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Sample records for hetero diels-alder reaction

  1. Solvent Effects in Asymmetric Hetero Diels-Alder and Ene Reactions

    DEFF Research Database (Denmark)

    Johannsen, Mogens; Jørgensen, Karl Anker

    1996-01-01

    The use of polar solvents such as nitromethane or 2-nitropropane leads to a significant improvement of the catalytic properties of a cationic copper-Lewis acid in the hetero Diels-Alder reaction of alkyl glyoxylates with dienes; The scope of a newly developed copper(II)-bisoxazoline catalyst...... for the hetero Diels-Alder reaction is demonstrated by the reaction of different dienes with alkyl glyoxylates in nitroalkane solvents with the formation of the hetero Diels-Alder adduct in high enantiomeric excess as the major product. The synthetic application of the reaction is exemplified by an improved...

  2. The first organocatalytic, ortho-regioselective inverse-electron-demand hetero-Diels-Alder reaction.

    Science.gov (United States)

    Hejmanowska, Joanna; Jasiński, Marcin; Wojciechowski, Jakub; Mlostoń, Grzegorz; Albrecht, Łukasz

    2017-10-17

    The development of the unprecedented ortho-regioselective inverse-electron-demand hetero-Diels-Alder (IEDHDA) reaction is described. It has been demonstrated that by proper choice of reactants and reaction conditions the inverse-electron-demand hetero-Diels-Alder cycloaddition can be realized with unprecedented regioselectivity arising from the reaction between the terminal carbon atom of the dienophile and the heteroatom of the heterodiene.

  3. The asymmetric hetero-Diels-Alder reaction in the syntheses of biologically relevant compounds.

    Science.gov (United States)

    Eschenbrenner-Lux, Vincent; Kumar, Kamal; Waldmann, Herbert

    2014-10-13

    The hetero-Diels-Alder reaction is one of the most powerful transformations in the chemistry toolbox for the synthesis of aza- and oxa-heterocycles embodying multiple stereogenic centers. However, as compared to other cycloadditions, in particular the dipolar cycloadditions and the Diels-Alder reaction, the hetero-Diels-Alder reaction has been much less explored and exploited in organic synthesis. Nevertheless, this powerful transformation has opened up efficient and creative routes to biologically relevant small molecules and different natural products which contain six-membered oxygen or nitrogen ring systems. Recent developments in this field, in particular in the establishment of enantioselectively catalyzed hetero-Diels-Alder cycloadditions steered by a plethora of different catalysts and the application of the resulting small molecules in chemical biology and medicinal chemistry research, are highlighted in this Minireview. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Catalytic Asymmetric Total Synthesis of (+)- and (-)-Paeoveitol via a Hetero-Diels-Alder Reaction.

    Science.gov (United States)

    Li, Tian-Ze; Geng, Chang-An; Yin, Xiu-Juan; Yang, Tong-Hua; Chen, Xing-Long; Huang, Xiao-Yan; Ma, Yun-Bao; Zhang, Xue-Mei; Chen, Ji-Jun

    2017-02-03

    The first catalytic asymmetric total synthesis of (+)- and (-)-paeoveitol has been accomplished in 42% overall yield via a biomimetic hetero-Diels-Alder reaction. The chiral phosphoric acid catalyzed hetero-Diels-Alder reaction showed excellent diastereo- and enantioselectivity (>99:1 dr and 90% ee); two rings and three stereocenters were constructed in a single step to produce (-)-paeoveitol on a scale of 452 mg. This strategy enabled us to selectively synthesize both paeoveitol enantiomers from the same substrates by simply changing the enantiomer of the catalyst.

  5. Metal-catalyzed Asymmetric Hetero-Diels-Alder Reactions of Unactivated Dienes with Glyoxylates

    DEFF Research Database (Denmark)

    Johannsen, Mogens; Yao, Sulan; Graven, Anette

    1998-01-01

    The development of a catalytic asymmetric hetero-Diels-Alder methodology for the reaction of unactivated dienes with glyoxylates is presented. Several different asymmetric catalysts can be used, but copper-bisoxazolines and aluminium-BINOL give the highest yield, and the best chemo...

  6. Total Synthesis of (+)-Cytosporolide A via a Biomimetic Hetero-Diels-Alder Reaction.

    Science.gov (United States)

    Takao, Ken-Ichi; Noguchi, Shuji; Sakamoto, Shu; Kimura, Mizuki; Yoshida, Keisuke; Tadano, Kin-Ichi

    2015-12-23

    The first total synthesis of (+)-cytosporolide A was achieved by a biomimetic hetero-Diels-Alder reaction of (-)-fuscoatrol A with o-quinone methide generated from (+)-CJ-12,373. The dienophile, highly oxygenated caryophyllene sesquiterpenoid (-)-fuscoatrol A, was synthesized from the synthetic intermediate in our previous total synthesis of (+)-pestalotiopsin A. The o-quinone methide precursor, isochroman carboxylic acid (+)-CJ-12,373, was synthesized through a Kolbe-Schmitt reaction and an oxa-Pictet-Spengler reaction. The hetero-Diels-Alder reaction of these two compounds proceeded with complete chemo-, regio-, and stereoselectivity to produce the complicated pentacyclic ring system of the cytosporolide skeleton. This total synthesis unambiguously demonstrates that natural cytosporolide A has the structure previously suggested.

  7. Stereo- and regioselectivity of the hetero-Diels-Alder reaction of nitroso derivatives with conjugated dienes.

    Science.gov (United States)

    Brulíková, Lucie; Harrison, Aidan; Miller, Marvin J; Hlaváč, Jan

    2016-01-01

    The hetero-Diels-Alder reaction between a nitroso dienophile and a conjugated diene to give the 3,6-dihydro-2 H -1,2-oxazine scaffold is useful for the synthesis of many biologically interesting molecules due to the diverse opportunities created by subsequent transformations of the resulting 1,2-oxazine ring. This review discusses the rationale for the observed regio- and stereoselectivity and the methods developed in recent years used to control and improve the stereo- and regioselectivity for the synthesis of 1,2-oxazine scaffolds.

  8. A Tunable and Enantioselective Hetero-Diels-Alder Reaction Provides Access to Distinct Piperidinoyl Spirooxindoles.

    Science.gov (United States)

    Jayakumar, Samydurai; Louven, Kathrin; Strohmann, Carsten; Kumar, Kamal

    2017-12-11

    The active complexes of chiral N,N'-dioxide ligands with dysprosium and magnesium salts catalyze the hetero-Diels-Alder reaction between 2-aza-3-silyloxy-butadienes and alkylidene oxindoles to selectively form 3,3'- and 3,4'-piperidinoyl spirooxindoles, respectively, in very high yields and with excellent enantioselectivities. The exo-selective asymmetric cycloaddition successfully regaled the construction of sp 3 -rich and highly substituted natural-product-based spirooxindoles supporting many chiral centers, including contiguous all-carbon quaternary centers. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Synthesis of 2,5-Disubstituted Octahydroquinolin-4-ones via anIntramolecular Hetero Diels-Alder Reaction

    Directory of Open Access Journals (Sweden)

    J. Antonio Palenzuela

    2007-02-01

    Full Text Available A route for the preparation of 2,5-disubstituted octahydroquinolin-4-ones, synthetic precursors of the decahydroquinoline-type toxins, is presented. The key steps are an asymmetric epoxidation and an intramolecular hetero Diels-Alder reaction between an activated diene and an imine. The presence of an allylic stereogenic center induces some selectivity and thus only two cycloadducts are obtained in 70:30 ratio and good yield.

  10. Tandem Reaction of Cationic Copolymerization and Concertedly Induced Hetero-Diels-Alder Reaction Preparing Sequence-Regulated Polymers.

    Science.gov (United States)

    Matsumoto, Suzuka; Kanazawa, Arihiro; Kanaoka, Shokyoku; Aoshima, Sadahito

    2017-06-14

    A unique tandem reaction of sequence-controlled cationic copolymerization and site-specific hetero-Diels-Alder (DA) reaction is demonstrated. In the controlled cationic copolymerization of furfural and 2-acetoxyethyl vinyl ether (AcOVE), only the furan ring adjacent to the propagating carbocation underwent the hetero-DA reaction with the aldehyde moiety of another furfural molecule. A further and equally important feature of the copolymerization is that the obtained copolymers had unprecedented 2:(1 + 1)-type alternating structures of repeating sequences of two VE and one furfural units in the main chain and one furfural unit in the side chain. The specific DA reaction is attributed to the delocalization of the positive charge to the side furan ring.

  11. Stereo-controlled synthesis of polyheterocycles via the diene-transmissive hetero-Diels-Alder reaction of β,γ-unsaturated α-keto esters.

    Science.gov (United States)

    Otani, Takashi; Tamai, Yumiko; Seki, Kazunori; Kikuchi, Tomohiro; Miyazawa, Taiichiro; Saito, Takao

    2015-06-07

    We describe the stereoselective synthesis of polyring-fused heterocyclic compounds based on diene-transmissive hetero-Diels-Alder reactions utilizing β,γ-unsaturated α-keto esters. This protocol involves the initial endo- or exo-selective Diels-Alder (DA) reactions with electron-rich dienophiles, methylenation of the ester carbonyl groups with the Tebbe reagent, and a stereoselective second DA reaction with electron-deficient dienophiles. The use of enantioselective DA reactions in the initial reaction enables access to chiral polyring-fused heterocyclic compounds with multiple chiral centres.

  12. The Synthesis of "N"-Benzyl-2-Azanorbornene via Aqueous Hetero Diels-Alder Reaction: An Undergraduate Project in Organic Synthesis and Structural Analysis

    Science.gov (United States)

    Sauvage, Xavier; Delaude, Lionel

    2008-01-01

    The synthesis of "N"-benzyl-2-azanorbornene via aqueous hetero Diels-Alder reaction of cyclopentadiene and benzyliminium chloride formed in situ from benzylamine hydrochloride and formaldehyde is described. Characterization of the product was achieved by IR and NMR spectroscopies. The spectral data acquired are thoroughly discussed. Numerous…

  13. Fast Hetero-Diels-Alder Reactions Using 4-Phenyl-1,2,4-Triazoline-3,5-Dione (PTAD) as the Dienophile

    Science.gov (United States)

    Celius, Tevye C.

    2010-01-01

    A hetero-Diels-Alder reaction that proceeds rapidly and only requires a simple filtration to purify the product is presented. The dienophile, 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD), is prepared by the heterogeneous oxidation of 4-phenylurazole by the bromenium ion, Br[superscript +], generated in situ by the oxidation of potassium bromide by…

  14. First catalytic hetero-Diels-Alder reaction of imidazole-2-thiones and in silico biological evaluation of the cycloadducts

    NARCIS (Netherlands)

    Eleftheriadis, Nikolaos; Samatidou, Evanthia; Neochoritis, Constantinos G.

    The Lewis acid-catalyzed Diels-Alder reactions of suitably substituted imidazole-2-thiones with dienes were studied. It was found that the electron density of the imidazole core influenced the reaction, since electron withdrawing groups led to the novel spiro-derivatives 2 whereas electron donating

  15. Intramolecular and Transannular Diels-Alder Reactions

    DEFF Research Database (Denmark)

    Tanner, David Ackland; Ascic, Erhad

    2014-01-01

    Few reactions can compete with the Diels-Alder (DA) [4+2] cycloaddition for the rapid and efficient generation of molecular complexity. The DA reaction is atom-economic and stereospecific, as well as diastereo- and regioselective. The intramolecular version (IMDA) of the DA cycloaddition and its...... and dienophile, methods for acceleration of IMDA reactions (such as use of high pressure) and catalysis (using oxophilic or carbophilic metal complexes, Brønsted acids, and enzymes). The use of furans as diene components (IMDAF), intramolecular hetero-DA (IMHDA) and IMDA reactions with inverse electron demand...... are also covered. Applications of IMDA to asymmetric synthesis (from substrate control through to enantioselective catalysis, including organocatalysis) are presented, along with tandem sequences involving IMDA cycloaddition. A theme pervading the whole chapter is the use of IMDA reactions for the total...

  16. Molecular Design of a Chiral Brønsted Acid with Two Different Acidic Sites: Regio-, Diastereo-, and Enantioselective Hetero-Diels-Alder Reaction of Azopyridinecarboxylate with Amidodienes Catalyzed by Chiral Carboxylic Acid-Monophosphoric Acid.

    Science.gov (United States)

    Momiyama, Norie; Tabuse, Hideaki; Noda, Hirofumi; Yamanaka, Masahiro; Fujinami, Takeshi; Yamanishi, Katsunori; Izumiseki, Atsuto; Funayama, Kosuke; Egawa, Fuyuki; Okada, Shino; Adachi, Hiroaki; Terada, Masahiro

    2016-09-07

    A chiral Brønsted acid containing two different acidic sites, chiral carboxylic acid-monophosphoric acid 1a, was designed to be a new and effective concept in catalytic asymmetric hetero-Diels-Alder reactions of azopyridinecarboxylate with amidodienes. The multipoint hydrogen-bonding interactions among the carboxylic acid, monophosphoric acid, azopyridinecarboxylate, and amidodiene achieved high catalytic and chiral efficiency, producing substituted 1,2,3,6-tetrahydropyridazines with excellent stereocontrol in a single step. This constitutes the first example of regio-, diastereo-, and enantioselective azo-hetero-Diels-Alder reactions by chiral Brønsted acid catalysis.

  17. Synthesis of 3-Alkenyl-1-azaanthraquinones via Diels-Alder and Electron Transfer Reactions

    Directory of Open Access Journals (Sweden)

    Patrice Vanelle

    2002-12-01

    Full Text Available A convenient route to 3-alkenyl-1-azaanthraquinones via a hetero Diels-Alder reaction between an azadiene and naphthoquinone, a free radical chlorination and an electron transfer reaction is reported.

  18. The pentadehydro-Diels-Alder reaction.

    Science.gov (United States)

    Wang, Teng; Naredla, Rajasekhar Reddy; Thompson, Severin K; Hoye, Thomas R

    2016-04-28

    In the classic Diels-Alder [4 + 2] cycloaddition reaction, the overall degree of unsaturation (or oxidation state) of the 4π (diene) and 2π (dienophile) pairs of reactants dictates the oxidation state of the newly formed six-membered carbocycle. For example, in the classic Diels-Alder reaction, butadiene and ethylene combine to produce cyclohexene. More recent developments include variants in which the number of hydrogen atoms in the reactant pair and in the resulting product is reduced by, for example, four in the tetradehydro-Diels-Alder (TDDA) and by six in the hexadehydro-Diels-Alder (HDDA) reactions. Any oxidation state higher than tetradehydro (that is, lacking more than four hydrogens) leads to the production of a reactive intermediate that is more highly oxidized than benzene. This increases the power of the overall process substantially, because trapping of the reactive intermediate can be used to increase the structural complexity of the final product in a controllable and versatile manner. Here we report an unprecedented overall 4π + 2π cycloaddition reaction that generates a different, highly reactive intermediate known as an α,3-dehydrotoluene. This species is in the same oxidation state as a benzyne. Like benzynes, α,3-dehydrotoluenes can be captured by various trapping agents to produce structurally diverse products that are complementary to those arising from the HDDA process. We call this new cycloisomerization process a pentadehydro-Diels-Alder (PDDA) reaction-a nomenclature chosen for chemical taxonomic reasons rather than mechanistic ones. In addition to alkynes, nitriles (RC≡N), although non-participants in aza-HDDA reactions, readily function as the 2π component in PDDA cyclizations to produce, via trapping of the α,3-(5-aza)dehydrotoluene intermediates, pyridine-containing products.

  19. N,N'-dioxide/nickel(II)-catalyzed asymmetric inverse-electron-demand hetero-diels-alder reaction of β,γ-unsaturated α-ketoesters with enecarbamates.

    Science.gov (United States)

    Zhou, Yuhang; Zhu, Yin; Lin, Lili; Zhang, Yulong; Zheng, Jianfeng; Liu, Xiaohua; Feng, Xiaoming

    2014-12-08

    N,N'-Dioxide/nickel(II) complexes have been developed to catalyze the inverse-electron-demand hetero-Diels-Alder reaction of β,γ-unsaturated α-ketoesters with acyclic enecarbamates. After detailed screening of the reaction parameters, mild optimized reaction conditions were established, affording 3,4-dihydro-2H-pyranamines in up to 99 % yield, 99 % ee and more than 95:5 d.r. The catalytic system was also efficient for β-substituted acyclic enecarbamates, affording more challenging 2,3,4-trisubstituted 3,4-dihydro-2H-pyranamine with three contiguous stereogenic centers in excellent yields, diastereoselectivities, and enantioselectivities. The reaction could be scaled up to a gram scale with no deterioration of either enantioselectivity or yield. Based on these experiments and on previous reports, a possible transition state was proposed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. The hexadehydro-Diels-Alder reaction.

    Science.gov (United States)

    Hoye, Thomas R; Baire, Beeraiah; Niu, Dawen; Willoughby, Patrick H; Woods, Brian P

    2012-10-11

    Arynes (aromatic systems containing, formally, a carbon-carbon triple bond) are among the most versatile of all reactive intermediates in organic chemistry. They can be 'trapped' to give products that are used as pharmaceuticals, agrochemicals, dyes, polymers and other fine chemicals. Here we explore a strategy that unites the de novo generation of benzynes-through a hexadehydro-Diels-Alder reaction-with their in situ elaboration into structurally complex benzenoid products. In the hexadehydro-Diels-Alder reaction, a 1,3-diyne is engaged in a [4+2] cycloisomerization with a 'diynophile' to produce the highly reactive benzyne intermediate. The reaction conditions for this simple, thermal transformation are notable for being free of metals and reagents. The subsequent and highly efficient trapping reactions increase the power of the overall process. Finally, we provide examples of how this de novo benzyne generation approach allows new modes of intrinsic reactivity to be revealed.

  1. Stepwise radical cation Diels-Alder reaction via multiple pathways.

    Science.gov (United States)

    Shimizu, Ryo; Okada, Yohei; Chiba, Kazuhiro

    2018-01-01

    Herein we disclose the radical cation Diels-Alder reaction of aryl vinyl ethers by electrocatalysis, which is triggered by an oxidative SET process. The reaction clearly proceeds in a stepwise fashion, which is a rare mechanism in this class. We also found that two distinctive pathways, including "direct" and "indirect", are possible to construct the Diels-Alder adduct.

  2. A hetero retro Diels-Alder reaction in aqueous solution : A dramatic water-induced increase of the equilibrium constant and inhibition of cycloreversion

    NARCIS (Netherlands)

    Wijnen, J.W; Engberts, J.B.F.N.

    The adduct of the Diels-Alder reaction of nitrosobenzene with cyclopentadiene is not stable in solution. The equilibrium constant for the reaction depends strongly on the medium and water induces a spectacular shift to the adduct. Comparison with the bimolecular addition of nitrosobenzene to

  3. Dehydrogenative Diels-Alder reaction.

    Science.gov (United States)

    Ozawa, Takuya; Kurahashi, Takuya; Matsubara, Seijiro

    2011-10-07

    The dehydrogenative cycloaddition of dieneynes, which possess a diene in the form of a styrene moiety and a dienophile in the form of an alkyne moiety, produces naphthalene derivatives when heated. It was found that a key requirement of this process is the presence of a silyl group attached to the alkyne moiety, which forces a dehydrogenation reaction to occur. © 2011 American Chemical Society

  4. Mechanisms of the Knoevenagel hetero Diels-Alder sequence in multicomponent reactions to dihydropyrans: experimental and theoretical investigations into the role of water.

    Science.gov (United States)

    Frapper, Gilles; Bachmann, Christian; Gu, Yanlong; Coval De Sousa, Rodolphe; Jérôme, François

    2011-01-14

    The role of water in a multicomponent domino reaction (MCR) involving styrene, 2,4-pentanedione, and formaldehyde was studied. Whereas anhydrous conditions produced no reaction, the MCR successfully proceeded in the presence of water, affording the targeted dihydropyran derivatives with good yield. The mechanism of this MCR (Knoevenagel hetero Diels-Alder sequence) was studied with and without explicit water molecules using the SMD continuum solvation model in combination with the B3LYP density functional and the 6-311++G** basis set to compute the water and acetone (aprotic organic solvent) solution Gibbs free energies. In the Knoevenagel step, we found that water acted as a proton relay to favor the formation of more flexible six-membered ring transition state structures both in concerted (direct H(2)O elimination) and stepwise (keto-enol tautomerization and dehydration) pathways. The inclusion of a water molecule in our model resulted in a significant decrease (-8.5 kcal mol(-1)ΔG(water)(‡)) of the direct water elimination activation barrier. Owing to the presence of water, all chemical steps involved in the MCR mechanism had activation free energies barriers lower than 39 kcal mol(-1) at 25 °C in aqueous solvent (ZPE corrected electronic energies barriers). Consequently, the MCR proceeded without the assistance of any catalyst.

  5. The [2 + 2] Cycloaddition-Retroelectrocyclization and [4 + 2] Hetero-Diels-Alder Reactions of 2-(Dicyanomethylene)indan-1,3-dione with Electron-Rich Alkynes: Influence of Lewis Acids on Reactivity.

    Science.gov (United States)

    Donckele, Etienne J; Finke, Aaron D; Ruhlmann, Laurent; Boudon, Corinne; Trapp, Nils; Diederich, François

    2015-07-17

    The reaction of electrophilic 2-(dicyanomethylene)indan-1,3-dione (DCID) with substituted, electron-rich alkynes provides two classes of push-pull chromophores with interesting optoelectronic properties. The formal [2 + 2] cycloaddition-retroelectrocyclization reaction at the exocyclic double bond of DCID gives cyanobuta-1,3-dienes, and the formal [4 + 2] hetero-Diels-Alder (HDA) reaction at an enone moiety of DCID generates fused 4H-pyran heterocycles. Both products can be obtained in good yield and excellent selectivity by carefully tuning the reaction conditions; in particular, the use of Lewis acids dramatically enhances formation of the HDA adduct.

  6. Theoretical study of the Diels-Alder reaction between o-benzoquinone and norbornadiene

    Science.gov (United States)

    Quijano-Quiñones, Ramiro F.; Quesadas-Rojas, M.; Cuevas, Gabriel; Mena-Rejón, Gonzalo J.

    2013-06-01

    The reaction between norbornadiene and o-benzoquinone is an important step in polyalicyclic rigid structures synthesis. It has been considered that this reaction is an example of Diels-Alder (DA) and hetero-Diels-Alder (HDA) cycloadditions with o-benzoquinone acting as diene (forming C-C bonds) and heterodiene (forming O-C bonds). We have performed a Density Functional Theory study of this reaction, employing B3LYP, mPW1PW91, and B1B95 functionals and 6-31G(d,p) and 6-31+G(d,p) Gaussian type basis sets. The results indicate that Diels-Alder is a feasible mechanism for both reactions, but should not be the main route to the formation of products with C-C bonds.

  7. Theoretical study of the Diels-Alder reaction between o-benzoquinone and norbornadiene

    International Nuclear Information System (INIS)

    Quijano-Quiñones, Ramiro F; Quesadas-Rojas, M; Mena-Rejón, Gonzalo J; Cuevas, Gabriel

    2013-01-01

    The reaction between norbornadiene and o-benzoquinone is an important step in polyalicyclic rigid structures synthesis. It has been considered that this reaction is an example of Diels-Alder (DA) and hetero-Diels-Alder (HDA) cycloadditions with o-benzoquinone acting as diene (forming C-C bonds) and heterodiene (forming O-C bonds). We have performed a Density Functional Theory study of this reaction, employing B3LYP, mPW1PW91, and B1B95 functionals and 6-31G(d,p) and 6-31+G(d,p) Gaussian type basis sets. The results indicate that Diels-Alder is a feasible mechanism for both reactions, but should not be the main route to the formation of products with C-C bonds.

  8. Domino Aza-Michael-ih-Diels-Alder Reaction to Various 3-Vinyl-1,2,4-triazines: Access to Polysubstituted Tetrahydro-1,6-naphthyridines.

    Science.gov (United States)

    Jouha, Jabrane; Buttard, Floris; Lorion, Magali; Berthonneau, Clément; Khouili, Mostafa; Hiebel, Marie-Aude; Guillaumet, Gérald; Brière, Jean-François; Suzenet, Franck

    2017-09-15

    A straightforward domino aza-Michael-inverse-electron-demand-hetero-Diels-Alder/retro-Diels-Alder reaction between primary and secondary propargylamine derivatives and 3-vinyl-1,2,4-triazines is developed highlighting not only the uniqueness of this dual-heterocyclic platform but also a novel and unprecedented path to polysubstituted tetrahydro-1,6-naphthyridine scaffolds.

  9. Fourfold Diels-Alder reaction of tetraethynylsilane.

    Science.gov (United States)

    Geyer, Florian L; Rode, Alexander; Bunz, Uwe H F

    2014-12-08

    A series of ethynylated silanes, including tetraethynylsilane, was treated with tetraphenylcyclopentadienone at 300 °C under microwave irradiation to give the aromatized Diels-Alder adducts as sterically encumbered mini-dendrimers with up to 20 benzene rings. The sterically most congested adducts display red-shifted emission through intramolecular π-π interactions in the excited state. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Intramolecular inverse electron demand Diels-Alder reactions of pyrimidines

    NARCIS (Netherlands)

    Frissen, A.E.

    1990-01-01

    This thesis deals with the intramolecular inverse electron demand Diels-Alder reaction of pyrimidines. The main objective of the study was to investigate the synthetic applicability of this reaction and to get more insight in the electronic and steric effects which determine the reactivity

  11. High stereoselectivity on low temperature Diels-Alder reactions

    Directory of Open Access Journals (Sweden)

    Invernize Paulo

    2005-12-01

    Full Text Available Abstract We have found that some of the usually poor dienophiles (2-cycloenones can undergo Diels-Alder reaction at -78°C with unusually high stereoselectivity in the presence of niobium pentachloride as a Lewis acid catalyst. A remarkable difference in reaction rates for unsubstituted and α- or β-methyl substituted 2-cycloenones was also observed.

  12. Reaction of Aldehydes/Ketones with Electron-Deficient 1,3,5-Triazines Leading to Functionalized Pyrimidines as Diels-Alder/Retro-Diels-Alder Reaction Products: Reaction Development and Mechanistic Studies.

    Science.gov (United States)

    Yang, Kai; Dang, Qun; Cai, Pei-Jun; Gao, Yang; Yu, Zhi-Xiang; Bai, Xu

    2017-03-03

    Catalytic inverse electron demand Diels-Alder (IEDDA) reactions of heterocyclic aza-dienes are rarely reported since highly reactive and electron-rich dienophiles are often found not compatible with strong acids such as Lewis acids. Herein, we disclose that TFA-catalyzed reactions of electron-deficient 1,3,5-triazines and electron-deficient aldehydes/ketones can take place. These reactions led to highly functionalized pyrimidines as products in fair to good yields. The reaction mechanism was carefully studied by the combination of experimental and computational studies. The reactions involve a cascade of stepwise inverse electron demand hetero-Diels-Alder (ihDA) reactions, followed by retro-Diels-Alder (rDA) reactions and elimination of water. An acid was required for both ihDA and rDA reactions. This mechanism was further verified by comparing the relative reactivity of aldehydes/ketones and their corresponding vinyl ethers in the current reaction system.

  13. Intramolecular Diels-Alder Reactions in Organic Synthesis

    OpenAIRE

    Sizemore, Nicholas Blandford Luke

    2014-01-01

    Intramolecular Diels-Alder (IMDA) reactions are an important class of reactions in synthetic organic chemistry for the rapid construction of polycyclic frameworks. Three classes of IMDA reactions were investigated synthetically and computationally: 1) all-carbon type 1 IMDA reactions, 2) N-acylnitroso type 2 IMDA reactions, and 3) cyano-azadiene IMDA reactions. The first class was implemented in research toward the total synthesis of maoecrystal Z and isopalhinine A. The second class was stud...

  14. Application of the aza-Diels-Alder reaction in the synthesis of natural products.

    Science.gov (United States)

    Cao, Min-Hui; Green, Nicholas J; Xu, Sheng-Zhen

    2017-04-11

    The Diels-Alder reaction that involves a nitrogen atom in the diene or dienophile is termed the aza-Diels-Alder reaction. As well as the powerful all-carbon Diels-Alder reaction, the aza-Diels-Alder reaction has also played an important role in the total synthesis of natural products. Herein, we review various natural products using an aza-Diels-Alder reaction as a key step to their total synthesis, and divide the syntheses into inter- and intra-molecular aza-Diels-Alder reactions and a retro-aza-Diels-Alder reaction. Inter- and intra-molecular aza-Diels-Alder reactions involve an imine as an electron deficient dienophile and an imine as an electron deficient azadiene. The significance of the aza-Diels-Alder reaction for the construction of a six-membered ring containing nitrogen is tremendous, but the development of asymmetric, in particular catalytic enantioselective intramolecular aza-Diels-Alder reaction in the total synthesis of natural products remains highly challenging, and will no doubt see enormous advances in the future.

  15. Polar Diels-Alder reactions using electrophilic nitrobenzothiophenes. A combined experimental and DFT study

    Science.gov (United States)

    Della Rosa, Claudia D.; Mancini, Pedro M. E.; Kneeteman, Maria N.; Lopez Baena, Anna F.; Suligoy, Melisa A.; Domingo, Luis R.

    2015-01-01

    The reactions between 2- and 3-nitrobenzothiophenes with three dienes of different nucleophilicity, 1-methoxy-3-trimethylsilyloxy-1,3-butadiene, 1-trimethylsilyloxy-1,3-butadiene and isoprene developed in anhydrous benzene and alternative under microwave irradiation with molecular solvents or in free solvent conditions, respectively, for produce dibenzothiophenes permit to conclude that both nitroheterocycles act as electrophile with the cited dienes. In the cases of the dienes 1-methoxy-3-trimethylsilyloxy-1,3-butadiene and 1-trimethylsilyloxy-1,3-butadiene which posses major nucleophilicity the observed product is the normal cycloaddition one. However when the diene is isoprene the product with both electrophiles follow the hetero Diels-Alder way. These reactions are considered polar cycloaddition reactions and the yields are reasonables. Moreover the polar Diels-Alder reactions of nitrobenzothiophenes with electron rich dienes 1-trimethylsilyloxy-1,3-butadiene have been theoretically studied using DFT methods.

  16. Diels-Alder reactions of anthracenes with C-sulfonyldithioformates

    DEFF Research Database (Denmark)

    El-Sayed, I.; Ali, O.M.; Fischer, A.

    2003-01-01

    C-Sulfonyldithioformates (2) (R-1 = ArSO2, R 2 = ArS) readily add to anthracene and 9-methylanthracene (1) in a Diels-Alder fashion with formation of 9,10-dihydro-10,9-(epithiomethano)anthracenes (3) which in turn may suffer thermally induced elimination of arenesulfinic acid to yield the 9......-anthracenedithiocarboxylic esters (4). The reactions with the unsymmetrical diene 9-methylanthracene take place in a highly stereoselective fashion....

  17. Synthesis of α- and β-lapachone derivatives from hetero diels-alder trapping of alkyl and aryl o-quinone methides

    International Nuclear Information System (INIS)

    Silva, Fernando de C. da; Ferreira, Sabrina B.; Ferreira, Vitor F.; Kaiser, Carlos R.; Pinto, Angelo C.

    2009-01-01

    Methylene and aryl o-quinone methides (o-QMs) generated by Knoevenagel condensation of 2-hydroxy-1,4-naphthoquinone with formaldehyde and arylaldehydes, undergo facile hetero Diels-Alder reaction with some substituted styrenes (as dienophiles) in aqueous ethanol media providing derivatives of α- and β-lapachone (author)

  18. Intramolecular Diels-Alder reactions of pyrimidines, a synthetic and computational study

    NARCIS (Netherlands)

    Stolle, W.A.W.

    1992-01-01

    This thesis deals with an investigation on the ringtransformation reactions of 2and 5-(ω-alkynyl)pyrimidine derivatives, which undergo upon heating an intramolecular Diels-Alder reaction and subsequently a spontaneous retro Diels- Alder reaction. To get a better insight into the

  19. Substituent effects on an inverse electron demand hetero Diels-Alder reaction in aqueous solution and organic solvents : Cycloaddition of substituted styrenes to di(2-pyridyl)-1,2,4,5-tetrazine

    NARCIS (Netherlands)

    Wijnen, Jan W.; Zavarise, Silvia; Engberts, Jan B.F.N.; Charton, Marvin

    1996-01-01

    The kinetics of the Diels-Alder reactions of di(2-pyridyl)-1,2,4,5-tetrazine (1) with substituted styrenes 2 was investigated in aqueous media and in organic solvents. The second-order rate constants ofthis reaction increase dramatically in water-rich media. A decrease in pH accelerates the aqueous

  20. Diels-Alder reactions onto fluorinated and hydrogenated graphene

    Science.gov (United States)

    Denis, Pablo A.

    2017-09-01

    We studied Diels-Alder (DA) reactions onto functionalized graphene. When fluorine, hydrogen or oxygen functional groups are present on one side of the sheet, the DA cycloadditions become significantly more exergonic when performed on the opposite side. Hydrogen is more effective than fluorine and oxygen to promote these cycloadditions. In contrast with the results obtained for perfect graphene, the functionalization with H, F or O turns the DA reactions exergonic, with ΔG°298 = -127.2 kcal/mol. The reaction barriers are expected to be considerably lowered with respect to perfect graphene because the functional groups significantly reduce the distortion energy.

  1. Is it true that polymerization of vegetable oil occurs through Diels-Alder reaction?

    Science.gov (United States)

    Diels-Alder reaction mechanism is known to be one of the major reaction mechanisms to produce dimers and polymers during heating process of vegetable oil. However, our NMR study showed no evidence for Diels-Alder products. Soybean oil oxidized at 180 °C for 24 hrs with 1.45 surface area-to-volume ...

  2. Asymmetric Diels-Alder reactions with 5-menthyloxy-2(5H)-furanones

    NARCIS (Netherlands)

    Jong, Johannes Cornelis de

    2006-01-01

    At the beginning of the reseach described in this thesis the catalytic asymmetric Diels-Alder reaction had scarcely been investigated. No good catalytic processes with high enantiomeric excess were known at that time. At the same time the Diels-Alder reactions with chiral dienophiles needed further

  3. DIELS-ALDER REACTIONS IN AQUEOUS-SOLUTIONS - ENFORCED HYDROPHOBIC INTERACTIONS BETWEEN DIENE AND DIENOPHILE

    NARCIS (Netherlands)

    BLOKZIJL, W; BLANDAMER, MJ; ENGBERTS, JBFN

    1991-01-01

    Second-order rate constants and isobaric activation parameters for the intermolecular Diels-Alder reactions of cyclopentadiene with alkyl vinyl ketones (2a,b) and 5-substituted-1,4-naphthoquinones (3a-c) as well as for the intramolecular Diels-Alder reaction of N-furfuryl-N-methylmaleamic acid (4)

  4. Synthesis of novel chromeno-annulated cis-fused pyrano[3,4-c]benzopyran and naphtho pyran derivatives via domino aldol-type/hetero Diels-Alder reaction and their cytotoxicity evaluation.

    Science.gov (United States)

    Madda, Jyothi; Venkatesham, Akkaladevi; Naveen Kumar, Bejjanki; Nagaiah, Kommu; Sujitha, Pombala; Ganesh Kumar, C; Rao, Tadikamalla Prabhakar; Jagadeesh Babu, Nanubolu

    2014-09-15

    New chromeno-annulated cis-fused pyrano[3,4-c]benzopyran and naphtho pyran derivatives have been synthesized by domino aldol-type reaction/hetero Diels-Alder reaction generated from o-quinone methide in situ from 7-O-prenyl derivatives of 8-formyl-2,3-disubstituted chromenones with resorcinols/naphthols in the presence of 20 mol% ethylenediamine diacetate (EDDA), triethylamine (2 mL) as co-catalyst in CH3CN under reflux conditions in good yields. The structures were established based on spectroscopic data, and further confirmed by X-ray diffraction analysis. The results showed that compounds 4h and 4j exhibited very potent cytotoxicity against human cervical cancer cell line (HeLa). Compound 4h displayed good inhibitory activity against both breast cancer cell lines, MDA-MB-231 and MCF-7. Further, the compound 4i exhibited good cytotoxicity against only MDA-MB-231, and compound 4j showed promising activity against human lung cancer cell line, A549 with IC50 value of 2.53±0.07 μM, which was comparable to the standard doxorubicin (IC50=1.21±0.1 μM). Copyright © 2014 Elsevier Ltd. All rights reserved.

  5. Mild and modular surface modification of cellulose via hetero Diels-Alder (HDA) cycloaddition.

    Science.gov (United States)

    Goldmann, Anja S; Tischer, Thomas; Barner, Leonie; Bruns, Michael; Barner-Kowollik, Christopher

    2011-04-11

    A combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and hetero Diels-Alder (HDA) cycloaddition was used to effect, under mild (T ≈ 20 °C), fast, and modular conditions, the grafting of poly(isobornyl acrylate) (M(n) = 9800 g mol(-1), PDI = 1.19) onto a solid cellulose substrate. The active hydroxyl groups expressed on the cellulose fibers were converted to tosylate leaving groups, which were subsequently substituted by a highly reactive cyclopentadienyl functionality (Cp). By employing the reactive Cp-functionality as a diene, thiocarbonyl thio-capped poly(isobornyl acrylate) synthesized via RAFT polymerization (mediated by benzyl pyridine-2-yldithioformiate (BPDF)) was attached to the surface under ambient conditions by an HDA cycloaddition (reaction time: 15 h). The surface-modified cellulose samples were analyzed in-depth by X-ray photoelectron spectroscopy, scanning electron microscopy, elemental analysis, Fourier transform infrared (FT-IR) spectroscopy as well as Fourier transform infrared microscopy employing a focal plane array detector for imaging purposes. The analytical results provide strong evidence that the reaction of suitable dienophiles with Cp-functional cellulose proceeds under mild reaction conditions (T ≈ 20 °C) in an efficient fashion. In particular, the visualization of individual modified cellulose fibers via high-resolution FT-IR microscopy corroborates the homogeneous distribution of the polymer film on the cellulose fibers.

  6. Fe(II)/Fe(III)-Catalyzed Intramolecular Didehydro-Diels-Alder Reaction of Styrene-ynes.

    Science.gov (United States)

    Mun, Hyeon Jin; Seong, Eun Young; Ahn, Kwang-Hyun; Kang, Eun Joo

    2018-02-02

    The intramolecular didehydro-Diels-Alder reaction of styrene-ynes was catalyzed by Fe(II) and Fe(III) to produce various naphthalene derivatives under microwave heating conditions. Mechanistic calculations found that the Fe(II) catalyst activates the styrenyl diene in an inverse-electron-demand Diels-Alder reaction, and the consecutive dehydrogenation reaction can be promoted by either Fe(II)-catalyzed direct dehydrogenation or an Fe(III)-catalyzed rearomatization/dehydrogenation pathway.

  7. Reaction energetics on long-range corrected density functional theory: Diels-Alder reactions.

    Science.gov (United States)

    Singh, Raman K; Tsuneda, Takao

    2013-02-15

    The possibility of quantitative reaction analysis on the orbital energies of long-range corrected density functional theory (LC-DFT) is presented. First, we calculated the Diels-Alder reaction enthalpies that have been poorly given by conventional functionals including B3LYP functional. As a result, it is found that the long-range correction drastically improves the reaction enthalpies. The barrier height energies were also computed for these reactions. Consequently, we found that dispersion correlation correction is also crucial to give accurate barrier height energies. It is, therefore, concluded that both long-range exchange interactions and dispersion correlations are essentially required in conventional functionals to investigate Diels-Alder reactions quantitatively. After confirming that LC-DFT accurately reproduces the orbital energies of the reactant and product molecules of the Diels-Alder reactions, the global hardness responses, the halves of highest occupied molecular orbital (HOMO)-lowest unoccupied molecular orbital (LUMO) energy gaps, along the intrinsic reaction coordinates of two Diels-Alder reactions were computed. We noticed that LC-DFT results satisfy the maximum hardness rule for overall reaction paths while conventional functionals violate this rule on the reaction pathways. Furthermore, our results also show that the HOMO-LUMO gap variations are close to the reaction enthalpies for these Diels-Alder reactions. Based on these results, we foresee quantitative reaction analysis on the orbital energies. Copyright © 2012 Wiley Periodicals, Inc.

  8. Domino Wittig Diels-Alder reaction: An expeditious entry into the AB ring system of furanosesquiterpenes

    Digital Repository Service at National Institute of Oceanography (India)

    Patre, R.E.; Gawas, S.; Sen, S.; Parameswaran, P.S.; Tilve, S.G.

    A domino Wittig Diels - Alder reaction has been employed in delineating a short and flexible synthetic stratagem for ready access to the AB ring system and the tricyclic framework of furanosesquiterpenes, such as the bioactive natural products...

  9. Diels-Alder reactions in confined spaces: the influence of catalyst structure and the nature of active sites for the retro-Diels-Alder reaction.

    Science.gov (United States)

    Cantín, Ángel; Gomez, M Victoria; de la Hoz, Antonio

    2016-01-01

    Diels-Alder cycloaddition between cyclopentadiene and p -benzoquinone has been studied in the confined space of a pure silica zeolite Beta and the impact on reaction rate due to the concentration effect within the pore and diffusion limitations are discussed. Introduction of Lewis or Brønsted acid sites on the walls of the zeolite strongly increases the reaction rate. However, contrary to what occurs with mesoporous molecular sieves (MCM-41), Beta zeolite does not catalyse the retro-Diels-Alder reaction, resulting in a highly selective catalyst for the cycloaddition reaction.

  10. High-level Computational Study of the Site-, Facial- and Stereoselectivities for the Diels-Alder Reaction Between o-Benzoquinone and Norbornadiene

    Directory of Open Access Journals (Sweden)

    Ronald N. Warrener

    2000-12-01

    Full Text Available Ab initio and DFT quantum chemical calculations have been applied to a study of the Diels-Alder reaction of o-benzoquinone as diene and norbornadiene as dienophile. Transition states for the different reactions are located and activation energies estimated. The prefered exo-π-facial selectivity and exo,endo-stereoselectivity exhibited in this cycloaddition are readily predicted using RHF/3-21G or higher levels of calculations. Differences between experimentally observed results and calculations may be explained by the postulation of a second, nonconcerted biradical mechanism leading to formation of hetero Diels-Alder products.

  11. Diels-Alder reactions: The effects of catalyst on the addition reaction

    Science.gov (United States)

    Yilmaz, Özgür; Kus, Nermin Simsek; Tunç, Tuncay; Sahin, Ertan

    2015-10-01

    The reaction between 2,3-dimethyl-1,3-butadiene and dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate is efficiently achieved with small amounts of catalyst, i.e. phenol, AcOH, nafion, and β-cyclodextrin. Exo-diastereoselective cycloaddition reactions were observed both without catalyst and different catalysts for 48 days. As a result, different products (tricyclicmolecule 5, retro-Diels-Alder product 6, and oxidation product 7) were obtained with different catalysts. In addition, we synthesized Diels-Alders product 8 and tricyclocyclitol 10 via Diels-Alder reaction. The structures of these products were characterized by 1H NMR, 13C NMR, MS and IR spectroscopy.

  12. Computational and Experimental Studies on the Hetero-Diels-Alder ...

    African Journals Online (AJOL)

    NJD

    Additionally, experimental studies carried out on the reactions of these enaminones 1 with sulphene were also found to be in ... reactions of simple enaminoketones with some dienophiles have been ... example, the only reported [4+2] cycloaddition reaction of .... (2a–c, 3a–c) are true ground state minima, verified by second.

  13. Computational and Experimental Studies on the Hetero-Diels-Alder ...

    African Journals Online (AJOL)

    Ab initio and density functional theory (DFT) calculations have been used to investigate the feasibility of cycloaddition reactions of enaminones 1 with sulphene. Specifically, the geometry optimizations, frequency calculations and self-consistent reactionfield (SCRF) solvent simulations in combination with higher-quality ...

  14. Diels-Alder reactions of inert aromatic compounds within a self-assembled coordination cage.

    Science.gov (United States)

    Horiuchi, Shinnosuke; Murase, Takashi; Fujita, Makoto

    2011-07-04

    A self-assembled coordination cage serves as a nanometer-sized molecular flask to promote the Diels-Alder reactions of aromatic hydrocarbons with N-cyclohexylmaleimide. The coordination cage accelerated the Diels-Alder reaction of anthracene at the electronically unfavorable, terminal benzene ring to give a compact, cavity-restrained syn-adduct. Activation-parameter measurements for the reactions revealed considerable reduction in the entropy cost, and preorganization of the substrates is a dominant factor in the enhanced reactivity. Owing to this entropy-cost reduction, otherwise-unreactive aromatic compounds, such as naphthalenes or triphenylene, also underwent Diels-Alder reactions in a regio- and stereocontrolled fashion. In the naphthalene Diels-Alder reaction, X-ray crystallographic analysis of the guest-inclusion complex clarified the reinforced orientation and proximity of the substrate pairs before the reaction. A perylene Diels-Alder adduct was stabilized inside the cage and protected from aerial oxidation. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Asymmetric aza-Diels-Alder reaction of Danishefsky's diene with imines in a chiral reaction medium

    Directory of Open Access Journals (Sweden)

    Pégot Bruce

    2006-09-01

    Full Text Available Abstract The asymmetric aza-Diels-Alder reaction of chiral imines with Danishefsky's diene in chiral ionic liquids provides the corresponding cycloadduct with moderate to high diastereoselectivity. The reaction has proved to perform better at room temperature in ionic liquids without either Lewis acid catalyst or organic solvent. Chiral ionic liquids are recycled while their efficiency is preserved.

  16. Organic chemistry of graphene: the Diels-Alder reaction.

    Science.gov (United States)

    Denis, Pablo A

    2013-11-11

    Herein, by using dispersion-corrected density functional theory, we investigated the Diels-Alder chemistry of pristine and defective graphene. Three dienes were considered, namely 2,3-dimethoxy-1,3-butadiene (DMBD), 9-methylanthracene (9MA), and 9,10-dimethylanthracene (910DMA). The dienophiles that were assayed were tetracyanoethylene (TCNE) and maleic anhydride (MA). When pristine graphene acted as the dienophile, we found that the cycloaddition products were 47-63 kcal mol(-1) less stable than the reactants, thus making the reaction very difficult. The presence of Stone-Wales translocations, 585 double vacancies, or 555-777 reconstructed double vacancies did not significantly improve the reactivity because the cycloaddition products were still located at higher energy than the reactants. However, for the addition of 910DMA to single vacancies, the product showed comparable stability to the separated reactants, whereas for unsaturated armchair edges the reaction was extremely favorable. With regards the reactions with dienophiles, for TCNE, the cycloaddition product was metastable. In the case of MA, we observed a reaction product that was less stable than the reactants by 50 kcal mol(-1) . For the reactions between graphene as a diene and the dienophiles, we found that the most-promising defects were single vacancies and unsaturated armchair edges, because the other three defects were much-less reactive. Thus, we conclude that the reactions with these above-mentioned dienes may proceed on pristine or defective sheets with heating, despite being endergonic. The same statement also applies to the dienophile maleic anhydride. However, for TCNE, the reaction is only likely to occur onto single vacancies or unsaturated armchair edges. We conclude that the dienophile character of graphene is slightly stronger than its behavior as a diene. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Electrostatic catalysis of a Diels-Alder reaction

    Science.gov (United States)

    Aragonès, Albert C.; Haworth, Naomi L.; Darwish, Nadim; Ciampi, Simone; Bloomfield, Nathaniel J.; Wallace, Gordon G.; Diez-Perez, Ismael; Coote, Michelle L.

    2016-03-01

    It is often thought that the ability to control reaction rates with an applied electrical potential gradient is unique to redox systems. However, recent theoretical studies suggest that oriented electric fields could affect the outcomes of a range of chemical reactions, regardless of whether a redox system is involved. This possibility arises because many formally covalent species can be stabilized via minor charge-separated resonance contributors. When an applied electric field is aligned in such a way as to electrostatically stabilize one of these minor forms, the degree of resonance increases, resulting in the overall stabilization of the molecule or transition state. This means that it should be possible to manipulate the kinetics and thermodynamics of non-redox processes using an external electric field, as long as the orientation of the approaching reactants with respect to the field stimulus can be controlled. Here, we provide experimental evidence that the formation of carbon-carbon bonds is accelerated by an electric field. We have designed a surface model system to probe the Diels-Alder reaction, and coupled it with a scanning tunnelling microscopy break-junction approach. This technique, performed at the single-molecule level, is perfectly suited to deliver an electric-field stimulus across approaching reactants. We find a fivefold increase in the frequency of formation of single-molecule junctions, resulting from the reaction that occurs when the electric field is present and aligned so as to favour electron flow from the dienophile to the diene. Our results are qualitatively consistent with those predicted by quantum-chemical calculations in a theoretical model of this system, and herald a new approach to chemical catalysis.

  18. A Ligand Structure-Activity Study of DNA-Based Catalytic Asymmetric Hydration and Diels-Alder Reactions

    NARCIS (Netherlands)

    Rosati, F.; Roelfes, J.G.

    A structure-activity relationship study of the first generation ligands for the DNA-based asymmetric hydration of enones and Diels-Alder reaction in water is reported. The design of the ligand was optimized resulting in a maximum ee of 83% in the hydration reaction and 75% in the Diels-Alder

  19. Synthesis of cyclopentadienyl capped polyethylene and subsequent block copolymer formation via hetero Diels-Alder (HDA) chemistry.

    Science.gov (United States)

    Espinosa, Edgar; Glassner, Mathias; Boisson, Christophe; Barner-Kowollik, Christopher; D'Agosto, Franck

    2011-09-15

    In the current contribution it is demonstrated - for the first time - that poly(ethylene) (M(n) = 1,400 as well as 2,800 g  ·  mol(-1) , PDI = 1.2) can be readily equipped with highly reactive cyclopentadienyl (Cp) end groups. The Cp terminal poly(ethylene) can subsequently be reacted in an efficient hetero Diels-Alder (HDA) reaction with macromolecules (poly(isobornyl acrylate) (M(n) = 4,600 g  ·  mol(-1) , PDI = 1.10) and poly(styrene) (M(n) = 6,300 g  ·  mol(-1) , PDI = 1.13) featuring strongly electron withdrawing thiocarbonyl thio end groups, prepared via reversible addition fragmentation chain transfer (RAFT) polymerization employing benzylpyridin-2-yldithioformate (BPDF) as transfer agent. The resulting block copolymers have been analyzed via high-temperature size exclusion chromatography (SEC) as well as nuclear magnetic resonance (NMR) spectroscopy. The current system allows for the removal of the excess of the non-poly(ethylene) containing segment via filtration of the poly(ethylene)-containing block copolymer. However, the reaction temperatures need to be judiciously selected. Characterization of the generated block copolymers at elevated temperatures can lead - depending on the block copolymer type - to the occurrence of retro Diels-Alder processes. The present study thus demonstrates that RAFT-HDA ligation can be effectively employed for the generation of block copolymers containing poly(ethylene) segments. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Niobium(V) chloride as catalyst in Diels-Alder reaction of furan ring

    International Nuclear Information System (INIS)

    Santos, Deborah A. dos; Rodrigues, Ludmila R.; Arpini, Bruno H.; Lacerda Junior, Valdemar; Greco, Sandro J.; Santos, Reginaldo B. dos; Neto, Alvaro C.; Castro, Eustaquio V.R. de

    2014-01-01

    According to the relevant literature, the Diels-Alder reaction of furan without a catalyst can last several weeks and shows a low yield due to the diene’s low reactivity. The use of Lewis acid catalysts or high pressures is described as an effective method for improving the reaction yields. This paper describes our recent study on the use of niobium pentachloride as the catalyst in Diels-Alder reactions between furan and several reactive dienophiles, among which methyl acrylate showed good yields, especially at lower temperatures. Other dienophiles have shown lower yields because of problems such as byproduct formation and the high reversibility of the reaction. (author)

  1. Niobium(V) chloride as catalyst in Diels-Alder reaction of furan ring

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Deborah A. dos; Rodrigues, Ludmila R.; Arpini, Bruno H.; Lacerda Junior, Valdemar; Greco, Sandro J.; Santos, Reginaldo B. dos; Neto, Alvaro C.; Castro, Eustaquio V.R. de, E-mail: vljuniorqui@gmail.com [Universidade Federal do Espirito Santo (UFES), Vitoria, ES (Brazil). Dept. de Quimica; Romao, Wanderson [Instituto Federal de Educacao, Ciencia e Tecnologia (IFES), Vila Velha, ES (Brazil)

    2014-05-15

    According to the relevant literature, the Diels-Alder reaction of furan without a catalyst can last several weeks and shows a low yield due to the diene’s low reactivity. The use of Lewis acid catalysts or high pressures is described as an effective method for improving the reaction yields. This paper describes our recent study on the use of niobium pentachloride as the catalyst in Diels-Alder reactions between furan and several reactive dienophiles, among which methyl acrylate showed good yields, especially at lower temperatures. Other dienophiles have shown lower yields because of problems such as byproduct formation and the high reversibility of the reaction. (author)

  2. Bioinspired intramolecular Diels-Alder reaction: a rapid access to the highly-strained cyclopropane-fused polycyclic skeleton.

    Science.gov (United States)

    Zhu, Shifa; Guo, Zhengjiang; Huang, Zhipeng; Jiang, Huanfeng

    2014-02-24

    A bioinsipred gold-catalyzed tandem Diels-Alder/Diels-Alder reaction of an enynal and a 1,3-diene, forming the highly-strained benzotricyclo[3.2.1.0(2,7) ]octane skeleton, was reported. In contrast, a Diels-Alder/Friedel-Crafts tandem reaction occurred instead when silver salts were used as the catalyst. Although both reactions experienced the similar Diels-Alder reaction of a pyrylium intermediate with a 1,3-diene, they have different reaction mechanisms. The former proceeded with a stepwise Diels-Alder reaction, while the latter one with a concerted one. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Modified lignin: Preparation and use in reversible gel via Diels-Alder reaction.

    Science.gov (United States)

    Zhou, Wanpeng; Zhang, Hui; Chen, Fangeng

    2018-02-01

    In this study, popular soda lignin was modified with either furan or maleimide ring, and the modified lignins were subjected to reversible Diels-Alder reaction. A new process was proposed to prepare the functionalized lignin. A long chain was introduced to the hydroxyl groups of lignin, and then either the furan or maleimide ring was added to the other end of the chain. The test results confirmed that either the furan ring or the maleimide ring was bound to lignin. Furan- and maleimide-functionalized lignins were also combined to generate crosslinking via Diels-Alder [4+2] cycloaddition reaction. Under appropriate conditions, the formation of a gel was identified, which reverted to liquid state after retro Diels-Alder reaction upon heating at 120°C. This study reveals the significant versatility and potential of the developed strategy for the utilization of lignin-based recyclable networks. Copyright © 2017 Elsevier B.V. All rights reserved.

  4. Asymmetric Catalytic Aza-Diels-Alder/Ring-Closing Cascade Reaction Forming Bicyclic Azaheterocycles by Trienamine Catalysis.

    Science.gov (United States)

    Li, Yang; Barløse, Casper; Jørgensen, Julie; Carlsen, Bjørn Dreiø; Jørgensen, Karl Anker

    2017-01-01

    An asymmetric catalytic aza-Diels-Alder/ring-closing cascade reaction between acylhydrazones and in situ formed trienamines is presented. The reaction proceeds through a formal aza-Diels-Alder cycloaddition, followed by a ring-closing reaction forming the hemiaminal ring leading to chiral bicyclic azaheterocycles in moderate to good yield (up to 71 %), good enantio- (up to 92 % ee) and diastereoselectivity (up to >20:1 d.r.). Furthermore, transformations are presented to show the potential application of the formed product. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Catalytic asymmetric diels-alder reaction of quinone imine ketals: a site-divergent approach.

    Science.gov (United States)

    Hashimoto, Takuya; Nakatsu, Hiroki; Maruoka, Keiji

    2015-04-07

    The catalytic asymmetric Diels-Alder reaction of quinone imine ketals with diene carbamates catalyzed by axially chiral dicarboxylic acids is reported herein. A variety of primary and secondary alkyl-substituted quinone derivatives which have not been applied in previous asymmetric quinone Diels-Alder reactions could be employed using this method. More importantly, we succeeded in developing a strategy to divert the reaction site in unsymmetrical 3-alkyl quinone imine ketals from the inherently favored unsubstituted C=C bond to the disfavored alkyl-substituted C=C bond. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Asymmetric Formal Aza-Diels-Alder Reaction of Trifluoromethyl Hemiaminals with Enones Catalyzed by Primary Amines.

    Science.gov (United States)

    Zhang, Sheng; Cha, Lide; Li, Lijun; Hu, Yanbin; Li, Yanan; Zha, Zhenggen; Wang, Zhiyong

    2016-04-15

    A primary amine-catalyzed asymmetric formal aza-Diels-Alder reaction of trifluoromethyl hemiaminals with enones was developed via a chiral gem-diamine intermediate. This novel protocol allowed facile access to structurally diverse trifluoromethyl-substituted piperidine scaffolds with high stereoselectivity. The utility of this method was further demonstrated through a concise approach to biologically active 4-hydroxypiperidine. More importantly, a stepwise mechanism involving an asymmetric induction process was proposed to rationalize the positive correlation between the chirality of the gem-diamine intermediate and the formal aza-Diels-Alder product.

  7. Recent applications of intramolecular Diels-Alder reactions to natural product synthesis

    DEFF Research Database (Denmark)

    Juhl, M.; Tanner, David Ackland

    2009-01-01

    This tutorial review presents some recent examples of intramolecular Diels-Alder (IMDA) reactions as key complexity-generating steps in the total synthesis of structurally intricate natural products. The opportunities afforded by transannular (TADA) versions of the IMDA reaction in complex molecu...... comprehensive, reviews....

  8. Diels-Alder reactions in water : Enforced hydrophobic interaction and hydrogen bonding

    NARCIS (Netherlands)

    Engberts, Jan B.F.N.

    1995-01-01

    Second-order rate constants have been measured for the Diels-Alder (DA) reactions of cyclopentadiene with dienophiles of varying hydrophobicity and hydrogen-bond acceptor capacity in water, in a series of organic solvents and in alcohol-water mixtures. The intramolecular DA reaction of

  9. DIELS-ALDER REACTIONS IN WATER - ENFORCED HYDROPHOBIC INTERACTION AND HYDROGEN-BONDING

    NARCIS (Netherlands)

    Engberts, J.B.F.N.

    Second-order rate constants have been measured for the Diels-Alder (DA) reactions of cyclopentadiene with dienophiles of varying hydrophobicity and hydrogen-bond acceptor capacity in water, in a series of organic solvents and in alcohol-water mixtures. The intramolecular DA reaction of

  10. Effects of the Hydrophobicity of the Reactants on Diels-Alder Reactions in Water

    NARCIS (Netherlands)

    Meijer, Ale; Otto, Sijbren; Engberts, Jan B.F.N.

    1998-01-01

    To assess the importance of the hydrophobicity of different parts of diene and dienophile on the aqueous acceleration of Diels-Alder reactions, second-order rate constants have been determined for the reactions of cyclopentadiene (1), 2,3-dimethyl-1,3-butadiene (4), and 1,3-cyclohexadiene (6) with

  11. Lewis acid catalysis of a Diels-Alder reaction in water

    NARCIS (Netherlands)

    Otto, S; Bertoncin, F; Engberts, JBFN

    1996-01-01

    Here we report the first detailed study of a Diels-Alder (DA) reaction that is catalyzed by Lewis acids in water. The effect of Co2+, Ni2+, Cu2+ and Zn2+ ions as Lewis acid catalysts on the rate and endo-exo selectivity of the DA reaction between the bidentate dienophiles

  12. Efficient Diels-Alder reaction of 1,2-benzoquinones with arynes and its utility in one-pot reactions.

    Science.gov (United States)

    Kaicharla, Trinadh; Bhojgude, Sachin Suresh; Biju, Akkattu T

    2012-12-21

    A new protocol for the efficient Diels-Alder reaction of 1,2-benzoquinones with arynes is reported. The aryne generated by the fluoride-induced 1,2-elimination of 2-(trimethylsilyl)aryl triflates undergoes a facile Diels-Alder reaction with 1,2-benzoquinones, affording the dioxobenzobicyclooctadienes in moderate to excellent yields. In addition, this methodology has been applied to the one-pot synthesis of benzoquinoxalinobarrelene and naphthalene derivatives.

