WorldWideScience

Sample records for alkenes

  1. Asymmetric fluorocyclizations of alkenes.

    Science.gov (United States)

    Wolstenhulme, Jamie R; Gouverneur, Véronique

    2014-12-16

    CONSPECTUS: The vicinal fluorofunctionalization of alkenes is an attractive transformation that converts feedstock olefins into valuable cyclic fluorinated molecules for application in the pharmaceutical, agrochemical, medical, and material sectors. The challenges associated with asymmetric fluorocyclizations induced by F(+) reagents are distinct from other types of halocyclizations. Processes initiated by the addition of an F(+) reagent onto an alkene do not involve the reversible formation of bridged fluoronium ions but generate acyclic β-fluorocationic intermediates. This mechanistic feature implies that fluorocyclizations are not stereospecific. A discontinuity exists between the importance of this class of fluorocyclization and the activation modes currently available to implement successful catalysis. Progress toward fluorocyclization has been achieved by investing in neutral and cationic [NF] reagent development. The body of work on asymmetric fluorination using chiral cationic [NF](+) reagents prepared by fluorine transfer from the dicationic [NF](2+) reagent Selectfluor to quinuclidines, inspired the development of asymmetric F(+)-induced fluorocyclizations catalyzed by cinchona alkaloids; for catalysis, the use of N-fluorobenzenesulfonimide, which is less reactive than Selectfluor, ensures that the achiral F(+) source remains unreactive toward the alkene. These organocatalyzed enantioselective fluorocyclizations can be applied to indoles to install the fluorine on a quaternary benzylic stereogenic carbon center and to afford fluorinated analogues of natural products featuring the hexahydropyrrolo[2,3-b]indole or the tetrahydro-2H-furo[2,3-b]indole skeleton. In an alternative approach, the poor solubility of dicationic Selectfluor bis(tetrafluoroborate) in nonpolar solvent was exploited with anionic phase transfer catalysis as the operating activation mode. Exchange of the tetrafluoroborate ions of Selectfluor with bulky lipophilic chiral anions (e

  2. Chromium Salen Mediated Alkene Epoxidation

    DEFF Research Database (Denmark)

    Petersen, Kaare Brandt; Norrby, Per-Ola; Daly, Adrian M.

    2002-01-01

    The mechanism of alkene epoxidation by chromium(v) oxo salen complexes has been studied by DFT and experimental methods. The reaction is compared to the closely related Mn-catalyzed process in an attempt to understand the dramatic difference in selectivity between the two systems. Overall......, the studies show that the reactions have many similarities, but also a few critical differences. In agreement with experiment, the chromium system requires a change from low- to high-spin in the catalytic cycle, whereas the manganese system can proceed either with spin inversion or entirely on the high......-spin surface. The low-spin addition of metal oxo species to an alkene leads to an intermediate which forms epoxide either with a barrier on the low-spin surface or without a barrier after spin inversion. Supporting evidence for this intermediate was obtained by using vinylcyclopropane traps. The chromium...

  3. Synthesis of tetrasubstituted alkenes via metathesis.

    Science.gov (United States)

    Paek, Seung-Mann

    2012-03-15

    Fully substituted olefin generation via metathesis is presented. Catalyst development, optimization of reaction conditions and substrate screening are included. In addition, asymmetric alkene metathesis, the cross metathesis reaction for this transformation and its application in natural products will be discussed.

  4. Facile Pd(II)- and Ni(II)-Catalyzed Isomerization of Terminal Alkenes into 2-Alkenes

    Science.gov (United States)

    Lim, Hwan Jung; Smith, Craig R.; RajanBabu, T. V.

    2009-01-01

    Mono- and 2,2′-di-substituted terminal alkenes can be isomerized into the more stable internal Z- and E- alkenes by treating them with catalytic amounts of [(allyl)PdCl]2 or [(allyl)NiBr]2, a triarylphosphine and silver triflate at room temperature. The isomeric ratio (E:Z) depends on the alkenes, the (E)-isomer being the major one. The reaction is tolerant to a wide variety of functional groups including other reactive olefins. Unlike the more reactive Ir catalysts, monosubstituted alkenes give almost exclusively the 2-alkenes. Direct comparison to two of the best-known catalysts for this process, (Ir(PCy3)3]+ [BPh4]−, and Grubbs Generation II metathesis catalyst) is also reported. PMID:19441793

  5. Asymmetric synthesis of bi(thio)xanthylidene overcrowded alkenes

    NARCIS (Netherlands)

    Geertsema, Edzard M.; Hoen, Rob; Meetsma, Auke; Feringa, Ben L.

    2006-01-01

    Overcrowded alkenes are a fascinating class of inherent dissymmetric molecules that attract considerable interest for instance as chiroptical molecular switches and unidirectionally rotary motors. A practical synthesis route towards enantiomerically pure overcrowded alkenes is an important goal. We

  6. Heterogeneous Catalysis: The Horiuti-Polanyi Mechanism and Alkene Hydrogenation

    Science.gov (United States)

    Mattson, Bruce; Foster, Wendy; Greimann, Jaclyn; Hoette, Trisha; Le, Nhu; Mirich, Anne; Wankum, Shanna; Cabri, Ann; Reichenbacher, Claire; Schwanke, Erika

    2013-01-01

    The hydrogenation of alkenes by heterogeneous catalysts has been studied for 80 years. The foundational mechanism was proposed by Horiuti and Polanyi in 1934 and consists of three steps: (i) alkene adsorption on the surface of the hydrogenated metal catalyst, (ii) hydrogen migration to the beta-carbon of the alkene with formation of a delta-bond…

  7. Syngas conversion to a light alkene and related methods

    Energy Technology Data Exchange (ETDEWEB)

    Ginosar, Daniel M.; Petkovic, Lucia M.

    2017-11-14

    Methods of producing a light alkene. The method comprises contacting syngas and tungstated zirconia to produce a product stream comprising at least one light alkene. The product stream is recovered. Methods of converting syngas to a light alkene are also disclosed. The method comprises heating a precursor of tungstated zirconia to a temperature of between about 350.degree. C. and about 550.degree. C. to form tungstated zirconia. Syngas is flowed over the tungstated zirconia to produce a product stream comprising at least one light alkene and the product stream comprising the at least one light alkene is recovered.

  8. Synthesis of Tetrasubstituted Alkenes via Metathesis

    Directory of Open Access Journals (Sweden)

    Seung-Mann Paek

    2012-03-01

    Full Text Available Fully substituted olefin generation via metathesis is presented. Catalyst development, optimization of reaction conditions and substrate screening are included. In addition, asymmetric alkene metathesis, the cross metathesis reaction for this transformation and its application in natural products will be discussed.

  9. Oxidation of gaseous hydrocarbons by alkene-utilizing bacteria

    NARCIS (Netherlands)

    Ginkel, van C.G.

    1987-01-01

    Gaseous alkenes are widespread in the environment due to the emission of these hydrocarbons by industry and due to their production from natural sources as for instance ethene by plants, fungi and bacteria. Micro-organisms have developed the potential to oxidize these hydrocarbons. Alkenes

  10. Green oxidation of alkenes in ionic liquid solvent by hydrogen

    Indian Academy of Sciences (India)

    Additionally, ion liquid solvent efficiently improved all the catalytic performances. Finally, the reaction was extended to different alkenes using the heterogeneous complex 2-L4. Among all the alkenes, those containing -electron-withdrawing groups and trans-orientations exhibited lower tendency for oxidation.

  11. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann [Agoura Hills, CA

    2011-11-29

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  12. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann

    2016-02-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  13. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann

    2015-09-22

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  14. Synthesis of terminal alkenes from internal alkenes and ethylene via olefin metathesis

    Energy Technology Data Exchange (ETDEWEB)

    Schrodi, Yann

    2013-07-09

    This invention relates generally to olefin metathesis, and more particularly relates to the synthesis of terminal alkenes from internal alkenes using a cross-metathesis reaction catalyzed by a selected olefin metathesis catalyst. In one embodiment of the invention, for example, a method is provided for synthesizing a terminal olefin, the method comprising contacting an olefinic substrate comprised of at least one internal olefin with ethylene, in the presence of a metathesis catalyst, wherein the catalyst is present in an amount that is less than about 1000 ppm relative to the olefinic substrate, and wherein the metathesis catalyst has the structure of formula (II) ##STR00001## wherein the various substituents are as defined herein. The invention has utility, for example, in the fields of catalysis, organic synthesis, and industrial chemistry.

  15. Fe(III)-Catalyzed Hydroallylation of Unactivated Alkenes with Morita-Baylis-Hillman Adducts.

    Science.gov (United States)

    Qi, Jifeng; Zheng, Jing; Cui, Sunliang

    2018-03-02

    An Fe(III)-catalyzed hydroallylation of unactivated alkenes with Morita-Baylis-Hillman adducts via an Fe-catalyzed process is described. A variety of alkenes, including mono-, di-, and trisubstituted alkenes, could all smoothly convert to structural diversified cinnamates in this protocol. Interestingly, when the hydroxyl-containing alkenes were used, various lactones could be rapidly assembled. Moreover, this protocol could be applied to late-stage functionalization of natural products.

  16. Uncatalyzed thermal gas phase aziridination of alkenes by organic ...

    Indian Academy of Sciences (India)

    Alkene aziridination by azides through uncatalyzed thermal gas phase routes has been studiedusing the DFT B3LYP/6-31G(d,p) method, where the possible role of discrete nitrene intermediates is emphasized.The thermal decomposition of azides is studied using the MP2/aug-cc-pVDZ strategy as well. The MP2(but not the ...

  17. Highly efficient epoxidation of alkenes with m-chloroperbenzoic acid ...

    Indian Academy of Sciences (India)

    Department of Chemistry, Faculty of Sciences, University of Birjand, P. O. Box 97175-615, Birjand, Iran. Email: a_allahresani@birjand.ac.ir; ... metals have a key role in coordination chemistry.3 6. They can be prepared simply and ...... mer supported cobalt (II) catalysts for alkene epoxida- tion Appl. Catal. A: Gen. 247 295.

  18. Heavy fluorous phosphine-free ruthenium catalysts for alkene metathesis

    Czech Academy of Sciences Publication Activity Database

    Babuněk, M.; Šimůnek, O.; Hošek, J.; Rybáčková, M.; Cvačka, Josef; Březinová, Anna; Kvíčala, J.

    2014-01-01

    Roč. 161, May (2014), s. 66-75 ISSN 0022-1139 Grant - others:GA ČR(CZ) GAP207/10/1533 Institutional support: RVO:61388963 Keywords : Hoveyda-Grubbs * ruthenium complex * fluorous * alkene metathesis * perfluoropolyether Subject RIV: CC - Organic Chemistry Impact factor: 1.948, year: 2014

  19. Unidirectional Light-Driven Molecular Motors Based on Overcrowded Alkenes

    NARCIS (Netherlands)

    Cnossen, Arjen; Browne, Wesley R.; Feringa, Ben L.; Credi, Alberto; Silvi, Serena; Venturi, Margherita

    2014-01-01

    Over the last two decades, interest in nanotechnology has led to the design and synthesis of a toolbox of nanoscale versions of macroscopic devices and components. In molecular nanotechnology, linear motors based on rotaxanes and rotary motors based on overcrowded alkenes are particularly promising

  20. Homogeneous oxidation of alcohol and alkene with copper (II ...

    Indian Academy of Sciences (India)

    Hakan Ünver

    2018-03-19

    Mar 19, 2018 ... hydroformylation,8 and hydrogenation.9 In synthetic chemical production processes, such as those in the dye, pigment, medicine, and perfume industries, selective alcohol and alkene oxidations are important reactions for obtaining numerous starting or intermediate chem- icals, aldehydes, ketones, diols, ...

  1. Atmospheric Gas-Phase Reactions of Fluorinated Compounds and Alkenes

    DEFF Research Database (Denmark)

    Østerstrøm, Freja From

    Experimental studies have been performed using three different smog chamber setups to investigate the atmospheric chemistry of fluorinated compounds as well as alkenes. The three instruments were at Ford Motor Company, USA, National Center for Atmospheric Research, USA, and Copenhagen Center...

  2. Heuristical Strategies on the Study Theme "The Unsaturated Hydrocarbons -- Alkenes"

    Science.gov (United States)

    Naumescu, Adrienne Kozan; Pasca, Roxana-Diana

    2011-01-01

    The influence of heuristical strategies upon the level of two experimental classes is studied in this paper. The didactic experiment took place at secondary school in Cluj-Napoca, in 2008-2009 school year. The study theme "The Unsaturated Hydrocarbons--Alkenes" has been efficiently learned by using the most active methods: laboratory…

  3. Direct C–H trifluoromethylation of di- and trisubstituted alkenes by photoredox catalysis

    Directory of Open Access Journals (Sweden)

    Ren Tomita

    2014-05-01

    Full Text Available Background: Trifluoromethylated alkene scaffolds are known as useful structural motifs in pharmaceuticals and agrochemicals as well as functional organic materials. But reported synthetic methods usually require multiple synthetic steps and/or exhibit limitation with respect to access to tri- and tetrasubstituted CF3-alkenes. Thus development of new methodologies for facile construction of Calkenyl–CF3 bonds is highly demanded.Results: The photoredox reaction of alkenes with 5-(trifluoromethyldibenzo[b,d]thiophenium tetrafluoroborate, Umemoto’s reagent, as a CF3 source in the presence of [Ru(bpy3]2+ catalyst (bpy = 2,2’-bipyridine under visible light irradiation without any additive afforded CF3-substituted alkenes via direct Calkenyl–H trifluoromethylation. 1,1-Di- and trisubstituted alkenes were applicable to this photocatalytic system, providing the corresponding multisubstituted CF3-alkenes. In addition, use of an excess amount of the CF3 source induced double C–H trifluoromethylation to afford geminal bis(trifluoromethylalkenes.Conclusion: A range of multisubstituted CF3-alkenes are easily accessible by photoredox-catalyzed direct C–H trifluoromethylation of alkenes under mild reaction conditions. In particular, trifluoromethylation of triphenylethene derivatives, from which synthetically valuable tetrasubstituted CF3-alkenes are obtained, have never been reported so far. Remarkably, the present facile and straightforward protocol is extended to double trifluoromethylation of alkenes.

  4. Highly efficient epoxidation of alkenes with m-chloroperbenzoic acid ...

    Indian Academy of Sciences (India)

    Co@Fe3O4/SiO2. Cl. OOH. O. Cl. OH. O. Scheme 1. Schematic illustration for the epoxidation of alkenes. 2. Experimental. 2.1 Materials. Tetraethoxysilane (TEOS), FeCl3·6H2O, FeCl2·4H2O, styrene, ... 1.5mL of TEOS was added dropwise to the mixture and ..... a high saturation magnetization value (34.3emug. −1. ).

  5. Alkene Metathesis and Renewable Materials: Selective Transformations of Plant Oils

    Science.gov (United States)

    Malacea, Raluca; Dixneuf, Pierre H.

    The olefin metathesis of natural oils and fats and their derivatives is the basis of clean catalytic reactions relevant to green chemistry processes and the production of generate useful chemicals from renewable raw materials. Three variants of alkene metathesis: self-metathesis, ethenolysis and cross-metathesis applied to plant oil derivatives will show new routes to fine chemicals, bifunctional products, polymer precursours and industry intermediates.

  6. Effect of C6 to C9 alkenals on aflatoxin production in corn, cottonseed, and peanuts.

    OpenAIRE

    Zeringue, H J

    1991-01-01

    The effect on aflatoxin production in Aspergillus flavus-inoculated corn, cottonseed, and peanuts in static culture in the presence of gaseous phase C6 to C9 alkenals was investigated. Aflatoxin B1 production was stimulated in corn at the lowest alkenal concentration (1-microliters level) tested. Aflatoxin B1 was completely eliminated at the highest alkenal concentrations (20-microliters level) tested in both treated corn and cottonseed cultures.

  7. Abundance of DNA adducts of 4-oxo-2-alkenals, lipid peroxidation-derived highly reactive genotoxins.

    Science.gov (United States)

    Kawai, Yoshichika; Nuka, Erika

    2018-01-01

    Reactive oxygen species and their reaction products can damage DNA to form mutagenic lesions. Among the reactive species, lipid peroxidation-derived aldehydes react with nucleobases and form bulky exocyclic adducts. Many types of aldehyde-derived DNA adducts have been characterized, identified and detected in vitro and in vivo , whereas relative quantitative and pathophysiological contributions of each adduct still remain unclear. In recent years, an abundant class of DNA adducts derived from 4-oxo-2-alkenals have been identified, in addition to classic aldehyde-derived adducts. The presence of 4-oxo-2-alkenal-derived DNA adducts associated with age-related diseases has been revealed in rodents and humans. In vitro studies have demonstrated that 4-oxo-2-alkenals, as compared with other classes of lipid peroxidation-derived aldehydes, are highly reactive with nucleobases. It has been generally recognized that 4-oxo-2-alkenals are generated through oxidative degradation of the corresponding 4-hydroperoxy-2-alkenals, homolytic degradation products of polyunsaturated fatty acid hydroperoxides. Our recent results have also shown an alternative pathway for the formation of 4-oxo-2-alkenals, in which 2-alkenals could undergo the metal-catalyzed autoxidation resulting in the formation of the corresponding 4-oxo-2-alkenals. This review summarizes the basis of the formation of lipid peroxidation-derived genotoxic aldehydes and their covalent adduction to nucleobases, especially focusing on the abundance of 4-oxo-2-alkenal-derived DNA adducts.

  8. Methods of producing epoxides from alkenes using a two-component catalyst system

    Science.gov (United States)

    Kung, Mayfair C.; Kung, Harold H.; Jiang, Jian

    2013-07-09

    Methods for the epoxidation of alkenes are provided. The methods include the steps of exposing the alkene to a two-component catalyst system in an aqueous solution in the presence of carbon monoxide and molecular oxygen under conditions in which the alkene is epoxidized. The two-component catalyst system comprises a first catalyst that generates peroxides or peroxy intermediates during oxidation of CO with molecular oxygen and a second catalyst that catalyzes the epoxidation of the alkene using the peroxides or peroxy intermediates. A catalyst system composed of particles of suspended gold and titanium silicalite is one example of a suitable two-component catalyst system.

  9. Synthesis, stereochemistry, and photochemical and thermal behaviour of bis-tert-butyl substituted overcrowded alkenes

    NARCIS (Netherlands)

    K. J. Ter Wiel, M.; G. Kwit, M.; Meetsma, A.; Feringa, B.L.

    2007-01-01

    In order to study the structural limits in the design of molecular motors, a tert-butyl substituted analogue was prepared. The unexpected photochemical and thermal isomerisation processes and the stereochemistry of new overcrowded alkene 5 are described. The bis tert-butyl substituted alkenes were

  10. Cobalt-catalyzed C-H olefination of aromatics with unactivated alkenes.

    Science.gov (United States)

    Manoharan, Ramasamy; Sivakumar, Ganesan; Jeganmohan, Masilamani

    2016-08-18

    A cobalt-catalyzed C-H olefination of aromatic and heteroaromatic amides with unactivated alkenes, allyl acetates and allyl alcohols is described. This method offers an efficient route for the synthesis of vinyl and allyl benzamides in a highly stereoselective manner. It is observed that the ortho substituent on the benzamide moiety is crucial for the observation of allylated products in unactivated alkenes.

  11. Regioselective Wacker Oxidation of Internal Alkenes: Rapid Access to Functionalized Ketones Facilitated by Cross-Metathesis

    KAUST Repository

    Morandi, Bill

    2013-07-26

    Wacka wacka: The title reaction makes use of a wide range of directing groups (DG) to enable the highly regioselective oxidation of alkenes, and occurs predictably at the distal position. Both E and Z alkenes afford valuable functionalized ketones and cross-metathesis was shown to facilitate the preparation of the starting materials. BQ=benzoquinone.

  12. Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Hitoshi; Thalji, Reema; Bergman, Robert; Ellman, Jonathan

    2008-05-22

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe){sub 2}]{sub 2} and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

  13. Enantioselective intramolecular hydroarylation of alkenes via directed C-H bond activation.

    Science.gov (United States)

    Harada, Hitoshi; Thalji, Reema K; Bergman, Robert G; Ellman, Jonathan A

    2008-09-05

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe)2]2 and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer.

  14. Enantioselective Intramolecular Hydroarylation of Alkenes via Directed C–H Bond Activation

    Science.gov (United States)

    Harada, Hitoshi; Thalji, Reema K.; Bergman, Robert G.; Ellman, Jonathan A.

    2008-01-01

    Highly enantioselective catalytic intramolecular ortho-alkylation of aromatic imines containing alkenyl groups tethered at the meta position relative to the imine directing group has been achieved using [RhCl(coe)2]2 and chiral phosphoramidite ligands. Cyclization of substrates containing 1,1- and 1,2-disubstituted as well as trisubstituted alkenes were achieved with enantioselectivities >90% ee for each substrate class. Cyclization of substrates with Z-alkene isomers proceeded much more efficiently than substrates with E-alkene isomers. This further enabled the highly stereoselective intramolecular alkylation of certain substrates containing Z/E-alkene mixtures via a Rh-catalyzed alkene isomerization with preferential cyclization of the Z-isomer. PMID:18681407

  15. Genes involved in long-chain alkene biosynthesis in Micrococcus luteus

    Energy Technology Data Exchange (ETDEWEB)

    Beller, Harry R.; Goh, Ee-Been; Keasling, Jay D.

    2010-01-07

    Aliphatic hydrocarbons are highly appealing targets for advanced cellulosic biofuels, as they are already predominant components of petroleum-based gasoline and diesel fuels. We have studied alkene biosynthesis in Micrococcus luteus ATCC 4698, a close relative of Sarcina lutea (now Kocuria rhizophila), which four decades ago was reported to biosynthesize iso- and anteiso branched, long-chain alkenes. The underlying biochemistry and genetics of alkene biosynthesis were not elucidated in those studies. We show here that heterologous expression of a three-gene cluster from M. luteus (Mlut_13230-13250) in a fatty-acid overproducing E. coli strain resulted in production of long-chain alkenes, predominantly 27:3 and 29:3 (no. carbon atoms: no. C=C bonds). Heterologous expression of Mlut_13230 (oleA) alone produced no long-chain alkenes but unsaturated aliphatic monoketones, predominantly 27:2, and in vitro studies with the purified Mlut_13230 protein and tetradecanoyl-CoA produced the same C27 monoketone. Gas chromatography-time of flight mass spectrometry confirmed the elemental composition of all detected long-chain alkenes and monoketones (putative intermediates of alkene biosynthesis). Negative controls demonstrated that the M. luteus genes were responsible for production of these metabolites. Studies with wild-type M. luteus showed that the transcript copy number of Mlut_13230-13250 and the concentrations of 29:1 alkene isomers (the dominant alkenes produced by this strain) generally corresponded with bacterial population over time. We propose a metabolic pathway for alkene biosynthesis starting with acyl-CoA (or -ACP) thioesters and involving decarboxylative Claisen condensation as a key step, which we believe is catalyzed by OleA. Such activity is consistent with our data and with the homology (including the conserved Cys-His-Asn catalytic triad) of Mlut_13230 (OleA) to FabH (?-ketoacyl-ACP synthase III), which catalyzes decarboxylative Claisen condensation during

  16. Methoxycarbonylation of alkenes with biomass-derived CO

    DEFF Research Database (Denmark)

    Paolicchi, Dario

    The production of chemicals, fuels and energy from renewable feedstock, such as biomass, has seen increasing interest in the last decade. One of the key issues regarding biorenewables is the reduction of the oxygenation grade in molecules, the removal of oxygen. This thesis focuses on the removal......), and GVL,the three products we investigated. The catalytic system is optimized, following the indication given by the results of the reactions. All the steps of the process are deeply discussed in this section. Consideration on the reaction time, on the choice and the quantity of the acidic catalyst......, the nature and the amount of the palladium precursor and the phosphine ligand, a screening of the reaction temperatures, and an investigation regarding different substrates (with a furanic backbone), alkenes and alcohols have been done. Our catalytic system proved to be valid to give good yields in a one...

  17. A biocompatible alkene hydrogenation merges organic synthesis with microbial metabolism.

    Science.gov (United States)

    Sirasani, Gopal; Tong, Liuchuan; Balskus, Emily P

    2014-07-21

    Organic chemists and metabolic engineers use orthogonal technologies to construct essential small molecules such as pharmaceuticals and commodity chemicals. While chemists have leveraged the unique capabilities of biological catalysts for small-molecule production, metabolic engineers have not likewise integrated reactions from organic synthesis with the metabolism of living organisms. Reported herein is a method for alkene hydrogenation which utilizes a palladium catalyst and hydrogen gas generated directly by a living microorganism. This biocompatible transformation, which requires both catalyst and microbe, and can be used on a preparative scale, represents a new strategy for chemical synthesis that combines organic chemistry and metabolic engineering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Engineering 1-Alkene Biosynthesis and Secretion by Dynamic Regulation in Yeast

    DEFF Research Database (Denmark)

    Zhou, Yongjin J.; Hu, Yating; Zhu, Zhiwei

    2018-01-01

    product secretion. Here, we engineered the budding yeast Saccharomyces cerevisiae to produce and secrete 1-alkenes by manipulation of the fatty acid metabolism, enzyme selection, engineering the electron transfer system and expressing a transporter. Furthermore, we implemented a dynamic regulation...... strategy to control the expression of membrane enzyme and 1-alkene production and cell growth by relieving the possible toxicity of overexpressed membrane proteins. With these efforts, the engineered yeast cell factory produced 35.3 mg/L 1-alkenes with more than 80% being secreted. This represents a 10...

  19. Tandem ring-closing metathesis/transfer hydrogenation: practical chemoselective hydrogenation of alkenes.

    Science.gov (United States)

    Connolly, Timothy; Wang, Zhongyu; Walker, Michael A; McDonald, Ivar M; Peese, Kevin M

    2014-09-05

    An operationally simple chemoselective transfer hydrogenation of alkenes using ruthenium metathesis catalysts is presented. Of great practicality, the transfer hydrogenation reagents can be added directly to a metathesis reaction and effect hydrogenation of the product alkene in a single pot at ambient temperature without the need to seal the vessel to prevent hydrogen gas escape. The reduction is applicable to a range of alkenes and can be performed in the presence of aryl halides and benzyl groups, a notable weakness of Pd-catalyzed hydrogenations. Scope and mechanistic considerations are presented.