  13. Micellar Catalysis of Diels-Alder Reactions : Substrate Positioning in the Micelle

    NARCIS (Netherlands)

    Rispens, Theo; Engberts, Jan B.F.N.

    2002-01-01

    We have studied the kinetics of the Diels-Alder reactions of cyclopentadiene, sorbyl alcohol, and sorbyltrimethylammonium bromide with a series of N-substituted maleimides in micellar media. Micellar rate constants have been determined and were found to be 20-40 times lower than the respective

  14. Stepwise or concerted? DFT study on the mechanism of ionic Diels-Alder reaction of chromanes

    Directory of Open Access Journals (Sweden)

    Haghdadi Mina

    2016-01-01

    Full Text Available The stepwise and concerted Ionic Diels-Alder reaction between phenyl (pyridin-2-ylmethylene oxonium and styrene derivatives are explored using theoretical method. The results support using computational method via persistent intermediates. The DFT method was essential to reproduce a reasonable potential energy surface for these challenging systems.

  15. Diels-Alder Reactions in Water. Effects of Hydrophobicity and Hydrogen Bonding

    NARCIS (Netherlands)

    Otto, Sijbren; Blokzijl, Wilfried; Engberts, Jan B.F.N.

    1994-01-01

    In order to check whether the activated complex for the Diels-Alder reactions of 5-substituted 1,4-naphthoquinones with cyclopentadiene is more polar in water than in other solvents, we have determined the substituent effects in seven different solvents. The substituent effects gradually decrease

  16. Unsaturated aldehydes as alkene equivalents in the Diels-Alder reaction

    DEFF Research Database (Denmark)

    Taarning, Esben; Madsen, Robert

    2008-01-01

    A one-pot procedure is described for using alpha,beta-unsaturated aldehydes as olefin equivalents in the Diels-Alder reaction. The method combines the normal electron demand cycloaddition with aldehyde dienophiles and the rhodium-catalyzed decarbonylation of aldehydes to afford cyclohexenes...

  17. A Diels-Alder Reaction Conducted Within the Parameters of Aqueous Organocatalysis: Still Just Smoke and Mirrors

    Science.gov (United States)

    Stowe, G. Neil

    2010-01-01

    Conducting reactions using water as solvent is a highly prized goal for the organic chemist. Based upon recent literature and our continuing interest in the field of aqueous organocatalysis, we tested the scope of an enamine based Diels-Alder reaction using (±)-nornicotine, proline and a proline derivative as aqueous organocatalysts. Unfortunately, none of the examined catalysts under aqueous conditions proved useful, leaving the aqueous Diels-Alder reaction as an elusive goal. PMID:21516231

  18. Growth of Fullerene Fragments Using the Diels-Alder Cycloaddition Reaction: First Step towards a C60 Synthesis by Dimerization

    Directory of Open Access Journals (Sweden)

    Julio A. Alonso

    2013-02-01

    Full Text Available Density Functional Theory has been used to model the Diels-Alder reactions of the fullerene fragments triindenetriphenilene and pentacyclopentacorannulene with ethylene and 1,3-butadiene. The purpose is to prove the feasibility of using Diels-Alder cycloaddition reactions to grow fullerene fragments step by step, and to dimerize fullerene fragments, as a way to obtain C60. The dienophile character of the fullerene fragments is dominant, and the reaction of butadiene with pentacyclopentacorannulene is favored.

  19. One-step versus two-step mechanism of Diels-Alder reaction of 1-chloro-1-nitroethene with cyclopentadiene and furan.

    Science.gov (United States)

    Jasiński, Radomir

    2017-08-01

    DFT computational study shows that Diels-Alder (DA) reactions of 1-chloro-1-nitroethene with cyclopentadiene and furan have polar nature. However, their mechanism is substantially different. In particular, 1-chloro-1-nitroethene react with cyclopentadiene according to one-step mechanism. In the same time, more favourable channel associated with the P-DA reaction between furan and 1-chloro-1-nitroethene is a domino process, that comprises an initial hetero-Diels-Alder reaction yielding a [2+4] cycloadduct, which experiences a subsequent [3,3] sigmatropic shift to yield the expected formal [4+2] cycloadduct. This is a consequence of more polar nature of reaction, due to higher nucleophilicity of furan in comparison to cyclopentadiene. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Well-defined Polymethylene-Based Co/Terpolymers by Combining Anthracene/Maleimide Diels-Alder Reaction with Polyhomologation

    KAUST Repository

    Hadjichristidis, Nikolaos; Alkayal, Nazeeha

    2015-01-01

    A novel strategy towards well-defined polymethylene-based co/terpolymers, by combining anthracene/maleimide Diels-Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: a

  1. A theoretical investigation on the regioselectivity of the intramolecular hetero Diels-Alder and 1,3-dipolar cycloaddition of 2-vinyloxybenzaldehyde derivatives

    Directory of Open Access Journals (Sweden)

    Hamzehloueian Mahshid

    2014-01-01

    Full Text Available The present study reports a systematic computational analysis of the two possible pathways, fused and bridged, for an intramolecular hetero Diels-Alder (IMHDA and an intramolecular 1,3-dipolar cycloaddition (IMDCA of 2-vinyloxybenzaldehyde derivatives. The potential energy surface analysis for both reactions is in agreement with experimental observations. The activation energies associated with the two regioisomeric channels in IMHDA reaction show that the bridged product is favored, although in IMDCA, the most stable TS results the fused product. The global electronic properties of fragments within each molecule were studied to discuss the reactivity patterns and charge transfer direction in the intramolecular processes. The asynchronicity of the bond formation and aromaticity of the optimized TSs in the Diels-Alder reaction as well as cycloaddition reaction were evaluated. Finally, 1H NMR chemical shifts of the possible regioisomers have been calculated using the GIAO method which of the most stable products are in agreement with the experimental data in the both reaction.

  2. Quinones as dienophiles in the Diels-Alder reaction: history and applications in total synthesis.

    Science.gov (United States)

    Nawrat, Christopher C; Moody, Christopher J

    2014-02-17

    In the canon of reactions available to the organic chemist engaged in total synthesis, the Diels-Alder reaction is among the most powerful and well understood. Its ability to rapidly generate molecular complexity through the simultaneous formation of two carbon-carbon bonds is almost unrivalled, and this is reflected in the great number of reported applications of this reaction. Historically, the use of quinones as dienophiles is highly significant, being the very first example investigated by Diels and Alder. Herein, we review the application of the Diels-Alder reaction of quinones in the total synthesis of natural products. The highlighted examples span some 60 years from the landmark syntheses of morphine (1952) and reserpine (1956) by Gates and Woodward, respectively, through to the present day examples, such as the tetracyclines. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. The unexpected product of Diels-Alder reaction between "indanocyclon" and maleimide

    Science.gov (United States)

    Dobrowolski, Michał A.; Roszkowski, Piotr; Struga, Marta; Szulczyk, Daniel

    2017-02-01

    A heterocyclic compound commonly known as "indanocyclon" undergoes an unexpected Diels-Alder addition with maleimide. The resulting product has been isolated and characterized in order to get an information about its structure and possible mechanism of the reaction. Extensive comparison of single crystal properties of 3-(2,8-dioxo-1,3-diphenyl-2,8-dihydrocyclopenta[a]inden-8a(1H)-yl)pyrrolidine-2,5-dione and favorable product of the reaction has been also performed.

  4. New L-Serine Derivative Ligands as Cocatalysts for Diels-Alder Reaction

    Science.gov (United States)

    Sousa, Carlos A. D.; Rodríguez-Borges, José E.; Freire, Cristina

    2013-01-01

    New L-serine derivative ligands were prepared and tested as cocatalyst in the Diels-Alder reactions between cyclopentadiene (CPD) and methyl acrylate, in the presence of several Lewis acids. The catalytic potential of the in situ formed complexes was evaluated based on the reaction yield. Bidentate serine ligands showed good ability to coordinate medium strength Lewis acids, thus boosting their catalytic activity. The synthesis of the L-serine ligands proved to be highly efficient and straightforward. PMID:24383009

  5. Using chiral ionic liquid additives to enhance asymmetric induction in a Diels-Alder reaction.

    Science.gov (United States)

    Goodrich, P; Nimal Gunaratne, H Q; Hall, L; Wang, Y; Jin, L; Muldoon, M J; Ribeiro, A P C; Pombeiro, A J L; Pârvulescu, V I; Davey, P; Hardacre, C

    2017-01-31

    A bis-oxazoline ligand has been complexed using Cu(ii) and Zn(ii) trifluoromethanesulfonate and a range of chiral ionic liquid (CIL) additives based on natural products were used as a co-catalyst for a Diels-Alder reaction. The catalytic performance of these systems was compared for the asymmetric Diels-Alder reaction between N-acryloyloxazolidinone and cyclopentadiene with and without the presence of a CIL additive. In the absence of the CIL, both catalysts resulted in low enantioselectivities in conventional solvents and ionic liquids. However, whilst only a minor effect of the CIL was observed for the Cu based catalyst, in the case of the Zn based catalyst, significant enhancements in endo enantioselectivity of up to 50% were found on the addition of a CIL.

  6. Hydrogen-Bonding Catalysis of Tetraalkylammonium Salts in an Aza-Diels-Alder Reaction.

    Science.gov (United States)

    Kumatabara, Yusuke; Kaneko, Shiho; Nakata, Satoshi; Shirakawa, Seiji; Maruoka, Keiji

    2016-08-05

    A piperidine-derived tetraalkylammonium salt with a non-coordinating counteranion worked as an effective hydrogen-bonding catalyst in an aza-Diels-Alder reaction of imines and a Danishefsky diene. The hydrogen-bonding interaction between the ammonium salt and an imine was observed as part of a (1) H NMR titration study. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Origin of Exo/Endo Selectivity in the Intramolecular Diels-Alder Reaction

    International Nuclear Information System (INIS)

    Yan, Shihai; Ryu, Do Hyun; Lee, Jin Yong

    2010-01-01

    The stereoselectivity of the intramolecular Diels-Alder reactions of 1 and its derivatives were investigated by ab initio calculations. The stereoselectivity mainly originates from the steric repulsion and the orbital interactions. The additional s-cis and s-trans conformations by introducing the carbonyl group at the neighbor of diene or dienophile may change the stereoselectivity, hence this kind of substitution can be utilized for stereoselective asymmetric synthesis

  8. A thermal dehydrogenative Diels-Alder reaction of styrenes for the concise synthesis of functionalized naphthalenes.

    Science.gov (United States)

    Kocsis, Laura S; Benedetti, Erica; Brummond, Kay M

    2012-09-07

    Functionalized naphthalenes are valuable building blocks in many important areas. A microwave-assisted, intramolecular dehydrogenative Diels-Alder reaction of styrenyl derivatives to provide cyclopenta[b]naphthalene substructures not previously accessible using existing synthetic methods is described. The synthetic utility of these uniquely functionalized naphthalenes was demonstrated by a single-step conversion of one of these cycloadducts to a fluorophore bearing a structural resemblance to Prodan.

  9. Enantio- and Stereoselective Construction of Atisane Scaffold via Organocatalytic Intramolecular Michael Reaction and Diels-Alder Reaction.

    Science.gov (United States)

    Sekita, Hiroko; Adachi, Kyohei; Kobayashi, Ippei; Sato, Yusuke; Nakada, Masahisa

    2017-05-05

    An enantio- and stereoselective construction of the atisane scaffold via organocatalytic intramolecular Michael reaction and Diels-Alder reaction is described. The organocatalytic intramolecular Michael reaction has been found to stereoselectively generate a trans-stereodiad comprising an all-carbon quaternary and a tertiary stereogenic centers. Use of the chiral secondary amine bearing thiourea with benzoic acid as additive is the key to obtaining the desired product with excellent ee in synthetically acceptable yield. The prepared chiral building block has been successfully converted to the compound including the atisane scaffold via the highly stereoselective intramolecular Diels-Alder reaction.

  10. The Diels-Alder reaction: A powerful tool for the design of drug delivery systems and biomaterials.

    Science.gov (United States)

    Gregoritza, Manuel; Brandl, Ferdinand P

    2015-11-01

    Click reactions have the potential to greatly facilitate the development of drug delivery systems and biomaterials. These reactions proceed under mild conditions, give high yields, and form only inoffensive by-products. The Diels-Alder cycloaddition is one of the click reactions that do not require any metal catalyst; it is one of the most useful reactions in synthetic organic chemistry and material design. Herein, we highlight possible applications of the Diels-Alder reaction in pharmaceutics and biomedical engineering. Particular focus is placed on the synthesis of polymers and dendrimers for drug delivery, the preparation of functionalized surfaces, bioconjugation techniques, and applications of the Diels-Alder reaction in nanotechnology. Moreover, applications of the reaction for the preparation of hydrogels for drug delivery and tissue engineering are reviewed. A general introduction to the Diels-Alder reaction is presented, along with a discussion of potential pitfalls and challenges. At the end of the article, we provide a set of tools that may facilitate the application of the Diels-Alder reaction to solve important pharmaceutical or biomedical problems. Copyright © 2015 Elsevier B.V. All rights reserved.

  11. A Kinetic Study of the Diels-Alder Reaction. An Experiment Illustrating Simple Second-Order Reaction Kinetics.

    Science.gov (United States)

    Silvestri, Michael G.; Dills, Charles E.

    1989-01-01

    Describes an organic chemistry experiment for teaching the basic concepts of chemical kinetics. Provides background information about first- and second-order reactions, experimental procedures of the Diels-Alder reaction between cyclopentadiene and dimethyl fumarate, and the experimental results. (YP)

  12. Investigating radical cation chain processes in the electrocatalytic Diels-Alder reaction.

    Science.gov (United States)

    Imada, Yasushi; Okada, Yohei; Chiba, Kazuhiro

    2018-01-01

    Single electron transfer (SET)-triggered radical ion-based reactions have proven to be powerful options in synthetic organic chemistry. Although unique chain processes have been proposed in various photo- and electrochemical radical ion-based transformations, the turnover number, also referred to as catalytic efficiency, remains unclear in most cases. Herein, we disclose our investigations of radical cation chain processes in the electrocatalytic Diels-Alder reaction, leading to a scalable synthesis. A gram-scale synthesis was achieved with high current efficiency of up to 8000%. The reaction monitoring profiles showed sigmoidal curves with induction periods, suggesting the involvement of intermediate(s) in the rate determining step.

  13. Nitropyrroles, Diels-Alder reactions assisted by microwave irradiation and solvent effect. An experimental and theoretical study

    Science.gov (United States)

    Mancini, Pedro M. E.; Kneeteman, María N.; Cainelli, Mauro; Ormachea, Carla M.; Domingo, Luis R.

    2017-11-01

    The behaviors of N-tosylnitropyrroles acting as electrophilic dienophiles in polar Diels-Alder reactions joint to different dienes of increeased nucleophilicity are analyzed. The reactions were developed under microwave irradiation using toluene or protic ionic liquids (PILs) as solvents and in free solvent conditions. In all the cases explored we observed good yields in short reaction times. For these reactions, the free solvent condition and the use of protic ionic liquids as solvents offer similar results. However, the free solvent conditions favor environmental sustainability. The role of PILs in these polar Diels-Alder reactions has been theoretically studied within the Molecular Electron Density Theory.

  14. Deeper Insight into the Diels-Alder Reaction through the Activation Strain Model.

    Science.gov (United States)

    Fernández, Israel; Bickelhaupt, F Matthias

    2016-12-06

    In this Focus Review, we present the application of the so-called Activation Strain Model of chemical reactivity to the Diels-Alder cycloaddition reaction. To this end, representative recent examples have been selected to illustrate the power of this new computational approach to gain a deeper quantitative understanding of this fundamental process in chemistry. We cover a wide range of issues, such as, the "endo-rule", reactivity trends emerging from systematic variation in the reactants' strain, and cycloaddition reactions involving relevant species in material science, that is, fullerenes, polycyclic aromatic hydrocarbons and nanotubes. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Synthesis of the AB ring system of clifednamide utilizing Claisen rearrangement and Diels-Alder reaction as key steps.

    Science.gov (United States)

    Loke, Inga; Bentzinger, Guillaume; Holz, Julia; Raja, Aruna; Bhasin, Aman; Sasse, Florenz; Köhn, Andreas; Schobert, Rainer; Laschat, Sabine

    2016-01-21

    In order to construct the functionalized AB ring system of clifednamide, member of the class of macrocyclic tetramic acid lactams, a synthesis was developed which utilized an Ireland-Claisen rearrangement and an intramolecular Diels-Alder reaction. Starting from di-O-isopropylidene-d-mannitol the allyl carboxylate precursor for the sigmatropic rearrangement was prepared. This rearrangement proceeded diastereoselectively only in the presence of an allyl silyl ether instead of the parent enone in the side chain, as suggested by deuteration experiments. A subsequent Diels-Alder reaction yielded the target ethyl hexahydro-1H-indene-carboxylate with high diastereoselectivity. Quantum-chemical investigations of this intramolecular Diels-Alder reaction support the proposed configuration of the final product.

  16. Medium-Ring Effects on the Endo/Exo Selectivity of the Organocatalytic Intramolecular Diels-Alder Reaction.

    Science.gov (United States)

    Hooper, Joel F; James, Natalie C; Bozkurt, Esra; Aviyente, Viktorya; White, Jonathan M; Holland, Mareike C; Gilmour, Ryan; Holmes, Andrew B; Houk, K N

    2015-12-18

    The intramolecular Diels-Alder reaction has been used as a powerful method to access the tricyclic core of the eunicellin natural products from a number of 9-membered-ring precursors. The endo/exo selectivity of this reaction can be controlled through a remarkable organocatalytic approach, employing MacMillan's imidazolidinone catalysts, although the mechanistic origin of this selectivity remains unclear. We present a combined experimental and density functional theory investigation, providing insight into the effects of medium-ring constraints on the organocatalyzed intramolecular Diels-Alder reaction to form the isobenzofuran core of the eunicellins.

  17. Application of Carbohydrate-Templated Asymmetric Diels-Alder Reaction to the Syntheses of ent-Penicillones A and B.

    Science.gov (United States)

    Weng, Chia-Hao; Hsu, Day-Shin; Liao, Chun-Chen

    2016-11-18

    Total syntheses of ent-penicillones A (ent-1) and B (ent-2) from 3,5-dimethylcatechol (3) were accomplished in 10 and 9 synthetic steps, respectively. A carbohydrate-templated asymmetric intramolecular Diels-Alder reaction of a masked o-benzoquinone (MOB) 9 and an aqueous acid-catalyzed intramolecular aldol reaction are the key synthetic steps. In addition, the absolute configurations of the bicyclo[2.2.2]oct-5-en-2-one core obtained from the per-O-benzylated α-d-glucopyranosyl as a carbohydrate template in the intramolecular Diels-Alder reaction of MOBs were revised.

  18. Quinine-Promoted, Enantioselective Boron-Tethered Diels-Alder Reaction by Anomeric Control of Transition State Conformation.

    Science.gov (United States)

    Scholl, Katie; Dillashaw, John; Timpy, Evan; Lam, Yu-Hong; DeRatt, Lindsey; Benton, Tyler R; Powell, Jacqueline P; Houk, Kendall N; Morgan, Jeremy B

    2018-05-01

    Diels-Alder reactions of tethered vinyl-metal species offer the opportunity to fashion highly functionalized diol intermediates for synthesis. We have developed the first enantioselective boron-tethered Diels-Alder reaction using quinine as a chiral promoter. Quinine recovery, enantioselectivity enhancement, and manipulation of the cyclohexene core are also investigated. DFT modeling calculations confirm the role of quinine as a bidentate ligand enhancing reaction rates. The enantioselectivity of the cycloaddition is proposed to originate from a boron-centered anomeric effect.

  19. alpha,beta-unsaturated 2-acyl imidazoles as a practical class of dienophiles for the DNA-Based catalytic asymmetric diels-alder reaction in water

    NARCIS (Netherlands)

    Boersma, A.J.; Feringa, B.L.; Roelfes, G.

    2007-01-01

    alpha,beta-Unsaturated 2-acyl imidazoles are a novel and practical class of dienophiles for the DNA-based catalytic asymmetric Diels-Alder reaction in water. The Diels-Alder products are obtained with very high diastereoselectivities and enantioselectivities in the range of 83-98%. The catalytic

  20. Cascade olefin isomerization/intramolecular Diels-Alder reaction catalyzed by N-heterocyclic carbenes.

    Science.gov (United States)

    Kowalczyk, Marcin; Lupton, David W

    2014-05-19

    The addition of an N-heterocyclic carbene to the carbonyl group of an α,β,γ,δ-unsaturated enol ester affords a hemiacetal azolium intermediate that enables a cascade olefin isomerization/Diels-Alder reaction, for which mechanistic studies implicate Lewis base catalysis. Preliminary studies into the utility of the products have been undertaken with reductive and oxidative cleavage, giving materials for potential use in complex-target synthesis. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. A computational study of the Diels Alder reactions involving acenes: reactivity and aromaticity

    Science.gov (United States)

    Cheng, Mei-Fun; Li, Wai-Kee

    2003-01-01

    Ab initio and DFT methods have been used to study the Diels-Alder reactivity and the aromaticity of four linear acenes, namely, naphthalene, anthracene, tetracene and pentacene. In total, eight additional pathways between ethylene and four acenes have been studied and all of them are concerted and exothermic reactions. It is found that the most reactive sites on the acenes are the center ring's meso-carbons. Also, reactivity decreases along the series pentacene > tetracene > anthracene > naphthalene. In addition, the NICS results indicate that the most reactive rings in the acenes are those with the highest aromaticity. These results are consistent with those of other theoretical studies and experiments.

  2. The Inverse Demand Oxa-Diels-Alder Reaction of Resorcinarenes: An Experimental and Theoretical Analysis of Regioselectivity and Diastereoselectivity.

    Science.gov (United States)

    Stefańska, Karolina; Jędrzejewska, Hanna; Wierzbicki, Michał; Szumna, Agnieszka; Iwanek, Waldemar

    2016-07-15

    The Diels-Alder reaction enables introduction of new functionalities onto the resorcinarene skeleton with simultaneous generation of new stereogenic centers and expansion of the internal cavity. We present highly regio- and diastereoselective inverse electron demand oxa-Diels-Alder reactions of resorcinarene ortho-quinone methide with benzofuran and indene, each generating 12 new stereogenic centers. The mechanism and reasons for regioselectivity and diastereoselectivity were analyzed using theoretical calculations (NBO charges, Fukui functions, transition state energies, and thermodynamic stability of the products). Enantiomers were separated, and their configurations were determined by comparison of experimental and theoretical electronic circular dichroism spectra.

  3. Chiral Pyridinium Phosphoramide as a Dual Brønsted Acid Catalyst for Enantioselective Diels-Alder Reaction.

    Science.gov (United States)

    Nishikawa, Yasuhiro; Nakano, Saki; Tahira, Yuu; Terazawa, Kanako; Yamazaki, Ken; Kitamura, Chitoshi; Hara, Osamu

    2016-05-06

    Chiral pyridinium phosphoramide 1·HX was designed to be a new class of chiral Brønsted acid catalyst in which both the pyridinium proton and the adjacent imide-like proton activated by the electron-withdrawing pyridinium moiety could work cooperatively as strong dual proton donors. The potential of 1·HX was shown in the enantioselective Diels-Alder reactions of 1-amino dienes with various dienophiles including N-unsubstituted maleimide, which has yet to be successfully used in an asymmetric Diels-Alder reaction.

  4. Mechanistic Insight into the Dehydro-Diels-Alder Reaction of Styrene-Ynes.

    Science.gov (United States)

    Kocsis, Laura S; Kagalwala, Husain N; Mutto, Sharlene; Godugu, Bhaskar; Bernhard, Stefan; Tantillo, Dean J; Brummond, Kay M

    2015-12-04

    The Diels-Alder reaction represents one of the most thoroughly studied and well-understood synthetic transformations for the assembly of six-membered rings. Although intramolecular dehydro-Diels-Alder (IMDDA) reactions have previously been employed for the preparation of naphthalene and dihydronaphthalene substrates, low yields and product mixtures have reduced the impact and scope of this reaction. Through the mechanistic studies described within, we have confirmed that the thermal IMDDA reaction of styrene-ynes produces a naphthalene product via loss of hydrogen gas from the initially formed cycloadduct, a tetraenyl intermediate. Alternatively, the dihydronaphthalene product is afforded from the same tetraenyl intermediate via a radical isomerization process. Moreover, we have identified conditions that can be used to achieve efficient, high-yielding, and selective IMDDA reactions of styrene-ynes to form either naphthalene or dihydronaphthalene products. The operational simplicity and retrosynthetic orthogonality of this method for the preparation of naphthalenes and dihydronaphthalenes makes this transformation appealing for the synthesis of medicinal and material targets. The mechanistic studies within may impact the development of other thermal transformations.

  5. New Insights into the Diels-Alder Reaction of Graphene Oxide.

    Science.gov (United States)

    Brisebois, Patrick P; Kuss, Christian; Schougaard, Steen B; Izquierdo, Ricardo; Siaj, Mohamed

    2016-04-18

    Graphene oxide is regarded as a major precursor for graphene-based materials. The development of graphene oxide based derivatives with new functionalities requires a thorough understanding of its chemical reactivity, especially for canonical synthetic methods such as the Diels-Alder cycloaddition. The Diels-Alder reaction has been successfully extended with graphene oxide as a source of diene by using maleic anhydride as a dienophile, thereby outlining the presence of the cis diene present in the graphene oxide framework. This reaction provides fundamental information for understanding the exact structure and chemical nature of graphene oxide. On the basis of high-resolution (13) C-SS NMR spectra, we show evidence for the formation of new sp(3) carbon centers covalently bonded to graphene oxide following hydrolysis of the reaction product. DFT calculations are also used to show that the presence of a cis dihydroxyl and C vacancy on the surface of graphene oxide are promoting the reaction with significant negative reaction enthalpies. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. The Hexadehydro-Diels-Alder Cycloisomerization Reaction Proceeds by a Stepwise Mechanism.

    Science.gov (United States)

    Wang, Tao; Niu, Dawen; Hoye, Thomas R

    2016-06-29

    We report here experiments showing that the hexadehydro-Diels-Alder (HDDA) cycloisomerization reaction proceeds in a stepwise manner-i.e., via a diradical intermediate. Judicious use of substituent effects was decisive. We prepared (i) a series of triyne HDDA substrates that differed only in the R group present on the remote terminus of the diynophilic alkyne and (ii) an analogous series of dienophilic alkynes (n-C7H15COC≡CR) for use in classical Diels-Alder (DA) reactions (with 1,3-cyclopentadiene). The R groups were CF3, CHO, COMe/Et, CO2Me, CONMe2/Et2, H, and 1-propynyl. The relative rates of both the HDDA cyclization reactions and the simple DA cycloadditions were measured. The reactivity trends revealed a dramatic difference in the behaviors of the CF3 (slowest HDDA and nearly fastest DA) and 1-propynyl (fastest HDDA and slowest DA) containing members of each series. These differences can be explained by invoking radical-stabilizing energies rather than electron-withdrawing effects as the dominating feature of the HDDA reaction.

  7. Silver-catalyzed formal inverse electron-demand Diels-Alder reaction of 1,2-diazines and siloxy alkynes.

    Science.gov (United States)

    Türkmen, Yunus E; Montavon, Timothy J; Kozmin, Sergey A; Rawal, Viresh H

    2012-06-06

    A highly effective silver-catalyzed formal inverse electron-demand Diels-Alder reaction of 1,2-diazines and siloxy alkynes has been developed. The reactions provide ready access to a wide range of siloxy naphthalenes and anthracenes, which are formed in good to high yields, under mild reaction conditions, using low catalyst loadings.

  8. Unconventional exo selectivity in thermal normal-electron-demand Diels-Alder reactions

    Science.gov (United States)

    Ho, Guo-Ming; Huang, Ci-Jhang; Li, Elise Yu-Tzu; Hsu, Sheng-Kai; Wu, Ti; Zulueta, Medel Manuel L.; Wu, Kevin Binchia; Hung, Shang-Cheng

    2016-10-01

    The Diels-Alder reaction is a useful tool for generating functionalized chiral molecules through the concerted cycloaddition of dienes and dienophiles leading to six-membered rings. Traditionally, the selective predictions of the products rely heavily on consideration of the secondary orbital interactions that stabilize the endo pathway. However, there remain some basic examples defying this notion and produce the exo-isomer as major product. Here we systematically evaluated of the structural features driving exo selectivity in thermal normal-electron-demand Diels-Alder reactions. Substitution at the Cβ position and the size and electronegativity of the electron-withdrawing group of the dienophile are contributing factors. Experimental and computational studies both point toward the steric and electrostatic forces between the substituents in both the diene and the dienophile that increase the likelihood of the exo pathway. For these substrates, the dominance of the endo pathway is reduced by transition state distortions and poor structural alignments of the reacting partners. We also noted the tilt of the dienophile with respect to the diene causing steric strain on the functionalities at the more advanced bond forming carbon-carbon position of the endo transition state. Insights into such factors may benefit synthetic planning and asserting control over this important named reaction.

  9. Retro-Diels-Alder reaction in aqueous solution : Toward a better understanding of organic reactivity in water

    NARCIS (Netherlands)

    Wijnen, J.W.; Engberts, Jan B.F.N.

    1997-01-01

    The retro-Diels-Alder (RDA) reaction of anthracenedione 1a proceeds considerably faster in aqueous solutions than in organic solvents. Addition of organic solvents to water retards the reaction, whereas glucose induces a modest acceleration. SDS micelles induce a considerable retardation, but even

  10. Design and synthesis of fused polycycles via Diels-Alder reaction and ring-rearrangement metathesis as key steps.

    Science.gov (United States)

    Kotha, Sambasivarao; Ravikumar, Ongolu

    2015-01-01

    Atom efficient processes such as the Diels-Alder reaction (DA) and the ring-rearrangement metathesis (RRM) have been used to design new polycycles. In this regard, ruthenium alkylidene catalysts are effective in realizing the RRM of bis-norbornene derivatives prepared by DA reaction and Grignard addition. Here, fused polycycles are assembled which are difficult to produce by conventional synthetic routes.

  11. No evidence found for Diels-Alder reaction products in soybean oil oxidized at the frying temperature by NMR study

    Science.gov (United States)

    It has been generally accepted that the Diels-Alder reaction mechanism is one of the major reaction mechanisms to produce dimers and polymers during heating process of vegetable oil. Soybean oil oxidized at 180 °C for 24 hrs with 1.45 surface area-to-volume ratio showed 36.1% polymer peak area in g...

  12. Characterization and kinetic study of Diels-Alder reaction: Detailed study on N-phenylmaleimide and furan based benzoxazine with potential self-healing application

    Directory of Open Access Journals (Sweden)

    Z. Stirn

    2016-07-01

    Full Text Available The Diels-Alder reaction between N-phenylmaleimide and benzoxazine bearing furan group was investigated for the purpose of successful appliance of self-healing in benzoxazine polymer networks. The reaction as a function of temperature/time was performed in molten state and in a solution, where also the kinetic study was performed. The Diels-Alder reaction leads to a mixture of two diastereomers: endo presented at lower cyclo-reversion temperature and exo at higher. Therefore, the conversion rates and exo/endo ratio were studied in detail for both systems. For instance, in molten state the Diels-Alder reaction was triggered by the temperature of the melting point at 60 °C with exo/endo ratio preferable to the endo adduct. The study of the kinetics in a solution revealed that the Diels-Alder reaction followed typical bimolecular reversible second-order reaction. The activation energies were close to the previous literature data; 48.4 and 51.9 kJ·mol–1 for Diels-Alder reaction, and 91.0 and 102.3 kJ·mol–1 for retro-Diels-Alder reaction, in acetonitrile and chloroform, respectively. The reaction equilibrium in a solution is much more affected by the retro-Diels-Alder reaction than in a molten state. This study shows detailed investigation of DA reaction and provides beneficial knowledge for further use in self-healing polymer networks.

  13. Investigation of the possibility of functionalization of C20 fullerene by benzene via Diels-Alder reaction

    Science.gov (United States)

    Siadati, Seyyed Amir; Nami, Navabeh

    2016-10-01

    C20 fullerene, this novel species with all its pentagonal faces has displayed some unique operations in making fast pericyclic reactions. As an example, the high dienophile character of the C20 fullerene and the ability of this species in making an ultra-fast Diels-Alder reaction with 1,3-butadiene, has been recently reported. Moreover, new experimental reports claim that the C60 fullerene, one of the fullerene family, could make a Diels-Alder reaction with the central ring of anthracene and make the ring non-aromatic. These reports may encourage researchers to do more studies on the properties of this small carbon cage. To address this question, the present research has discussed all the reaction channels of the Diels-Alder cycloaddition of benzene molecule as a 1,3-diene with the C20 fullerene in order to answer this question: ;Is C20fullerene able to make a Diels-Alder reaction with this molecule?;.

  14. Diels-Alder Reaction of Isobenzofurans/Cyclopentadienones with Tetrathiafulvalene: Preparation of Naphthalene, Fluoranthene, and Fluorenone Derivatives.

    Science.gov (United States)

    Karunakaran, Jayachandran; Mohanakrishnan, Arasambattu K

    2018-02-16

    Diels-Alder reaction of 1,3-diarylbenzo[c]furan/cyclopentadienone with TTF followed by triflic acid mediated cleavage of the resulting adducts led to the formation of the respective 1,4-diaryl substituted naphthalenes, fluoranthenes, and fluorenones. The photophysical properties of representative diaryl-substituted hydrocarbons are also reported.

  15. N,N-Diethyl-1-Tosyl-3-Indoleglyoxylamide as a Dienophile in Diels-Alder Reactions. Hyperbaric vs. Thermal Conditions

    Directory of Open Access Journals (Sweden)

    B. Biolatto

    2000-03-01

    Full Text Available Under high pressure conditions, the Diels-Alder reaction involving N,N-diethyl-1-tosyl-3-indoleglyoxylamide and 1-(N-acetyl-N-propylamino-1,3-butadiene produces a highly functionalized intermediate for the synthesis of Indole Alkaloids, in shorter times and higher yields than under thermal conditions.

  16. Microwave-Enhanced Organic Syntheses for the Undergraduate Laboratory: Diels-Alder Cycloaddition, Wittig Reaction, and Williamson Ether Synthesis

    Science.gov (United States)

    Baar, Marsha R.; Falcone, Danielle; Gordon, Christopher

    2010-01-01

    Microwave heating enhanced the rate of three reactions typically performed in our undergraduate organic chemistry laboratory: a Diels-Alder cycloaddition, a Wittig salt formation, and a Williamson ether synthesis. Ninety-minute refluxes were shortened to 10 min using a laboratory-grade microwave oven. In addition, yields improved for the Wittig…

  17. A mechanochemical study of the effects of compression on a Diels-Alder reaction

    Science.gov (United States)

    Jha, Sanjiv K.; Brown, Katie; Todde, Guido; Subramanian, Gopinath

    2016-08-01

    We examine the effects of compressive external forces on the mechanisms of the parent Diels-Alder (DA) reaction between butadiene and ethylene. Reaction pathways and transition states were calculated using the nudged elastic band method within a mechanochemical framework at the CASSCF(6,6)/6-31G**, as well as the B3LYP/6-311++G** levels of theory. Our results suggest that compressive hydrostatic pressure lowers the energy barrier for the parent DA reaction while suppressing the undesirable side reaction, thereby leading to a direct increase in the yield of cyclohexene. Compressive pressure also increases the exothermicity of the parent DA reaction, which would lead to increased temperatures in a reaction vessel and thereby indirectly increase the yield of cyclohexene. Our estimates indicate that the compression used in our study corresponds to a range of 68 MPa-1410 MPa.

  18. Metal Chelation in Asymmetric Diels-Alder Reaction (II)

    International Nuclear Information System (INIS)

    Chung, Kyoo Hyun; Chu, Chan Kook; Chang, Min Ho

    2004-01-01

    In the reaction, the inverse asymmetric induction has been observed by the use of either monovalent Lewis acids or divalent Lewis acids. The reaction of the acrylate of (S)-ethyl lactate with cyclopentadiene proceeded with 86% endo-S selectivity in the presence of TiCl 4 , divalent Lewis acid, whereas did with 32% endo-R selectivity in the presence of BF 3 ·Et 2 O, monovalent Lewis acid. When a chiral dienophile which was prepared from benzyl ester of (S)-proline or methyl ester of (S)-indoline-2-carboxylic acid was employed in the reaction, a similar diastereofacial selectivity was also observed. Recently, we reported the similar selectivity in the reaction of methyl (2S,5S)-(5-t-butyldimethylsilyloxypiperidin- 2-yl)ethanoatewith cyclopentadiene.

  19. DFT studies for the substituent effect on the diels-alder reaction of 1,4-diaza-1,3-butadienes

    International Nuclear Information System (INIS)

    Lee, Gab Yong

    2001-01-01

    DFT calculations have been performed on several substituted 1,4-diaza-1,3-butadienes (1,4-DABs) with electron donating and withdrawing groups at the terminal two nitrogens to investigate the reactivity of Diels-Alder reaction with acrolein. The calculated FMO (Frontier Molecular orbital) energies for the optimized 1,4-disubstituted-1,4DABs have been used to explain both normal and inverse electron demand Diels-Alder reactions. It is shown that the electron donating and withdrawing substituents lead to the normal(HOMO diene controlled) and inverse electron demand (LUMO diene controlled) Diels-Alder reactions, respectively

  20. Exploring Reaction Mechanism on Generalized Force Modified Potential Energy Surfaces (G-FMPES) for Diels-Alder Reaction

    Science.gov (United States)

    Jha, Sanjiv; Brown, Katie; Subramanian, Gopinath

    We apply a recent formulation for searching minimum energy reaction path (MERP) and saddle point to atomic systems subjected to an external force. We demonstrate the effect of a loading modality resembling hydrostatic pressure on the trans to cis conformational change of 1,3-butadiene, and the simplest Diels-Alder reaction between ethylene and 1,3-butadiene. The calculated MERP and saddle points on the generalized force modified potential energy surface (G-FMPES) are compared with the corresponding quantities on an unmodified potential energy surface. Our study is performed using electronic structure calculations at the HF/6-31G** level as implemented in the AIMS-MOLPRO code. Our calculations suggest that the added compressive pressure lowers the energy of cis butadiene. The activation energy barrier for the concerted Diels-Alder reaction is found to decrease progressively with increasing compressive pressure.

  1. Magnetically Separable Iron Oxide Nanoparticles: An Efficient and Reusable Catalyst for Imino Diels-Alder Reaction

    Energy Technology Data Exchange (ETDEWEB)

    Basavegowda, Nagaraj; Mishra, Kanchan; Lee, Yong Rok; Joh, Young-Gull [Yeungnam University, Gyeongsan (Korea, Republic of)

    2016-02-15

    Iron oxide nanoparticles were synthesized using Saururus chinensis (S. chinensis) leaf extract as a reducing and stabilizing agent via ultrasonication. The size, morphology, crystallinity, elemental composition, weight loss, surface chemical state, and magnetic properties of the synthesized nanoparticles were investigated. The synthe-sized nanoparticles were used as an efficient and recyclable catalyst for the synthesis of a variety of 2-methyl-4-substituted-1,2,3,4-tetrahydroquinoline derivatives by the imino Diels-Alder reaction. After the reaction, the catalyst was recovered by an external magnetic field. The recovered catalyst was then reused in a subsequent reaction under identical conditions. The recycled iron oxide nanoparticles (IONPs) were reused five times with-out any significant loss of catalytic activity.

  2. Magnetically Separable Iron Oxide Nanoparticles: An Efficient and Reusable Catalyst for Imino Diels-Alder Reaction

    International Nuclear Information System (INIS)

    Basavegowda, Nagaraj; Mishra, Kanchan; Lee, Yong Rok; Joh, Young-Gull

    2016-01-01

    Iron oxide nanoparticles were synthesized using Saururus chinensis (S. chinensis) leaf extract as a reducing and stabilizing agent via ultrasonication. The size, morphology, crystallinity, elemental composition, weight loss, surface chemical state, and magnetic properties of the synthesized nanoparticles were investigated. The synthe-sized nanoparticles were used as an efficient and recyclable catalyst for the synthesis of a variety of 2-methyl-4-substituted-1,2,3,4-tetrahydroquinoline derivatives by the imino Diels-Alder reaction. After the reaction, the catalyst was recovered by an external magnetic field. The recovered catalyst was then reused in a subsequent reaction under identical conditions. The recycled iron oxide nanoparticles (IONPs) were reused five times with-out any significant loss of catalytic activity.

  3. Liquid-Crystalline Ionic Liquids as Ordered Reaction Media for the Diels-Alder Reaction.

    Science.gov (United States)

    Bruce, Duncan W; Gao, Yanan; Canongia Lopes, José Nuno; Shimizu, Karina; Slattery, John M

    2016-11-02

    Liquid-crystalline ionic liquids (LCILs) are ordered materials that have untapped potential to be used as reaction media for synthetic chemistry. This paper investigates the potential for the ordered structures of LCILs to influence the stereochemical outcome of the Diels-Alder reaction between cyclopentadiene and methyl acrylate. The ratio of endo- to exo-product from this reaction was monitored for a range of ionic liquids (ILs) and LCILs. Comparison of the endo:exo ratios in these reactions as a function of cation, anion and liquid crystallinity of the reaction media, allowed for the effects of liquid crystallinity to be distinguished from anion effects or cation alkyl chain length effects. These data strongly suggest that the proportion of exo-product increases as the reaction media is changed from an isotropic IL to a LCIL. A detailed molecular dynamics (MD) study suggests that this effect is related to different hydrogen bonding interactions between the reaction media and the exo- and endo-transition states in solvents with layered, smectic ordering compared to those that are isotropic. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Bio-orthogonal Fluorescent Labelling of Biopolymers through Inverse-Electron-Demand Diels-Alder Reactions.

    Science.gov (United States)

    Kozma, Eszter; Demeter, Orsolya; Kele, Péter

    2017-03-16

    Bio-orthogonal labelling schemes based on inverse-electron-demand Diels-Alder (IEDDA) cycloaddition have attracted much attention in chemical biology recently. The appealing features of this reaction, such as the fast reaction kinetics, fully bio-orthogonal nature and high selectivity, have helped chemical biologists gain deeper understanding of biochemical processes at the molecular level. Listing the components and discussing the possibilities and limitations of these reagents, we provide a recent snapshot of the field of IEDDA-based biomolecular manipulation with special focus on fluorescent modulation approaches through the use of bio-orthogonalized building blocks. At the end, we discuss challenges that need to be addressed for further developments in order to overcome recent limitations and to enable researchers to answer biomolecular questions in more detail. © 2017 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  5. Blue-Emitting Arylalkynyl Naphthalene Derivatives via a Hexadehydro-Diels-Alder Cascade Reaction.

    Science.gov (United States)

    Xu, Feng; Hershey, Kyle W; Holmes, Russell J; Hoye, Thomas R

    2016-10-05

    We describe here three alkynyl substituted naphthalenes that display promising luminescence characteristics. Each compound is easily and efficiently synthesized in three steps by capitalizing on the hexadehydro-Diels-Alder (HDDA) cycloisomerization reaction in which an intermediate benzyne is captured by tetraphenylcyclopentadienone, a classical trap for benzyne itself. These compounds luminesce in the deep blue when stimulated either optically (i.e., photoluminescence in both solution and solid films) or electrically [in a light-emitting diode (LED)]. The photophysical properties are relatively insensitive to the electronic nature of the substituents (H, OMe, CO 2 Me) that define these otherwise identical compounds. Overall, our observations suggest that the twisted nature of the five adjacent aryl groups serves to minimize the intermolecular interaction between core naphthalene units in different sample morphologies. These compounds represent promising leads for the identification of others of value as the emissive component of organic LEDs (OLEDs).

  6. Sn-PILC: A novel Efficient and Recyclable Catalyst for One-pot Three Component Povarov’s Inverse-electron-demand Hetero Diels-Alder Reaction for a Facile Synthesis of Tetrahydropyranoquinoline Derivatives under Neat Conditions

    Directory of Open Access Journals (Sweden)

    Megha Rai

    2016-07-01

    Full Text Available The Povarov’s inverse-electron-demand hetero Diels–Alder one-pot three components reaction of aromatic aldehyde, aromatic amine with DHF has been developed using Sn-PILC as a catalyst under a neat condition which may helpful to society to get pharmacologically more active compounds. In the present study a novel series of tetrahydroquinoline 4(a-f were synthesized and characterized by IR, 1HNMR, 13CNMR, Mass spectral analysis and elemental analysis. The synthetic details and characterization results are discussed. DOI: http://dx.doi.org/10.17807/orbital.v8i3.801

  7. The inverse electron demand Diels-Alder click reaction in radiochemistry.

    Science.gov (United States)

    Reiner, Thomas; Zeglis, Brian M

    2014-04-01

    The inverse electron-demand Diels-Alder (IEDDA) cycloaddition between 1,2,4,5-tetrazines and strained alkene dienophiles is an emergent variety of catalyst-free 'click' chemistry that has the potential to have a transformational impact on the synthesis and development of radiopharmaceuticals. The ligation is selective, rapid, high-yielding, clean, and bioorthogonal and, since its advent in 2008, has been employed in a wide variety of chemical settings. In radiochemistry, the reaction has proven particularly useful with (18)  F and has already been utilized to create a number of (18)  F-labeled agents, including the PARP1-targeting small molecule (18)  F-AZD2281, the αv β3 integrin-targeting peptide (18)  F-RGD, and the GLP-1-targeting peptide (18)  F-exendin. The inherent flexibility of the ligation has also been applied to the construction of radiometal-based probes, specifically the development of a modular strategy for the synthesis of radioimmunoconjugates that effectively eliminates variability in the construction of these agents. Further, the exceptional speed and biorthogonality of the reaction have made it especially promising in the realm of in vivo pretargeted imaging and therapy, and pretargeted imaging strategies based on the isotopes (111) In, (18)  F, and (64) Cu have already proven capable of producing images with high tumor contrast and low levels of uptake in background, nontarget organs. Ultimately, the characteristics of inverse electron-demand Diels-Alder click chemistry make it almost uniquely well-suited for radiochemistry, and although the field is young, this ligation has the potential to make a tremendous impact on the synthesis, development, and study of novel radiopharmaceuticals. Copyright © 2013 John Wiley & Sons, Ltd.

  8. Asymmetric NHC-catalyzed aza-Diels-Alder reactions: Highly enantioselective route to α-amino acid derivatives and DFT calculations

    KAUST Repository

    Yang, Limin; Wang, Fei; Lee, Richmond; Lv, Yunbo; Huang, Kuo-Wei; Zhong, Guofu

    2014-01-01

    A facile N-heterocyclic carbene catalytic enantioselective aza-Diels-Alder reaction of oxodiazenes with α-chloroaldehydes as dienophile precursors is reported, with excellent enantioselectivity (ee > 99%) and excellent yield (up to 93%). DFT study

  9. Regio-, Diastereo-, and Enantioselective Nitroso-Diels-Alder Reaction of 1,3-Diene-1-carbamates Catalyzed by Chiral Phosphoric Acids.

    Science.gov (United States)

    Pous, Jonathan; Courant, Thibaut; Bernadat, Guillaume; Iorga, Bogdan I; Blanchard, Florent; Masson, Géraldine

    2015-09-23

    Chiral phosphoric acid-catalyzed asymmetric nitroso-Diels-Alder reaction of nitrosoarenes with carbamate-dienes afforded cis-3,6-disubstituted dihydro-1,2-oxazines in high yields with excellent regio-, diastereo-, and enantioselectivities. Interestingly, we observed that the catalyst is able not only to control the enantioselectivity but also to reverse the regioselectivity of the noncatalyzed nitroso-Diels-Alder reaction. The regiochemistry reversal and asynchronous concerted mechanism were confirmed by DFT calculations.

  10. Continuous-flow retro-Diels-Alder reaction: an efficient method for the preparation of pyrimidinone derivatives.

    Science.gov (United States)

    Nekkaa, Imane; Palkó, Márta; Mándity, István M; Fülöp, Ferenc

    2018-01-01

    The syntheses of various pyrimidinones as potentially bioactive products by means of the highly controlled continuous-flow retro-Diels-Alder reaction of condensed pyrimidinone derivatives are presented. Noteworthy, the use of this approach allowed us to rapidly screen a selection of conditions and quickly confirm the viability of preparing the desired pyrimidinones in short reaction times. Yields typically higher than those published earlier using conventional batch or microwave processes were achieved.

  11. Intramolecular anionic diels-alder reactions of 1-aryl-4-oxahepta-1,6-diyne systems in DMSO.

    Science.gov (United States)

    Kudoh, Takayuki; Mori, Tomoko; Shirahama, Mitsuhito; Yamada, Masashi; Ishikawa, Teruhiko; Saito, Seiki; Kobayashi, Hisayoshi

    2007-04-25

    Base-promoted cycloaddition reactions of 1-aryl- or 1-aryl-7-substituted-4-oxahepta-1,6-diyne systems in DMSO have proven to involve an anionic intramolecular Diels-Alder process taking place even at room temperature in spite of the reaction suffering from temporary disruption of aromaticity. Although initially formed alpha-arylallenide anion can be protonated by DMSO, it can be back to the allenide anion probably because of a small acidity difference between alpha-arylallene and DMSO. The alpha-arylallenide anion in combination with the alpha-aryl substituent can constitute an anionic diene structure that undergoes the intramolecular Diels-Alder reaction involving the C(6)-yne part, a very fast process probably because of the increased HOMO-1 level of the anionic diene, as shown by DFT calculations. Diversified substituted naphthalenes, benzofurans, phenanthrenes, and quinolines, including biaryl architectures, are available from 4-oxahepta-1,6-diynes in a highly expeditious way.

  12. Inverse-Electron-Demand Diels-Alder Reactions: Principles and Applications.

    Science.gov (United States)

    Png, Zhuang Mao; Zeng, Huining; Ye, Qun; Xu, Jianwei

    2017-09-05

    Inverse-electron-demand Diels-Alder (iEDDA) reactions are an intriguing class of cycloaddition reactions that have attracted increasing attention for their application in bioorthogonal chemistry, the total synthesis of natural products, and materials science. In many cases, the application of the iEDDA reaction has been demonstrated as an innovative approach to achieve target structures. The theoretical aspects of this class of reactions are of particular interest for scientists as a means to understand the various factors, such as steric strain and electron density of the attached groups, that govern the reaction and thus to elucidate the reaction mechanism. This review aims to summarize both theoretical investigations and application-driven research work on the iEDDA reaction. First, the historical aspects and the theoretical basis of the reaction, especially recent advances in time-dependent density functional theory (TD-DFT) calculations, as well as catalysis strategies will be highlighted and discussed. Second, the applications of this novel reaction in the context of materials science, bioorthogonal chemistry, and total synthesis of natural products will be elaborated with selected recent examples. The challenges and opportunities of the iEDDA reaction will be highlighted to give more insight into its potential applications in many other research areas. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR). An easy entry to linear bicyclic scaffolds.

    Science.gov (United States)

    Miró, Javier; Sánchez-Roselló, María; Sanz, Álvaro; Rabasa, Fernando; Del Pozo, Carlos; Fustero, Santos

    2015-01-01

    A new tandem cross enyne metathesis (CEYM)-intramolecular Diels-Alder reaction (IMDAR) has been carried out. It involves conjugated ketones, esters or amides bearing a remote olefin and aromatic alkynes as the starting materials. The overall process enables the preparation of a small family of linear bicyclic scaffolds in a very simple manner with moderate to good levels of diastereoselectivity. This methodology constitutes one of the few examples that employ olefins differently than ethylene in tandem CEYM-IMDAR protocols.

  14. Design and synthesis of polycyclic sulfones via Diels-Alder reaction and ring-rearrangement metathesis as key steps.

    Science.gov (United States)

    Kotha, Sambasivarao; Gunta, Rama

    2015-01-01

    Here, we describe a new and simple synthetic strategy to various polycyclic sulfones via Diels-Alder reaction and ring-rearrangement metathesis (RRM) as the key steps. This approach delivers tri- and tetracyclic sulfones with six (n = 1), seven (n = 2) or eight-membered (n = 3) fused-ring systems containing trans-ring junctions unlike the conventional all cis-ring junctions generally obtained during the RRM sequence. Interestingly the starting materials used are simple and commercially available.

  15. C2-symmetric bisamidines: Chiral Brønsted bases catalysing the Diels-Alder reaction of anthrones

    Directory of Open Access Journals (Sweden)

    2008-08-01

    Full Text Available C2-symmetric bisamidines 8 have been tested as chiral Brønsted bases in the Diels-Alder reaction of anthrones and N-substituted maleimides. High yields of cycloadducts and significant asymmetric inductions up to 76% ee are accessible. The proposed mechanism involves proton transfer between anthrone and bisamidine, association of the resulting ions and finally a cycloaddition step stereoselectively controlled by the chiral ion pair.

  16. A 11-Steps Total Synthesis of Magellanine through a Gold(I)-Catalyzed Dehydro Diels-Alder Reaction.

    Science.gov (United States)

    McGee, Philippe; Bétournay, Geneviève; Barabé, Francis; Barriault, Louis

    2017-05-22

    We have developed an innovative strategy for the formation of angular carbocycles via a gold(I)-catalyzed dehydro Diels-Alder reaction. This transformation provides rapid access to a variety of complex angular cores in excellent diastereoselectivities and high yields. The usefulness of this Au I -catalyzed cycloaddition was further demonstrated by accomplishing a 11-steps total synthesis of (±)-magellanine. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Organoplatinum complex promoted the asymmetric endo stereochemically controlled Diels-Alder reaction between 3-diphenylphosphinofuran and diphenylvinylphosphine.

    Science.gov (United States)

    Liu, Fengli; Pullarkat, Sumod A; Tan, Kien-Wee; Li, Yongxin; Leung, Pak-Hing

    2009-12-07

    The organoplatinum complex containing ortho-metalated (R)-(1-(dimethylamino)ethyl)-naphthalene as the chiral auxiliary has been used efficiently to promote the asymmetric [4 + 2] Diels-Alder reaction between diphenylvinylphosphine and 3-diphenylphosphinofuran to generate two chelating diphosphine endocycloadducts in the ratio 17:1. The absolute configurations of the three newly generated stereocenters have been assigned by single-crystal X-ray analysis.

  18. Surface confined retro Diels-Alder reaction driven by the swelling of weak polyelectrolytes.

    Science.gov (United States)

    Lyu, Beier; Cha, Wenli; Mao, Tingting; Wu, Yuanzi; Qian, Hujun; Zhou, Yitian; Chen, Xiuli; Zhang, Shen; Liu, Lanying; Yang, Guang; Lu, Zhongyuan; Zhu, Qiang; Ma, Hongwei

    2015-03-25

    Recently, the type of reactions driven by mechanical force has increased significantly; however, the number of methods for activating those mechanochemical reactions stays relatively limited. Furthermore, in situ characterization of a reaction is usually hampered by the inherent properties of conventional methods. In this study, we report a new platform that utilizes mechanical force generated by the swelling of surface tethered weak polyelectrolytes. An initiator with Diels-Alder (DA) adduct structure was applied to prepare the polyelectrolyte-carboxylated poly(OEGMA-r-HEMA), so that the force could trigger the retro DA reaction. The reaction was monitored in real time by quartz crystal microbalance and confirmed with atomic force microscopy and X-ray photoelectron spectroscopy. Compared with the conventional heating method, the swelling-induced retro DA reaction proceeded rapidly with high conversion ratio and selectivity. A 23.61 kcal/mol theoretical energy barrier supported the practicability of this retro DA reaction being triggered mechanically at ambient temperature. During swelling, the tensile force was controllable and persistent. This unique feature imparts this mechanochemical platform the potential to "freeze" an intermediate state of a reaction for in situ spectroscopic observations, such as surface-enhanced Raman spectroscopy and frequency generation spectroscopy.

  19. Photoreactive polymer brushes for high-density patterned surface derivatization using a Diels-Alder photoclick reaction.

    Science.gov (United States)

    Arumugam, Selvanathan; Orski, Sara V; Locklin, Jason; Popik, Vladimir V

    2012-01-11

    Reactive polymer brushes grown on silicon oxide surfaces were derivatized with photoreactive 3-(hydroxymethyl)naphthalene-2-ol (NQMP) moieties. Upon 300 or 350 nm irradiation, NQMP efficiently produces o-naphthoquinone methide (oNQM), which in turn undergoes very rapid Diels-Alder addition to vinyl ether groups attached to a substrate, resulting in the covalent immobilization of the latter. Any unreacted oNQM groups rapidly add water to regenerate NQMP. High-resolution surface patterning is achieved by irradiating NQMP-derivatized surfaces using photolithographic methods. The Diels-Alder photoclick reaction is orthogonal to azide-alkyne click chemistry, enabling sequential photoclick/azide-click derivatizations to generate complex surface functionalities. © 2011 American Chemical Society

  20. Well-defined Polymethylene-Based Co/Terpolymers by Combining Anthracene/Maleimide Diels-Alder Reaction with Polyhomologation

    KAUST Repository

    Hadjichristidis, Nikolaos

    2015-05-26

    A novel strategy towards well-defined polymethylene-based co/terpolymers, by combining anthracene/maleimide Diels-Alder reaction with polyhomologation, is presented. For the synthesis of diblock copolymers the following approach was applied: a) synthesis of α-anthracene-ω-hydroxy- polymethylene by polyhomologation using tri (9-anthracene-methyl propyl ether) borane as initiator, b) synthesis of furan-protected-maleimide-terminated poly (ε-caprolactone) or polyethylene glycol and c). Diels-Alder reaction between the anthracene and maleimide-terminated polymers. In the case of triblock terpolymers the α-anthracene-ω-hydroxy-polymethylene was used as macroinitiator for the ring-opening polymerization of D, L-lactide to afford an anthracene-terminated PM-b-PLA copolymer, followed by Diels-Alder reaction with furan-protected maleimide-terminated poly (ε-caprolactone) or polyethylene glycol to give the triblock terpolymers. All intermediate and final products were characterized by SEC, 1H NMR, UV-VIS spectroscopy and DSC.

  1. An MM and QM Study of Biomimetic Catalysis of Diels-Alder Reactions Using Cyclodextrins

    Directory of Open Access Journals (Sweden)

    Wei Chen

    2018-01-01

    Full Text Available We performed a computational investigation of the mechanism by which cyclodextrins (CDs catalyze Diels-Alder reactions between 9-anthracenemethanol and N-cyclohexylmaleimide. Hydrogen bonds (Hbonds between N-cyclohexylmaleimide and the hydroxyl groups of cyclodextrins were suggested to play an important role in this catalytic process. However, our free energy calculations and molecular dynamics simulations showed that these Hbonds are not stable, and quantum mechanical calculations suggested that the reaction is not promoted by these Hbonds. The binding of 9-anthracenemethanol and N-cyclohexylmaleimide to cyclodextrins was the key to the catalytic process. Cyclodextrins act as a container to hold the two reactants in the cavity, pre-organize them for the reactions, and thus reduce the entropy penalty to the activation free energy. Dimethyl-β-CD was a better catalyst for this specific reaction than β-CD because of its stronger van der Waals interaction with the pre-organized reactants and its better performance in reducing the activation energy. This computational work sheds light on the mechanism of the catalytic reaction by cyclodextrins and introduces new perspectives of supramolecular catalysis.

  2. C-C bond formation in the intramolecular Diels-Alder reaction of triene amides.

    Science.gov (United States)

    Benallou, Abdelilah; El Alaoui El Abdallaoui, Habib; Garmes, Hocine

    2018-02-01

    The mechanism nature of the intramolecular Diels-Alder reaction has been performed; and thus, the changes of C-C bond forming/breaking along IRC are characterized in this study. Conceptual DFT analyses of the most favorable adduct fused/exo shows that the flux electronic will take place from diene to dienophile moiety. Moreover, ELF topological analysis based on the electron density predicts that C-C bond is formed by the coupling of two pseudoradical centers generated at the most significant atoms of the molecules. However, C2 vs C3, also C1 and C4 interaction comes mainly from the global electron density transfer which takes place along the reaction. Two- stage one-step is the proposed mechanism of this reaction, the first stage aims for the formation of C2-C3 σ bond while the second stage aims for C1-C4 σ bond formation. Interestingly, the observed asynchronicity of this IMDA reaction due principally to the asymmetric reorganization of electron density at the most attractive centers.