  20. Synthesis and dynamic behaviour of new metallo-based sterically overcrowded alkenes

    NARCIS (Netherlands)

    Smid, WI; Schoevaars, AM; Kruizinga, W; Veldman, N; Smeets, WJJ; Spek, AL; Feringa, BL; Smeets, Wilberth J.J.; Spek, Anthony L.; Feringa, Bernard

    1996-01-01

    The synthesis and crystal and molecular structures of novel metallo-based sterically overcrowded alkenes are reported and dynamic H-1 NMR studies reveals that the isomerization barriers are dramatically increased on metal coordination.

  1. Biobased production of alkanes and alkenes through metabolic engineering of microorganisms

    DEFF Research Database (Denmark)

    Kang, Min Kyoung; Nielsen, Jens

    2017-01-01

    Advancement in metabolic engineering of microorganisms has enabled bio-based production of a range of chemicals, and such engineered microorganism can be used for sustainable production leading to reduced carbon dioxide emission there. One area that has attained much interest is microbial...... hydrocarbon biosynthesis, and in particular, alkanes and alkenes are important high-value chemicals as they can be utilized for a broad range of industrial purposes as well as ‘drop-in’ biofuels. Some microorganisms have the ability to biosynthesize alkanes and alkenes naturally, but their production level...... is extremely low. Therefore, there have been various attempts to recruit other microbial cell factories for production of alkanes and alkenes by applying metabolic engineering strategies. Here we review different pathways and involved enzymes for alkane and alkene production and discuss bottlenecks...

  2. Development of chiral terminal-alkene-phosphine hybrid ligands for palladium-catalyzed asymmetric allylic substitutions.

    Science.gov (United States)

    Liu, Zhaoqun; Du, Haifeng

    2010-07-02

    A variety of novel chiral terminal-alkene-phosphine hybrid ligands were successfully developed from diethyl L-tartrate for palladium-catalyzed asymmetric allylic alkylations, etherifications, and amination to give the desired products in excellent yields and ee's.

  3. Alkadienes and alkenes, sex pheromone components of the almond seed wasp Eurytoma amygdali.

    Science.gov (United States)

    Krokos, F D; Konstantopoulou, M A; Mazomenos, B E

    2001-11-01

    Whole body extracts of virgin Eurytoma amygdali females were attractive to males in laboratory bioassays. Extracts of various body parts of the female wasp elicited different responses to males, with the thorax extract being the most active. Preparative fractionation of the crude hydrocarbon extract on a silver nitrate impregnated silica gel column (alkanes, alkenes, and alkadienes) revealed that the highest male response was elicited by alkadienes and the lowest by alkenes, with the alkane fraction being inactive. The identification of alkenes and alkadienes was based on gas chromatographic, mass spectrometric, and gas-phase infrared data. Laboratory bioassays suggested that the two alkadienes, (Z,Z)-6,9-tricosadiene [(Z,Z)-6,9-C23:2], and (Z,Z)-6,9-pentacosadiene [(Z,Z)-6,9-C25:2], and to a lesser extent alkenes, identified in the female extract of E. amygdali were male attractants.

  4. Recent advances in the ruthenium(ii)-catalyzed chelation-assisted C-H olefination of substituted aromatics, alkenes and heteroaromatics with alkenes via the deprotonation pathway.

    Science.gov (United States)

    Manikandan, Rajendran; Jeganmohan, Masilamani

    2017-08-08

    The transition-metal-catalyzed chelation-assisted alkenylation at the inert C-H bond of aromatics with alkenes is one of the efficient methods to synthesize substituted vinylarenes in a highly regio- and stereoselective manner. Palladium, rhodium and ruthenium complexes are frequently used as catalysts for this type of transformation. The present review describes the recent advances in the ruthenium-catalyzed chelation-assisted alkenylation at the C-H bond of aromatics, alkenes and heteroaromatics with alkenes via the deprotonation pathway. Several directing groups including 2-pyridyl, carbonyl, amidine, amide, amine, imidate, sulphonic acid, triazole, cyano, oxazolidinone and hydontoin are widely used in the reaction. The scope, limitation and mechanistic investigation of the alkenylation reactions are discussed elaborately. This feature article includes all the reported ruthenium-catalyzed alkenylation reactions via the deprotonation pathway until the end of March 2017.

  5. Copper-catalyzed intermolecular trifluoromethylazidation of alkenes: convenient access to CF3 -containing alkyl azides.

    Science.gov (United States)

    Wang, Fei; Qi, Xiaoxu; Liang, Zhaoli; Chen, Pinhong; Liu, Guosheng

    2014-02-10

    A novel copper-catalyzed intermolecular trifluoromethylazidation of alkenes has been developed under mild reaction conditions. A variety of CF3 -containing organoazides were directly synthesized from a wide range of olefins, including activated and unactivated alkenes, and the resulting products can be easily transformed into the corresponding CF3 -containing amine derivatives. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Intramolecular Azide to Alkene Cycloadditions for the Construction of Pyrrolobenzodiazepines and Azetidino-Benzodiazepines

    Directory of Open Access Journals (Sweden)

    Karl Hemming

    2014-10-01

    Full Text Available The coupling of proline- and azetidinone-substituted alkenes to 2-azidobenzoic and 2-azidobenzenesulfonic acid gives precursors that undergo intramolecular azide to alkene 1,3-dipolar cycloadditions to give imine-, triazoline- or aziridine-containing pyrrolo[1,4]benzodiazepines (PBDs, pyrrolo[1,2,5]benzothiadiazepines (PBTDs, and azetidino[1,4]benzodiazepines. The imines and aziridines are formed after loss of nitrogen from a triazoline cycloadduct. The PBDs are a potent class of antitumour antibiotics.

  7. A New Mn–Salen Micellar Nanoreactor for Enantioselective Epoxidation of Alkenes in Water

    Directory of Open Access Journals (Sweden)

    Francesco P. Ballistreri

    2018-03-01

    Full Text Available A new chiral Mn–salen catalyst, functionalized with a long aliphatic chain and a choline group, able to act as surfactant catalyst for green epoxidation in water, is here described. This catalyst was employed with a commercial surfactant (CTABr leading to a nanoreactor for the enantioselective epoxidation of some selected alkenes in water, using NaClO as oxidant. This is the first example of a nanoreactor for enantioselective epoxidation of non-functionalized alkenes in water.

  8. Branched-Selective Intermolecular Ketone α-Alkylation with Unactivated Alkenes via an Enamide Directing Strategy.

    Science.gov (United States)

    Xing, Dong; Dong, Guangbin

    2017-10-04

    We describe a strategy for intermolecular branched-selective α-alkylation of ketones using simple alkenes as the alkylating agents. Enamides derived from isoindolin-1-one provide an excellent directing template for catalytic activation of ketone α-positions. High branched selectivity is obtained for both aliphatic and aromatic alkenes using a cationic iridium catalyst. Preliminary mechanistic study favors an Ir-C migratory insertion pathway.

  9. Spectroscopic and Theoretical Identification of Two Thermal Isomerization Pathways for Bistable Chiral Overcrowded Alkenes.

    Science.gov (United States)

    Kistemaker, Jos C M; Pizzolato, Stefano F; van Leeuwen, Thomas; Pijper, Thomas C; Feringa, Ben L

    2016-09-12

    Chiroptical molecular switches play an important role in responsive materials and dynamic molecular systems. Here we present the synthesis of four chiral overcrowded alkenes and the experimental and computational study of their photochemical and thermal behavior. By irradiation with UV light, metastable diastereoisomers with opposite helicity were generated through high yielding E-Z isomerizations. Kinetic studies on metastable 1-4 using CD spectroscopy and HPLC analysis revealed two pathways at higher temperatures for the thermal isomerization, namely a thermal E-Z isomerization (TEZI) and a thermal helix inversion (THI). These processes were also studied computationally whereby a new strategy was developed for calculating the TEZI barrier for second-generation overcrowded alkenes. To demonstrate that these overcrowded alkenes can be employed as bistable switches, photochromic cycling was performed, which showed that the alkenes display good selectivity and fatigue resistance over multiple irradiation cycles. In particular, switch 3 displayed the best performance in forward and backward photoswitching, while 1 excelled in thermal stability of the photogenerated metastable form. Overall, the alkenes studied showed a remarkable and unprecedented combination of switching properties including dynamic helicity, reversibility, selectivity, fatigue resistance, and thermal stability. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Chemoenzymatic Epoxidation of Alkenes and Reusability Study of the Phenylacetic Acid

    Directory of Open Access Journals (Sweden)

    Emilia Abdulmalek

    2014-01-01

    Full Text Available Here, we focused on a simple enzymatic epoxidation of alkenes using lipase and phenylacetic acid. The immobilised Candida antarctica lipase B, Novozym 435 was used to catalyse the formation of peroxy acid instantly from hydrogen peroxide (H2O2 and phenylacetic acid. The peroxy phenylacetic acid generated was then utilised directly for in situ oxidation of alkenes. A variety of alkenes were oxidised with this system, resulting in 75–99% yield of the respective epoxides. On the other hand, the phenylacetic acid was recovered from the reaction media and reused for more epoxidation. Interestingly, the waste phenylacetic acid had the ability to be reused for epoxidation of the 1-nonene to 1-nonene oxide, giving an excellent yield of 90%.

  11. In tandem or alone: a remarkably selective transfer hydrogenation of alkenes catalyzed by ruthenium olefin metathesis catalysts.

    Science.gov (United States)

    Zieliński, Grzegorz Krzysztof; Samojłowicz, Cezary; Wdowik, Tomasz; Grela, Karol

    2015-03-07

    A system for transfer hydrogenation of alkenes, composed of a ruthenium metathesis catalyst and HCOOH, is presented. This operationally simple system can be formed directly after a metathesis reaction to effect hydrogenation of the metathesis product in a single-pot. These hydrogenation conditions are applicable to a wide range of alkenes and offer remarkable selectivity.

  12. Photochemical Synthesis and Ligand Exchange Reactions of Ru(CO)[subscript 4] (Eta[superscript 2]-Alkene) Compounds

    Science.gov (United States)

    Cooke, Jason; Berry, David E.; Fawkes, Kelli L.

    2007-01-01

    The photochemical synthesis and subsequent ligand exchange reactions of Ru(CO)[subscript 4] (eta[superscript2]-alkene) compounds has provided a novel experiment for upper-level inorganic chemistry laboratory courses. The experiment is designed to provide a system in which the changing electronic properties of the alkene ligands could be easily…

  13. Chiral diamine-silver(I)-alkene complexes: a quantum chemical and NMR study

    DEFF Research Database (Denmark)

    Kieken, Elsa; Wiest, Olaf; Helquist, Paul

    2005-01-01

    The ability of chiral diamine silver complexes to bind chiral and prochiral alkenes has been analyzed in detail. The stereoselectivity in binding of alkenes to a chiral ethanediamine silver complex has been investigated by NMR. The low-energy conformations of several small model complexes have been...... calculation of stereoselectivities that match well the experimental results. For a chiral allylic alcohol substrate, the correct stereoselectivity was obtained only when the structures were optimized with a continuum representation of the solvent. The discrepancy between gas phase and solution data is found...

  14. Hydrochloric Acid-Promoted Intermolecular 1,2-Thiofunctionalization of Aromatic Alkenes.

    Science.gov (United States)

    Li, Xiaomeng; Guo, Yunlong; Shen, Zengming

    2018-03-02

    An efficient method for making 1,2-thiofunctionalized products via the difunctionalization of aromatic alkenes was developed. In this method, cheap and readily available hydrochloric acid was used to promote 1,2-thiofunctionalization of aryl alkenes with N-arylsulfenylphthalimide and different types of nucleophiles. Importantly, extension of nucleophiles can reach aryl ethers, indoles, and carboxylic acids with good reactivity. This practical and convenient method has broad substrate scope and high yields under metal-free and mild conditions. Furthermore, we achieved conversion and application for making sulfoxide and sulfone by oxidation.

  15. Arabinose-derived ketones as catalysts for asymmetric epoxidation of alkenes.

    Science.gov (United States)

    Shing, Tony K M; Leung, Gulice Y C; Luk, To

    2005-09-02

    [reaction: see text] Readily available arabinose-derived ketones, containing a tunable butane-2,3-diacetal as the steric blocker, displayed increasing enantioselectivity (up to 90% ee) with the size of the acetal alkyl group in catalytic asymmetric epoxidation of trans-disubstituted and trisubstituted alkenes. The stereochemical communication between our ketone catalysts and the alkene substrates is mainly due to steric effect, and electronic effect involving pi-pi interaction between phenyl groups of substrate and of catalyst did not appear to be operative in our system.

  16. A new approach to ferrocene derived alkenes via copper-catalyzed olefination

    Directory of Open Access Journals (Sweden)

    Vasily M. Muzalevskiy

    2015-11-01

    Full Text Available A new approach to ferrocenyl haloalkenes and bis-alkenes was elaborated. The key procedure involves copper catalyzed olefination of N-unsubstituted hydrazones, obtained from ferrocene-containing carbonyl compounds and hydrazine, with polyhaloalkanes. The procedure is simple, cheap and could be applied for the utilization of environmentally harmful polyhalocarbons. The cyclic voltammetry study of the representative examples of the synthesized ferrocenyl alkenes shows the strong dependence of the cathodic behavior on the amount of vinyl groups: while for the monoalkene containing molecules no reduction is seen, the divinyl products are reduced in several steps.

  17. A new approach to ferrocene derived alkenes via copper-catalyzed olefination.

    Science.gov (United States)

    Muzalevskiy, Vasily M; Shastin, Aleksei V; Demidovich, Alexandra D; Shikhaliev, Namiq G; Magerramov, Abel M; Khrustalev, Victor N; Rakhimov, Rustem D; Vatsadze, Sergey Z; Nenajdenko, Valentine G

    2015-01-01

    A new approach to ferrocenyl haloalkenes and bis-alkenes was elaborated. The key procedure involves copper catalyzed olefination of N-unsubstituted hydrazones, obtained from ferrocene-containing carbonyl compounds and hydrazine, with polyhaloalkanes. The procedure is simple, cheap and could be applied for the utilization of environmentally harmful polyhalocarbons. The cyclic voltammetry study of the representative examples of the synthesized ferrocenyl alkenes shows the strong dependence of the cathodic behavior on the amount of vinyl groups: while for the monoalkene containing molecules no reduction is seen, the divinyl products are reduced in several steps.

  18. Regioselective Pd-catalyzed methoxycarbonylation of alkenes using both paraformaldehyde and methanol as CO surrogates.

    Science.gov (United States)

    Liu, Qiang; Yuan, Kedong; Arockiam, Percia-Beatrice; Franke, Robert; Doucet, Henri; Jackstell, Ralf; Beller, Matthias

    2015-04-07

    In recent years, considerable effort has focused on the development of novel carbonylative transformations using CO surrogates. Consequently, toxic CO gas can be replaced by more convenient inorganic or organic carbonyl compounds. Herein, the first regioselective methoxycarbonylation of alkenes with paraformaldehyde and methanol as CO substitutes is reported. This new procedure is applicable to a series of alkenes in the presence of a palladium catalyst under relatively mild conditions and is highly atom efficient. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Addition of α,α-Difluoroiodomethyl Ketones to Alkenes with a Copper Catalyst

    International Nuclear Information System (INIS)

    Kwak, Kyung Chell; Lee, Woo Yiel; Lee, Young Hang; Yun, Young Gab; Chung, Hun Taeg; Kwon, Tae Oh; Chai, Kyu Yun; Zheshan, Quan; Kwak, Gyu Beum

    2005-01-01

    The addition reactions of α,α-difluoroiodomethyl n-butyl ketone, α,α-difluoroiodomethyl cyclohexyl ketone, or α,α-difluoroiodomethyl phenyl ketone to alkenes were successfully accomplished in good yields in the presence of copper powder. The reaction was also applicable to alkenes containing a variety of functional groups such as ester, trimethylsilyl, or ether group. Acetonitrile was determined to be the best solvent in the present study and the reaction was performed at 55 .deg. C for 15-22 h. This reaction provides a new, efficient and general method for the synthesis of α,α-difluoro functionalized ketones

  20. The syn/anti-Dichotomy in the Palladium-Catalyzed Addition of Nucleophiles to Alkenes

    Czech Academy of Sciences Publication Activity Database

    Kočovský, Pavel; Bäckvall, J. E.

    2015-01-01

    Roč. 21, č. 1 (2015), s. 36-56 ISSN 0947-6539 Institutional support: RVO:61388963 Keywords : alkenes * catalysis * nucleophilic addition * palladium * stereochemistry Subject RIV: CC - Organic Chemistry Impact factor: 5.771, year: 2015 http://onlinelibrary.wiley.com/doi/10.1002/chem.201404070/pdf

  1. Continuous flow hydrogenation of nitroarenes, azides and alkenes using maghemite-Pd nanocomposites

    Science.gov (United States)

    Maghemite-supported ultra-fine Pd (1-2 nm) nanoparticles, prepared by a simple co-precipitation method, find application in the catalytic continuous flow hydrogenation of nitroarenes, azides, and alkenes wherein they play an important role in reduction of various functional group...

  2. Synthesis of Alkyne and Alkene Ketal Derivatives of Pentacyclo[5.4 ...

    African Journals Online (AJOL)

    10 .0 5,9 ]undecane-8-11-dione and 1-Phenyl-pentacyclo[5.4.0.02,6.03,10.05 ... Reduction of the alkyne ketal derivatives using Pd/CaCO3 has been demonstrated to forma mixture containing the desired alkene ketal derivatives. KEYWORDS ...

  3. Copper-catalyzed asymmetric ring opening of oxabicyclic alkenes with organolithium reagents

    NARCIS (Netherlands)

    Bos, Pieter H.; Rudolph, Alena; Pérez, Manuel; Fañanás-Mastral, Martín; Harutyunyan, Syuzanna R.; Feringa, Bernard

    2012-01-01

    A highly efficient method is reported for the asymmetric ring opening of oxabicyclic alkenes with organolithium reagents. Using a copper/chiral phosphoramidite complex together with a Lewis acid (BF3·OEt2), full selectivity for the anti isomer and excellent enantioselectivities were obtained for the

  4. Tandem isomerization-decarboxylation for converting alkenoic fatty acids into alkenes

    Science.gov (United States)

    We report a facile Ru-catalyzed route to alkenes from alkenoic fatty acids via a readily accessible pre-catalyst [Ru(CO)2RCO2]n. The catalyst apparently functions in a tandem mode by dynamically isomerizing the positions of double bonds in an aliphatic chain and, subsequently, decarboxylating specif...

  5. Are Isomeric Alkenes Used in Species Recognition among Neo-Tropical Stingless Bees (Melipona Spp).

    Science.gov (United States)

    Martin, Stephen J; Shemilt, Sue; da S Lima, Cândida B; de Carvalho, Carlos A L

    2017-12-01

    Our understanding of the role of cuticular hydrocarbons (CHC) in recognition is based largely on temperate ant species and honey bees. The stingless bees remain relatively poorly studied, despite being the largest group of eusocial bees, comprising more than 400 species in some 60 genera. The Meliponini and Apini diverged between 80-130 Myr B.P. so the evolutionary trajectories that shaped the chemical communication systems in ants, honeybees and stingless bees may be very different. The aim of this study was to study if a unique species CHC signal existed in Neotropical stingless bees, as has been shown for many temperate species, and what compounds are involved. This was achieved by collecting CHC data from 24 colonies belonging to six species of Melipona from North-Eastern Brazil and comparing the results with previously published CHC studies on Melipona. We found that each of the eleven Melipona species studied so far each produced a unique species CHC signal based around their alkene isomer production. A remarkable number of alkene isomers, up to 25 in M. asilvai, indicated the diversification of alkene positional isomers among the stingless bees. The only other group to have really diversified in alkene isomer production are the primitively eusocial Bumblebees (Bombus spp), which are the sister group of the stingless bees. Furthermore, among the eleven Neotropical Melipona species we could detect no effect of the environment on the proportion of alkane production as has been suggested for some other species.

  6. Synthesis of E- and Z-trisubstituted alkenes by catalytic cross-metathesis

    Science.gov (United States)

    Nguyen, Thach T.; Koh, Ming Joo; Mann, Tyler J.; Schrock, Richard R.; Hoveyda, Amir H.

    2017-12-01

    Catalytic cross-metathesis is a central transformation in chemistry, yet corresponding methods for the stereoselective generation of acyclic trisubstituted alkenes in either the E or the Z isomeric forms are not known. The key problems are a lack of chemoselectivity—namely, the preponderance of side reactions involving only the less hindered starting alkene, resulting in homo-metathesis by-products—and the formation of short-lived methylidene complexes. By contrast, in catalytic cross-coupling, substrates are more distinct and homocoupling is less of a problem. Here we show that through cross-metathesis reactions involving E- or Z-trisubstituted alkenes, which are easily prepared from commercially available starting materials by cross-coupling reactions, many desirable and otherwise difficult-to-access linear E- or Z-trisubstituted alkenes can be synthesized efficiently and in exceptional stereoisomeric purity (up to 98 per cent E or 95 per cent Z). The utility of the strategy is demonstrated by the concise stereoselective syntheses of biologically active compounds, such as the antifungal indiacen B and the anti-inflammatory coibacin D.

  7. Effects of chemical complexity on the autoxidation mechanisms of endocyclic alkene ozonolysis products

    DEFF Research Database (Denmark)

    Rissanen, Matti P.; Kurtén, Theo; Sipilä, Mikko

    2015-01-01

    Formation of highly oxidized, multifunctional products in the ozonolysis of three endocyclic alkenes, 1- methylcyclohexene, 4-methylcyclohexene, and α-pinene, was investigated using a chemical ionization atmospheric pressure interface time-of-flight (CI-APi-TOF) mass spectrometer with a nitrate ion...

  8. Highly regio- and enantioselective multiple oxy- and amino-functionalizations of alkenes by modular cascade biocatalysis

    Science.gov (United States)

    Wu, Shuke; Zhou, Yi; Wang, Tianwen; Too, Heng-Phon; Wang, Daniel I. C.; Li, Zhi

    2016-01-01

    New types of asymmetric functionalizations of alkenes are highly desirable for chemical synthesis. Here, we develop three novel types of regio- and enantioselective multiple oxy- and amino-functionalizations of terminal alkenes via cascade biocatalysis to produce chiral α-hydroxy acids, 1,2-amino alcohols and α-amino acids, respectively. Basic enzyme modules 1–4 are developed to convert alkenes to (S)-1,2-diols, (S)-1,2-diols to (S)-α-hydroxyacids, (S)-1,2-diols to (S)-aminoalcohols and (S)-α-hydroxyacids to (S)-α-aminoacids, respectively. Engineering of enzyme modules 1 & 2, 1 & 3 and 1, 2 & 4 in Escherichia coli affords three biocatalysts over-expressing 4–8 enzymes for one-pot conversion of styrenes to the corresponding (S)-α-hydroxyacids, (S)-aminoalcohols and (S)-α-aminoacids in high e.e. and high yields, respectively. The new types of asymmetric alkene functionalizations provide green, safe and useful alternatives to the chemical syntheses of these compounds. The modular approach for engineering multi-step cascade biocatalysis is useful for developing other new types of one-pot biotransformations for chemical synthesis. PMID:27297777

  9. Alkene Metathesis Catalysis: A Key for Transformations of Unsaturated Plant Oils and Renewable Derivatives

    Directory of Open Access Journals (Sweden)

    Dixneuf Pierre H.

    2016-03-01

    Full Text Available This account presents the importance of ruthenium-catalysed alkene cross-metathesis for the catalytic transformations of biomass derivatives into useful intermediates, especially those developed by the authors in the Rennes (France catalysis team in cooperation with chemical industry. The cross-metathesis of a variety of functional alkenes arising from plant oils, with acrylonitrile and fumaronitrile and followed by catalytic tandem hydrogenation, will be shown to afford linear amino acid derivatives, the precursors of polyamides. The exploration of cross-metathesis of bio-sourced unsaturated nitriles with acrylate with further catalytic hydrogenation has led to offer an excellent route to α,ω-amino acid derivatives. That of fatty aldehydes has led to bifunctional long chain aldehydes and saturated diols. Two ways of access to functional dienes by ruthenium-catalyzed ene-yne cross-metathesis of plant oil alkene derivatives with alkynes and by cross-metathesis of bio-sourced alkenes with allylic chloride followed by catalytic dehydrohalogenation, are reported. Ricinoleate derivatives offer a direct access to chiral dihydropyrans and tetrahydropyrans via ring closing metathesis. Cross-metathesis giving value to terpenes and eugenol for the straightforward synthesis of artificial terpenes and functional eugenol derivatives without C=C bond isomerization are described.

  10. Synthesis and molecular structure of chiral metallo-based sterically overcrowded alkenes

    NARCIS (Netherlands)

    Wiel, Matthijs K.J. ter; Meetsma, Auke; Feringa, Bernard

    2002-01-01

    A four step synthesis of pyridyl-2-yl-thioxanthen-9-ylidene-isoquinolines is described. The corresponding palladium complexes are the first examples of a novel class of chiral, metallo-based, sterically overcrowded alkenes. The crystal and molecular structure of the palladium dichloride complex

  11. Reversible gel-sol photoswitching with an overcrowded alkene-based bis-urea supergelator

    NARCIS (Netherlands)

    Wezenberg, Sander J.; Croisetu, Christelle M.; Stuart, Marc C. A.; Feringa, Ben L.

    2016-01-01

    A new type of low-molecular-weight gelator (LMWG), i.e. overcrowded alkene-based bis-ureas, can be switched effectively between cis and trans isomers using light as demonstrated by H-1 NMR and UV-Vis spectroscopy. Gelation studies reveal that one of the synthesized trans compounds forms stable gels

  12. Spectroscopic and Theoretical Identification of Two Thermal Isomerization Pathways for Bistable Chiral Overcrowded Alkenes

    NARCIS (Netherlands)

    Kistemaker, Jos C. M.; Pizzolato, Stefano F.; van Leeuwen, Thomas; Pijper, Thomas C.; Feringa, Ben L.