  3. Substituent Effects on Regioselectivity of the Diels-Alder Reactions: Reactions of 10-Allyl-1,8-dichloroanthracene with 2-Chloroacrylonitrile, 1-Cyanovinyl Acetate and Phenyl Vinyl Sulfone

    Directory of Open Access Journals (Sweden)

    Mujeeb A. Sultan

    2016-01-01

    Full Text Available Diels-Alder reaction of 10-allyl-1,8-dichloroanthracene (3 with 2-chloroacrylonitrile (4 and 1-cyanovinyl acetate (5 gives exclusively the ortho isomer while its reaction with phenyl vinyl sulfone (10 yields a mixture of two isomeric adducts with priority to ortho isomer. The reactions proceeded under microwave condition in xylene. Configurations of these isomers have been assigned with the help of NMR spectra. The results indicated that the steric effect is dominating toward the isomer regioselectivity in the Diels-Alder reaction of the present compounds.

  4. Mono- and polyadducts of C60 with anthracenes by Diels-Alder-reactions

    International Nuclear Information System (INIS)

    Duarte-Ruiz, A.

    2000-09-01

    This work describes the synthesis and characterization of seven new mono-adducts of 9-methylanthracene, 9,10-dimethylanthracene, 9-bromoanthracene. 2,3,6,7-tetramethylanthracene, 1-methylanthracene, 2,6-di-tert-butylanthracen, as well as 2-methylanthracene to fullerene C60 in solution at r.t. by means of [4+2] Diels-Alder reactions. It could be shown that the mono-adducts with 9-methylanthracene, 9,10-dimethylanthracene, and 1-methylanthracene form the corresponding antipodal bis-adduct 'trans-1' on heating the solid to 180 o C. Furthermore the functionalization of fullerene C60 anthracene mono-adduct (C60C14H10) with anthracene through [4+2] Diels-Alder reactions was investigated which made it possible to separate and to characterize the five possible bis-adducts ('trans-1', 'trans-2', 'trans-3', 'trans-4', and 'e') that can form when the second anthracene adds either 'trans' to the opposite hemisphere (compared to the first addition of anthracene) or to an equatorial position. An exact identification of the bis-adducts 'trans-2' and 'trans-4' could only be acquired with spectroscopic methods, fortunately the bis-adducts 'trans-4', 'trans-3', and 'e' could also be examined by x-ray, thus all five could be fully characterized. No bis-adducts on the same hemisphere ('cis') were found. UV/VIS-spectra of the bis-adducts opened up the possibility to identify other [4+2] Diels-Alder products in the future. It has been noticed that the eluation sequence of the bis-adducts ('trans-1' before 'trans-2' before 'trans-4' before 'trans-3' before 'e') doesn't strictly correlate with the dipole moments. Furthermore six new tris-adducts ('t4t4t2', 't3t3t3', 't3t3t4', 'et3t2', 'et3t4', and 'eee') and one tetra-adduct ('eeet3') were separated and characterized. The tris-adduct 't3t3t3' was additionally characterized by x-ray which showed that the crystal contains only one enatiomer. All bis- and tris-adducts form the antipodal bis-adduct 'trans-1' on heating to 180 o C for 10 min

  5. Artificial Metalloenzymes with the Neocarzinostatin Scaffold: Toward a Biocatalyst for the Diels-Alder Reaction.

    Science.gov (United States)

    Ghattas, Wadih; Cotchico-Alonso, Lur; Maréchal, Jean-Didier; Urvoas, Agathe; Rousseau, Maëva; Mahy, Jean-Pierre; Ricoux, Rémy

    2016-03-02

    A copper(II) cofactor coupled to a testosterone anchor, copper(II)-(5-(Piperazin-1-yl)-1,10-phenanthroline)testosterone-17-hemisuccinamide (10) was synthesized and associated with a neocarzinostatin variant, NCS-3.24 (KD =3 μm), thus generating a new artificial metalloenzyme by following a "Trojan horse" strategy. Interestingly, the artificial enzyme was able to efficiently catalyze the Diels-Alder cyclization reaction of cyclopentadiene (1) with 2-azachalcone (2). In comparison with what was observed with cofactor 10 alone, the artificial enzymes favored formation of the exo products (endo/exo ratios of 84:16 and 62:38, respectively, after 12 h). Molecular modeling studies assigned the synergy between the copper complex and the testosterone (KD =13 μm) moieties in the binding of 10 to good van der Waals complementarity. Moreover, by pushing the modeling exercise to its limits, we hypothesize on the molecular grounds that are responsible for the observed selectivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Preparation of strained axially chiral (1,5)naphthalenophanes by photo-dehydro-Diels-Alder reaction.

    Science.gov (United States)

    Wessig, Pablo; Matthes, Annika

    2011-03-02

    The preparation of 10 (1,5)naphthalenophanes (10a-j) by photo-dehydro-Diels-Alder (PDDA) reaction is described. Owing to hindered rotation around the biaryl axis, compounds 10 are axially chiral and the separation of enantiomers by chiral HPLC was demonstrated in three cases (10a,b,e). The absolute configuration of the isolated enantiomers could be unambiguously determined by comparison of calculated and measured circular dichroism (CD) spectra. Furthermore, we analyzed ring strain phenomena of (1,5)naphthalenophanes 10. Depending on the length of the linker units, one can distinguish three classes of naphthalenophanes. Compounds 10a-c are highly strained (E(STR) = 7-31 kcal/mol), and the strain is caused by small bond angles in the linker unit and deformation of the naphthalene moiety. Another type of strain is observed if the linker unit becomes relatively long (10g,h) originating from transannular interactions and is comparable with the well-known strain of medium sized rings. The naphthalenophanes 10d-f with a linker length of 10-14 atoms are only marginally strained. To clearly discriminate the different sources of strain, we defined two geometrical parameters (average central dihedral angle δ(C) and naphthalene thickness D(N)) and demonstrated that they are well-suited to indicate naphthalene deformation of our naphthalenophanes 10 as well as of ten model naphthalenophanes (I-X) with different linker lengths and linking positions.

  7. A Computational Experiment of the Endo versus Exo Preference in a Diels-Alder Reaction

    Science.gov (United States)

    Rowley, Christopher N.; Woo, Tom K.

    2009-01-01

    We have developed and tested a computational laboratory that investigates an endo versus exo Diels-Alder cycloaddition. This laboratory employed density functional theory (DFT) calculations to study the cycloaddition of N-phenylmaleimide to furan. The endo and exo stereoisomers of the product were distinguished by building the two isomers in a…

  8. Ground states of molecules. XLIX. MINDO/3 study of the retro-diels-alder reaction of cyclohexene

    International Nuclear Information System (INIS)

    Dewar, M.J.S.; Olivella, S.; Rzepa, H.S.

    1978-01-01

    The retro-Diels-Alder reaction of cyclohexene to form ethylene and butadiene has been studied, using MINDO/3. The transition state is predicted to be very unsymmetric, corresponding to weakening of one of the two breaking CC bonds. The calculated entropy of activation agrees well with experiment and the calculated secondary isotope effects for 4,4-dideuteriocyclohexene and 4,4,5,5-tetradeuteriocyclohexene are similar to those measured for an analogous reaction by Taagepera and Thornton. Discrepancies between the conclusions reached here and those from recent ab-initio calculations are discussed. 4 tables, 3 figures, 53 references

  9. Spectacular Rate Enhancement of the Diels-Alder Reaction at the Ionic Liquid/n-Hexane Interface.

    Science.gov (United States)

    Beniwal, Vijay; Manna, Arpan; Kumar, Anil

    2016-07-04

    The use of the ionic liquid/n-hexane interface as a new class of reaction medium for the Diels-Alder reaction gives large rate enhancements of the order of 10(6) to 10(8) times and high stereoselectivity, as compared to homogeneous media. The rate enhancement is attributed to the H-bonding abilities and polarities of the ionic liquids, whereas the hydrophobicity of ionic liquids was considered to be the factor in controlling stereoselectivity. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. A computational study of the Diels-Alder reactions between 2,3-dibromo-1,3-butadiene and maleic anhydride

    Science.gov (United States)

    Rivero, Uxía; Meuwly, Markus; Willitsch, Stefan

    2017-09-01

    The neutral and cationic Diels-Alder-type reactions between 2,3-dibromo-1,3-butadiene and maleic anhydride have been computationally explored as the first step of a combined experimental and theoretical study. Density functional theory calculations show that the neutral reaction is concerted while the cationic reaction can be either concerted or stepwise. Further isomerizations of the Diels-Alder products have been studied in order to predict possible fragmentation pathways in gas-phase experiments. Rice-Ramsperger-Kassel-Marcus (RRKM) calculations suggest that under single-collision experimental conditions the neutral product may reform the reactants and the cationic product will most likely eliminate CO2.

  11. Kinetic study of the Diels-Alder reaction of Li⁺@C₆₀ with cyclohexadiene: greatly increased reaction rate by encapsulated Li⁺.

    Science.gov (United States)

    Ueno, Hiroshi; Kawakami, Hiroki; Nakagawa, Koji; Okada, Hiroshi; Ikuma, Naohiko; Aoyagi, Shinobu; Kokubo, Ken; Matsuo, Yutaka; Oshima, Takumi

    2014-08-06

    We studied the kinetics of the Diels-Alder reaction of Li(+)-encapsulated [60]fullerene with 1,3-cyclohexadiene and characterized the obtained product, [Li(+)@C60(C6H8)](PF6(-)). Compared with empty C60, Li(+)@C60 reacted 2400-fold faster at 303 K, a rate enhancement that corresponds to lowering the activation energy by 24.2 kJ mol(-1). The enhanced Diels-Alder reaction rate was well explained by DFT calculation at the M06-2X/6-31G(d) level of theory considering the reactant complex with dispersion corrections. The calculated activation energies for empty C60 and Li(+)@C60 (65.2 and 43.6 kJ mol(-1), respectively) agreed fairly well with the experimentally obtained values (67.4 and 44.0 kJ mol(-1), respectively). According to the calculation, the lowering of the transition state energy by Li(+) encapsulation was associated with stabilization of the reactant complex (by 14.1 kJ mol(-1)) and the [4 + 2] product (by 5.9 kJ mol(-1)) through favorable frontier molecular orbital interactions. The encapsulated Li(+) ion catalyzed the Diels-Alder reaction by lowering the LUMO of Li(+)@C60. This is the first detailed report on the kinetics of a Diels-Alder reaction catalyzed by an encapsulated Lewis acid catalyst rather than one coordinated to a heteroatom in the dienophile.

  12. Insight into the informational-structure behavior of the Diels-Alder reaction of cyclopentadiene and maleic anhydride.

    Science.gov (United States)

    Molina-Espíritu, Moyocoyani; Esquivel, Rodolfo O; Kohout, Miroslav; Angulo, Juan Carlos; Dobado, José A; Dehesa, Jesús S; LópezRosa, Sheila; Soriano-Correa, Catalina

    2014-08-01

    The course of the Diels-Alder reactions of cyclopentadiene and maleic anhydride were studied. Two reaction paths were modelled: endo- and exo-selective paths. All structures within the transient region were characterized and analyzed by means of geometrical descriptors, physicochemical parameters and information-theoretical measures in order to observe the linkage between chemical behavior and the carriage of information. We have shown that the information-theoretical characterization of the chemical course of the reaction is in complete agreement with its phenomenological behavior in passing from reactants to products. In addition, we were able to detect the main differences between the two reaction mechanisms. This type of informational analysis serves to provide tools to help understand the chemical reactivity of the two simplest Diels-Alder reactions, which permits the establishment of a connection between the quantum changes that molecular systems exert along reaction coordinates and standard physicochemical phenomenology. In the present study, we have shown that every reaction stage has a family of subsequent structures that are characterized not solely by their phenomenological behavior but also by informational properties of their electronic density distribution (localizability, order, uniformity). Moreover, we were able to describe the main differences between endo-adduct and exo-adduct pathways. With the advent of new experimental techniques, it is in principle possible to observe the structural changes in the transient regions of chemical reactions. Indeed, through this work we have provided the theoretical concepts needed to unveil the concurrent processes associated with chemical reactions.

  13. Theoretical Study on Regioselectivity of the Diels-Alder Reaction between 1,8-Dichloroanthracene and Acrolein.

    Science.gov (United States)

    Sultan, Mujeeb A; Karama, Usama; Almansour, Abdulrahman I; Soliman, Saied M

    2016-09-23

    A theoretical study of the regioselectivity of the Diels-Alder reaction between 1,8-dichloroanthracene and acrolein is performed using DFT at the B3LYP/6-31G(d,p) level of theory. The FMO analysis, global and local reactivity indices confirmed the reported experimental results. Potential energy surface analysis showed that the cycloadditions (CAs) favor the formation of the anti product. These results are in good agreement with the reported results obtained experimentally where the anti is the major product.

  14. Theoretical Study on Regioselectivity of the Diels-Alder Reaction between 1,8-Dichloroanthracene and Acrolein

    Directory of Open Access Journals (Sweden)

    Mujeeb A. Sultan

    2016-09-01

    Full Text Available A theoretical study of the regioselectivity of the Diels-Alder reaction between 1,8-dichloroanthracene and acrolein is performed using DFT at the B3LYP/6-31G(d,p level of theory. The FMO analysis, global and local reactivity indices confirmed the reported experimental results. Potential energy surface analysis showed that the cycloadditions (CAs favor the formation of the anti product. These results are in good agreement with the reported results obtained experimentally where the anti is the major product.

  15. Nitroso Diels-Alder (NDA) Reaction as an Efficient Tool for the Functionalization of Diene-Containing Natural Products

    Science.gov (United States)

    Carosso, Serena; Miller, Marvin J.

    2014-01-01

    This review describes the use of nitroso Diels-Alder reactions for the functionalization of complex diene-containing natural products in order to generate libraries of compounds with potential biological activity. The application of this methodology to the structural modification of a series of natural products (thebaine, steroidal dienes, rapamycin, leucomycin, colchicine, isocolchicine and piperine) is discussed using relevant examples from the literature from 1973 onwards. The biological activity of the resulting compounds is also discussed. Additional comments are provided that evaluate the methodology as a useful tool in organic, bioorganic and medicinal chemistry. PMID:25119424

  16. A Catalyst-Enabled Diastereodivergent Aza-Diels-Alder Reaction: Complementarity of N-Heterocyclic Carbenes and Chiral Amines.

    Science.gov (United States)

    Rong, Zi-Qiang; Wang, Min; Chow, Chi Hao Eugene; Zhao, Yu

    2016-07-04

    Highly efficient and diastereodivergent aza-Diels-Alder reactions have been developed to access either diastereomeric series of benzofuran-fused δ-lactams and dihydropyridines in nearly perfect stereoselectivity (d.r. >20:1, >99 % ee for all examples). The complementarity of N-heterocyclic carbene and chiral amine as the catalyst was demonstrated for the first time, together with an excellent level of catalytic efficiency (1 mol % loading). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Synthesis of terephthalic acid via Diels-Alder reactions with ethylene and oxidized variants of 5-hydroxymethylfurfural

    Science.gov (United States)

    Pacheco, Joshua J.; Davis, Mark E.

    2014-01-01

    Terephthalic acid (PTA), a monomer in the synthesis of polyethylene terephthalate (PET), is obtained by the oxidation of petroleum-derived p-xylene. There is significant interest in the synthesis of renewable, biomass-derived PTA. Here, routes to PTA starting from oxidized products of 5-hydroxymethylfurfural (HMF) that can be produced from biomass are reported. These routes involve Diels-Alder reactions with ethylene and avoid the hydrogenation of HMF to 2,5-dimethylfuran. Oxidized derivatives of HMF are reacted with ethylene over solid Lewis acid catalysts that do not contain strong Brønsted acids to synthesize intermediates of PTA and its equally important diester, dimethyl terephthalate (DMT). The partially oxidized HMF, 5-(hydroxymethyl)furoic acid (HMFA), is reacted with high pressure ethylene over a pure-silica molecular sieve containing framework tin (Sn-Beta) to produce the Diels-Alder dehydration product, 4-(hydroxymethyl)benzoic acid (HMBA), with 31% selectivity at 61% HMFA conversion after 6 h at 190 °C. If HMFA is protected with methanol to form methyl 5-(methoxymethyl)furan-2-carboxylate (MMFC), MMFC can react with ethylene in the presence of Sn-Beta for 2 h to produce methyl 4-(methoxymethyl)benzenecarboxylate (MMBC) with 46% selectivity at 28% MMFC conversion or in the presence of a pure-silica molecular sieve containing framework zirconium (Zr-Beta) for 6 h to produce MMBC with 81% selectivity at 26% MMFC conversion. HMBA and MMBC can then be oxidized to produce PTA and DMT, respectively. When Lewis acid containing mesoporous silica (MCM-41) and amorphous silica, or Brønsted acid containing zeolites (Al-Beta), are used as catalysts, a significant decrease in selectivity/yield of the Diels-Alder dehydration product is observed. PMID:24912153

  18. An Inverse Electron Demand Azo-Diels-Alder Reaction of o-Quinone Methides and Imino Ethers: Synthesis of Benzocondensed 1,3-Oxazines.

    Science.gov (United States)

    Osipov, Dmitry V; Osyanin, Vitaly A; Khaysanova, Guzel' D; Masterova, Elvira R; Krasnikov, Pavel E; Klimochkin, Yuri N

    2018-04-20

    We have studied the reactions of o-quinone methide precursors with imino ethers. The reaction provides a versatile route to substituted 1,3-benzoxazines. The proposed reaction mechanism involves the generation of the o-quinone methide intermediates, imino-Diels-Alder reaction, and elimination. This cascade process is a rare example of the participation of imino ethers as dienophiles.

  19. Extraordinary Mechanism of the Diels-Alder Reaction: Investigation of Stereochemistry, Charge Transfer, Charge Polarization, and Biradicaloid Formation.

    Science.gov (United States)

    Sexton, Thomas; Kraka, Elfi; Cremer, Dieter

    2016-02-25

    The Diels-Alder reaction between 1,3-butadiene and ethene is investigated from far-out in the entrance channel to the very last step in the exit channel thus passing two bifurcation points and extending the range of the reaction valley studied with URVA (Unified Reaction Valley Approach) by 300% compared to previous studies. For the first time, the pre- and postchemical steps of the reaction are analyzed at the same level of theory as the actual chemical processes utilizing the path curvature and its decomposition into internal coordinate or curvilinear coordinate components. A first smaller charge transfer to the dienophile facilitates the rotation of gauche butadiene into its cis form. The actual chemical processes are initiated by a second larger charge transfer to the dienophile that facilitates pyramidalization of the reacting carbon centers, bond equalization, and biradicaloid formation of the reactants. The transition state is aromatically stabilized and moved by five path units into the entrance channel in line with the Hammond-Leffler postulate. The pseudorotation of the boat form into the halfchair of cyclohexene is analyzed. Predictions are made for the Diels-Alder reaction based on a 11-phase mechanism obtained by the URVA analysis.

  20. Lateral extension of π conjugation along the bay regions of bisanthene through a diels-alder cycloaddition reaction

    KAUST Repository

    Li, Jinling; Jiao, Chongjun; Huang, Kuo-Wei; Wu, Jishan

    2011-01-01

    Diels-Alder cycloaddition reactions at the bay regions of bisanthene (1) with dienophiles such as 1,4-naphthoquinone have been investigated. The products were submitted to nucleophilic addition followed by reductive aromatization reactions to afford the laterally extended bisanthene derivatives 2 and 3. Attempted synthesis of a larger expanded bisanthene 4 revealed an unexpected hydrogenation reaction at the last reductive aromatization step. Unusual Michael addition was observed on quinone 14, which was obtained by Diels-Alder reaction between 1 and 1,4-anthraquinone. Compounds 1-3 exhibited near-infrared (NIR) absorption and emission with high-to-moderate fluorescent quantum yields. Their structures and absorption spectra were studied by density function theory and non-planar twisted structures were calculated for 2 and 3. All compounds showed amphoteric redox behavior with multiple oxidation/reduction waves. Oxidative titration with SbCl 5 gave stable radical cations, and the process was followed by UV/Vis/NIR spectroscopic measurements. Their photostability was measured and correlated to their different geometries and electronic structures. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Lateral extension of π conjugation along the bay regions of bisanthene through a diels-alder cycloaddition reaction

    KAUST Repository

    Li, Jinling

    2011-11-14

    Diels-Alder cycloaddition reactions at the bay regions of bisanthene (1) with dienophiles such as 1,4-naphthoquinone have been investigated. The products were submitted to nucleophilic addition followed by reductive aromatization reactions to afford the laterally extended bisanthene derivatives 2 and 3. Attempted synthesis of a larger expanded bisanthene 4 revealed an unexpected hydrogenation reaction at the last reductive aromatization step. Unusual Michael addition was observed on quinone 14, which was obtained by Diels-Alder reaction between 1 and 1,4-anthraquinone. Compounds 1-3 exhibited near-infrared (NIR) absorption and emission with high-to-moderate fluorescent quantum yields. Their structures and absorption spectra were studied by density function theory and non-planar twisted structures were calculated for 2 and 3. All compounds showed amphoteric redox behavior with multiple oxidation/reduction waves. Oxidative titration with SbCl 5 gave stable radical cations, and the process was followed by UV/Vis/NIR spectroscopic measurements. Their photostability was measured and correlated to their different geometries and electronic structures. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Facile approach to prepare pH and redox-responsive nanogels via Diels-Alder click reaction

    Directory of Open Access Journals (Sweden)

    C. M. Q. Le

    2018-08-01

    Full Text Available A novel pH and redox responsive system of sub-100 nm nanogels was prepared by arm-first approach via Diels-Alder click reaction. First, well-defined poly(ethylene glycol-block-poly(styrene-alt-maleic anhydride (PEG-b-PSM was synthesized and subsequently functionalized with furfuryl amine, leading to the formation of the dual-functional block copolymer of PEG-b-PSMf. The furfuryl groups in the PSMf block were employed to incorporate a redox-responsive linkage and the carboxylic acid moieties generated through functionalization acted as a pH-responsive part. The Diels-Alder click reaction between a bismaleimide crosslinker and PEG-b-PSMf was conducted at 60 °C, affording star-like nanogel structures. Doxorubicin, a model anticancer drug, was loaded into to the core of the nanogels primarily by the ionic interaction with carboxylates of core blocks and a highest drug loading capacity of 38.1% was obtained. Furthermore, the in vitro profile showed a low release percentage (11.2% of DOX at PBS pH 7.4, whereas a burst release (62% at pH 5.0 in the presence of 10 mM glutathione, indicating the effective pH and redox responsive characteristic of the PEG-b-PSMf nanogels.

  3. Ti(Oi-Pr)4-promoted photoenolization Diels-Alder reaction to construct polycyclic rings and its synthetic applications.

    Science.gov (United States)

    Yang, Baochao; Lin, Kuaikuai; Shi, Yingbo; Gao, Shuanhu

    2017-09-20

    Stereoselective construction of polycyclic rings with all-carbon quaternary centers, and vicinal all-carbon quaternary stereocenters, remains a significant challenge in organic synthesis. These structures can be found in a wide range of polycyclic natural products and drug molecules. Here we report a Ti(Oi-Pr) 4 -promoted photoenolization/Diels-Alder (PEDA) reaction to construct hydroanthracenol and related polycyclic rings bearing all-carbon quaternary centers. This photolysis proceeds under mild conditions and generates a variety of photo-cycloaddition products in good reaction efficiency and stereoselectivity (48 examples), and has been successfully used in the construction of core skeleton of oncocalyxones, tetracycline and pleurotin. It also provides a reliable method for the late-stage modification of natural products bearing enone groups, such as steroids. The total synthesis of oncocalyxone B was successfully achieved using this PEDA approach.Anthracenols with multiple chiral centres are common motifs in natural products. Here, the authors show a highly stereoselective photoenolization/Diels-Alder methodology involving a key Lewis acid reagent enabling the efficient construction of a family of anthracenol derivatives with quaternary centers.

  4. Grafting methyl acrylic onto carbon fiber via Diels-Alder reaction for excellent mechanical and tribological properties of phenolic composites

    Science.gov (United States)

    Fei, Jie; Duan, Xiao; Luo, Lan; Zhang, Chao; Qi, Ying; Li, Hejun; Feng, Yongqiang; Huang, Jianfeng

    2018-03-01

    Carbon fibers (CFs) were grafted with methyl acrylic via Diels-Alder reaction at the different oil bath temperature effectively creating a carboxyl functionalized surface. The effect of grafting temperature on the surface morphology and functional groups of carbon fibers were investigated by FTIR, Raman spectroscopy, XPS and SEM respectively. The results showed that the optimal grafting temperature was 80 °C, and the relative surface coverage by carboxylic acid groups increased from an initial 5.16% up to 19.30% significantly improved the chemical activity without damaging the skin and core region of the carbon fibers. Mechanical property tests indicated that the shear and tensile strength of the sample with the grafting temperature of 80 °C (CFRP-3) increased obviously by 90.3% and 78.7%, respectively, compared with the pristine carbon fibers reinforced composite. Further, the sample CFRP-3 exhibited higher and more stable friction coefficient and improved wear resistance, while the wear rate decreased 52.7%, from 10.8 × 10-6 to 5.1 × 10-6 mm3/N m. The present work shows that grafting methyl acrylic via Diels-Alder reaction could be a highly efficient and facile method to functionalize carbon fibers for advanced composites.

  5. Illustrating the Utility of X-Ray Crystallography for Structure Elucidation through a Tandem Aldol Condensation/Diels-Alder Reaction Sequence

    Science.gov (United States)

    Hoang, Giang T.; Kubo, Tomohiro; Young, Victor G., Jr.; Kautzky, Jacob A.; Wissinger, Jane E.

    2015-01-01

    Two introductory organic chemistry laboratory experiments are described based on the Diels-Alder reaction of 2,3,4,5-tetraphenylcyclopentadienone, which is synthesized prior to or in a one-pot reaction, with styrene. Students are presented with three possible products, the "endo" and "exo" diastereomers and the decarbonylated…

  6. Thermodynamic and molecular origin of interfacial rate enhancements and endo-selectivities of a Diels-Alder reaction.

    Science.gov (United States)

    Beniwal, Vijay; Kumar, Anil

    2017-02-08

    Organic reactions in general display large rate accelerations when performed under interfacial conditions, such as on water or at ionic liquid interfaces. However, a clear picture of the physicochemical factors responsible for this large rate enhancements is not available. To gain an understanding of the thermodynamic and molecular origin of these large rate enhancements, we performed a Diels-Alder reaction between cyclopentadiene and methyl acrylate at ionic liquid/n-hexane interfaces. This study describes, for the first time, a methodology for the calculation of the activation parameters of an interfacial reaction. It has been seen that the energy of activation for an interfacial reaction is much smaller than that of the corresponding homogeneous reaction, resulting into the large rate acceleration for the interfacial reaction. Furthermore, the study describes the effects of the alkyl chain length of ionic liquid cations, the extent of heterogeneity, and the polarity of ionic liquids on the rate constants and stereoselectivity of the reaction.

  7. Integration of Computational and Preparative Techniques to Demonstrate Physical Organic Concepts in Synthetic Organic Chemistry: An Example Using Diels-Alder Reaction

    Science.gov (United States)

    Palmer, David R. J.

    2004-01-01

    The Diels-Alder reaction is used as an example for showing the integration of computational and preparative techniques, which help in demonstrating the physical organic concepts in synthetic organic chemistry. These experiments show that the students should not accept the computational results without questioning them and in many Diels-Alder…

  8. High Pressure Diels Alder Reactions of 1-Vinyl-2,2,6-trimethylcyclohexene Catalyzed by Chiral Lewis Acids; An Enantioselective Route to a Drimane Sesquiterpene Precursor.

    NARCIS (Netherlands)

    Knol, Joop; Meetsma, Auke; Feringa, Bernard

    1995-01-01

    The Diels Alder reaction of 1-vinyl-2,2,6-trimethylcyclohexene and 3-((E)-3-(methoxycarbonyl)propenoyl)-1,3-oxazolidin-2-one under high pressure, catalyzed by a chiral bis-imine copper(II) complex, yields a drimane sesquiterpene precursor in a highly regio- and diastereoselective manner with

  9. Synthesis of Precursors of the Agalacto (Exo) Fragment of the Quartromicins via an Auxiliary-Controlled Exo-Selective Diels-Alder Reaction

    Science.gov (United States)

    Qi, Jun; Roush, William R.

    2008-01-01

    A direct synthesis of the α-hydroxyaldehyde exo-5, a precursor of the exo-spirotetronate subunit o f the quartromicins, was achieved through an exo-selective Lewis acid-catalyzed Diels-Alder reaction of dienophile 12a and diene 1. PMID:16774259

  10. Novel UTP derivative with diene-containing spacer arm for Diels-Alder reaction: potential tool for radioactive or fluorescent detection upon its incorporation into ribonucleic acid

    Czech Academy of Sciences Publication Activity Database

    Točík, Zdeněk; Krásný, Libor; Kovačková, Soňa; Rejman, Dominik; Rosenberg, Ivan

    2007-01-01

    Roč. 6, č. 5 (2007), s. 357 ISSN 1535-3508. [International Conference of the European Society for Molecular Imaging /2./. 14.06.2007-15.06.2007, Naples] Institutional research plan: CEZ:AV0Z40550506; CEZ:AV0Z50520701 Keywords : UTP derivative * Diels - Alder reaction * diene * spacer arm Subject RIV: CC - Organic Chemistry

  11. Bicyclic Guanidine Catalyzed Asymmetric Tandem Isomerization Intramolecular-Diels-Alder Reaction: The First Catalytic Enantioselective Total Synthesis of (+)-alpha-Yohimbine.

    Science.gov (United States)

    Feng, Wei; Jiang, Danfeng; Kee, Choon-Wee; Liu, Hongjun; Tan, Choon-Hong

    2016-02-04

    Hydroisoquinoline derivatives were prepared in moderate to good enantioselectivities via a bicyclic guanidine-catalyzed tandem isomerization intramolecular-Diels-Alder (IMDA) reaction of alkynes. With this synthetic method, the first enantioselective synthesis of (+)-alpha-yohimbine was completed in 9 steps from the IMDA products. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Microwave- assisted solvent-free Diels-Alder reaction – a fast and simple route to various 5,6-substituted norbornenes and polychlorinated norbornenes

    Czech Academy of Sciences Publication Activity Database

    Dejmek, Milan; Hřebabecký, Hubert; Šála, Michal; Dračínský, Martin; Nencka, Radim

    -, č. 24 (2011), s. 4077-4083 ISSN 0039-7881 R&D Projects: GA MŠk 1M0508 Institutional research plan: CEZ:AV0Z40550506 Keywords : Diels - Alder reaction * polychlorinated norbornanes * norbornene Subject RIV: CC - Organic Chemistry Impact factor: 2.466, year: 2011

  13. Syntheses of the hexahydroindene cores of indanomycin and stawamycin by combinations of iridium-catalyzed asymmetric allylic alkylations and intramolecular Diels-Alder reactions.

    Science.gov (United States)

    Gärtner, Martin; Satyanarayana, Gedu; Förster, Sebastian; Helmchen, Günter

    2013-01-02

    Short and concise syntheses of the hexahydroindene cores of the antibiotics indanomycin (X-14547 A) and stawamycin are presented. Key methods used are an asymmetric iridium-catalyzed allylic alkylation, a modified Julia olefination, a Suzuki-Miyaura coupling, and an intramolecular Diels-Alder reaction. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Synthesis of a Self-Healing Polymer Based on Reversible Diels-Alder Reaction: An Advanced Undergraduate Laboratory at the Interface of Organic Chemistry and Materials Science

    Science.gov (United States)

    Weizman, Haim; Nielsen, Christian; Weizman, Or S.; Nemat-Nasser, Sia

    2011-01-01

    This laboratory experiment exposes students to the chemistry of self-healing polymers based on a Diels-Alder reaction. Students accomplish a multistep synthesis of a monomer building block and then polymerize it to form a cross-linked polymer. The healing capability of the polymer is verified by differential scanning calorimetry (DSC) experiments.…

  15. A Pyrene-Linked Cavity within a β-Barrel Protein Promotes an Asymmetric Diels-Alder Reaction.

    Science.gov (United States)

    Himiyama, Tomoki; Taniguchi, Naomasa; Kato, Shunsuke; Onoda, Akira; Hayashi, Takashi

    2017-10-23

    A unique π-expanded reaction cavity tethering a polycyclic moiety which provides a platform for substrate binding was constructed within the robust β-barrel structure of nitrobindin (NB). NB variants with cavities of different sizes and shapes are coupled with N-(1-pyrenyl)maleimide (Pyr) to prepare a series of NB-Pyr conjugates. The orientation of the pyrene moiety is fixed within the cavity by the coupling reaction. The fluorescent quenching analysis of NB-Pyr indicates that azachalcone (aza), which is a dienophile for a Diels-Alder (DA) reaction, is efficiently incorporated within the pyrene-linked reaction cavity by the aromatic interaction. The DA reaction between aza and cyclopentadiene proceeds within the reaction cavity of NB-Pyr in the presence of Cu II ion in high yield and high enantio- and regioselectivity. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Classical Example of Total Kinetic and Thermodynamic Control: The Diels-Alder Reaction between DMAD and Bis-furyl Dienes.

    Science.gov (United States)

    Borisova, Kseniya K; Kvyatkovskaya, Elizaveta A; Nikitina, Eugeniya V; Aysin, Rinat R; Novikov, Roman A; Zubkov, Fedor I

    2018-04-20

    A rare example of chemospecificity in the tandem Diels-Alder reaction of activated alkynes and bis-dienes has been revealed. The reaction between bis-furyl dienes and DMAD occurs at 25-80 °C and leads to kinetically controlled "pincer" adducts, 4a,8a-disubstituted 1,4:5,8-diepoxynaphthalenes. On the contrary, only thermodynamically controlled "domino" adducts (2,3-disubstituted 1,4:5,8-diepoxynaphthalenes) are formed in the same reaction at 140 °C. The "pincer" adducts can be transformed to the "domino" adducts at heating. The rate constants for reactions of both types were calculated using dynamic 1 H NMR spectroscopy.

  17. P-chiral 1-phosphanorbornenes: from asymmetric phospha-Diels-Alder reactions towards ligand design and functionalisation.

    Science.gov (United States)

    Möller, Tobias; Wonneberger, Peter; Sárosi, Menyhárt B; Coburger, Peter; Hey-Hawkins, Evamarie

    2016-02-07

    The principle of stereotopic face differentiation was successfully applied to 2H-phospholes which undergo a very efficient and highly stereoselective Diels-Alder reaction giving phosphorus-chiral 1-phosphanorbornenes with up to 87% yield. The observed reaction pathway has been supported by theoretical calculations showing that the cycloaddition reaction between 2H-phosphole 3a and the dienophile (5R)-(-)-menthyloxy-2(5H)-furanone (8) is of normal electron demand. Optically pure phosphanes were obtained by separation of the single diastereomers and subsequent desulfurisation of the sulfur-protected phosphorus atom. Finally, divergent ligand synthesis is feasible by reduction of the chiral auxiliary, subsequent stereospecific intramolecular Michael addition, and various functionalisations of the obtained key compound 13a. Furthermore, the unique structural properties of phospanorbornenes are presented and compared to those of phosphanorbornanes.

  18. Diels-Alder reactions for the rational design of benzo[b]thiophenes: DFT-based guidelines for synthetic chemists

    Science.gov (United States)

    Brasca, Romina; Kneeteman, María N.; Mancini, Pedro M. E.; Fabian, Walter M. F.

    2012-02-01

    In this work we studied the capability of several diene/dienophile pairs to undergo Diels-Alder (DA) reactions leading to benzo[b]thiophenes. A variety of synthetically and commercially available nitrothiophenes were chosen as dienophiles. Methyl 5-nitro-3-thiophenecarboxylate was selected as a potential strong electrophilic candidate based on some DFT-based properties and the substitution pattern of the expected product. The mechanistic details concerning the participation of this dienophile in polar DA reactions were investigated through a theoretical point of view. The results were compared with the experimental outcomes. This methodology should allow synthetic chemists to analyze DA reactions in detail in a stage prior to the synthetic job.

  19. Origins of the Unfavorable Activation and Reaction Energies of 1-Azadiene Heterocycles Compared to 2-Azadiene Heterocycles in Diels-Alder Reactions.

    Science.gov (United States)

    Fell, Jason S; Martin, Blanton N; Houk, K N

    2017-02-17

    The reactivities of butadiene, cyclopentadiene, furan, thiophene, pyrrole, and their 1-aza- and 2-aza-derivatives in Diels-Alder reactions with ethylene and fumaronitrile were investigated with density functional theory (M06-2X/6-311G(d,p)). The activation free energies for the Diels-Alder reactions of cyclic 1-azadienes are 10-14 kcal mol -1 higher than those of cyclic 2-azadienes, and the reaction free energies are 17-20 kcal mol -1 more endergonic. The distortion/interaction model shows that the increased activation energies of cyclic 1-azadienes originate from increased transition state distortion energies and unfavorable interaction energies, arising from addition to the nitrogen terminus of the C═N bond.

  20. Temperature-controlled cross-linking of silver nanoparticles with diels-alder reaction and its application on antibacterial property

    Science.gov (United States)

    Liu, Lian; Yang, Pengfei; Li, Junying; Zhang, Zhiliang; Yu, Xi; Lu, Ling

    2017-05-01

    Sliver nanoparticles (AgNPs) were synthesized and functionalized with furan group on their surface, followed by the reverse Diels-Alder (DA) reaction with bismaleimide to vary the particle size, so as to give different antibacterial activities. These nanoparticles were characterized using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Ultraviolet-Visible (UV-vis), Nanoparticle Size Analyzer and X-Ray Photoelectron Spectroscopy (XPS). It was found that the cross-linking reaction with bismaleimide had a great effect on the size of AgNPs. The size of the AgNPs could be controlled by the temperature of DA/r-DA equilibrium. The antibacterial activity was assessed using the inhibition zone diameter by introducing the particles into a media containing Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, respectively. It was found that these particles were effective bactericides. Furthermore, the antibacterial activity of the nanoparticles decreased orderly as the particle size enlarged.

  1. Highly Regio- and Stereoselective Diels-Alder Cycloadditions via Two-Step and Multicomponent Reactions Promoted by Infrared Irradiation under Solvent-Free Conditions

    Science.gov (United States)

    Flores-Conde, Maria Ines; Reyes, Leonor; Herrera, Rafael; Rios, Hulme; Vazquez, Miguel A.; Miranda, Rene; Tamariz, Joaquin; Delgado, Francisco

    2012-01-01

    Infrared irradiation promoted the Diels-Alder cycloadditions of exo-2-oxazolidinone dienes 1–3 with the Knoevenagel adducts 4–6, as dienophiles, leading to the synthesis of new 3,5-diphenyltetrahydrobenzo[d]oxazol-2-one derivatives (7, 9, 11 and 13–17), under solvent-free conditions. These cycloadditions were performed with good regio- and stereoselectivity, favoring the para-endo cycloadducts. We also evaluated the one-pot three-component reaction of active methylene compounds 20, benzaldehydes 21 and exo-2-oxazolidinone diene 2 under the same reaction conditions. A cascade Knoevenagel condensation/Diels-Alder cycloaddition reaction was observed, resulting in the final adducts 13–16 in similar yields. These procedures are environmentally benign, because no solvent and no catalyst were employed in these processes. The regioselectivity of these reactions was rationalized by Frontier Molecular Orbital (FMO) calculations. PMID:22489113

  2. Highly Regio- and Stereoselective Diels-Alder Cycloadditions via Two-Step and Multicomponent Reactions Promoted by Infrared Irradiation under Solvent-Free Conditions

    Directory of Open Access Journals (Sweden)

    Francisco Delgado

    2012-02-01

    Full Text Available Infrared irradiation promoted the Diels-Alder cycloadditions of exo-2-oxazolidinone dienes 1–3 with the Knoevenagel adducts 4–6, as dienophiles, leading to the synthesis of new 3,5-diphenyltetrahydrobenzo[d]oxazol-2-one derivatives (7, 9, 11 and 13–17, under solvent-free conditions. These cycloadditions were performed with good regio- and stereoselectivity, favoring the para-endo cycloadducts. We also evaluated the one-pot three-component reaction of active methylene compounds 20, benzaldehydes 21 and exo-2-oxazolidinone diene 2 under the same reaction conditions. A cascade Knoevenagel condensation/Diels-Alder cycloaddition reaction was observed, resulting in the final adducts 13–16 in similar yields. These procedures are environmentally benign, because no solvent and no catalyst were employed in these processes. The regioselectivity of these reactions was rationalized by Frontier Molecular Orbital (FMO calculations.

  3. Asymmetric Diels-Alder Reaction of α,β-Unsaturated Oxazolidin-2-one Derivatives Catalyzed by a Chiral Fe(III)-Bipyridine Diol Complex.

    Science.gov (United States)

    Li, Mao; Carreras, Virginie; Jalba, Angela; Ollevier, Thierry

    2018-02-16

    An asymmetric Fe III -bipyridine diol catalyzed Diels-Alder reaction of α,β-unsaturated oxazolidin-2-ones has been developed. Among various Fe II /Fe III salts, Fe(ClO 4 ) 3 ·6H 2 O was selected as the Lewis acid of choice. The use of a low catalyst loading (2 mol % of Fe(ClO 4 ) 3 ·6H 2 O and 2.4 mol % of Bolm's ligand) afforded high yields (up to 99%) and high enantiomeric excesses (up to 98%) of endo-cycloadducts for the Diels-Alder reaction between cyclopentadiene and substituted acryloyloxazolidin-2-ones. Other noncyclic dienes led to decreased enantioselectivities. A proposed model supports the observed stereoinduction.

  4. Asymmetric NHC-catalyzed aza-Diels-Alder reactions: Highly enantioselective route to α-amino acid derivatives and DFT calculations

    KAUST Repository

    Yang, Limin

    2014-08-01

    A facile N-heterocyclic carbene catalytic enantioselective aza-Diels-Alder reaction of oxodiazenes with α-chloroaldehydes as dienophile precursors is reported, with excellent enantioselectivity (ee > 99%) and excellent yield (up to 93%). DFT study showed that cis-TSa, formed from a top face approach of oxodiazene to cis-IIa, is the most favorable transition state and is consistent with the experimental observations. © 2014 American Chemical Society.

  5. Multiscale Treatment for the Molecular Mechanism of a Diels-Alder Reaction in Solution: A QM/MM-MD Study.

    Science.gov (United States)

    Soto-Delgado, Jorge; Tapia, Ricardo A; Torras, Juan

    2016-10-11

    Thermodynamics and the solvent role in the acceleration of the Diels-Alder reaction between cyclopentadiene (CPD) and methyl vinyl ketone (MVK) have been revisited. In this work we use an ab initio hybrid QM/MM-MD scheme combined with multiple steered molecular dynamics to extract the free energy pofile in water and methanol using the bidirectional Minh-Adib estimator. We obtain 18.7 kcal mol -1 and 20.8 kcal mol -1 free energy barrier for the reaction in water and methanol, respectively. This methodology reproduces experimental values with an absolute error of about 0.8 kcal mol -1 . The experimental difference between the activation free-energy barriers of water and methanol is also reproduced with an absolute error of about 0.1 kcal mol -1 . We explore the charge transfer evolution along reaction coordinates to characterize the electronic behavior for this reaction. It is shown that the solvent molecules around the reaction system produce a global polarization along the reaction coordinate which is consistent with the solvent polarity. The results highlight the role of hydrogen bonding formed in the transition state to stabilize the system charge reorganization in the reaction process.

  6. On the importance of hydrogen bonding in the promotion of Diels-Alder reactions of unactivated aldehydes: a computational study

    Science.gov (United States)

    Chemouri, Hafida; Mekelleche, Sidi Mohamed

    2014-03-01

    The kinetic solvent effects on the Diels-Alder (DA) reaction of N,N-dimethylamino-3-trimethylsilyl butadiene with p-anisaldehyde are studied by density functional calculations at the B3LYP/6-31C(d) level of theory. Experimentally, it has been found that the acceleration of this reaction is not due to the increase of the polarity of the solvent but it is rather due to hydrogen bonding (HB). Intrinsic reaction coordinate calculations combined with electron localisation function analysis show that this reaction follows a one-step two-stage mechanism with a highly asynchronous sigma bond formation process. The calculations, performed using an explicit solvent model based on the coordination of the carbonyl group with one molecule of the solvent, show a considerable decrease of the activation energy when going from the gas phase (ɛ = 1) to solution phase and this diminution is found to be more important in isopropyl alcohol (ɛ = 18.3) in comparison with acetonitrile (ɛ = 37.5). Our calculations also show that the acceleration of this DA reaction is due to the increase of the electrophilicity power of the solvated carbonyl compound and consequently the increase of the polarity of the reaction in the presence of protic solvents. The obtained results put in evidence the relevance of HB in the promotion of DA reactions of unactivated ketones as experimentally expected.

  7. Theoretical Study on the Aza-Diels-Alder Reaction Catalyzed by PHCl2 Lewis Acid via Pnicogen Bonding.

    Science.gov (United States)

    Yaghoobi, Fereshteh; Sohrabi Mahboub, Mahdi

    2018-03-15

    The reaction mechanism of the Aza-Diels-Alder (A-D-A) cycloaddition reaction between X 2 C═NNH 2 , where X = H, F, Cl, Br, and 1,3-butadiene catalyzed by a PHCl 2 Lewis acid was characterized using density functional theory calculations. The influences of various substituents of X on the studied reaction were analyzed using the activation strain model (ASM), which is also termed as the distortion-interaction model. Calculations showed that the smallest and largest values of the activation energies belong to the substituents of F and Br, respectively. The activation energy of the studied reactions was decreased within 8.6 kcal·mol -1 in the presence of PHCl 2 catalyst. Investigations showed that the pnicogen bonding is adequately capable of activating the A-D-A reaction. The quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis were implemented to understand the nature of C 4,Cbut ···C XIm and C 1,Cbut ···N XIm bonds at the TS structures. Additionally, the energy decomposition analysis (EDA) based on the ETS-NOCV scheme was used to characterize the nature of C 4,Cbut ···C XIm and C 1,Cbut ···N XIm bond. The results of the study mirror the fact that the PHCl 2 Lewis acid may be suggested as a simple suitable catalyst for experimental studies on the A-D-A reactions.

  8. Theoretical study on the Diels-Alder reaction of bromo-substituted 2H-pyrane-2-ones and some substituent vinyls

    Directory of Open Access Journals (Sweden)

    Haghdadi Mina

    2015-01-01

    Full Text Available A DFT study of the reactivity, regio- and stereoselectivity of Diels-Alder reaction between 3-bromo, 5-bromo, and 3,5-dibromo-2(H-pyran-2-ones and some weakly activated and unactivated alkenes has been carried out using density functional theory (DFT. Four possible reaction channels, which are related to the formation of meta- and para- and endo- and exo-cycloadducts have been explored and characterized. The energy and natural bond orbital analysis shows that the meta-regioselectivity on the exo pathway is preferred and follows an asynchronous concerted mechanism with a polar nature in all Diels-Alder cycloadditions. Moreover, the activation free energies of Diels-Alder cycloadditions of 3,5-dibromo-2(H-pyran-2one are lower than 3- bromo-2(H-pyran-2one and 5-bromo-2(H-pyran-2one, which are in line with experimental observation. DFT-based reactivity indices clearly predict the regiochemistry of the isolated cycloadducts.

  9. Exploring conditions for the enhancement of acene semiconductors through the use of the Diels-alder reaction

    Science.gov (United States)

    Qualizza, Brittni A.

    This dissertation demonstrates the application of SAMs to the surface of acene crystals, specifically of tetracene and rubrene, using the Diels-Alder reaction. The second chapter details preliminary reaction results and two analytical methods which were employed to confirm adsorption of the dienophile on the surface of single crystals, tetracene and rubrene. These were mass spectrometry and X-ray photoelectron spectroscopy (XPS). Mass spectrometry experiments distinguish the chemical identity of adduct on the crystals and also it discerned chemi- and physisorbed molecules from one another. XPS was used to prove face selectivity of the reaction by the detection of dichloromaleic anhydride. From a mechanistic standpoint, this system demonstrated unusual steric effects: the reaction of one face of the tetracene crystal was virtually inert, while another face was facile. The dienophiles' steric bulk was also expected to play critical role for these confined systems, however analysis of surface data was hindered by the relative lack of corresponding solution kinetic data. While the rate of anthracene's reaction has been studied extensively with a range of dienophiles and tetracene/pentacene has been studied theoretically (with limited experimental reports), an expansive report was generated to aid in future interpretations of acene systems. These kinetic results constitute chapter three.

  10. Microwave-assisted intramolecular dehydrogenative Diels-Alder reactions for the synthesis of functionalized naphthalenes/solvatochromic dyes.

    Science.gov (United States)

    Kocsis, Laura S; Benedetti, Erica; Brummond, Kay M

    2013-04-01

    Functionalized naphthalenes have applications in a variety of research fields ranging from the synthesis of natural or biologically active molecules to the preparation of new organic dyes. Although numerous strategies have been reported to access naphthalene scaffolds, many procedures still present limitations in terms of incorporating functionality, which in turn narrows the range of available substrates. The development of versatile methods for direct access to substituted naphthalenes is therefore highly desirable. The Diels-Alder (DA) cycloaddition reaction is a powerful and attractive method for the formation of saturated and unsaturated ring systems from readily available starting materials. A new microwave-assisted intramolecular dehydrogenative DA reaction of styrenyl derivatives described herein generates a variety of functionalized cyclopenta[b]naphthalenes that could not be prepared using existing synthetic methods. When compared to conventional heating, microwave irradiation accelerates reaction rates, enhances yields, and limits the formation of undesired byproducts. The utility of this protocol is further demonstrated by the conversion of a DA cycloadduct into a novel solvatochromic fluorescent dye via a Buchwald-Hartwig palladium-catalyzed cross-coupling reaction. Fluorescence spectroscopy, as an informative and sensitive analytical technique, plays a key role in research fields including environmental science, medicine, pharmacology, and cellular biology. Access to a variety of new organic fluorophores provided by the microwave-assisted dehydrogenative DA reaction allows for further advancement in these fields.

  11. The Diels-Alder cyclization of ketenimines.

    Science.gov (United States)

    Erb, Jeremy; Strull, Jessica; Miller, David; He, Jean; Lectka, Thomas

    2012-04-20

    A Diels-Alder reaction between cyclopentadiene and a variety of ketenimines is reported. A copper(I)-bis(phosphine complex catalyzes the cycloaddition across the C═N bond of the ketenimine in a [4 + 2] reaction to give an enamine intermediate that is hydrolyzed upon purification to generate aminoketones. © 2012 American Chemical Society

  12. Temperature-controlled cross-linking of silver nanoparticles with Diels-Alder reaction and its application on antibacterial property

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Lian; Yang, Pengfei, E-mail: ypf@qlu.edu.cn; Li, Junying; Zhang, Zhiliang; Yu, Xi; Lu, Ling

    2017-05-01

    Highlights: • Silver nanoparticles were functionalized by furan groups. • The DA reaction of furan with bismaleimide was used to cross-link the particles. • The reverse cross-linking could be controlled by temperature. • The antibacterial activity of silvers could be adjusted by the cross-linking. - Abstract: Sliver nanoparticles (AgNPs) were synthesized and functionalized with furan group on their surface, followed by the reverse Diels-Alder (DA) reaction with bismaleimide to vary the particle size, so as to give different antibacterial activities. These nanoparticles were characterized using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Ultraviolet-Visible (UV–vis), Nanoparticle Size Analyzer and X-Ray Photoelectron Spectroscopy (XPS). It was found that the cross-linking reaction with bismaleimide had a great effect on the size of AgNPs. The size of the AgNPs could be controlled by the temperature of DA/r-DA equilibrium. The antibacterial activity was assessed using the inhibition zone diameter by introducing the particles into a media containing Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, respectively. It was found that these particles were effective bactericides. Furthermore, the antibacterial activity of the nanoparticles decreased orderly as the particle size enlarged.

  13. Temperature-controlled cross-linking of silver nanoparticles with Diels-Alder reaction and its application on antibacterial property

    International Nuclear Information System (INIS)

    Liu, Lian; Yang, Pengfei; Li, Junying; Zhang, Zhiliang; Yu, Xi; Lu, Ling

    2017-01-01

    Highlights: • Silver nanoparticles were functionalized by furan groups. • The DA reaction of furan with bismaleimide was used to cross-link the particles. • The reverse cross-linking could be controlled by temperature. • The antibacterial activity of silvers could be adjusted by the cross-linking. - Abstract: Sliver nanoparticles (AgNPs) were synthesized and functionalized with furan group on their surface, followed by the reverse Diels-Alder (DA) reaction with bismaleimide to vary the particle size, so as to give different antibacterial activities. These nanoparticles were characterized using Scanning Electron Microscope (SEM), X-Ray Diffraction (XRD), Ultraviolet-Visible (UV–vis), Nanoparticle Size Analyzer and X-Ray Photoelectron Spectroscopy (XPS). It was found that the cross-linking reaction with bismaleimide had a great effect on the size of AgNPs. The size of the AgNPs could be controlled by the temperature of DA/r-DA equilibrium. The antibacterial activity was assessed using the inhibition zone diameter by introducing the particles into a media containing Escherichia coli, Listeria monocytogenes, and Staphylococcus aureus, respectively. It was found that these particles were effective bactericides. Furthermore, the antibacterial activity of the nanoparticles decreased orderly as the particle size enlarged.

  14. The role of achiral pyrazolidinone templates in enantioselective Diels-Alder reactions: scope, limitations, and conformational insights.

    Science.gov (United States)

    Sibi, Mukund P; Stanley, Levi M; Nie, Xiaoping; Venkatraman, Lakshmanan; Liu, Mei; Jasperse, Craig P

    2007-01-17

    We have evaluated the role of achiral pyrazolidinone templates in conjunction with chiral Lewis acids in room temperature, enantioselective Diels-Alder cycloadditions. The role of the fluxional N(1) substituent was examined, with the bulky 1-naphthylmethyl group providing enantioselectivities up to 99% ee, while templates with smaller fluxional groups gave lower selectivities. High selectivities were also observed in reactions of 7d with chiral Lewis acids derived from relatively small chiral ligands, suggesting the pyrazolidinone templates are capable of relaying stereochemical information from the ligand to the reaction center. Lewis acids capable of adapting square planar geometries, such as Cu(OTf)2, Cu(ClO4)2, and Pd(ClO4)2, were found to be particularly effective at providing high selectivities. Additionally, substitution at the C-5 position of the pyrazolidinone templates has been shown to be critical for optimal selectivity. Reactions of the optimal pyrazolidinone appended with a number of common dienophiles and various dienes demonstrate the utility of this achiral template. Furthermore, catalytic loadings could be lowered to 2.5 mol % with essentially no loss in selectivity. Pi-Pi interactions were evaluated as a means to explain the unusually high selectivity observed at room temperature. Finally, non-C2-symmetric ligands were employed as a test to determine if chiral relay was operative.

  15. Higher-order human telomeric G-quadruplex DNA metalloenzymes enhance enantioselectivity in the Diels-Alder reaction.

    Science.gov (United States)

    Li, Yinghao; Jia, Guoqing; Wang, Changhao; Cheng, Mingpan; Li, Can

    2015-03-02

    Short human telomeric (HT) DNA sequences form single G-quadruplex (G4 ) units and exhibit structure-based stereocontrol for a series of reactions. However, for more biologically relevant higher-order HT G4 -DNAs (beyond a single G4 unit), the catalytic performances are unknown. Here, we found that higher-order HT G4 -DNA copper metalloenzymes (two or three G4 units) afford remarkably higher enantioselectivity (>90 % ee) and a five- to sixfold rate increase, compared to a single G4 unit, for the Diels-Alder reaction. Electron paramagnetic resonance (EPR) and enzymatic kinetic studies revealed that the distinct catalytic function between single and higher-order G4 -DNA copper metalloenzymes can be attributed to different Cu(II) coordination environments and substrate specificity. Our finding suggests that, like protein enzymes and ribozymes, higher-order structural organization is crucial for G4 -DNA-based catalysis. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Highly efficient method for 125I-radiolabeling of biomolecules using inverse-electron-demand Diels-Alder reaction.

    Science.gov (United States)

    Choi, Mi Hee; Shim, Ha Eun; Yun, Seong-Jae; Kim, Hye Rim; Mushtaq, Sajid; Lee, Chang Heon; Park, Sang Hyun; Choi, Dae Seong; Lee, Dong-Eun; Byun, Eui-Baek; Jang, Beom-Su; Jeon, Jongho

    2016-04-19

    In this report, we present a rapid and highly efficient method for radioactive iodine labeling of trans-cyclooctene group conjugated biomolecules using inverse-electron-demand Diels-Alder reaction. Radioiodination reaction of the tetrazine structure was carried out using the stannylated precursor 2 to give 125 I-labeled azide ([ 125 I]1) with high radiochemical yield (65±8%) and radiochemical purity (>99%). For radiolabeling application of [ 125 I]1, trans-cyclooctene derived cRGD peptide and human serum albumin were prepared. These substrated were reacted with [ 125 I]1 under mild condition to provide the radiolabeled products [ 125 I]6 and [ 125 I]8, respectively, with excellent radiochemical yields. The biodistribution study of [ 125 I]8 in normal ICR mice showed significantly lower thyroid uptake values than that of 125 I-labeled human serum albumin prepared by a traditional radiolabeling method. Therefore [ 125 I]8 will be a useful radiolabeled tracer in various molecular imaging and biological studies. Those results clearly demonstrate that [ 125 I]1 will be used as a valuable prosthetic group for radiolabeling of biomolecules. Copyright © 2016 Elsevier Ltd. All rights reserved.

  17. Supramolecular hydrogel formation between chitosan and hydroxypropyl β-cyclodextrin via Diels-Alder reaction and its drug delivery.

    Science.gov (United States)

    Zhang, Mengke; Wang, Jinpeng; Jin, Zhengyu

    2018-07-15

    Chitosan-cyclodextrin hydrogel (CFCD) was prepared via Diels-Alder reaction between furfural functionalized chitosan (CF) and N-maleoyl alanine functionalized hydroxypropyl β-cyclodextrin (HPCD-AMI) in aqueous media without any catalyst or initiator. The CF and HPCD-AMI were confirmed by Fourier transform infrared spectroscopy and 1 H nuclear magnetic resonance spectroscopy. The resultant CFCD hydrogel was characterized in terms of thermal peripteries, microstructure, rheology behavior, and swelling capacity. The rheology analysis found that the storage modulus G' ranged from 1pa to 1200pa as the degree of furfural substitute on chitosan increased from 2.6% to 28.3%, indicating the hydrogel strength can be tuned readily by reaction stoichiometry. The swelling behaviors proved that CFCD hydrogel was pH-responsive with low swelling capacity, which would be preferable for drug delivery. Drug adsorption analysis showed the introduction of cyclodextrin into CFCD hydrogels promoted drug adsorption capacity. In addition, methyl orange cumulative release in PBS buffer was only 48.85% after 24h, suggesting CFCD hydrogel had good sustained release capacity on the loaded drug. Copyright © 2018 Elsevier B.V. All rights reserved.

  18. Click and Release: A Chemical Strategy toward Developing Gasotransmitter Prodrugs by Using an Intramolecular Diels-Alder Reaction.

    Science.gov (United States)

    Ji, Xingyue; Zhou, Cheng; Ji, Kaili; Aghoghovbia, Robert E; Pan, Zhixiang; Chittavong, Vayou; Ke, Bowen; Wang, Binghe

    2016-12-19

    Prodrug strategies have been proven to be a very effective way of addressing delivery problems. Much of the chemistry in prodrug development relies on the ability to mask an appropriate functional group, which can be removed under appropriate conditions. However, developing organic prodrugs of gasotransmitters represent unique challenges. This is especially true with carbon monoxide, which does not have an easy "handle" for bioreversible derivatization. By taking advantage of an intramolecular Diels-Alder reaction, we have developed a prodrug strategy for preparations of organic CO prodrugs that are stable during synthesis and storage, and yet readily release CO with tunable release rates under near physiological conditions. The effectiveness of the CO prodrug system in delivering a sufficient quantity of CO for possible therapeutic applications has been studied using a cell culture anti-inflammatory assay and a colitis animal model. These studies fully demonstrate the proof of concept, and lay a strong foundation for further medicinal chemistry work in developing organic CO prodrugs. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Computational Investigation of the Competition between the Concerted Diels-Alder Reaction and Formation of Diradicals in Reactions of Acrylonitrile with Non-Polar Dienes

    Science.gov (United States)

    James, Natalie C.; Um, Joann M.; Padias, Anne B.; Hall, H. K.; Houk, K. N.

    2013-01-01

    The energetics of the Diels-Alder cycloaddition reactions of several 1,3-dienes with acrylonitrile, and the energetics of formation of diradicals, were investigated with density functional theory (B3LYP and M06-2X) and compared to experimental data. For the reaction of 2,3-dimethyl-1,3-butadiene with acrylonitrile, the concerted reaction is favored over the diradical pathway by 2.5 kcal/mol using B3LYP/6-31G(d); experimentally this reaction gives both cycloadduct and copolymer. The concerted cycloaddition of cyclopentadiene with acrylonitrile is preferred computationally over the stepwise pathway by 5.9 kcal/mol; experimentally, only the Diels-Alder adduct is formed. For the reactions of (E)-1,3-pentadiene and acrylonitrile, both cycloaddition and copolymerization were observed experimentally; these trends were mimicked by the computational results, which showed only a 1.2 kcal/mol preference for the concerted pathway. For the reactions of (Z)-1,3-pentadiene and acrylonitrile, the stepwise pathway is preferred by 3.9 kcal/mol, in agreement with previous experimental findings that only polymerization occurs. M06-2X is known to give more accurate activation and reaction energetics but the energies of diradicals are too high. PMID:23758325

  20. Reactivity of Single-Walled Carbon Nanotubes in the Diels-Alder Cycloaddition Reaction: Distortion-Interaction Analysis along the Reaction Pathway.

    Science.gov (United States)

    Li, Yingzi; Osuna, Sílvia; Garcia-Borràs, Marc; Qi, Xiaotian; Liu, Song; Houk, Kendall N; Lan, Yu

    2016-08-26

    Diels-Alder cycloaddition is one of the most powerful tools for the functionalization of single-walled carbon nanotubes (SWCNTs). Density functional theory at the B3-LYP level of theory has been used to investigate the reactivity of different-diameter SWCNTs (4-9,5) in Diels-Alder reactions with 1,3-butadiene; the reactivity was found to decrease with increasing SWCNT diameter. Distortion/interaction analysis along the whole reaction pathway was found to be a better way to explore the reactivity of this type of reaction. The difference in interaction energy along the reaction pathway is larger than that of the corresponding distortion energy. However, the distortion energy plots for these reactions show the same trend. Therefore, the formation of the transition state can be determined from the interaction energy. A lower interaction energy leads to an earlier transition state, which indicates a lower activation energy. The computational results also indicate that the original distortion of the SWCNTs leads to an increase in the reactivity of the SWCNTs. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Syntheses of the Stemona Alkaloids (±)-Stenine, (±)-Neostenine, and (±)-13-Epineostenine Using a Stereodivergent Diels-Alder/Azido-Schmidt Reaction

    Science.gov (United States)

    Frankowski, Kevin J.; Golden, Jennifer E.; Zeng, Yibin; Lei, Yao; Aubé, Jeffrey

    2009-01-01

    A tandem Diels-Alder/azido Schmidt reaction sequence provides rapid access to the core skeleton shared by several Stemona alkaloids including stenine, neostenine, tuberstemonine, and neotubererostemonine. The discovery and evolution of inter- and intramolecular variations of this process and their applications to total syntheses of (±)–stenine and (±)–neostenine is described. The stereochemical outcome of the reaction depends on both substrate type and reaction condition, enabling the preparation of both (±)–stenine and (±)–neostenine from the same diene/dienophile combination. PMID:18396881

  2. [3+2] Cycloaddition of propargylic alcohols and α-oxo ketene dithioacetals: synthesis of functionalized cyclopentadienes and further application in a Diels-Alder reaction.

    Science.gov (United States)

    Fang, Zhongxue; Liu, Jianquan; Liu, Qun; Bi, Xihe

    2014-07-07

    Cyclopentadienes are valuable intermediates in organic synthesis and also ubiquitous as the Cp ligands in organometallic chemistry. As part of ongoing efforts to develop novel organic reactions that employ functionalized alkynes, a [3+2] cycloaddition of propargylic alcohols and ketene dithioacetals has been developed, which leads to fully substituted 2,5-dialkylthio cyclopentadienes in good to excellent yields. In an unusual dethiolating Diels-Alder reaction, the cyclopentadienes were further reacted with maleimides to afford a family of novel fluorescent polycyclic compounds. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Cross-conjugated Trienamine Catalysis with α'-Alkylidene 2-Cyclohexenones: Application in β,γ-Regioselective Aza-Diels-Alder Reaction.

    Science.gov (United States)

    Zhou, Zhi; Wang, Zhou-Xiang; Ouyang, Qin; Xiao, Wei; Du, Wei; Chen, Ying-Chun

    2017-02-24

    Endo-type cross-conjugated trienamines between highly congested α'-alkylidene 2-cyclohexenones and a chiral primary amine catalyst serve as HOMO-raised dienophiles in inverse-electron-demand aza-Diels-Alder cycloadditions with a number of 1-azadiene substrates. The reactions exhibit exclusive β,γ-regioselectivity, and multifunctional products with high molecular complexity are efficiently constructed in excellent diastereo- and enantioselectivity (>19:1 d.r., up to 99 % ee). © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Synthesis and Computational Studies Demonstrate the Utility of an Intramolecular Styryl Diels-Alder Reaction and Di-t-butylhydroxytoluene Assisted [1,3]-Shift to Construct Anticancer dl-Deoxypodophyllotoxin.

    Science.gov (United States)

    Saavedra, Diana I; Rencher, Benjamin D; Kwon, Doo-Hyun; Smith, Stacey J; Ess, Daniel H; Andrus, Merritt B

    2018-02-16

    Deoxypodophyllotoxin is a secondary metabolite lignan possessing potent anticancer activity with potential as a precursor for known anticancer drugs, but its use is limited by scarcity from natural sources. We here report the total synthesis of racemic deoxypodophyllotoxin in seven steps using an intramolecular styryl Diels-Alder reaction strategy uniquely suited to assemble the deoxypodophyllotoxin core. Density functional theory was used to analyze concerted, polar, and singlet-open-shell diradical reaction pathways, which identified a low-energy concerted [4 + 2] Diels-Alder pathway followed by a faster di-t-butylhydroxytoluene assisted [1,3]-formal hydrogen shift.

  5. Intramolecular didehydro-Diels-Alder reaction and its impact on the structure-function properties of environmentally sensitive fluorophores.

    Science.gov (United States)

    Brummond, Kay M; Kocsis, Laura S

    2015-08-18

    Reaction discovery plays a vital role in accessing new chemical entities and materials possessing important function.1 In this Account, we delineate our reaction discovery program regarding the [4 + 2] cycloaddition reaction of styrene-ynes. In particular, we highlight our studies that lead to the realization of the diverging reaction mechanisms of the intramolecular didehydro-Diels-Alder (IMDDA) reaction to afford dihydronaphthalene and naphthalene products. Formation of the former involves an intermolecular hydrogen atom abstraction and isomerization, whereas the latter is formed via an unexpected elimination of H2. Forming aromatic compounds by a unimolecular elimination of H2 offers an environmentally benign alternative to typical oxidation protocols. We also include in this Account ongoing work focused on expanding the scope of this reaction, mainly its application to the preparation of cyclopenta[b]naphthalenes. Finally, we showcase the synthetic utility of the IMDDA reaction by preparing novel environmentally sensitive fluorophores. The choice to follow this path was largely influenced by the impact this reaction could have on our understanding of the structure-function relationships of these molecular sensors by taking advantage of a de novo construction and functionalization of the aromatic portion of these compounds. We were also inspired by the fact that, despite the advances that have been made in the construction of small molecule fluorophores, access to rationally designed fluorescent probes or sensors possessing varied and tuned photophysical, spectral, and chemical properties are still needed. To this end, we report our studies to correlate fluorophore structure with photophysical property relationships for a series of solvatochromic PRODAN analogs and viscosity-sensitive cyanoacrylate analogs. The versatility of this de novo strategy for fluorophore synthesis was demonstrated by showing that a number of functional groups could be installed at

  6. On the effect of tether composition on cis/trans selectivity in intramolecular Diels-Alder reactions.

    Science.gov (United States)

    Paddon-Row, Michael N; Longshaw, Alistair I; Willis, Anthony C; Sherburn, Michael S

    2009-01-05

    Intramolecular Diels-Alder (IMDA) transition structures (TSs) and energies have been computed at the B3LYP/6-31+G(d) and CBS-QB3 levels of theory for a series of 1,3,8-nonatrienes, H(2)C=CH-CH=CH-CH(2)-X-Z-CH=CH(2) [-X-Z- = -CH(2)-CH(2)- (1); -O-C(=O)- (2); -CH(2)-C(=O)- (3); -O-CH(2)- (4); -NH-C(=O)- (5); -S-C(=O)- (6); -O-C(=S)- (7); -NH-C(=S)- (8); -S-C(=S)- (9)]. For each system studied (1-9), cis- and trans-TS isomers, corresponding, respectively, to endo- and exo-positioning of the -C-X-Z- tether with respect to the diene, have been located and their relative energies (E(rel) (TS)) employed to predict the cis/trans IMDA product ratio. Although the E(rel) (TS) values are modest (typically NH or S), the IMDA cis stereoselectivity diminishes. The predicted stereochemical reaction preferences are explained in terms of two opposing effects operating in the cis-TS, namely (1) unfavorable torsional (eclipsing) strain about the C4-C5 bond, that is caused by the -C-X-C(=Y)- group's strong tendency to maintain local planarity; and (2) attractive electrostatic and secondary orbital interactions between the endo-(thio)carbonyl group, C=Y, and the diene. The former interaction predominates when X is weakly electronegative (X=N, S), while the latter is dominant when X is more strongly electronegative (X=O), or a methylene group (X=CH(2)) which increases tether flexibility. These predictions hold up to experimental scrutiny, with synthetic IMDA reactions of 1, 2, 3, and 4 (published work) and 5, 6, and 8 (this work) delivering ratios close to those calculated. The reactions of thiolacrylate 5 and thioamide 8 represent the first examples of IMDA reactions with tethers of these types. Our results point to strategies for designing tethers, which lead to improved cis/trans-selectivities in IMDAs that are normally only weakly selective. Experimental verification of the validity of this claim comes in the form of fumaramide 14, which undergoes a more trans-selective IMDA reaction

  7. Regioselectivity of Sc2C2@C3v(8)-C82: Role of the Sumanene-Type Hexagon in Diels-Alder Reaction.

    Science.gov (United States)

    Zhao, Pei; Zhao, Xiang; Ehara, Masahiro

    2016-09-16

    Recently, several experiments have demonstrated high chemical reactivity of the sumanene-type hexagon in Sc2C2@C82. To further uncover its reactivity, the Diels-Alder reaction to all the nonequivalent C-C bonds of C82 and Sc2C2@C82 has been investigated by density functional theory calculations. For the free fullerene, the [5,6] bond 7 is the thermodynamically most favored, whereas the addition on the [6,6] bond 3 has the lowest activation energy. Diels-Alder reaction has no preference for addition sites in the sumanene-type hexagon. However, in the case of the endohedral fullerene, the [6,6] bond 19 in the special hexagon becomes the most reactive site according to both kinetic and thermodynamic considerations. Further analyses reveal that bond 19 in Sc2C2@C82 exhibits the shortest bond length and third largest π-orbital axis vector. In addition, the LUMOs of bond 19 are also symmetry-allowed to interact with butadiene.

  8. Synthesis of stimuli-responsive chitosan-based hydrogels by Diels-Alder cross-linking `click´ reaction as potential carriers for drug administration.

    Science.gov (United States)

    Guaresti, O; García-Astrain, C; Aguirresarobe, R H; Eceiza, A; Gabilondo, N

    2018-03-01

    Stimuli-responsive chitosan-based hydrogels for biomedical applications using the Diels-Alder reaction were prepared. Furan modified chitosan (Cs-Fu) was cross-linked with polyetheramine derived bismaleimide at different equivalent ratios in order to determine the effect in the swelling and release properties on the final CsFu:BMI hydrogels. The Diels Alder cross-linking reaction was monitored by UV-vis spectroscopy and rheological measurements. Both the sol-gel transition value and the final storage modulus for the different formulations were similar and close to 40 min and 400 Pa, respectively. On the contrary, the swelling degree was found to be strongly dependent on the amount of bismaleimide, mainly in acidic medium, where the increased cross-linking reduced the swelling value in 25%, but maintaining the sustained drug release in the simulated gastrointestinal environment. Our study suggested that these DA-cross-linked chitosan hydrogels could be potential carriers for targeted drug administration. Copyright © 2017 Elsevier Ltd. All rights reserved.

  9. Specific acid catalysis and Lewis acid catalysis of Diels-Alder reactions in aqueous media

    NARCIS (Netherlands)

    Mubofu, E.B.; Engberts, J.B.F.N.

    A comparative study of specific acid catalysis and Lewis acid catalysis of Diells-Alder reactions between dienophiles (1, 4 and 6) and cyclopentadiene (2) in water and mixed aqueous media is reported. The reactions were performed in water with copper(II) nitrate as the Lewis acid catalyst whereas

  10. C—C bond formation in the intramolecular Diels-Alder reaction of triene amides

    Directory of Open Access Journals (Sweden)

    Abdelilah Benallou

    2018-02-01

    Full Text Available The mechanism nature of the intramolecular Diels–Alder reaction has been performed; and thus, the changes of C—C bond forming/breaking along IRC are characterized in this study. Conceptual DFT analyses of the most favorable adduct fused/exo shows that the flux electronic will take place from diene to dienophile moiety. Moreover, ELF topological analysis based on the electron density predicts that C—C bond is formed by the coupling of two pseudoradical centers generated at the most significant atoms of the molecules. However, C2 vs C3, also C1 and C4 interaction comes mainly from the global electron density transfer which takes place along the reaction. Two- stage one-step is the proposed mechanism of this reaction, the first stage aims for the formation of C2—C3 σ bond while the second stage aims for C1—C4 σ bond formation. Interestingly, the observed asynchronicity of this IMDA reaction due principally to the asymmetric reorganization of electron density at the most attractive centers.

  11. Deeper Insight into the Diels-Alder Reaction through the Activation Strain Model

    NARCIS (Netherlands)

    Fernandez, Israel; Bickelhaupt, F. Matthias

    2016-01-01

    In this Focus Review, we present the application of the so-called Activation Strain Model of chemical reactivity to the Diels–Alder cycloaddition reaction. To this end, representative recent examples have been selected to illustrate the power of this new computational approach to gain a deeper

  12. Radioactive phosphorylation of alcohols to monitor biocatalytic Diels-Alder reactions.

    Directory of Open Access Journals (Sweden)

    Alexander Nierth

    Full Text Available Nature has efficiently adopted phosphorylation for numerous biological key processes, spanning from cell signaling to energy storage and transmission. For the bioorganic chemist the number of possible ways to attach a single phosphate for radioactive labeling is surprisingly small. Here we describe a very simple and fast one-pot synthesis to phosphorylate an alcohol with phosphoric acid using trichloroacetonitrile as activating agent. Using this procedure, we efficiently attached the radioactive phosphorus isotope (32P to an anthracene diene, which is a substrate for the Diels-Alderase ribozyme-an RNA sequence that catalyzes the eponymous reaction. We used the (32P-substrate for the measurement of RNA-catalyzed reaction kinetics of several dye-labeled ribozyme variants for which precise optical activity determination (UV/vis, fluorescence failed due to interference of the attached dyes. The reaction kinetics were analyzed by thin-layer chromatographic separation of the (32P-labeled reaction components and densitometric analysis of the substrate and product radioactivities, thereby allowing iterative optimization of the dye positions for future single-molecule studies. The phosphorylation strategy with trichloroacetonitrile may be applicable for labeling numerous other compounds that contain alcoholic hydroxyl groups.

  13. Deeper Insight into the Diels-Alder Reaction through the Activation Strain Model

    NARCIS (Netherlands)

    Fernandez, I.; Bickelhaupt, F.M.

    2016-01-01

    The Diels–Alder (DA) cycloaddition reaction has the ability to significantly increase molecular complexity regioselectively and stereospecifically in a single synthetic step. In this review it is discussed how the activation strain model of chemical reactivity reveals the physical factors that

  14. The Diels-Alder Cycloaddition Reaction of Substituted Hemifullerenes with 1,3-Butadiene: Effect of Electron-Donating and Electron-Withdrawing Substituents.

    Science.gov (United States)

    Mojica, Martha; Méndez, Francisco; Alonso, Julio A

    2016-02-12

    The Diels-Alder (DA) reaction provides an attractive route to increase the number of six member rings in substituted Polycyclic Aromatic Hydrocarbons (PAHs). The density functional theory (DFT) B3LYP method has been used in this work to inquire if the substitution of H over the edge of triindenetriphenylene (pristine hemifullerene 1) and pentacyclopentacorannulene (pristine hemifullerene 2), could improve the DA cycloaddition reaction with 1,3-butadiene. The substituents tested include electron-donating (NH₂, OMe, OH, Me, i-Pr) and electron-withdrawing groups (F, COOH, CF₃, CHO, CN, NO₂). The electronic, kinetic and thermodynamic parameters of the DA reactions of the substituted hemifullerenes with 1,3-butadiene have been analyzed. The most promising results were obtained for the NO₂ substituent; the activation energy barriers for reactions using this substituent were lower than the barriers for the pristine hemifullerenes. This leads us to expect that the cycloadditions to a starting fullerene fragment will be possible.

  15. The Brønsted Acid-Catalyzed, Enantioselective Aza-Diels-Alder Reaction for the Direct Synthesis of Chiral Piperidones.

    Science.gov (United States)

    Weilbeer, Claudia; Sickert, Marcel; Naumov, Sergei; Schneider, Christoph

    2017-01-12

    We disclose herein the first enantioselective aza-Diels-Alder reaction of β-alkyl-substituted vinylketene silyl-O,O-acetals and imines furnishing a broad range of optically highly enriched 4-alkyl-substituted 2-piperidones. As a catalyst for this one-pot reaction we employed a chiral phosphoric acid which effects a vinylogous Mannich reaction directly followed by ring-closure to the lactam. Subsequent fully diastereoselective transformations including hydrogenation, enolate alkylation, and lactam alkylation/reduction processes converted the cycloadducts into various highly substituted piperidines of great utility for the synthesis of natural products and medicinally active compounds. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Multifunctional Hydrogel with Good Structure Integrity, Self-Healing, and Tissue-Adhesive Property Formed by Combining Diels-Alder Click Reaction and Acylhydrazone Bond.

    Science.gov (United States)

    Yu, Feng; Cao, Xiaodong; Du, Jie; Wang, Gang; Chen, Xiaofeng

    2015-11-04

    Hydrogel, as a good cartilage tissue-engineered scaffold, not only has to possess robust mechanical property but also has to have an intrinsic self-healing property to integrate itself or the surrounding host cartilage. In this work a double cross-linked network (DN) was designed and prepared by combining Diels-Alder click reaction and acylhydrazone bond. The DA reaction maintained the hydrogel's structural integrity and mechanical strength in physiological environment, while the dynamic covalent acylhydrazone bond resulted in hydrogel's self-healing property and controlled the on-off switch of network cross-link density. At the same time, the aldehyde groups contained in hydrogel further promote good integration of the hydrogel to surrounding tissue based on aldehyde-amine Schiff-base reaction. This kind of hydrogel has good structural integrity, autonomous self-healing, and tissue-adhesive property and simultaneously will have a good application in tissue engineering and tissue repair field.

  17. Gold-catalyzed tandem hydroamination/formal aza-Diels-Alder reaction of homopropargyl amino esters: a combined computational and experimental mechanistic study.

    Science.gov (United States)

    Miró, Javier; Sánchez-Roselló, María; González, Javier; del Pozo, Carlos; Fustero, Santos

    2015-03-27

    A tandem gold-catalyzed hydroamination/formal aza-Diels-Alder reaction is described. This process, which employs quaternary homopropargyl amino ester substrates, leads to the formation of an intrincate tetracyclic framework and involves the generation of four bonds and five stereocenters in a highly diastereoselective manner. Theoretical calculations have allowed us to propose a suitable mechanistic rationalization for the tandem protocol. Additionally, by studying the influence of the ligands on the rate of the gold-catalyzed reactions, it was possible to establish optimum conditions in which to perform the process with a variety of substituents on the amino ester substrates. Notably, the asymmetric version of the tandem reaction was also evaluated. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Features of the Diels-Alder reaction between 9,10-diphenylanthracene and 4-phenyl-1,2,4-triazoline-3,5-dione

    Science.gov (United States)

    Kiselev, V. D.; Kornilov, D. A.; Kashaeva, E. A.; Potapova, L. N.; Krivolapov, D. B.; Litvinov, I. A.; Konovalov, A. I.

    2014-12-01

    The Diels-Alder reaction between substituted anthracenes 1a-1j and 4-phenyl-1,2,4-triazoline-3,5 ( 2) is studied. In all cases except one, the reaction proceeds on the most active 9,10-atoms of substituted anthracenes. The orthogonality of the two phenyl groups at the 9,10-position of diene 1a is found to shield 9,10-reactive centers. No dienophiles with C=C bonds are shown to participate in the Diels-Alder reaction with 1a; however, the reaction 1a + 2 proceeds with the very active dienophile 2,4-phenyl-1,2,4-triazoline-3,5-dione. It is shown that attachment occurs on the less active but sterically accessible 1,4-reactive center of diene 1a. The structure of adduct 3a is proved by 1H and 13C NMR spectroscopy and X-ray diffraction analysis. The following parameters are obtained for reaction 1a + 2 ⇆ 3a in toluene at 25°C: K eq = 2120 M-1, Δ Hf ≠ = 58.6 kJ/mol, Δ Sf ≠ = -97 J/(mol K), Δ Vf ≠ = -17.2 cm3/mol, Δ Hb ≠ = 108.8 kJ/mol, Δ Sb ≠ = 7.3 J/(mol K), Δ Vb ≠ = -0.8 cm3/mol, Δ H r-n = -50.2 kJ/mol, Δ S r-n = -104.3 J/(mol K), Δ V r-n = -15.6 cm3/mol. It is concluded that the values of equilibrium constants of the reactions 1a-1j + 2 ⇆ 3a-3j vary within 4 × 101-1011 M-1.

  19. Copper(I)-Catalyzed Asymmetric Desymmetrization through Inverse-Electron-Demand aza-Diels-Alder Reaction: Efficient Access to Tetrahydropyridazines Bearing a Unique α-Chiral Silane Moiety.

    Science.gov (United States)

    Wei, Liang; Zhou, Yu; Song, Zhi-Min; Tao, Hai-Yan; Lin, Zhenyang; Wang, Chun-Jiang

    2017-04-11

    An unprecedented copper(I)-catalyzed asymmetric desymmetrization of 5-silylcyclopentadienes with in situ formed azoalkene was realized through an inverse-electron-demand aza-Diels-Alder reaction (IEDDA) pathway, in which 5-silylcyclopentadienes served as efficient enophiles. This new protocol provides a facile access to the biologically important heterocyclic tetrahydropyridazines containing a unique α-chiral silane motif and three adjoining stereogenic centers in generally good yield (up to 92 %) with exclusive regioselectivity, high diastereoselectivity (>20:1 diastereomeric ratio), and excellent enantioselectivity (up to 98 % enantiomeric excess). DFT calculations and control experiments further confirmed the proposed reaction mechanism. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Prediction of the chemo- and regioselectivity of Diels-Alder reactions of o-benzoquinone derivatives with thiophenes by means of DFT-based reactivity indices

    Science.gov (United States)

    Ghomri, Amina; Mekelleche, Sidi Mohamed

    2014-03-01

    Global and local reactivity indices derived from density functional theory were used to elucidate the regio- and chemoselectivity of Diels-Alder reactions of masked o-benzoquinones with thiophenes acting as dienophiles. The polarity of the studied reactions is evaluated in terms of the difference of electrophilicity powers between the diene and dienophile partners. Preferential cyclisation modes of these cycloadditions are predicted using Domingo's polar model based on the local electrophilicity index, ωk, of the electrophile and the local nucleophilicity index, Nuk, of the nucleophile. The theoretical calculations, carried out at the B3LYP/6-311G(d,p) level of theory, are in good agreement with experimental findings.

  1. Diels-Alder reactions using 4,7-dioxygenated indanones as dienophiles for regioselective construction of oxygenated 2,3-dihydrobenz[f]indenone skeleton

    Directory of Open Access Journals (Sweden)

    2008-05-01

    Full Text Available Regioselective construction of 4,8,9-trioxygenated 2,3-dihydrobenz[f]indenones, key intermediates for the synthesis of kinamycin antibiotics, was achieved via Diels-Alder reactions (DAR using 4,7-dioxygenated indanone-type compounds as dienophiles. Reaction of indanetrione with 1-methoxybutadiene gave a 1 : 1 mixture of undesired 4,5,9-trioxygenated 2,3-dihydrobenz[f]indenone and [4.4.3]propellane. The addition of Lewis acid did not affect the product ratio, whereas the use of the 6-bromoindanetrione exclusively afforded the latter propellane. On the other hand, DAR of benzyne derived from bromoindan and furan gave 5,8-epoxy-2,3-dihydrobenz[f]indene, which was subjected to acid-induced ring opening to give 2,3-dihydrobenz[f]indenone with undesired 4,5,9-trioxy functions.

  2. Isolation and stereochemical assignment of phthalides resulting from the Diels-Alder reaction between 5-isopropoxyfuran-2(5H)-one and cyclopentadiene

    Science.gov (United States)

    Resende, G. C.; Alvarenga, E. S.; Willoughby, P. H.

    2015-12-01

    Naturally occurring phthalides and their synthetic analogs, feature a wide range of bioactivities. In our work, the Diels-Alder reaction between 5-isopropoxyfuran-2(5H)-one and cyclopentadiene was chosen as the key step to obtain tetrahydroisobenzofuran-1(3H)-one derivatives. The anti-endo (major), anti-exo and syn-endo adducts were isolated and structurally elucidated by nmr experiments. In order to rationalize the experimental finding, chemical shifts were predicted by theoretical calculations using density functional theory at B3LYP/6-31G(d,p) and B3LYP/6-311 + G(2d,p) levels. The goodness-of-fit between calculated and experimental data was evaluated by comparing mean absolute errors and applying DP4 probability methodology. Results demonstrated that DP4 probability of combined data (13C and 1H) is the most efficient method for assignment of the correct diastereoisomers.

  3. Site-Specific Protein Labeling Utilizing Lipoic Acid Ligase (LplA) and Bioorthogonal Inverse Electron Demand Diels-Alder Reaction.

    Science.gov (United States)

    Baalmann, Mathis; Best, Marcel; Wombacher, Richard

    2018-01-01

    Here, we describe a two-step protocol for selective protein labeling based on enzyme-mediated peptide labeling utilizing lipoic acid ligase (LplA) and bioorthogonal chemistry. The method can be applied to purified proteins, protein in cell lysates, as well as living cells. In a first step a W37V mutant of the lipoic acid ligase (LplA W37V ) from Escherichia coli is utilized to ligate a synthetic chemical handle site-specifically to a lysine residue in a 13 amino acid peptide motif-a short sequence that can be genetically expressed as a fusion with any protein of interest. In a second step, a molecular probe can be attached to the chemical handle in a bioorthogonal Diels-Alder reaction with inverse electron demand (DA inv ). This method is a complementary approach to protein labeling using genetic code expansion and circumvents larger protein tags while maintaining label specificity, providing experimental flexibility and straightforwardness.

  4. Synthesis and characterization of a novel double cross-linked hydrogel based on Diels-Alder click reaction and coordination bonding.

    Science.gov (United States)

    Li, Shubin; Wang, Lu; Yu, Xuemei; Wang, Chengli; Wang, Zhenyu

    2018-01-01

    Hydrogels, promising biological materials, need to have both strong mechanical properties and also inherent self-healing properties. In this work a double cross-linked network (DN) hydrogel was designed and prepared by combining a Diels-Alder click reaction and coordination effects. This DN hydrogel had good thermodynamic properties, anti-EDTA performance and self-healing properties. In addition, the mechanical properties, swelling properties and surface morphology of DN hydrogels can be controlled by adjusting the ratio of Fe 3+ -catechol. The adjustment of pH value can change the color, crosslinking mode and mechanical properties of the DN hydrogel. This smart hydrogel created from DA click chemistry and coordination effects has significance for guiding the design of new hydrogels with good mechanical properties, self-healing properties and controlled cross-link density. Copyright © 2017. Published by Elsevier B.V.

  5. Diels-Alder cyclo-addition as an efficient tool for linking π-donors onto fullerene C60

    International Nuclear Information System (INIS)

    Hudhomme, P.

    2006-01-01

    Diels-Alder reaction of endo-cyclic, acyclic 1,3-dienes or (hetero) o-quinodimethanes with the dienophilic fullerene C 60 is presented as an efficient tool for linking electro-active units giving rise to systems where both the donor and C 60 partners take up well defined volumes and orientations with respect to one another. While porphyrin is the most frequently used electron donor in artificial photosynthetic models, C 60 -based tetrathiafulvalene (TTF) or p-conjugated oligomer adducts remain interesting candidates for the preparation of photovoltaic devices. In this account, we focus on the use of the Diels-Alder cyclo-addition and its use in the synthesis of TTF-C 60 dyads, (TTF) n -C 60 polyads and C 60 -TTF-C 60 dumbbells as part of ongoing research into materials which display efficient photo-induced electron transfer. (author)

  6. Epoxy-Functionalized Porous Organic Polymers via the Diels-Alder Cycloaddition Reaction for Atmospheric Water Capture.

    Science.gov (United States)

    Byun, Yearin; Coskun, Ali

    2018-03-12

    The synthesis of highly microporous, epoxy-functionalized porous organic polymers (ep-POPs) by a one-pot, catalyst-free Diels-Alder cycloaddition polymerization is reported. The high oxygen content of ep-POPs offer efficient hydrogen-bonding sites for water molecules, thus leading to high water-uptake capacities up to 39.2-42.4 wt % under a wide temperature range of 5-45 °C, which covers the span of climatic conditions and manufacturing applications in which such materials might be used. Importantly, ep-POPs demonstrated regeneration temperatures as low as 55 °C, as well as excellent water stability, recyclability, and high specific surface areas up to 852 m 2  g -1 . © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Asymmetric Diels-Alder Reaction of α-Substituted and β,β-Disubstituted α,β-Enals via Diarylprolinol Silyl Ether for the Construction of All-Carbon Quaternary Stereocenters.

    Science.gov (United States)

    Hayashi, Yujiro; Bondzic, Bojan P; Yamazaki, Tatsuya; Gupta, Yogesh; Ogasawara, Shin; Taniguchi, Tohru; Monde, Kenji

    2016-10-24

    The asymmetric Diels-Alder reaction of α-substituted acrolein proceeds in the presence of the trifluoroacetic acid salt of trifluoromethyl-substituted diarylprolinol silyl ether to afford the exo-isomer with both excellent diastereoselectivity and high enantioselectivity. In the Diels-Alder reaction of a β,β-disubstituted α,β-unsaturated aldehyde, good exo-selectivity and excellent enantioselectivity was obtained when the perchloric acid salt of the bulky triisopropyl silyl ether of trifluoromethyl substituted diarylprolinol was employed as an organocatalyst in the presence of water. In both cases, all-carbon quaternary stereocenters are constructed enantioselectively. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Covalently crosslinked diels-alder polymer networks.

    Energy Technology Data Exchange (ETDEWEB)

    Bowman, Christopher (University of Colorado, Boulder, CO); Adzima, Brian J. (University of Colorado, Boulder, CO); Anderson, Benjamin John

    2011-09-01

    This project examines the utility of cycloaddition reactions for the synthesis of polymer networks. Cycloaddition reactions are desirable because they produce no unwanted side reactions or small molecules, allowing for the formation of high molecular weight species and glassy crosslinked networks. Both the Diels-Alder reaction and the copper-catalyzed azide-alkyne cycloaddition (CuAAC) were studied. Accomplishments include externally triggered healing of a thermoreversible covalent network via self-limited hysteresis heating, the creation of Diels-Alder based photoresists, and the successful photochemical catalysis of CuAAC as an alternative to the use of ascorbic acid for the generation of Cu(I) in click reactions. An analysis of the results reveals that these new methods offer the promise of efficiently creating robust, high molecular weight species and delicate three dimensional structures that incorporate chemical functionality in the patterned material. This work was performed under a Strategic Partnerships LDRD during FY10 and FY11 as part of a Sandia National Laboratories/University of Colorado-Boulder Excellence in Science and Engineering Fellowship awarded to Brian J. Adzima, a graduate student at UC-Boulder. Benjamin J. Anderson (Org. 1833) was the Sandia National Laboratories point-of-contact for this fellowship.

  9. Spiroketals of Pestalotiopsis fici provide evidence for a biosynthetic hypothesis involving diversified Diels-Alder reaction cascades.

    Science.gov (United States)

    Liu, Ling; Li, Yan; Li, Li; Cao, Ya; Guo, Liangdong; Liu, Gang; Che, Yongsheng

    2013-04-05

    Chloropestolides B-G (1-6), six new metabolites featuring the chlorinated spiro[benzo[d][1,3]dioxine-2,7'-bicyclo[2.2.2]octane]-4,8'-dione (1-3) and spiro[benzo[d][1,3]dioxine-2,1'-naphthalene]-2',4-dione (4-6) skeletons, and their putative biosynthetic precursor dechloromaldoxin (7) were isolated from the scale-up fermentation cultures of the plant endophytic fungus Pestalotiopsis fici . The structures of 1-7 were determined mainly by NMR experiments. The absolute configurations of 1-3 were deduced by analogy to the previously isolated metabolites from the same fungus (9 and 13-18), whereas those of 4, 5, and 7 were assigned by electronic circular dichroism (ECD) calculations. Structurally, the spiroketal skeletons found in 1-3 and 4-6 could be derived from 2,6-dihydroxy-4-methylbenzoic acid with chlorinated bicyclo[2.2.2]oct-2-en-5-one and 4a,5,8,8a-tetrahydronaphthalen-2(1H)-one, respectively. Biogenetically, compounds 1-6 were derived from the same Diels-Alder precursors as the previously isolated 9 and 12-18. In addition, compounds 2 and 3 were proposed as the biosynthetic intermediates of 17 and 16, respectively. Compound 1 was cytotoxic to three human tumor cell lines.

  10. Diels-Alder Reactions of 12-Hydroxy-9(10®20-5aH-abeo-abieta-1(10,8(9,12(13-triene-11,14-dione

    Directory of Open Access Journals (Sweden)

    Shougang Hu

    2013-06-01

    Full Text Available 12-Hydroxy-9(10®20-5aH-abeo-abieta-1(10,8(9,12(13-triene-11,14-dione (quinone 2 served as the dienophile in numerous intermolecular Diels-Alder reactions. These cycloadditions were conducted either thermally (including microwave heating or with Lewis acid activation. While most dienes reacted with quinone 2 in good chemical yield, others were incompatible under the experimental conditions used.

  11. Studies on the interactions of 5-R-3-(2-pyridyl)-1,2,4-triazines with arynes: inverse demand aza-Diels-Alder reaction versus aryne-mediated domino process.

    Science.gov (United States)

    Kopchuk, Dmitry S; Nikonov, Igor L; Khasanov, Albert F; Giri, Kousik; Santra, Sougata; Kovalev, Igor S; Nosova, Emiliya V; Gundala, Sravya; Venkatapuram, Padmavathi; Zyryanov, Grigory V; Majee, Adinath; Chupakhin, Oleg N

    2018-05-02

    The interactions between substituted 5-R-3-(pyridyl-2)-1,2,4-triazines with in situ generated substituted aryne intermediates have been studied. The reaction afforded either inverse demand (ID) aza-Diels-Alder products or 1,2,4-triazine ring rearrangement (domino) products as major ones depending on the nature of both the substituents at the C5 position of the 1,2,4-triazine core or in the aryne moiety. The structures of the key products were confirmed based on X-ray data. Based on the density functional theoretical (DFT) studies of the Diels-Alder transition state geometries, the influence of the nature of arynes on the direction of the 1,2,4-triazine transformation has been proposed.

  12. 1-acetylvinyl acrylates: new captodative olefins bearing an internal probe for the evaluation of the relative reactivity of captodative against electron-deficient double bonds in Diels-Alder and Friedel-Crafts reactions

    International Nuclear Information System (INIS)

    Herrera, Rafael; Universidad Michoacana de San Nicolas de Hidalgo, Morelia, Mich.; Jimenez-Vazquez, Hugo A.; Delgado, Francisco; Tamariz, Joaquin; Soederberg, Bjoern C.G.

    2005-01-01

    The captodative olefins 1-acetylvinyl esters of methacrylic and trans-crotonic acids, 3a and 3b, have been prepared. The presence of a second double bond in the molecule, acting as an internal probe, allowed us to compare their relative reactivity in Diels-Alder and Friedel-Crafts reactions. The reactivity was evaluated with cyclopentadiene (6) as diene in Diels-Alder cycloadditions, and with furan (9) and thiophene (10) as heteroaromatic Friedel-Crafts substrates. In both processes, the captodative enone double bond proved to be more reactive than that in the acrylic moiety. FMO theory accounted for this chemo selectivity as a consequence of the major π contribution of the enone to the LUMO of these molecules. The slight exo stereoselectivity observed in the cycloaddition to 6 parallels the higher stability of the corresponding transition state, according to the results of B3LYP/6-311G(d,p) calculations. (author)

  13. Niobium Pentachloride Activation of Enone Derivatives: Diels-Alder and Conjugate Addition Products

    Directory of Open Access Journals (Sweden)

    Gil Valdo José da Silva

    2002-05-01

    Full Text Available Niobium pentachloride has proven to be a powerful activating agent for Diels-Alder or conjugate addition reactions of cycloenones. The Diels-Alder product was obtained only with an unsubstituted enone (cyclohexenone and the highly reactive diene cyclopentadiene; substituents in the b-position of enones seem to prevent Diels-Alder reaction: oxygenated substituents favor the formation of vinyl chlorides (ethyl ether or dichloromethane as solvents or enol ethers (ethyl acetate as solvent, while a methyl substituent prevents any kind of transformation with NbCl5. Less reactive dienes, furan and 2-methylfuran gave the conjugate addition products of the furan ring to the enone system.

  14. Solvent effect on the degree of (a)synchronicity in polar Diels-Alder reactions from the perspective of the reaction force constant analysis.

    Science.gov (United States)

    Yepes, Diana; Martínez-Araya, Jorge I; Jaque, Pablo

    2017-12-29

    In this work, we computationally evaluated the influence of six different molecular solvents, described as a polarizable continuum model at the M06-2X/6-31+G(d,p) level, on the activation barrier/reaction rate, overall energy change, TS geometry, and degree of (a)synchronicity of two concerted Diels-Alder cycloadditions of acrolein (R1) and its complex with Lewis acid acrolein···BH 3 (R2) to cyclopentadiene. In gas-phase, we found that both exothermicity and activation barrier are only reduced by about 2.0 kcal mol -1 , and the asynchronicity character of the mechanism is accentuated when BH 3 is included. An increment in the solvent's polarity lowers the activation energy of R1 by 1.3 kcal mol -1 , while for R2 the reaction rate is enhanced by more than 2000 times at room temperature (i.e., the activation energy decreases by 4.5 kcal mol -1 ) if the highest polar media is employed. Therefore, a synergistic effect is achieved when both external agents, i.e., Lewis acid catalyst and polar solvent, are included together. This effect was ascribed to the ability of the solvent to favor the encounter between cyclopentadiene and acrolein···BH 3 . This was validated by the asymmetry of the TS which becomes highly pronounced when either both or just BH 3 is considered or the solvent's polarity is increased. Finally, the reaction force constant κ(ξ) reveals that an increment in the solvent's polarity is able to turn a moderate asynchronous mechanism of the formation of the new C-C σ-bonds into a highly asynchronous one. Graphical abstract A synergistic effect is achieved when both external agents, i.e., Lewis acid catalyst and polar solvent, are included together: lowered energy barriers and increased asynchronicities.

  15. Gold-Catalyzed Cyclization of Furan-Ynes bearing a Propargyl Carbonate Group: Intramolecular Diels-Alder Reaction with In Situ Generated Allenes.

    Science.gov (United States)

    Sun, Ning; Xie, Xin; Chen, Haoyi; Liu, Yuanhong

    2016-09-26

    Gold-catalyzed cyclization of various furan-ynes with a propargyl carbonate or ester moiety results in the formation of a series of polycyclic aromatic ring systems. The reactions can be rationalized through a tandem gold-catalyzed 3,3-rearrangement of the propargyl carboxylate moiety in furan-yne substrates to form an allenic intermediate, which is followed by an intramolecular Diels-Alder reaction of furan and subsequent ring-opening of the oxa-bridged cycloadduct. It was found that the steric and electronic properties of phosphine ligands on the gold catalyst had a significant impact on the reaction outcome. In the case of 1,5-furan-yne, the cleavage of the oxa-bridge in the cycloadduct with concomitant 1,2-migration of the R(1) group occurs to furnish anthracen-1(2H)-ones bearing a quaternary carbon center. For 1,4-furan-yne, a facile aromatization of the cycloadduct takes place to give 9-oxygenated anthracene derivatives. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Density functional theory studies on electronic properties of thiophene s oxides as aromatic dienophiles for reactivity prediction in diels-alder reactions

    International Nuclear Information System (INIS)

    Banjo, S.

    2013-01-01

    The reactivity of thiophene S-oxides was discussed with special emphasis on the use of thiophene S-oxides as dienophiles in Diels-Alder type reactions. The omega values obtained for thiophene S-oxide (TO) with electron-donating group (-CH/sub 3/) increased the nucleophilicity power whereas substitution with electron-withdrawing groups (such as -NO/sub 2/ and -CO/sub 2/CH/sub 2/CH/sub 3/) increased the electrophilicity power, indicating an increase of reactivity towards a nucleophiles. The higher the value of delta omega the more favourable the D-A process, therefore apart from (4+2) addition reactions of these TO as diene with the typical dienophiles like 1,2-dicyanoethene and 1,2-dicyanoethene, it could be possible for TO with strong electron withdrawing substituents to serve as dienophile, e.g. heterocycles Ie and If. Also, from the value of delta omega heterocycle 1d could involve in (4+2) addition reactions with heterocyles 1e and If. (author)

  17. A Near-Infrared Photothermal Effect-Responsive Drug Delivery System Based on Indocyanine Green and Doxorubicin-Loaded Polymeric Micelles Mediated by Reversible Diels-Alder Reaction.

    Science.gov (United States)

    Li, Hui; Li, Junjie; Ke, Wendong; Ge, Zhishen

    2015-10-01

    Near-infrared light (NIR) possesses great advantages for light-responsive controllable drug release, such as deep tissue penetration and low damage to healthy tissues. Herein, a NIR-responsive drug delivery system is developed based on a NIR dye, indocyanine green (ICG), and anticancer drug, doxorubicin (DOX)-loaded thermoresponsive block copolymer micelles, in which the drug release can be controlled via NIR irradiation. First, block copolymers, poly(oligo(ethylene glycol) methacrylate)-block-poly(furfuryl methacrylate) (POEGMA-b-PFMA), are synthesized by sequential reversible addition-fragmentation chain-transfer (RAFT) polymerization, followed by modification with N-octyl maleimide through Diels-Alder (DA) reaction to produce POEGMA-b-POMFMA. The self-assembly of POEGMA-b-POMFMA by nano-precipitation in aqueous solution affords the polymeric micelles which are used to simultaneously encapsulate ICG and DOX. Upon irradiation by NIR light (805 nm), the loaded DOX is released rapidly from the micelles due to partial retro DA reaction and local temperature increase-induced faster drug diffusion by the photothermal effect. Cytotoxicity evaluation and intracellular distribution observation demonstrate significant synergistic effects of NIR-triggered drug release, photothermal, and chemotherapy toward cancer cells under NIR irradiation. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Novel N-allyl/propargyl tetrahydroquinolines: Synthesis via Three-component Cationic Imino Diels-Alder Reaction, Binding Prediction, and Evaluation as Cholinesterase Inhibitors.

    Science.gov (United States)

    Rodríguez, Yeray A; Gutiérrez, Margarita; Ramírez, David; Alzate-Morales, Jans; Bernal, Cristian C; Güiza, Fausto M; Romero Bohórquez, Arnold R

    2016-10-01

    New N-allyl/propargyl 4-substituted 1,2,3,4-tetrahydroquinolines derivatives were efficiently synthesized using acid-catalyzed three components cationic imino Diels-Alder reaction (70-95%). All compounds were tested in vitro as dual acetylcholinesterase and butyryl-cholinesterase inhibitors and their potential binding modes, and affinity, were predicted by molecular docking and binding free energy calculations (∆G) respectively. The compound 4af (IC50 = 72 μm) presented the most effective inhibition against acetylcholinesterase despite its poor selectivity (SI = 2), while the best inhibitory activity on butyryl-cholinesterase was exhibited by compound 4ae (IC50 = 25.58 μm) with considerable selectivity (SI = 0.15). Molecular docking studies indicated that the most active compounds fit in the reported acetylcholinesterase and butyryl-cholinesterase active sites. Moreover, our computational data indicated a high correlation between the calculated ∆G and the experimental activity values in both targets. © 2016 The Authors Chemical Biology & Drug Design Published by John Wiley & Sons Ltd.

  19. Two-step protein labeling by using lipoic acid ligase with norbornene substrates and subsequent inverse-electron demand Diels-Alder reaction.

    Science.gov (United States)

    Best, Marcel; Degen, Anna; Baalmann, Mathis; Schmidt, Tobias T; Wombacher, Richard

    2015-05-26

    Inverse-electron-demand Diels-Alder cycloaddition (DAinv ) between strained alkenes and tetrazines is a highly bio-orthogonal reaction that has been applied in the specific labeling of biomolecules. In this work we present a two-step labeling protocol for the site-specific labeling of proteins based on attachment of a highly stable norbornene derivative to a specific peptide sequence by using a mutant of the enzyme lipoic acid ligase A (LplA(W37V) ), followed by the covalent attachment of tetrazine-modified fluorophores to the norbornene moiety through the bio-orthogonal DAinv  . We investigated 15 different norbornene derivatives for their selective enzymatic attachment to a 13-residue lipoic acid acceptor peptide (LAP) by using a standardized HPLC protocol. Finally, we used this two-step labeling strategy to label proteins in cell lysates in a site-specific manner and performed cell-surface labeling on living cells. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. In-depth evaluation of the cycloaddition-retro-Diels-Alder reaction for in vivo targeting with [111In]-DTPA-RGD conjugates

    International Nuclear Information System (INIS)

    Laverman, Peter; Meeuwissen, Silvie A.; Berkel, Sander S. van; Oyen, Wim J.G.; Delft, Floris L. van; Rutjes, Floris P.J.T.; Boerman, Otto C.

    2009-01-01

    Introduction: The spontaneous copper-free tandem 1,3-dipolar cycloaddition-retro-Diels-Alder (tandem crDA) reaction between cyclic Arg-Gly-Asp-D-Phe-Orn(N 3 ) [c(RGDfX)] and oxanorbornadiene-DTPA (o-DTPA) or methyloxanorbornadiene-DTPA (mo-DTPA) into two DTPA-c(RGDfX) regioisomers is characterized. Since there is no information on the stability and reaction rate of the tandem crDA reaction in biological media, we set out to characterize these reaction parameters. Methods: The effects of concentration of the reactants, temperature, pH and reaction environment (serum, blood) on the kinetics of the reaction were determined using 111 In-labeled oxanorbornadiene-DTPA analogs. The affinity of the radiolabeled conjugate was determined in a solid-phase α v β 3 integrin binding assay. Furthermore, the octanol-water partition coefficient was determined and, finally, the biodistribution of the labeled compounds in mice with subcutaneous α v β 3 -expressing tumors was determined. Results: Fifty percent conversion was reached after 26 h. Kinetic experiments furthermore established that the reaction rate of the tandem crDA reaction follows temperature- and concentration-dependent second-order kinetics, but is independent of the pH of the medium. Affinity of the two [ 111 In]DTPA-cRGDfX conjugates for α v β 3 integrin is 191 nM. Biodistribution studies showed specific (α v β 3 -mediated) uptake of [ 111 In]DTPA-c(RGDfX) in the tumor and in α v β 3 -expressing tissues. Conclusion: The tandem crDA reaction using methyl-substituted oxanorbornadiene is a versatile method for a single-step ligation that proceeds independently of pH and also proceeds in serum and blood. Currently, we are further looking into enhancement of reaction kinetics and exploitation of tandem crDA in vivo.

  1. Linear-dendritic supramolecular complexes as nanoscale reaction vessels for "green" chemistry. Diels-Alder reactions between fullerene C60 and polycyclic aromatic hydrocarbons in aqueous medium.

    Science.gov (United States)

    Simonyan, Arsen; Gitsov, Ivan

    2008-10-21

    This study describes the first Diels-Alder (DA) reaction performed in aqueous medium with highly hydrophobic compounds-fullerene (C 60) as the dienophile and anthracene (An) or tetracene (Tet) as the dienes, respectively. The reactions are performed in nanocontainers, constructed by self-assembly of linear-dendritic amphiphilic copolymers with poly(ethylene glycol), PEG or poly(ethylene oxide), PEO as the hydrophilic blocks and poly(benzyl ether) monodendrons as the hydrophobic fragments: G3PEO13k, dG3 and dG2. Comparative studies under identical conditions are carried out with an amphiphilic linear-linear copolymer, poly(styrene)1800- block-PEO2100, PSt-PEO, and the nonionic surfactant Igepal CO-720, IP720. The binding affinity of supermolecules built of these amphiphiles toward the DA reagents decreases in the following order: G3PEO13k > dG3 > PSt-PEO > dG2 > IP720. The kinetic constant of binding is evaluated for tetracene and decreases in a similar fashion: 5 x 10 (-7) M/min (G3PEO13k), through 4 x 10 (-7) M/min (PSt-PEO) down to 1.5 x 10 (-7) M/min for IP720. The mobility of substrates encapsulated in the micellar core, estimated by pyrene fluorescence decay, is 95-121 ns for the micelles of the linear-dendritic copolymers and notably higher for PSt-PEO (152 ns), revealing the much denser interior of the linear analogue. The apparent kinetic constant for the DA reaction of C 60 and Tet within the G3PEO13k supermolecule in aqueous medium is markedly higher than in organic solvent (toluene), 208 vs 1.82 M /min. With G3PEO13k the conversions reach 49% for the DA reaction between C 60 and An, and 55% for C 60 and Tet. Besides the monoadduct (26.5% yield) the reaction with An produces exclusively increasing amounts of D 2 h -symmetric antipodal bis-adduct, whose yield reaches up to 22.5% after 48 h. In addition to the environmentally friendly conditions notable advantages of the synthetic strategy described are the extended stability of the linear

  2. On the Reaction of 1,3-Diphenylisobenzofuran and (2-Iodoethynyl(phenyliodonium Triflate. A Unique Case of Oxygen Transfer from the Diels-Alder Adduct to the Diene

    Directory of Open Access Journals (Sweden)

    Mercè Font-Bardia

    2012-07-01

    Full Text Available Reaction of 1,3-diphenylisobenzofuran (DPIBF with 2-(iodoethynyl(phenyl-iodonium triflate at room temperature gave the expected Diels-Alder adduct, but using an excess of DFIBF (2 equiv. and performing the reaction at 55 °C or heating at this temperature during the concentration stage, the initial orange solution or product mixture became dark brown and the products 1,2-phenylene-1,2-bis(phenylmethanone and 2-(3-iodo-1,4-diphenylnaphthyl(phenyliodonium triflate were obtained, which suggests an oxygen transfer between DPIBF and the initial adduct.

  3. Insights into the Diels-Alder Reaction between 3-Vinylindoles and Methyleneindolinone without and with the Assistance of Hydrogen-Bonding Catalyst Bisthiourea: Mechanism, Origin of Stereoselectivity, and Role of Catalyst.

    Science.gov (United States)

    Yan, Chao-Xian; Yang, Fan; Yang, Xing; Zhou, Da-Gang; Zhou, Pan-Pan

    2017-03-17

    The Diels-Alder reaction between 3-vinylindoles and methyleneindolinone can proceed both under catalyst-free conditions and with bisthiourea as the catalyst. The reaction with bisthiourea is much faster and results in higher stereoselectivity of the product. The reaction mechanism, origin of stereoselectivity, and role of the catalyst were elaborated based on quantum mechanical calculations and theoretical methods of reactivity indices, NCI, QTAIM, and distortion/interaction models. In the uncatalyzed reaction, the two C-C bonds that are formed undergo conversion from noncovalent to covalent bonding via a concerted asynchronous mechanism. The weak intermolecular interactions formed in the transition state play important roles. The difference between the interaction and distortion energies is responsible for the stereoselectivity. In the catalyzed reaction, bisthiourea induces both the diene and dienophile to approach it via weak intermolecular interactions, which greatly lowers the energy barrier of the reaction and leads to the product with excellent stereoselectivity. The possible pathways of this reaction were explored, which suggested that the formation of the two C-C bonds goes through either a stepwise or concerted asynchronous mechanism. These results detail the reaction mechanism and shed light on both the significant role of the bisthiourea catalyst and the origin of stereoselectivity for this type of Diels-Alder reaction and related ones.

  4. In-depth evaluation of the cycloaddition-retro-Diels-Alder reaction for in vivo targeting with [{sup 111}In]-DTPA-RGD conjugates

    Energy Technology Data Exchange (ETDEWEB)

    Laverman, Peter [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands)], E-mail: p.laverman@nucmed.umcn.nl; Meeuwissen, Silvie A. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands); Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Berkel, Sander S. van [Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Oyen, Wim J.G. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands); Delft, Floris L. van; Rutjes, Floris P.J.T. [Institute for Molecules and Materials, Radboud University Nijmegen, 6500 GL Nijmegen (Netherlands); Boerman, Otto C. [Department of Nuclear Medicine, Radboud University Nijmegen Medical Centre, 6500 HB Nijmegen (Netherlands)

    2009-10-15

    Introduction: The spontaneous copper-free tandem 1,3-dipolar cycloaddition-retro-Diels-Alder (tandem crDA) reaction between cyclic Arg-Gly-Asp-D-Phe-Orn(N{sub 3}) [c(RGDfX)] and oxanorbornadiene-DTPA (o-DTPA) or methyloxanorbornadiene-DTPA (mo-DTPA) into two DTPA-c(RGDfX) regioisomers is characterized. Since there is no information on the stability and reaction rate of the tandem crDA reaction in biological media, we set out to characterize these reaction parameters. Methods: The effects of concentration of the reactants, temperature, pH and reaction environment (serum, blood) on the kinetics of the reaction were determined using {sup 111}In-labeled oxanorbornadiene-DTPA analogs. The affinity of the radiolabeled conjugate was determined in a solid-phase {alpha}{sub v}{beta}{sub 3} integrin binding assay. Furthermore, the octanol-water partition coefficient was determined and, finally, the biodistribution of the labeled compounds in mice with subcutaneous {alpha}{sub v}{beta}{sub 3}-expressing tumors was determined. Results: Fifty percent conversion was reached after 26 h. Kinetic experiments furthermore established that the reaction rate of the tandem crDA reaction follows temperature- and concentration-dependent second-order kinetics, but is independent of the pH of the medium. Affinity of the two [{sup 111}In]DTPA-cRGDfX conjugates for {alpha}{sub v}{beta}{sub 3} integrin is 191 nM. Biodistribution studies showed specific ({alpha}{sub v}{beta}{sub 3}-mediated) uptake of [{sup 111}In]DTPA-c(RGDfX) in the tumor and in {alpha}{sub v}{beta}{sub 3}-expressing tissues. Conclusion: The tandem crDA reaction using methyl-substituted oxanorbornadiene is a versatile method for a single-step ligation that proceeds independently of pH and also proceeds in serum and blood. Currently, we are further looking into enhancement of reaction kinetics and exploitation of tandem crDA in vivo.

  5. Enantioselective Diels-Alder Reaction Using Chiral Mg Complexes Derived from Chiral 2-[2-[(Alkyl- or 2-[2-[(Arylsulfonyl)amino]phenyl]-4-phenyl-1,3-oxazoline.

    Science.gov (United States)

    Ichiyanagi, Tsuyoshi; Shimizu, Makoto; Fujisawa, Tamotsu

    1997-11-14

    Magnesium complexes derived from (R)-2-[2-[(alkyl- or (R)-2-[2-[(arylsulfonyl)amino]phenyl]-4-phenyl-1,3-oxazolines and methylmagnesium iodide were found to be efficient Lewis acid catalysts for the Diels-Alder reaction of 3-alkenoyl-1,3-oxazolidin-2-one with cyclopentadiene. Chiral ligands were easily prepared from readily available D-phenylglycinol in good yields. The reaction of 3-acryloyl-1,3-oxazolidin-2-one with cyclopentadiene catalyzed by a stoichiometric amount of the Lewis acid gave exclusively the endo-cycloaddition product in up to 92% ee. The sulfonamide group on the chiral ligand strongly influenced the enantiofacial selectivity: the use of a toluene-, benzene-, 1- or 2-naphthalene-, or methanesulfonamide group in the chiral ligand gave the endo-(2R)-cycloaddition product, while a trifluoromethanesulfonamide group predominantly gave its enantiomer, the endo-(2S)-cycloaddition product, in 65% ee. The scope and limitations of the catalytic effect of chiral Mg(II) complexes on the enantioselectivity of the Diels-Alder reaction were investigated. The reaction mechanism of the Mg(II)-catalyzed reaction is also discussed on the basis of the experimental results.

  6. Quantum mechanical/molecular mechanical modeling finds Diels-Alder reactions are accelerated less on the surface of water than in water.

    Science.gov (United States)

    Thomas, Laura L; Tirado-Rives, Julian; Jorgensen, William L

    2010-03-10

    Quantum and molecular mechanics calculations for the Diels-Alder reactions of cyclopentadiene with 1,4-naphthoquinone, methyl vinyl ketone, and acrylonitrile have been carried out at the vacuum-water interface and in the gas phase. In conjunction with previous studies of these cycloadditions in dilute solution, a more complete picture of aqueous environmental effects emerges with implications for the origin of observed rate accelerations using heterogeneous aqueous suspensions, "on water" conditions. The pure TIP4P water slab maintains the bulk density and hydrogen-bonding properties in central water layers. The bulk region merges to vacuum over a ca. 5 A band with progressive diminution of the density and hydrogen bonding. The relative free energies of activation and transition structures for the reactions at the interface are found to be intermediate between those calculated in the gas phase and in bulk water; i.e., for the reaction with 1,4-naphthoquinone, the DeltaDeltaG(++) values relative to the gas phase are -3.6 and -7.3 kcal/mol at the interface and in bulk water, respectively. Thus, the results do not support the notion that a water surface is more effective than bulk water for catalysis of such pericyclic reactions. The trend is in qualitative agreement with expectations based on density considerations and estimates of experimental rate constants for the gas phase, a heterogeneous aqueous suspension, and a dilute aqueous solution for the reaction of cyclopentadiene with methyl vinyl ketone. Computed energy pair distributions reveal a uniform loss of 0.5-1.0 hydrogen bond for the reactants and transition states in progressing from bulk water to the vacuum-water interface. Orientational effects are apparent at the surface; e.g., the carbonyl group in the methyl vinyl ketone transition structure is preferentially oriented into the surface. Also, the transition structure for the 1,4-naphthoquinone case is buried more in the surface, and the free energy of

  7. Direct and Indirect Determinations of Elementary Rate Constants H + O2: Chain Branching; the Dehydration of tertiary-Butanol; the Retro Diels-Alder Reaction of Cyclohexene; the Dehydration of Isopropanol

    Science.gov (United States)

    Heyne, Joshua S.