    2016-01-01

    Chiroptical molecular switches play an important role in responsive materials and dynamic molecular systems. Here we present the synthesis of four chiral overcrowded alkenes and the experimental and computational study of their photochemical and thermal behavior. By irradiation with UV light,

  13. Metallocene-catalyzed alkene polymerization and the observation of Zr-allyls

    Science.gov (United States)

    Landis, Clark R.; Christianson, Matthew D.

    2006-01-01

    Single-site polymerization catalysts enable exquisite control over alkene polymerization reactions to produce new materials with unique properties. Knowledge of catalyst speciation and fundamental kinetics are essential for full mechanistic understanding of zirconocene-catalyzed alkene polymerization. Currently the effect of activators on fundamental polymerization steps is not understood. Progress in understanding activator effects requires determination of fundamental kinetics for zirconocene catalysts with noncoordinating anions such as [B(C6F5)4]−. Kinetic NMR studies at low temperature demonstrate a very fast propagation rate for 1-hexene polymerization catalyzed by [(SBI)Zr(CH2SiMe3)][B(C6F5)4] [where SBI is rac-Me2Si(indenyl)2] with complete consumption of 1-hexene before the first NMR spectrum. Surprisingly, the first NMR spectrum reveals, aside from uninitiated catalyst, Zr-allyls as the sole catalyst-containing species. These Zr-allyls, which exist in two diastereomeric forms, have been characterized by physical and chemical methods. The mechanism of Zr-allyl formation was probed with a trapping experiment, leading us to favor a mechanism in which Zr-polymeryl undergoes β-H transfer to metal without dissociation of coordinated alkene followed by σ-bond metathesis to form H2 and Zr-allyl. Zr-allyl species undergo slow reactions with alkene but react rapidly with H2 to form hydrogenation products. PMID:17032772

  14. Concentrated Aqueous Sodium Tosylate as Green Medium for Alkene Oxidation and Nucleophilic Substitution Reactions.

    Science.gov (United States)

    Sela, Tal; Lin, Xiaoxi; Vigalok, Arkadi

    2017-11-03

    A hydrotropic solution of highly concentrated sodium tosylate (NaOTs) can be used as a recyclable medium for the environmentally benign oxidation of conjugated alkenes with H 2 O 2 . Both uncatalyzed and metal-catalyzed reactions provided the corresponding oxidation products in higher yields than in pure water or many common organic solvents.

  15. Manganese catalyzed cis-dihydroxylation of electron deficient alkenes with H2O2

    NARCIS (Netherlands)

    Saisaha, Pattama; Pijper, Dirk; van Summeren, Ruben P.; Hoen, Robert; Smit, Christian; de Boer, Johannes W.; Hage, Ronald; Alsters, Paul L.; Feringa, Bernard; Browne, Wesley R.

    2010-01-01

    A practical method for the multigram scale selective cis-dihydroxylation of electron deficient alkenes such as diethyl fumarate and N-alkyl and N-aryl-maleimides using H2O2 is described. High turnovers (>1000) can be achieved with this efficient manganese based catalyst system, prepared in situ from

  16. Nucleophilic conjugate trifluoromethylation of chromones and activated alkenes under the action of Ruppert’s reagent

    Directory of Open Access Journals (Sweden)

    V. Ya. Sosnovskikh

    2017-05-01

    Full Text Available This review summarizes data on the reactions of chromones and activated alkenes with trimethyl(trifluoromethylsilane (Ruppert’s reagent, which occures as a nucleophilic 1,4-trifluoromethylation with high regioselectivity and good yields. The most important chemical properties of the formed products are also considered.

  17. Carbon Dioxide Induced Alkene Extrusion from Bis(pentamethylcyclopentadienyl)titanium(III) Alkyls

    NARCIS (Netherlands)

    Luinstra, Gerrit A.; Teuben, Jan H.

    1987-01-01

    Reaction of titanium(III) alkyls, (η5-C5Me5)2TiR (R = Et or Prn), in toluene solution with CO2 proceeds at room temperature with formation of the titanium formate (η5-C5Me5)2TiO2CH, and the corresponding alkene (ethene or propene).

  18. Epoxidation of Alkenes with Aqueous Hydrogen Peroxide and Quaternary Ammonium Bicarbonate Catalysts

    DEFF Research Database (Denmark)

    Mielby, Jerrik Jørgen; Kegnæs, Søren

    2013-01-01

    A range of solid and liquid catalysts containing bicarbonate anions were synthesised and tested for the epoxidation of alkenes with aqueous hydrogen peroxide. The combination of bicarbonate anions and quaternary ammonium cations opens up for new catalytic systems that can help to overcome...

  19. Mechanism of the Hydrosilylation Reaction of Alkenes at Porous Silicon: Experimental and Computational Deuterium Labeling Studies

    NARCIS (Netherlands)

    Smet, de L.C.P.M.; Zuilhof, H.; Sudhölter, E.J.R.; Lie, L.H.; Houlton, A.; Horrocks, B.R.

    2005-01-01

    The mechanism of the formation of Si-C bonded monolayers on silicon by reaction of 1-alkenes with hydrogen-terminated porous silicon surfaces has been studied by both experimental and computational means. We propose that monolayer formation occurs via the same radical chain process as at

  20. Synthesis of insect pheromones belonging to the group of (Z)-trisubstituted alkenes

    Energy Technology Data Exchange (ETDEWEB)

    Grigorieva, Natalia Ya; Tsiklauri, Paata G [N.D.Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow (Russian Federation)

    2000-07-31

    Stereo- and regiocontrolled methods for the construction of a (Z)-trisubstituted C=C bond and for the regiospecific introduction of a chiral fragment are exemplified in total syntheses of insect pheromones belonging to (Z)-trisubstituted alkenes. The bibliography includes 113 references.

  1. Photochemical Covalent Attachment of Alkene-Derived Monolayers onto Hydroxyl-Terminated Silica

    NARCIS (Netherlands)

    Maat, ter J.; Regeling, R.; Yang, M.; Mullings, M.N.; Bent, S.F.; Zuilhof, H.

    2009-01-01

    The functionalization of optically transparent substrates is of importance, for example, in the field of biosensing. In this article, a new method for modification of silica surfaces is presented that is based on a photochemical reaction of terminal alkenes with the surface. This yields highly

  2. A shock tube study of C4–C6 straight chain alkenes + OH reactions

    KAUST Repository

    Khaled, Fathi

    2016-06-28

    Alkenes are known to be good octane boosters and they are major components of commercial fuels. Detailed theoretical calculations and direct kinetic measurements of elementary reactions of alkenes with combustion radicals are scarce for C4 alkenes and they are practically absent for C5 and larger alkenes. The overall rate coefficients for the reaction of OH radical with 1-butene (CH CHCH CH, k ), 1-pentene (CH CHCH CH-CH, k ), cis/trans 2-pentene (CH CHCHCH CH, k and k ), 1-hexene (CH CHCH CH CH CH, k ) and cis/trans 2-hexene (CH CHCHCH CH CH, k and k ) were measured behind reflected shock waves over the temperature range of 833-1377K and pressures near 1.5atm. The reaction progress was followed by measuring mole fraction of OH radicals near 306.7nm using UV laser absorption technique. It is found that the rate coefficients of OH+trans-2-alkenes are larger than those of OH+cis-2-alkenes, followed by OH+1-alkenes. The derived Arrhenius expressions for the overall rate coefficients (in cm.mol.s) are:. kI=(4.83±0.03)104.T2.72±0.01.exp(940.8±2.9cal/molRT)(946K-1256K) + kII=(5.66±0.54)10-1.T4.14±0.80.exp(4334±227cal/molRT)(875K-1379K) + kIII=(3.25±0.12)104.T2.76±0.5.exp(1962±83cal/molRT)(877K-1336K) + kIV=(3.42±0.09)104.T2.76±0.5.exp(1995±59cal/molRT)(833K-1265K) + kV=(7.65±0.58)10-4.T5±1.exp(5840±175cal/molRT)(836K-1387K) + kVI=(2.58±0.06)106.T2.17±0.37.exp(1461±55cal/molRT)(891K-1357K) + kVII=(3.08±0.05)106.T2.18±0.37.exp(1317±38cal/molRT)(881K-1377K) +

  3. Transfer Hydrogenation of Alkenes Using Ethanol Catalyzed by a NCP Pincer Iridium Complex: Scope and Mechanism.

    Science.gov (United States)

    Wang, Yulei; Huang, Zhidao; Leng, Xuebing; Zhu, Huping; Liu, Guixia; Huang, Zheng

    2018-03-28

    The first general catalytic approach to effecting transfer hydrogenation (TH) of unactivated alkenes using ethanol as the hydrogen source is described. A new NCP-type pincer iridium complex ( BQ -NC O P)IrHCl containing a rigid benzoquinoline backbone has been developed for efficient, mild TH of unactivated C-C multiple bonds with ethanol, forming ethyl acetate as the sole byproduct. A wide variety of alkenes, including multisubstituted alkyl alkenes, aryl alkenes, and heteroatom-substituted alkenes, as well as O- or N-containing heteroarenes and internal alkynes, are suitable substrates. Importantly, the ( BQ -NC O P)Ir/EtOH system exhibits high chemoselectivity for alkene hydrogenation in the presence of reactive functional groups, such as ketones and carboxylic acids. Furthermore, the reaction with C 2 D 5 OD provides a convenient route to deuterium-labeled compounds. Detailed kinetic and mechanistic studies have revealed that monosubstituted alkenes (e.g., 1-octene, styrene) and multisubstituted alkenes (e.g., cyclooctene (COE)) exhibit fundamental mechanistic difference. The OH group of ethanol displays a normal kinetic isotope effect (KIE) in the reaction of styrene, but a substantial inverse KIE in the case of COE. The catalysis of styrene or 1-octene with relatively strong binding affinity to the Ir(I) center has ( BQ -NC O P)Ir I (alkene) adduct as an off-cycle catalyst resting state, and the rate law shows a positive order in EtOH, inverse first-order in styrene, and first-order in the catalyst. In contrast, the catalysis of COE has an off-cycle catalyst resting state of ( BQ -NC O P)Ir III (H)[O(Et)···HO(Et)···HOEt] that features a six-membered iridacycle consisting of two hydrogen-bonds between one EtO ligand and two EtOH molecules, one of which is coordinated to the Ir(III) center. The rate law shows a negative order in EtOH, zeroth-order in COE, and first-order in the catalyst. The observed inverse KIE corresponds to an inverse equilibrium

  4. Failure and Redemption of Statistical and Nonstatistical Rate Theories in the Hydroboration of Alkenes.

    Science.gov (United States)

    Bailey, Johnathan O; Singleton, Daniel A

    2017-11-08

    Our previous work found that canonical forms of transition state theory incorrectly predict the regioselectivity of the hydroboration of propene with BH 3 in solution. In response, it has been suggested that alternative statistical and nonstatistical rate theories can adequately account for the selectivity. This paper uses a combination of experimental and theoretical studies to critically evaluate the ability of these rate theories, as well as dynamic trajectories and newly developed localized statistical models, to predict quantitative selectivities and qualitative trends in hydroborations on a broader scale. The hydroboration of a series of terminally substituted alkenes with BH 3 was examined experimentally, and a classically unexpected trend is that the selectivity increases as the alkyl chain is lengthened far from the reactive centers. Conventional and variational transition state theories can predict neither the selectivities nor the trends. The canonical competitive nonstatistical model makes somewhat better predictions for some alkenes but fails to predict trends, and it performs poorly with an alkene chosen to test a specific prediction of the model. Added nonstatistical corrections to this model make the predictions worse. Parametrized Rice-Ramsperger-Kassel-Marcus (RRKM)-master equation calculations correctly predict the direction of the trend in selectivity versus alkene size but overpredict its magnitude, and the selectivity with large alkenes remains unpredictable with any parametrization. Trajectory studies in explicit solvent can predict selectivities without parametrization but are impractical for predicting small changes in selectivity. From a lifetime and energy analysis of the trajectories, "localized RRKM-ME" and "competitive localized noncanonical" rate models are suggested as steps toward a general model. These provide the best predictions of the experimental observations and insight into the selectivities.

  5. Reversible Interconversion between Alkanes, Alkenes, Alcohols and Ketones under Hydrothermal Conditions

    Science.gov (United States)

    Shipp, J.; Hartnett, H. E.; Gould, I. R.; Shock, E.; Williams, L. B.

    2011-12-01

    Many transformation reactions involving hydrocarbons that occur in deep sedimentary systems and determine petroleum compositions occur in the presence of H2O. Hydrothermal transformations of organic material are thought to provide carbon sources for microbes in deep ocean sediments. Hydrothermal conditions may also mimic the conditions where life developed on an early Earth. Nevertheless, much remains to be learned about the mechanisms of hydrothermal organic reactions, including ways in which various reactions are interrelated and how reactions compete with each other. It can be argued that metastable equilibrium states develop over geological timescales and at geochemically relevant temperatures, suggesting that reactions occur under thermodynamic rather than kinetic control. The extent to which reactions are reversible, and how product distributions are determined, are primary tests of the metastable equilibrium model. Seewald (2001, GCA 65, 1641-1664) showed that under hydrothermal conditions and in the presence of a redox buffer, simple alkanes and alkenes undergo oxidation, reduction, and hydration reactions. He proposed a reaction scheme where alkanes interconvert with alkenes, followed by stepwise hydration of alkenes to alcohols, oxidation to ketones, and finally conversion to carboxylic acids, which can undergo decarboxylation. Here we describe experiments that further develop the scope of these functional group interconversions, determine relative reaction kinetics, and provide insight into competing reactions. Hydrothermal experiments were performed at 300°C and 100 MPa in gold capsules for 12 to 144 hours. The reactant structures were based on cyclohexane with one and two methyl groups that served as regio- and stereochemical markers for the reactions. Starting with the alkanes, the observed products include the corresponding alkenes, alcohols, ketones and enones, in support of the Seewald reaction scheme. Our experiments add a branch to this scheme

  6. Beyond Iron: Iridium-Containing P450 Enzymes for Selective Cyclopropanations of Structurally Diverse Alkenes

    International Nuclear Information System (INIS)

    Key, Hanna M.; Dydio, Paweł; Liu, Zhennan

    2017-01-01

    Enzymes catalyze organic transformations with exquisite levels of selectivity, including chemoselectivity, stereoselectivity, and substrate selectivity, but the types of reactions catalyzed by enzymes are more limited than those of chemical catalysts. Thus, the convergence of chemical catalysis and biocatalysis can enable enzymatic systems to catalyze abiological reactions with high selectivity. Recently, we disclosed artificial enzymes constructed from the apo form of heme proteins and iridium porphyrins that catalyze the insertion of carbenes into a C-H bond. Here, we postulated that the same type of Ir(Me)-PIX enzymes could catalyze the cyclopropanation of a broad range of alkenes with control of multiple modes of selectivity. Here, we report the evolution of artificial enzymes that are highly active and highly stereoselective for the addition of carbenes to a wide range of alkenes. These enzymes catalyze the cyclopropanation of terminal and internal, activated and unactivated, electron-rich and electron-deficient, conjugated and nonconjugated alkenes. In particular, Ir(Me)-PIX enzymes derived from CYP119 catalyze highly enantio- and diastereoselective cyclopropanations of styrene with ±98% ee, > 70:1 dr, > 75% yield, and ~10,000 turnovers (TON), as well as 1,2-disubstituted styrenes with up to 99% ee, 35:1 dr, and 54% yield. Moreover, Ir(Me)-PIX enzymes catalyze cyclopropanation of internal, unactivated alkenes with up to 99% stereoselectivity, 76% yield, and 1300 TON. They also catalyze cyclopropanation of natural products with diastereoselectivities that are complementary to those attained with standard transition metal catalysts. Finally, Ir(Me)-PIX P450 variants react with substrate selectivity that is reminiscent of natural enzymes; they react preferentially with less reactive internal alkenes in the presence of more reactive terminal alkenes. Altogether, the studies reveal the suitability of Ir-containing P450s to combine the broad reactivity and

  7. Upgrading light hydrocarbons via tandem catalysis: a dual homogeneous Ta/Ir system for alkane/alkene coupling.

    Science.gov (United States)

    Leitch, David C; Lam, Yan Choi; Labinger, Jay A; Bercaw, John E

    2013-07-17

    Light alkanes and alkenes are abundant but are underutilized as energy carriers because of their high volatility and low energy density. A tandem catalytic approach for the coupling of alkanes and alkenes has been developed in order to upgrade these light hydrocarbons into heavier fuel molecules. This process involves alkane dehydrogenation by a pincer-ligated iridium complex and alkene dimerization by a Cp*TaCl2(alkene) catalyst. These two homogeneous catalysts operate with up to 60/30 cooperative turnovers (Ir/Ta) in the dimerization of 1-hexene/n-heptane, giving C13/C14 products in 40% yield. This dual system can also effect the catalytic dimerization of n-heptane (neohexene as the H2 acceptor) with cooperative turnover numbers of 22/3 (Ir/Ta).

  8. Magnetic Fe@g‑C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

    Data.gov (United States)

    U.S. Environmental Protection Agency — A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically...

  9. Cobalt-mediated [3 + 2]-annulation reaction of alkenes with alpha,beta-unsaturated ketones and imines.

    Science.gov (United States)

    Schomaker, Jennifer M; Toste, F Dean; Bergman, Robert G

    2009-08-20

    The utility of cobalt dinitrosyl complexes for the [3 + 2] annulation of alkenes with unsaturated enones and ketimines has been demonstrated. Reaction of a series of cobalt dinitrosyl/alkene adducts with conjugate acceptors in the presence of Sc(OTf)(3)/LHMDS formed two new C-C bonds at the carbons alpha to the nitrosyl groups of the substrate, leading to unusual tri- and tetracycles. Retrocycloaddition of these products in the presence of norbornadiene yielded functionalized tetrasubstituted bicyclic olefins.

  10. Manganese catalyzed cis-dihydroxylation of electron deficient alkenes with H(2)O(2).

    Science.gov (United States)

    Saisaha, Pattama; Pijper, Dirk; van Summeren, Ruben P; Hoen, Rob; Smit, Christian; de Boer, Johannes W; Hage, Ronald; Alsters, Paul L; Feringa, Ben L; Browne, Wesley R

    2010-10-07

    A practical method for the multigram scale selective cis-dihydroxylation of electron deficient alkenes such as diethyl fumarate and N-alkyl and N-aryl-maleimides using H(2)O(2) is described. High turnovers (>1000) can be achieved with this efficient manganese based catalyst system, prepared in situ from a manganese salt, pyridine-2-carboxylic acid, a ketone and a base, under ambient conditions. Under optimized conditions, for diethyl fumarate at least 1000 turnovers could be achieved with only 1.5 equiv. of H(2)O(2) with d/l-diethyl tartrate (cis-diol product) as the sole product. For electron rich alkenes, such as cis-cyclooctene, this catalyst provides for efficient epoxidation.

  11. Palladium-catalyzed aryl C-H olefination with unactivated, aliphatic alkenes.

    Science.gov (United States)

    Deb, Arghya; Bag, Sukdev; Kancherla, Rajesh; Maiti, Debabrata

    2014-10-01

    Palladium-catalyzed coupling between aryl halides and alkenes (Mizoroki-Heck reaction) is one of the most popular reactions for synthesizing complex organic molecules. The limited availability, problematic synthesis, and higher cost of aryl halide precursors (or their equivalents) have encouraged exploration of direct olefination of aryl carbon-hydrogen (C-H) bonds (Fujiwara-Moritani reaction). Despite significant progress, the restricted substrate scope, in particular noncompliance of unactivated aliphatic olefins, has discouraged the use of this greener alternative. Overcoming this serious limitation, we report here a palladium-catalyzed chelation-assisted ortho C-H bond olefination of phenylacetic acid derivatives with unactivated, aliphatic alkenes in good to excellent yields with high regio- and stereoselectivities. The versatility of this operationally simple method has been demonstrated through drug diversification and sequential C-H olefination for synthesizing divinylbenzene derivatives.

  12. Ligand-enabled ortho-C-H olefination of phenylacetic amides with unactivated alkenes.

    Science.gov (United States)

    Lu, Ming-Zhu; Chen, Xing-Rong; Xu, Hui; Dai, Hui-Xiong; Yu, Jin-Quan

    2018-02-07

    Although chelation-assisted C-H olefination has been intensely investigated, Pd(ii)-catalyzed C-H olefination reactions are largely restricted to acrylates and styrenes. Here we report a quinoline-derived ligand that enables the Pd(ii)-catalyzed olefination of the C(sp 2 )-H bond with simple aliphatic alkenes using a weakly coordinating monodentate amide auxiliary. Oxygen is used as the terminal oxidant with catalytic copper as the co-oxidant. A variety of functional groups in the aliphatic alkenes are tolerated. Upon hydrogenation, the ortho -alkylated product can be accessed. The utility of this reaction is also demonstrated by the late-stage diversification of drug molecules.

  13. Postpolymerization Modifications of Alkene-Functional Polycarbonates for the Development of Advanced Materials Biomaterials.

    Science.gov (United States)

    Thomas, Anthony W; Dove, Andrew P

    2016-12-01

    Functional aliphatic polycarbonates have attracted significant attention as materials for use as biomedical polymers in recent years. The incorporation of pendent functionality offers a facile method of modifying materials postpolymerization, thus enabling functionalities not compatible with ring-opening polymerization (ROP) to be introduced into the polymer. In particular, polycarbonates bearing alkene-terminated functional groups have generated considerable interest as a result of their ease of synthesis, and the wide range of materials that can be obtained by performing simple postpolymerization modifications on this functionality, for example, through radical thiol-ene addition, Michael addition, and epoxidation reactions. This review presents an in-depth appraisal of the methods used to modify alkene-functional polycarbonates postpolymerization, and the diversity of practical applications for which these materials and their derivatives have been used. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Enabling the synthesis of medium chain alkanes and 1-alkenes in yeast

    DEFF Research Database (Denmark)

    Zhu, Zhiwei; Zhou, Yongjin J.; Kang, Min Kyoung

    2017-01-01

    Microbial synthesis of medium chain aliphatic hydrocarbons, attractive drop-in molecules to gasoline and jet fuels, is a promising way to reduce our reliance on petroleum-based fuels. In this study, we enabled the synthesis of straight chain hydrocarbons (C7–C13) by yeast Saccharomyces cerevisiae...... of fatty acids to 1-alkenes, which could be synthesized at a level of 3 mg/L, 25-fold higher than that of alkanes produced via aldehydes....

  15. Product Control in Alkene Trifluoromethylation: Hydrotrifluoromethylation, Vinylic Trifluoromethylation, and Iodotrifluoromethylation using Togni Reagent

    OpenAIRE

    Egami, Hiromichi; Usui, Yoshihiko; Kawamura, Shintaro; Nagashima, Sayoko; Sodeoka, Mikiko

    2015-01-01

    Hydrotrifluoromethylation, vinylic trifluoromethylation, and iodotrifluoromethylation of simple alkenes have been achieved by using Togni reagent in the absence of any transition metal catalyst. These reactions were readily controllable by selection of appropriate salts and solvents. The addition of K2CO3 afforded the hydrotrifluoromethylation product, with DMF acting not only as a solvent, but also as the hydrogen source. In contrast, the use of tetra-n-butylammonium iodide (TBAI) in 1,4-dio...

  16. Rhenium Oxide Supported on Mesoporous Organized Alumina as a Catalyst for Metathesis of 1-alkenes

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Hamtil, Roman; Žilková, Naděžda; Čejka, Jiří

    2004-01-01

    Roč. 97, 1/2 (2004), s. 25-29 ISSN 1011-372X R&D Projects: GA ČR GA203/02/0976; GA AV ČR IAA4040411 Institutional research plan: CEZ:AV0Z4040901 Keywords : organised mesoporous alumina * rhenium oxide * 1-alkene metathesis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 1.904, year: 2004

  17. Aerobic radical multifunctionalization of alkenes using tert-butyl nitrite and water

    Directory of Open Access Journals (Sweden)

    Daisuke Hirose

    2013-08-01

    Full Text Available Water induces a change in the product of radical multifunctionalization reactions of aliphatic alkenes involving an sp3 C–H functionalization by an 1,5-hydrogen shift using tert-butyl nitrite and molecular oxygen. The reaction without water, reported previously, gives nitrated γ-lactols, whereas the reaction in the presence of water produces 4-hydroxy-5-nitropentyl nitrate or 4-hydroxy-3-nitropentyl nitrate derivatives.

  18. Visible light-driven photocatalytic generation of sulfonamidyl radicals for alkene hydroamination of unsaturated sulfonamides.

    Science.gov (United States)

    Chen, Jun; Guo, Hong-Mei; Zhao, Quan-Qing; Chen, Jia-Rong; Xiao, Wen-Jing

    2018-02-05

    A visible light-driven photocatalytic generation of sulfonamidyl radicals, and application to intramolecular alkene hydroamination, has been accomplished, providing a mild and efficient approach to various functionalized isoxazolidines. The success of this protocol is based on the strategy of oxidative deprotonation electron transfer by merging the base and the photocatalyst under visible light irradiation, obviating installation of a photolabile handle or stoichiometric external oxidants.

  19. A comparative study on the sooting tendencies of various 1-alkene fuels in counterflow diffusion flames

    KAUST Repository

    Wang, Yu

    2018-02-19

    Alkenes are important components in transportation fuels, and are known to have increased sooting tendencies compared to analogous saturated hydrocarbons with the same carbon number. This work aims to understand the sooting tendencies of various 1-alkenes through experiments and numerical simulations for counterflow diffusion flames. Soot and PAH formation tendencies of 1-alkene fuels, including ethylene (C2H4), propene (C3H6), 1-butene (1-C4H8), 1-pentene (1-C5H10), 1-hexene (1-C6H12) and 1-octene (1-C8H16), were experimentally studied using laser induced-incandescence (LII) and laser-induced fluorescence (LIF) techniques, respectively. From the LII results, 1-C4H8 was found to be the most sooting fuel, followed by C3H6 > 1-C5H10 > 1-C6H12 > 1-C8H16 > C2H4. The LIF data with a detection wavelength of 500 nm indicated the PAH formation tendencies followed the order of 1-C4H8 > 1-C5H10 ∼1-C6H12 > C3H6 > 1-C8H16 > C2H4, which were different from the order of sooting tendencies. Numerical simulations with a comprehensive chemical kinetic model including PAH growth chemistry for the tested 1-alkene fuels were conducted to elucidate the aromatic formation pathways and rationalize the experimentally observed trends. The numerical results highlighted the importance of intermediate species with odd carbon numbers in aromatic species formation, such as propargyl, allyl, cyclopentadienyl and indenyl radicals. Their concentration differences, which could be traced back to the parent fuel molecules through rate of production analysis, rationalize the experimentally observed differences in soot and PAH formation tendencies.