    Due to growing environmental concern over the continued use of fossil fuels, methods to limit emissions and partially replace fossil fuel use with renewable biofuels are of considerable interest. Developing chemical kinetic models for the chemistry that affects combustion properties is important to understanding how new fuels affect combustion energy conversion processes in transportation devices. This thesis reports the experimental study of several important reactions (the H + O2 branching reaction, the key decomposition reactions of tertiary-butanol, the dehydration reaction of isopropanol, and the retro Diels-Alder reaction of cyclohexene) and develops robust analysis methods to estimate the absolute uncertainties of specific elementary rate constants derived from the experimental data. In the study of the above reactions, both a direct and indirect rate constant determination technique with associated uncertainty estimation methodologies are developed. In the study of the decomposition reactions, a direct determination technique is applied to experimental data gathered in preparation of this thesis. In the case of the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, both of which are used as internal standards for relative rate studies (Herzler et al. 1997) and chemical thermometry (Rosado-Reyes et al. 2013) , analysis showed an ˜20 K difference in the reaction rate between the reported results and the previous recommendations. In light of these discrepancies, an uncertainty estimation of previous recommendations illuminated an uncertainty of at least 20 K for the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, thus resolving the discrepancies. The determination of the H + O2 branching reaction and decomposition reactions of isopropanol used an indirect determination technique. The uncertainty of the H + O2 branching reaction rate is shown to be underestimated by previous

  8. Elucidation of Diels-Alder Reaction Network of 2,5-Dimethylfuran and Ethylene on HY Zeolite Catalyst

    Energy Technology Data Exchange (ETDEWEB)

    Do, Phuong T. M. [Univ. of Delaware, Newark, DE (United States); McAtee, Jesse R. [Univ. of Delaware, Newark, DE (United States); Watson, Donald A. [Univ. of Delaware, Newark, DE (United States); Lobo, Raul F. [Univ. of Delaware, Newark, DE (United States)

    2012-12-12

    The reaction of 2,5-dimethylfuran and ethylene to produce p-xylene represents a potentially important route for the conversion of biomass to high-value organic chemicals. Current preparation methods suffer from low selectivity and produce a number of byproducts. Using modern separation and analytical techniques, the structures of many of the byproducts produced in this reaction when HY zeolite is employed as a catalyst have been identified. From these data, a detailed reaction network is proposed, demonstrating that hydrolysis and electrophilic alkylation reactions compete with the desired Diels–Alder/dehydration sequence. This information will allow the rational identification of more selective catalysts and more selective reaction conditions.

  9. Base-catalyzed tandem Michael/dehydro-Diels-Alder reaction of α,α-dicyanoolefins with electron-deficient 1,3-conjugated enynes: a facile entry to angularly fused polycycles.

    Science.gov (United States)

    Zhang, Mingrui; Zhang, Junliang

    2014-01-07

    Angularly fused carbocyclic frameworks and their heteroatom-substituted analogues exist in many natural products that display a broad and interesting range of biological activities. Preparation of polycyclic products by cycloaddition reactions have been the long-standing hot topic in the synthetic community. Dehydro-Diels-Alder (DDA) reactions are one class of dehydropericyclic reactions that are derived conceptually by systematic removal of hydrogen atom pairs. A base-promoted tandem Michael addition and DDA reaction of α,α-dicyanoolefins with electron-deficient 1,3-conjugated enynes was realized in which a DDA reaction takes place between the arylalkynes and electron-deficient tetrasubstituted olefin. The control experiments support the stepwise anionic reaction pathway rather than the concerted reaction pathway. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Design and preparation of novel polyarylene ether materials based on Diels-Alder reaction as the crosslinker for electrooptical modulators

    Science.gov (United States)

    Gao, Wu; Hou, Wenjun; Zhen, Zhen; Liu, Xinhou; Liu, Jialei; Fedorchuk, A. A.; Czaja, P.

    2016-07-01

    Novel crosslinkable organic linear electro-optical (EO) material based on polyarylene ether as the main chain host polymer was designed and prepared. The host polymer with rigid aromatic has demonstrated a good compatibility with the guest chromophore. Long side chain with anthracene ensured the crosslinkable reaction and appropriate glass transition temperature of the host polymer (55 °C). The EO r33 tensor coefficient for this novel EO material has been magnitude of 66 pm/V at 1310 nm and the excellent long term stability at 85 °C. These parameters permit to consider their application in fabrication of organic electro optical devices. The semi-empirical and DFT quantum chemical simulations were performed for 4 principal chromophores to clarify a role of cross-linker in the enhancement of the ground state dipole moments and effective hyperpolarizabilities.

  11. Lipase-catalyzed asymmetric synthesis of naphtho[2,3-c]furan-1(3H)-one derivatives by a one-pot dynamic kinetic resolution/intramolecular Diels-Alder reaction: Total synthesis of (-)-himbacine.

    Science.gov (United States)

    Sugiyama, Koji; Kawanishi, Shinji; Oki, Yasuhiro; Kamiya, Marin; Hanada, Ryosuke; Egi, Masahiro; Akai, Shuji

    2018-04-01

    One-pot sequential reactions using the acyl moieties installed by enzymatic dynamic kinetic resolution of alcohols have been little investigated. In this work, the acryloyl moiety installed via the lipase/oxovanadium combo-catalyzed dynamic kinetic resolution of a racemic dienol [4-(cyclohex-1-en-1-yl)but-3-en-2-ol or 1-(cyclohex-1-en-1-yl)but-2-en-1-ol] with a (Z)-3-(phenylsulfonyl)acrylate underwent an intramolecular Diels-Alder reaction in a one-pot procedure to produce an optically active naphtho[2,3-c]furan-1(3H)-one derivative (98% ee). This method was successfully applied to the asymmetric total synthesis of (-)-himbacine. Copyright © 2017 Elsevier Ltd. All rights reserved.

  12. Synthesis of a Phlorin from a Meso-Fused Anthriporphyrin by a Diels-Alder Strategy.

    Science.gov (United States)

    Aslam, Adil S; Hong, Jung-Ho; Shin, June-Ho; Cho, Dong-Gyu

    2017-12-18

    An anthracene-containing meso-fused carbaporphyrin, which has extended π-conjugation pathways as compared to the corresponding naphthalene-containing carbaporphyrin, has been synthesized. The weak global aromaticity of the anthriporphyrin also allowed its use as the diene for a Diels-Alder reaction with dimethyl acetylenedicarboxylate (DMAD). The resulting phlorin contains an interesting bicyclic structure. Moreover, to the best of our knowledge, this phlorin is the first Diels-Alder adduct of a diene forming part of the global π-conjugation pathway of an aromatic porphyrinoid. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Kinetic and thermodynamic measurements for the facile property prediction of diels-alder-conjugated material behavior

    Czech Academy of Sciences Publication Activity Database

    Koehler, K. C.; Ďuračková, Andrea; Kloxin, C. J.; Bowman, C. N.

    2012-01-01

    Roč. 58, č. 11 (2012), s. 3545-3552 ISSN 0001-1541 Institutional research plan: CEZ:AV0Z40500505 Keywords : Diels - Alder reaction s * self-healing polymer networks * thermoreversible reaction s Subject RIV: CD - Macromolecular Chemistry Impact factor: 2.493, year: 2012

  14. Synthesis of Unsymmetrical Annulated 2,2’-Bipyridine Analogues with Attached Cycloalkene and Piperidine Rings via Sequential Diels-Alder Reaction of 5,5’-bi-1,2,4-triazinesâ€

    Directory of Open Access Journals (Sweden)

    D. Branowska

    2005-12-01

    Full Text Available Synthesis of bisfunctionalized unsymmetrical 2,2’-bipyridines 8 or their sulfonyl derivatives 12a,b are described. They were prepared via the Diels-Alder reaction of 1-methyl-4-pyrrolidin-1-yl-1,2,3,6-tetrahydropyridine (6 with 3,3’-bis(methyl- sulfanyl-5,5’-bi-1,2,4-triazine (1. The reaction leads to the single cycloaddition product 7 which undergoes Diels-Alder reaction with cyclic enamines 2a,b to give unsymmetrical 2,2’-bipyridine derivatives 8, consisting of the two different heterocyclic units: cycloalkeno[c]pyridine and 2,6-naphthyridine.

  15. Diversity-Oriented Approaches to Polycyclics and Bioinspired Molecules via the Diels-Alder Strategy: Green Chemistry, Synthetic Economy, and Beyond.

    Science.gov (United States)

    Kotha, Sambasivarao; Chavan, Arjun S; Goyal, Deepti

    2015-05-11

    We describe diverse approaches to various dienes and their utilization in the Diels-Alder reaction to produce a variety of polycycles. The dienes covered here are prepared by simple alkylation reaction or via the Claisen rearrangement or by enyne metathesis of alkyne or enyne building blocks. Here, we have also included the Diels-Alder chemistry of dendralenes, a higher analog of cross-conjugated dienes. The present article is inclusive of o-xylylene derivatives that are generated in situ starting with benzosultine or benzosulfone derivatives. The Diels-Alder reaction of these dienes with various dienophiles gave diverse polycyclic systems and biologically important targets.

  16. Sequential aminodiene Diels-Alder approach to the ergoline skeleton.

    Science.gov (United States)

    Padwa, Albert; Bur, Scott K; Zhang, Hongjun

    2005-08-19

    Through a novel sequence of aminodiene Diels-Alder reactions, several substituted amidofurans were readily converted to tricyclic ketones in good yield. The formation of the tricyclic ketone system is the result of a ring opening and dehydration of a transient oxabicyclic adduct formed by an intramolecular Diels-Alder cycloaddition of an amidofuran with a cyclohexenone moiety tethered such that it participates in the cycloaddition as the 2pi component. A convenient way to construct the cyclohexenone is to make use of some aminodiene chemistry developed by Rawal. An angular carbomethoxy group is required in order to activate the olefin toward cycloaddition with Rawal's diene. The presence of this activating group not only prevents the isomerization of the advanced ergoline intermediate to a naphthalene but can also be leveraged for an oxidation to provide Uhle's ketone (13). The easily formed Kornfeld ketone analogue 25 was readily transformed into the corresponding triflate 41 by the action of triflic anhydride and a base. Oxidative addition of vinyl triflate 41 to Pd(0) and the ability of the resulting vinyl palladium species to undergo cross-coupling with terminal alkynes prompted us to devise an expeditious route to lysergic acid. Unfortunately, our inability to carry out a regioselective Heck reaction using vinyl triflate 41 and the methylene amino acrylate ester 48 thwarted the completion of the synthesis of lysergic acid.

  17. An Active Alkali-Exchanged Faujasite Catalyst for p-Xylene Production via the One-Pot Diels-Alder Cycloaddition/Dehydration Reaction of 2,5-Dimethylfuran with Ethylene.

    Science.gov (United States)

    Rohling, Roderigh Y; Uslamin, Evgeny; Zijlstra, Bart; Tranca, Ionut C; Filot, Ivo A W; Hensen, Emiel J M; Pidko, Evgeny A

    2018-02-02

    The one-pot Diels-Alder cycloaddition (DAC)/dehydration (D) tandem reaction between 2,5-dimethylfuran and ethylene is a potent pathway toward biomass-derived p -xylene. In this work, we present a cheap and active low-silica potassium-exchanged faujasite (KY, Si/Al = 2.6) catalyst. Catalyst optimization was guided by a computational study of the DAC/D reaction mechanism over different alkali-exchanged faujasites using periodic density functional theory calculations complemented by microkinetic modeling. Two types of faujasite models were compared, i.e., a high-silica alkali-exchanged faujasite model representing isolated active cation sites and a low-silica alkali-exchanged faujasite in which the reaction involves several cations in the proximity. The mechanistic study points to a significant synergetic cooperative effect of the ensemble of cations in the faujasite supercage on the DAC/D reaction. Alignment of the reactants by their interactions with the cationic sites and stabilization of reaction intermediates contribute to the high catalytic performance. Experiments confirmed the prediction that KY is the most active catalyst among low-silica alkali-exchanged faujasites. This work is an example of how the catalytic reactivity of zeolites depends on multiple interactions between the zeolite and reagents.

  18. Synthesis of isochromene-type scaffolds via single-flask Diels-Alder-[4 + 2]-annulation sequence of a silyl-substituted diene with menadione.

    Science.gov (United States)

    Lee, Jihoon; Panek, James S

    2014-06-20

    A sequential Diels-Alder reaction/silicon-directed [4 + 2]-annulation was developed to assemble hydroisochromene-type ring systems from menadione 2. In the first step, a Diels-Alder of the 1-silyl-substituted butadiene 1 with 2 furnished an intermediate cyclic allylsilane. Subsequently, TMSOTf promoted a [4 + 2]-annulation through trapping of an oxonium, generated by condensation between an aldehyde and the TBS protected alcohol resulted in the formation of a cis-fused hydroisochromene 13.

  19. Asymmetric Synthesis of P-Chiral Diphosphines. Steric Effects on the Palladium-Complex-Promoted Asymmetric Diels-Alder Reaction between a Dimethylphenylphosphole and (E/Z)-Methyl-Substituted Diphenylvinylphosphines.

    Science.gov (United States)

    Aw, Beng-Hwee; Hor, T. S. Andy; Selvaratnam, S.; Mok, K. F.; White, Andrew J. P.; Williams, David J.; Rees, Nicholas H.; McFarlane, William; Leung, Pak-Hing

    1997-05-07

    The organopalladium complex containing ortho-metalated (S)-(1-(dimethylamino)ethyl)naphthalene as the chiral auxiliary has been used successfully to promote the asymmetric [4+2] Diels-Alder reactions between 1-phenyl-3,4-dimethylphosphole and the following coordinated dienophiles: (a) diphenylvinylphosphine; (b) (E)-diphenyl-1-propenylphosphine; (c) (Z)-diphenyl-1-propenylphosphine. Reaction a generates three carbon and one phosphorus stereogenic centers while reactions b and c each produce four carbon and one phosphorus chiral centers. In dichloromethane, all three reactions proceeded smoothly at room temperature giving the corresponding rigid diphosphines in high yields. Under similar reaction conditions, the reaction times observed for reactions a-c are 2, 3, and 50 h, respectively. Two-dimensional ROESY NMR studies confirmed that the prolonged reaction time required for reaction c is due to several major repulsive interactions between the chiral naphthylamine auxiliary and the (Z)-methyl-substituted vinylphosphine in the transition state. Nevertheless, all three reactions gave the corresponding rigid diphosphine in high yields. The absolute stereochemistries of the three bidentate phosphine ligands that were produced from the cycloaddition reactions have been assigned by 2D ROESY NMR spectroscopy. These diphosphines are powerful sequesterers of group 8 metals although they are highly air-sensitive in the free ligand form. The coordination chemistry and the absolute stereochemistry of the optically active complex [1alpha,4alpha,5alpha(S),6alpha(S),7R]-dichloro[5-(diphenylphosphino)-2,3,6-trimethy-7-phenyl-7-phosphabicyclo[2.2.1]-hept-2-ene-P(5)(),P(7)()]palladium(II) has been studied by single-crystal X-ray analysis. Crystal structure data: C(27)H(28)Cl(2)P(2)Pd, M(r) = 591.7; triclinic; space group P1; a = 8.643(3), b = 9.044(6), c = 9.058(4) Å; alpha = 102.75(4) degrees, beta = 108.59(2) degrees, gamma = 97.82(3) degrees; V = 638.0(5) Å(3); Z = 1; R(1) = 0.036.

  20. Naphthalene Diels-Alder in a self-assembled molecular flask.

    Science.gov (United States)

    Murase, Takashi; Horiuchi, Shinnosuke; Fujita, Makoto

    2010-03-10

    Despite its inertness toward pericyclic reactions under common conditions, naphthalenes readily undergo Diels-Alder reactions when coencapsulated with a suitable dienophile within the cavity of a self-assembled host. Localization of the reactant pair significantly reduces the entropic cost of the reaction, and preorganization within the host cavity controls both the regio- and stereoselectivity of the reaction: electronically disfavored exo adducts were obtained, and with substituted naphthalenes, the reaction takes place on the less electron-rich, unsubstituted ring. Our findings highlight the fact that judicious tuning of substrate size and shape within molecular flasks can unveil new and unusual reactivities for otherwise unreactive molecules.

  1. Effect of hydrostatic pressure, temperature, and solvent on the rate of the Diels-Alder reaction between 9,10-anthracenedimethanol and maleic anhydride

    Science.gov (United States)

    Kiselev, V. D.; Kornilov, D. A.; Anikin, O. V.; Latypova, L. I.; Konovalov, A. I.

    2017-03-01

    The rate of the reaction between 9,10-anthracenedimethanol and maleic anhydride in 1,4-dioxane, acetonitrile, trichloromethane, and toluene is studied at 25, 35, 45°C in the pressure range of 1-1772 bar. The rate constants, enthalpies, entropies and activation volumes are determined. It is shown that the rate of reaction with 9,10-anthracenedimethanol is approximately one order of magnitude higher than with 9-anthracenemethanol.

  2. Petasis/Diels-Alder/Cyclization Cascade Reactions for the Generation of Scaffolds with Multiple Stereogenic Centers and Orthogonal Handles for Library Production

    DEFF Research Database (Denmark)

    Flagstad, Thomas; Azevedo, Carlos M. G.; Min, Geanna

    2018-01-01

    A new effective strategy for the synthesis of sp3‐rich small molecules for library production is presented. The key steps to generate complexity highlight Petasis 3‐component reaction followed by an intramolecular Diels‐Alder and cyclization to generate a densely enriched tricyclic or tetracyclic...

  3. Positive photocatalysis of a Diels-Alder reaction by quenching of excited naphthalene-indole charge-transfer complex with cyclohexadiene.

    Science.gov (United States)

    Gonzalez-Béjar, María; Stiriba, Salah-Eddine; Miranda, Miguel A; Pérez-Prieto, Julia

    2007-02-01

    [reaction: see text] Naphthalene photo-catalyzes formation of cyclohexadiene-indole cycloadducts in a wavelength-dependent process. Steady-state irradiation and time-resolved fluorescence studies agree well with NP-InH ground-state charge transfer (CT) complexes as the key species responsible for the photo-catalyzed process.

  4. The Diels Alder/retro-Diels Alder concept on solid support : a study of the scope, limitations and conceivable applications as a traceless thermocleavable linker

    NARCIS (Netherlands)

    Gieling, Reinerus Gerardus

    2003-01-01

    This thesis deals with the conceivable transfer of the Diels Alder/retro-Diels Alder concept to the solid phase in order to broaden the scope of the methodology to a combinatorial level. In addition, based on this methodology the development of a traceless thermocleavable linking system for

  5. Diels-Alder Synthesis of endo-cis-N-phenylbicyclo[2.2.2]oct-5-en-2,3-dicarboximide

    Science.gov (United States)

    Baar, Marsha R.; Wustholz, Kristin

    2005-01-01

    A study investigated the Diels-Alder synthesis of endo-cis-N-phenylbicyclo [2.2.2]oct-5-en-2,3-dicarboximide. The amount of time taken by a reaction between the 1,3-cyclohexadiene and N-phenylmaleimide at room temperature and also whether the desired cycloadduct would precipitate directly from the reaction mixture was examined.

  6. Quantitative structure-activation barrier relationship modeling for Diels-Alder ligations utilizing quantum chemical structural descriptors.

    Science.gov (United States)

    Nandi, Sisir; Monesi, Alessandro; Drgan, Viktor; Merzel, Franci; Novič, Marjana

    2013-10-30

    In the present study, we show the correlation of quantum chemical structural descriptors with the activation barriers of the Diels-Alder ligations. A set of 72 non-catalysed Diels-Alder reactions were subjected to quantitative structure-activation barrier relationship (QSABR) under the framework of theoretical quantum chemical descriptors calculated solely from the structures of diene and dienophile reactants. Experimental activation barrier data were obtained from literature. Descriptors were computed using Hartree-Fock theory using 6-31G(d) basis set as implemented in Gaussian 09 software. Variable selection and model development were carried out by stepwise multiple linear regression methodology. Predictive performance of the quantitative structure-activation barrier relationship (QSABR) model was assessed by training and test set concept and by calculating leave-one-out cross-validated Q2 and predictive R2 values. The QSABR model can explain and predict 86.5% and 80% of the variances, respectively, in the activation energy barrier training data. Alternatively, a neural network model based on back propagation of errors was developed to assess the nonlinearity of the sought correlations between theoretical descriptors and experimental reaction barriers. A reasonable predictability for the activation barrier of the test set reactions was obtained, which enabled an exploration and interpretation of the significant variables responsible for Diels-Alder interaction between dienes and dienophiles. Thus, studies in the direction of QSABR modelling that provide efficient and fast prediction of activation barriers of the Diels-Alder reactions turn out to be a meaningful alternative to transition state theory based computation.

  7. Studies toward the synthesis of palhinine lycopodium alkaloids: a Morita-Baylis-Hillman/intramolecular Diels-Alder approach.

    Science.gov (United States)

    Sizemore, Nicholas; Rychnovsky, Scott D

    2014-02-07

    A synthetic route to the isotwistane core of palhinine lycopodium alkaloids is described. A Morita-Baylis-Hillman/intramolecular Diels-Alder (IMDA) strategy sets the vicinal all-carbon quaternary centers present in this family of natural products. The regioselectivity of the IMDA reaction is dictated by the conditions employed for silyl enol ether formation, with one set of conditions providing the core of cardionine and alternate conditions generating the desired isotwistane core of isopalhinine.

  8. Tyrosine-lipid peroxide adducts from radical termination: para coupling and intramolecular Diels-Alder cyclization.

    Science.gov (United States)

    Shchepin, Roman; Möller, Matias N; Kim, Hye-young H; Hatch, Duane M; Bartesaghi, Silvina; Kalyanaraman, Balaraman; Radi, Rafael; Porter, Ned A

    2010-12-15

    Free radical co-oxidation of polyunsaturated lipids with tyrosine or phenolic analogues of tyrosine gave rise to lipid peroxide-tyrosine (phenol) adducts in both aqueous micellar and organic solutions. The novel adducts were isolated and characterized by 1D and 2D NMR spectroscopy as well as by mass spectrometry (MS). The spectral data suggest that the polyunsaturated lipid peroxyl radicals give stable peroxide coupling products exclusively at the para position of the tyrosyl (phenoxy) radicals. These adducts have characteristic (13)C chemical shifts at 185 ppm due to the cross-conjugated carbonyl of the phenol-derived cyclohexadienone. The primary peroxide adducts subsequently undergo intramolecular Diels-Alder (IMDA) cyclization, affording a number of diastereomeric tricyclic adducts that have characteristic carbonyl (13)C chemical shifts at ~198 ppm. All of the NMR HMBC and HSQC correlations support the structure assignments of the primary and Diels-Alder adducts, as does MS collision-induced dissociation data. Kinetic rate constants and activation parameters for the IMDA reaction were determined, and the primary adducts were reduced with cuprous ion to give a phenol-derived 4-hydroxycyclohexa-2,5-dienone. No products from adduction of peroxyls at the phenolic ortho position were found in either the primary or cuprous reduction product mixtures. These studies provide a framework for understanding the nature of lipid-protein adducts formed by peroxyl-tyrosyl radical-radical termination processes. Coupling of lipid peroxyl radicals with tyrosyl radicals leads to cyclohexenone and cyclohexadienone adducts, which are of interest in and of themselves since, as electrophiles, they are likely targets for protein nucleophiles. One consequence of lipid peroxyl reactions with tyrosyls may therefore be protein-protein cross-links via interprotein Michael adducts.

  9. Hydrogen Abstraction Acetylene Addition and Diels-Alder Mechanisms of PAH Formation:  A Detailed Study Using First Principles Calculations.

    Science.gov (United States)

    Kislov, V V; Islamova, N I; Kolker, A M; Lin, S H; Mebel, A M

    2005-09-01

    Extensive ab initio Gaussian-3-type calculations of potential energy surfaces (PES), which are expected to be accurate within 1-2 kcal/mol, combined with statistical theory calculations of reaction rate constants have been applied to study various possible pathways in the hydrogen abstraction acetylene addition (HACA) mechanism of naphthalene and acenaphthalene formation as well as Diels-Alder pathways to acenaphthalene, phenanthrene, and pyrene. The barrier heights; reaction energies; and molecular parameters of the reactants, products, intermediates, and transition states have been generated for all types of reactions involved in the HACA and Diels-Alder mechanisms, including H abstraction from various aromatic intermediates, acetylene addition to radical sites, ring closures leading to the formation of additional aromatic rings, elimination of hydrogen atoms, H disproportionation, C2H2 cycloaddition, and H2 loss. The reactions participating in various HACA sequences (e.g., Frenklach's, alternative Frenklach's, and Bittner and Howard's routes) are demonstrated to have relatively low barriers and high rate constants under combustion conditions. A comparison of the significance of different HACA mechanisms in PAH growth can be made in the future using PES and molecular parameters obtained in the present work. The results show that the Diels-Alder mechanism cannot compete with the HACA pathways even at high combustion temperatures, because of high barriers and consequently low reaction rate constants. The calculated energetic parameters and rate constants have been compared with experimental and theoretical data available in the literature.

  10. Biodegradable hyaluronic acid hydrogels to control release of dexamethasone through aqueous Diels-Alder chemistry for adipose tissue engineering.

    Science.gov (United States)

    Fan, Ming; Ma, Ye; Zhang, Ziwei; Mao, Jiahui; Tan, Huaping; Hu, Xiaohong

    2015-11-01

    A robust synthetic strategy of biopolymer-based hydrogels has been developed where hyaluronic acid derivatives reacted through aqueous Diels-Alder chemistry without the involvement of chemical catalysts, allowing for control and sustain release of dexamethasone. To conjugate the hydrogel, furan and maleimide functionalized hyaluronic acid were synthesized, respectively, as well as furan functionalized dexamethasone, for the covalent immobilization. Chemical structure, gelation time, morphologies, swelling kinetics, weight loss, compressive modulus and dexamethasone release of the hydrogel system in PBS at 37°C were studied. The results demonstrated that the aqueous Diels-Alder chemistry provides an extremely selective reaction and proceeds with high efficiency for hydrogel conjugation and covalent immobilization of dexamethasone. Cell culture results showed that the dexamethasone immobilized hydrogel was noncytotoxic and preserved proliferation of entrapped human adipose-derived stem cells. This synthetic approach uniquely allows for the direct fabrication of biologically functionalized gel scaffolds with ideal structures for adipose tissue engineering, which provides a competitive alternative to conventional conjugation techniques such as copper mediated click chemistry. Copyright © 2015. Published by Elsevier B.V.

  11. Revisiting the stability of endo/exo Diels-Alder adducts between cyclopentadiene and 1,4-benzoquinone

    International Nuclear Information System (INIS)

    Tormena, Claudio F.; Lacerda Junior, Valdemar; Oliveira, Kleber T. de

    2010-01-01

    In this work it is presented a detailed theoretical analysis of the relative stability of endo/exo Diels-Alder adducts formed by the reaction between cyclopentadiene (1) and 1,4-benzoquinone (2). The intrinsic reaction coordinate (IRC) showed the existence of only one transition state for the reaction studied, for both endo 3 and exo 4 adducts. The energies of both adducts were obtained at high level of theory (CBS-Q) confirming that the endo adduct is more stable than exo, which is in the opposite way to the observed in reactions that usually follow Alder's rule. An electronic structure analysis was performed through NBO methodology, indicating that the attractive delocalization interaction predominates over the steric repulsive interaction in the endo adducts. In summary, for the studied cycloaddition reaction the endo adduct is the thermodynamic and kinetic product, which can be also confirmed by experimental data mentioned in this work. (author)

  12. Revisiting the stability of endo/exo Diels-Alder adducts between cyclopentadiene and 1,4-benzoquinone

    Energy Technology Data Exchange (ETDEWEB)

    Tormena, Claudio F. [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Quimica. Dept. de Quimica Organica; Lacerda Junior, Valdemar [Universidade Federal do Espirito Santo (UFES), Vitoria, ES (Brazil). Centro de Ciencias Exatas. Dept. de Quimica; Oliveira, Kleber T. de [Universidade Federal do ABC (UFABC), Santo Andre, SP (Brazil). Centro de Ciencias Naturais e Humanas

    2010-07-01

    In this work it is presented a detailed theoretical analysis of the relative stability of endo/exo Diels-Alder adducts formed by the reaction between cyclopentadiene (1) and 1,4-benzoquinone (2). The intrinsic reaction coordinate (IRC) showed the existence of only one transition state for the reaction studied, for both endo 3 and exo 4 adducts. The energies of both adducts were obtained at high level of theory (CBS-Q) confirming that the endo adduct is more stable than exo, which is in the opposite way to the observed in reactions that usually follow Alder's rule. An electronic structure analysis was performed through NBO methodology, indicating that the attractive delocalization interaction predominates over the steric repulsive interaction in the endo adducts. In summary, for the studied cycloaddition reaction the endo adduct is the thermodynamic and kinetic product, which can be also confirmed by experimental data mentioned in this work. (author)

  13. Diels-Alder cycloaddition strategy for kinetic resolution of chiral pyrazolidinones.

    Science.gov (United States)

    Sibi, Mukund P; Kawashima, Keisuke; Stanley, Levi M

    2009-09-03

    A rare example of the application of a catalytic, enantioselective Diels-Alder cycloaddition to affect a kinetic resolution has been developed. Chiral pyrazolidinones are resolved with high selectivity through a process that utilizes a relay of stereochemical information from a permanent chiral center to a fluxional chiral center to enhance the inherent selectivity of the chiral Lewis acid catalyst.

  14. Thermally reversible rubber-toughened thermoset networks via Diels-Alder chemistry

    NARCIS (Netherlands)

    Araya-Hermosilla, R.; Fortunato, G.; Pucci, A.; Raffa, P.; Polgar, L.; Broekhuis, A. A.; Pourhossein, P.; Lima, G. M. R.; Beljaars, M.; Picchioni, F.

    In this work we present a reversible and toughened thermoset system based on the covalent incorporation of a furane functionalized ethylene-propylene rubber (EPM-Fu) into a thermoset furane functionalized polyketone (PK-Fu) via Diels-Alder (DA) reversible cross-linking with bismaleimide (b-MA).

  15. Further studies of the thermal and photochemical diels-alder reactions of N-methyl-1,2,4-triazoline-3,5-dione (MeTAD) with naphthalene and some substituted naphthalenes

    Science.gov (United States)

    Breton; Newton

    2000-05-19

    MeTAD thermally reacted with naphthalene (2) and methylated naphthalenes to give equilibrium mixtures of starting materials and [4 + 2] cycloadducts. Methyl substitution on the naphthalene ring generally increased both the amount of cycloadduct formed and the rate of cycloaddition relative to 2. The isolated cycloadducts were all thermally labile and quantitatively reverted to the parent naphthalene in the presence of 2,3-dimethyl-2-butene as a trap for liberated MeTAD. The rates of the cycloreversion reactions were affected by substitution patterns but not appreciably by solvent. A mechanism for the cycloaddition reaction is presented that proposes the involvement of a charge-transfer complex. Photochemically, MeTAD demonstrated lower regioselectivity in its reactions with substituted naphthalenes relative to the corresponding thermal reactions.

  16. Diels-Alder functionalized carbon nanotubes for bone tissue engineering: in vitro/in vivo biocompatibility and biodegradability

    Science.gov (United States)

    Mata, D.; Amaral, M.; Fernandes, A. J. S.; Colaço, B.; Gama, A.; Paiva, M. C.; Gomes, P. S.; Silva, R. F.; Fernandes, M. H.

    2015-05-01

    The risk-benefit balance for carbon nanotubes (CNTs) dictates their clinical fate. To take a step forward at this crossroad it is compulsory to modulate the CNT in vivo biocompatibility and biodegradability via e.g. chemical functionalization. CNT membranes were functionalised combining a Diels-Alder cycloaddition reaction to generate cyclohexene (-C6H10) followed by a mild oxidisation to yield carboxylic acid groups (-COOH). In vitro proliferation and osteogenic differentiation of human osteoblastic cells were maximized on functionalized CNT membranes (p,f-CNTs). The in vivo subcutaneously implanted materials showed a higher biological reactivity, thus inducing a slighter intense inflammatory response compared to non-functionalized CNT membranes (p-CNTs), but still showing a reduced cytotoxicity profile. Moreover, the in vivo biodegradation of CNTs was superior for p,f-CNT membranes, likely mediated by the oxidation-induced myeloperoxidase (MPO) in neutrophil and macrophage inflammatory milieus. This proves the biodegradability faculty of functionalized CNTs, which potentially avoids long-term tissue accumulation and triggering of acute toxicity. On the whole, the proposed Diels-Alder functionalization accounts for the improved CNT biological response in terms of the biocompatibility and biodegradability profiles. Therefore, CNTs can be considered for use in bone tissue engineering without notable toxicological threats.The risk-benefit balance for carbon nanotubes (CNTs) dictates their clinical fate. To take a step forward at this crossroad it is compulsory to modulate the CNT in vivo biocompatibility and biodegradability via e.g. chemical functionalization. CNT membranes were functionalised combining a Diels-Alder cycloaddition reaction to generate cyclohexene (-C6H10) followed by a mild oxidisation to yield carboxylic acid groups (-COOH). In vitro proliferation and osteogenic differentiation of human osteoblastic cells were maximized on functionalized CNT

  17. T3P- A Novel Catalyst for Aza-Diels-Alder Reaction: One-Pot Synthesis of Pyrano[3,2-c]quinolines and furano[3,2-c]quinolines

    Directory of Open Access Journals (Sweden)

    T. S. R. Prasanna

    2011-01-01

    Full Text Available T3P was found to be an efficient catalyst for the Aza-Diels–Alder reactions of aldimines with dihydropyran or dihydrofuran to afford the corresponding pyrano-and furo [3,2-c]quinolines in high yields with high diastereoselectivity in a short period of time.

  18. Pedagogical Comparison of Five Reactions Performed under Microwave Heating in Multi-Mode versus Mono-Mode Ovens: Diels-Alder Cycloaddition, Wittig Salt Formation, E2 Dehydrohalogenation to Form an Alkyne, Williamson Ether Synthesis, and Fischer Esterification

    Science.gov (United States)

    Baar, Marsha R.; Gammerdinger, William; Leap, Jennifer; Morales, Erin; Shikora, Jonathan; Weber, Michael H.

    2014-01-01

    Five reactions were rate-accelerated relative to the standard reflux workup in both multi-mode and mono-mode microwave ovens, and the results were compared to determine whether the sequential processing of a mono-mode unit could provide for better lab logistics and pedagogy. Conditions were optimized so that yields matched in both types of…

  19. An intermolecular Diels-Alder cycloaddition under various condition between 1,3-cyclohexadiene and 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate

    Directory of Open Access Journals (Sweden)

    Özgür Yılmaz

    2017-10-01

    Full Text Available The reaction between 1,3-cyclohexadiene and dimethyl 7-oxabicyclo[2.2.1]hepta-2,5-diene-2,3-dicarboxylate both without a catalyst and with different catalysts, in both atmospheric and at high pressure, over 20 days were studied. At the end of the reactions, different products (retro Diels-Alder addition product 5 and Diels-Alder addition product 6 were obtained in different yields. When we look at the percentage of the addition product, it is observed that the yield of reaction at high pressure in water is the highest. All structures of these products were characterized by 1H-NMR, 13C-NMR, MS, and IR spectroscopy.

  20. Novel Diels-Alder based self-healing epoxies for aerospace composites

    Science.gov (United States)

    Coope, T. S.; Turkenburg, D. H.; Fischer, H. R.; Luterbacher, R.; van Bracht, H.; Bond, I. P.

    2016-08-01

    Epoxy resins containing Diels-Alder (DA) furan and maleimide moieties are presented with the capability to self-heal after exposure to an external heat source. A conventional epoxy amine system has been combined with furfuryl and maleimide functional groups in a two-step process, to avoid major side-reactions, and the concentration of a thermo-reversibly binding cross-linker was considered to balance thermoset and thermoplastic behaviours, and the subsequent self-healing performance. In the context of self-repair technologies an inbuilt ‘intrinsic’ self-healing system is deemed favourable as the healing agent can be placed in known ‘hot spot’ regions (i.e. skin-stringer run outs, ply drops and around drilled holes) where operational damage predominately occurs in load bearing aerospace structures. In this study, the mechanical and self-healing performance of furan functionalised epoxy resins containing varying amounts (10, 20, 30 or 40 pph) of bismaleimide were investigated using a bulk epoxy polymer tapered double cantilever beam test specimen geometry. Two forms, a thin film and a bulk material, were evaluated to account for future integration methods into fibre reinforced polymer (FRP) composites. The highest healing efficiency, with respect to the obtained initial load value, was observed from the 20 pph bulk material derivative. The polymers were successful in achieving consistent multiple (three) healing cycles when heated at 150 °C for 5 min. This novel investigated DA material exhibits favourable processing characteristics for FRP composites as preliminary studies have shown successful coextrution with reinforcing fibres to form free standing films and dry fibre impregnation.

  1. SAM-dependent enzyme-catalysed pericyclic reactions in natural product biosynthesis

    Science.gov (United States)

    Ohashi, Masao; Liu, Fang; Hai, Yang; Chen, Mengbin; Tang, Man-Cheng; Yang, Zhongyue; Sato, Michio; Watanabe, Kenji; Houk, K. N.; Tang, Yi

    2017-09-01

    Pericyclic reactions—which proceed in a concerted fashion through a cyclic transition state—are among the most powerful synthetic transformations used to make multiple regioselective and stereoselective carbon-carbon bonds. They have been widely applied to the synthesis of biologically active complex natural products containing contiguous stereogenic carbon centres. Despite the prominence of pericyclic reactions in total synthesis, only three naturally existing enzymatic examples (the intramolecular Diels-Alder reaction, and the Cope and the Claisen rearrangements) have been characterized. Here we report a versatile S-adenosyl-L-methionine (SAM)-dependent enzyme, LepI, that can catalyse stereoselective dehydration followed by three pericyclic transformations: intramolecular Diels-Alder and hetero-Diels-Alder reactions via a single ambimodal transition state, and a retro-Claisen rearrangement. Together, these transformations lead to the formation of the dihydropyran core of the fungal natural product, leporin. Combined in vitro enzymatic characterization and computational studies provide insight into how LepI regulates these bifurcating biosynthetic reaction pathways by using SAM as the cofactor. These pathways converge to the desired biosynthetic end product via the (SAM-dependent) retro-Claisen rearrangement catalysed by LepI. We expect that more pericyclic biosynthetic enzymatic transformations remain to be discovered in naturally occurring enzyme ‘toolboxes’. The new role of the versatile cofactor SAM is likely to be found in other examples of enzyme catalysis.

  2. On the Diels-Alder approach to solely biomass-derived polyethylene terephthalate (PET): conversion of 2,5-dimethylfuran and acrolein into p-xylene.

    Science.gov (United States)

    Shiramizu, Mika; Toste, F Dean

    2011-10-24

    Polyethylene terephthalate (PET) is a polymeric material with high global demand. Conventionally, PET is produced from fossil-fuel-based materials. Herein, we explored the feasibility of a sustainable method for PET production by using solely bio-renewable resources. Specifically, 2,5-dimethylfuran (derived from lignocellulosic biomass through 5-(hydroxymethyl)furfural) and acrolein (produced from glycerol, a side product of biodiesel production) were converted into the key intermediate p-xylene (a precursor of terephthalic acid). This synthesis consists of a sequential Diels-Alder reaction, oxidation, dehydration, and decarboxylation. In particular, the pivotal first step, the Diels-Alder reaction, was studied in detail to provide useful kinetic and thermodynamic data. Although it was found that this reaction requires low temperature to proceed efficiently, which presents a limitation on economic feasibility on an industrial scale, the concept was realized and bio-derived p-xylene was obtained in 34% overall yield over four steps. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Imino Diels-Alder-Based Construction of a Piperidine A-Ring Unit for Total Synthesis of the Marine Hepatotoxin Cylindrospermopsin.

    Science.gov (United States)

    Heintzelman, Geoffrey R.; Weinreb, Steven M.; Parvez, Masood

    1996-07-12

    The synthesis of a piperidine A-ring precursor to the alkaloid cylindrospermopsin (1) is described. The initial approach to the A-ring precursor focused on the imino Diels-Alder reaction of diene 8 with ethyl (N-tosylimino)acetate (9) to form the cycloadduct 10 as a single stereoisomer. However, all attempts to convert ester 10 to a requisite diene such as 5 were unsuccessful. An alternative strategy involved the Diels-Alder cycloaddition of N-tosylimine 9 with oxygenated diene 19 under either thermal or Lewis acid-catalyzed conditions to produce a mixture of cis and trans enones 20 and 21. Although the undesired cis-enone 20 was the major product under all reaction conditions, it could be converted to the desired trans enone 21 by acid-catalyzed isomerization. Copper-mediated conjugate addition of vinylmagnesium bromide to cis-enone 20 followed by stereoselective ketone reduction with L-Selectride produced alcohol 23, whose structure was confirmed by X-ray crystallography. Similarly, trans-enone 21 was converted to alcohol 25 whose structure and stereochemistry were also established by X-ray analysis. Alcohol 25 was then protected as the silyl ether 26, which was hydroborated at the terminal olefin to produce primary alcohol ester 28having the stereochemistry and functionality needed for cylindrospermopsin.

  4. A facile avenue to conductive polymer brushes via cyclopentadiene-maleimide Diels-Alder ligation

    Czech Academy of Sciences Publication Activity Database

    Yameen, B.; Rodriguez-Emmenegger, C.; Preuss, C. M.; Pop-Georgievski, Ognen; Verveniotis, Elisseos; Trouillet, V.; Rezek, Bohuslav; Barner-Kowollik, C.

    2013-01-01

    Roč. 49, č. 77 (2013), s. 8623-8625 ISSN 1359-7345 R&D Projects: GA ČR GBP205/12/G118; GA ČR GAP108/11/1857; GA ČR(CZ) GBP108/12/G108 Institutional support: RVO:61389013 ; RVO:68378271 Keywords : conductive poly(3-hexylthiophen) brushes * Diels-Alder ligation * Kelvin Probe Force Microscopy (KFM) Subject RIV: CD - Macromolecular Chemistry Impact factor: 6.718, year: 2013

  5. Synthesis of novel steroid-tetrahydroquinoline hybrid molecules and D-homosteroids by intramolecular cyclization reactions.

    Science.gov (United States)

    Magyar, Angéla; Wölfling, János; Kubas, Melanie; Cuesta Seijo, Jose Antonio; Sevvana, Madhumati; Herbst-Irmer, Regine; Forgó, Péter; Schneider, Gyula

    2004-05-01

    Steroidal aryliminium salts were prepared from D-seco-pregnene aldehyde 2b, and their BF3.OEt2-catalyzed reactions were studied. The nature of the substituent R1 in the anilines 3-6 essentially influenced the chemoselectivity. Using unsubstituted 3, 4-methoxy- (4) or 4-bromoaniline (5), different tetrahydroquinoline derivatives 7a-13a via intramolecular hetero Diels-Alder reaction were formed. In the case of 4-nitroaniline (6) the N-arylamino-D-homopregnane (14a) were also obtained. We assume, that an intramolecular Prins reaction led to this type of fluoro-D-homosteroid. The main products represent a new class of tetrahydroquinolino-androstenes.

  6. Biogenesis of Triterpene Dimers from Orthoquinones Related to Quinonemethides: Theoretical Study on the Reaction Mechanism

    Directory of Open Access Journals (Sweden)

    Mariana Quesadas-Rojas

    2016-11-01

    Full Text Available The biogenetic origin of triterpene dimers from the Celastraceae family has been proposed as assisted hetero-Diels-Alder reaction (HDA. In this work, computational calculation of HDA between natural quinonemethides (tingenone and isopristimerol and hypothetical orthoquinones has been performed at the M06-2X/6-31G(d level of theory. We have located all the HDA transition states supporting the biogenetic route via HDA cycloadditions. We found that all reactions take place through a concerted inverse electron demand and asynchronous mechanism. The enzymatic assistance for dimer formation was analyzed in terms of the calculated transition state energy barrier.

  7. Determination of ergocalciferol in human plasma after Diels-Alder derivatization by LC–MS/MS and its application to a bioequivalence study

    Directory of Open Access Journals (Sweden)

    Pritesh Contractor

    2017-12-01

    Full Text Available An accurate, sensitive and selective method is developed for determination of ergocalciferol (vitamin D2 in human plasma using LC–MS/MS. After liquid-liquid extraction with n-hexane, ergocalciferol was derivatized by reacting with 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD, a strong dienophile based on Diels-Alder reaction. Ergocalciferol and its deuterated internal standard, ergocalciferol-d6, were analyzed on X Select CSH C18 (100 mm×4.6 mm, 2.5 µm column using acetonitrile and 0.1% (v/v formic acid in water containing 0.14% methylamine within 6.0 min under gradient elution mode. Tandem mass spectrometry in positive ionization mode was used to quantify ergocalciferol by multiple reaction monitoring (MRM. Entire data processing was done using Watson LIMS™ software which provided excellent data integrity and high throughput with improved operational efficiency. The major advantage of this method includes higher sensitivity (0.10 ng/mL, superior extraction efficiency (≥83% and small sample volume (100 µL for processing. The method was linear in the concentration range of 0.10–100 ng/mL for ergocalciferol. The intra-batch and inter-batch accuracy and precision (% CV values varied from 97.3% to 109.0% and 1.01% to 5.16%, respectively. The method was successfully applied to support a bioequivalence study of 1.25 mg ergocalciferol capsules in 12 healthy subjects. Keywords: Ergocalciferol, Diels-Alder reaction, 4-phenyl-1,2,4-triazoline-3,5-dione, LC–MS/MS, Human plasma

  8. An efficient synthesis of novel pyrano[2,3-d]- and furopyrano[2,3-d]pyrimidines via indium-catalyzed multi-component domino reaction

    Directory of Open Access Journals (Sweden)

    Gohain Mukut

    2006-06-01

    Full Text Available Abstract Various novel pyrano [2,3-d]pyrimidines 5 and furopyrano [2,3-d]pyrimidines 7 were synthesized in 80–99% yields via a multicomponent domino Knoevenagel/hetero-Diels-Alder reaction of 1,3-dimethyl barbituric acid with an aromatic aldehyde and ethyl vinyl ether/2,3-dihydrofuran in presence of 1 mol% of indium(III chloride. The reaction also proceeds in aqueous media without using any catalyst, but the yield is comparatively less (65–70%.

  9. The Preparation and Properties of Thermo-reversibly Cross-linked Rubber Via Diels-Alder Chemistry

    NARCIS (Netherlands)

    Polgar, Lorenzo Massimo; van Duin, Martin; Picchioni, Francesco

    2016-01-01

    A method for using Diels Alder thermo-reversible chemistry as cross-linking tool for rubber products is demonstrated. In this work, a commercial ethylene-propylene rubber, grafted with maleic anhydride, is thermo-reversibly cross-linked in two steps. The pending anhydride moieties are first modified

  10. Fusing catechol-driven surface anchoring with rapid hetero Diels-Alder ligation

    Czech Academy of Sciences Publication Activity Database

    Preuss, C. M.; Zieger, M. M.; Rodriguez-Emmenegger, Cesar; Zydziak, N.; Trouillet, V.; Goldmann, A. S.; Barner-Kowollik, C.

    2014-01-01

    Roč. 3, č. 11 (2014), s. 1169-1173 ISSN 2161-1653 R&D Projects: GA MŠk(CZ) ED1.1.00/02.0109; GA ČR GBP205/12/G118 Institutional support: RVO:61389013 Keywords : nanoparticles * biosensors * polymer brushes Subject RIV: BO - Biophysics Impact factor: 5.764, year: 2014

  11. Application of microwave irradiation to organic liquid phase reactions

    International Nuclear Information System (INIS)

    Huang Kun; Liu Hua; Ji Xuelin

    1994-01-01

    Microwave irradiation has been used in organic liquid phase reactions to significantly reduce the reaction time and improve the yield. The proposed mechanism, the development of techniques and reactions, such as Diels-Alder, ene, rearrangement reactions etc., are discussed

  12. A Tri-O-Bridged Diels-Alder Adduct from Cortex Mori Radicis

    Directory of Open Access Journals (Sweden)

    An-Qi Lu

    2018-01-01

    Full Text Available Sanggenon X, an unusual tri-O-bridged Diels-Alder adduct, was isolated from Cortex Mori Radicis. Its structure was established by spectroscopic analysis, including NMR and HR-MS (High Resolution Mass Spectrometry. Sanggenon X contained three O-bridged rings, where the oxygenated bridgeheads were all quaternary carbons. Chemical methylation was carried out to deduce the linkages of the three O-bridges. The absolute configuration was determined by calculating the ECD (Electronic Circular Dichroism using the TDDFT (Time-Dependent Density Functional Theory method. Sanggenon X showed significant antioxidant activity against Fe2+-Cys-induced lipid peroxidation in rat liver microsomes, and was as effective as the positive control, curcumin.

  13. Biotransformation of a cage-like diels-alder adduct and derivatives by Mucor ramosissimus samutsevitsch Biotransformação de um aduto de diels-alder cage-like e derivados por Mucor ramosissimus samutsevitsch

    Directory of Open Access Journals (Sweden)

    Felicia Megumi Ito

    2009-09-01

    Full Text Available The present study aimed to evaluate the ability for biotransformation of the Diels-Alder adduct tricyclo[6.2.1.0(2,7]undeca-4,9-dien-3,6-dione (1 and two synthetic derivatives by the saprobe fungus Mucor ramosissimus Samutsevitsch. Products from oxidation, isomerization and, regioselective and enantioselective reduction were achieved.Neste trabalho avaliou-se a capacidade de biotransformação do aduto de Diels-Alder triciclo[6.2.1.0(2-7]undeca-4,9-dien-3,6-diona (1 e dois derivados sintéticos pelo fungo sapróbio Mucor ramosissimus Samutsevitsch. Produtos de oxidação, isomerização e redução regiosseletiva e enantiosseletiva foram obtidos.

  14. Random quaternary ammonium Diels-Alder poly(phenylene) copolymers for improved vanadium redox flow batteries

    Science.gov (United States)

    Largier, Timothy D.; Cornelius, Chris J.

    2017-06-01

    This study analyzes the effect of quaternary ammonium homopolymer (AmPP) and ionic and non-ionic random unit copolymerization (AmPP-PP) of Diels-Alder poly(phenylene)s on electrochemical and transport properties, vanadium redox flow battery performance, and material stability. AmPP-PP materials were synthesized with IEC's up to 2.2 meq/g, displaying a carbonate form ion conductivity of 17.3 mS/cm and water uptake of 57.3%. Vanadium ion permeability studies revealed that the random copolymers possess superior charge carrier selectivity. For materials of comparable ion content, at 10 mA/cm2 the random copolymer displayed a 14% increase in coulombic efficiency (CE) corresponding to a 7% increase in energy efficiency. All quaternary ammonium materials displayed ex situ degradation in a 0.5 M V5+ + 5 M H2SO4 solution, with the rate of degradation appearing to increase with IEC. Preliminary studies reveal that the neutralizing counter-ion has a significant effect on VRB performance, proportional to changes in vanadium ion molecular diffusion.

  15. Development of new chiral auxiliary from the Diels-Alder adduct endo-tricyclo[6.2.1.02,7] undeca-4 ,9-dien-3 ,6-dione

    Directory of Open Access Journals (Sweden)

    Suély Copini

    2012-06-01

    Full Text Available Stereochemistry control is very important in organic synthesis and it is a basic challenge in asymmetric synthesis. An approach widely used is making use of chiral auxiliary compounds. In this work it is showed the synthesis of highly optically pure rigid polycyclic compounds from the Diels-Alder adduct 1. Compounds 1-3 were prepared as described by Ito et. al. [1]. The alcohol (--3 was obtained by biotransformation of diketone 2 with Mucor ramosissimus, e.e.>99% (60%. The polycyclic halides 4-6 were synthesized (60-97% after treatment of alcohol (--3 with NBS, NIS and, NCS in dichloromethane, respectively. Compound 7 was prepared by reaction with p-toluenesulfonic acid, whilst 8 was prepared by treatment of (--3 with m-chloroperbenzoic acid. The strained polycylic alcohols 9-13 will be achieved by reduction of ketones 4-8 with NaBH4. All compounds were identified by 1H and 13C NMR spectroscopy. Due to intrinsic rigidity of the synthesized polycyclic, they could be of use as chiral auxiliary agents. Prochiral substrates can be readily attached by many ways to C-3 or through hydroxyl group found in compounds 8-13. The stereo-dirigent potential of these polycyclic can also be increased by directly or indirectly introduction of many groups at position C-3, or at adjacent positions to carbonyl or hydroxyl at C-3 and C-10.

  16. An interpenetrating HA/G/CS biomimic hydrogel via Diels-Alder click chemistry for cartilage tissue engineering.

    Science.gov (United States)

    Yu, Feng; Cao, Xiaodong; Zeng, Lei; Zhang, Qing; Chen, Xiaofeng

    2013-08-14

    In order to mimic the natural cartilage extracellular matrix, a novel biological degradable interpenetrating network hydrogel was synthesized from the gelatin (G), hyaluronic acid (HA) and chondroitin sulfate (CS) by Diels-Alder "click" chemistry. HA was modified with furylamine and G was modified with furancarboxylic acid respectively. (1)H NMR spectra and elemental analysis showed that the substitution degrees of HA-furan and G-furan were 71.5% and 44.5%. Then the hydrogels were finally synthesized by cross-linking furan-modified HA and G derivatives with dimaleimide poly(ethylene glycol) (MAL-PEG-MAL). The mechanical and degradation properties of the hydrogels could be tuned simply through varying the molar ratio between furan and maleimide. Rheological, mechanical and degradation studies demonstrated that the Diels-Alder "click" chemistry is an efficient method for preparing high performance biological interpenetrating hydrogels. This biomimic hydrogel with improved mechanical properties could have great potential applications in cartilage tissue engineering. Copyright © 2013 Elsevier Ltd. All rights reserved.

  17. Magnetic hyaluronic acid nanospheres via aqueous Diels-Alder chemistry to deliver dexamethasone for adipose tissue engineering.

    Science.gov (United States)

    Jia, Yang; Fan, Ming; Chen, Huinan; Miao, Yuting; Xing, Lian; Jiang, Bohong; Cheng, Qifan; Liu, Dongwei; Bao, Weikang; Qian, Bin; Wang, Jionglu; Xing, Xiaodong; Tan, Huaping; Ling, Zhonghua; Chen, Yong

    2015-11-15

    Biopolymer-based nanospheres have great potential in the field of drug delivery and tissue regenerative medicine. In this work, we present a flexible way to conjugate a magnetic hyaluronic acid (HA) nanosphere system that are capable of vectoring delivery of adipogenic factor, e.g. dexamethasone, for adipose tissue engineering. Conjugation of nanospheres was established by aqueous Diels-Alder chemistry between furan and maleimide of HA derivatives. Simultaneously, a furan functionalized dexamethasone peptide, GQPGK, was synthesized and covalently immobilized into the nanospheres. The magnetic HA nanospheres were fabricated by encapsulating super-paramagnetic iron oxide nanoparticles, which exhibited quick magnetic sensitivity. The aqueous Diels-Alder chemistry made nanospheres high binding efficiency of dexamethasone, and the vectoring delivery of dexamethasone could be easily controlled by a external magnetic field. The potential application of the magnetic HA nanospheres on vectoring delivery of adipogenic factor was confirmed by co-culture of human adipose-derived stem cells (ASCs). In vitro cytotoxicity tests demonstrated that incorporation of dexamethasone into magnetic HA nanospheres showed high efficiency to promote ASCs viabilities, in particular under a magnetic field, which suggested a promising future for adipose regeneration applications. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Cross-linking of rubber in the presence of multi-functional cross-linking aids via thermoreversible Diels-Alder chemistry

    NARCIS (Netherlands)

    Polgar, L. M.; Fortunato, G.; Araya-Hermosilla, R.; van Duin, M.; Pucci, A.; Picchioni, F.

    Furan-functionalized polyketone (PK-FU) was added to a furan-functionalized ethylene-propylene rubber (EPM-FU). The mixture was subsequently cross-linked with a bismaleimide through Diels-Alder chemistry in order to improve the mechanical properties of the rubber. Infrared spectroscopy showed the

  19. Use of Diels-Alder Chemistry for Thermoreversible Cross-Linking of Rubbers : The Next Step toward Recycling of Rubber Products?

    NARCIS (Netherlands)

    Polgar, L. M.; van Duin, M.; Broekhuis, A. A.; Picchioni, F.

    2015-01-01

    A proof of principle for the use of Diels-Alder chemistry as a thermoreversible cross-linking tool for rubber products is demonstrated. A commercial ethylene-propylene rubber grafted with maleic anhydride has been thermoreversibly cross-linked in two steps. The pending anhydride rings were first

  20. Bio-based self-healing coatings based on thermo-reversible Diels-Alder reaction

    NARCIS (Netherlands)

    Turkenburg, D.H.; Durant, Y.; Fischer, H.R.

    2017-01-01

    Stimulated by the growing demand for greener and more sustainable polymer systems we have studied thermoreversible polymer networks composed largely (> 83% w/w) of diethylitaconate of bio-based origin. A series of coating materials has been synthesized consisting of linear chains of diethylitaconate

  1. Synthesis of novel plant oil derivatives: Furan and Diels-Alder reaction products

    Science.gov (United States)

    Plant oils are useful sustainable raw materials for the development of new chemical products. In this work epoxidized soybean oil was treated with different acids, and variable amounts of furan structures were produced from the epoxidized linoleate moiety. From process studies, the highest yields of...

  2. Room-temperature healing of a thermosetting polymer using the Diels-Alder reaction.

    Science.gov (United States)

    Peterson, Amy M; Jensen, Robert E; Palmese, Giuseppe R

    2010-04-01

    Self-healing materials are particularly desirable for load-bearing applications because they offer the potential for increased safety and material lifetimes. A furan-functionalized polymer network was designed that can heal via covalent bonding across the crack surface with the use of a healing agent consisting of a bismaleimide in solution. Average healing efficiencies of approximately 70% were observed. The healing ability of fiber-reinforced composite specimens was investigated with flexural, short beam shear, and double cantilever beam specimens. It was found that solvent amount and maleimide concentration play key roles in determining healing efficiency.

  3. Multistep Synthesis of a Terphenyl Derivative Showcasing the Diels-Alder Reaction

    Science.gov (United States)

    Davie, Elizabeth A. Colby

    2015-01-01

    An adaptable multistep synthesis project designed for the culmination of a second-year organic chemistry laboratory course is described. The target compound is a terphenyl derivative that is an intermediate in the synthesis of compounds used in organic light-emitting devices. Students react a conjugated diene with dimethylacetylene dicarboxylate…

  4. N-O chemistry for antibiotics: discovery of N-alkyl-N-(pyridin-2-yl)hydroxylamine scaffolds as selective antibacterial agents using nitroso Diels-Alder and ene chemistry.

    Science.gov (United States)

    Wencewicz, Timothy A; Yang, Baiyuan; Rudloff, James R; Oliver, Allen G; Miller, Marvin J

    2011-10-13

    The discovery, syntheses, and structure-activity relationships (SAR) of a new family of heterocyclic antibacterial compounds based on N-alkyl-N-(pyridin-2-yl)hydroxylamine scaffolds are described. A structurally diverse library of ∼100 heterocyclic molecules generated from Lewis acid-mediated nucleophilic ring-opening reactions with nitroso Diels-Alder cycloadducts and nitroso ene reactions with substituted alkenes was evaluated in whole cell antibacterial assays. Compounds containing the N-alkyl-N-(pyridin-2-yl)hydroxylamine structure demonstrated selective and potent antibacterial activity against the Gram-positive bacterium Micrococcus luteus ATCC 10240 (MIC(90) = 2.0 μM or 0.41 μg/mL) and moderate activity against other Gram-positive strains including antibiotic resistant strains of Staphylococcus aureus (MRSA) and Enterococcus faecalis (VRE). A new synthetic route to the active core was developed using palladium-catalyzed Buchwald-Hartwig amination reactions of N-alkyl-O-(4-methoxybenzyl)hydroxylamines with 2-halo-pyridines that facilitated SAR studies and revealed the simplest active structural fragment. This work shows the value of using a combination of diversity-oriented synthesis (DOS) and parallel synthesis for identifying new antibacterial scaffolds.

  5. Synthesis of Pyrrolo[1,2-a]pyrimidine Enantiomers via Domino Ring-Closure followed by Retro Diels-Alder Protocol

    Directory of Open Access Journals (Sweden)

    Beáta Fekete

    2017-04-01

    Full Text Available From 2-aminonorbornene hydroxamic acids, a simple and efficient method for the preparation of pyrrolo[1,2-a]pyrimidine enantiomers is reported. The synthesis is based on domino ring-closure followed by microwave-induced retro Diels-Alder (RDA protocols, where the chirality of the desired products is transferred from norbornene derivatives. The stereochemistry of the synthesized compounds was proven by X-ray crystallography. The absolute configuration of the product is determined by the configuration of the starting amino hydroxamic acid.

  6. Synthesis of Pyrrolo[1,2-a]pyrimidine Enantiomers via Domino Ring-Closure followed by Retro Diels-Alder Protocol.

    Science.gov (United States)

    Fekete, Beáta; Palkó, Márta; Haukka, Matti; Fülöp, Ferenc

    2017-04-13

    From 2-aminonorbornene hydroxamic acids, a simple and efficient method for the preparation of pyrrolo[1,2- a ]pyrimidine enantiomers is reported. The synthesis is based on domino ring-closure followed by microwave-induced retro Diels-Alder (RDA) protocols, where the chirality of the desired products is transferred from norbornene derivatives. The stereochemistry of the synthesized compounds was proven by X-ray crystallography. The absolute configuration of the product is determined by the configuration of the starting amino hydroxamic acid.

  7. Synthesis and Reactions of Acenaphthenequinones-Part-2. The Reactions of Acenaphthenequinones

    Directory of Open Access Journals (Sweden)

    Mahmoud Shoukry

    2002-02-01

    Full Text Available The reactions of acenaphthenequinone and its derivatives with different nucleophiles, organic and inorganic reagents are reviewed. This survey also covers their oxidation and reduction reactions, in addition to many known reactions such as Friedel Crafts, Diels-Alder, bromination and thiolation.

  8. Preparation and Reaction Chemistry of Novel Silicon-Substituted 1,3-Dienes

    Directory of Open Access Journals (Sweden)

    Partha P. Choudhury

    2015-09-01

    Full Text Available 2-Silicon-substituted 1,3-dienes containing non transferrable groups known to promote transmetallation were prepared by Grignard chemistry and enyne metathesis. These dienes participated in one pot metathesis/Diels-Alder reactions in regio- and diastereoselective fashions. Electron-rich alkenes showed the fastest rates in metathesis reactions, and ethylene, a commonly used metathesis promoter slowed enyne metathesis. 2-Pyridyldimethylsilyl and 2-thienyldimethylsilyl substituted Diels-Alder cycloadducts participated in cross-coupling chemistry and the 2-thienyldimethylsilyl substituted cycloadducts underwent cross-coupling under very mild reaction conditions.

  9. Carbohydrate carbocyclization by a zinc-mediated tandem reaction and ring-closing enyne metathesis

    DEFF Research Database (Denmark)

    Poulsen, Carina Storm; Madsen, Robert

    2002-01-01

    reaction, an amino group can be introduced in the 1,7-enyne products. Addition of 2-TMS-ethynylcerium(III) chloride after the reductive ring-opening produces the corresponding 1,6-enynes. Further annulation of the product 1,3-dienes can be achieved through a Diels-Alder reaction with good control of stereo...

  10. Iptycenes with an acridinone motif developed through [4+2] cycloaddition of tethered naphthalene and iminoquinone via a radical reaction.

    Science.gov (United States)

    Raju, Selvam; Annamalai, Pratheepkumar; Chen, Pei-Ling; Liu, Yi-Hung; Chuang, Shih-Ching

    2017-06-06

    A new class of iptycenes was developed by combining 2-(naphthalen-1-yl)anilines and p-benzoquinones through copper(ii)-mediated radical cyclisation. This unusual cyclisation reaction resulted in the robust and efficient syntheses of iptycenes with an acridinone motif. These iptycenes can be further transformed into planar acridinone heterocyclics through the Diels-Alder reaction.

  11. The Nitrosocarbonyl Hetero-Diels–Alder Reaction as a Useful Tool for Organic Syntheses

    Science.gov (United States)

    Bodnar, Brian S.

    2014-01-01

    Organic transformations that result in the formation of multiple covalent bonds within the same reaction are some of the most powerful tools in synthetic organic chemistry. Nitrosocarbonyl hetero-Diels–Alder (HDA) reactions allow for the simultaneous stereospecific introduction of carbon–nitrogen and carbon–oxygen bonds in one synthetic step, and provide direct access to 3,6-dihydro-1,2-oxazines. This Review describes the development of the nitrosocarbonyl HDA reaction and the utility of the resulting oxazine ring in the synthesis of a variety of important, biologically active molecules. PMID:21520360

  12. Development of Green and Sustainable Chemical Reactions

    DEFF Research Database (Denmark)

    Taarning, Esben

    Abstract This thesis entitled Development of Green and Sustainable Chemical Reactions is divided into six chapters involving topics and projects related to green and sustainable chemistry. The chapters can be read independently, however a few concepts and some background information is introduced...... as well as the possibility for establishing a renewable chemical industry is discussed. The development of a procedure for using unsaturated aldehydes as olefin synthons in the Diels- Alder reaction is described in chapter three. This procedure affords good yields of the desired Diels- Alder adducts...... in chapter one and two which can be helpful to know when reading the subsequent chapters. The first chapter is an introduction into the fundamentals of green and sustainable chemistry. The second chapter gives an overview of some of the most promising methods to produce value added chemicals from biomass...

  13. Stereo- and regioselectivity of the hetero-Diels–Alder reaction of nitroso derivatives with conjugated dienes

    Directory of Open Access Journals (Sweden)

    Lucie Brulíková

    2016-09-01

    Full Text Available The hetero-Diels–Alder reaction between a nitroso dienophile and a conjugated diene to give the 3,6-dihydro-2H-1,2-oxazine scaffold is useful for the synthesis of many biologically interesting molecules due to the diverse opportunities created by subsequent transformations of the resulting 1,2-oxazine ring. This review discusses the rationale for the observed regio- and stereoselectivity and the methods developed in recent years used to control and improve the stereo- and regioselectivity for the synthesis of 1,2-oxazine scaffolds.

  14. Hetero-Diels–Alder reactions of hetaryl and aryl thioketones with acetylenic dienophiles

    Directory of Open Access Journals (Sweden)

    Grzegorz Mlostoń

    2015-04-01

    Full Text Available Selected hetaryl and aryl thioketones react with acetylenecarboxylates under thermal conditions in the presence of LiClO4 or, alternatively, under high-pressure conditions (5 kbar at room temperature yielding thiopyran derivatives. The hetero-Diels–Alder reaction occurs in a chemo- and regioselective manner. The initially formed [4 + 2] cycloadducts rearrange via a 1,3-hydrogen shift sequence to give the final products. The latter were smoothly oxidized by treatment with mCPBA to the corresponding sulfones.

  15. Studies on the Diels-Alder adduct from cyclopentadiene and p-benzoquinone: Biotransformation, enantiomeric excess and absolute configuration

    Directory of Open Access Journals (Sweden)

    Felipe Camargo Braga

    2012-06-01

    Full Text Available The use of microorganisms or isolated enzymes in synthetic routes has been extensively used by industry and academic research. A great advantage of biotransformation in a synthetic route is highly regio- and enatiosselective control, which can be achieved through microbial catalyzed reaction. Biotransformation is one of the most efficient methods in a production of high purity optical compounds and development of efficient routes for target molecules. Biotransformation by Mucor ramosissimus of enedione 1 gave the keto-alcohol (--2 with enantiomeric excess (ee>99,9% (determined by 1H NMR with [(+-Eu(hfc]3 and their epimer (--3. Determination of the absolute configuration of epimer (--3 was accomplished by controlled reaction and measuring of optical rotation (scheme 1. The fungus M. ramosissimus is a promising species to perform desymmetrization of diketones with high enantioselectivity.

  16. Effects of Surfactants on the Rate of Chemical Reactions

    Directory of Open Access Journals (Sweden)

    B. Samiey

    2014-01-01

    Full Text Available Surfactants are self-assembled compounds that depend on their structure and electric charge can interact as monomer or micelle with other compounds (substrates. These interactions which may catalyze or inhibit the reaction rates are studied with pseudophase, cooperativity, and stoichiometric (classical models. In this review, we discuss applying these models to study surfactant-substrate interactions and their effects on Diels-Alder, redox, photochemical, decomposition, enzymatic, isomerization, ligand exchange, radical, and nucleophilic reactions.

  17. Concerted and stepwise mechanisms in cycloaddition reactions: potential surfaces and isotope effects

    International Nuclear Information System (INIS)

    Houk, K.N.; Yi Li; Storer, Joey; Raimondi, Laura; Beno, Brett

    1994-01-01

    CASSCF/6-31G * calculations have been performed on concerted and stepwise Diels-Alder reactions of butadiene with ethene, the dimerization of butadiene, and the dimerization of cyclobutadiene. The relative energies of concerted and stepwise mechanisms are compared, and the factors influencing these ''energies of concert'' are discussed. The comparison of calculated isotope effects to experimental data provides support for theoretical results. (Author)

  18. A Thermal Dehydrogenative Diels–Alder Reaction of Styrenes for the Concise Synthesis of Functionalized Naphthalenes

    Science.gov (United States)

    Kocsis, Laura S.; Benedetti, Erica

    2012-01-01

    Functionalized naphthalenes are valuable building blocks in many important areas. A microwave-assisted, intramolecular dehydrogenative Diels-Alder reaction of styrenyl derivatives to provide cyclopenta[b]naphthalene substructures not previously accessible using existing synthetic methods is described. The synthetic utility of these uniquely functionalized naphthalenes was demonstrated by a single-step conversion of one of these cycloadducts to a fluorophore bearing a structural resemblance to Prodan. PMID:22913473

  19. The discovery of pyridinium 1,2,4-triazines with enhanced performance in bioconjugation reactions

    Czech Academy of Sciences Publication Activity Database

    Siegl, Sebastian J.; Dzijak, Rastislav; Vázquez, Arcadio; Pohl, Radek; Vrábel, Milan

    2017-01-01

    Roč. 8, č. 5 (2017), s. 3593-3598 ISSN 2041-6520 R&D Projects: GA ČR GJ15-06020Y Institutional support: RVO:61388963 Keywords : Diels-Alder reactions * trans-cyclooctene ligation * living cells Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 8.668, year: 2016 http://pubs.rsc.org/en/content/articlehtml/2017/sc/c6sc05442k

  20. Diastereoselective Synthesis of Novel Heterocyclic Scaffolds through Tandem Petasis 3-Component/Intramolecular Diels-Alder and ROM-RCM Reactions

    DEFF Research Database (Denmark)

    Ishøy, Mette; Petersen, Rico; Petersen, Michael Åxman

    2017-01-01

    A high-yielding, stereoselective and extraordinarily complexity generatingPetasis 3-component/intramolecular Diels-Alderreaction has been developed. In combination with ROM-RCM, rapid access to complex sp3-rich heterocyclic scaffolds amenableto subsequent functionalization and library synthesis...

  1. Microwaves in chemistry: Another way of heating reaction mixtures

    Science.gov (United States)

    Berlan, J.

    1995-04-01

    The question of a possible "microwave activation" of chemical reaction is discussed. In fact two cases should be distinguished: homogeneous or heterogeneous reaction mixtures. In homogeneous mixtures there are no (or very low) rate enhancements compared to a conventional heating, but some influence on chemioselectivity has been observed. These effects derive from fast and mass heating of microwaves, and probably, especially under reflux, from different boiling rates and/or overheating. With heterogeneous mixtures non conventional effects probably derive from mass heating and selective overheating. This is illustrated with several reactions: Diels-Alder, naphthalene sulphonation, preparation of cyanuric acid, hydrolysis of nitriles, transposition reaction on solid support.

  2. Fundamental understanding of oxygen reduction and reaction behavior and developing high performance and stable hetero-structured cathodes

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Xingbo [West Virginia Univ., Morgantown, WV (United States)

    2016-11-14

    New unique hetero-structured cathode has been developed in this project. La2NiO4+δ (LNO) as a surface catalyst with interstitial oxygen defects was introduced onto the state-of-the-art (La0.6Sr0.4)0.95Co0.2Fe0.8O3-δ (LSCF) cathode to enhance the surface-limited ORR kinetics on SOFC cathode. Furthermore, the hetero-structured cathode surface maintains high activity under electrode polarization with much less negative effects from surface cation segregation of Sr, which is known to cause degradation issues for conventional LSCF and LSC cathodes, thus improving the cathode long-term stability. The interface chemistry distribution and oxygen transport properties have been studied to prove the enhancement of power out and stability of LNO-infiltrated LSCF cathode. The further investigation demonstrates that CeO2 & La2-xNiO4+δ (x=0-0.2) co-infiltration is a simple and cost-effective method to improve both performance and stability of LSCF cathode by limiting nano-particles growth/delamination and further improve the surface stability. For the first time, a physical model is proposed to illustrate how unique interstitial species on hetero-structured cathode surface work to regulate the exchange rate of the incorporation reaction. Meanwhile, fundamental investigation of the surface oxygen exchange and bulk oxygen transport properties under over-potential conditions across cathode materials have been carried out in this project, which were discussed and compared to the Nernst equation that is generally applied to treat any oxide electrodes under equilibrium.

  3. Author Details

    African Journals Online (AJOL)

    Singh, P. Vol 66 (2013) - Articles Conformational Preferences of Amphibian Peptides Brevinin-Ya and Brevinin-Yb Explored Using Molecular Dynamics Abstract PDF PDF · Vol 62 (2009) - Articles Computational and Experimental Studies on the Hetero-Diels-Alder Reactions of Cross-conjugated Enaminones with Sulphene

  4. Cycloadditions of ketene acetals under microwave irradiation in solvent-free conditions

    International Nuclear Information System (INIS)

    Diaz-Ortiz, A.; Diez-Barra, E.; La Hoz, A. De; Prieto, P.; Moreno, A.

    1994-01-01

    When subjected to microwave irradiation ketene acetals undergo 1.3-dipolar and hetero-Diels-Alder cycloadditions within 5-12 min to give excellent yields of easily purified heterocyclic products. This efficient and rapid synthesis has the advantage of employing milder reaction conditions than those of classical thermal heating. (author)

  5. Forthcoming Articles

    Indian Academy of Sciences (India)

    NPadmaja

    2018-05-03

    May 3, 2018 ... bridged-atom in the formation of polysubstituted pyridines via. Hetero-Diels-Alder reaction of isotellurazoles with acetylenic dienophiles: A molecular electron density study abdo benallou abdo_benallou@yahoo.fr. Universite Chouaib. Doukkali safi. Morocco. 02 Apr. 34. JULY Spl. Issue-. MTIC. JCSC-D-18-.

  6. Activation-Strain Analysis Reveals Unexpected Origin of Fast Reactivity in Heteroaromatic Azadiene Inverse-Electron-Demand Diels-Alder Cycloadditions

    NARCIS (Netherlands)

    Talbot, Austin; Devarajan, Deepa; Gustafson, Samantha J.; Fernandez, Israel; Bickelhaupt, F. Matthias; Ess, Daniel H.

    2014-01-01

    Heteroaromatic azadienes, especially 1,2,4,5-tetrazines, are extremely reactive partners with alkenes in inverse-electron-demand Diels–Alder reactions. Azadiene cycloaddition reactions are used to construct heterocycles in synthesis and are popular as bioorthogonal reactions. The origin of fast

  7. Pericyclic reactions in an aqueous molecular flask.

    Science.gov (United States)

    Murase, Takashi; Fujita, Makoto

    2010-10-01

    A self-assembled molecular flask with a nanometer-sized restricted cavity offers a new reaction environment that is quite different from the bulk solution. The self-assembled cage accommodates a pair of hydrophobic molecules to perform unusual Diels-Alder reactions and [2+2] photoadditions of otherwise unreactive aromatic molecules. In this cage, for example, the Diels-Alder reaction of naphthalene proceeds smoothly under mild conditions, and aceanthrylene shows reactivity for both [2+2] and [2+4] cycloadditions via the identical ternary host-guest complex. The observed greatly enhanced reactivity stems from the increased local concentration and pre-organization of the substrate pair within the cage, which reduces the entropic cost and switches the reaction profile from a bimolecular to a pseudo-intramolecular reaction pathway. The reinforced orientation and arrangement of substrate pairs specify regio- and stereo-selectivities of the subsequent reactions in the cavity. Chiral auxiliaries outside the cage create the inner chiral environment and induce asymmetric reactions inside the cage (up to 50% ee). © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc.

  8. Organometallic Reactions Development, Mechanistic Studies and Synthetic Applications

    DEFF Research Database (Denmark)

    Dam, Johan Hygum

    of the successful total synthesis of the cyclophane cavicularin, which contains a bent aromatic moiety. The pivotal step in the synthesis embodied a pyrone-alkyne Diels-Alder cycloaddition with CO2-extrusion to deliver the bent aromatic residue. The fourth project involved further development of the conditions...... previously discovered in the Madsen group for the direct coupling of alcohols and amines to amides under dihydrogen liberation. The goal was to synthesize isolatable ruthenium catalysts and two 18-electron complexes capable of performing the reaction in excellent yields were prepared and characterized...

  9. Synthesis and Intramolecular [4+2] Cycloaddition Reactions of 4-Pyridazinecarbonitriles with Alkyne Side Chains

    Directory of Open Access Journals (Sweden)

    Norbert Haider

    1998-01-01

    Full Text Available The preparation of a series of new 3-(alkynyl-X-substituted 4-pyridazinecarbonitriles 2-5 (X = O, NH is described. The compounds are shown to undergo thermally induced intramolecular Diels-Alder reactions with inverse electron demand, affording the fused benzonitriles 6-8. Incorporation of a 1,2-phenylene unit into the side chain, as in the case of compounds 10 and 13, results in a more favorable conformation of the dienophilic substructure and thus to a pronounced acceleration of the [4+2] cycloaddition reaction.

  10. Borostannylation of Alkynes and Enynes. Scope and Limitations of the Reaction and Utility of the Adducts

    Science.gov (United States)

    Singidi, Ramakrishna Reddy; RajanBabu, T. V.

    2010-01-01

    The utility of the bis-metallating reagent 1,3-dimethyl-2-trimethylstannyl-2-bora-1,3-diazacyclopentane (1) has not been fully realized because of the hydrolytic instability of the products derived from catalyzed vicinal syn-additions to alkynes. The isolation of variety of such adducts derived from alkynes (and also from hitherto unreported additions to 1,3-enynes) as stable boron pinacolates is reported. Examples of the applications of resulting products in tandem cross-coupling reactions and as dienes in Diels-Alder reactions are illustrated. PMID:20459076

  11. Mineralization of hetero bi-functional reactive dye in aqueous solution by Fenton and photo-Fenton reactions.

    Science.gov (United States)

    Torrades, Francesc; García-Hortal, José Antonio; García-Montaño, Julia

    2015-01-01

    This study focused on the advanced oxidation of the hetero bi-functional reactive dye Sumifix Supra Yellow 3RF (CI Reactive Yellow 145) using dark Fenton and photo-Fenton conditions in a lab-scale experiment. A 2(3) factorial design was used to evaluate the effects of the three key factors: temperature, Fe(II) and H2O2 concentrations, for a dye concentration of 250 mg L(-1) with chemical oxygen demand (COD) of 172 mg L(-1) O2 at pH=3. The response function was the COD reduction. This methodology lets us find the effects and interactions of the studied variables and their roles in the efficiency of the treatment process. In the optimization, the correlation coefficients for the model (R2) were 0.948 and 0.965 for Fenton and photo-Fenton treatments, respectively. Under optimized reaction conditions: pH=3, temperature=298 K, [H2O2]=11.765 mM and [Fe(II)]=1.075 mM; 60 min of treatment resulted in a 79% and 92.2% decrease in COD, for the dye taken as the model organic compound, after Fenton and photo-Fenton treatments, respectively.

  12. Hetero-atom doped carbon nanotubes for dye degradation and oxygen reduction reaction

    Energy Technology Data Exchange (ETDEWEB)

    Nandan, Ravi, E-mail: aerawat27@gmail.com; Nanda, Karuna Kar [Materials Research Centre, Indian Institute of Science, Bangalore-560012 (India)

    2015-06-24

    We report the synthesis of nitrogen doped vertically aligned multi-walled (MWNCNTs) carbon nanotubes by pyrolysis and its catalytic performance for degradation of methylene blue (MB) dye & oxygen reduction reaction (ORR). The degradation of MB was monitored spectrophotometrically with time. Kinetic studies show the degradation of MB follows a first order kinetic with rate constant k=0.0178 min{sup −1}. The present rate constant is better than that reported for various supported/non-supported semiconducting nanomaterials. Further ORR performance in alkaline media makes MWNCNTs a promising cost-effective, fuel crossover tolerance, metal-free, eco-friendly cathode catalyst for direct alcohol fuel cell.

  13. Synthesis and mechanism of formation of oxadeazaflavines by microwave thermal cyclization of ortho-halobenzylidene barbiturates

    Energy Technology Data Exchange (ETDEWEB)

    Figueroa-Villar, J. Daniel; Oliveira, Sandra C.G. de, E-mail: figueroa@ime.eb.br [Grupo de Quimica Medicinal, Departamento de Quimica, Instituto Militar de Engenharia, Rio de Janeiro, RJ (Brazil)

    2011-09-15

    The thermal cyclization reaction of o-halobenzylidene barbiturates was developed as an efficient and simple method for the preparation of oxadeazaflavines. The use of solid state reaction conditions with microwave irradiation afforded the products in 5 min with 47 to 98% yield. Experimental synthetic results and thermogravimetric reaction analyses agree with the molecular modeling mechanism simulation, indicating that this reaction occurs through an intramolecular hetero-Diels-Alder cyclization followed by fast re-aromatization. (author)

  14. Oxidative cycloaddition of hydroxamic acids with dienes or guaiacols mediated by iodine(III) reagents.

    Science.gov (United States)

    Shimizu, Hisato; Yoshimura, Akira; Noguchi, Keiichi; Nemykin, Victor N; Zhdankin, Viktor V; Saito, Akio

    2018-01-01

    [Bis(trifluoroacetoxy)iodo]benzene (BTI) and (diacetoxyiodo)benzene (DIB) efficiently promote the formation of acylnitroso species from hydroxamic acids in the presence of various dienes to give the corresponding hetero-Diels-Alder (HDA) adducts in moderate to high yields. The present method could be applied to the HDA reactions of acylnitroso species with o -benzoquinones generated by the oxidative dearomatization of guaiacols.

  15. π-Bond Screening in Benzonorbornadienes: The Role of 7-Substituents in Governing the Facial Selectivity for the Diels-Alder Reaction of Benzonorbornadienes with 3,6-Di(2-pyridyl-s-Tetrazine

    Directory of Open Access Journals (Sweden)

    Peter A. Harrison

    2001-03-01

    Full Text Available Benzonorbornadiene 21, 7-spirocyclopropylbenzonorbornadiene 23, 7,7-dimethylbenzonorbornadiene 25, and 7-spirocyclopentylbenzonorbornadiene 27 have been reacted with 3,6-di(2-pyridyl-s-tetrazine (rate: 21>23>25=27 to form symmetrical 4,5-dihydropyridazines which are stable towards fragmentation but rearrange with varying facility to their 1,4 isomers. The facial selectivity of attack on the π-bond changes from exo-attack for 21 and 23 to endo-attack for 25 and 27. The 7-spirocyclopropyl benzonorbornadiene 23 typically forms a mixture of dihydropyridazines with exo-stereochemistry, which undergo further stereochemical isomerisation to an exo-fused product upon acetylation (acetyl chloride in hot pyridine. Oxidation with DDQ of the dihydropyridazines individually or as mixtures gives the corresponding fused 3,6-di(2-pyridylpyridazines.

  16. Iptycene synthesis: A new method for attaching a 2,3-anthracene moiety to the 9,10-positions of another anthracene moiety - Exceptional conditions for a Lewis acid catalyzed Diels-Alder reaction

    Science.gov (United States)

    Chen, Yong-Shing; Hart, Harold

    1989-01-01

    An efficient three-step method for appending a 2,3-anthracene moiety to the 9,10-positions of an existing anthracene moiety is described. The first step uses excess 1,4-anthraquinone (3 equiv) and aluminum chloride (6 equiv) to obtain the anthracene-quinone cycloadduct (omission of the AlCl3 resulted in no adduct). The resulting diketone was reduced to the corresponding diol (excess LiAlH4), which was dehydrated to the arene with phosphorus oxychloride and pyridine. Specific examples include the preparation of heptipycene 8 from pentiptycene 6 (66 percent overall yield) and a similar conversion of 8 to the noniptycene 13 (75 percent overall yield). The methodology led to a markedly improved synthesis of tritriptycene 9 and the first synthesis of undecaiptycene 14.

  17. Insight into organic reactions from the direct random phase approximation and its corrections

    Energy Technology Data Exchange (ETDEWEB)

    Ruzsinszky, Adrienn [Department of Physics, Temple University, Philadelphia, Pennsylvania 19122 (United States); Zhang, Igor Ying; Scheffler, Matthias [Fritz-Haber-Institut der Max-Planck-Gesellschaft, Faradayweg 4-6, 14195 Berlin (Germany)

    2015-10-14

    The performance of the random phase approximation (RPA) and beyond-RPA approximations for the treatment of electron correlation is benchmarked on three different molecular test sets. The test sets are chosen to represent three typical sources of error which can contribute to the failure of most density functional approximations in chemical reactions. The first test set (atomization and n-homodesmotic reactions) offers a gradually increasing balance of error from the chemical environment. The second test set (Diels-Alder reaction cycloaddition = DARC) reflects more the effect of weak dispersion interactions in chemical reactions. Finally, the third test set (self-interaction error 11 = SIE11) represents reactions which are exposed to noticeable self-interaction errors. This work seeks to answer whether any one of the many-body approximations considered here successfully addresses all these challenges.

  18. Insight into organic reactions from the direct random phase approximation and its corrections

    International Nuclear Information System (INIS)

    Ruzsinszky, Adrienn; Zhang, Igor Ying; Scheffler, Matthias

    2015-01-01

    The performance of the random phase approximation (RPA) and beyond-RPA approximations for the treatment of electron correlation is benchmarked on three different molecular test sets. The test sets are chosen to represent three typical sources of error which can contribute to the failure of most density functional approximations in chemical reactions. The first test set (atomization and n-homodesmotic reactions) offers a gradually increasing balance of error from the chemical environment. The second test set (Diels-Alder reaction cycloaddition = DARC) reflects more the effect of weak dispersion interactions in chemical reactions. Finally, the third test set (self-interaction error 11 = SIE11) represents reactions which are exposed to noticeable self-interaction errors. This work seeks to answer whether any one of the many-body approximations considered here successfully addresses all these challenges

  19. Poly(2-vinyl pyridine)-block-poly(ethylene oxide) featuring a furan group at the block junction-synthesis and functionalization.

    Science.gov (United States)

    Rudolph, Tobias; Barthel, Markus J; Kretschmer, Florian; Mansfeld, Ulrich; Hoeppener, Stephanie; Hager, Martin D; Schubert, Ulrich S; Schacher, Felix H

    2014-05-01

    Furfuryl glycidyl ether (FGE) represents a highly versatile monomer for the preparation of reversibly cross-linkable nanostructured materials via Diels-Alder reactions. Here, the use of FGE for the mid-chain functionalization of a P2VP-b-PEO diblock copolymer is reported. The material features one furan moiety at the block junction, P2VP68 -FGE-b-PEO390 , which can be subsequently addressed in Diels-Alder reactions using maleimide-functionalized counterparts. The presence of the FGE moiety enables the introduction of dyes as model labels or the formation of hetero-grafted brushes as shell on hybrid Au@Polymer nanoparticles. This renders P2VP68 -FGE-b-PEO390 , a powerful tool for selective functionalization reactions, including the modification of surfaces. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Study of the Deformation/Interaction Model: How Interactions Increase the Reaction Barrier

    Directory of Open Access Journals (Sweden)

    Zhiling Liang

    2018-01-01

    Full Text Available The interactions (including weak interactions between dienophiles and dienes play an important role in the Diels-Alder reaction. To elucidate the influence of these interactions on the reactivity, a popular DFT functional and a variational DFT functional corrected with dispersion terms are used to investigate different substituent groups incorporated on the dienophiles and dienes. The bond order is used to track the trajectory of the cycloaddition reaction. The deformation/interaction model is used to obtain the interaction energy from the reactant complex to the inflection point until reaching the saddle point. The interaction energy initially increases with a decrease in the interatomic distance, reaching a maximum value, but then decreases when the dienophiles and dienes come closer. Reduced density gradient and chemical energy component analysis are used to analyse the interaction. Traditional transition state theory and variational transition state theory are used to obtain the reaction rates. The influence of tunneling on the reaction rate is also discussed.

  1. Synthesis of Taxol-Like Prostate Cancer Chemotherapeutic Agents

    National Research Council Canada - National Science Library

    Jo, Hyunil

    2008-01-01

    This report describes the synthetic approaches toward a potent microtubule stabilizing natural product, eleutherobin, utilizing tandem Diels-Alder reaction/Grob-type fragmentation reaction as key steps...

  2. Bonds broken and formed during the mixed-linkage glucan : xyloglucan endotransglucosylase reaction catalysed by Equisetum hetero-trans-β-glucanase.

    Science.gov (United States)

    Simmons, Thomas J; Fry, Stephen C

    2017-03-08

    Mixed-linkage glucan∶xyloglucan endotransglucosylase (MXE) is one of the three activities of the recently characterised hetero-trans-β-glucanase (HTG), which among land plants is known only from Equisetum species. The biochemical details of the MXE reaction were incompletely understood - details that would promote understanding of MXE's role in vivo and enable its full technological exploitation. We investigated HTG's site of attack on one of its donor substrates, mixed-linkage (1→3),(1→4)-β-d-glucan (MLG), with radioactive oligosaccharides of xyloglucan as the acceptor substrate. Comparing three different MLG preparations, we showed that the enzyme favours those with a high content of cellotetraose blocks. The reaction products were analysed by enzymic digestion, thin-layer chromatography (TLC), high-pressure liquid chromatography (HPLC) and gel-permeation chromatography (GPC). Equisetum HTG consistently cleaved the MLG at the third consecutive β-(1→4)-bond following (towards the reducing terminus) a β-(1→3)-bond. It then formed a β-(1→4)-bond between the MLG and the non-reducing terminal glucose residue of the xyloglucan oligosaccharide, consistent with its xyloglucan endotransglucosylase/hydrolase subfamily membership. Using size-homogeneous barley MLG as the donor substrate, we showed that HTG does not favour any particular region of the MLG chain relative to the polysaccharide's reducing and non-reducing termini; rather, it selects its target cellotetraosyl unit stochastically along the MLG molecule. This work improves our understanding of how enzymes can exhibit promiscuous substrate specificities and provides the foundations to explore strategies for engineering novel substrate specificities into transglycanases. © 2017 The Author(s).

  3. Thermal replacement reaction: a novel route for synthesizing eco-friendly ZnO@γ-In2Se3 hetero-nanostructures by replacing cadmium with indium and their photoelectrochemical and photocatalytic performances.

    Science.gov (United States)

    Zhang, Zhuo; Choi, Mingi; Baek, Minki; Yong, Kijung

    2015-05-21

    A novel route called thermal replacement reaction was demonstrated for synthesizing eco-friendly ZnO@γ-In2Se3 hetero-structural nanowires on FTO glass by replacing the element cadmium with indium for the first time. The indium layer was coated on the surface of the ZnO nanowires beforehand, then CdSe quantum dots were deposited onto the coated indium layer, and finally the CdSe quantum dots were converted to γ-In2Se3 quantum dots by annealing under vacuum at 350 °C for one hour. The prepared ZnO@γ-In2Se3 hetero-nanostructures exhibit stable photoelectrochemical properties that can be ascribed to the protection of the In2O3 layer between the ZnO nanowire and γ-In2Se3 quantum dots and better photocatalytic performance in the wide wavelength region from 400 nm to nearly 750 nm. This strategy for preparing the ZnO@γ-In2Se3 hetero-nanostructures not only enriches our understanding of the single replacement reaction where the active element cadmium can be replaced with indium, but also opens a new way for the in situ conversion of cadmium-based to eco-friendly indium-based nano-devices.

  4. Investigation of Thermochemistry Associated with the Carbon–Carbon Coupling Reactions of Furan and Furfural Using ab Initio Methods

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Cong; Assary, Rajeev S.; Curtiss, Larry A.

    2014-06-26

    Upgrading of furan and small oxygenates obtained from the decomposition of cellulosic materials via formation of carbon-carbon bonds is critical to effective conversion of biomass to liquid transportation fuels. Simulation-driven molecular level understanding of carbon-carbon bond formation is required to design efficient catalysts and processes. Accurate quantum chemical methods are utilized here to predict the reaction energetics for conversion of furan (C4H4O) to C5-C8 ethers and the transformation of furfural (C5H6O2) to C13-C26 alkanes. Furan, can be coupled with various C1 to C4 lower molecular weight carbohydrates obtained from the pyrolysis via Diels-Alder type reactions in the gas phase to produce C5-C8 cyclic ethers. The computed reaction barriers for these reactions (~25 kcal/mol) are lower than the cellulose activation or decomposition reactions (~50 kcal/mol). Cycloaddition of C5-C8 cyclo-ethers with furans can also occur in the gas phase, and the computed activation energy is similar to that of the first Diels-Alder reaction. Furfural, obtained from biomass, can be coupled with aldehydes or ketones with α-hydrogen atoms to form longer chain aldol products and these aldol products can undergo vapor phase hydrocycloaddition (activation barrier of ~20 kcal/mol) to form the precursors of C26 cyclic hydrocarbons. These thermochemical studies provide the basis for further vapor phase catalytic studies required for upgrading of furans/furfurals to longer chain hydrocarbons.

  5. Selective Production of Renewable para-Xylene by Tungsten Carbide Catalyzed Atom-Economic Cascade Reactions.

    Science.gov (United States)

    Dai, Tao; Li, Changzhi; Li, Lin; Zhao, Zongbao Kent; Zhang, Bo; Cong, Yu; Wang, Aiqin

    2018-02-12

    Tungsten carbide was employed as the catalyst in an atom-economic and renewable synthesis of para-xylene with excellent selectivity and yield from 4-methyl-3-cyclohexene-1-carbonylaldehyde (4-MCHCA). This intermediate is the product of the Diels-Alder reaction between the two readily available bio-based building blocks acrolein and isoprene. Our results suggest that 4-MCHCA undergoes a novel dehydroaromatization-hydrodeoxygenation cascade process by intramolecular hydrogen transfer that does not involve an external hydrogen source, and that the hydrodeoxygenation occurs through the direct dissociation of the C=O bond on the W 2 C surface. Notably, this process is readily applicable to the synthesis of various (multi)methylated arenes from bio-based building blocks, thus potentially providing a petroleum-independent solution to valuable aromatic compounds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Liquid state sup1H and sup13C-NMR studies on polymerisation reaction of 2,2'-difurfuryloxy-2- silapropane

    International Nuclear Information System (INIS)

    Rusli bin Omar

    1994-01-01

    The purpose of this study was to prepare the copolymer of 2,2'-difurfuryloxy-2-silapropane (DFS) and 1,1'-(methylenedi-4, 1-phenylene) bismaleimide (BM). DFS was prepared at 0 degC through the reaction of 2 moles of furfuryl alcohol (FA) with 1 mole of dichlorodimethylsilane (DCMS) in the presence of pyridine and chloroform as a solvent. The formation of this compound was characterized by the sup1H and sup13C-NMR spectroscopy and mass spectrometry. DFS has the ability to undergo the Diels-Alder reaction. The furan end groups of DFS could react with dienophile groups of other materials. The adduct of DFS-BM was prepared by the reaction of DFS with BM at room temperature (18degC) in chloroform (CDClsub3). Characterization of the adduct was carried out through a study of the sup1H and sup13C-NMR spectra of the adduct

  7. Cycloadditions in mixed aqueous solvents : the role of the water concentration

    NARCIS (Netherlands)

    Rispens, Theo; Engberts, Jan B. F. N.

    We examined the kinetics of a series of cycloaddition reactions in mixtures of water with methanol, acetonitrile and poly(ethylene glycol) (MW 1000). The reactions include the Diels-Alder (DA) reaction between cyclopentadiene and N-n-butylmaleimide or acridizinium bromide, the retro-Diels-Alder

  8. phenylalanine and l-tyrosine as chiral micellar media for the cat

    African Journals Online (AJOL)

    potential chiral micellar catalysts for the Diels-Alder reaction between methyl acrylate and .... hydrophobic effects, electrostatic interactions and the accompanying medium effects. In the case .... liquids as effective organocatalysts for Diels-Alder reaction. Green Chem. 2014, 16 .... Colloids and Surfaces A: Physicochem.

  9. An Asymmetric Synthetic Approach to the A-ring of the Taxol Family of Anti-Cancer Compounds

    Directory of Open Access Journals (Sweden)

    M. L. Marin

    1998-02-01

    Full Text Available A synthetic route developed for the preparation of the A-ring of Taxol family of molecules is reported. By means of an intramolecular Diels-Alder reaction an asymmetric approach to this ring has been accomplished. Also, initial studies to prepare the A ring using an intramolecular Diels-Alder reaction have been successful.

  10. Thermally Self-Healing Polymeric Materials : The Next Step to Recycling Thermoset Polymers?

    NARCIS (Netherlands)

    Zhang, Youchun; Broekhuis, Antonius A.; Picchioni, Francesco

    2009-01-01

    We developed thermally self-healing polymeric materials on the basis of furan-functionalized, alternating thermosetting polyketones (PK-furan) and bis-maleimide by using the Diels-Alder (DA) and Retro-Diels-Alder (RDA) reaction sequence. PK-furan can be easily obtained under mild conditions by the

  11. Trans-Selective Rhodium Catalysed Conjugate Addition of Organoboron Reagents to Dihydropyranones

    Directory of Open Access Journals (Sweden)

    Hannah J. Edwards

    2015-04-01

    Full Text Available The selective synthesis of 2,6-trans-tetrahydropyran derivatives employing the rhodium catalysed addition of organoboron reagents to dihydropyranone templates, derived from a zinc-catalysed hetero-Diels-Alder reaction, is reported. The addition of both arylboronic acids and potassium alkenyltrifluoroborates have been accomplished in high yields using commercially-available [Rh(cod(OH]2 catalyst. The selective formation of the 2,6-trans-tetrahydropyran stereoisomer is consistent with a mechanism involving alkene association and carbometalation on the less hindered face of the dihydropyranone.

  12. Pd(OAc)2/Ph3P-catalyzed dimerization of isoprene and synthesis of monoterpenic heterocycles.

    Science.gov (United States)

    Kellner, Dominik; Weger, Maximilian; Gini, Andrea; Mancheño, Olga García

    2017-01-01

    The palladium-catalyzed dimerization of isoprene is a practical approach of synthesizing monoterpenes. Though several highly selective methods have been reported, most of them still required pressure or costly ligands for attaining the active system and desired selectivity. Herein, we present a simple and economical procedure towards the tail-to-tail dimer using readily available Pd(OAc) 2 and inexpensive triphenylphosphine as ligand. Furthermore, simple screw cap vials are employed, allowing carrying out the reaction at low pressure. In addition, the potential of the dimer as a chemical platform for the preparation of heterocyclic terpenes by subsequent (hetero)-Diels-Alder or [4 + 1]-cycloadditions with nitrenes is also depicted.

  13. Simulating chemical reactions in ionic liquids using QM/MM methodology.

    Science.gov (United States)

    Acevedo, Orlando

    2014-12-18

    The use of ionic liquids as a reaction medium for chemical reactions has dramatically increased in recent years due in large part to the numerous reported advances in catalysis and organic synthesis. In some extreme cases, ionic liquids have been shown to induce mechanistic changes relative to conventional solvents. Despite the large interest in the solvents, a clear understanding of the molecular factors behind their chemical impact is largely unknown. This feature article reviews our efforts developing and applying mixed quantum and molecular mechanical (QM/MM) methodology to elucidate the microscopic details of how these solvents operate to enhance rates and alter mechanisms for industrially and academically important reactions, e.g., Diels-Alder, Kemp eliminations, nucleophilic aromatic substitutions, and β-eliminations. Explicit solvent representation provided the medium dependence of the activation barriers and atomic-level characterization of the solute-solvent interactions responsible for the experimentally observed "ionic liquid effects". Technical advances are also discussed, including a linear-scaling pairwise electrostatic interaction alternative to Ewald sums, an efficient polynomial fitting method for modeling proton transfers, and the development of a custom ionic liquid OPLS-AA force field.

  14. Vapor phase reactions in polymerization plasma for divinylsiloxane-bis-benzocyclobutene film deposition

    International Nuclear Information System (INIS)

    Kinoshita, Keizo; Nakano, Akinori; Kawahara, Jun; Kunimi, Nobutaka; Hayashi, Yoshihiro; Kiso, Osamu; Saito, Naoaki; Nakamura, Keiji; Kikkawa, Takamaro

    2006-01-01

    Vapor phase reactions in plasma polymerization of divinylsiloxane-bis-benzocyclobutene (DVS-BCB) low-k film depositions on 300 mm wafers were studied using mass spectrometry, in situ Fourier transform infrared, and a surface wave probe. Polymerization via Diels-Alder cycloaddition reaction was identified by the detection of the benzocyclohexene group. Hydrogen addition and methyl group desorption were also detected in DVS-BCB monomer and related large molecules. The dielectric constant k of plasma polymerized DVS-BCB with a plasma source power range up to 250 W was close to ∼2.7 of thermally polymerized DVS-BCB, and increased gradually over 250 W. The electron density at 250 W was about 1.5x10 10 cm -3 . The increase of the k value at higher power was explained by the decrease of both large molecular species via multistep dissociation and incorporation of silica components into the polymer. It was found that the reduction of electron density as well as precursor residence time is important for the plasma polymerization process to prevent the excess dissociation of the precursor

  15. Transparent Ethenylene-Bridged Polymethylsiloxane Aerogels: Mechanical Flexibility and Strength and Availability for Addition Reaction.

    Science.gov (United States)

    Shimizu, Taiyo; Kanamori, Kazuyoshi; Maeno, Ayaka; Kaji, Hironori; Doherty, Cara M; Nakanishi, Kazuki

    2017-05-09

    Transparent, low-density ethenylene-bridged polymethylsiloxane [Ethe-BPMS, O 2/2 (CH 3 )Si-CH═CH-Si(CH 3 )O 2/2 ] aerogels from 1,2-bis(methyldiethoxysilyl)ethene have successfully been synthesized via a sol-gel process. A two-step sol-gel process composed of hydrolysis under acidic conditions and polycondensation under basic conditions in a liquid surfactant produces a homogeneous pore structure based on cross-linked nanosized colloidal particles. Visible-light transmittance of the aerogels varies with the concentration of the base catalyst and reaches as high as 87% (at a wavelength of 550 nm for a 10 mm thick sample). Gelation and aging temperature strongly affect the deformation behavior of the resultant aerogels against uniaxial compression, and the obtained aerogels prepared at 80 °C show high elasticity after being unloaded. This highly resilient behavior is primarily derived from the rigidity of ethenylene groups, which is confirmed by a comparison with other aerogels with similar molecular structures, ethylene-bridged polymethylsiloxane and polymethylsilsesquioxane. Applicability of the addition reaction using a Diels-Alder reaction of benzocyclobutene has also been investigated, revealing that a successful addition takes place on the ethenylene linkings, which is verified using Raman and solid-state NMR spectroscopies. Insights into the effect of molecular structure on mechanical properties and the availability of surface functionalization provided in this study are important for realizing transparent aerogels with the desired functionality.

  16. Fulltext PDF

    Indian Academy of Sciences (India)

    Steps A and G are Diels-Alder reactions. Being 7t 4s+7t2s type processes, they are thermally allowed. Note that the dienophiles are activated due to the presence of carbonyl groups. Step H is a related reaction, occurring in the reverse direction. It is a retro-Diels-Alder reaction. The symmetry rules governing this process are ...

  17. A New Synthesis of Porphyrins with Extended Conjugation and their Photophysics

    National Research Council Canada - National Science Library

    Ono, Noboru

    2005-01-01

    .... These molecules useful non-linear optical and optoelectronic properties. The contractor used a synthesis method based on the retro Diels-Alder reaction of porphyrins fused with bicyclo[2.2.2]octadiene units...

  18. Synthetic studies on taxanes: A domino-enyne metathesis/Diels ...

    Indian Academy of Sciences (India)

    Abstract. A domino enyne cross-metathesis/intramolecular Diels-Alder reaction has been successfully used to synthesize a bicyclo[5.3.1] undecene, corresponding to AB-ring of taxol without the gem dimethyl group.

  19. The oxanorbornene approach to 3-hydroxy, 3,4-dihydroxy and 3,4,5-trihydroxy derivatives of 2-aminocyclohexanecarboxylic acid

    Directory of Open Access Journals (Sweden)

    Howard Judith AK

    2006-05-01

    Full Text Available Abstract The nitro oxanorbornene adduct derived from the Diels-Alder reaction of ethyl (E-3-nitroacrylate and furan provides a versatile template for the stereoselective synthesis of hydroxylated derivatives of 2-aminocyclohexanecarboxylic acid (ACHC.

  20. Unconventional, Chemically Stable, and Soluble Two-Dimensional Angular Polycyclic Aromatic Hydrocarbons: From Molecular Design to Device Applications

    KAUST Repository

    Zhang, Lei; Cao, Yang; Colella, Nicholas S.; Liang, Yong; Bredas, Jean-Luc; Houk, Kendall N.; Briseñ o, Alejandro L.

    2015-01-01

    , longer acenes, which could exhibit even better performance, are susceptible to oxidation, photodegradation, and, in solar cells which contain fullerenes, Diels-Alder reactions. This Account highlights recent advances in the molecular design of two

  1. Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes

    Czech Academy of Sciences Publication Activity Database

    Vida, N.; Václavík, Jiří; Beier, P.

    2016-01-01

    Roč. 12, JAN 20 2016 (2016), s. 110-116 ISSN 1860-5397 Institutional support: RVO:67985840 Keywords : dearomatization * decarboxylation * Diels-Alder reaction Subject RIV: EE - Microbiology, Virology Impact factor: 2.337, year: 2016

  2. Wirtschaftsinformatik fur dummies

    CERN Document Server

    Thesmann, Stephan; Kobayashi, Shu; Jorgensen, Karl Anker

    2015-01-01

    Cycloaddition reactions are among the most important tools for synthesis in organic chemistry, since these reactions are vital to the modern synthesis of natural products and biologically active substances. Metal catalysis plays an increasingly important role in these reactions, often allowing several stereocenters to be selectively created and integrated in the target molecules. Kobayashi and Jorgensen's handbook provides numerous examples of metal-catalyzed reactions, including [2+1], [3+2] and [4+2] cycloadditions. Important reactions such as carbo- and hetero-Diels-Alder, carbocyclic, cyclopropanation and 1,3-dipolar cycloaddition reactions are discussed. A large number of experimental procedures gives a concrete idea of the use of metal-catalyzed cycloaddition reactions in modern synthesis. The book is aimed at chemists in industry or academia, who want to effectively use cycloadditions in their work.

  3. (4+2) Cycloaddition reactions with inverse electron demand of nitrogen bearing, heteroaromatic cations

    International Nuclear Information System (INIS)

    Ritzberger-Baumgartner, W.

    1996-06-01

    Three cationic, heteroaromatic diene-systems (1, 2, 3, 4-tetramethoxycarbonyl-quinolizinium-tetrafluoroborate (M), 8, 9, 10, 11-tetrarnethoxycarbonylpyrido[2,1-a]-isoquinolinium-TFB and triazolo[1,5-b]isoquinolinium-TFBs) and a cationic, non-aromatic diene (2,5,5-trimethyl-3-oxo-1, 2, 4-triazolium-TFB) were synthesized. The dienes were employed successfully in cycloaddition reactions with a number ofconjugated dienophiles (including norbornene). The mechanism underlying these cycloaddition reactions was discussed in the theoretical section. At first quantumchemical calculations of the frontier orbital energies provided the proof, that the reactions followed the pattern of reactions with inverse electron demand. Calculation of the charge distribution and of the orbital coefficients led to the conclusion, that these reactions are mainly orbital controlled. Two mechanistic variants were in discussion. Either the reactions proceed in a concerted manner resembling the Diels-Alder reaction with inverse electron demand or in two distinct steps with the formation of a cationic intermediate following the attack of the heterodienes acting as weak electrophiles at the dienophiles being weak nucleophiles. Calculations of a possible transition state of these cycloaddition reactions revealed a pronounced preference for the formation of the bond between the logical reaction centers in the first step of a two-step reaction. However, experimental and theoretical findings led to the conviction, that cationic polar cycloaddition reactions proceed exactly along the crossroad between a concerted and a two-step mechanism and depending on the electrophilic strength of the diene and the nucleophilic strength of the dienophile these reactions show more characteristics of one of the two mechanistic possibilities. The high regioselectivity as well as the high stereoselectivity could be explained satisfactory with the help of the calculated orbital coefficients. (author)

  4. An unexpected reaction pathway in the synthesis of the ABCE framework of strychnine-type alkaloids - A multidisciplinary study

    Science.gov (United States)

    Šoral, Michal; Markus, Jozef; Doháňošová, Jana; Šoralová, Stanislava; Dvoranová, Dana; Chyba, Andrej; Moncol, Ján; Berkeš, Dušan; Liptaj, Tibor

    2017-01-01

    Acid-catalyzed cyclization of spirocyclic 1‧-benzyl-2‧-(prop-2-en-1-yl)spiro[indole-3,3‧-pyrrolidine]-5‧-one (1) was performed. The pentacyclic product of Povarov-like imino-Diels-Alder reaction was isolated in high yield instead of expected tetracyclic aza-Prins intermediate. The unusual exotic alkaloid-type structure of the resulting molecule 2 was unambiguously confirmed by a detailed NMR analysis using a set of 2D NMR spectra including an INADEQUATE experiment. The relative configuration of 2 was predicted from the synthesis mechanism and DFT geometry calculations and independently confirmed using NOESY and residual dipolar coupling (RDC) assisted NMR analysis in stretched crosslinked polystyrene gels. The reversibility of the cycloaddition in aprotic solvents was observed. A new reaction pathway yielding a rare 6-5-5-5 tetracyclic spiroindoline 3 was suggested. The relative configuration within the tetracyclic framework was ultimately proved using Single-crystal X-ray diffraction analysis of compound 4.

  5. Light-Induced C-H Arylation of (Hetero)arenes by In Situ Generated Diazo Anhydrides.

    Science.gov (United States)

    Cantillo, David; Mateos, Carlos; Rincon, Juan A; de Frutos, Oscar; Kappe, C Oliver

    2015-09-07

    Diazo anhydrides (Ar-N=N-O-N=N-Ar) have been known since 1896 but have rarely been used in synthesis. This communication describes the development of a photochemical catalyst-free C-H arylation methodology for the preparation of bi(hetero)aryls by the one-pot reaction of anilines with tert-butyl nitrite and (hetero)arenes under neutral conditions. The key step in this procedure is the in situ formation and subsequent photochemical (>300 nm) homolytic cleavage of a transient diazo anhydride intermediate. The generated aryl radical then efficiently reacts with a (hetero)arene to form the desired bi(hetero)aryls producing only nitrogen, water, and tert-butanol as byproducts. The scope of the reaction for several substituted anilines and (hetero)arenes was investigated. A continuous-flow protocol increasing selectivity and safety has been developed enabling the experimentally straightforward preparation of a variety of substituted bi(hetero)aryls within 45 min of reaction time. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Effects of radiation on hetero-atom-containing polyacetylenes

    International Nuclear Information System (INIS)

    Yamaoka, H.; Matsuyama, T.; Masuda, T.; Higashimura, T.

    1991-01-01

    The effects of radiation on several substituted polyacetylenes containing hetero-atoms such as silicon and chlorine were studied. All the polymers containing silicon atoms degraded in the presence of air, whereas no degradation proceeded in vacuo. In the case of polymers containing chlorine atoms, degradation and crosslinking occurred simultaneously, both in air and in vacuo. The reaction mode of these polymers was found to be strongly dependent on the nature of the substituents. The relationship between the radiation sensitivity and thermal stability of substituted polyacetylenes is discussed on the basis of the obtained results. (author)

  7. Synthesis and thermal properties of hetero-bifunctional PLA oligomers and their stereocomplexes

    NARCIS (Netherlands)

    ten Breteler, M.R.; Feijen, Jan; Dijkstra, Pieter J.; Signori, F.; Signori, F.

    2013-01-01

    Abstract Hetero-telechelic, low-molecular-weight polylactides (PLAs) were prepared by the zinc-catalyzed ring-opening polymerization of l-lactide or d-lactide using functional initiators and subsequent reaction with termination reagents, yielding –OH, –COOH, –NH2 and –SH as functional chain ends.

  8. Further exploration of antimicrobial ketodihydronicotinic acid derivatives by multiple parallel syntheses

    DEFF Research Database (Denmark)

    Laursen, Jane B.; Nielsen, Janne; Haack, T.

    2006-01-01

    A synthetic reexamination of a series of ketodihydronicotinic acid class antibacterial agents was undertaken in an attempt to improve their therapeutic potential. A convenient new synthesis was developed involving hetero Diels-Alder chemistry producing 74 new analogs in a multiple parallel synthe...

  9. Synthesis and properties of sulfonated poly(phenylene sulfone)s without ether linkage by Diels–Alder reaction for PEMFC application

    International Nuclear Information System (INIS)

    Lim, Youngdon; Lee, Hyunchul; Lee, Soonho; Jang, Hohyoun; Hossain, Md. Awlad; Cho, Younggil; Kim, Taeho; Hong, Youngtaik; Kim, Whangi

    2014-01-01

    A new sulfonated poly(phenylene sulfone) polymer (SPPS) was synthesized by Diels-Alder polymerization from 1,4-bis(2,4,5-triphenylcyclopentadienone)benzene (BTPCPB) and 4,4′-diethynylphenylsulfone, and followed by sulfonation reaction with chlorosulfuric acid. A series of sulfonated poly(phenylene sulfone)s (SPPS) with different degrees of sulfonation was prepared in a controllable manner with chlorosulfuric acid. These polymers showed good solubility in aprotic polar solvents, dimethyl acetamide (DMAC) and dimethyl sulfoxide (DMSO). Three different polymer membranes were studied by 1 H NMR spectroscopy, and thermogravimetric analysis (TGA). The ion exchange capacity (IEC) and proton conductivity of SPPS were evaluated according to the degrees of sulfonation. The water uptake (WU) of the synthesized SPPS membranes ranged from 38%∼75%, compared with 32% for Nafion 211 ® at 80 °C. The SPPS membranes exhibited proton conductivities (at 80 °C under 90% RH) of 110.2 mS/cm compared with 102.7 mS/cm for Nafion 211 ® . Power density was performed by single cell and showed similar to Nafion value

  10. One-step hydroprocessing of fatty acids into renewable aromatic hydrocarbons over Ni/HZSM-5: insights into the major reaction pathways.

    Science.gov (United States)

    Xing, Shiyou; Lv, Pengmei; Wang, Jiayan; Fu, Junying; Fan, Pei; Yang, Lingmei; Yang, Gaixiu; Yuan, Zhenhong; Chen, Yong

    2017-01-25

    For high caloricity and stability in bio-aviation fuels, a certain content of aromatic hydrocarbons (AHCs, 8-25 wt%) is crucial. Fatty acids, obtained from waste or inedible oils, are a renewable and economic feedstock for AHC production. Considerable amounts of AHCs, up to 64.61 wt%, were produced through the one-step hydroprocessing of fatty acids over Ni/HZSM-5 catalysts. Hydrogenation, hydrocracking, and aromatization constituted the principal AHC formation processes. At a lower temperature, fatty acids were first hydrosaturated and then hydrodeoxygenated at metal sites to form long-chain hydrocarbons. Alternatively, the unsaturated fatty acids could be directly deoxygenated at acid sites without first being saturated. The long-chain hydrocarbons were cracked into gases such as ethane, propane, and C 6 -C 8 olefins over the catalysts' Brønsted acid sites; these underwent Diels-Alder reactions on the catalysts' Lewis acid sites to form AHCs. C 6 -C 8 olefins were determined as critical intermediates for AHC formation. As the Ni content in the catalyst increased, the Brønsted-acid site density was reduced due to coverage by the metal nanoparticles. Good performance was achieved with a loading of 10 wt% Ni, where the Ni nanoparticles exhibited a polyhedral morphology which exposed more active sites for aromatization.

  11. Ultra-Fast RAFT-HDA Click Conjugation: An Efficient Route to High Molecular Weight Block Copolymers.

    Science.gov (United States)

    Inglis, Andrew J; Stenzel, Martina H; Barner-Kowollik, Christopher

    2009-11-02

    The use of the reversible addition fragmentation chain transfer-hetero Diels-Alder (RAFT-HDA) click reaction for the modular construction of block copolymers is extended to the generation of high molecular weight materials. Cyclopentadienyl end-functionalized polystyrene (PS-Cp) prepared via both atom transfer radical polymerization (ATRP) and the RAFT process are conjugated to poly(isobornyl acrylate) (PiBoA) (also prepared via RAFT polymerization) to achieve well-defined block copolymers with molecular weights ranging from 34 000 to over 100 000 g · mol(-1) and with small polydispersities (PDI HDA click chemistry can provide access to high molecular weight block copolymers in a simple and straight-forward fashion. Copyright © 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Quantum and Statistical Mechanics Applied to Singlet Carbenes, Pericyclic Reactions, and Condensed Phase Phenomena

    Science.gov (United States)

    Evanseck, Jeffrey Donald

    preferential stabilization of the E isomer in both acetonitrile and aqueous solutions. The rates of intramolecular Diels-Alder reactions are compared to recent experimental work and predictions of different solvent systems are made.

  13. [4 + 2] Cycloaddition reaction of C-aryl ketenimines with PTAD as a synthetic equivalent of dinitrogen. Synthesis of triazolocinnolines and cinnolines.

    Science.gov (United States)

    Alajarin, Mateo; Bonillo, Baltasar; Marin-Luna, Marta; Vidal, Angel; Orenes, Raul-Angel

    2009-05-01

    C,C,N-Triaryl ketenimines and C-alkyl-C,N-diaryl ketenimines react with 2 equiv of PTAD to provide 1,2,4-triazolo[1,2-a]cinnolines with a pendant triazolidindione group by means of a Diels-Alder/ene sequence. The treatment of such adducts with potassium hydroxide affords 3-aminocinnolines.

  14. Site-specific chemical conjugation of human Fas ligand extracellular domain using trans-cyclooctene - methyltetrazine reactions.

    Science.gov (United States)

    Muraki, Michiro; Hirota, Kiyonori

    2017-07-03

    Fas ligand plays a key role in the human immune system as a major cell death inducing protein. The extracellular domain of human Fas ligand (hFasLECD) triggers apoptosis of malignant cells, and therefore is expected to have substantial potentials in medical biotechnology. However, the current application of this protein to clinical medicine is hampered by a shortage of the benefits relative to the drawbacks including the side-effects in systemic administration. Effective procedures for the engineering of the protein by attaching useful additional functions are required to overcome the problem. A procedure for the site-specific chemical conjugation of hFasLECD with a fluorochrome and functional proteins was devised using an inverse-electron-demand Diels-Alder reaction between trans-cyclooctene group and methyltetrazine group. The conjugations in the present study were attained by using much less molar excess amounts of the compounds to be attached as compared with the conventional chemical modification reactions using maleimide derivatives in the previous study. The isolated conjugates of hFasLECD with sulfo-Cy3, avidin and rabbit IgG Fab' domain presented the functional and the structural integrities of the attached molecules without impairing the specific binding activity toward human Fas receptor extracellular domain. The present study provided a new fundamental strategy for the production of the engineered hFasLECDs with additional beneficial functions, which will lead to the developments of the improved diagnostic systems and the effective treatment methods of serious diseases by using this protein as a component of novel molecular tools.

  15. Synthesis of hetero ionic compounds using dialkylcarbonate quaternization

    Energy Technology Data Exchange (ETDEWEB)

    Friesen, Cody A.; Wolfe, Derek; Johnson, Paul Bryan

    2018-04-03

    Methods of preparing hetero ionic complexes, and ionic liquids from bisulfate salts of heteroatomic compounds using dialkylcarbonates as a primary quaternizing reactant are disclosed. Also disclosed are methods of making electrochemical cells comprising the ionic liquids, and an electrochemical cell comprising an alkaline electrolyte and a hetero ionic complex additive.

  16. HETERO code, heterogeneous procedure for reactor calculation

    International Nuclear Information System (INIS)

    Jovanovic, S.M.; Raisic, N.M.