  20. Evidence for Alkene cis-Aminocupration, an Aminooxygenation Case Study: Kinetics, EPR Spectroscopy, and DFT Calculations

    Science.gov (United States)

    Paderes, Monissa C.; Belding, Lee; Fanovic, Branden; Dudding, Travis; Keister, Jerome B.

    2012-01-01

    Alkene difunctionalization reactions are important in organic synthesis. We have recently shown that copper(II) complexes can promote and catalyze intramolecular alkene aminooxygenation, carboamination, and diamination reactions. In this contribution, we report a combined experimental and theoretical examination of the mechanism of the copper(II)-promoted olefin aminooxygenation reaction. Kinetics experiments revealed a mechanistic pathway involving an equilibrium reaction between a copper(II) carboxylate complex and the γ-alkenyl sulfonamide substrate and a rate-limiting intramolecular cis-addition of N–Cu across the olefin. Kinetic isotope effect studies support that the cis-aminocupration is the rate-determining step. UV/Vis spectra support a role for the base in the break-up of copper(II) carboxylate dimer to monomeric species. Electron paramagnetic resonance (EPR) spectra provide evidence for a kinetically competent N–Cu intermediate with a CuII oxidation state. Due to the highly similar stereochemical and reactivity trends among the CuII-promoted and catalyzed alkene difunctionalization reactions we have developed, the cis-aminocupration mechanism can reasonably be generalized across the reaction class. The methods and findings disclosed in this report should also prove valuable to the mechanism analysis and optimization of other copper(-II) carboxylate promoted reactions, especially those that take place in aprotic organic solvents. PMID:22237868

  1. Cooperative carbon-atom abstraction from alkenes in the core of a pentanuclear nickel cluster

    Science.gov (United States)

    Shoshani, Manar M.; Johnson, Samuel A.

    2017-12-01

    Although the cleavage of C-C bonds in unactivated hydrocarbons by soluble transition-metal complexes remains a challenge, such reactions hold the potential to provide access to previously inconceivable skeletal transformations. For instance, one can imagine the dismantling and reassembly of C-C and C-H bonds commonly observed in surface catalysis, but with the increased control innate to homogeneous catalysis. Here we report a pentanuclear nickel cluster that is unreactive to functional groups, such as alcohols, amines and even water, but selectively cleaves the C=C bonds of simple alkenes, such as ethylene, styrene and isobutylene, at temperatures as low as ‑30 °C and in near-quantitative yields. The isolation of intermediates in reactions with styrene and isobutylene demonstrates that the five nickel centres cooperatively activate three C-H bonds of the alkene substrate before cleaving the C-C bond in the core of the cluster to give a pentanuclear nickel carbide. The net organic product transformation is the abstraction of a carbon atom from an alkene.

  2. Degradation of trichloroethene by a linear-plasmid-encoded alkene monooxygenase in Rhodococcus corallinus (Nocardia corallina) B-276.

    Science.gov (United States)

    Saeki, H; Akira, M; Furuhashi, K; Averhoff, B; Gottschalk, G

    1999-07-01

    Rhodococcus corallinus (formerly Nocardia corallina) B-276, isolated with propene as sole carbon and energy source, is able to oxidize trichloroethene (TCE). Glucose- or propene-grown R. corallinus B-276 cells exhibited no difference in TCE degradation efficiency. TCE degradation was found to be growth-phase-dependent and maximum rates were monitored with stationary-phase cells. K(m) and Vmax values for TCE degradation of R. corallinus B-276 grown in nutrient broth medium in the presence of glucose were 187 microM and 2.4 nmol min-1 (mg protein)-1, respectively. Escherichia coli recombinants harbouring and expressing the alkene monooxygenase genes of R. corallinus B-276 exhibited the ability to degrade TCE. This result provides clear evidence that the alkene monooxygenase of R. corallinus B-276 catalyses TCE oxidation. R. corallinus B-276 was shown to contain four linear plasmids, pNC10 (70 kb), pNC20 (85 kb), pNC30 (185 kb) and pNC40 (235 kb). The observation that pNC30-deficient strains had lost the ability to grow on propene suggested that the genes of the propene degradation pathway are encoded by the linear plasmid pNC30. Southern blot analysis with cloned alkene monooxygenase genes from R. corallinus B-276 revealed a positive hybridization signal with the linear plasmid pNC30. This result clearly shows that the alkene monooxygenase is encoded by the linear plasmid pNC30. Eleven short-chain-alkene-oxidizing strains were screened for the presence of linear plasmids. Among these, four propene-oxidizing Rhodococcus strains and one ethene-oxidizing Mycobacterium strain were found to contain linear megaplasmids. Southern blot analysis with the alkene monooxygenase revealed positive signals with linear plasmids of two propene-oxidizing Rhodococcus ruber strains. These results indicate that homologous alkene monooxygenases are encoded by linear plasmids in R. ruber strains.

  3. Quartz Crystal Microbalance Analysis of Diels-Alder Reactions of Alkene Gases to Functional Ionic Liquids on Chips.

    Science.gov (United States)

    Hsu, Tzu-Hsuan; Chiang, Shu-Jen; Chu, Yen-Ho

    2016-11-15

    We demonstrated here a successful development of the use of functional ionic liquids FIL 1 and FIL 3 for chemoselective detection of alkene gases measured by quartz crystal microbalance. This detection of gaseous alkenes was achieved by the Diels-Alder [4 + 2] cycloadditions with FIL 1 and FIL 3 thin-coated on quartz chips. Our functional ionic liquids could be prepared by straightforward synthetic chemistry in short steps and are superior in alkene gas detection. The QCM platform developed in this work is chemoselective with fast gas diffusion into ionic liquids, readily applicable to low molecular weight alkene gases and insensitive to moisture. To the best of our knowledge, this is the first report based upon the Diels-Alder reactions demonstrating sensitive alkene gas detection in ionic liquids on a QCM. This work is a proof-of-concept inspection of the promising use of a QCM-based sensor method for reaction-directed detection of gas samples, which is part of an ongoing program aimed at studying diseases.

  4. In situ EPR studies of reaction pathways in Titania photocatalyst-promoted alkylation of alkenes.

    Science.gov (United States)

    Rhydderch, Shona; Howe, Russell F

    2015-03-03

    In situ EPR spectroscopy at cryogenic temperatures has been used to observe and identify paramagnetic species produced when titania is irradiated in the presence of reactants used in the photocatalytic alkylation of maleimide with t-butyl carboxylic acid or phenoxyacetic acid. It is shown that maleimide acts as an acceptor of conduction band electrons. Valence band holes oxidise t-butyl carboxylic acid to the t-butyl radical and phenoxyacetic acid to the phenoxyacetic acid radical cation. In the presence of maleimide, the phenoxymethyl radical is formed from phenoxyacetic acid. The relevance of these observations to the mechanisms of titania photocatalyst-promoted alkylation of alkenes is discussed.

  5. Palladium-Catalyzed Tandem Oxidative Arylation/Olefination of Aromatic Tethered Alkenes/Alkynes.

    Science.gov (United States)

    Gao, Yang; Gao, Yinglan; Wu, Wanqing; Jiang, Huanfeng; Yang, Xiaobo; Liu, Wenbo; Li, Chao-Jun

    2017-01-18

    We describe herein a palladium-catalyzed tandem oxidative arylation/olefination reaction of aromatic tethered alkenes/alkynes for the synthesis of dihydrobenzofurans and 2 H-chromene derivatives. This reaction features a 1,2-difunctionalization of C-C π-bond with two C-H bonds using O 2 as terminal oxidant at room temperature. The products obtained are valuable synthons and important scaffolds in biological agents and natural products. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Catalytic di-dehydroxylation of diols and carbohydrates to alkenes by (pentamethylcyclopentadienyl)/trioxorhenium(VII)

    Energy Technology Data Exchange (ETDEWEB)

    Cook, G.K.; Andrews, M.A. [Brookhaven National Laboratory, Upton, NY (United States)

    1996-10-01

    Oxygenated organics, which are traditionally prepared by the oxidation of petroleum-based feedstocks, are potentially accessible by the partial deoxygenation of renewable carbohydrate feedstocks. Towards this end, we have recently accomplished the catalytic di-dehydroxylation of both diols and polyols (including protected and unprotected sugars) to alkenes utilizing Cp {sup *}ReO{sub 3} in the presence of a suitable stoichiometric reductant such as triphenylphosphine. The reaction conditions, scope, effect of co-catalysts, and mechanism, including catalyst deactivation and regeneration, will be discussed.

  7. Cobalt-Mediated [3+2]-Annulation Reaction of Alkenes with α,β-Unsaturated Ketones and Imines

    Science.gov (United States)

    Schomaker, Jennifer M.; Toste, F. Dean; Bergman, Robert G.

    2009-01-01

    The utility of cobalt dinitrosyl complexes for the [3+2] annulation of alkenes with unsaturated enones and ketimines has been demonstrated. Reaction of a series of cobalt dinitrosyl/alkene adducts with conjugate acceptors in the presence of Sc(OTf)3/LHMDS formed two new C-C bonds at the carbons α to the nitrosyl groups of the substrate, leading to unusual tri- and tetracycles. Retrocycloaddition of these products in the presence of norbornadiene yielded functionalized tetrasubstituted bicyclic olefins. PMID:19639989

  8. Renewable Alkenes from the Hydrothermal Treatment of Polyhydroxyalkanoates-Containing Sludge.

    Science.gov (United States)

    Torri, Cristian; Weme, Tom Detert Oude; Samorì, Chiara; Kiwan, Alisar; Brilman, Derk W F

    2017-11-07

    Polyhydroxyalkanoates (PHA) are a key constituent of excess sludge produced by Aerobic Sewage Sludge Treatment plants. The accumulation of significant amount of PHA inside aerobic microbial cells occurs when a surplus of an easily degradable carbon source (e.g., volatile fatty acids, VFA) is found in combination with other nutrients limitation. Herein, hydrothermal treatment (HT) of PHA-containing sludge at 300 and 375 °C was demonstrated to be effective in converting most (>70% w/w) of the bacterial PHA stored inside microbial cells into alkene/CO 2 gas mixtures. Simultaneously, most of non-PHA biomass was converted into water-soluble compounds (50% carbon yield) that were acidogenic fermented to produce volatile fatty acids, ideal substrate to feed aerobic bacteria and produce more PHA. According to results here presented, HT of excess sludge with moderate (13%) PHA content can produce about 50 kg of alkenes per tonne of suspended solids treated, with a significant reduction of sludge mass (80% reduction of wet sludge volume) and consequent disposal cost.

  9. Electron transfer reactions in the alkene mono-oxygenase complex from Nocardia corallina B-276.

    Science.gov (United States)

    Gallagher, S C; Cammack, R; Dalton, H

    1999-04-01

    Nocardia corallina B-276 possesses a multi-component enzyme, alkene mono-oxygenase (AMO), that catalyses the stereoselective epoxygenation of alkenes. The reductase component of this system has been shown by EPR and fluorescence spectroscopy to contain two prosthetic groups, an FAD centre and a [2Fe-2S] cluster. The role of these centres in the epoxygenation reaction was determined by midpoint potential measurements and electron transfer kinetics. The order of potentials of the prosthetic groups of the reductase were FAD/FAD.=-216 mV, [2Fe-2S]/[2Fe-2S].=-160 mV and FAD./FAD.=-134 mV. Combined, these data implied that the reductase component supplied the energy required for the epoxygenation reaction and allowed a prediction of the mechanism of electron transfer within the AMO complex. The FAD moiety was reduced by bound NADH in a two-electron reaction. The electrons were then transported to the [2Fe-2S] centre one at a time, which in turn reduced the di-iron centre of the epoxygenase. Reduction of the di-iron centre is required for oxygen binding and substrate oxidation.

  10. Laboratory spectroscopic analyses of electron irradiated alkanes and alkenes in solar system ices

    Science.gov (United States)

    Hand, K. P.; Carlson, R. W.

    2012-03-01

    We report results from laboratory experiments of 10 keV electron irradiation of thin ice films of water and short-chain hydrocarbons at ˜10-8 Torr and temperatures ranging from 70-100 K. Hydrocarbon mixtures include water with C3H8, C3H6, C4H10 (butane and isobutane), and C4H8, (1-butene and cis/trans-2-butene). The double bonds of the alkenes in our initial mixtures were rapidly destroyed or converted to single carbon bonds, covalent bonds with hydrogen, bonds with -OH (hydroxyl), bonds with oxygen (C-O), or double bonds with oxygen (carbonyl). Spectra resulting from irradiation of alkane and alkene ices are largely indistinguishable; the initial differences in film composition are destroyed and the resulting mixture includes long-chain, branched aliphatics, aldehydes, ketones, esters, and alcohols. Methane was observed as a product during radiolysis but CO was largely absent. We find that while some of the carbon is oxidized and lost to CO2 formation, some carbon is sequestered into highly refractory, long-chain aliphatic compounds that remain as a thin residue even after the ice film has been raised to standard temperature and pressure. We conclude that the high availability of hydrogen in our experiments leads to the formation of the formyl radical which then serves as the precursor for formaldehyde and polymerization of longer hydrocarbon chains.

  11. The enol-variant of the hydroperoxide channel in alkene ozonolysis

    Science.gov (United States)

    Uherek, E.; Moortgat, G. K.

    2003-04-01

    Carboxylic acids, in particular dicarboxylic acids, belong to the product classes with lowest volatility in atmospheric oxidation and significantly contribute to aerosol formation. The mechanisms leading to carboxylic acids in the ozonolysis of alkenes have been investigated in laboratory experiments. The concentrations of symmetric alkenes have been varied in the range from 0.5 - 4 ppm (excess of ozone) in a 570 L smog chamber. The systematic tendencies leading to different yields for C(n) acids (2-5%) and C(n-1) acids (4-10%) formed from a Criegee Intermediate with n carbon atoms reveal that C(n) acids are formed via several pathways, partially as products of secondary chemistry. The formation of the C(n-1) acids however, which are not yet included in the established mechanisms, requires the introduction of a new mechanism. The acids are primary products and their formation can be explained by a variant of the hydroperoxide channel in ozonolysis. In this variant a keto-enol tautomery of a radical intermediate is followed by an allyl rearrangement. This step allows further oxidation of the beta-C-atom of the Criegee Intermediate and does not only explain the formation of C(n-1) acids in this systematic study but can also be an additional pathway to the dicarboxylic acids detected in terpene oxidation.

  12. DFT Rationalization of the Diverse Outcomes of the Iodine(III)-Mediated Oxidative Amination of Alkenes.

    Science.gov (United States)

    Funes-Ardoiz, Ignacio; Sameera, W M C; Romero, R Martín; Martínez, Claudio; Souto, José A; Sampedro, Diego; Muñiz, Kilian; Maseras, Feliu

    2016-05-23

    A computational study of the mechanism for the iodine(III)-mediated oxidative amination of alkenes explains the experimentally observed substrate dependence on product distribution. Calculations with the M06 functional have been carried out on the reaction between PhI(N(SO2 Me)2 )2 and three different representative substrates: styrene, α-methylstyrene, and (E)-methylstilbene. All reactions start with electrophilic attack by a cationic PhI(N(SO2 Me)2 )(+) unit on the double bond, and formation of an intermediate with a single C-I bond and a planar sp(2) carbocationic center. The major path, leading to 1,2-diamination, proceeds through a mechanism in which the bissulfonimide initially adds to the alkene through an oxygen atom of one sulfonyl group. This behavior is now corroborated by experimental evidence. An alternative path, leading to an allylic amination product, takes place through deprotonation at an allylic C-H position in the common intermediate. The regioselectivity of this amination depends on the availability of the resonant structures of an alternate carbocationic intermediate. Only in cases where a high electronic delocalization is possible, as in (E)-methylstilbene, does the allylic amination occur without migration of the double bond. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Mechanistic Links in the in-situ Formation of Dinuclear Manganese Catalysts, H2O2 Disproportionation, and Alkene Oxidation

    NARCIS (Netherlands)

    Angelone, Davide; Abdolahzadeh, Shaghayegh; de Boer, Johannes W.; Browne, Wesley R.

    The oxidation of substrates, such as alkenes, with H2O2 and the catalyst [Mn-2(IV)(mu-O)(3)(tmtacn)(2)](2+) (1; tmtacn = 1,4,7-tri-methyl-1,4,7-triazacyclononane) is promoted by the addition of carboxylic acids through the in situ formation of bis-(carboxylato) complexes of the type

  14. Chemistry of Volatile Organic Compounds in the Los Angeles basin: Nighttime Removal of Alkenes and Determination of Emission Ratios

    Science.gov (United States)

    de Gouw, J. A.; Gilman, J. B.; Kim, S.-W.; Lerner, B. M.; Isaacman-VanWertz, G.; McDonald, B. C.; Warneke, C.; Kuster, W. C.; Lefer, B. L.; Griffith, S. M.; Dusanter, S.; Stevens, P. S.; Stutz, J.

    2017-11-01

    We reanalyze a data set of hydrocarbons in ambient air obtained by gas chromatography-mass spectrometry at a surface site in Pasadena in the Los Angeles basin during the NOAA California Nexus study in 2010. The number of hydrocarbon compounds quantified from the chromatograms is expanded through the use of new peak-fitting data analysis software. We also reexamine hydrocarbon removal processes. For alkanes, small alkenes, and aromatics, the removal is determined by the reaction with hydroxyl (OH) radicals. For several highly reactive alkenes, the nighttime removal by ozone and nitrate (NO3) radicals is also significant. We discuss how this nighttime removal affects the determination of emission ratios versus carbon monoxide (CO) and show that previous estimates based on nighttime correlations with CO were too low. We analyze model output from the Weather Research and Forecasting-Chemistry model for hydrocarbons and radicals at the Pasadena location to evaluate our methods for determining emission ratios from the measurements. We find that our methods agree with the modeled emission ratios for the domain centered on Pasadena and that the modeled emission ratios vary by 23% across the wider South Coast basin. We compare the alkene emission ratios with published results from ambient measurements and from tunnel and dynamometer studies of motor vehicle emissions. We find that with few exceptions the composition of alkene emissions determined from the measurements in Pasadena closely resembles that of motor vehicle emissions.

  15. Palladium-catalysed transfer hydrogenation of alkenes in the presence of zinc powder and various organic acids

    Directory of Open Access Journals (Sweden)

    I.B. Masesane

    2005-06-01

    Full Text Available Catalytic transfer hydrogenation using palladium(II chloride, zinc powder and various organic acids proved effective for the reduction of a variety of alkenes at ambient temperature and atmospheric pressure. The method was found to be convenient, economical and uses a stable nonpyrophoric catalyst.

  16. Regioselective Hydration of an Alkene and Analysis of the Alcohol Product by Remote Access NMR: A Classroom Demonstration

    Science.gov (United States)

    Smith, Maureen E.; Johnson, Sara L.; Masterson, Douglas S.

    2013-01-01

    A two-part demonstration was conducted in our first-semester organic chemistry course designed to introduce students to the formation of alcohols, regioselective reactions, and analysis of organic products by NMR analysis. This demonstration utilized the oxymercuration-demercuration sequence to prepare an alcohol from an alkene in a Markovnikov…

  17. Tribology and Stability of Organic Monolayers on CrN: A Comparison among Silane, Phosphate, Alkene, and Alkyne Chemistries

    NARCIS (Netherlands)

    Pujari, S.P.; Li, F.; Regeling, R.; Zuilhof, H.

    2013-01-01

    The fabrication of chemically and mechanically stable monolayers on the surfaces of various inorganic hard materials is crucial to the development of biomedical/electronic devices. In this Article, monolayers based on the reactivity of silane, phosphonate, 1-alkene, and 1-alkyne moieties were

  18. Olefination of Electron-Deficient Alkenes with Allyl Acetate: Stereo- and Regioselective Access to (2Z,4E)-Dienamides.

    Science.gov (United States)

    Li, Feifei; Yu, Chunbing; Zhang, Jian; Zhong, Guofu

    2016-09-16

    A Ru-catalyzed direct olefination of electron-deficient alkenes with allyl acetate via C-H bond activation is disclosed. By using N,N-disubstituted aminocarbonyl as the directing group, this external oxidant-free protocol resulted in high reaction efficiency and good stereo- and regioselectivities, which opens a novel synthetic passway for access to (Z,E)-butadiene skeletons.

  19. Aldehyde-Selective Wacker-Type Oxidation of Unbiased Alkenes Enabled by a Nitrite Co-Catalyst

    KAUST Repository

    Wickens, Zachary K.

    2013-09-13

    Breaking the rules: Reversal of the high Markovnikov selectivity of Wacker-type oxidations was accomplished using a nitrite co-catalyst. Unbiased aliphatic alkenes can be oxidized with high yield and aldehyde selectivity, and several functional groups are tolerated. 18O-labeling experiments indicate that the aldehydic O atom is derived from the nitrite salt.

  20. Molybdenum-catalyzed conversion of diols and biomass-derived polyols to alkenes using isopropyl alcohol as reductant and solvent

    DEFF Research Database (Denmark)

    Dethlefsen, Johannes Rytter; Lupp, Daniel; Gorfo, Ayele Teshome

    2015-01-01

    in isopropyl alcohol (iPrOH), which serves as both the solvent and reductant. The reaction proceeds at 240-250 °C in a pressurized autoclave, and the alkene yield from simple aliphatic diols can be as high as 77%. The major byproducts are carbonyl compounds - formed by dehydration of the diol...

  1. Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

    Science.gov (United States)

    A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation and the reaction can be accomplished using vi...

  2. Products and Kinetics of the Reactions of an Alkane Monolayer and a Terminal Alkene Monolayer with NO₃ Radicals

    Energy Technology Data Exchange (ETDEWEB)

    Gross, Simone; Bertram, Allan K.

    2009-01-27

    The reactions of an alkanethiol and a terminal alkenethiol self-assembled monolayer with NO₃ radicals (in the presence of NO₂ and O₂) were studied. For the alkane monolayer, infrared (IR) spectroscopy and time-of-flight secondary ion mass spectrometry (ToF-SIMS) confirmed the formation of organonitrates (RONO₂). The observation of organonitrates is in contrast to the recent X-ray photoelectron spectroscopy (XPS) data, which showed very little nitrogen-containing surface species. The identification of organonitrates may help explain why significant volatilization of the organic chain was not observed in recent studies of alkane monolayer oxidation by NO₃ radicals. The reactive uptake coefficient (g) of NO₃ on alkene monolayers determined in our study is higher than the values obtained in a recent study using liquid and solid alkene bulk films. A possible reason for this difference may be the location of the double bond at the interface. Using the g value determined in our studies, we show that under conditions where NO₃ is high the lifetime of an alkene monolayer in the atmosphere may be short (approximately 20 min). XPS, IR, and ToF-SIMS were used to identify surface functional groups after the oxidation of the alkene monolayers by NO₃. The results are consistent with the formation of C-O, aldehyde/ketone, carboxylic groups, and nitrogen containing species.

  3. Photocatalytic E → Z Isomerization of Polarized Alkenes Inspired by the Visual Cycle: Mechanistic Dichotomy and Origin of Selectivity.

    Science.gov (United States)

    Metternich, Jan B; Artiukhin, Denis G; Holland, Mareike C; von Bremen-Kühne, Maximilian; Neugebauer, Johannes; Gilmour, Ryan

    2017-10-06

    Iteratively executed with exquisite spatial and temporal control, the selective isomerization of polarized alkenes underpins a plethora of complex biological processes ranging from natural product biosynthesis through to the mammalian visual cycle. However, nature's proficiency conceals the inherent difficulties in replicating this contra-thermodynamic transformation in the laboratory. Recently, we disclosed the first highly Z-selective isomerization of polarized alkenes, employing the cinnamoyl chromophore as a retinal surrogate under UV-irradiation (402 nm) with (-)-riboflavin (vitamin B 2 ) as an inexpensive, organic photocatalyst (J. Am. Chem. Soc. 2015, 137, 11254-11257). This study was inspired by the propensity of crystalline (-)-riboflavin in the eyes of vertebrates to invert the intrinsic directionality of retinal isomerization. Herein, we extend this methodology to include a bioinspired, catalytic E → Z isomerization of α,β-unsaturated nitriles, thereby mimicking the intermediate Opsin-derived, protonated Schiff base in the visual cycle with simple polarized alkenes. Replacement of the iminium motif by a cyano group is well tolerated and gives an additional degree of versatility for postisomerization functionalization. Broad substrate scope is demonstrated (up to 99:1 Z:E) together with evidence of mechanistic dichotomy via both singlet and triplet energy transfer mechanisms. Kinetic studies, temperature dependent photostationary state correlations and investigation of substituent-based electronic perturbation of the alkene identified polarization combined with increased Z-isomer activation barriers as the selectivity governing factors in catalysis. This investigation demonstrates the importance of internal structural preorganization on photostationary composition and explicates the augmented Z-selectivity upon hydrogen-alkyl exchange at the β-position of the alkene.

  4. Recommended Vapor-Liquid Equilibrium Data. Part 4. Binary Alkanol-Alkene/Alkyne Systems

    Science.gov (United States)

    Góral, Marian; Bok, Andrzej; Kasprzycka-Gutman, Teresa; Oracz, Paweł

    2006-12-01

    The recommended vapor-liquid equilibrium (VLE) data for binary mixtures of alkanols with alkenes and alkynes have been selected after critical evaluation of all data reported in the open literature up to the end of 2003. The evaluation procedure consisted in combining the thermodynamic consistency tests, data correlation, comparison with enthalpy of mixing data, and comparison of VLE data for various mixtures. The data were correlated with Wilson equation as well as with equation of state appended with chemical term (EoSC) proposed by Góral. The recommended data for 18 systems are presented in the form of individual pages containing tables of data, figures, and auxiliary information. Each page corresponds to one system and contains three isotherms (spaced by at least 15K) and one isobar (preferably at 101.32kPa). Experimental gaps were completed with the predicted data.