    1966-11-01

    This report describes the procedure for calculating the parameters of heterogeneous reactor system taking into account the interaction between fuel elements related to established geometry. First part contains the analysis of single fuel element in a diffusion medium, and criticality condition of the reactor system described by superposition of elements interactions. the possibility of performing such analysis by determination of heterogeneous system lattice is described in the second part. Computer code HETERO with the code KETAP (calculation of criticality factor η n and flux distribution) is part of this report together with the example of RB reactor square lattice

  17. Stochastic models (cooperative and non-cooperative) for NMR analysis of the hetero-association of aromatic molecules in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Evstigneev, Maxim P. [Department of Physics, Sevastopol National Technical University, Sevastopol 99053, Crimea (Ukraine)], E-mail: max_evstigneev@mail.ru; Davies, David B. [School of Biological and Chemical Sciences, Birkbeck College, University of London, Malet Street, London WC1E 7HX (United Kingdom); Veselkov, Alexei N. [Department of Physics, Sevastopol National Technical University, Sevastopol 99053, Crimea (Ukraine)

    2006-01-25

    Stochastic cooperative (STOCH-C) and non-cooperative (STOCH-NC) models have been developed for NMR analysis of the hetero-association of aromatic compounds in solution, in order to take into account all physically meaningful association reactions of molecules in which there are no limitations on the lengths of the aggregates and complexes. These algorithmical approaches are compared with previously published basic (BASE) and generalized (GEN) analytical statistical thermodynamical models of hetero-association of biologically active aromatic molecules using the same sets of published NMR data measured under the same solution conditions (0.1 M phosphate buffer, pD = 7.1, T = 298 K). It is shown that, within experimental errors, the BASE analytical model may be used to describe molecular systems characterized by relatively small contributions of hetero-association reactions, whereas the GEN model may be applied to hetero-association reactions of any aromatic compound with different self-association properties. The STOCH-C computational algorithm enabled the effect on hetero-association of the interactions of molecules with different cooperativity parameters of self-association to be estimated for the first time and it is proposed that the algorithm for the stochastic models has great potential for detailed investigation and understanding of the interactions of aromatic molecules in solution.

  18. Stochastic models (cooperative and non-cooperative) for NMR analysis of the hetero-association of aromatic molecules in aqueous solution

    International Nuclear Information System (INIS)

    Evstigneev, Maxim P.; Davies, David B.; Veselkov, Alexei N.

    2006-01-01

    Stochastic cooperative (STOCH-C) and non-cooperative (STOCH-NC) models have been developed for NMR analysis of the hetero-association of aromatic compounds in solution, in order to take into account all physically meaningful association reactions of molecules in which there are no limitations on the lengths of the aggregates and complexes. These algorithmical approaches are compared with previously published basic (BASE) and generalized (GEN) analytical statistical thermodynamical models of hetero-association of biologically active aromatic molecules using the same sets of published NMR data measured under the same solution conditions (0.1 M phosphate buffer, pD = 7.1, T = 298 K). It is shown that, within experimental errors, the BASE analytical model may be used to describe molecular systems characterized by relatively small contributions of hetero-association reactions, whereas the GEN model may be applied to hetero-association reactions of any aromatic compound with different self-association properties. The STOCH-C computational algorithm enabled the effect on hetero-association of the interactions of molecules with different cooperativity parameters of self-association to be estimated for the first time and it is proposed that the algorithm for the stochastic models has great potential for detailed investigation and understanding of the interactions of aromatic molecules in solution

  19. Exploiting the Electrophilic and Nucleophilic Dual Role of Nitrile Imines: One-Pot, Three-Component Synthesis of Furo[2,3-d]pyridazin-4(5H)-ones.

    Science.gov (United States)

    Giustiniano, Mariateresa; Mercalli, Valentina; Amato, Jussara; Novellino, Ettore; Tron, Gian Cesare

    2015-08-21

    An expeditious multicomponent reaction to synthesize tetrasubstituted furo[2,3-d]pyridazin-4(5H)-ones is reported. In brief, hydrazonoyl chlorides react with isocyanoacetamides, in the presence of TEA, to give 1,3-oxazol-2-hydrazones which, without being isolated, can react with dimethylacetylene dicarboxylate to afford furo[2,3-d]pyridazin-4(5H)-ones with an unprecedented level of complexity in a triple domino Diels-Alder/retro-Diels-Alder/lactamization reaction sequence.

  20. Chemistry and biosynthesis of isoprenylated flavonoids from Japanese mulberry tree

    Science.gov (United States)

    Nomura, Taro; Hano, Yoshio; Fukai, Toshio

    2009-01-01

    Many isoprenylated flavonoids have been isolated from Japanese mulberry tree (Moraceae). Among them, kuwanons G (1) and H (2) were the first isolated active substances exhibiting a hypotensive effect. These compounds are considered to be formed through an enzymatic Diels-Alder type reaction between an isoprenyl portion of an isoprenylphenol as the diene and an α, β-double bond of chalcone as the dienophile. The absolute configurations of these Diels-Alder type adducts were confirmed by three different methods. The stereochemistries of the adducts were consistent with those of ones in the Diels-Alder reaction involving exo- and endo-addition. Some strains of Morus alba callus tissues have a high productivity of mulberry Diels-Alder type adducts, such as chalcomoracin (3) and kuwanon J (4). The biosynthetic studies of the mulberry Diels-Alder type adducts have been carried out with the aid of the cell strain. Chalcomoracin (3) and kuwanon J (4) were proved to be enzymatic Diels-Alder type reaction products by the administration experiments with O-methylchalcone derivatives. Furthermore, for the isoprenoid biosynthesis of prenylflavonoids in Morus alba callus tissues by administration of [1,3-13C2]- and [2-13C]-glycerol, a novel way through the junction of glycolysis and pentose-phosphate cycle was proved. Two independent isoprenoid biosynthetic pathways, that for sterols and that for isoprenoidphenols, operate in the Morus alba cell cultures. The former is susceptible to compactin (ML-236) and the latter resists to compactin in the cell cultures, respectively. PMID:19907125

  1. Synthesis of naphthalenes through three-component coupling of alkynes, Fischer carbene complexes, and benzaldehyde hydrazones via isoindole intermediates.

    Science.gov (United States)

    Duan, Shaofeng; Sinha-Mahapatra, Dilip K; Herndon, James W

    2008-04-17

    The synthesis of naphthalene derivatives through three-component coupling of 2-alkynylbenzaldehyde hydrazones with carbene complexes and electron-deficient alkynes has been examined. The reaction involves formation of an isoindole derivative, followed by intramolecular Diels-Alder reaction, followed by nitrene extrusion. The reaction was highly regioselective using unsymmetrical alkynes.

  2. Enantioselective cycloadditions with alpha,beta-disubstituted acrylimides.

    Science.gov (United States)

    Sibi, Mukund P; Ma, Zhihua; Itoh, Kennosuke; Prabagaran, Narayanasamy; Jasperse, Craig P

    2005-06-09

    [reaction: see text] The use of N-H imide templates provides a solution to the problem of rotamer control in Lewis acid catalyzed reactions of alpha,beta-disubstituted acryloyl imides. Reactions proceed through the s-cis rotamer and with improved reactivity because A(1,3) strain is avoided. Enantioselective nitrone, nitrile oxide, and Diels-Alder cycloadditions demonstrate the principle.

  3. Advances in quantum and molecular mechanical (QM/MM) simulations for organic and enzymatic reactions.

    Science.gov (United States)

    Acevedo, Orlando; Jorgensen, William L

    2010-01-19

    Application of combined quantum and molecular mechanical (QM/MM) methods focuses on predicting activation barriers and the structures of stationary points for organic and enzymatic reactions. Characterization of the factors that stabilize transition structures in solution and in enzyme active sites provides a basis for design and optimization of catalysts. Continued technological advances allowed for expansion from prototypical cases to mechanistic studies featuring detailed enzyme and condensed-phase environments with full integration of the QM calculations and configurational sampling. This required improved algorithms featuring fast QM methods, advances in computing changes in free energies including free-energy perturbation (FEP) calculations, and enhanced configurational sampling. In particular, the present Account highlights development of the PDDG/PM3 semi-empirical QM method, computation of multi-dimensional potentials of mean force (PMF), incorporation of on-the-fly QM in Monte Carlo (MC) simulations, and a polynomial quadrature method for efficient modeling of proton-transfer reactions. The utility of this QM/MM/MC/FEP methodology is illustrated for a variety of organic reactions including substitution, decarboxylation, elimination, and pericyclic reactions. A comparison to experimental kinetic results on medium effects has verified the accuracy of the QM/MM approach in the full range of solvents from hydrocarbons to water to ionic liquids. Corresponding results from ab initio and density functional theory (DFT) methods with continuum-based treatments of solvation reveal deficiencies, particularly for protic solvents. Also summarized in this Account are three specific QM/MM applications to biomolecular systems: (1) a recent study that clarified the mechanism for the reaction of 2-pyrone derivatives catalyzed by macrophomate synthase as a tandem Michael-aldol sequence rather than a Diels-Alder reaction, (2) elucidation of the mechanism of action of fatty

  4. Trans-4 Hexadiene- 1-Alcohol Maleic Andydride D-A Reaction%反式4-己二烯-1-醇与马来酸酐的D-A反应

    Institute of Scientific and Technical Information of China (English)

    谢永生; 郝斌华; 冯磊

    2012-01-01

    To overcome the shortcomings of the traditional D-A reaction experimenting, this article argues that the best way to carry out the college organic chemistry experimenting course is the counter-reaction of Trans-4 Hexadiene-l-Alcohol maleic andydride diel-alder, and proposes some measures and environment-friendly and size-reducing improvement: in a tube a simple mixing of 4- Hexadiene-l-ol, maleic andydride and a small amount of ethyl acetate can witness the completion of more than ten experiments by students in a water bath oscillator. After the experimenting, only a small amount of solvent recovery is left and the product categorical structure can be easily assessed with 1NMR experiments.%文章针对传统D-A反应教学实验的缺点,提出反式4-己二烯-1-醇与马来酸酐的Diels-Alder反应是适合大学有机化学教学实验的最佳选择,并对该实验进行绿色化和微型化改进:仅需在试管中简单的混合4-己二烯-1-醇、马来酸酐和少量乙酸乙酯即可在一台水浴振荡器上完成数十个学生实验;实验后处理简洁快速,仅有少量回收溶剂产生;产品绝对结构很容易地由氢核磁共振实验鉴定.

  5. Reactivity and Synthetic Applications of 4,5-Dicyanopyridazine: An Overview

    Directory of Open Access Journals (Sweden)

    Donatella Giomi

    2010-03-01

    Full Text Available Despite the poor reputation of electron-deficient pyridazines in intermolecular Hetero Diels-Alder (HDA reactions, 4,5-dicyanopyridazine (DCP showed a surprising reactivity as a heterocyclic azadiene in inverse electron-demand HDA processes with different dienophiles. The use of alkenes, alkynes and enamines as 2p electron counterparts afforded dicyanocyclohexa-1,3-dienes and substituted phthalonitriles, respectively, while the use of suitable bis-dienophiles provides a general strategy for the one-pot synthesis of polycyclic carbo- and hetero-cage systemsthrough pericyclic three-step homodomino processes. HDA reactions with heterocyclic dienophiles allowed direct benzoannelation: in particular, pyrrole and indole derivatives were converted to dicyano-indoles and -carbazoles. In addition an unprecedented reactivity of DCP as a very reactive heterocyclic electrophile at the C-4 carbon was also evidenced: by changing the experimental conditions, cyanopyrrolyl- and cyanoindolyl-pyridazines were obtained through reactions of pyrrole and indole systems as carbon nucleophiles in formal SNAr2 processes where a CN group of DCP acts as leaving group. Thus, careful control of the reaction conditions allows exploitation of both pathways for the synthesis of different classes of heterocyclic derivatives.

  6. HETERO code, heterogeneous procedure for reactor calculation; Program Hetero, heterogeni postupak proracuna reaktora

    Energy Technology Data Exchange (ETDEWEB)

    Jovanovic, S M; Raisic, N M [Boris Kidric Institute of Nuclear Sciences Vinca, Beograd (Yugoslavia)

    1966-11-15

    This report describes the procedure for calculating the parameters of heterogeneous reactor system taking into account the interaction between fuel elements related to established geometry. First part contains the analysis of single fuel element in a diffusion medium, and criticality condition of the reactor system described by superposition of elements interactions. the possibility of performing such analysis by determination of heterogeneous system lattice is described in the second part. Computer code HETERO with the code KETAP (calculation of criticality factor {eta}{sub n} and flux distribution) is part of this report together with the example of RB reactor square lattice.

  7. Bioorthogonal Chemistry-Introduction and Overview

    Czech Academy of Sciences Publication Activity Database

    Carell, T.; Vrábel, Milan

    2016-01-01

    Roč. 374, č. 1 (2016), č. článku 9. ISSN 2365-0869 Institutional support: RVO:61388963 Keywords : bioorthogonal reactions * click chemistry * biomolecule labeling * 1,3-dipolar cycloaddition * Diels-Alder reaction Subject RIV: CC - Organic Chemistry Impact factor: 4.033, year: 2016

  8. phenylalanine and l-tyrosine as chiral micellar media for the cat

    African Journals Online (AJOL)

    polar solvents [15-18]. Hence, surfactants offer the possibility for organic reactions to occur in aqueous media, and from the viewpoint of green chemistry, water is safer, harmless and environmentally benign [19]. However, there has been limited work on the use of chiral micellar media to catalyze Diels-. Alder reactions.

  9. Photosensitized oxygenation of alkenes in the presence of bisazafullerene (C59N)2 and hydroazafullerene C59HN

    International Nuclear Information System (INIS)

    Tagmatarchis, Nikos; Shinohara, Hisanori

    2001-01-01

    Bisazafullerene (C 59 N) 2 and hydroazafullerene C 59 HN photosensitize the reaction of alkenes with oxygen. 2-methyl 2-butene and α-terpinene undergo ene and Diels-Alder photooxygenation reactions, respectively, in the presence of minute amounts of azafullerenes to produce the corresponding peroxides

  10. Chiral 1,3,2-oxazaborolidines in asymmetric synthesis: recent advances

    International Nuclear Information System (INIS)

    Glushkov, Vladimir A; Tolstikov, Alexander G

    2004-01-01

    The use of chiral 1,3,2-oxazaborolidines in asymmetric organic synthesis, particularly, in enantioselective reduction of ketones, imines and oxime ethers, asymmetric Diels-Alder reactions, aldol condensation and atroposelective reduction of lactones is reviewed. Reactions of immobilised 1,3,2-oxazaborolidines are also considered.

  11. Structural diversity through intramolecular cycloaddition and modulation of chemical reactivity in excited state. Synthesis and photoreactions of 3-oxa-tricyclo[5.2.2.0(1,5)]undecenones: novel stereoselective route to oxa-triquinanes and oxa-sterpuranes.

    Science.gov (United States)

    Singh, V; Alam, S Q

    2000-11-20

    Synthesis of 11-methyl-3-oxa-tricyclo[5.2.2.0(1,5)]undecenones by intramolecular Diels-Alder reaction of highly labile spiroepoxycyclohexa-2,4-dienones and its photochemical reactions upon triplet (3T) and singlet (1S) excitation leading to a stereoselective route to oxa-triquinane and oxa-sterpurane, respectively, is described.

  12. Thermal and catalytic intramolecular [4+2]-cycloaddition in 2-alkenylfurans

    International Nuclear Information System (INIS)

    Zubkov, Fedor I; Nikitina, Evgenia V; Varlamov, Alexey V

    2005-01-01

    The published data on the intramolecular Diels-Alder reaction in compounds of the 2-alkenylfuran series are generalised. The methods and conditions for the preparation of tricyclic systems are considered. The effects of the substituents in the furan and the unsaturated fragments on the cycloaddition are discussed. The application of this reaction to the synthesis of alkaloids and terpenoids is exemplified.

  13. Thermal and catalytic intramolecular [4+2]-cycloaddition in 2-alkenylfurans

    Energy Technology Data Exchange (ETDEWEB)

    Zubkov, Fedor I; Nikitina, Evgenia V; Varlamov, Alexey V [Department of Physical, Mathematical and Natural Sciences, Peoples' Friendship University of Russia (Russian Federation)

    2005-07-31

    The published data on the intramolecular Diels-Alder reaction in compounds of the 2-alkenylfuran series are generalised. The methods and conditions for the preparation of tricyclic systems are considered. The effects of the substituents in the furan and the unsaturated fragments on the cycloaddition are discussed. The application of this reaction to the synthesis of alkaloids and terpenoids is exemplified.

  14. Experimental and numerical investigation of hetero-/homogeneous combustion-based HCCI of methane–air mixtures in free-piston micro-engines

    International Nuclear Information System (INIS)

    Chen, Junjie; Liu, Baofang; Gao, Xuhui; Xu, Deguang

    2016-01-01

    Highlights: • Single-shot experiments and a transient model of micro-engine were presented. • Coupled combustion can significantly improve in-cylinder temperatures. • Coupled combustion can reduce mass losses and compression ratios. • Heterogeneous reactions cause earlier ignition. • Heat losses result in higher mass losses. - Abstract: The hetero-/homogenous combustion-based HCCI (homogeneous charge compression ignition) of fuel–lean methane–air mixtures over alumina-supported platinum catalysts was investigated experimentally and numerically in free-piston micro-engines without ignition sources. Single-shot experiments were carried out in the purely homogeneous and coupled hetero-/homogeneous combustion modes, involved temperature measurements, capturing the visible combustion image sequences, exhaust gas analysis, and the physicochemical characterization of catalysts. Simulations were performed with a two-dimensional transient model that includes detailed hetero-/homogeneous chemistry and transport, leakage, and free-piston motion to gain physical insight and to explore the hetero-/homogeneous combustion characteristics. The micro-engine performance concerning combustion efficiency, mass loss, energy density, and free-piston dynamics was investigated. The results reveal that both purely homogeneous and coupled hetero-/homogeneous combustion of methane–air mixtures in a narrow cylinder with a diameter of 3 mm and a height of approximately 0.3 mm are possible. The coupled hetero-/homogeneous mode can not only significantly improve the combustion efficiency, in-cylinder temperature and pressure, output power and energy density, but also reduce the mass loss because of its lower compression ratio and less time spent around TDC (top dead center) and during the expansion stroke, indicating that this coupled mode is a promising combustion scheme for micro-engine. Heat losses result in higher mass losses. Heterogeneous reactions cause earlier ignition

  15. Unidirectional oxide hetero-interface thin-film diode

    International Nuclear Information System (INIS)

    Park, Youngmin; Lee, Eungkyu; Lee, Jinwon; Lim, Keon-Hee; Kim, Youn Sang

    2015-01-01

    The unidirectional thin-film diode based on oxide hetero-interface, which is well compatible with conventional thin-film fabrication process, is presented. With the metal anode/electron-transporting oxide (ETO)/electron-injecting oxide (EIO)/metal cathode structure, it exhibits that electrical currents ohmically flow at the ETO/EIO hetero-interfaces for only positive voltages showing current density (J)-rectifying ratio of ∼10 5 at 5 V. The electrical properties (ex, current levels, and working device yields) of the thin-film diode (TFD) are systematically controlled by changing oxide layer thickness. Moreover, we show that the oxide hetero-interface TFD clearly rectifies an AC input within frequency (f) range of 10 2  Hz < f < 10 6  Hz, providing a high feasibility for practical applications

  16. Unidirectional oxide hetero-interface thin-film diode

    Energy Technology Data Exchange (ETDEWEB)

    Park, Youngmin; Lee, Eungkyu; Lee, Jinwon; Lim, Keon-Hee [Program in Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 151-742 (Korea, Republic of); Kim, Youn Sang, E-mail: younskim@snu.ac.kr [Program in Nano Science and Technology, Graduate School of Convergence Science and Technology, Seoul National University, Seoul 151-742 (Korea, Republic of); Advanced Institute of Convergence Technology, Gyeonggi-do 443-270 (Korea, Republic of)

    2015-10-05

    The unidirectional thin-film diode based on oxide hetero-interface, which is well compatible with conventional thin-film fabrication process, is presented. With the metal anode/electron-transporting oxide (ETO)/electron-injecting oxide (EIO)/metal cathode structure, it exhibits that electrical currents ohmically flow at the ETO/EIO hetero-interfaces for only positive voltages showing current density (J)-rectifying ratio of ∼10{sup 5} at 5 V. The electrical properties (ex, current levels, and working device yields) of the thin-film diode (TFD) are systematically controlled by changing oxide layer thickness. Moreover, we show that the oxide hetero-interface TFD clearly rectifies an AC input within frequency (f) range of 10{sup 2} Hz < f < 10{sup 6} Hz, providing a high feasibility for practical applications.

  17. InAs/Si Hetero-Junction Nanotube Tunnel Transistors

    KAUST Repository

    Hanna, Amir; Fahad, Hossain M.; Hussain, Muhammad Mustafa

    2015-01-01

    Hetero-structure tunnel junctions in non-planar gate-all-around nanowire (GAA NW) tunnel FETs (TFETs) have shown significant enhancement in ‘ON’ state tunnel current over their all-silicon counterpart. Here we show the unique concept of nanotube TFET in a hetero-structure configuration that is capable of much higher drive current as opposed to that of GAA NW TFETs.Through the use of inner/outer core-shell gates, a single III-V hetero-structured nanotube TFET leverages physically larger tunneling area while achieving higher driver current (ION) and saving real estates by eliminating arraying requirement. Numerical simulations has shown that a 10 nm thin nanotube TFET with a 100 nm core gate has a 5×normalized output current compared to a 10 nm diameter GAA NW TFET.

  18. InAs/Si Hetero-Junction Nanotube Tunnel Transistors

    KAUST Repository

    Hanna, Amir

    2015-04-29

    Hetero-structure tunnel junctions in non-planar gate-all-around nanowire (GAA NW) tunnel FETs (TFETs) have shown significant enhancement in ‘ON’ state tunnel current over their all-silicon counterpart. Here we show the unique concept of nanotube TFET in a hetero-structure configuration that is capable of much higher drive current as opposed to that of GAA NW TFETs.Through the use of inner/outer core-shell gates, a single III-V hetero-structured nanotube TFET leverages physically larger tunneling area while achieving higher driver current (ION) and saving real estates by eliminating arraying requirement. Numerical simulations has shown that a 10 nm thin nanotube TFET with a 100 nm core gate has a 5×normalized output current compared to a 10 nm diameter GAA NW TFET.

  19. Radioimmunoassay with heterologous antibody (hetero-antibody RIA)

    International Nuclear Information System (INIS)

    Iwasawa, Atsushi; Hayashi, Hiroaki; Itoh, Zen; Wakabayashi, Katsumi

    1991-01-01

    To develop a homologous radioimmunoassay (RIA) for a hormone of a small or rare animal often meets difficulty in collecting a large amount of purified antigen required for antibody production. On the other hand, to employ a heterologous RIA to estimate the hormone often gives poor sensitivity. To overcome this difficulty, a 'hetero-antibody' RIA was studied. In a hetero-antibody RIA system, a purified preparation of a hormone is used for radioiodination and standardization and a heterologous antibody to the hormone is used for the first antibody. Canine motilin and rat LH were selected as examples, and anti-porcine motilin and anti-hCG, anti-hCGβ or anti-ovine LHβ was used as the heterologous antibody. The sensitivities of the hetero-antibody RIAs were much higher than those of heterologous RIAs in any case, showing that these hetero-antibody RIA systems were suitable for practical use. To clarify the principle of hetero-antibody RIA, antiserum to porcine motilin was fractionated on an affinity column where canine motilin was immobilized. The fraction bound had greater constants of affinity with both porcine and canine motilins than the rest of the antibody fractions. This fraction also reacted with a synthetic peptide corresponding to the C-terminal sequence common to porcine and canine motilins in a competitive binding test with labeled canine motilin. These results suggest that an antibody population having high affinity and cross-reactivity is present in polyclonal antiserum and indicate that the population can be used in hetero-antibody RIA at an appropriate concentration. (author)

  20. One-Dimensional Hetero-Nanostructures for Rechargeable Batteries.

    Science.gov (United States)

    Mai, Liqiang; Sheng, Jinzhi; Xu, Lin; Tan, Shuangshuang; Meng, Jiashen

    2018-04-17

    Rechargeable batteries are regarded as one of the most practical electrochemical energy storage devices that are able to convert and store the electrical energy generated from renewable resources, and they function as the key power sources for electric vehicles and portable electronics. The ultimate goals for electrochemical energy storage devices are high power and energy density, long lifetime, and high safety. To achieve the above goals, researchers have tried to apply various morphologies of nanomaterials as the electrodes to enhance the electrochemical performance. Among them, one-dimensional (1D) materials show unique superiorities, such as cross-linked structures for external stress buffering and large draw ratios for internal stress dispersion. However, a homogeneous single-component electrode material can hardly have the characteristics of high electronic/ionic conductivity and high stability in the electrochemical environment simultaneously. Therefore, designing well-defined functional 1D hetero-nanostructures that combine the advantages and overcome the limitations of different electrochemically active materials is of great significance. This Account summarizes fabrication strategies for 1D hetero-nanostructures, including nucleation and growth, deposition, and melt-casting and electrospinning. Besides, the chemical principles for each strategy are discussed. The nucleation and growth strategy is suitable for growing and constructing 1D hetero-nanostructures of partial transition metal compounds, and the experimental conditions for this strategy are relatively accessible. Deposition is a reliable strategy to synthesize 1D hetero-nanostructures by decorating functional layers on 1D substrate materials, on the condition that the preobtained substrate materials must be stable in the following deposition process. The melt-casting strategy, in which 1D hetero-nanostructures are synthesizes via a melting and molding process, is also widely used. Additionally

  1. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    ... between carbon-carbon bond length and the ease of retro Diels-Alder reaction ... Syntheses, characterization and crystal structures of potassium and barium ... Structural diversity in serine derived homochiral metal organic frameworks ..... supramolecular assemblies of dimetal subunits differing in coordinated water ...

  2. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences. Sambasivarao Kotha. Articles written in Journal of Chemical Sciences. Volume 126 Issue 5 September 2014 pp 1369-1371 Special issue on Chemical Crystallography. Correlation between carbon-carbon bond length and the ease of retro Diels-Alder reaction · Sambasivarao ...

  3. Conformationally locked nucleoside analogues based on the bridgehead substituted 7-oxonorbornane and their antiviral properties

    Czech Academy of Sciences Publication Activity Database

    Dejmek, Milan; Hřebabecký, Hubert; Dračínský, Martin; Neyts, J.; Leyssen, P.; Mertlíková-Kaiserová, Helena; Nencka, Radim

    2011-01-01

    Roč. 76, č. 12 (2011), s. 1549-1566 ISSN 0010-0765 R&D Projects: GA MŠk 1M0508 Institutional research plan: CEZ:AV0Z40550506 Keywords : 1'-homonucleosides * Diels - Alder reaction * antiviral agents Subject RIV: CC - Organic Chemistry Impact factor: 1.283, year: 2011

  4. Author Details

    African Journals Online (AJOL)

    Joondan, N. Vol 31, No 3 (2017) - Articles The use of optically active O-alkyl ester hydrochlorides of L-phenylalanine and L-tyrosine as chiral micellar media for the catalysis of diels-alder reactions. Abstract PDF. ISSN: 1726-801X. AJOL African Journals Online. HOW TO USE AJOL... for Researchers · for Librarians ...

  5. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 5. Correlation between carbon-carbon bond length and the ease of retro Diels-Alder reaction. Sambasivarao Kotha Shaibal Banerjee Mobin Shaikh. Special issue on Chemical Crystallography Volume 126 Issue 5 September 2014 pp 1369-1371 ...

  6. In the search of an electron transfer between π-donors and C60: the bis-linking of tetrathiafulvalene (TTF) to C60

    International Nuclear Information System (INIS)

    Hudhomme, P.; Rabreau, J.M.; Cariou, M.; Jubault, M.; Gorgues, A.

    1998-01-01

    In order to realize the bis-linking of tetrathiafulvalene (TTF) to one or two C 60 , and to reach the dyad compounds 1 and 2, the [4+2] Diels-Alder reactions of C 60 with orthoquinodimethanic derivatives of 1,3-dithioles 5a,b or TTF 9 are studied. (orig.)

  7. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Keywords. Maoecrystal V; synthesis; Diels-Alder reaction; dearomatization. Abstract. Nature continues to be a rich source of bio-active compounds that often provide the lead for drug development. Isolation and characterization of maoecrystal V, a C19 terpenoid, having potent and selective cytotoxicity towards HeLa cells ...

  8. Synthesis of Highly Symmetrical Triptycene Tetra- and Hexacarboxylates

    Czech Academy of Sciences Publication Activity Database

    Rybáčková, Markéta; Bělohradský, Martin; Holý, Petr; Pohl, Radek; Dekoj, Václav; Závada, Jiří

    -, č. 10 (2007), s. 1554-1558 ISSN 0039-7881 R&D Projects: GA ČR GA203/03/0087 Institutional research plan: CEZ:AV0Z40550506 Keywords : carboxylic acids * Diels - Alder reaction s * oxidations * triptycenes * arynes Subject RIV: CC - Organic Chemistry Impact factor: 2.257, year: 2007

  9. Synthesis of extended bifunctional triptycenes

    Czech Academy of Sciences Publication Activity Database

    Rybáček, Jiří; Závada, Jiří; Holý, Petr

    -, č. 22 (2008), s. 3615-3618 ISSN 0039-7881 R&D Projects: GA ČR GA203/03/0087 Institutional research plan: CEZ:AV0Z40550506 Keywords : anthracenes * arynes * Diels - Alder reaction * quinones * triptycenes Subject RIV: CC - Organic Chemistry Impact factor: 2.470, year: 2008

  10. Fluxional additives: a second generation control in enantioselective catalysis.

    Science.gov (United States)

    Sibi, Mukund P; Manyem, Shankar; Palencia, Hector

    2006-10-25

    The concept of "fluxional additives", additives that can adopt enantiomeric conformations depending on the chiral information in the ligand, is demonstrated in enantioselective Diels-Alder and nitrone cycloaddition reactions. The additive design is modular, and diverse structures are accessible in three steps. Chiral Lewis acids from main group and transition metals show enhancements in enantioselectivity in the presence of these additives.

  11. A self-crosslinking thermosetting monomer with both epoxy and anhydride groups derived from Tung oil fatty acids: Synthesis and properties

    Science.gov (United States)

    A self-crosslinking compound with epoxy groups and anhydride groups (GEMA) has been successfully synthesized from Tung oil fatty acid by reacting with maleic anhydride via the Diels-Alder reaction. GEMA has very good storage stability and can be cured with trace amounts of tertiary amine. This advan...

  12. PHENYLSULFONYL-SUBSTITUTED 5-ALKOXY-2(5H)-FURANONES - A NEW CLASS OF HIGHLY REACTIVE CHIRAL DIENOPHILES

    NARCIS (Netherlands)

    DEJONG, JC; VANDENBERG, KJ; FERINGA, BL; van Leusen, A.M.

    1991-01-01

    The synthesis of enantiomerically pure (5S)-5-(d-menthyloxy)-4-(phenylsulfonyl)-2(5H)-furanone (4) and the application of 4 as efficient dienophile in Diels-Alder reactions under mild conditions with enantioselectivities > 98% e.e. are described.

  13. Toward a catalytic site in DNA

    DEFF Research Database (Denmark)

    Jakobsen, Ulla; Rohr, Katja; Vogel, Stefan

    2007-01-01

    A number of functionalized polyaza crown ether building blocks have been incorporated into DNA-conjugates as catalytic Cu(2+) binding sites. The effect of the DNA-conjugate catalyst on the stereochemical outcome of a Cu(2+)-catalyzed Diels-Alder reaction will be presented....

  14. DNA-based asymmetric catalysis : Sequence-dependent rate acceleration and enantioselectivity

    NARCIS (Netherlands)

    Boersma, Arnold J.; Klijn, Jaap E.; Feringa, Ben L.; Roelfes, Gerard

    2008-01-01

    This study shows that the role of DNA in the DNA-based enantioselective Diels-Alder reaction of azachalcone with cyclopentadiene is not limited to that of a chiral scaffold. DNA in combination with the copper complex of 4,4'-dimethyl-2,2'-bipyridine (Cu-L1) gives rise to a rate acceleration of up to

  15. 3,6-bis-(2-pyridyl)-pyridazine as supramolecular (CO)initiator for DL-lactide polymerization

    NARCIS (Netherlands)

    Hoogenboom, R.; Schubert, U.S.

    2003-01-01

    The synthesis of a new hydroxy functionalized dipyridylpyridazine by a Diels-Alder reaction between 5-hexyn-1-ol and dipyridyltetrazine was reported. An aluminum alkoxide was generated in situ from this functional ligand to initiate the controlled ring opening polymn. of of DL-lactide resulting in a

  16. Synthesis and characterization of novel substituted 3,6-bis(2-pyridyl)pyridazine metal-coordinating ligands

    NARCIS (Netherlands)

    Hoogenboom, R.; Kickelbick, G.; Schubert, U.S.

    2003-01-01

    The synthesis of novel functionalized 3,6-di(2-pyridyl)pyridazines via an inverse electron demand Diels-Alder reaction between the corresponding 3,6-di(2-pyridyl)-1,2,4,5-tetrazine and various alkynes is reported. The resulting 3,6-di(2-pyridyl)pyridazines were investigated using X-ray

  17. Remendable Polymeric Materials Using Reversible Covalent Bonds

    Science.gov (United States)

    2008-12-01

    response in poly(ethylene-co-methacrylic acid ) copolymers. Journal of The Royal Society Interface, 4, 405-411. Kavitha, A. A., and N. K. Singha...2007: A tailor-made polymethacrylate bearing a reactive diene in reversible diels-alder reaction. J. Polym. Sci. A Polym. Chem., 45, 4441-4449

  18. Synthesis and reactivity of aliphatic sulfur pentafluorides from substituted (pentafluorosulfanyl)benzenes

    Czech Academy of Sciences Publication Activity Database

    Vida, Norbert; Václavík, Jiří; Beier, Petr

    2016-01-01

    Roč. 12, Jan 20 (2016), s. 110-116 ISSN 1860-5397 Institutional support: RVO:61388963 Keywords : dearomatization * decarboxylation * Diels-Alder reaction * oxidation * pentafluorosulfanyl group Subject RIV: CC - Organic Chemistry Impact factor: 2.337, year: 2016 http://www.beilstein-journals.org/bjoc/single/articleFullText.htm?publicId=1860-5397-12-12

  19. Synthesis of Highly Functionalised Enantiopure Bicyclo[3.2.1]- octane Systems from Carvone

    Directory of Open Access Journals (Sweden)

    Noelia Vera

    2004-04-01

    Full Text Available The commercially available monoterpene carvone has been efficiently convertedinto the tricyclo[3.2.1.02.7]octane and bicyclo[3.2.1]octane systems characteristic of somebiologically active compounds. The sequence used for this transformation involves as keyfeatures an intramolecular Diels-Alder reaction of a 5-vinyl-1,3-cyclohexadiene and acyclopropane ring opening.

  20. Genetically designed biomolecular capping system for mesoporous silica nanoparticles enables receptor-mediated cell uptake and controlled drug release

    Czech Academy of Sciences Publication Activity Database

    Datz, S.; Argyo, C.; Gattner, M.; Weiss, V.; Brunner, K.; Bretzler, J.; von Schirnding, C.; Torrano, A. A.; Spada, F.; Vrábel, Milan; Engelke, H.; Bräuchle, C.; Carell, T.; Bein, T.

    2016-01-01

    Roč. 8, č. 15 (2016), s. 8101-8110 ISSN 2040-3364 Institutional support: RVO:61388963 Keywords : responsive controlled release * Diels-Alder reactions * human carbonic anhydrase Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 7.367, year: 2016 http://pubs.rsc.org/en/content/articlehtml/2016/nr/c5nr08163g

  1. Normal and hetero-yellow endosperm grain sorghum as substitute ...

    African Journals Online (AJOL)

    housed in flat deck-type cages, 1,6 x 1 m, fitted with a self- feeder and an automatic water nipple. Temperatures in the ... adiabatic bomb calorimeter. Amino acid analyses, following acid hydrolysis in a .... the hetero-yellow endosperm type sorghum had the highest avarage daily gains (ADGs), whereas pigs fed the maize-.

  2. Reaction

    African Journals Online (AJOL)

    abp

    19 oct. 2017 ... Reaction to Mohamed Said Nakhli et al. concerning the article: "When the axillary block remains the only alternative in a 5 year old child". .... Bertini L1, Savoia G, De Nicola A, Ivani G, Gravino E, Albani A et al ... 2010;7(2):101-.

  3. Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1, 10-phenanthroline)(2) building blocks

    NARCIS (Netherlands)

    Yu, Yunfang; Wei, Yongqin; Broer, Ria; Sa, Rongjian; Wu, Kechen

    Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen)(2)(H2O)(HTST)] center dot 2H(2)O (1), [CO3(phen)(6) (H2O)(2)(TST)(2)]center dot 7H(2)O (2), and [CO2Cu(phen)(6)(H2O)(2)(TST)(2)]center dot 10H(2)O (3), have been synthesized by the reactions of a new

  4. The Synthesis of the Stable IVDU Derivative for Imaging HSV-1 TK Expression

    International Nuclear Information System (INIS)

    Kim, Eun Jung; Choi, Tae Hyun; Ahn, Soon Hyuk; Kim, Byoung Soo; Park, Hyun; Cheon, Gi Jeong; An, Gwang Il; Rhee, Hak June

    2009-01-01

    5-iododeoxyuridine analogues have been exclusively developed for the potential antiviral and antitumor therapeutic agents. In this study, we synthesized carbocyclic radioiododeoxyuridineanalogue (ddIVDU) and carbocyclic intermediate as efficient carbocyclic radiopharmaceuticals. The synthesis is LAH reduction, hetero Diels-Alder reaction as key reactions including Pd(0)-catalyzed coupling reaction together with organotin. MCA-RH7777 (MCA) and MCA-tk (HSV1-tk positive) cells were treated with various concentration of carbocyclic ddIVDU, and GCV. Cytotoxicity was measured by the MTS methods. For in vitro uptake study, MCA and MCA-tk cells were incubated with 1uCi of [ 125 I]carbocyclic ddIVDU. Accumulated radioactivity was measured after various incubation times. The synthesis of ddIVDU and precursor for radioiodination were achieved from cyclopentadiene in good overall yield, respectively. The radioiododemetallation for radiolabeling gave more than 80% yield with > 95% radiochemical purity. GCV was more toxic than carbocyclic ddIVDU in MCA-tk cells. Accumulation of [ 125 I]carbocyclic ddIVDU was higher in MCA-tk cells than MCA cells. Biological data reveal that ddIVDU is stable in vitro, less toxic than ganciclovir (GCV), and selective in HSV1-tk expressed cells. Thus, this new carbocyclic nucleoside, referred to in this paper as carbocyclic 2',3'-didehydro-2',3'-dideoxy-5- iodovinyluridine (carbocyclic ddIVDU), is a potential imaging probe for HSV1-tk

  5. Synthesis and 1,3-Dipolar Cycloaddition Reactions of Chiral Maleimides

    Directory of Open Access Journals (Sweden)

    Lubor Fisera

    1997-02-01

    Full Text Available New routes to the synthesis of various novel chiral maleimides are described. The oxabicyclic anhydride 2 readily available exo-Diels-Alder adduct of furan and maleic anhydride was used as a vehicle, which in turn reacted with hydrochlorides of amino acids 3a-f in the presence of Et3N with release of furan to give the requisite novel chiral imides 4a-f in good to moderate yields. The stereoselectivity of 1,3-dipolar cycloaddition of nitrile oxides with prepared chiral imides 4a-f is investigated.

  6. Quinone methides tethered to naphthalene diimides as selective G-quadruplex alkylating agents.

    Science.gov (United States)

    Di Antonio, Marco; Doria, Filippo; Richter, Sara N; Bertipaglia, Carolina; Mella, Mariella; Sissi, Claudia; Palumbo, Manlio; Freccero, Mauro

    2009-09-16

    We have developed novel G-quadruplex (G-4) ligand/alkylating hybrid structures, tethering the naphthalene diimide moiety to quaternary ammonium salts of Mannich bases, as quinone-methide precursors, activatable by mild thermal digestion (40 degrees C). The bis-substituted naphthalene diimides were efficiently synthesized, and their reactivity as activatable bis-alkylating agents was investigated in the presence of thiols and amines in aqueous buffered solutions. The electrophilic intermediate, quinone-methide, involved in the alkylation process was trapped, in the presence of ethyl vinyl ether, in a hetero Diels-Alder [4 + 2] cycloaddition reaction, yielding a substituted 2-ethoxychroman. The DNA recognition and alkylation properties of these new derivatives were investigated by gel electrophoresis, circular dichroism, and enzymatic assays. The alkylation process occurred preferentially on the G-4 structure in comparison to other DNA conformations. By dissecting reversible recognition and alkylation events, we found that the reversible process is a prerequisite to DNA alkylation, which in turn reinforces the G-quadruplex structural rearrangement.

  7. heteroHarvest: Harvesting Information from Heterogeneous Sources

    DEFF Research Database (Denmark)

    Qureshi, Pir Abdul Rasool; Memon, Nasrullah; Wiil, Uffe Kock

    2011-01-01

    The abundance of information regarding any topic makes the Internet a very good resource. Even though searching the Internet is very easy, what remains difficult is to automate the process of information extraction from the available online information due to the lack of structure and the diversity...... in the sharing methods. Most of the times, information is stored in different proprietary formats, complying with different standards and protocols which makes tasks like data mining and information harvesting very difficult. In this paper, an information harvesting tool (heteroHarvest) is presented...... with objectives to address these problems by filtering the useful information and then normalizing the information in a singular non hypertext format. Finally we describe the results of experimental evaluation. The results are found promising with an overall error rate equal to 6.5% across heterogeneous formats....

  8. Synthesis of 1-Methyl-3-oxo-7-oxabicyclo[2.2.1]hept-5-ene-2-carboxylic Acid Methyl Ester

    Directory of Open Access Journals (Sweden)

    Gil Valdo José da Silva

    2005-11-01

    Full Text Available A simple and efficient method for the preparation of 1-methyl-3-oxo-7- oxabicyclo[2.2.1]hept-5-en-2-carboxylic acid methyl ester (1 is described. The first step is a highly regioselective Diels-Alder reaction between 2-methylfuran and methyl-3-bromo- propiolate. A remarkably difficult ketal hydrolysis reaction was effected by treatment with HCl, a simple reagent that was shown to be more efficient, in this case, than commonly used more elaborate methods.

  9. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    B3LYP/6-31G() calculations were performed to obtain all the transition states and products for the 128 distinct reaction channels of Diels-Alder reactions by taking all possible combinations from a series of dienes (1N-a, 1N-b, 2N, 1P-a, 1P-b, 2P, 1O, 1S) and dienophiles (NE, PE, OE, SE, AE, OHE, MeE, CNE).

  10. Towards the total synthesis of Stawamycin. Synthesis of C11-C21 fragment

    Directory of Open Access Journals (Sweden)

    Dias Luiz C.

    2001-01-01

    Full Text Available The carbocyclic (C11-C21 fragment of Stawamycin has been prepared by a sequence involving 11 steps (10% overall yield from methyl (R-(--3-hydroxy-2-methylpropionate. Key steps are Pd-catalyzed Stille coupling reaction between a vinyl iodide and a vinylstannane followed by an intramolecular Diels-Alder cycloaddition reaction to afford the desired adduct as the major isomer together with three other possible adducts in 78% overall yield.

  11. Synthesis of Hydroxynaphtharines; Sintesis de naftazarinas hidroxiladas

    Energy Technology Data Exchange (ETDEWEB)

    Farina, F.; Fernandez, E.; Gimeno, V.; Valderrama, J.A. [Instituto de Quimica Organica General, CSIC, Madrid (Spain)

    1995-12-01

    A variety of naththazarines type 4 and 8 were prepared through Diels-Alder reactions of substituted 1,4-benzoquinones with 1,3-dienes. Thiele-Winter reaction of 5 afforded 6 which by chromic oxidation yielded naththazarines 7 and/or naphthoquinones 9. Hydroxynaphthazarines of type 8 were synthesized from 5 through 2,3-epoxides of the type 14. The structural study of the products, by H-NMR, showed the typical tautomerism of the naphthazarine system. 23 refs.

  12. Palladium-Catalyzed Decarboxylative γ-Olefination of 2,5-Cyclohexadiene-1-carboxylic Acid Derivatives with Vinyl Halides.

    Science.gov (United States)

    Chang, Chi-Hao; Chou, Chih-Ming

    2018-04-06

    This study explores a Pd-catalyzed decarboxylative Heck-type Csp 3 -Csp 2 coupling reaction of 2,5-cyclohexadiene-1-carboxylic acid derivatives with vinyl halides to provide γ-olefination products. The olefinated 1,3-cyclohexadienes can be further oxidized to produce meta-alkylated stilbene derivatives. Additionally, the conjugated diene products can also undergo a Diels-Alder reaction to produce a bicyclo[2.2.2]octadiene framework.

  13. Recycling tires? Reversible crosslinking of poly(butadiene).

    Science.gov (United States)

    Trovatti, Eliane; Lacerda, Talita M; Carvalho, Antonio J F; Gandini, Alessandro

    2015-04-01

    Furan-modified poly(butadiene) prepared by the thiol-ene click reaction is crosslinked with bismaleimides through the Diels-Alder reaction, giving rise to a novel recyclable elastomer. This is possible because of the thermal reversibility of the adducts responsible for the formation of the network. The use of this strategy provides the possibility to produce recyclable tires. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Synthesis research of squalene synthetase inhibitor CP-263, 114. How is skeleton construction carried out?; Sukuaren gosei koso sogaizai CP-263,114 no gosei kenkyu - ikanishite kokkaku kochiku wo okonauka?

    Energy Technology Data Exchange (ETDEWEB)

    Matsushima, Y. [Tokyo Inst. of Tech., Tokyo (Japan)

    2000-01-01

    CP-263, 114 isolated as a squalene synthetase inhibitor and the decyclization of CP-225, 917 was not only expected to be a lead chemical compound of the hypercholesterolemia medicine, but also have collected the attention of the organic synthetic chemistry researchers all over the world from the ring structure of advanced oxygen functionalization. In the CP- chemical compound, the constructive method of the bicyclo ring structure is a key of the synthesis, there are three reports to use the intramolecular Diels-Alder reaction (Fukuyama) and the siloxy-Cope rearrangement (Leighton), intramolecular Heck reaction (Danishefsky) as a result of succeeding in including the foothold to the side-chain lactol ring. Recently, Nicolaou et al. succeeded for the first time in the total synthesis racemic modification shell. They carried out the skeleton construction by the intramolecular Diels-Alder reaction, and constructed the maleic anhydride structure in taking the ketone as a foothold. (NEDO)

  15. Spectrophotometric investigation of the hetero-association of Caffeine and thiazine dye in aqueous solution

    Science.gov (United States)

    Bolotin, P. A.; Baranovsky, S. F.; Evstigneev, M. P.

    2006-06-01

    The self-association of thiazine dye, Methylene Blue (MB), and its hetero-association with Caffeine (CAF), were studied in aqueous solution by means of spectrophotometry in the visible range of spectrum. Concentration and temperature dependences of molar absorption of the interacting molecules were used to analyse dynamic equilibrium in solution in terms of two-component model of molecular hetero-association. The magnitudes of equilibrium dimerization and hetero-association constants as well as thermodynamic parameters, enthalpy and entropy, were determined. The calculation of the fraction of different types of associates in the mixed solution, containing Methylene Blue and Caffeine, was done. It was concluded that the hetero-association of Methylene Blue and Caffeine molecules results in lower effective concentration of the dye in solution, which may account for the alteration of its biological activity.

  16. Biomedical Applications of Gold Nanoparticles Functionalized Using Hetero-Bifunctional Poly(ethylene glycol) Spacer

    National Research Council Canada - National Science Library

    Fu, Wei; Shenoy, Dinesh; Li, Jane; Crasto, Curtis; Jones, Graham; Dimarzio, Charles; Sridhar, Srinivas; Amiji, Mansoor

    2005-01-01

    To increase the targeting potential, circulation time, and the flexibility of surface-attached biomedically-relevant ligands on gold nanoparticles, hetero-bifunctional poly(ethylene glycol) (PEG, MW 1,500...

  17. Palladium Gate All Around - Hetero Dielectric -Tunnel FET based highly sensitive Hydrogen Gas Sensor

    Science.gov (United States)

    Madan, Jaya; Chaujar, Rishu

    2016-12-01

    The paper presents a novel highly sensitive Hetero-Dielectric-Gate All Around Tunneling FET (HD-GAA-TFET) based Hydrogen Gas Sensor, incorporating the advantages of band to band tunneling (BTBT) mechanism. Here, the Palladium supported silicon dioxide is used as a sensing media and sensing relies on the interaction of hydrogen with Palladium-SiO2-Si. The high surface to volume ratio in the case of cylindrical GAA structure enhances the fortuities for surface reactions between H2 gas and Pd, and thus improves the sensitivity and stability of the sensor. Behaviour of the sensor in presence of hydrogen and at elevated temperatures is discussed. The conduction path of the sensor which is dependent on sensors radius has also been varied for the optimized sensitivity and static performance analysis of the sensor where the proposed design exhibits a superior performance in terms of threshold voltage, subthreshold swing, and band to band tunneling rate. Stability of the sensor with respect to temperature affectability has also been studied, and it is found that the device is reasonably stable and highly sensitive over the bearable temperature range. The successful utilization of HD-GAA-TFET in gas sensors may open a new door for the development of novel nanostructure gas sensing devices.

  18. High-efficiency super capacitors based on hetero-structured α-MnO2 nanorods

    International Nuclear Information System (INIS)

    Ghouri, Zafar Khan; Shaheer Akhtar, M.; Zahoor, Awan; Barakat, Nasser A.M.; Han, Weidong; Park, Mira; Pant, Bishweshwar; Saud, Prem Singh; Lee, Cho Hye; Kim, Hak Yong

    2015-01-01

    Highlights: • Hetero-structured α-MnO 2 nanorods are prepared by a facile hydrothermal route. • It is applied as active electrode materials for supercapacitor. • A high specific capacitance of 298 Fg −1 with a superior long term cyclic stability is achieved. • Supercapacitor shows high specific capacitance retention 94% after 1000 cycles. - Abstract: Hetero-structured manganese dioxide nanorods with α phase (α-MnO 2 ) were prepared by a facile hydrothermal route at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements were used to characterize the prepared hetero-structured α-MnO 2 nanorods. Supercapacitive performance of the hetero-structured α-MnO 2 nanomaterials as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium. The MnO 2 hetero-structure with 2 × 2 tunnels constructed from double chains of octahedral [MnO 6 ] structure yield a significantly high specific capacitance of 298 Fg −1 at 5 mV s −1 and demonstrated a superior long term cyclic stability, with specific capacitance retention about 94% after 1000 cycles. The superior supercapacitive performance of the hetero-structured α-MnO 2 electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport

  19. Effect of doping on electronic properties of double-walled carbon and boron nitride hetero-nanotubes

    International Nuclear Information System (INIS)

    Majidi, R.; Ghafoori Tabrizi, K.; Jalili, S.

    2009-01-01

    The effect of boron nitride (BN) doping on electronic properties of armchair double-walled carbon and hetero-nanotubes is studied using ab initio molecular dynamics method. The armchair double-walled hetero-nanotubes are predicted to be semiconductor and their electronic structures depend strongly on the electronic properties of the single-walled carbon nanotube. It is found that electronic structures of BN-doped double-walled hetero-nanotubes are intermediate between those of double-walled boron nitride nanotubes and double-walled carbon and boron nitride hetero-nanotubes. Increasing the amount of doping leads to a stronger intertube interaction and also increases the energy gap.

  20. Effect of doping on electronic properties of double-walled carbon and boron nitride hetero-nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Majidi, R. [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Ghafoori Tabrizi, K., E-mail: K-TABRIZI@sbu.ac.i [Department of Physics, Shahid Beheshti University, Evin, Tehran 19839-63113 (Iran, Islamic Republic of); Jalili, S. [Department of Chemistry, K.N. Toosi University of Technology, Tehran 16315-1618 (Iran, Islamic Republic of)

    2009-11-01

    The effect of boron nitride (BN) doping on electronic properties of armchair double-walled carbon and hetero-nanotubes is studied using ab initio molecular dynamics method. The armchair double-walled hetero-nanotubes are predicted to be semiconductor and their electronic structures depend strongly on the electronic properties of the single-walled carbon nanotube. It is found that electronic structures of BN-doped double-walled hetero-nanotubes are intermediate between those of double-walled boron nitride nanotubes and double-walled carbon and boron nitride hetero-nanotubes. Increasing the amount of doping leads to a stronger intertube interaction and also increases the energy gap.

  1. Design and Synthesis of Aza-Bicyclononene Dienophiles for Rapid Fluorogenic Ligations

    Czech Academy of Sciences Publication Activity Database

    Siegl, Sebastian J.; Vázquez, Arcadio; Dzijak, Rastislav; Dračínský, Martin; Galeta, Juraj; Rampmaier, Robert; Klepetářová, Blanka; Vrábel, Milan

    2018-01-01

    Roč. 24, č. 10 (2018), s. 2426-2432 ISSN 0947-6539 R&D Projects: GA ČR GJ15-06020Y; GA MŠk(CZ) LO1304 EU Projects: European Commission(XE) 677465 - SWEETOOLS Institutional support: RVO:61388963 Keywords : cell labeling * Diels-Alder reaction * fluorogenic * tetrazines * trans-cyclooctene Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 5.317, year: 2016

  2. CuO and Ag2O/CuO Catalyzed Oxidation of Aldehydes to the Corresponding Carboxylic Acids by Molecular Oxygen

    Directory of Open Access Journals (Sweden)

    Yaowu Sha

    2008-04-01

    Full Text Available Furfural was oxidized to furoic acid by molecular oxygen under catalysis by 150nm-sized Ag2O/CuO (92% or simply CuO (86.6%. When 30 nm-size catalyst was used,the main product was a furfural Diels-Alder adduct. Detailed reaction conditions andregeneration of catalysts were investigated. Under optimal conditions, a series of aromaticand aliphatic aldehydes were oxidized to the corresponding acids in good yields.

  3. One-pot synthesis of phthalazines and pyridazino-aromatics: a novel strategy for substituted naphthalenes.

    Science.gov (United States)

    Kessler, Simon N; Wegner, Hermann A

    2012-07-06

    A new one-pot strategy for the synthesis of phthalazines and pyridazino-aromatics starting from aromatic aldehydes has been developed. A variety of substituents ranging from electron withdrawing to donating is tolerated furnishing the desired 1,2-diazine in good to excellent yields. The products have been applied to the bidentate Lewis acid catalyzed inverse electron-demand Diels-Alder (IEDDA) reaction opening a novel two-step entry into substituted naphthalenes, such as Naproxen.

  4. Synthesis and Structure of D3h-Symmetric Triptycene Trimaleimide

    Directory of Open Access Journals (Sweden)

    Anthony Linden

    2010-01-01

    Full Text Available A new D3h symmetric triptycene derivative has been synthesized with the aim of obtaining molecules that are able to assemble into porous structures, and can be used in the development of new ligands. The synthesis involves a Diels-Alder reaction as the key step, followed by an oxidation and the formation of a maleimide ring. Triptycene trimaleimide furnished single crystals which have been analyzed by means of X-ray diffraction.

  5. Chloroacetamide-Linked Nucleotides and DNA for Cross-Linking with Peptides and Proteins

    Czech Academy of Sciences Publication Activity Database

    Olszewska, Agata; Pohl, Radek; Brázdová, Marie; Fojta, Miroslav; Hocek, Michal

    2016-01-01

    Roč. 27, č. 9 (2016), s. 2089-2094 ISSN 1043-1802 R&D Projects: GA ČR GBP206/12/G151 Institutional support: RVO:61388963 ; RVO:68081707 Keywords : tumor suppressor p53 * Diels-Alder reaction * reductive amination Subject RIV: CC - Organic Chemistry Impact factor: 4.818, year: 2016 http://pubs.acs.org/doi/full/10.1021/acs.bioconjchem.6b00342

  6. Biomimetic Aerobic C–H Olefination of Cyclic Enaminones at Room Temperature: Development toward the Synthesis of 1,3,5-Trisubstituted Benzenes

    Science.gov (United States)

    Yu, Yi-Yun

    2014-01-01

    A green and mild protocol for the dehydrogenative olefination of cyclic enaminones was devised via palladium catalysis at room temperature using oxygen as the terminal oxidant. The synthetic utility of the olefinated cyclic enaminones afforded a series of unique 1,3,5-trisubstituted benzenes via an unanticipated Diels-Alder tandem reaction. The broad substrate scope and good yields achieved with this new protocol provide an alternative pathway for arene functionalization. PMID:25071423

  7. Biomimetic Aerobic C-H Olefination of Cyclic Enaminones at Room Temperature: Development toward the Synthesis of 1,3,5-Trisubstituted Benzenes.

    Science.gov (United States)

    Yu, Yi-Yun; Georg, Gunda I

    2014-04-14

    A green and mild protocol for the dehydrogenative olefination of cyclic enaminones was devised via palladium catalysis at room temperature using oxygen as the terminal oxidant. The synthetic utility of the olefinated cyclic enaminones afforded a series of unique 1,3,5-trisubstituted benzenes via an unanticipated Diels-Alder tandem reaction. The broad substrate scope and good yields achieved with this new protocol provide an alternative pathway for arene functionalization.

  8. A Tetrazine-Labile Vinyl Ether Benzyloxycarbonyl Protecting Group (VeZ): An Orthogonal Tool for Solid-Phase Peptide Chemistry.

    Science.gov (United States)

    Staderini, Matteo; Gambardella, Alessia; Lilienkampf, Annamaria; Bradley, Mark

    2018-06-01

    The vinyl ether benzyloxycarbonyl (VeZ) protecting group is selectively cleaved by treatment with tetrazines via an inverse electron-demand Diels-Alder reaction. This represents a new orthogonal protecting group for solid-phase peptide synthesis, with Fmoc-Lys(VeZ)-OH as a versatile alternative to Fmoc-Lys(Alloc)-OH and Fmoc-Lys(Dde)-OH, as demonstrated by the synthesis of two biologically relevant cyclic peptides.

  9. Diels-Alders adducts of C-60 and esters of 3-(1-indenyl)-propionic acid : alternatives for [60]PCBM in polymer:fullerene solar cells

    NARCIS (Netherlands)

    Sieval, Alexander B.; Treat, Neil D.; Rozema, Desiree; Hummelen, Jan C.; Stingelin, Natalie

    2015-01-01

    A series of new, easily synthesized C-60-fullerene derivatives is introduced that allow for optimization of the interactions between rr-P3HT and the fullerene by systematic variation of the size of the ester group. Two compounds gave overall cell efficiencies of 4.8%, clearly outperforming [60]PCBM

  10. Synthesis of an Imidazolidinone Organocatalyst and Its Application in a Diels-Alder Cycloaddition: A Multistep Experiment for the Organic Teaching Laboratory

    Science.gov (United States)

    Murphy, John J.; Driver, Ross B.; Walsh, Ria; Stephens, John C.

    2016-01-01

    The development of novel, high-yielding, and selective methodologies for the asymmetric synthesis of stereocenters is at the forefront of modern synthetic chemistry research. Organocatalysis can now be viewed as a viable alternative to the use of the sometimes toxic transition-metal catalysts. In this experiment, the simple synthesis of an achiral…

  11. Hetero-azeotropic distillation: combining fungal dehydration and lipid extraction.

    Science.gov (United States)

    Tough, A J; Isabella, B L; Beattie, J E; Herbert, R A

    2000-01-01

    A low-cost single-stage laboratory process combining fungal dehydration and lipid extraction was compared with a traditional two-stage method employing freeze-drying and subsequent mechanical disruption in the presence of solvent. The ability of a number of organic solvents to form hetero-azeotropes with water was exploited. Chloroform, cyclohexane and hexane were assessed in their abilities to both dry and extract lipid from the oleaginous phycomycete Mortierella alpina (ATCC 32222). Drying rate and lipid extraction were maximised under conditions that prevented fungal agglomeration. The total processing time was limited by the rate of dehydration rather than by the rate of lipid extraction. In all cases azeotropic distillation facilitated a greater rate of dehydration than was possible with freeze-drying. A consequent reduction in overall processing time was observed. Uniquely, both the solvent used and the mode of mixing employed controlled the morphology of the aggregates formed during distillation. In combination with mild mixing chloroform discouraged agglomeration whereas cyclohexane and hexane promoted aggregation. Successful lipid extraction was dependent on the use of dry biomass rather than on the application of heat to effect distillation. Neither the application of heat nor the solvent employed had any significant effect on the lipid composition of the extracted oil.