  5. Asymmetric silver-catalysed intermolecular bromotrifluoromethoxylation of alkenes with a new trifluoromethoxylation reagent

    Science.gov (United States)

    Guo, Shuo; Cong, Fei; Guo, Rui; Wang, Liang; Tang, Pingping

    2017-06-01

    Fluorinated organic compounds are becoming increasingly important in pharmaceuticals, agrochemicals and materials science. The introduction of trifluoromethoxy groups into new drugs and agrochemicals has attracted much attention due to their strongly electron-withdrawing nature and high lipophilicity. However, synthesis of trifluoromethoxylated organic molecules is difficult owing to the decomposition of trifluoromethoxide anion and β-fluoride elimination from transition-metal-trifluoromethoxide complexes, and no catalytic enantioselective trifluoromethoxylation reaction has been reported until now. Here, we present an example of an asymmetric silver-catalysed intermolecular bromotrifluoromethoxylation of alkenes with trifluoromethyl arylsulfonate (TFMS) as a new trifluoromethoxylation reagent. Compared to other trifluoromethoxylation reagents, TFMS is easily prepared and thermally stable with good reactivity. In addition, this reaction is operationally simple, scalable and proceeds under mild reaction conditions. Furthermore, broad scope and good functional group compatibility has been demonstrated by application of the method to the bromotrifluoromethoxylation of double bonds in natural products and natural product derivatives.

  6. Identification and quantification of alkene-based drilling fluids in crude oils by comprehensive two-dimensional gas chromatography with flame ionization detection.

    Science.gov (United States)

    Reddy, Christopher M; Nelson, Robert K; Sylva, Sean P; Xu, Li; Peacock, Emily A; Raghuraman, Bhavani; Mullins, Oliver C

    2007-04-27

    Comprehensive two-dimensional gas chromatography with flame ionization detection (GC x GC-FID) was used to measure alkene-based drilling fluids in crude oils. Compared to one-dimensional gas chromatography, GC x GC-FID is more robust for detecting alkenes due to the increased resolution afforded by second dimension separations. Using GC x GC-FID to analyze four oil samples from one reservoir contaminated with the same drilling fluid, C(15), C(16), C(17), C(18) and C(20) alkenes were identified. The drilling fluid that contaminated these samples also differed from another commercially obtained fluid, which only contained C(16) and C(18) alkenes. These results should motivate the petroleum industry to consider GC x GC-FID for measuring drilling fluids.

  7. Magnetic Fe@g??C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes

    Science.gov (United States)

    A photoactive catalyst, Fe@g-C3N4, has been developed for the hydrogenation of alkenes and alkynes using hydrazine hydrate as a source of hydrogen. The magnetically separable Fe@g-C3N4 eliminates the use of high pressure hydrogenation, and the reaction can be accomplished using visible light without the need for external sources of energy.This dataset is associated with the following publication:Baig, N., S. Verma, R. Varma , and M. Nadagouda. Magnetic Fe@g-C3N4: A Photoactive Catalyst for the Hydrogenation of Alkenes and Alkynes. ACS Sustainable Chemistry & Engineering. American Chemical Society, Washington, DC, USA, 4(3): 1661-1664, (2016).

  8. Rapid Access to β-Trifluoromethyl-Substituted Ketones: Harnessing Inductive Effects in Wacker-Type Oxidations of Internal Alkenes

    KAUST Repository

    Lerch, Michael M.

    2014-07-18

    We present a practical trifluoromethyl-directed Wacker-type oxidation of internal alkenes that enables rapid access to β-trifluoromethyl-substituted ketones. Allylic trifluoromethyl-substituted alkenes bearing a wide range of functional groups can be oxidized in high yield and regioselectivity. The distance dependence of the regioselectivity was established by systematic variation of the number of methylene units between the double bond and the trifluoromethyl group. The regioselectivity enforced by traditional directing groups could even be reversed by introduction of a competing trifluoromethyl group. Besides being a new powerful synthetic method to prepare fluorinated molecules, this work directly probes the role of inductive effects on nucleopalladation events. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. Rhenium oxide supported on organized mesoporous alumina - A highly active and versatile catalyst for alkene, diene, and cycloalkene metathesis

    Czech Academy of Sciences Publication Activity Database

    Hamtil, Roman; Žilková, Naděžda; Balcar, Hynek; Čejka, Jiří

    2006-01-01

    Roč. 302, č. 2 (2006), s. 193-200 ISSN 0926-860X R&D Projects: GA AV ČR IAA4040411; GA MPO FT-TA/042 Institutional research plan: CEZ:AV0Z40400503 Keywords : organized mesoporous alumina * rhenium oxide * alkene metathesis * ring-opening metathesis polzmerization Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.630, year: 2006

  10. Iodine-Catalyzed Direct Olefination of 2-Oxindoles and Alkenes via Cross-Dehydrogenative Coupling (CDC) in Air.

    Science.gov (United States)

    Huang, Hong-Yan; Wu, Hong-Ru; Wei, Feng; Wang, Dong; Liu, Li

    2015-08-07

    A direct intermolecular olefination of sp(3) C-H bond between 2-oxindoles and simple alkenes via a Cross-Dehydrogenative Coupling (CDC) strategy has been developed. In the absence of additional base, moderate to excellent yields have been obtained by using a catalytic amount of iodine with atmospheric oxygen as the reoxidant. Based on the observation of a radical capture experiment, the transformation is proposed to proceed via a radical process.

  11. Borata-Wittig olefination reactions of ketones, carboxylic esters and amides with bis(pentafluorophenyl)borata-alkene reagents.

    Science.gov (United States)

    Wang, Tongdao; Kohrt, Sonja; Daniliuc, Constantin G; Kehr, Gerald; Erker, Gerhard

    2017-08-07

    The strongly electrophilic borane derivative amino-CH 2 CH 2 CH 2 -B(C 6 F 5 ) 2 6 was α-CH deprotonated with LiTMP to give the borata-alkene {[amino-(CH 2 ) 2 -CH[double bond, length as m-dash]B(C 6 F 5 ) 2 - ][Li + ]} 2 9 which underwent facile [2 + 2] cycloaddition reactions with benzophenone or fluorenone to yield the respective 1,2-oxaboretanides 11a,b. Compounds 9 and 11 were characterized by the X-ray diffraction. Thermolysis or hydrolysis of compounds 11a,b gave the corresponding borata-Wittig olefination products 12a,b. A variety of R-CH 2 -CH 2 -B(C 6 F 5 ) 2 boranes (conveniently generated by hydroboration of terminal alkenes R-CH[double bond, length as m-dash]CH 2 with Piers' borane [HB(C 6 F 5 ) 2 ]) were analogously deprotonated to give the respective borata-alkenes 16a-e (R: Ph-CH 2 -, n C 4 H 9 , t Bu, Cy, PhCH 2 CH 2 -). They underwent "non-classical" borata-Wittig olefination reactions with ethylformate to give the respective enolether carbonylation products, or their C 1 -elongated aldehydes (after hydrolysis). The borata-alkene [Ph-(CH 2 ) 2 -CH[double bond, length as m-dash]B(C 6 F 5 ) 2 - ] [Li + HTMP] (16a) gave the respective "non-classical" borata-Wittig olefination products, the enolethers 25a,b and 27, respectively, upon treatment with methyl- or ethyl acetate or γ-butyrolactone.

  12. Intermolecular sulfenoamination of alkenes with sulfonamides and N-sulfanylsuccinimides to access β-sulfonylamino sulfides and dihydrobenzothiazines.

    Science.gov (United States)

    Liu, Tao; Tian, Jun; Gao, Wen-Chao; Chang, Hong-Hong; Liu, Qiang; Li, Xing; Wei, Wen-Long

    2017-07-19

    An acid-catalyzed intermolecular sulfenoamination reaction of alkenes is developed with sulfonamides as the nitrogen source and N-sulfanylsuccinimides as the sulfur source. This methodology provides a straightforward and general way to synthesize various β-sulfonylamino sulfides with high regio- and diastereoselectivity. The developed method was coupled with intramolecular C-N coupling in a one-pot procedure to afford a series of dihydrobenzothiazine derivatives, a kind of important heterocycle used as biologically active compounds in medicinal chemistry.

  13. Metal-catalyzed hydrosilylation of alkenes and alkynes using dimethyl(pyridyl)silane.

    Science.gov (United States)

    Itami, Kenichiro; Mitsudo, Koichi; Nishino, Akira; Yoshida, Jun-ichi

    2002-04-19

    Metal-catalyzed hydrosilylation of alkenes and alkynes using dimethyl(pyridyl)silane is described. The hydrosilylation of alkenes using dimethyl(2-pyridyl)silane (2-PyMe(2)SiH) proceeded well in the presence of a catalytic amount of RhCl(PPh(3))(3) with virtually complete regioselectivity. By taking advantage of the phase tag property of the 2-PyMe(2)Si group, hydrosilylation products were isolated in greater than 95% purity by simple acid-base extraction. Strategic catalyst recovery was also demonstrated. The hydrosilylation of alkynes using 2-PyMe(2)SiH proceeded with a Pt(CH(2)=CHSiMe(2))(2)O/P(t-Bu)(3) catalyst to give alkenyldimethyl(2-pyridyl)silanes in good yield with high regioselectivity. A reactivity comparison of 2-PyMe(2)SiH with other related hydrosilanes (3-PyMe(2)SiH, 4-PyMe(2)SiH, and PhMe(2)SiH) was also performed. In the rhodium-catalyzed reaction, the reactivity order of hydrosilane was 2-PyMe(2)SiH > 3-PyMe(2)SiH, 4-PyMe(2)SiH, PhMe(2)SiH, indicating a huge rate acceleration with 2-PyMe(2)SiH. In the platinum-catalyzed reaction, the reactivity order of hydrosilane was PhMe(2)SiH, 3-PyMe(2)SiH > 4-PyMe(2)SiH > 2-PyMe(2)SiH, indicating a rate deceleration with 2-PyMe(2)SiH and 4-PyMe(2)SiH. It seems that these reactivity differences stem primarily from the governance of two different mechanisms (Chalk-Harrod and modified Chalk-Harrod mechanisms). From the observed reactivity order, coordination and electronic effects of dimethyl(pyridyl)silanes have been implicated.

  14. Cobalt-Catalyzed [2π + 2π] Cycloadditions of Alkenes: Scope, Mechanism, and Elucidation of Electronic Structure of Catalytic Intermediates

    Science.gov (United States)

    2015-01-01

    Aryl-substituted bis(imino)pyridine cobalt dinitrogen compounds, (RPDI)CoN2, are effective precatalysts for the intramolecular [2π + 2π] cycloaddition of α,ω-dienes to yield the corresponding bicyclo[3.2.0]heptane derivatives. The reactions proceed under mild thermal conditions with unactivated alkenes, tolerating both amine and ether functional groups. The overall second order rate law for the reaction, first order with respect to both the cobalt precatalyst and the substrate, in combination with electron paramagnetic resonance (EPR) spectroscopic studies established the catalyst resting state as dependent on the identity of the precatalyst and diene substrate. Planar S =1/2 κ3-bis(imino)pyridine cobalt alkene and tetrahedral κ2-bis(imino)pyridine cobalt diene complexes were observed by EPR spectroscopy and in the latter case structurally characterized. The hemilabile chelate facilitates conversion of a principally ligand-based singly occupied molecular orbital (SOMO) in the cobalt dinitrogen and alkene compounds to a metal-based SOMO in the diene intermediates, promoting C–C bond-forming oxidative cyclization. Structure–activity relationships on bis(imino)pyridine substitution were also established with 2,4,6-tricyclopentyl-substituted aryl groups, resulting in optimized catalytic [2π + 2π] cycloaddition. The cyclopentyl groups provide a sufficiently open metal coordination sphere that encourages substrate coordination while remaining large enough to promote a challenging, turnover-limiting C(sp3)–C(sp3) reductive elimination. PMID:26030841

  15. Defensive roles of (E)-2-alkenals and related compounds in heteroptera.

    Science.gov (United States)

    Noge, Koji; Prudic, Kathleen L; Becerra, Judith X

    2012-08-01

    We examined whether shared volatiles found in various heteropteran species and developmental stages function to repel predators. The nymphal dorsal abdominal gland secretions of Riptortus pedestris (Heteroptera: Alydidae) and Thasus acutangulus (Heteroptera: Coreidae), and the metathoracic scent gland secretion of Euschistus biformis (Heteroptera: Pentatomidae) adults were identified by gas chromatography/mass spectrometry (GC/MS). (E)-2-Hexenal, 4-oxo-(E)-2-hexenal (4-OHE), and (E)-2-octenal were found in all three species and deemed likely candidates for repelling predators. In addition to (E)-2-alkenals, the adult E. biformis secreted (E)-2-hexenyl acetate, (E)-2-octenyl acetate, and four hydrocarbons. We evaluated the potential predator repellent properties of these compounds and compound blends against a generalist, cosmopolitan insect predator, the Chinese praying mantid (Mantodea: Mantidae: Tenodera aridifolia sinensis). Mantids that experienced (E)-2-hexenal, (E)-2-octenal, and (E)-2-octenyl acetate moved away from the site of interaction, while 4-OHE and (E)-2-hexenyl acetate did not affect mantid behavior. The compound blends did not have additive or synergistic repellency effects on predator behavior. Compound repellency was not related to compound volatility. Instead, the repellent effect is likely related to predator olfaction, and the affinity of each compound to receptors on the antennae. Our results also suggest the repellents might intensify the visual defensive signals of aposematism (T. acutangulus nymphs) and mimicry (R. pedestris nymphs) in heteropteran bugs.

  16. Clean and Selective Catalytic C-H alkylation of Alkenes with Environmental friendly Alcohols

    KAUST Repository

    Poater, Albert

    2016-09-14

    Bearing the alkylation of alkene substrates using alcohol as solvent, catalysed by the cationic Ru-based catalyst [(C6H6)(PCy3)(CO)RuH]+, DFT calculations have been carried out to get mechanistic insights of such an environmental friendly reaction. Hard experimental conditions of Yi and coworkers [Science2011, 333, 1613] allow the formation of a C-C bond between indene and ethanol. The predicted mechanism suggests a cationic Ru-alkenyl species once two equivalents of indene interact releasing a molecule of indane subproduct. Then, oxidative addition of the Csingle bondO bond of alcohol to Ru-alkenyl species leads to Ru-alkenyl-alkyl species, followed by the reductive elimination process produces the desired alkylation product and a Ru-hydroxo complex. Finally, vinylic Csingle bondH activation and water elimination regenerates the Ru-alkenyl species. In this paper we present a full description of the complete reaction pathway along with possible alternative pathways, which are predicted to display higher upper barriers. Furthermore, the present study explains the possible reasons for the absence of undesired products such as indene dimer or hydroxylated indene in the experiments.

  17. Polymethoxy-1-alkenes from Aphanizomenon ovalisporum Inhibit Vertebrate Development in the Zebrafish (Danio rerio Embryo Model

    Directory of Open Access Journals (Sweden)

    John P. Berry

    2012-10-01

    Full Text Available Cyanobacteria are recognized producers of a wide array of toxic or otherwise bioactive secondary metabolites. The present study utilized the zebrafish (Danio rerio embryo as an aquatic animal model of vertebrate development to identify, purify and characterize lipophilic inhibitors of development (i.e., developmental toxins from an isolate of the freshwater cyanobacterial species, Aphanizomenon ovalisporum. Bioassay-guided fractionation led to the purification, and subsequent chemical characterization, of an apparent homologous series of isotactic polymethoxy-1-alkenes (1–6, including three congeners (4–6 previously identified from the strain, and two variants previously identified from other species (2 and 3, as well as one apparently novel member of the series (1. Five of the PMAs in the series (1–5 were purified in sufficient quantity for comparative toxicological characterization, and toxicity in the zebrafish embryo model was found to generally correlate with relative chain length and/or methoxylation. Moreover, exposure of embryos to a combination of variants indicates an apparent synergistic interaction between the congeners. Although PMAs have been identified previously in cyanobacteria, this is the first report of their apparent toxicity. These results, along with the previously reported presence of the PMAs from several cyanobacterial species, suggest a possibly widespread distribution of the PMAs as toxic secondary metabolites and warrants further chemical and toxicological investigation.

  18. Product Control in Alkene Trifluoromethylation: Hydrotrifluoromethylation, Vinylic Trifluoromethylation, and Iodotrifluoromethylation using Togni Reagent.

    Science.gov (United States)

    Egami, Hiromichi; Usui, Yoshihiko; Kawamura, Shintaro; Nagashima, Sayoko; Sodeoka, Mikiko

    2015-10-01

    Hydrotrifluoromethylation, vinylic trifluoromethylation, and iodotrifluoromethylation of simple alkenes have been achieved by using Togni reagent in the absence of any transition metal catalyst. These reactions were readily controllable by selection of appropriate salts and solvents. The addition of K2CO3 afforded the hydrotrifluoromethylation product, with DMF acting not only as a solvent, but also as the hydrogen source. In contrast, the use of tetra-n-butylammonium iodide (TBAI) in 1,4-dioxane resulted in vinylic trifluoromethylation, while the use of KI afforded the iodotrifluoromethylation product. The vinylic trifluoromethylation product was obtained by treatment of the iodotrifluoromethylation product with ammonium 2-iodobenzoate, indicating that it was formed through an elimination reaction of the in-situ-generated iodotrifluoromethylation product, and the solubility of the resulting 2-iodobenzoate salt plays a key role in the product switching. A radical-clock experiment showed that these reactions proceed via radical intermediates. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.

  19. Is H Atom Abstraction Important in the Reaction of Cl with 1-Alkenes?

    Science.gov (United States)

    Walavalkar, M P; Vijayakumar, S; Sharma, A; Rajakumar, B; Dhanya, S

    2016-06-23

    The relative yields of products of the reaction of Cl atoms with 1-alkenes (C4-C9) were determined to see whether H atom abstraction is an important channel and if it is to identify the preferred position of abstraction. The presence of all the possible positional isomers of long chain alkenones and alkenols among the products, along with chloroketones and chloroalcohols, confirms the occurrence of H atom abstraction. A consistent pattern of distribution of abstraction products is observed with oxidation at C4 (next to allyl) being the lowest and that at CH2 groups away from the double bond being the highest. This contradicts with the higher stability of allyl (C3) radical. For a better understanding of the relative reactivity, ab initio calculations at MP2/6-311+G (d,p) level of theory are carried out in the case of 1-heptene. The total rate coefficient, calculated using conventional transition state theory, was found to be in good agreement with the experimental value at room temperature. The preferred position of Cl atom addition is predicted to be the terminal carbon atom, which matches with the experimental observation, whereas the rate coefficients calculated for individual channels of H atom abstraction do not explain the observed pattern of products. The distribution of abstraction products except at C4 is found to be better explained by reported structure activity relationship, developed from experimental rate coefficient data. This implies the reactions to be kinetically dictated and emphasizes the importance of secondary reactions.

  20. Terminal Alkene Formation by the Thioesterase of Curacin A Biosynthesis: Structure of a Decarboxylating Thioesterase

    Energy Technology Data Exchange (ETDEWEB)

    Gehret, Jennifer J.; Gu, Liangcai; Gerwick, William H.; Wipf, Peter; Sherman, David H.; Smith, Janet L. (Pitt); (Michigan); (UCSD)

    2011-11-07

    Curacin A is a polyketide synthase (PKS)-non-ribosomal peptide synthetase-derived natural product with potent anticancer properties generated by the marine cyanobacterium Lyngbya majuscula. Type I modular PKS assembly lines typically employ a thioesterase (TE) domain to off-load carboxylic acid or macrolactone products from an adjacent acyl carrier protein (ACP) domain. In a striking departure from this scheme the curacin A PKS employs tandem sulfotransferase and TE domains to form a terminal alkene moiety. Sulfotransferase sulfonation of {beta}-hydroxy-acyl-ACP is followed by TE hydrolysis, decarboxylation, and sulfate elimination (Gu, L., Wang, B., Kulkarni, A., Gehret, J. J., Lloyd, K. R., Gerwick, L., Gerwick, W. H., Wipf, P., Hakansson, K., Smith, J. L., and Sherman, D. H. (2009) J. Am. Chem. Soc. 131, 16033-16035). With low sequence identity to other PKS TEs (<15%), the curacin TE represents a new thioesterase subfamily. The 1.7-{angstrom} curacin TE crystal structure reveals how the familiar {alpha}/{beta}-hydrolase architecture is adapted to specificity for {beta}-sulfated substrates. A Ser-His-Glu catalytic triad is centered in an open active site cleft between the core domain and a lid subdomain. Unlike TEs from other PKSs, the lid is fixed in an open conformation on one side by dimer contacts of a protruding helix and on the other side by an arginine anchor from the lid into the core. Adjacent to the catalytic triad, another arginine residue is positioned to recognize the substrate {beta}-sulfate group. The essential features of the curacin TE are conserved in sequences of five other putative bacterial ACP-ST-TE tridomains. Formation of a sulfate leaving group as a biosynthetic strategy to facilitate acyl chain decarboxylation is of potential value as a route to hydrocarbon biofuels.

  1. Homochiral nickel coordination polymers based on salen(Ni) metalloligands: synthesis, structure, and catalytic alkene epoxidation.

    Science.gov (United States)

    Huang, Yuanbiao; Liu, Tianfu; Lin, Jingxiang; Lü, Jian; Lin, Zujin; Cao, Rong

    2011-03-21

    One-dimensional (1D) homochiral nickel coordination polymers [Ni(3)(bpdc)(RR-L)(2)·(DMF)](n) (2R, RR-L = (R,R)-(-)-1,2-cyclohexanediamino-N,N'-bis(3-tert-butyl-5-(4-pyridyl)salicylidene), bpdc = 4,4'-biphenyldicarboxylic acid) and [Ni(3)(bpdc)(SS-L)(2)·(DMF)](n) (2S, SS-L = (S,S)-(-)-1,2-cyclohexanediamino-N,N'-bis(3-tert-butyl-5-(4-pyridyl)salicylidene) based on enantiopure pyridyl-functionalized salen(Ni) metalloligand units NiL ((1,2-cyclohexanediamino-N,N'-bis(3-tert-butyl-5-(4-pyridyl)salicylidene))Ni(II)) have been synthesized and characterized by microanalysis, IR spectroscopy, solid-state UV-vis spectroscopy, thermogravimetric analysis (TGA), circular dichroism (CD) spectroscopy, cyclic voltammetric measurement, and powder and single crystal X-ray diffraction. Each NiL as unbridging pendant metalloligand uses one terminal pyridyl group to coordinate achiral unit (nickel and bpdc(2-)) building a helical chain, while the other pyridyl group remains uncoordinated. Both 2R and 2S contain left- and right-handed helical chains made of the achiral building blocks, while the NiL as remote external chiral source is perpendicular to the backbone of the helices. The nickel coordination polymers 2R and 2S containing unsaturated active nickel center in metalloligand NiL can be used as self-supported heterogeneous catalysts. They show catalytic activity comparable with their homogeneous counterpart in alkene epoxidation and exhibit great potential as recyclable catalysts.

  2. Ring-size-selective construction of fluorine-containing carbocycles via intramolecular iodoarylation of 1,1-difluoro-1-alkenes

    Directory of Open Access Journals (Sweden)

    Takeshi Fujita

    2017-12-01

    Full Text Available 1,1-Difluoro-1-alkenes bearing a biaryl-2-yl group effectively underwent site-selective intramolecular iodoarylation by the appropriate cationic iodine species. Iodoarylation of 2-(2-aryl-3,3-difluoroallylbiaryls proceeded via regioselective carbon–carbon bond formation at the carbon atoms in β-position to the fluorine substituents, thereby constructing dibenzo-fused six-membered carbocycles bearing a difluoroiodomethyl group. In contrast, 2-(3,3-difluoroallylbiaryls underwent a similar cyclization at the α-carbon atoms to afford ring-difluorinated seven-membered carbocycles.

  3. Room Temperature Activation of Aryloxysulfonyl Azides by [Co(II)(TPP)] for Selective Radical Aziridination of Alkenes via Metalloradical Catalysis.

    Science.gov (United States)

    Subbarayan, Velusamy; Jin, Li-Mei; Xin, Cui; Zhang, X Peter

    2015-06-03

    Aryloxysulfonyl azides can be effectively activated by commercially available cobalt(II) complex of meso -tetraphenylporphyrin ([Co(TPP)]) at room temperature under neutral and nonoxidative conditions for selective radical aziridination of alkenes via metalloradical catalysis. The [Co(TPP)]-catalyzed radical aziridination system is suitable for different combinations of olefin substrates and aryloxysulfonyl azides, producing various N -aryloxysulfonyl aziridine derivatives in good to excellent yields. In addition to generating the environmentally benign N 2 as the only byproduct, this Co(II)-based metalloradical aziridination process features mild reaction conditions and operational simplicity.

  4. An inexpensive and recyclable silver-foil catalyst for the cyclopropanation of alkenes with diazoacetates under mechanochemical conditions.

    Science.gov (United States)

    Chen, Longrui; Bovee, Mark O; Lemma, Betsegaw E; Keithley, Kimberlee S M; Pilson, Sara L; Coleman, Michael G; Mack, James

    2015-09-14

    The diastereoselective cyclopropanation of various alkenes with diazoacetate derivatives can be achieved under mechanochemical conditions using metallic silver foil and a stainless-steel vial and ball system. This solvent-free method displays analogous reactivity and selectivity to solution-phase reactions without the need for slow diazoacetate addition or an inert atmosphere. The heterogeneous silver-foil catalyst system is easily recyclable without any appreciable loss of activity or selectivity being observed. The cyclopropanation products were obtained with excellent diastereoselectivities (up to 98:2 d.r.) and in high yields (up to 96 %). © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Scope and limitations of chiral bis(oxazoline) ligands in the copper-catalysed asymmetric cyclopropanation of trisubstituted alkenes

    DEFF Research Database (Denmark)

    Østergaard, N.; Jensen, Jakob Feldthusen; Tanner, David Ackland

    2001-01-01

    A series of derivatives of 3-methyl-2-buten-1-ol has been used to test the scope and limitations of the copper-catalysed asymmetric cyclopropanation of trisubstituted alkenes by ethyl diazoacetate in the presence of C-2-symmetric bis(oxazoline) ligands. In the best case, a trans/cis ratio of 91......:9, with 92% ee for the major isomer, was obtained from the reaction of the p-methoxybenzoate derivative. The highest ee was 95%, for the trans isomer of a 80:20 diastereomer mixture (acetate derivative)....

  6. Tandem hydroformylation/hydrogenation of alkenes to normal alcohols using Rh/Ru dual catalyst or Ru single component catalyst.

    Science.gov (United States)

    Takahashi, Kohei; Yamashita, Makoto; Nozaki, Kyoko

    2012-11-14

    The catalyst system for tandem hydroformylation/hydrogenation of terminal alkenes to the corresponding homologated normal alcohol was developed. The reaction mechanism for the Rh/Ru dual catalyst was investigated by real-time IR monitoring experiments and (31)P NMR spectroscopy, which proved the mutual orthogonality of Rh-catalyzed hydroformylation and Ru-catalyzed hydrogenation. Detailed investigation about Ru-catalyzed hydrogenation of undecanal under H(2)/CO pressure clarified different kinetics from the hydrogenation under H(2) and gave a clue to design more active hydrogenation catalysts under H(2)/CO atmosphere. The solely Ru-catalyzed normal selective hydroformylation/hydrogenation is also reported.

  7. Intermolecular Anti-Markovnikov Hydroamination of Unactivated Alkenes with Sulfonamides Enabled by Proton-Coupled Electron Transfer.

    Science.gov (United States)

    Zhu, Qilei; Graff, David E; Knowles, Robert R

    2018-01-17

    Here we report a catalytic method for the intermolecular anti-Markovnikov hydroamination of unactivated alkenes using primary and secondary sulfonamides. These reactions occur at room temperature under visible light irradiation and are jointly catalyzed by an iridium(III) photocatalyst, a dialkyl phosphate base, and a thiol hydrogen atom donor. Reaction outcomes are consistent with the intermediacy of an N-centered sulfonamidyl radical generated via proton-coupled electron transfer activation of the sulfonamide N-H bond. Studies outlining the synthetic scope (>60 examples) and mechanistic features of the reaction are presented.

  8. Co(I)-Catalyzed [3 + 2] Annulation of o-Haloaryl Imines with Alkenes for the Synthesis of Indanamines.

    Science.gov (United States)

    Paul, Jérôme; Luong Van My, Lisa; Behar-Pirès, Myriam; Guillaume, Coralie; Léonel, Eric; Presset, Marc; Le Gall, Erwan

    2018-03-26

    The use of a CoBr 2 /1,10-phenanthroline catalytic system together with Zn as the reductant was developed to prepare diversely substituted indanamines by a Co(I)-catalyzed [3 + 2] annulation of o-haloaryl imines with electron-deficient alkenes in good yields. The use of Mn as the reductant allowed the elaboration of a three-component version of this reaction. These conditions were also found to be suitable for the activation of various halides and were extended to the preparation of the indenamine and strigolactam scaffolds.

  9. Oxidative Olefination of Anilides with Unactivated Alkenes Catalyzed by an (Electron-Deficient η(5) -Cyclopentadienyl)Rhodium(III) Complex Under Ambient Conditions.

    Science.gov (United States)

    Takahama, Yuji; Shibata, Yu; Tanaka, Ken

    2015-06-15

    The oxidative olefination of sp(2) C-H bonds of anilides with both activated and unactivated alkenes using an (electron-deficient η(5) -cyclopentadienyl)rhodium(III) complex is reported. In contrast to reactions using this electron-deficient rhodium(III) catalyst, [Cp*RhCl2 ]2 showed no activity against olefination with unactivated alkenes. In addition, the deuterium kinetic isotope effect (DKIE) study revealed that the C-H bond cleavage step is thought to be the turnover-limiting step. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Sequence-alignment modelling and molecular docking studies of the epoxygenase component of alkene monooxygenase from Nocardia corallina B-276.

    Science.gov (United States)

    Gallagher, S C; George, A; Dalton, H

    1998-06-15

    Whole cells of Nocardia corallina B-276 catalyse the stereoselective epoxygenation of alkenes to chiral epoxides. The bacterium expresses an enzyme, alkene monooxygenase, which catalyses the epoxygenation reaction stereoselectively. The enzyme consists of a terminal oxygenase (epoxygenase), an NADH-dependent reductase (reductase) and a regulatory component (coupling protein). The epoxygenase component contains a bridged diiron centre similar to that found in the hydroxylase component of soluble methane monooxygenase. Sequence-alignment modelling, supported by chemical modification and fluorescence probing, identified a hydrophobic oxygen/substrate binding site within the epoxygenase. The diiron centre was coordinated by the two His and two Glu residues from two conserved Glu-Xaa-Xaa-His sequences and by two further Glu residues. Molecular docking of substrates and products into the proposed active-site model of the epoxygenase suggested that Ala91 and Ala185 were responsible for the stereoselectivity exerted by AMO. It is proposed that these residues clamped the intermediate and/or product of the reaction, thereby controlling the configuration of the epoxide produced. In soluble methane monooxygenase these residues are replaced by two Gly residues which do not provide sufficient steric hindrance to prevent rotation of the intermediate in the active site and, therefore, the product of the reaction catalysed by this enzyme is achiral.

  11. Mechanism and Regioselectivity of Rh(III)-Catalyzed Intermolecular Annulation of Aryl-Substituted Diazenecarboxylates and Alkenes: DFT Insights

    KAUST Repository

    Ajitha, Manjaly John

    2016-02-05

    The mechanism of Rh-catalyzed intermolecular annulation of aryl-substituted diazenecarboxylates and alkenes was investigated using density functional theory (DFT) (PCM-M062X/6-311+G(d,p)//M062X/6-31G(d)). The acetate ligand (OAc)-assisted C-H activation via the formation of a five-membered rhodacycle (I-TS1; ΔG‡ = 19.4 kcal/mol) is more favorable compared to that via a four-membered intermediate (II-TS1; ΔG‡ = 27.8 kcal/mol). Our results also revealed that the seven-membered intermediate (I-3, ΔGrel = -6.8 kcal/mol) formed after the alkene insertion could undergo a coordination switch with the adjacent nitrogen atom (via TScs; ΔG‡ = 16.5 kcal/mol) to produce a thermodynamically stable six-membered intermediate (II-3, ΔGrel = -10.4 kcal/mol), eventually leading to a cyclization process followed by a barrierless ligand-assisted protonation to yield the final product. The β-hydride elimination product was found to be kinetically and thermodynamically undesirable. The rate-determining step is identified as the initial C-H activation, consistent with the previous kinetic studies. Notably, DFT studies offered important insights on the ability of the substrate (diazene carboxylate) to promote the switchable coordination site selectivity during the reaction to achieve a lower energy pathway. © 2016 American Chemical Society.

  12. Intramolecular Schmidt reaction of acyl chlorides with alkyl azides: preparation of pyrrolizine by intramolecular capture of intermediates with alkenes or alkynes.

    Science.gov (United States)

    Wang, Bao-Juan; Xue, Ping; Gu, Peiming

    2015-02-11

    The preparation of substituted pyrrolizines through the Schmidt reaction of acyl chlorides with alkyl azides has been realized. Intramolecular capture of the isocyanate ion and N-acyliminium ion intermediates from the Schmidt process with alkene or alkyne units was achieved, and the efficiency of the conversion with respect to ring construction and bond formation was demonstrated.

  13. Examination of the structure-toxicity relationships of L-cysteine-S-conjugates of halogenated alkenes and their corresponding mercapturic acids in rat renal tissue slices.

    NARCIS (Netherlands)

    Stijntjes, G.J.; Commandeur, J.N.M.; te Koppele, J.M.; McGuinness, S; Gandolfi, A.J.; Vermeulen, N.P.E.

    1993-01-01

    Rat kidney slices were produced using a modified version of a mechanical tissue slicer. The slices were incubated with various concentrations of l-cysteine conjugates and mercapturic acids of halogenated alkenes in a submersion incubation system. The slices showed a time- and concentration-dependent

  14. Mechanism of Alkene, Alkane, and Alcohol Oxidation with H2O2 by an in Situ Prepared Mn-II/Pyridine-2-carboxylic Acid Catalyst

    NARCIS (Netherlands)

    Saisaha, Pattama; Dong, Jia Jia; Meinds, Tim G.; de Boer, Johannes W.; Hage, Ronald; Mecozzi, Francesco; Kasper, Johann B.; Browne, Wesley R.

    The oxidation of alkenes, alkanes, and alcohols with H2O2 is catalyzed efficiently using an in situ prepared catalyst comprised of a MnII salt and pyridine-2-carboxylic acid (PCA) together with a ketone in a wide range of solvents. The mechanism by which these reactions proceed is elucidated, with a

  15. An Efficient Synthesis of Substituted Furans by Cupric Halide-Mediated Intramolecular Halocyclization of 2-(1-Alkynyl)-2-alken-1-ones

    International Nuclear Information System (INIS)

    Fu, Weijun; Guo, Wenbo; Zhu, Mei; Xu, Chen; Xu, Fengjuan

    2013-01-01

    An efficient synthesis of 3-halofurans by the intramolecular cyclization of 2-(1-alkynyl)-2-alken-1-ones with cupric halide has been developed. A broad range of 3-chloro- and 3-bromofuran derivatives could be obtained in the present method in moderate to good yields. The 3-halofuran derivatives are potential synthetic intermediates for amplification of molecular complexity

  16. Recent advances in efficient and selective synthesis of di-, tri-, and tetrasubstituted alkenes via Pd-catalyzed alkenylation-carbonyl olefination synergy.

    Science.gov (United States)

    Negishi, Ei-ichi; Huang, Zhihong; Wang, Guangwei; Mohan, Swathi; Wang, Chao; Hattori, Hatsuhiko

    2008-11-18

    Although generally considered competitive, the alkenylation and carbonyl olefination routes to alkenes are also complementary. In this Account, we focus on these approaches for the synthesis of regio- and stereodefined di- and trisubstituted alkenes and a few examples of tetrasubstituted alkenes. We also discuss the subset of regio- and stereodefined dienes and oligoenes that are conjugated. Pd-catalyzed cross-coupling using alkenyl metals containing Zn, Al, Zr, and B (Negishi coupling and Suzuki coupling) or alkenyl halides and related alkenyl electrophiles provides a method of alkenylation with the widest applicability and predictability, with high stereo- and regioselectivity. The requisite alkenyl metals or alkenyl electrophiles are most commonly prepared through highly selective alkyne addition reactions including (i) conventional polar additions, (ii) hydrometalation, (iii) carbometalation, (iv) halometalation, and (v) other heteroatom-metal additions. Although much more limited in applicability, the Heck alkenylation offers an operationally simpler, viable alternative when it is highly selective and satisfactory. A wide variety of carbonyl olefination reactions, especially the Wittig olefination and its modifications represented by the E-selective HWE olefination and the Z-selective Still-Gennari olefination, collectively offer the major alternative to the Pd-catalyzed alkenylation. However, the carbonyl olefination method fundamentally suffers from more limited stereochemical options and generally lower stereoselectivity levels than the Pd-catalyzed alkenylation. In a number of cases, however, very high (>98%) stereoselectivity levels have been attained in the syntheses of both E and Z isomers. The complementarity of the alkenylation and carbonyl olefination routes provide synthetic chemists with valuable options. While the alkenylation involves formation of a C-C single bond to a CC bond, the carbonyl olefination converts a CO bond to a CC bond. When a

  17. Investigations into Chemical Hydrogen Storage and the anti-Markovnikov Hydroamination of Alkenes

    Science.gov (United States)

    St. John, Anthony J.

    The known carbon-boron-nitrogen (CBN) material ethylenediamine bisborane (EDBB) has been prepared and tested as a potential hydrogen storage material. Dehydrogenation of EDBB was achieved using the (t BuPOCOP)Ir(H)2 (t BuPOCOP = 2,6-bis(OPtBu2)C 6H3) catalyst. This reaction results in the release of two equivalents of hydrogen per molecule of EDBB. The product of this reaction is an insoluble, likely oligomeric, species. Heating the reaction mixture does not result in the release of additional equivalents of hydrogen. A new CBN material, 1,2-B,N-cyclohexane, was targeted as a potential hydrogen storage material. The enthalpy of dehydrogenation of 1,2-B,N-cyclohexane to 1,2-dihydro-1,2-azaborine was calculated to be 23.5 kcal/mol at 298 K using the B3LYP basis set. Ultimately, our collaborators at the University of Oregon prepared 1,2-B,N-cyclohexane. This molecule is a stable solid and undergoes thermal dehydrogenation of the B-N bond at 150 °C. The dehydrogenation of a variety of cyclic CBN materials was studied with the ( tBuPOCOP)Ir(H)2 catalyst. A number of cobalt-pincer complexes were tested as ammonia borane (AB) dehydrogenation catalysts. (PhPSiNSiP)CoCl (PhPSiNSiP = (N(SiMe2CH2PPh 2)2) was found to be a very active precatalyst for AB dehydrogenation, releasing 1 equivalent of hydrogen at 2.0 mol % catalyst loading within 5 minutes. The product of this reaction was characterized as cyclopentaborazane. The catalyst lifetime is limited and the identity of the active species remains unknown. A novel [(tBuPOCOP)Co] 2Hg complex was synthesized by reaction of (t BuPOCOP)CoI with Na/Hg. This complex was fully characterized by 1H NMR spectroscopy, elemental analysis, and X-ray crystallography. A new catalytic pathway for the anti-Markovnikov hydroamination of alkenes is proposed. The individual steps of this pathway were studied with the [(MTPA)Rh(propene)][BPh 4] (MTPA = tris((6-methyl-2-pyridyl)methyl)amine) complex. Protonation of this complex with anilinium

  18. Ruthenium meso-Tetrakis(2,6-dichlorophenyl)porphyrin Complex Immobilized in Mesoporous MCM-41 as a Heterogeneous Catalyst for Selective Alkene Epoxidations.

    Science.gov (United States)

    Liu, Chun-Jing; Yu, Wing-Yiu; Li, Shou-Gui; Che, Chi-Ming

    1998-10-16

    A ruthenium complex of meso-tetrakis(2,6-dichlorophenyl)porphyrin, [Ru(II)(TDCPP)(CO)(EtOH)], is immobilized into mesoporous MCM-41 molecular sieves; the supported Ru catalyst can effect highly selective heterogeneous alkene epoxidations using 2,6-dichloropyridine N-oxide as terminal oxidant. Aromatic and aliphatic alkenes can be efficiently converted to their epoxides in good yields and selectivities, and cis-alkenes such as cis-stilbene, cis-beta-methylstyrene, and cis-beta-deuteriostyrene are epoxidized stereospecifically. Oxidation of cycloalkenes, e.g., norbornene and cyclooctene, can be carried out effectively using the heterogeneous Ru-catalyzed reaction while these alkenes are unreactive in the zeolite-based titanium silicate (TS-1)-catalyzed conditions (Murugavel, R.; Roesky, H. W. Angew. Chem., Int. Ed. Engl. 1997, 36, 477). On the other hand, the Ru/M-41(m) catalyst displays size selectivity in the (+)-limonene oxidation where the terminal C=C bond (vs internal trisubstituted C=C bond) becomes more readily oxidized. Bulky 3,4,6-tri-O-benzyl-D-glucal has failed to react under the heterogeneous Ru-catalyzed conditions, whereas the smaller acetyl derivative is converted to a 3:1 mixture of alpha- and beta-glycal epoxides. The Ru/M-41(m) catalyst can be used repeatedly, and 67% of its initial activity is retained after 11 691 turnovers (three runs). The loss of activity is attributed to catalyst leaching and/or deactivation. On the basis of Hammett correlation (rho(+) = -0.72, R = 0.997) and product studies (cyclohexene and cis-alkenes as the substrates), a reactive dioxoruthenium(VI) porphyrin intermediate is not favored. An oxoruthenium(V) complex or oxoruthenium(IV) porphyrin cation radical could be the key intermediate for this highly selective epoxidation reaction.

  19. Sequential Functionalization of Alkynes and Alkenes Catalyzed by Gold(I) and Palladium(II) N-Heterocyclic Carbene Complexes

    KAUST Repository

    Gómez-Herrera, Alberto

    2016-08-22

    The iodination of terminal alkynes for the synthesis of 1-iodoalkynes using N-iodosuccinimide in the presence of a AuI-NHC (NHC=N-heterocyclic carbene) catalyst is reported. A series of aromatic alkynes was transformed successfully into the corresponding 1-iodoalkynes in good to excellent yields under mild reaction conditions. The further use of these compounds as organic building blocks and the advantageous choice of metal-NHC complexes as catalysts for alkyne functionalization were further demonstrated by performing selective AuI-catalyzed hydrofluorination to yield (Z)-2-fluoro-1-iodoalkenes, followed by a Suzuki–Miyaura cross-coupling with aryl boronic acids catalyzed by a PdII-NHC complex to access trisubstituted (Z)-fluoroalkenes. All methodologies can be performed sequentially with only minor variations in the optimized individual reaction conditions, maintaining high efficiency and selectivity in all cases, which therefore, provides straightforward access to valuable fluorinated alkenes from commercially available terminal alkynes.

  20. Infrared matrix isolation and theoretical studies of reactions of ozone with bicyclic alkenes: α-pinene, norbornene, and norbornadiene.

    Science.gov (United States)

    Kugel, Roger W; Ault, Bruce S

    2015-01-15

    The reactions of ozone with three bicyclic alkenes, α-pinene, norbornene, and norbornadiene, were studied by low-temperature (14 K), argon matrix isolation infrared spectroscopy including (18)O isotope-labeling studies. Theoretical calculations of some of the proposed reaction intermediates and products were carried out using the Gaussian 09 suite of programs, applying density functional theory (DFT), the B3LYP functional, and the 6-311G++(d,2p) basis set. In the α-pinene/ozone system, the thermal reaction between α-pinene and ozone was too slow to observe under the twin-jet or merged-jet deposition conditions of these experiments. However, red light (λ ≥ 600 nm) irradiation of the argon matrixes containing α-pinene and ozone caused new infrared peaks to appear that could be readily assigned to reaction products of α-pinene with O((3)P) resulting from ozone photolysis: α-pinene oxide (with an epoxide ring) and two isomeric ketones. Norbornene and norbornadiene were both found to react with ozone in the gas phase during twin-jet or merged-jet deposition of these mixtures with argon. New peaks observed in the infrared spectra were assigned to the primary ozonides, Criegee intermediates, and secondary ozonides of norbornene and norbornadiene, indicating that the bulk of these reactions proceeded via the "classic" Criegee mechanism for ozonolysis of alkenes. Calculated infrared frequencies and molecular energies support these conclusions. Ultraviolet irradiation of these mixtures resulted in complete decomposition of the early intermediates and the formation of acids, aldehydes, alcohols, carbon dioxide, and carbon monoxide. In any case, no evidence for "unusual" chemistry, prompted by the bicyclic nature of the reactants, was observed.

  1. Chain propagation and termination mechanisms for polymerization of conjugated polar alkenes by [Al]-based frustrated Lewis pairs

    KAUST Repository

    He, Jianghua

    2014-11-25

    A combined experimental and theoretical study on mechanistic aspects of polymerization of conjugated polar alkenes by frustrated Lewis pairs (FLPs) based on N-heterocyclic carbene (NHC) and Al(C6F5)3 pairs is reported. This study consists of three key parts: structural characterization of active propagating intermediates, propagation kinetics, and chain-termination pathways. Zwitterionic intermediates that simulate the active propagating species in such polymerization have been generated or isolated from the FLP activation of monomers such as 2-vinylpyridine and 2-isopropenyl-2-oxazoline-one of which, IMes+-CH2C(Me)=(C3H2NO)Al(C6F5)3 - (2), has been structurally characterized. Kinetics performed on the polymerization of 2-vinylpyridine by ItBu/Al(C6F5)3 revealed that the polymerization follows a zero-order dependence on monomer concentration and a first-order dependence on initiator (ItBu) and activator [Al(C6F5)3] concentrations, indicating a bimolecular, activated monomer propagation mechanism. The Lewis pair polymerization of conjugate polar alkenes such as methacrylates is accompanied by competing chain-termination side reactions; between the two possible chain-termination pathways, the one that proceeds via intramolecular backbiting cyclization involving nucleophilic attack of the activated ester group of the growing polymer chain by the O-ester enolate active chain end to generate a six-membered lactone (δ-valerolactone)-terminated polymer chain is kinetically favored, but thermodynamically disfavored, over the pathway leading to the -ketoester-terminated chain, as revealed by computational studies.

  2. Facile Preparation of (2Z,4E)-Dienamides by the Olefination of Electron-deficient Alkenes with Allyl Acetate.

    Science.gov (United States)

    Ding, Liyuan; Yu, Chunbing; Zhao, Zhenqiang; Li, Feifei; Zhang, Jian; Zhong, Guofu

    2017-06-21

    Direct cross-coupling between two alkenes via vinylic C-H bond activation represents an efficient strategy for the synthesis of butadienes with high atomic and step economy. However, this functionality-directed cross-coupling reaction has not been developed, as there are still limited directing groups in practical use. In particular, a stoichiometric amount of oxidant is usually required, producing a large amount of waste. Due to our interest in novel 1,3-butadiene synthesis, we describe the ruthenium-catalyzed olefination of electron-deficient alkenes using allyl acetate and without external oxidant. The reaction of 2-phenyl acrylamide and allyl acetate was chosen as a model reaction, and the desired diene product was obtained in 80% isolated yield with good stereoselectivity (Z,E/Z,Z = 88:12) under optimal conditions: [Ru(p-cymene) Cl2]2 (3 mol %) and AgSbF6 (20 mol %) in DCE at 110 ºC for 16 h. With the optimized catalytic conditions in hand, representative α- and/or β-substituted acrylamides were investigated, and all reacted smoothly, regardless of aliphatic or aromatic groups. Also, differently N-substituted acrylamides have proven to be good substrates. Moreover, we examined the reactivity of different allyl derivatives, suggesting that the chelation of acetate oxygen to the metal is crucial for the catalytic process. Deuterium-labeled experiments were also conducted to investigate the reaction mechanism. Only Z-selective H/D exchanges on acrylamide were observed, indicating a reversible cyclometalation event. In addition, a kinetic isotope effect (KIE) of 3.2 was observed in the intermolecular isotopic study, suggesting that the olefinic C-H metalation step is probably involved in the rate-determining step.

  3. Self-assembled monolayers of 1-alkenes on oxidized platinum surfaces as platforms for immobilized enzymes for biosensing

    Energy Technology Data Exchange (ETDEWEB)

    Alonso, Jose Maria; Bielen, Abraham A.M. [Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB, Wageningen (Netherlands); Olthuis, Wouter [BIOS Lab on a Chip Group, MESA+ and MIRA Institutes, University of Twente, P.O. Box 217, 7500 AE Enschede (Netherlands); Kengen, Servé W.M. [Laboratory of Microbiology, Wageningen University, 6703HB Wageningen (Netherlands); Zuilhof, Han, E-mail: han.zuilhof@wur.nl [Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB, Wageningen (Netherlands); Department of Chemical and Materials Engineering, King Abdulaziz University, Jeddah 22254 (Saudi Arabia); Franssen, Maurice C.R., E-mail: maurice.franssen@wur.nl [Laboratory of Organic Chemistry, Wageningen University, Dreijenplein 8, 6703 HB, Wageningen (Netherlands)

    2016-10-15

    Highlights: • Three different oxidases are covalently attached to alkene based SAMs on PtOx. • Attached enzymes remain active and their activity is assessed by chronoamperometry. • Functionalized PtOx allows electron mediator free chronoamperometry measurements. • The thus formed enzyme electrodes are useful as biosensors for glucose and lactate. • Immobilization of human HAOX foresees in vivo lactate monitoring in humans. - Abstract: Alkene-based self-assembled monolayers grafted on oxidized Pt surfaces were used as a scaffold to covalently immobilize oxidase enzymes, with the aim to develop an amperometric biosensor platform. NH{sub 2}-terminated organic layers were functionalized with either aldehyde (CHO) or N-hydroxysuccinimide (NHS) ester-derived groups, to provide anchoring points for enzyme immobilization. The functionalized Pt surfaces were characterized by X-ray photoelectron spectroscopy (XPS), static water contact angle (CA), infrared reflection absorption spectroscopy (IRRAS) and atomic force microscopy (AFM). Glucose oxidase (GOX) was covalently attached to the functionalized Pt electrodes, either with or without additional glutaraldehyde crosslinking. The responses of the acquired sensors to glucose concentrations ranging from 0.5 to 100 mM were monitored by chronoamperometry. Furthermore, lactate oxidase (LOX) and human hydroxyacid oxidase (HAOX) were successfully immobilized onto the PtOx surface platform. The performance of the resulting lactate sensors was investigated for lactate concentrations ranging from 0.05 to 20 mM. The successful attachment of active enzymes (GOX, LOX and HAOX) on Pt electrodes demonstrates that covalently functionalized PtOx surfaces provide a universal platform for the development of oxidase enzyme-based sensors.

  4. Oxidation of Alkenes with H2O2 by an in-Situ Prepared Mn(II)/Pyridine-2-carboxylic Acid Catalyst and the Role of Ketones in Activating H2O2

    NARCIS (Netherlands)

    Dong, Jia Jia; Saisaha, Pattama; Meinds, Tim G.; Alsters, Paul L.; Ijpeij, Edwin G.; van Summeren, Ruben P.; Mao, Bin; Fananas-Mastral, Martin; de Boer, Johannes W.; Hage, Ronald; Feringa, Ben L.; Browne, Wesley R.

    A simple, high yielding catalytic method for the multigram scale selective epoxidation of electron-rich alkenes using near-stoichiometric H2O2 under ambient conditions is reported. The system consists of a Mn(II) salt (

  5. Detailed Mechanistic Studies on Palladium-Catalyzed Selective C-H Olefination with Aliphatic Alkenes: A Significant Influence of Proton Shuttling.