  12. Orthogonal Clickable Iron Oxide Nanoparticle Platform for Targeting, Imaging, and On-Demand Release.

    Science.gov (United States)

    Guldris, Noelia; Gallo, Juan; García-Hevia, Lorena; Rivas, José; Bañobre-López, Manuel; Salonen, Laura M

    2018-04-12

    A versatile iron oxide nanoparticle platform is reported that can be orthogonally functionalized to obtain highly derivatized nanomaterials required for a wide variety of applications, such as drug delivery, targeted therapy, or imaging. Facile functionalization of the nanoparticles with two ligands containing isocyanate moieties allows for high coverage of the surface with maleimide and alkyne groups. As a proof-of-principle, the nanoparticles were subsequently functionalized with a fluorophore as a drug model and with biotin as a targeting ligand towards tumor cells through Diels-Alder and azide-alkyne cycloaddition reactions, respectively. The thermoreversibility of the Diels-Alder product was exploited to induce the on-demand release of the loaded molecules by magnetic hyperthermia. Additionally, the nanoparticles were shown to target cancer cells through in vitro experiments, as analyzed by magnetic resonance imaging. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. New faces of porous Prussian blue: interfacial assembly of integrated hetero-structures for sensing applications.

    Science.gov (United States)

    Kong, Biao; Selomulya, Cordelia; Zheng, Gengfeng; Zhao, Dongyuan

    2015-11-21

    Prussian blue (PB), the oldest synthetic coordination compound, is a classic and fascinating transition metal coordination material. Prussian blue is based on a three-dimensional (3-D) cubic polymeric porous network consisting of alternating ferric and ferrous ions, which provides facile assembly as well as precise interaction with active sites at functional interfaces. A fundamental understanding of the assembly mechanism of PB hetero-interfaces is essential to enable the full potential applications of PB crystals, including chemical sensing, catalysis, gas storage, drug delivery and electronic displays. Developing controlled assembly methods towards functionally integrated hetero-interfaces with adjustable sizes and morphology of PB crystals is necessary. A key point in the functional interface and device integration of PB nanocrystals is the fabrication of hetero-interfaces in a well-defined and oriented fashion on given substrates. This review will bring together these key aspects of the hetero-interfaces of PB nanocrystals, ranging from structure and properties, interfacial assembly strategies, to integrated hetero-structures for diverse sensing.

  14. Pathways for the reaction of the butadiene radical cation, [C{sub 4}H{sub 6}]{sup {sm{underscore}bullet}+}, with ethylene

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, M.; Schaefer, H.F. III

    1999-11-04

    The Diels-Alder (DA) reaction, a [4+2] cycloaddition used to build six membered rings, is one of the most valuable cycloadditions in organic chemistry. In cases where the ene does not add to the diene (even with the help of Lewis acids which may reduce the electron density of one reactant by complexation) one electron oxidation (by an oxidizing agent or by photoinduced electron transfer (PET)) may accelerate the reaction. Reaction pathways for the addition of ethylene, 1, to butadiene radical cation, 2, involving H-shifts have been investigated at the coupled cluster UCCSD(T)/DZP//UMP2(fc)/DZP + ZPE level of theory. Activation energies are relatively low for [1,2]- (10.0 kcal mol{sup {minus}1}, TS-4/20) and [1,5]-hydrogen shifts (7.7 kcal mol{sup {minus}1}, TS-4/26) but are relatively high for [1,4]-(33.8 kcal mol{sup {minus}1}, TS-4/14) and [1,3]-H shifts (e.g., 42.2 kcal mol{sup {minus}1}, TS-12/13; 57.2 kcal mol{sup {minus}1}, TS-16/21). Several rearrangement reactions have been found to occur below the energy limit of separated 1 + 2. The cyclopentenyl cation, [C{sub 5}{sub 7}]{sup +}, 18, experimentally observed as reaction product of the butadiene radical cation, 2, and ethylene, 1, in the gas phase may origin from various reaction pathways. The following reaction sequence has been identified as the lowest in energy path from 1 + 2 to 18 with all relative energies ({Delta}E{degree}) of transition structures below that of 1 + 2: (a) ethylene adds to the butadiene radical cation to form an open-chain distonic intermediate, that undergoes a [1,5]-H shift to the 1,4-hexadiene radical cation; (b) intramolecular [2+1] cycloaddition to methyl-cyclopenta-1,3-diyl intermediates, which can interconvert through a bicyclo[2.1.0]pentane radical cation; (c) [1,2]-H shift to the 3-methyl cyclopentene radical cation; (d) methyl radical loss to give cyclopenten-3-yl cation. Along this reaction pathway, {Delta}H{sup 298} is below that of 1 + 2; max. ({Delta}G{sup 298} by

  15. Structural variability in uranyl-lanthanide hetero-metallic complexes with DOTA and oxalato ligands

    International Nuclear Information System (INIS)

    Thuery, P.

    2009-01-01

    Four novel 4f-5f hetero-metallic complexes could be obtained from the reaction of uranyl and lanthanide nitrates with DOTA (H 4 L) under hydrothermal conditions. In all cases, as in the previous examples reported, additional oxalato ligands are formed in situ. Variations in the stoichiometry of the final products and the presence of hydroxo ions in some cases appear to result in a large structural variability. In the two isomorphous complexes [(UO 2 ) 2 Ln 2 (L) 2 (C 2 O 4 )] with Ln = Sm(1) or Eu(2), the lanthanide ion is located in the N 4 O 4 site and is also bound to a carboxylate oxygen atom from a neighbouring unit, to give zigzag chains which are further linked to one another by [(UO 2 ) 2 (C 2 O 4 )] 2+ di-cations, resulting in the formation of a 3D framework. In [(UO 2 ) 4 Gd 2 (L) 2 (C 2 O 4 ) 3 (H 2 O) 6 ].2H 2 O (3), 2D bilayer subunits of the 'double floor' type with uranyl oxalate pillars are assembled into a 3D framework by other, disordered uranyl ions. [(UO 2 ) 2 Gd(L)(C 2 O 4 )(OH)].H 2 O (4) is a 2D assembly in which cationic {[(UO 2 ) 2 (C 2 O 4 )(OH)] + } n chains are linked to one another by the [Gd(L)] - groups. The most notable feature of this compound is the environment of the 4f ion, which is eight-coordinate and twisted square anti-prismatic (TSA'), instead of nine-coordinate mono-capped square anti-prismatic (SA), as generally observed in DOTA complexes of gadolinium(III) and similarly-sized ions. (author)

  16. Distinguish self- and hetero-perceived stress through behavioral imaging and physiological features.

    Science.gov (United States)

    Spodenkiewicz, Michel; Aigrain, Jonathan; Bourvis, Nadège; Dubuisson, Séverine; Chetouani, Mohamed; Cohen, David

    2018-03-02

    Stress reactivity is a complex phenomenon associated to multiple and multimodal expressions. Response to stressors has an obvious survival function and may be seen as an internal regulation to adapt to threat or danger. The intensity of this internal response can be assessed as the self-perception of the stress response. In species with social organization, this response also serves a communicative function, so-called hetero-perception. Our study presents multimodal stress detection assessment - a new methodology combining behavioral imaging and physiological monitoring for analyzing stress from these two perspectives. The system is based on automatic extraction of 39 behavioral (2D+3D video recording) and 62 physiological (Nexus-10 recording) features during a socially evaluated mental arithmetic test. The analysis with machine learning techniques for automatic classification using Support Vector Machine (SVM) show that self-perception and hetero-perception of social stress are both close but different phenomena: self-perception was significantly correlated with hetero-perception but significantly differed from it. Also, assessing stress with SVM through multimodality gave excellent classification results (F1 score values: 0.9±0.012 for hetero-perception and 0.87±0.021 for self-perception). In the best selected feature subsets, we found some common behavioral and physiological features that allow classification of both self- and hetero-perceived stress. However, we also found the contributing features for automatic classifications had opposite distributions: self-perception classification was mainly based on physiological features and hetero-perception was mainly based on behavioral features. Copyright © 2017. Published by Elsevier Inc.

  17. An Au/Si hetero-nanorod-based biosensor for Salmonella detection

    Energy Technology Data Exchange (ETDEWEB)

    Fu Junxue; Zhao Yiping [Physics and Astronomy Department, University of Georgia, Athens, GA 30602 (United States); Park, Bosoon; Siragusa, Greg [USDA, ARS, Russell Research Center, Athens, GA 30605 (United States); Jones, Les; Tripp, Ralph [Department of Infectious Diseases, College of Veterinary Medicine, University of Georgia, Athens, GA 30602 (United States); Cho, Yong-Jin [Korea Food Research Institute, Songnam (Korea, Republic of)], E-mail: zhaoy@physast.uga.edu

    2008-04-16

    We present a novel and effective food-borne bacteria detection method. A hetero-structured silicon/gold nanorod array fabricated by the glancing angle deposition method is functionalized with anti-Salmonella antibodies and organic dye molecules. Due to the high aspect ratio nature of the Si nanorods, dye molecules attached to the Si nanorods produce an enhanced fluorescence upon capture and detection of Salmonella. This bio-functional hetero-nanorod detection method has great potential in the food safety industry as well as in biomedical diagnostics.

  18. Gaschromatographic and mass spectroscopic investigations of tall oil rosin acids and diterpenioc compounds and modified diterpene acids

    International Nuclear Information System (INIS)

    Mayr, M.

    1984-12-01

    Diterpene resin acids are important constituents of the coniferous wood. The composition of these nonvolatile extractives have been studied by a number of investigations; both naturally occurring resins (oleoresin) and distillation products of the alkaline sulfate pulping process (tall oil) were analyzed. These mixtures find important uses in chemical intermediates, paper sizes, ester gums, coatings and numerous other applications. Owing to the more ameliorate physical properties a major part of tall oil resin acids is chemically modified and is used in intermediate chemicals. Such modifications are the disproportionation in the presence of certain catalysts and the formation of Diels-Alder adducts. The present study was undertaken to obtain detailed information of the overall composition of diterpenoid compounds and to achieve a separation of the complex natural and tall oil mixtures using high resolution glass capillary columns. Furthermore, one objective was to characterize the identified diterpene compounds and Diels-Alder adducts by relative retention values. Additionally the presence of some major adduct components in the modified samples was checked by comparison with pure specimens, independently synthesized or purified by crystallization and the mechanism of the Diels-Alder reaction was investigated. A compilation of the mass spectra of the substances detected in the different samples closes this work. (Author)

  19. Regioselectivity in the hetero-Diels–Alder reactions of styrenes with ...

    Indian Academy of Sciences (India)

    SAFA ALI-ASGARI

    Herrera R, Nagarajan A, Morales M A, Méndez F,. Jiménez-Vázquez H A, Gerardo Zepeda L and Tama- riz J 2001 Regio- and Stereoselectivity of Captodative. Olefins in 1,3-Dipolar Cycloadditions. A DFT/HSAB. Theory Rationale for the Observed Regiochemistry of. Nitrones J. Org. Chem. 66 1252. 19. Chattaraj P K, Sarkar ...

  20. Influence of Ti–O–Si hetero-linkages in the photocatalytic degradation of Rhodamine B

    NARCIS (Netherlands)

    Rasalingam, S; Kibombo, H.S.; Wu, C.M.; Budhi, S.; Peng, R.; Baltrusaitis, Jonas; Koodali, R.T.

    2013-01-01

    The influence of Ti–O–Si hetero-linkages in the degradation of Rhodamine B (RhB) dye over TiO2–SiO2 xerogels is exemplified by XPS analysis. We demonstrate a relationship between the percentage surface content of Ti–O–Si and the rate of photocatalytic degradation of RhB. Our detailed surface

  1. Injustice to transsexual women in a hetero-normatie healthcare system

    Directory of Open Access Journals (Sweden)

    Douglas Newman-Valentine

    2014-11-01

    Conclusion: A hetero-normative healthcare system has a negative impact on the health of transsexual women and will cause them to be marginalised. This could contribute to both homoand trans-phobia that will in turn strengthen the belief that transsexual women are un-African.

  2. Hetero-interaction between Gouy-Stern double layers : charge and potential regulation

    NARCIS (Netherlands)

    Lyklema, J.; Duval, J.F.L.

    2005-01-01

    This issue of Advances is devoted to the memory of Hans-Joachim Schulze who, before his untimely death, made substantial contributions in the domains of flotation, wetting and particle interaction, often under adverse working conditions. Many of his publications involve hetero-interaction between

  3. Synthesis and optical spectroscopy of (hetero)-nanocrystals: An exciting interplay between Chemistry and Physics

    NARCIS (Netherlands)

    Groeneveld, E.

    2012-01-01

    This thesis describes the synthesis and study of the optical properties of various colloidal semiconductor (hetero)nanocrystals ((H)NCs). Before the experimental results are discussed in detail, the essential theoretical background on the chemical and physical aspects of this work is provided in

  4. Catalytic Enantioselective Synthesis of Naturally Occurring Butenolides via Hetero-Allylic Alkylation and Ring Closing Metathesis

    NARCIS (Netherlands)

    Mao, Bin; Geurts, Koen; Fañanás-Mastral, Martín; Zijl, Anthoni W. van; Fletcher, Stephen P.; Minnaard, Adriaan J.; Feringa, Bernard

    2011-01-01

    An efficient catalytic asymmetric synthesis of chiral γ-butenolides was developed based on the hetero-allylic asymmetric alkylation (h-AAA) in combination with ring closing metathesis (RCM). The synthetic potential of the h-AAA-RCM protocol was illustrated with the facile synthesis of (-)-whiskey

  5. Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1,10-phenanthroline) 2 building blocks

    Science.gov (United States)

    Yu, Yunfang; Wei, Yongqin; Broer, Ria; Sa, Rongjian; Wu, Kechen

    2008-03-01

    Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen) 2(H 2O)(HTST)]·2H 2O ( 1), [Co 3(phen) 6(H 2O) 2(TST) 2]·7H 2O ( 2), and [Co 2Cu(phen) 6(H 2O) 2(TST) 2]·10H 2O ( 3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H 3TST) with the M2+ ( M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). Complex 1 contains a cis-Co(II)(phen) 2 building block and an HTST as monodentate ligand; complex 2 consists of two TST as bidentate ligands connecting one trans- and two cis-Co(II)(phen) 2 building blocks; complex 3 is formed by replacing the trans-Co(II)(phen) 2 in 2 with a trans-Cu(II)(phen) 2, which is the first reported hetero-trinuclear supramolecular complex containing both the Co(II)(phen) 2 and Cu(II)(phen) 2 as building blocks. The study shows the flexible multifunctional self-assembly capability of the H 3TST ligands presenting in these supramolecular complexes through coordinative, H-bonding and even π- π stacking interactions. The photoluminescent optical properties of these complexes are also investigated and discussed as well as the second-order nonlinear optical properties of 1.

  6. Improved electron density through hetero-junction binary sensitized TiO2/ CdTe / D719 system as photoanode for dye sensitized solar cell

    Science.gov (United States)

    Pandey, A. K.; Ahmad, Muhammad Shakeel; Alizadeh, Mahdi; Rahim, Nasrudin Abd

    2018-07-01

    The combined effect of dual sensitization and hetero-junction symmetry has been investigated on the performance of TiO2 based dye sensitized solar cell. CdTe nanoparticles have been introduced in TiO2 matrix to function as sensitizer as well as act as hetero-junction between D719 dye and TiO2 nanoarchitecture. Four concentrations of CdTe i.e. 0.5 wt%, 2 wt%, 5 wt% and 8 wt% have been investigated. Morphological and compositional studies have been conducted using scanning electron microscope (SEM) and X-ray diffraction (XRD) respectively. Light absorption characteristics have been investigated by employing Uv-vis spectroscopy and the overall performance has been studied using solar simulator and electrochemical impedance spectroscopy (EIS). Performance has been found to be increased with the addition of CdTe due to high electron density and reduction in recombination reactions. An increase of 41.73% in incident photo conversion efficiency (IPCE) and 75.57% in short circuit current density (Jsc) have been recorded for the specimens containing 5 wt% CdTe compared to bare TiO2 based DSSCs. Further addition of CdTe leads to reduction in overall performance of DSSCs.

  7. Electron transfer reactions of 1-phenyl-4-vinylpyrazole mediated by cerium(IV) ammonium nitrate

    International Nuclear Information System (INIS)

    Pitarch-Vinuesa, M.; Miranda, M.A.; Medio-Simon, M.; Sepulveda-Arques, J.

    1993-01-01

    The title compound is converted into the cyclic ethers 5 and the alcohol 6 upon treatment with ceric ammonium nitrate in acetone. Using methanol as a solvent the dimethoxy derivative 9 and the nitrate ester 10 are formed. No cross cycloaddition is observed in the presence of olefins such as ethyl vinyl ether, DMAD, or indene; however, with cyclopentadiene as co-reagent a mixture of the exo-endo Diels-Alder adducts 14 involving the vinylic system of 1 as 2π component is obtained. The results are rationalized through the intermediacy of the radical cation 1 .+ , generated by single electron transfer (SET) from the neutral precursor 1 to Ce(IV)

  8. Amplified emission and modified spectral features in an opal hetero-structure mediated by passive defect mode localization

    Science.gov (United States)

    Rout, Dipak; Kumar, Govind; Vijaya, R.

    2018-01-01

    A photonic crystal hetero-structure consisting of a passive planar defect of SiO2 thin film sandwiched between two identical opals grown by inward growing self-assembly method using Rhodamine-B dye-doped polystyrene microspheres is studied for the characteristics of dye emission. The optical properties and the defect mode characteristics of the hetero-structure are studied from the reflection and transmission measurements. Laser-induced fluorescence from the hetero-structure showed amplified and spectrally narrowed emission compared to the photonic crystal emphasizing the role of the defect mode and distributed feedback. The enhanced emission is also complemented by the reduction in fluorescence decay time in the case of the hetero-structure in comparison to the 3D photonic crystals.

  9. Organic Reactions in Aqueous Media (by Chao-Jun Li and Tak-Hang Chan)

    Science.gov (United States)

    Rosan, Reviewed Alan M.

    2000-06-01

    the index. The text does not explicitly include a discussion of what has come to be broadly termed biphasic reaction conditions. Understandably, enzymatic reactions are beyond the scope of the presentation. This book has a decidedly applied character with an understated environmental theme, and the authors succinctly present the extraordinary effects of water on the kinetics, efficiency, and stereoselectivity of a large number of diverse reactions. In addition to their emphasis on the historically significant aqueous Diels-Alder reaction, discovered in 1980, and the literature regarding reactions of various nucleophilic organometals, the authors are to be commended for gathering together a wide and diverse body of information: it is clear that many of the examples shown are gems buried among larger bodies of work. Thus the book does an excellent job of culling and surveying a vast amount of data. There is, however, less emphasis on organizing the mechanistic bases underlying these often dramatic effects. For example, the apparent lack of generality of the effect of water on rate and selectivity in pericyclic reactions calls for some theoretical foundation. The singularly effective use of aqueous TlOH in the Suzuki reaction is cited without comment. On the other hand, the authors' concept of a mechanistic triad that incorporates to various degrees anion, radical, or covalent character in the carbon-carbon bond-forming step between various organometals and carbonyl substrates is appealing and suggests the need for future sophisticated experimental design. The most interesting sections are those dealing with synthesis and industrial applications. Unfortunately the latter is also the shortest chapter. The synthetic examples are timely and well chosen and include water-promoted Heck, Stille, Suzuki, and aldol reactions. There is an extensive, highly informative listing and survey of the use of water-soluble phosphines (both achiral and chiral) and an excellent discussion

  10. Auto e hetero-avaliação no diagnóstico de necessidades de treinamento Self and hetero assessment in training needs diagnostic

    Directory of Open Access Journals (Sweden)

    Mônica Lemes Magalhães

    2001-06-01

    Full Text Available O presente estudo teve como objetivos: desenvolver uma metodologia de avaliação de necessidades de treinamento que incluísse atitudes; estudar a relação entre auto e hetero-avaliação, buscando avaliar conhecimentos, habilidades e atitudes; e avaliar a relação entre a auto-avaliação e algumas variáveis preditoras (tempo de trabalho na organização e na função, emprego anterior, gênero, estado civil, escolaridade e idade. Foram desenvolvidos questionários, de acordo com o método de análise de papel ocupacional. Esses questionários foram aplicados em 898 bancários e seus supervisores imediatos. Os resultados sugeriram que a metodologia parece ser adequada para analisar necessidades de treinamento. Mostraram também que existe relação significativa entre auto e hetero-avaliação de necessidades de treinamento, embora supervisores tendam a apontar maiores necessidades de treinamento, em seus subordinados, do que as auto-avaliações destes mesmos.The objectives of the present study were: to develop a training needs assessment methodology that included attitudes; to study the relationship between self and hetero assessment, by assessing knowledge, skills and attitudes; and to evaluate the relationship between self-assessment and some predicting variables (work experience at the organizational and occupational levels, prior job experience, gender, marital status, schooling and age. Questionnaires were developed, following the method of occupational role analysis. These questionnaires were applied in 898 bank employees and their immediate supervisors. Results have suggested that the methodology seems to be appropriate for analyzing training needs. They have also shown that there is a significant relationship between self and hetero assessments of training needs. However, supervisors tend to point higher training needs, in their subordinates, than the self-assessments made by the latter.

  11. and hetero-dinuclear complexes with a new septadentate Schiff

    Indian Academy of Sciences (India)

    Unknown

    disulphide yields a septadentate Schiff base with N2SO4 donor frame of which ..... bond has been calculated according to the published method 25 and the .... complexes exhibit CuII → CuIII oxidation and CuII → CuI reduction reaction at cyclic.

  12. Mononuclear, trinuclear, and hetero-trinuclear supramolecular complexes containing a new tri-sulfonate ligand and cobalt(II)/copper(II)-(1,10-phenanthroline)2 building blocks

    International Nuclear Information System (INIS)

    Yu Yunfang; Wei Yongqin; Broer, Ria; Sa Rongjian; Wu Kechen

    2008-01-01

    Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen) 2 (H 2 O)(HTST)].2H 2 O (1), [Co 3 (phen) 6 (H 2 O) 2 (TST) 2 ].7H 2 O (2), and [Co 2 Cu(phen) 6 (H 2 O) 2 (TST) 2 ].10H 2 O (3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H 3 TST) with the M 2+ (M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). Complex 1 contains a cis-Co(II)(phen) 2 building block and an HTST as monodentate ligand; complex 2 consists of two TST as bidentate ligands connecting one trans- and two cis-Co(II)(phen) 2 building blocks; complex 3 is formed by replacing the trans-Co(II)(phen) 2 in 2 with a trans-Cu(II)(phen) 2 , which is the first reported hetero-trinuclear supramolecular complex containing both the Co(II)(phen) 2 and Cu(II)(phen) 2 as building blocks. The study shows the flexible multifunctional self-assembly capability of the H 3 TST ligands presenting in these supramolecular complexes through coordinative, H-bonding and even π-π stacking interactions. The photoluminescent optical properties of these complexes are also investigated and discussed as well as the second-order nonlinear optical properties of 1. - Graphical abstract: Novel mononuclear, trinuclear, and hetero-trinuclear supermolecular complexes, [Co(phen) 2 (H 2 O)(HTST)].2H 2 O (1), [Co 3 (phen) 6 (H 2 O) 2 (TST) 2 ].7H 2 O (2), and [Co 2 Cu(phen) 6 (H 2 O) 2 (TST) 2 ].10H 2 O (3), have been synthesized by the reactions of a new tri-sulfonate ligand (2,4,6-tris(4-sulfophenylamino)-1,3,5-triazine, H 3 TST) with the M 2+ (M=Co, Cu) and the second ligand 1,10-phenanthroline (phen). The study shows the flexible multifunctional self-assembly capability of H 3 TST ligand presenting in these supramolecular complexes

  13. High-efficiency super capacitors based on hetero-structured α-MnO{sub 2} nanorods

    Energy Technology Data Exchange (ETDEWEB)

    Ghouri, Zafar Khan [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Shaheer Akhtar, M. [New & Renewable Energy Material Development Center (NewREC), Chonbuk National University, Jeonbuk (Korea, Republic of); Zahoor, Awan [Department of Chemical Engineering, NED University of Engineering & Technology, University Road, Karachi 75270 (Pakistan); Barakat, Nasser A.M., E-mail: nasser@jbnu.ac.kr [Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Department of Chemical Engineering, Faculty of Engineering, El-Minia University, El-Minia (Egypt); Han, Weidong [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Park, Mira [Department of Organic materials and Fiber Engineering, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Pant, Bishweshwar; Saud, Prem Singh; Lee, Cho Hye [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of); Kim, Hak Yong, E-mail: khy@jbnu.ac.kr [Department of BIN Fusion Technology, Chonbuk National University, Jeonju 561-756 (Korea, Republic of)

    2015-09-05

    Highlights: • Hetero-structured α-MnO{sub 2} nanorods are prepared by a facile hydrothermal route. • It is applied as active electrode materials for supercapacitor. • A high specific capacitance of 298 Fg{sup −1} with a superior long term cyclic stability is achieved. • Supercapacitor shows high specific capacitance retention 94% after 1000 cycles. - Abstract: Hetero-structured manganese dioxide nanorods with α phase (α-MnO{sub 2}) were prepared by a facile hydrothermal route at low temperature. X-ray diffraction, scanning electron microscopy, transmission electron microscopy and nitrogen adsorption–desorption measurements were used to characterize the prepared hetero-structured α-MnO{sub 2} nanorods. Supercapacitive performance of the hetero-structured α-MnO{sub 2} nanomaterials as active electrode material was evaluated by cyclic voltammetry (CV) in alkaline medium. The MnO{sub 2} hetero-structure with 2 × 2 tunnels constructed from double chains of octahedral [MnO{sub 6}] structure yield a significantly high specific capacitance of 298 Fg{sup −1} at 5 mV s{sup −1} and demonstrated a superior long term cyclic stability, with specific capacitance retention about 94% after 1000 cycles. The superior supercapacitive performance of the hetero-structured α-MnO{sub 2} electrode is due to its high specific surface area and unique hierarchy architecture which facilitate fast electron and ion transport.

  14. Advanced Optoelectronic Devices based on Si Quantum Dots/Si Nanowires Hetero-structures

    International Nuclear Information System (INIS)

    Xu, J; Zhai, Y Y; Cao, Y Q; Chen, K J

    2017-01-01

    Si quantum dots are currently extensively studied since they can be used to develop many kinds of optoelectronic devices. In this report, we review the fabrication of Si quantum dots (Si QD) /Si nanowires (Si NWs) hetero-structures by deposition of Si QDs/SiO 2 or Si QDs/SiC multilayers on Si NWs arrays. The electroluminescence and photovoltaic devices based on the formed hetero-structures have been prepared and the improved performance is confirmed. It is also found that the surface recombination via the surface defects states on the Si NWs, especially the ones obtained by the long-time etching, may deteriorate the device properties though they exhibit the better anti-reflection characteristics. The possible surface passivation approaches are briefly discussed. (paper)

  15. Auto and hetero-associative memory using a 2-D optical logic gate

    Science.gov (United States)

    Chao, Tien-Hsin (Inventor)

    1992-01-01

    An optical system for auto-associative and hetero-associative recall utilizing Hamming distance as the similarity measure between a binary input image vector V(sup k) and a binary image vector V(sup m) in a first memory array using an optical Exclusive-OR gate for multiplication of each of a plurality of different binary image vectors in memory by the input image vector. After integrating the light of each product V(sup k) x V(sup m), a shortest Hamming distance detection electronics module determines which product has the lowest light intensity and emits a signal that activates a light emitting diode to illuminate a corresponding image vector in a second memory array for display. That corresponding image vector is identical to the memory image vector V(sup m) in the first memory array for auto-associative recall or related to it, such as by name, for hetero-associative recall.

  16. Elemental and Microscopic Analysis of Naturally Occurring C-O-Si Hetero-Fullerene-Like Structures.

    Science.gov (United States)

    Hullavarad, Nilima V; Hullavarad, Shiva S; Fochesatto, Javier

    2015-03-01

    Carbon exhibits an ability to form a wide range of structures in nature. Under favorable conditions, carbon condenses to form hollow, spheroid fullerenes in an inert atmosphere. Using high resolution FESEM, we have concealed the existence of giant hetero-fullerene like structures in the natural form. Clear, distinct features of connected hexagons and pentagons were observed. Energy dispersive X-ray analysis depth-profile of natural fullerene structures indicates that Russian-doll-like configurations composed of C, 0, and Si rings exist in nature. The analysis is based on an outstanding molecular feature found in the size fraction of aerosols having diameters 150 nm to 1.0 µm. The fullerene like structures, which are ~ 150 nm in diameter, are observed in large numbers. To the best of our knowledge, this is the first direct detailed observation of natural fullerene-like structures. This article reports inadvertent observation of naturally occurring hetero-fullerene-like structures in the Arctic.

  17. High toughness alumina/aluminate: The role of hetero-interfaces

    International Nuclear Information System (INIS)

    Brito, M.E.; Yasuoka, M.; Kanzaki, S.

    1996-01-01

    Silica doped alumina/aluminate materials present a combination of high strength and high toughness not achieved before in other alumina systems, except for transformation toughened alumina. The authors have associated the increase in toughness to crack bridging by anisotropically grown alumina grains with concurrent interfacial debonding of these grains. A HREM study of grain boundaries and hetero-interface structures in this material shows the absence of amorphous phases at grain boundaries. Local Auger electron analysis of fractured surfaces revealed the coexistence of Si and La at the grain facets exposed by the noticeable intergranular fracture mode of this material. It is concluded that a certain and important degree of boundaries weakness is related to both presence of Si at the interfaces and existence of alumina/aluminate hetero-interfaces

  18. Synthesis and (spectro)electrochemistry of mixed-valent diferrocenyl-dihydrothiopyran derivatives.

    Science.gov (United States)

    Kowalski, Konrad; Karpowicz, Rafał; Mlostoń, Grzegorz; Miesel, Dominique; Hildebrandt, Alexander; Lang, Heinrich; Czerwieniec, Rafał; Therrien, Bruno

    2015-04-07

    Three novel diferrocenyl complexes were prepared and characterised. 2,2-Diferrocenyl-4,5-dimethyl-3,6-dihydro-2H-thiopyran (1, sulphide) was accessible by the hetero-Diels-Alder reaction of diferrocenyl thioketone with 2,3-dimethyl-1,3-butadiene. Stepwise oxidation of 1 gave the respective oxides 2,2-diferrocenyl-4,5-dimethyl-3,6-dihydro-2H-thiopyran-1-oxide (2, sulfoxide) and 2,2-diferrocenyl-4,5-dimethyl-3,6-dihydro-2H-thiopyran-1,1-dioxide (3, sulfone), respectively. The molecular structures of 1 and 3 in the solid state were determined by single crystal X-ray crystallography. The oxidation of sulphide 1 to sulfone 3, plays only a minor role on the overall structure of the two compounds. Electrochemical (cyclic voltammetry (= CV), square wave voltammetry (= SWV)) and spectroelectrochemical (in situ UV-Vis/NIR spectroscopy) studies were carried out. The CV and SWV measurements showed that an increase of the sulphur atom oxidation from -2 in 1 to +2 in 3 causes an anodic shift of the ferrocenyl-based oxidation potentials of about 100 mV. The electrochemical oxidation of 1-3 generates mixed-valent cations 1(+)-3(+). These monooxidised species display low-energy electronic absorption bands between 1000 and 3000 nm assigned to IVCT (= Inter-Valence Charge Transfer) electronic transitions. Accordingly, the mixed-valent cations 1(+)-3(+) are classified as weakly coupled class II systems according to Robin and Day.

  19. Orgasm is gendered. A feminist exploration into the (hetero) sexual lives of young women

    OpenAIRE

    Mazzoni, Lorenza

    2011-01-01

    Italian society is still facing an enormous ???orgasm gap??? in (hetero) sexual relations: according to a very recent survey (Barbagli and co., 2010) only a minority of women reach an orgasm in every sexual intercourse, in contrast with the vast majority of men; this is true even in the younger generations. I take the lack of orgasm as a starting point for studying how sexual behaviours are still under the reign of patriarchy, imposing male standards that privilege male pleasure at the expens...

  20. HKUST-1 Membranes Anchored on Porous Substrate by Hetero MIL-110 Nanorod Array Seeds.

    Science.gov (United States)

    Mao, Yiyin; Cao, Wei; Li, Junwei; Sun, Luwei; Peng, Xinsheng

    2013-09-02

    Great anchors and seeds: Hetero-seeding growth processes and anchored nanorod arrays were successfully utilized in the synthesis of HKUST-1 membranes. These arrays were firmly anchored on porous substrates by using a MIL-110 nanorod array as both the anchor and seed. The resulting HKUST-1 membranes demonstrated good separation factors for binary gases exceeding the Knudson selectivity. Copyright © 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Dscam1 web server: online prediction of Dscam1 self- and hetero-affinity.

    Science.gov (United States)

    Marini, Simone; Nazzicari, Nelson; Biscarini, Filippo; Wang, Guang-Zhong

    2017-06-15

    Formation of homodimers by identical Dscam1 protein isomers on cell surface is the key factor for the self-avoidance of growing neurites. Dscam1 immense diversity has a critical role in the formation of arthropod neuronal circuit, showing unique evolutionary properties when compared to other cell surface proteins. Experimental measures are available for 89 self-binding and 1722 hetero-binding protein samples, out of more than 19 thousands (self-binding) and 350 millions (hetero-binding) possible isomer combinations. We developed Dscam1 Web Server to quickly predict Dscam1 self- and hetero- binding affinity for batches of Dscam1 isomers. The server can help the study of Dscam1 affinity and help researchers navigate through the tens of millions of possible isomer combinations to isolate the strong-binding ones. Dscam1 Web Server is freely available at: http://bioinformatics.tecnoparco.org/Dscam1-webserver . Web server code is available at https://gitlab.com/ne1s0n/Dscam1-binding . simone.marini@unipv.it or guangzhong.wang@picb.ac.cn. Supplementary data are available at Bioinformatics online. © The Author 2017. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com

  2. A flexible tactile sensitive sheet using a hetero-core fiber optic sensor

    Science.gov (United States)

    Fujino, S.; Yamazaki, H.; Hosoki, A.; Watanabe, K.

    2014-05-01

    In this report, we have designed a tactile sensitive sheet based on a hetero-core fiber-optic sensor, which realize an areal sensing by using single sensor potion in one optical fiber line. Recently, flexible and wide-area tactile sensing technology is expected to applied to acquired biological information in living space and robot achieve long-term care services such as welfare and nursing-care and humanoid technology. A hetero-core fiber-optic sensor has several advantages such as thin and flexible transmission line, immunity to EMI. Additionally this sensor is sensitive to moderate bending actions with optical loss changes and is independent of temperature fluctuation. Thus, the hetero-core fiber-optic sensor can be suitable for areal tactile sensing. We measure pressure characteristic of the proposed sensitive sheet by changing the pressure position and pinching characteristic on the surface. The proposed tactile sensitive sheet shows monotonic responses on the whole sensitive sheet surface although different sensitivity by the position is observed at the sensitive sheet surface. Moreover, the tactile sensitive sheet could sufficiently detect the pinching motion. In addition, in order to realize the discrimination between pressure and pinch, we fabricated a doubled-over sensor using a set of tactile sensitive sheets, which has different kinds of silicon robbers as a sensitive sheet surface. In conclusion, the flexible material could be given to the tactile sensation which is attached under proposed sensitive sheet.

  3. The step-wise pathway of septin hetero-octamer assembly in budding yeast.

    Science.gov (United States)

    Weems, Andrew; McMurray, Michael

    2017-05-25

    Septin proteins bind guanine nucleotides and form rod-shaped hetero-oligomers. Cells choose from a variety of available septins to assemble distinct hetero-oligomers, but the underlying mechanism was unknown. Using a new in vivo assay, we find that a stepwise assembly pathway produces the two species of budding yeast septin hetero-octamers: Cdc11/Shs1-Cdc12-Cdc3-Cdc10-Cdc10-Cdc3-Cdc12-Cdc11/Shs1. Rapid GTP hydrolysis by monomeric Cdc10 drives assembly of the core Cdc10 homodimer. The extended Cdc3 N terminus autoinhibits Cdc3 association with Cdc10 homodimers until prior Cdc3-Cdc12 interaction. Slow hydrolysis by monomeric Cdc12 and specific affinity of Cdc11 for transient Cdc12•GTP drive assembly of distinct trimers, Cdc11-Cdc12-Cdc3 or Shs1-Cdc12-Cdc3. Decreasing the cytosolic GTP:GDP ratio increases the incorporation of Shs1 vs Cdc11, which alters the curvature of filamentous septin rings. Our findings explain how GTP hydrolysis controls septin assembly, and uncover mechanisms by which cells construct defined septin complexes.

  4. HeteroGenius: A Framework for Hybrid Analysis of Heterogeneous Software Specifications

    Directory of Open Access Journals (Sweden)

    Manuel Giménez

    2014-01-01

    Full Text Available Nowadays, software artifacts are ubiquitous in our lives being an essential part of home appliances, cars, cell phones, and even in more critical activities like aeronautics and health sciences. In this context software failures may produce enormous losses, either economical or, in the worst case, in human lives. Software analysis is an area in software engineering concerned with the application of diverse techniques in order to prove the absence of errors in software pieces. In many cases different analysis techniques are applied by following specific methodological combinations that ensure better results. These interactions between tools are usually carried out at the user level and it is not supported by the tools. In this work we present HeteroGenius, a framework conceived to develop tools that allow users to perform hybrid analysis of heterogeneous software specifications. HeteroGenius was designed prioritising the possibility of adding new specification languages and analysis tools and enabling a synergic relation of the techniques under a graphical interface satisfying several well-known usability enhancement criteria. As a case-study we implemented the functionality of Dynamite on top of HeteroGenius.

  5. Hydrogen doping of Indium Tin Oxide due to thermal treatment of hetero-junction solar cells

    Energy Technology Data Exchange (ETDEWEB)

    Ritzau, Kurt-Ulrich, E-mail: kurt-ulrich.ritzau@ise.fraunhofer.de [Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstrasse 2, 79110 Freiburg (Germany); Behrendt, Torge [Infineon Technologies, Max-Planck-Straße 5, 59581 Warstein (Germany); Palaferri, Daniele [Laboratoire Matériaux et Phénomènes Quantiques, Université Paris Diderot, Sorbonne Paris Cité, CNRS—UMR 7162, 75013 Paris (France); Bivour, Martin; Hermle, Martin [Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstrasse 2, 79110 Freiburg (Germany)

    2016-01-29

    Indium Tin Oxide (ITO) layers in silicon hetero junction solar cells change their electrical and optical properties when exposed to temperature treatments. Hydrogen which effuses from underlying amorphous silicon layers is identified to dope the ITO layer. This leads to an additional increase in conductivity. In this way an almost isolating ITO can become degenerately doped through temperature treatments. The resulting carrier density in the range of 10{sup 20} cm{sup −3} leads to a substantial increase in free carrier absorption, which in turn leads to an increased parasitic absorption in the cell device. Thus hydrogen effusion in silicon hetero-junction (SHJ) solar cells does not only affect the degradation of amorphous silicon (a-Si:H) passivation of crystalline silicon (c-Si), but also the electrical and optical properties of both front and back ITO layers. This leads to the further design rule for SHJ solar cells, meaning that ITO properties have to be optimized in the state after modification during temperature treatment. - Highlights: • ITO is additionally doped by heat treatment of silicon hetero-junction solar cells. • The discovered effect turns an almost isolating ITO into a degenerately doped TCO. • TCO properties have to be considered as measured in the final cell.

  6. DOE Energy Frontiers Research Center for Heterogeneous Functional Materials; the “HeteroFoaM Center”

    Energy Technology Data Exchange (ETDEWEB)

    Reifsnider, Kenneth Leonard [Univ. of South Carolina, Columbia, SC (United States)

    2016-11-03

    Synopsis of five year accomplishments: Devices that convert and store energy are generally made from heterogeneous constituent materials that act and interact to selectively conduct, transport, and separate mass, heat, and charge. Controlling these actions and interactions enables the technical breakthroughs that have made fuel cells, batteries, and solid state membranes, for example, essential parts of our society. In the biological sense, these materials are ‘vascular’ rather than primitive ‘cellular’ materials, in which the arrangements and configurations of the constituents (including their void phases) play essential and definitive roles in their functional capabilities. In 2009 a group of investigators, with lifetime investments of effort in the understanding of heterogeneous materials, recognized that the design of such material systems is not an optimization problem as such. Local interactions of the constituents create “emergent” properties and responses that are not part of the formal set of constituent characteristics, in much the same sense that society and culture is created by the group interactions of the people involved. The design of emergent properties is an open question in all formal science, but for energy materials the lack of this foundation science relegates development tasks to Edisonian trial and error, with anecdotal success and frequent costly failures. That group defined, for the first time, multi-scale heterogeneous functional materials with functional disordered and void phase regions as “HeteroFoaM,” and formed the first multidisciplinary research team to define and codify the foundation science of that material class. The primary goal of the HeteroFoaM Center was, and is, to create and establish the multi-scale fundamental knowledge and related methodology required for the rational and systematic multiphysics design of heterogeneous functional materials and their interfaces and surfaces for applications in energy

  7. Visible light CrO{sub 4}{sup 2-} reduction using the new CuAlO{sub 2}/CdS hetero-system

    Energy Technology Data Exchange (ETDEWEB)

    Brahimi, R. [Centre of Research in Physical and Chemical Analysis (CRAPC), BP 248, RP 16004 Algiers (Algeria); Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB), BP 32 16111 Algiers (Algeria); Bessekhouad, Y. [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB), BP 32 16111 Algiers (Algeria); National Veterinary High School, BP 16111 Algiers (Algeria); Nasrallah, N. [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB), BP 32 16111 Algiers (Algeria); Trari, M., E-mail: solarchemistry@gmail.com [Laboratory of Storage and Valorization of Renewable Energies, Faculty of Chemistry (USTHB), BP 32 16111 Algiers (Algeria)

    2012-06-15

    Graphical abstract: Pseudo-first order kinetic for CrO{sub 4}{sup 2-} photoreduction for various concentrations. Highlights: Black-Right-Pointing-Pointer The work deals with the chromium reduction over CuAlO{sub 2}/CdS hetero-system. Black-Right-Pointing-Pointer The conduction band of CdS (-1.08 V) is more negative than the CrO{sub 4}{sup 2-}/Cr{sup 3+} level. Black-Right-Pointing-Pointer The sensitizer CuAlO{sub 2} has been synthesized by sol-gel. Black-Right-Pointing-Pointer The Cr(VI) reduction follows a pseudo first order kinetic with of salicylic acid. - Abstract: In this study, 64% of hexavalent chromium Cr(VI) reduction from the initial concentration (10{sup -4} M) is reported under visible light using the (CuAlO{sub 2}/CdS) hetero-system. In this new hetero-system, low doped CuAlO{sub 2} delafossite, synthesized by sol-gel works as an electrons reservoir with a wide space charge region (440 nm). In this case, the electron transfer to chromate is mediated via the hexagonal CdS variety, whose conduction band level is at -1.08 V with respect to the saturated calomel electrode which is more negative than the CrO{sub 4}{sup 2-}/Cr{sup 3+} level. This high reduction rate is achieved under optimized pH and CuAlO{sub 2} percentage. Moreover, salicylic acid gives the best performance among hole scavengers and CuAlO{sub 2} approaches 100% photostability at pH 7.5. The photo-catalytic process follows a pseudo first order kinetic with a half life of 2 h. The reaction products are identified by UV-visible spectrophotometry and linear voltametry at a platinum rotating electrode. The results reveal the presence of Cr{sup 3+} after irradiation.

  8. Reações orgânicas em meio aquoso

    Directory of Open Access Journals (Sweden)

    Silva Flavia Martins da

    2001-01-01

    Full Text Available The use of water as solvent in organic reactions has been uncommon for several reasons, among them the low solubility of the reactants, the incompatibility of the intermediates with water, and the competition between the desired reaction and hydrolysis. Breslow in 1980, demonstrated that the hydrophobic effect accelerates Diels-Alder reactions and gives a high endo/exo selectivity. Since then, many other reactions were studied in this medium, and below we show the principal results. Besides the academic interest, human and economic aspects are included in this study. Water as a solvent minimizes environmental impact, costs and increases operational safety.

  9. Theoretical Study of the Diastereofacial Isomers of Aldrin and Dieldrin

    Directory of Open Access Journals (Sweden)

    Zoran Zdravkovski

    2006-02-01

    Full Text Available The Diels-Alder reaction of hexachlorocyclopentadiene with norbornadiene givesaldrin but theoretically three other diastereofacial isomers are possible. On oxidation theseisomers can generate eight adducts one of which is known as dieldrin. All these, as well asthe corresponding reactions with hexafluorocyclopenadiene were studied by semiempirical(AM1 and PM3 and hybrid density functional (B3LYP methods. Besides the energy levels,the transition states were calculated for the reactions leading to the diastereofacial isomers ofaldrin, which indicate that aldrin is the favored product of the reaction both fromthermodynamic and kinetic point of view.

  10. Neighboring Hetero-Atom Assistance of Sacrificial Amines to Hydrogen Evolution Using Pt-Loaded TiO2-Photocatalyst

    Directory of Open Access Journals (Sweden)

    Masahide Yasuda

    2014-05-01

    Full Text Available Photocatalytic H2 evolution was examined using Pt-loaded TiO2-photocatalyst in the presence of amines as sacrificial agents. In the case of amines with all of the carbon attached to the hetero-atom such as 2-aminoethanol, 1,2-diamonoethane, 2-amino-1,3-propanediol, and 3-amino-1,2-propanediol, they were completely decomposed into CO2 and water to quantitatively evolve H2. On the other hand, the amines with both hetero-atoms and one methyl group at the β-positions (neighboring carbons of amino group such as 2-amino-1-propanol and 1,2-diaminopropane were partially decomposed. Also, the photocatalytic H2 evolution using amines without the hetero-atoms at the β-positions such as ethylamine, propylamine, 1-butylamine, 1,3-diaminopropane, 2-propylamine, and 2-butylamine was inefficient. Thus, it was found that the neighboring hetero-atom strongly assisted the degradation of sacrificial amines. Moreover, rate constants for H2 evolution were compared among amines. In conclusion, the neighboring hetero-atom did not affect the rate constants but enhanced the yield of hydrogen evolution.

  11. Uranium hetero-bimetallic complexes: synthesis, structure and magnetic properties

    International Nuclear Information System (INIS)

    Le Borgne, Th.

    2000-01-01

    The aim of this thesis is to synthesize molecular complexes with uranium and transition metal ions in close proximity, to determine the nature of the magnetic interaction between them. We decided to use Schiff bases as assembling ligands, which are unusual for uranium (IV). Although the simplest Schiff bases, such as H 2 Salen, lead to ligand exchange reactions, the bi-compartmental Schiff base H 4 L 6 (bis(3-hydroxy-salicylidene) - 2,2-dimethyl-propylene) allows the crystal structure determination of the complex [L 6 Cu(pyr)]U[L 6 Cu].2pyr, obtained by reaction of the metallo-ligand H 2 L 6 Cu with U(acac) 4 . In this manner, the complexes [L 6 Co(pyr)] 2 U and [L 6 Ni(pyr)] 2 U.pyr were also isolated, as well as the compounds in which the paramagnetic ions have been exchanged by the diamagnetic ions Zn II , Zr IV and Th IV ': [L 6 Zn(pyr)] 2 U, [L 6 Cu] 2 Zr and [L 6 Cu(pyr)]Th[L 6 Cu].2pyr. These complexes are the first which involve three metallic centres assembling by the means of a hexa-dentate Schiff base. The crystalline structures show, for all these complexes, the outstanding orthogonal arrangement of the two fragments L 6 M around the central atom which is in a dodecahedral environment of eight oxygen atoms of two Schiff bases. The syntheses of the isostructural complexes Cu2 II and Zn 2 U in which the uranium (IV) ion is close, in the first one, to the paramagnetic ion Cu II and, in the second one, to the diamagnetic ion Zn II , has allowed the use of the empiric method to determine the nature of the magnetic interaction between an f element and a transition metal. The comparison of the magnetic behaviour of two complexes Cu 2 U and Zn 2 U, expressed by the variation of χT vs T, reveals the ferromagnetic interaction in the heart of the triad Cu-U-Cu. The magnetic behaviour of the complexes Cu 2 Th et Cu 2 Zr which does not show any coupling between the two copper (II) ions and the weak antiferromagnetic interaction in the Ni 2 U compound, favour the

  12. Phosphine-catalyzed cycloadditions of allenic ketones: new substrates for nucleophilic catalysis.

    Science.gov (United States)

    Wallace, Debra J; Sidda, Rachel L; Reamer, Robert A

    2007-02-02

    A range of phosphine-catalyzed cycloaddition reactions of allenic ketones have been studied, extending the scope of these processes from the more widely used 2,3-butadienoates to allow access to a number of synthetically useful products. Reaction of allenyl methyl ketone 4 with exo-enones afforded spirocyclic compounds in good regioselectivity and promising enantioselectivity via a [2 + 3] cycloaddtion. Aromatic allenyl ketones undergo a phosphine-promoted dimerization to afford functionalized pyrans, leading to a formal [2 + 4] Diels-Alder product, but did not react in the [2 + 3] cycloaddition. The results from other reactions that had found utility with 2,3-butadienoates are also reported.

  13. Synthesis of Racemic β-Chamigrene, a Spiro[5.5]undecane Sequiterpene

    Directory of Open Access Journals (Sweden)

    Simen Antonsen

    2014-12-01

    Full Text Available The present paper describes a total synthesis of racemic β-chamigrene (1, a sesquiterpene with a spiro[5.5]undecane carbon framework. Compared with previously reported β-chamigrene syntheses, we were able to reduce the total number of reaction steps, which also resulted in a significant improvement of the overall yield. The commercially available ketone 6-methylhept-5-en-2-one was transformed by known simple procedures into 3,3-dimethyl-2-methylenecyclohexanone. This reacted with isoprene by a Diels-Alder reaction to give a spiro ketone. An olefination reaction on this compound gave the target molecule.

  14. Synthesis of 2-phenylnaphthalenes from styryl-2-methoxybenzenes.

    Science.gov (United States)

    Mudududdla, Ramesh; Sharma, Rohit; Abbat, Sheenu; Bharatam, Prasad V; Vishwakarma, Ram A; Bharate, Sandip B

    2014-10-18

    A new simple and efficient method for the synthesis of 2-phenylnaphthalenes from electron-rich 1-styryl-2-methoxybenzenes has been described. The reaction proceeds via TFA catalyzed C-C bond cleavage followed by intermolecular [4+2]-Diels-Alder cycloaddition of an in situ formed styrenyl trifluoroacetate intermediate. The quantum chemical calculations identified the transition state for the cycloaddition reaction and helped in tracing the reaction mechanism. The method has been efficiently utilized for synthesis of the phenanthrene skeleton and a naphthalene-based potent and selective ER-β agonist.

  15. A potential role of substrate as a base for deprotonation pathway in Rh-catalysed C-H amination of heteroArenes: DFT insights

    KAUST Repository

    Ajitha, Manjaly John

    2016-03-29

    The possibility of direct introduction of a new functionality through C–H bond activation is an attractive strategy in covalent synthesis. Here, we investigated the mechanism of Rh-catalysed C-H amination of the hetero-aryl substrate (2-phenylpyridine) using phenyl azide as nitrogen source by density functional theory (DFT). For the deprotocyclometallation and protodecyclometallation processes of the title reaction, we propose a stepwise base-assisted mechanism (pathway I) instead of previously reported concerted mechanism (pathway II). In the new mechanism proposed here, 2-phenylpyridine acts as a base in the initial deprotonation step (C-H bond cleavage) and transports the proton towards the final protonation step. In fact, the N-H bond of the strong conjugate acid (formed during initial C-H bond cleavage) considered in pathway I (via TS4) is more acidic than the C-H bond of the neutral substrate considered in pathway II (via TS5). The higher activation barrier of TS5 mainly originates from the ring strain of the four membered cyclic transition state. The vital role of base, as disclosed here, can potentially have broader mechanistic implications for the development of reaction conditions of transition metal catalysed reactions.

  16. Injustice to transsexual women in a hetero-normative healthcare system.

    Science.gov (United States)

    Newman-Valentine, Douglas; Duma, Sinegugu

    2014-11-21

    Transsexual women who are on the journey of sexual re-alignment will experience various health problems. These problems are related directly to the treatment regime that they are following in order to attain and maintain their physical embodiment as a woman. They are forced to negotiate a hetero-normative healthcare system in order to receive assistance and care for their health problems related to their sexual re-alignment process. The questions posed were: What are the unique health problems that transsexual women experience whilst on the journey of sexual re-alignment? What is the current context of the South African healthcare system in which transsexual women should negotiate healthcare? These questions were asked in order to explore the health problems with which transsexual women are faced and to describe the hetero-normative healthcare system in South Africa. An electronic literature search was executed via the EBSCO host with specific inclusion and exclusion criteria. The search words that were used were: Transsexual/s and Health/Healthcare. All studies had to be peer reviewed and published in the English language, from January 1972 up until February 2013. Literature on transsexual children was excluded. Transsexual women have the potential to suffer significant side-effects from their sexual re-alignment treatment, including cardio-vascular problems, endocrine problems and mental ill-health. They are also vulnerable to HIV infection. They have poor access to quality holistic healthcare and this may lead an increase in the mortality and morbidity figures of women. A hetero-normative healthcare system has a negative impact on the health of transsexual women and will cause them to be marginalised. This could contribute to both homo- and trans-phobia that will in turn strengthen the belief that transsexual women are un-African.

  17. Experimental evidence for the involvement of PDLIM5 in mood disorders in hetero knockout mice.

    Directory of Open Access Journals (Sweden)

    Yasue Horiuchi

    Full Text Available BACKGROUND: Reports indicate that PDLIM5 is involved in mood disorders. The PDLIM5 (PDZ and LIM domain 5 gene has been genetically associated with mood disorders; it's expression is upregulated in the postmortem brains of patients with bipolar disorder and downregulated in the peripheral lymphocytes of patients with major depression. Acute and chronic methamphetamine (METH administration may model mania and the evolution of mania into psychotic mania or schizophrenia-like behavioral changes, respectively. METHODS: To address whether the downregulation of PDLIM5 protects against manic symptoms and cause susceptibility to depressive symptoms, we evaluated the effects of reduced Pdlim5 levels on acute and chronic METH-induced locomotor hyperactivity, prepulse inhibition, and forced swimming by using Pdlim5 hetero knockout (KO mice. RESULTS: The homozygous KO of Pdlim5 is embryonic lethal. The effects of METH administration on locomotor hyperactivity and the impairment of prepulse inhibition were lower in Pdlim5 hetero KO mice than in wild-type mice. The transient inhibition of PDLIM5 (achieved by blocking the translocation of protein kinase C epsilon before the METH challenge had a similar effect on behavior. Pdlim5 hetero KO mice showed increased immobility time in the forced swimming test, which was diminished after the chronic administration of imipramine. Chronic METH treatment increased, whereas chronic haloperidol treatment decreased, Pdlim5 mRNA levels in the prefrontal cortex. Imipramine increased Pdlim5 mRNA levels in the hippocampus. CONCLUSION: These findings are partially compatible with reported observations in humans, indicating that PDLIM5 is involved in psychiatric disorders, including mood disorders.

  18. Interactions between polystyrene microplastics and marine phytoplankton lead to species-specific hetero-aggregation.

    Science.gov (United States)

    Long, Marc; Paul-Pont, Ika; Hégaret, Hélène; Moriceau, Brivaela; Lambert, Christophe; Huvet, Arnaud; Soudant, Philippe

    2017-09-01

    To understand the fate and impacts of microplastics (MP) in the marine ecosystems, it is essential to investigate their interactions with phytoplankton as these may affect MP bioavailability to marine organisms as well as their fate in the water column. However, the behaviour of MP with marine phytoplanktonic cells remains little studied and thus unpredictable. The present study assessed the potential for phytoplankton cells to form hetero-aggregates with small micro-polystyrene (micro-PS) particles depending on microalgal species and physiological status. A prymnesiophycea, Tisochrysis lutea, a dinoflagellate, Heterocapsa triquetra, and a diatom, Chaetoceros neogracile, were exposed to micro-PS (2 μm diameter; 3.96 μg L -1 ) during their growth culture cycles. Micro-PS were quantified using an innovative flow-cytometry approach, which allowed the monitoring of the micro-PS repartition in microalgal cultures and the distinction between free suspended micro-PS and hetero-aggregates of micro-PS and microalgae. Hetero-aggregation was observed for C. neogracile during the stationary growth phase. The highest levels of micro-PS were "lost" from solution, sticking to flasks, with T. lutea and H. triquetra cultures. This loss of micro-PS sticking to the flask walls increased with the age of the culture for both species. No effects of micro-PS were observed on microalgal physiology in terms of growth and chlorophyll fluorescence. Overall, these results highlight the potential for single phytoplankton cells and residual organic matter to interact with microplastics, and thus potentially influence their distribution and bioavailability in experimental systems and the water column. Copyright © 2017 Elsevier Ltd. All rights reserved.

  19. Surface Reconstruction for Preparation of Plasmonic Au/TiO₂ Nanoparticle with Perfect Hetero Interface and Improved Photocatalytic Capacity.

    Science.gov (United States)

    Yuan, Guoqiu; Ping, Chen; Zhao, Qin; Cao, Min; Jin, Yonglong; Ge, Cunwang

    2018-07-01

    The photocatalytic activity of plasmonic Au/TiO2 nanoparticles (NPs) is dependent on distances between Au and TiO2. The preparation of plasmonic NPs is still a challenge because of an inherent lattice mismatch on heterogeneous interfaces. The combination between Au and TiO2 NPs often exhibits physical adsorption, which affect block the electron transferring process by photo-induction from TiO2 to Au NPs and weaken the photocatalytic activity. In this work an approach for preparing plasmonic Au/TiO2 NPs with perfect hetero-interface was proposed based on reconstruction of anatase TiO2 with (101) surface and in-situ reduction of Au NPs. Under UV-irradiation, anatase TiO2 NPs with a high percentage of (001) facets in formaldehyde solution undergo photochemical reactions to reconstruct the (101) surface of TiO2 and simultaneously allow polyformaldehyde to absorb on the same surface. Thus, Au(OH)-4 ions could be adsorbed on the (101) surfaces of TiO2 through electrostatic adsorption and reduced to form nano-Au in situ after recrystallization at 180 °C. The high-resolution transmission electron microscopy (HRTEM) images showed clear nanoscale lattice transition on heterogeneous interfaces of Au/TiO2 NPs. The surface structure of TiO2 NPs and the growth mechanism of Au/TiO2 NPs were evaluated with HRTEM, X-ray photoelectron spectra (XPS) and Fourier transform infrared spectroscopy (FTIR). It was demonstrated that the as-prepared plasmonic Au/TiO2 NPs had higher photocatalytic activity and corrosion resistance in comparison with primary TiO2 NPs by photo-electrochemical measurements. The reinforcing mechanism could be interpreted with Mott-Schottky analysis in terms of quantum mechanics. Our study implied that the reconstruction based synthesis may open up more opportunities to obtain lattice-mismatch nanomaterials for photocatalysis.

  20. Red light emission from ZnO:Eu"3"+|CuSCN hetero-junction under cathodic polarization

    International Nuclear Information System (INIS)

    Sirimanne, P.M.; Minoura, H.

    2015-01-01

    Eu"3"+ ions were bonded to ZnO ceramic via organic ligand. Surface bonded Eu"3"+ ions were exhibited specific luminescence bands due to electron transitions between f–f intra-configurationally transitions. Further enhancement of luminescence bands was observed by attaching selected oligomers to Eu"3"+ ions. A hetero-junction was prepared by depositing copper-thiocyanate on Eu"3"+ ions bonded ZnO ceramic. Red light emission was observed from surface bonded Eu"3"+ ions in ZnO:Eu"3"+|CuSCN hetero-junction under reverse bias. - Highlights: • Europium doped ZnO ceramic exhibits photo-luminescence. • Semiconductor hetro-junction was prepared. • ZnO:Eu"3"+|CuSCN hetero-junction emits red light under reverse bias.