    Science.gov (United States)

    Deb, Arghya; Hazra, Avijit; Peng, Qian; Paton, Robert S; Maiti, Debabrata

    2017-01-18

    Directing group-assisted regioselective C-H olefination with electronically biased olefins is well studied. However, the incorporation of unactivated olefins has remained largely unsuccessful. A proper mechanistic understanding of olefination involving unactivated alkenes is therefore essential for enhancing their usage in future. In this Article, detailed experimental and computational mechanistic studies on palladium catalyzed C-H olefination with unactivated, aliphatic alkenes are described. The isolation of Pd(II) intermediates is shown to be effective for elucidating the elementary steps involved in catalytic olefination. Reaction rate and order determination, control experiments, isotopic labeling studies, and Hammett analysis have been used to understand the reaction mechanism. The results from these experimental studies implicate β-hydride elimination as the rate-determining step and that a mechanistic switch occurs between cationic and neutral pathway. Computational studies support this interpretation of the experimental evidence and are used to uncover the origins of selectivity.

  6. Synthesis of Aryl-(E)-2-(azidomethyl)alkenoate and Aryl-(Z)-2-(azidomethyl)acrylonitrile from Aryl Aldehydes and Activated Alkenes via One-Pot Way

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang-Jin; Yang, Hae-Won; Han, Tae-Hwi; Yoon, Cheol Min [Korea University, Sejong (Korea, Republic of)

    2016-05-15

    Aryl-(E)-2-(azidomethyl)alkenoate and aryl-(Z)-2-(azidomethyl)acrylonitrile from aryl aldehydes and activated alkenes (acrylate and acrylonitrile) were synthesized in one-pot consecutive way with excellent stereoselectivity in good to high yield. The method include a three-step one-pot processes: Baylis-Hillman reaction of aryl aldehydes and activated alkenes using DABCO followed by acetylation using acetic anhydride and a catalytic amount of DMAP and nucleophilic substitution using sodium azide in DMF at room temperature. Our one-pot synthetic protocol is efficient and simple. Organoazides are one of the most important synthetic intermediates for the preparation of nitrogen-containing organic compounds, for example, amines via reduction, imines via rearrangement, and other nitrogen-containing heterocycles via cycloaddition reactions. Because allyl azides among them are versatile building skeletons for the synthesis of biologically active nitrogen-containing heterocycles, the synthesis of allyl azides have become an attractive research area.

  7. First-Row Late Transition Metals for Catalytic Alkene Hydrofunctionalisation: Recent Advances in C-N, C-O and C-P Bond Formation

    Directory of Open Access Journals (Sweden)

    Sophie Bezzenine-Lafollée

    2017-11-01

    Full Text Available This review provides an outline of the most noteworthy achievements in the area of C-N, C-O and C-P bond formation by hydroamination, hydroalkoxylation, hydrophosphination, hydrophosphonylation or hydrophosphinylation reaction on unactivated alkenes (including 1,2- and 1,3-dienes promoted by first-row late transition metal catalytic systems based on manganese, iron, cobalt, nickel, copper and zinc. The relevant literature from 2009 until mid-2017 has been covered.

  8. Molecular weight growth in Titan's atmosphere: branching pathways for the reaction of 1-propynyl radical (H3CC≡C˙) with small alkenes and alkynes.

    Science.gov (United States)

    Kirk, Benjamin B; Savee, John D; Trevitt, Adam J; Osborn, David L; Wilson, Kevin R

    2015-08-28

    The reaction of small hydrocarbon radicals (i.e.˙CN, ˙C2H) with trace alkenes and alkynes is believed to play an important role in molecular weight growth and ultimately the formation of Titan's characteristic haze. Current photochemical models of Titan's atmosphere largely assume hydrogen atom abstraction or unimolecular hydrogen elimination reactions dominate the mechanism, in contrast to recent experiments that reveal significant alkyl radical loss pathways during reaction of ethynyl radical (˙C2H) with alkenes and alkynes. In this study, the trend is explored for the case of a larger ethynyl radical analogue, the 1-propynyl radical (H3CC[triple bond, length as m-dash]C˙), a likely product from the high-energy photolysis of propyne in Titan's atmosphere. Using synchrotron vacuum ultraviolet photoionization mass spectrometry, product branching ratios are measured for the reactions of 1-propynyl radical with a suite of small alkenes (ethylene and propene) and alkynes (acetylene and d4-propyne) at 4 Torr and 300 K. Reactions of 1-propynyl radical with acetylene and ethylene form single products, identified as penta-1,3-diyne and pent-1-en-3-yne, respectively. These products form by hydrogen atom loss from the radical-adduct intermediates. The reactions of 1-propynyl radical with d4-propyne and propene form products from both hydrogen atom and methyl loss, (-H = 27%, -CH3 = 73%) and (-H = 14%, -CH3 = 86%), respectively. Together, these results indicate that reactions of ethynyl radical analogues with alkenes and alkynes form significant quantities of products by alkyl loss channels, suggesting that current photochemical models of Titan over predict both hydrogen atom production as well as the efficiency of molecular weight growth in these reactions.

  9. Cross metathesis with hydroxamate and benzamide BOC-protected alkenes to access HDAC inhibitors and their biological evaluation highlighted intrinsic activity of BOC-protected dihydroxamates.

    Science.gov (United States)

    Zwick, Vincent; Nurisso, Alessandra; Simões-Pires, Claudia; Bouchet, Samuel; Martinet, Nadine; Lehotzky, Attila; Ovadi, Judit; Cuendet, Muriel; Blanquart, Christophe; Bertrand, Philippe

    2016-01-01

    Conditions for the metathesis of alkenes in the convergent synthesis of HDAC inhibitors have been improved by continuous catalyst flow injection in the reaction media. Intermediate and target compounds obtained were tested for their ability to induce HDAC inhibition and tubulin acetylation, revealing the key role of the tert-butyloxycarbonyl (BOC) group for more HDAC6 selectivity. Molecular modelling added rationale for this BOC effect. Copyright © 2015 Elsevier Ltd. All rights reserved.

  10. Implementation of PC-SAFT and SAFT + Cubic for modeling thermodynamic properties of eight 1-alkenes and their mixtures

    International Nuclear Information System (INIS)

    Polishuk, Ilya; Perel, Ariel

    2012-01-01

    Highlights: ► PC-SAFT and SAFT + Cubic are used for modeling properties of 1-alkenes and their mixtures. ► SAFT + Cubic appears as a better estimator of pure compound data than PC-SAFT. ► SAFT + Cubic is superior in modeling inter-relation between VLE and LLE in mixtures. - Abstract: In the current study the widely used theoretically based model PC-SAFT and the recently proposed SAFT + Cubic have been implemented for correlating and predicting various thermodynamic properties of 1-Hexene, 1-Heptene, 1-Octene, 1-Nonene, 1-Decene, 1-Dodecene, 1-Tetradecene, and 1-Hexadecene, and the available high pressure data on their mixtures. Unlike PC-SAFT, SAFT + Cubic is capable of correlating the critical and subcritical pure compound data simultaneously. In addition, SAFT + Cubic is advantageous in predicting the isothermal compressibility factors and sound velocities. It is also superior in correlating the complex phase behavior in the asymmetric systems {Methane(1) + 1-Hexene(2)} and {Methane(1) + 1-Heptene(2)}. Overestimation of critical temperatures and pressures affects the accuracy of PC-SAFT in predicting VLE in the system {n-Hexane(1) + 1-Hexadecene(2)}. At the same time, this disadvantage of PC-SAFT possibly turns into advantage while modeling the VLE data of {Carbon Dioxide(1) + 1-Hexene(2)}. As seems, both of them are capable of only rough estimation of the heat capacity data.

  11. Tribology and stability of organic monolayers on CrN: a comparison among silane, phosphonate, alkene, and alkyne chemistries.

    Science.gov (United States)

    Pujari, Sidharam P; Li, Yan; Regeling, Remco; Zuilhof, Han

    2013-08-20

    The fabrication of chemically and mechanically stable monolayers on the surfaces of various inorganic hard materials is crucial to the development of biomedical/electronic devices. In this Article, monolayers based on the reactivity of silane, phosphonate, 1-alkene, and 1-alkyne moieties were obtained on the hydroxyl-terminated chromium nitride surface. Their chemical stability and tribology were systematically investigated. The chemical stability of the modified CrN surfaces was tested in aqueous media at 60 °C at pH 3, 7, and 11 and monitored by static water contact angle measurements, X-ray photoelectron spectroscopy (XPS), ellipsometry, and Fourier transform infrared reflection absorption spectroscopy (FT-IRRAS). The tribological properties of the resulting organic monolayers with different end groups (fluorinated or nonfluorinated) were studied using atomic force microscopy (AFM). It was found that the fluorinated monolayers exhibit a dramatic reduction of adhesion and friction force as well as excellent wear resistance compared to those of nonfluorinated coatings and bare CrN substrates. The combination of remarkable chemical stability and superior tribological properties makes these fluorinated monolayers promising candidates for the development of robust high-performance devices.

  12. Controlled and Efficient Polymerization of Conjugated Polar Alkenes by Lewis Pairs Based on Sterically Hindered Aryloxide-Substituted Alkylaluminum

    Directory of Open Access Journals (Sweden)

    Xiaojun Wang

    2018-02-01

    Full Text Available Reported herein is the development of an effective strategy for controlled and efficient Lewis pair polymerization of conjugated polar alkenes, including methyl methacrylate (MMA, n-butyl methacrylate (nBuMA, and γ-methyl-α-methylene-γ-butyrolactone (γMMBL, by the utilization of sterically encumbered Al(BHT2Me (BHT: 2,6-di-tert-butyl-4-methylphenol as a Lewis acid that shuts down intramolecular backbiting termination. In combination with a selected N-heterocyclic carbene (NHC as a Lewis base, the polymerization of MMA exhibited activity up to 3000 h−1 TOF and an acceptable initiation efficiency of 60.6%, producing polymers with high molecular weight (Mn up to 130 kg/mol and extremely narrow dispersity (Đ = 1.06~1.13. This controlled polymerization with a living characteristic has been evidenced by chain-extension experiments and chain-end analysis, and enabled the synthesis of well-defined diblock copolymers.

  13. Chemical imaging of catalyst deactivation during the conversion of renewables at the single particle level: etherification of biomass-based polyols with alkenes over H-Beta zeolites.

    Science.gov (United States)

    Parvulescu, Andrei N; Mores, Davide; Stavitski, Eli; Teodorescu, Cristian M; Bruijnincx, Pieter C A; Gebbink, Robertus J M Klein; Weckhuysen, Bert M

    2010-08-04

    The etherification of biomass-based alcohols with various linear alpha-olefins under solvent-free conditions was followed in a space- and time-resolved manner on 9 microm large H-Beta zeolite crystals by confocal fluorescence microscopy. This allowed us to visualize the interaction with the substrate and distribution of the coke products into the catalyst at the level of an individual zeolite crystal during the etherification process. The spectroscopic information obtained on the micrometer-scale zeolite was in line with the results obtained with bulk characterization techniques and further confirmed by the catalytic results obtained both for micrometer-scale and nanoscale zeolites. This allowed us to explain the influence of the substrate type (glycerol, glycols, and alkenes) and zeolite properties (Si/Al ratio and particle size) on the etherification activity. The etherification of the biomass-based alcohols takes place mainly on the external surface of the zeolite particles. The gradual blockage of the external surface of the zeolite results in a partial or total loss of etherification activity. The deactivation could be attributed to olefin oligomerization. The high conversions obtained in the etherification of 1,2-propylene glycol with long linear alkenes (up to 80%) and the pronounced deactivation of the zeolite observed in the etherification of glycerol with long linear alkenes (max. 20% conversion) were explained by the spectroscopic measurements and is due to differences in the adsorption, i.e., in the center of the zeolite particle for glycerol and on the external surface in the case of glycols.

  14. Degradation of Hydrocarbons by Members of the Genus Candida II. Oxidation of n-Alkanes and 1-Alkenes by Candida lipolytica

    Science.gov (United States)

    Klug, M. J.; Markovetz, A. J.

    1967-01-01

    Candida lipolytica ATCC 8661 was grown in a mineral-salts hydrocarbon medium. n-Alkanes and 1-alkenes with 14 through 18 carbon atoms were used as substrates. Ether extracts of culture fluids and cells obtained from cultures grown on the various substrates were analyzed by thin-layer and gas-liquid chromatography. Analyses of fluids from cultures grown on n-alkanes indicated a predominance of fatty acids and alcohols of the same chain length as the substrate. In addition, numerous other fatty acids and alcohols were present. Analyses of saponifiable and nonsaponifiable material obtained from the cells revealed essentially the same products. The presence of primary and secondary alcohols, as well as fatty acids, of the same chain length as the n-alkane substrate suggested that attack on both the methyl and α-methylene group was occurring. The significance of these two mechanisms in the degradation of n-alkanes by this organism was not evident from the data presented. Analyses of fluids from cultures grown on 1-alkenes indicated the presence of 1,2-diols, as well as ω-unsaturated fatty acids, of the same chain length as the substrate. Alcohols present were all unsaturated. Saponifiable and nonsaponifiable material obtained from cells contained essentially the same products. The presence of 1,2-diols and ω-unsaturated fatty acids of the same chain length as the substrate from cultures grown on 1-alkenes indicated that both the terminal methyl group and the terminal double bond were being attacked. PMID:6025303

  15. Synthesis of Mo–Fe3O4@SiO2@P4VP core–shell–shell structured magnetic microspheres for alkene epoxidation reactions

    International Nuclear Information System (INIS)

    Huang, Xiubing; Guo, Wanchun; Wang, Ge; Yang, Mu; Wang, Qian; Zhang, Xinxin; Feng, Yanhui; Shi, Zhan; Li, Chunguang

    2012-01-01

    Molybdenum complexes immobilized on core–shell–shell structured Fe 3 O 4 @SiO 2 @poly(4-vinylpyridine) microspheres have been successfully fabricated by grafting [3-(methacryloyloxy)propyl]trimethoxysilane on Fe 3 O 4 @SiO 2 followed by seeded emulsion polymerization of 4-vinylpyridine monomers. The synthesized samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FESEM), x-ray photoelectron spectroscopy (XPS), Fourier-transform infrared spectra (FT-IR) and magnetometer. Their catalytic property was investigated by epoxidation of alkenes, using environmentally friendly H 2 O 2 and ethanol as oxidant and solvent, respectively. The results show that Mo–Fe 3 O 4 @SiO 2 @P4VP catalyst possesses high conversion (99.0%) and selectivity (99.0%) in the epoxidation of cis-cyclooctene at 60 °C for 24 h, and the catalyst can be recovered using a magnet and still shows high conversion (95.0%) and selectivity (99.0%) after being recycled three times. -- Highlights: ► Core–shell–shell structured Mo–Fe 3 O 4 @SiO 2 @P4VP microspheres were fabricated. ► The catalyst shows high activity in the epoxidation of alkenes. ► Environmentally friendly H 2 O 2 and ethanol are used as oxidant and solvent. ► The catalyst can be quickly magnetically recovered and maintains high activity.

  16. Palladium-Catalyzed Reductive Coupling Reaction of Terminal Alkynes with Aryl Iodides Utilizing Hafnocene Difluoride as a Hafnium Hydride Precursor Leading to trans-Alkenes.

    Science.gov (United States)

    Takahashi, Keita; Ogiwara, Yohei; Sakai, Norio

    2018-01-26

    Herein, we describe a reductive cross-coupling of alkynes and aryl iodides by using a novel catalytic system composed of a catalytic amount of palladium dichloride and a promoter precursor, hafnocene difluoride (Cp 2 HfF 2 , Cp=cyclopentadienyl anion), in the presence of a mild reducing reagent, a hydrosilane, leading to a one-pot preparation of trans-alkenes. In this process, a series of coupling reactions efficiently proceeds through the following three steps: (i) an initial formation of hafnocene hydride from hafnocene difluoride and the hydrosilane, (ii) a subsequent hydrohafnation toward alkynes, and (iii) a final transmetalation of the alkenyl hafnium species to a palladium complex. This reductive coupling could be chemoselectively applied to the preparation of trans-alkenes with various functional groups, such as an alkyl group, a halogen, an ester, a nitro group, a heterocycle, a boronic ester, and an internal alkyne. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Rate and Selectivity Control in Thioether and Alkene Oxidation with H 2 O 2 over Phosphonate-Modified Niobium(V)-Silica Catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Thornburg, Nicholas E.; Notestein, Justin M. (NWU)

    2017-09-05

    Supported metal oxide catalysts are versatile materials for liquid-phase oxidations, including alkene epoxidation and thioether sulfoxidation with H2O2. Periodic trends in H2O2 activation was recently demonstrated for alkene epoxidation, highlighting Nb-SiO2 as a more active and selective catalyst than Ti-SiO2. Three representative catalysts are studied consisting of NbV, TiIV, and ZrIV on silica, each made through a molecular precursor approach that yields highly dispersed oxide sites, for thioanisole oxidation by H2O2. Initial rates trend Nb>Ti>>Zr, as for epoxidation, and Nb outperforms Ti for a number of other thioethers. In contrast, selectivity to sulfoxide vs. sulfone trends Ti>Nb>>Zr at all conversions. Modifying the Nb-SiO2 catalyst with phenylphosphonic acid does not completely remove sulfoxidation reactivity, as it did for photooxidation and epoxidation, and results in an unusual material active for sulfoxidation but neither epoxidation nor overoxidation to the sulfone.

  18. The role of salicylic acid, L-ascorbic acid and oxalic acid in promoting the oxidation of alkenes with H(2)O(2) catalysed by [Mn(IV) (2)(O)(3)(tmtacn)(2)](2+)

    NARCIS (Netherlands)

    de Boer, Johannes W.; Alsters, Paul L.; Meetsma, Auke; Hage, Ronald; Browne, Wesley R.; Feringa, Ben L.

    2008-01-01

    The role played by the additives salicylic acid, L-ascorbic acid and oxalic acid in promoting the catalytic activity of [Mn(IV) (2)(O)(3)(tmtacn)(2)](PF(6))(2) {1(PF(6))(2), where tmtacn = N, N ', N ''-trimethyl-1,4,7-triazacyclononane} in the epoxidation and cis-dihydroxylation of alkenes with

  19. Facile regio- and stereoselective metal-free synthesis of all-carbon tetrasubstituted alkenes bearing a C(sp3)-F unit via dehydroxyfluorination of Morita-Baylis-Hillman (MBH) adducts.

    Science.gov (United States)

    Takizawa, Shinobu; Arteaga, Fernando Arteaga; Kishi, Kenta; Hirata, Shuichi; Sasai, Hiroaki

    2014-08-15

    Highly E-selective all-carbon tetrasubstituted alkenes with a C(sp(3))-F unit have been synthesized through a dehydroxyfluorination of Morita-Baylis-Hillman (MBH) adducts which can be readily prepared from α,β-unsaturated carbonyl compounds and α-keto esters. A variety of subsequent transformations afforded monofluoromethyl substituted heterocycles in high yields.

  20. Impact of chamber wall loss of gaseous organic compounds on secondary organic aerosol formation: explicit modeling of SOA formation from alkane and alkene oxidation

    Directory of Open Access Journals (Sweden)

    Y. S. La

    2016-02-01

    Full Text Available Recent studies have shown that low volatility gas-phase species can be lost onto the smog chamber wall surfaces. Although this loss of organic vapors to walls could be substantial during experiments, its effect on secondary organic aerosol (SOA formation has not been well characterized and quantified yet. Here the potential impact of chamber walls on the loss of gaseous organic species and SOA formation has been explored using the Generator for Explicit Chemistry and Kinetics of the Organics in the Atmosphere (GECKO-A modeling tool, which explicitly represents SOA formation and gas–wall partitioning. The model was compared with 41 smog chamber experiments of SOA formation under OH oxidation of alkane and alkene series (linear, cyclic and C12-branched alkanes and terminal, internal and 2-methyl alkenes with 7 to 17 carbon atoms under high NOx conditions. Simulated trends match observed trends within and between homologous series. The loss of organic vapors to the chamber walls is found to affect SOA yields as well as the composition of the gas and the particle phases. Simulated distributions of the species in various phases suggest that nitrates, hydroxynitrates and carbonylesters could substantially be lost onto walls. The extent of this process depends on the rate of gas–wall mass transfer, the vapor pressure of the species and the duration of the experiments. This work suggests that SOA yields inferred from chamber experiments could be underestimated up a factor of 2 due to the loss of organic vapors to chamber walls.

  1. Molybdenum oxide catalysts for metathesis of higher 1-alkenes via supporting MoO2(acetylacetonate)2 and MoO2(glycolate)2 on SBA-15 mesoporous molecular sieves

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Mishra, D.; Marceau, E.; Carrier, X.; Žilková, Naděžda; Bastl, Zdeněk

    2009-01-01

    Roč. 359, 1-2 (2009), s. 129-135 ISSN 0926-860X R&D Projects: GA MŠk MEB020723; GA AV ČR IAA400400805; GA AV ČR KAN100400701 Institutional research plan: CEZ:AV0Z40400503 Keywords : 1-alkene metathesis * Mo heterogeneous catalysts * Molybdenum dioxide bis(acetylacetonate) * Molybdenum dioxide bis(glycolate) Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 3.564, year: 2009

  2. The non-metathetic role of Grubbs' carbene complexes: from hydrogen-free reduction of α,β-unsaturated alkenes to solid-supported sequential cross-metathesis/reduction.

    Science.gov (United States)

    Poeylaut-Palena, Andrés A; Testero, Sebastián A; Mata, Ernesto G

    2011-02-07

    An efficient and high-yielding "hydrogen-free" reduction of α,β-unsaturated alkenes was carried out employing Grubbs' catalyst in a non-metathetic role and Et(3)SiH. Conditions were optimized under microwave irradiation. Application to the solid-phase organic synthesis allows a facile construction of sp(3)-sp(3) carbon bonds through a sequential cross metathesis/olefin reduction.

  3. Palladium nanoparticles supported on fibrous-structured silica nanospheres (KCC-1): An efficient and selective catalyst for the transfer hydrogenation of alkenes

    KAUST Repository

    Qureshi, Ziyauddin

    2015-01-09

    An efficient palladium catalyst supported on fibrous silica nanospheres (KCC-1) has been developed for the hydrogenation of alkenes and α,β-unsaturated carbonyl compounds, providing excellent yields of the corresponding products with remarkable chemoselectivity. Comparison (high-resolution TEM, chemisorption) with analogous mesoporous (MCM-41, SBA-15) silica-supported Pd nanocatalysts prepared under identical conditions, demonstrates the advantage of employing the fibrous KCC-1 morphology versus traditional supports because it ensures superior accessibility of the catalytically active cores along with excellent Pd dispersion at high metal loading. This morphology ultimately leads to higher catalytic activity for the KCC-1-supported nanoparticles. The protocol developed for hydrogenation is advantageous and environmentally benign owing to the use of HCOOH as a source of hydrogen, water as a solvent, and because of efficient catalyst recyclability and durability. The recycled catalyst has been analyzed by XPS spectroscopy and TEM showing only minor changes in the oxidation state of Pd and in the morphology after the reaction, thus confirming the robustness of the catalyst.

  4. Evidence for metal-surface interactions and their role in stabilizing well-defined immobilized Ru-NHC alkene metathesis catalysts.

    Science.gov (United States)

    Samantaray, Manoja K; Alauzun, Johan; Gajan, David; Kavitake, Santosh; Mehdi, Ahmad; Veyre, Laurent; Lelli, Moreno; Lesage, Anne; Emsley, Lyndon; Copéret, Christophe; Thieuleux, Chloé

    2013-02-27

    Secondary interactions are demonstrated to direct the stability of well-defined Ru-NHC-based heterogeneous alkene metathesis catalysts. By providing key stabilization of the active sites, higher catalytic performance is achieved. Specifically, they can be described as interactions between the metal center (active site) and the surface functionality of the support, and they have been detected by surface-enhanced (1)H-(29)Si NMR spectroscopy of the ligand and (31)P solid-state NMR of the catalyst precursor. They are present only when the metal center is attached to the surface via a flexible linker (a propyl group), which allows the active site to either react with the substrate or relax, reversibly, to the surface, thus providing stability. In contrast, the use of a rigid linker (here mesitylphenyl) leads to a well-defined active site far away from the surface, stabilized only by a phosphine ligand which under reaction conditions leaves probably irreversibly, leading to faster decomposition and deactivation of the catalysts.

  5. Activation of the Kelch-like ECH-associated protein 1 (Keap1)/NF-E2-related factor 2 (Nrf2) pathway through covalent modification of the 2-alkenal group of aliphatic electrophiles in Coriandrum sativum L.

    Science.gov (United States)

    Abiko, Yumi; Mizokawa, Mai; Kumagai, Yoshito

    2014-11-12

    Phytochemicals able to activate the transcription factor NF-E2-related factor 2 (Nrf2) were isolated from an extract of Coriandrum sativum L. (C. sativum) leaves by preparative octadecyl silica column chromatography. Ultraperformance liquid chromatography and liquid chromatography-tandem mass spectrometry analysis of the isolated components after derivatization with 2-diphenylacetyl-1,3-inandione-1-hydrazone and experiments with HepG2 cells revealed that (E)-2-alkenals with different carbon numbers play a role in Nrf2 activation in these cells. Such Nrf2 activation appears to be attributable to S-alkylation of Kelch-like ECH-associated protein 1 (Keap1), the negative regulator for Nrf2, as determined by a biotin-PEAC5-maleimide assay. Interestingly, (E)-2-butenal caused Keap1 modification and Nrf2 activation, whereas butanal did not. These results suggest that (E)-2-alkenals with an α,β-unsaturated aldehyde moiety, which is a common substituent in phytochemicals isolated from C. sativum leaves, activate the Keap1/Nrf2 pathway associated with cellular protection.

  6. Weak interactions modulating the dimensionality in supramolecular architectures in three new nickel(II)-hydrazone complexes, magnetostructural correlation, and catalytic potential for epoxidation of alkenes under phase transfer conditions.

    Science.gov (United States)

    Sadhukhan, Dipali; Ray, Aurkie; Pilet, Guillaume; Rizzoli, Corrado; Rosair, Georgina M; Gómez-García, Carlos J; Signorella, Sandra; Bellú, Sebastián; Mitra, Samiran

    2011-09-05

    Three different ONO donor acetyl hydrazone Schiff bases have been synthesized from the condensation of acetic hydrazide with three different carbonyl compounds: salicylaldehyde (HL(1)), 2-hydroxyacetophenone (HL(2)), and 2, 3-dihydroxybenzaldehyde (HL(3)). These tridentate ligands are reacted with Ni(OOCCF(3))(2)·xH(2)O to yield three new Ni(II) complexes having distorted octahedral geometry at each Ni center: [Ni(L(1))(OOCCF(3))(CH(3)OH)](2) (1), [Ni(L(2))(OOCCF(3))(H(2)O)](2) (2), and [Ni(L(3))(L(3)H)](OOCCF(3))(H(2)O)(1.65)(CH(3)OH)(0.35) (3). The ligands and the complexes have been characterized by elemental analysis and IR and UV-vis spectroscopy, and the structures of the complexes have been established by single crystal X-ray diffraction (XRD) study. 1 and 2 are centrosymmetric dinuclear complexes and are structural isomers whereas 3 is a bis chelated cationic monomer coordinated by one neutral and one monoanionic ligand. O-H···O hydrogen bonds in 3 lead to the formation of a dimer. Slight steric and electronic modifications in the ligand backbone provoke differences in the supramolecular architectures of the complexes, leading to a variety of one, two, and three-dimensional hydrogen bonded networks in complexes 1-3 respectively. Variable temperature magnetic susceptibility measurements reveal that moderate antiferromagnetic interactions operate between phenoxo bridged Ni(II) dimers in 1 and 2 whereas very weak antiferromagnetic exchange occurs through hydrogen bonding and π-π stacking interactions in 3. All complexes are proved to be efficient catalysts for the epoxidation of alkenes by NaOCl under phase transfer condition. The efficiency of alkene epoxidation is dramatically enhanced by lowering the pH, and the reactions are supposed to involve high valent Ni(III)-OCl or Ni(III)-O· intermediates. 3 is the best epoxidation catalyst among the three complexes with 99% conversion and very high turnover number (TON, 396).

  7. Mechanistic insights into the selective cyclization of indolines with alkynes and alkenes to produce six- and seven-membered 1,7-fused indolines via Rh(iii) catalysis: a theoretical study.

    Science.gov (United States)

    Han, Lingli; Zhang, Xinyu; Wang, Xingdong; Zhao, Fengyue; Liu, Shaojing; Liu, Tao

    2017-05-10

    The coupling reaction mechanisms of the Rh(iii)-catalyzed redox-neutral C7-selective aryl C-H functionalization of indolines with alkynes and alkenes have been theoretically investigated with the aid of the density functional theory (DFT) calculations. Our calculation results indicate that the active catalyst in this system is the cationic species [Cp*Rh(OAc)] + (2cat) instead of the neutral species Cp*Rh(OAc) 2 (1cat). The origin of forming different products associated with using different coupling partners was also rationalized in detail. For the coupling reaction of N-methoxycarbamoyl-protected indoline (1a) with alkyl alkyne (4a), the electronic effect plays a dominant role and causes the six-membered ring product to be the main product. For the coupling reaction of 1a with aryl alkyne (2a), through the replacement of alkyl alkyne with aryl alkyne, the steric effect serves as a crucial factor, compared with the electronic effect, and leads to the main seven-membered ring product. For the coupling reaction of 1a with acrylate (6a), the chemoselectivity is dictated by the steric effect and electronic effect.

  8. Computational Study on M1/POM Single-Atom Catalysts (M = Cu, Zn, Ag, and Au; POM = [PW12O40]3-): Metal-Support Interactions and Catalytic Cycle for Alkene Epoxidation.

    Science.gov (United States)

    Liu, Chun-Guang; Jiang, Meng-Xu; Su, Zhong-Min

    2017-09-05

    Geometrical structures, metal-support interactions, and infrared (IR) spectroscopy of a series of M 1 /POM (M = Cu, Zn, Ag, and Au; POM = [PW 12 O 40 ] 3- ) single-atom catalysts (SACs), and catalytic cycle for alkene epoxidation catalyzed by M 1 /POM SACs were studied using density functional theory (DFT) calculations. The calculations demonstrate that the most probable anchoring sties for the isolated single atoms studied here in the M 1 /POM SACs are the fourfold hollow sites on the surface of POM support. The bonding interaction between single metal atom and surface of POM support comes from the molecular orbitals with a mixture of d atomic orbital of metal and 2p group orbital of surface oxygen atoms of POM cage. The calculated adsorption energy of isolated metal atoms in these M 1 /POM SACs indicates that the early transition metals (Cu and Zn) have high thermal stability. The DFT-derived IR spectra show that the four characteristic peaks of free Keggin-type POM structure split into six because of introduction of isolated metal atom. Compared with other metal atoms, the Zn 1 /POM SAC has the high reactivity for activity of dioxygen molecule, because the dioxygen moiety in Zn 1 /POM SAC displays O 2 - · radical feature with [POM 4- ·Zn 2+ O 2 - ·] 3- configuration. Finally, a catalytic cycle for ethylene epoxidation by O 2 catalyzed by Zn 1 /POM SAC was proposed based on our DFT calculations. Supported noble-metal SACs are among the most important catalysts currently. However, noble metals are expensive and of limited supply. Development of non-noble-metal SACs is of essential importance. Therefore, the reported Zn 1 /POM SAC would be very useful to guide the search for SACs into non-noble metals.

  9. Isomerization of C[sub 4] alkenes

    Science.gov (United States)

    Smith, L.A. Jr.

    1984-11-13

    A method is described for isomerizing isobutene or n-butene to produce a mixture of isobutene and normal butene, and polymerizing at least a portion thereof to produce isobutene/n-butene co-dimer, which comprises feeding at least 80 weight % of either the isobutene or n-butene to a catalytic distillation reactor containing a fixed bed acidic cation exchange resin catalyst packing which provides both the catalyst sites and distillation sites for the reaction products, isomerizing a portion of the isobutene or n-butene to produce a mixture of isobutene and n-butene and reacting at least a portion of the isobutene and n-butene to form co-dimer of isobutene and n-butene, whereby an overhead fraction containing any unreacted isobutene and n-butene and a bottoms fraction containing co-dimer is produced. The result of the reaction is substantially the same regardless whether the feed is isobutene or n-butene. Other aspects of the invention, include combinations of procedures to produce high purity isobutene and n-butene. Either isobutene or n-butene product (depending on the desired product) can be recycled as feed, thus substantially carrying out the isomerization to extinction and total conversion to the desired product. 1 fig.

  10. Isomerization of C.sub.4 alkenes

    Science.gov (United States)

    Smith, Jr., Lawrence A.

    1984-01-01

    A method for isomerizing isobutene or n-butene to produce a mixture of isobutene and normal butene, and polymerizing at least a portion thereof to produce isobutene/n-butene codimer, which comprieses feeding at least 80 weight % of either the isobutene or n-butene to a catalytic distillation reactor containing a fixed bed acidic cation exchange resin catalyst packing which provides both the catalyst sites and distillation sites for the reaction products, isomerizing a portion of the isobutene or n-butene to produce a mixture of isobutene and n-butene and reacting at least a portion of the isobutene and n-butene to form codimer of isobutene and n-butene, whereby an overhead fraction containing any unreacted isobutene and n-butene and a bottoms fraction containing codimer is produced. The result of the reaction is substantially the same regardless whether the feed is isobutene or n-butene. Other aspects of the invention, include combinations of procedures to produce high purity isobutene and n-butene. Either isobutene or n-butene product (depending on the desired product) can be recycled as feed, thus substantially carrying out the isomerization to extinction and total conversion to the desired product.

  11. High court orders Lavents retrial / Ib Alken

    Index Scriptorium Estoniae

    Alken, Ib

    2003-01-01

    Pärast Euroopa Inimõiguste Kohtu otsust, mille kohaselt rikkus Läti riik Banka Baltija endise juhi Aleksandrs Lavents'i kohtuasja menetlemisel tema põhiõigusi, mõistis Läti Riigikohus asja uuesti läbivaatamisele

  12. Catalytic Alkene Metathesis in Ionic Liquids

    Science.gov (United States)

    Fischmeister, Cédric

    Olefin metathesis has found a tremendous number of application in the past 25 years. Immobilisation of olefin metathesis (pre)catalysts in room temperature ionic liquids (RTILs) offers the opportunity to recover and reuse the catalyst and also to reduce the level of ruthenium (Ru) contaminants in the products.

  13. Alkene conversions with early transition metal catalysts

    NARCIS (Netherlands)

    Bijpost, Erik Alexander

    1996-01-01

    In dit proefschrift worden zowel deze vormingswijze als de katalytische oligomerisatie van alkenen met polaire substituenten uitvoerig beschreven. Dit zou uiteindelijk kunnen leiden tot de ontwikkeling van schonere, selectievere syntheseroutes in de organische fijnchemie. ... Zie: Samenvatting

  14. Influence of alkene substituent in dictating the reaction course to ...

    Indian Academy of Sciences (India)

    RITABRATA DATTA

    2017-11-06

    Nov 6, 2017 ... Following the same synthetic procedure as described in the preparation of 9a, the carbinol 15 (70 mg, 0.26 mmol) was converted to the triene 9c (66 mg, 83%, purified by col- umn chromatography, 4% EA/PE as eluent) by using sodium hydride (19 mg, 0.39 mmol, 50% suspension in oil) and allyl bromide ...

  15. Green oxidation of alkenes in ionic liquid solvent by hydrogen ...

    Indian Academy of Sciences (India)

    Abstract. A series of Fe(III) Schiff base complexes immobilized on MCM-41 were prepared and character- ized by various physicochemical and spectroscopic methods. The complexes were used for oxidation of cyclo- hexene by 30% hydrogen peroxide in the presence and absence of ethylmethyl imidazolium chloride ...

  16. On the large σ-hyperconjugation in alkanes and alkenes.

    Science.gov (United States)

    Wu, Judy I-Chia; Wang, Changwei; McKee, William Chadwick; Schleyer, Paul von Ragué; Wu, Wei; Mo, Yirong

    2014-06-01

    The conventional view that the σCC and σCH bonds in alkanes and unsaturated hydrocarbons are so highly localized that their non-steric interactions are negligible is scrutinized by the block-localized wavefunction (BLW) method. Even molecules considered conventionally to be "strain free" and "unperturbed" have surprisingly large and quite significant total σ-BLW-delocalization energies (DEs) due to their geminal and vicinal hyperconjugative interactions. Thus, the computed BLW-DEs (in kcal mol(-1)) for the antiperiplanar conformations of the n-alkanes (C(N)H(2N+2), N = 1-10) range from 11.6 for ethane to 82.2 for n-decane and are 50.9 for cyclohexane and 91.0 for adamantane. Although σ-electron delocalization in unsaturated hydrocarbons usually is ignored, the σ-BLW-DEs (in kcal mol(-1)) are substantial, as exemplified by D2h ethylene (9.0), triplet D2d ethylene (16.4), allene (19.3), butadiene (19.0), hexatriene (28.3), benzene (28.1), and cyclobutadiene (21.1). While each individual geminal and vicinal hyperconjugative interaction between hydrocarbon σ-bonding and σ-antibonding orbitals tends to be smaller than an individual π conjugative interaction (e.g., 10.2 kcal mol(-1) in anti-1,3-butadiene, the presence of many σ-hyperconjugative interactions (e.g., a total of 12 in anti-1,3-butadiene, see text), result in substantial total σ-stabilization energies (e.g., 19.0 kcal mol(-1) for butadiene), which may surpass those from the π interactions. Although large in magnitude, σ-electron delocalization energies often are obscured by cancellation when two hydrocarbons are compared. Rather than being strain-free, cyclohexane, adamantane, and diamantane suffer from their increasing number of intramolecular 1,4-C…C repulsions resulting in elongated C-C bond lengths and reduced σ-hyperconjugation, compared to the (skew-free) antiperiplanar n-alkane conformers. Instead of being inconsequential, σ-bond interactions are important and merit consideration.

  17. Mechanism of Intramolecular Rhodium- and Palladium-Catalyzed Alkene Alkoxyfunctionalizations

    KAUST Repository

    Vummaleti, Sai V. C.

    2015-11-13

    Density functional theory calculations have been used to investigate the reaction mechanism for the [Rh]-catalyzed intramolecular alkoxyacylation ([Rh] = [RhI(dppp)+] (dppp, 1,3-bis(diphenylphosphino)propane) and [Pd]/BPh3 dual catalytic system assisted intramolecular alkoxycyanation ([Pd] = Pd-Xantphos) using acylated and cyanated 2-allylphenol derivatives as substrates, respectively. Our results substantially confirm the proposed mechanism for both [Rh]- and [Pd]/ BPh3-mediated alkoxyfunctionalizations, offering a detailed geometrical and energetical understanding of all the elementary steps. Furthermore, for the [Rh]-mediated alkoxyacylation, our observations support the hypothesis that the quinoline group of the substrate is crucial to stabilize the acyl metal complex and prevent further decarbonylation. For [Pd]/BPh3-catalyzed alkoxycyanation, our findings clarify how the Lewis acid BPh3 cocatalyst accelerates the only slow step of the reaction, corresponding to the oxidative addition of the cyanate O-CN bond to the Pd center. © 2015 American Chemical Society.

  18. Modification of inorganic surface with 1-alkenes and 1-alkynes

    NARCIS (Netherlands)

    Maat, ter J.

    2012-01-01

    Surface modification is important because it allows the tuning of surface properties, thereby enabling new applications of a material. It can change physical properties such as wettability and friction, but can also introduce chemical functionalities and binding specificity. Several techniques

  19. Influence of alkene substituent in dictating the reaction course to ...

    Indian Academy of Sciences (India)

    RITABRATA DATTA

    2017-11-06

    org/ 10.1007/ s12039-017-1390-3) contains supplementary material, which is available to authorized users. oxidation will provide the butenolide 2. Success of this strategy thus depends on RCM of the triene 3 to afford.

  20. Highly efficient epoxidation of alkenes with m-chloroperbenzoic acid ...

    Indian Academy of Sciences (India)

    The heterogeneous nanocatalyst was characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), Fourier transform infrared spectra (FT-IR), atomic absorption spectroscopy (AAS), vibrating sample magnetometer (VSM) and nitrogen adsorption–desorption isotherm ...

  1. Recent Applications of Alkene Metathesis in Fine Chemical Synthesis

    Science.gov (United States)

    Bicchielli, Dario; Borguet, Yannick; Delaude, Lionel; Demonceau, Albert; Dragutan, Ileana; Dragutan, Valerian; Jossifov, Christo; Kalinova, Radostina; Nicks, François; Sauvage, Xavier

    During the last decade or so, the emergence of the metathesis reaction in organic synthesis has revolutionised the strategies used for the construction of complex molecular structures. Olefin metathesis is indeed particularly suited for the construction of small open-chain molecules and macrocycles using crossmetathesis and ring-closing metathesis, respectively. These reactions serve, inter alia, as key steps in the synthesis of various agrochemicals and pharmaceuticals such as macrocyclic peptides, cyclic sulfonamides, novel macrolides, or insect pheromones. The present chapter is aiming at illustrating the great synthetic potential of metathesis reactions. Shortcomings, such as the control of olefin geometry and the unpredictable effect of substituents on the reacting olefins, will also be addressed. Examples to be presented include epothilones, amphidinolides, spirofungin A, and archazolid. Synthetic approaches involving silicon-tethered ring-closing metathesis, relay ring-closing metathesis, sequential reactions, domino as well as tandem metathesis reactions will also be illustrated.

  2. Green oxidation of alkenes in ionic liquid solvent by hydrogen ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 126; Issue 3 ... Regular Articles Volume 126 Issue 3 May 2014 pp 801-805 ... Department of Chemical Engineering, Birjand Branch, Islamic Azad University, Birjand 9717851367, Iran; Department of Chemistry, Faculty of Sciences, Ferdowsi University of Mashhad, PO ...

  3. Green oxidation of alkenes in ionic liquid solvent by hydrogen ...

    Indian Academy of Sciences (India)

    For correspondence a surface-bound tether containing a functional group. This methodology has been employed successfully in the functionalization of various traditional types of silica supports.26–28 More recently, MCM-41 materi- als have been used extensively as ideal inorganic sup- ports due to their high surface area ...

  4. Fast and Green Microwave-Assisted Conversion of Essential Oil Allylbenzenes into the Corresponding Aldehydes via Alkene Isomerization and Subsequent Potassium Permanganate Promoted Oxidative Alkene Group Cleavage

    DEFF Research Database (Denmark)

    Luu, Thi Xuan Thi; Lam, Trinh To; Le, Thach Ngoc

    2009-01-01

    oxidation of the latter to the corresponding benzaldehyde by KMnO4/CuSO4 center dot 5H(2)O. The assistance by microwave irradiation results in very short reaction times (eugenol (4-allyl-2-methoxyphenol) into vanillin (4-hydroxy-3-methoxybenzaldehyde) has been carried...

  5. Renewable alkenes from the hydrothermal treatment of polyhydroxyalkanoates-containing sludge

    NARCIS (Netherlands)

    Torri, Cristian; Detert Oude Weme, Tom; Samorì, Chiara; Kiwan, Alisar; Brilman, Derk W.F.

    2017-01-01

    Polyhydroxyalkanoates (PHA) are a key constituent of excess sludge produced by Aerobic Sewage Sludge Treatment plants. The accumulation of significant amount of PHA inside aerobic microbial cells occurs when a surplus of an easily degradable carbon source (e.g., volatile fatty acids, VFA) is found

  6. Alkene- and Alkyne- Substituted Methylimidazolium Bromides: Structural Effects and Physical properties (Preprint)

    National Research Council Canada - National Science Library

    Schneider, Stefan; Drake, Gregory; Hall, Leslie; Hawkiins, Tommy; Rosander, Michael; Smith, Dennis

    2007-01-01

    .... X-ray structures of 1-(2-butynyl)-3-methylimidazolium bromide, 1-propargyl-3-methylimidazolium bromide as well as the X-ray structure of 1-allyl-3- methylimidazolium bromide which was previously identified as a room temperature ionic...

  7. Alkene- and alkyne- substituted methylimidazolium bromides: structural effects and Physical properties (Postprint)

    National Research Council Canada - National Science Library

    Schneider, Stefan; Drake, Gregory; Hall, Leslie; Hawkiins, Tommy; Rosander, Michael; Smith, Dennis

    2007-01-01

    .... X-ray structures of 1-(2-butynyl)-3-methylimidazolium bromide, 1-propargyl-3-methylimidazolium bromide as well as the X-ray structure of 1-allyl-3- methylimidazolium bromide which was previously identified as a room temperature ionic...

  8. MECHANISTIC STUDIES ON THE VITAMIN B12-CATALYZED DECHLORINATION OF CHLORINATED ALKENES. (U915562)

    Science.gov (United States)

    The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Concl...

  9. Intramolecular Azide to Alkene Cycloadditions for the Construction of Pyrrolobenzodiazepines and Azetidino-Benzodiazepines

    Czech Academy of Sciences Publication Activity Database

    Hemming, K.; Chambers, Christopher S.; Jamshaid, F.; O´Gorman, Paul A.

    2014-01-01

    Roč. 19, č. 10 (2014), s. 16737-16756 ISSN 1420-3049 Institutional support: RVO:61388971 Keywords : azide * cycloadditions * benzodiazepines Subject RIV: CC - Organic Chemistry Impact factor: 2.416, year: 2014

  10. Selective oxidation of alkanes and/or alkenes to valuable oxygenates

    Science.gov (United States)

    Lin, Manhua [Maple Glen, PA; Pillai, Krishnan S [North Brunwick, NJ

    2011-02-15

    A catalyst, its method of preparation and its use for producing at least one of methacrolein and methacrylic acid, for example, by subjecting isobutane or isobutylene or a mixture thereof to a vapor phase catalytic oxidation in the presence of air or oxygen. In the case where isobutane alone is subjected to a vapor phase catalytic oxidation in the presence of air or oxygen, the product is at least one of isobutylene, methacrolein and methacrylic acid. The catalyst comprises a compound having the formula A.sub.aB.sub.bX.sub.xY.sub.yZ.sub.zO.sub.o wherein A is one or more elements selected from the group of Mo, W and Zr, B is one or more elements selected from the group of Bi, Sb, Se, and Te, X is one or more elements selected from the group of Al, Bi, Ca, Ce, Co, Fe, Ga, Mg, Ni, Nb, Sn, W and Zn, Y is one or more elements selected from the group of Ag, Au, B, Cr, Cs, Cu, K, La, Li, Mg, Mn, Na, Nb, Ni, P, Pb, Rb, Re, Ru, Sn, Te, Ti, V and Zr, and Z is one or more element from the X or Y groups or from the following: As, Ba, Pd, Pt, Sr, or mixtures thereof, and wherein a=1, 0.05oxidation state of the other elements.

  11. Photocatalytic radical addition of 1,1,2,2-tetrafluoro-1-iodoethane to alkenes

    Czech Academy of Sciences Publication Activity Database

    Voltrová, Svatava; Beier, Petr

    2017-01-01

    Roč. 6, č. 115 (2017) ISSN 2071-4807 Institutional support: RVO:61388963 Keywords : photocatalysis * radical addition * Rhodamine B * Eosin Y * tetrafluoroiodoethane * LED Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry http://notes. fluorine 1.ru/public/2017/6_2017/article_2.html

  12. Reactions of the tert-butylthiyl radical with organometallic compounds and alkenes

    Energy Technology Data Exchange (ETDEWEB)

    McPhee, D.J.; Campredon, M.; Lesage, M.; Griller, D. (National Research Council of Canada, Ottawa, Ontario (Canada))

    1989-09-13

    Absolute rate constants for the reactions of the tert-butylthiyl radical with a variety of substrates were measured by using a combination of laser flash photolysis techniques and product studies. Reactions with organometallic substrates such as boranes, phosphines, and phosphites were extremely rapid with rate constants in the range 10{sup 8}-10{sup 9} M{sup {minus}1} s{sup {minus}1}. By contrast, addition to a simple olefin, oct-1-ene, was ca. 100 times less rapid. However, 1,1-diphenyl- and 1,1-dicyclopropylethylene were remarkably efficient traps for tert-butylthiyl and scavenged the radical with rate constants of 9.9 {times} 10{sup 8} and 2.4 {times} 10{sup 8} M{sup {minus}1} s{sup {minus}1}, respectively.

  13. High accuracy ab initio calculations on reactions of OH with 1-alkenes. The case of propene

    Czech Academy of Sciences Publication Activity Database

    Izsák, R.; Szöri, Milan; Knowles, P. J.; Viskolcz, B.

    2009-01-01

    Roč. 5, č. 9 (2009), s. 2313-2321 ISSN 1549-9618 Institutional research plan: CEZ:AV0Z40550506 Keywords : multireference ab initio calculations * OH-addition * H-abstraction by OH Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.804, year: 2009

  14. Alkene Isomerization Using a Solid Acid as Activator and Support for a Homogeneous Catalyst

    Science.gov (United States)

    Seen, Andrew J.

    2004-01-01

    An upper-level undergraduate experiment that, in addition to introducing students to catalysis using an air sensitive transition-metal complex, introduces the use of a solid acid as an activator and support for the catalyst is developed. The increased stability acquired in the course of the process affords the opportunity to characterize the…

  15. Atom-Transfer Radical Addition to Unactivated Alkenes by using Heterogeneous Visible-Light Photocatalysis.

    Science.gov (United States)

    Mao, Liang-Liang; Cong, Huan

    2017-11-23

    Heterogeneous visible-light photocatalysis represents an important route toward the development of sustainable organic synthesis. In this study visible light-induced, heavy metal-free atom-transfer radical addition to unactivated terminal olefins is carried out by using the combination of heterogeneous titanium dioxide as photocatalyst and a hypervalent iodine(III) reagent as co-initiator. The reaction can be applied to a range of substrates with good functional-group tolerance under very mild conditions. In addition to a number of commonly used atom-transfer reagents, the relatively challenging chloroform is also suitable. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. The upper explosion limit of lower alkanes and alkenes in air at elevated pressures and temperatures.

    Science.gov (United States)

    Van den Schoor, F; Verplaetsen, F

    2006-01-16

    The upper explosion limit (UEL) of ethane-air, propane-air, n-butane-air, ethylene-air and propylene-air mixtures is determined experimentally at initial pressures up to 30 bar and temperatures up to 250 degrees C. The experiments are performed in a closed spherical vessel with an internal diameter of 200 mm. The mixtures are ignited by fusing a coiled tungsten wire, placed at the centre of the vessel, by electric current. Flame propagation is said to have taken place if there is a pressure rise of at least 1% of the initial pressure after ignition of the mixture. In the pressure-temperature range investigated, a linear dependence of UEL on temperature and a bilinear dependence on pressure are found except in the vicinity of the auto-ignition range. A comparison of the UEL data of the lower alkanes shows that the UEL expressed as equivalence ratio (the actual fuel/air ratio divided by the stoichiometric fuel/air ratio) increases with increasing carbon number in the homologous series of alkanes.

  17. (III) Porphyrins for the selective oxidation of alkanes/alkenes by t ...

    Indian Academy of Sciences (India)

    Abstract. Two iron(III) tetraphenyl porphyrin catalytic units are connected by an azo-link to form the dimeric .... and was decanted and was evaporated to dryness under reduced pressure. The crude solid was purified by silica gel column chromatography and the desired .... matography equipped with flame ionization detector.

  18. Pauson-Khand Reaction of Internal Dissymmetric Trifluoromethyl Alkynes. Influence of the Alkene on the Regioselectivity

    Directory of Open Access Journals (Sweden)

    Nuria Aiguabella

    2014-02-01

    Full Text Available The scope of the Pauson-Khand reaction (PKR of internal trifluoromethyl alkynes, previously described with norbornadiene, is expanded to norbornene and ethylene. A thorough structural analysis of the resulting PK adducts has been carried out to unveil that α-trifluoromethylcyclopentenones are preferred in all cases, independently of the electronic properties of the alkyne. The regioselectivity observed with norbornadiene and ethylene is higher than in the case of norbornene.

  19. Advances in Nucleophilic Phosphine Catalysis of Alkenes, Allenes, Alkynes, and MBHADs

    Science.gov (United States)

    Fan, Yi Chiao

    2014-01-01

    In nucleophilic phosphine catalysis, tertiary phosphines undergo conjugate additions to activated carbon–carbon multiple bonds to form β-phosphonium enolates, β-phosphonium dienolates, β-phosphonium enoates, and vinyl phosphonium ylides as intermediates. When these reactive zwitterionic species react with nucleophiles and electrophiles, they may generate carbo- and heterocycles with multifarious molecular architectures. This Article describes the reactivities of these phosphonium zwitterions, the applications of phosphine catalysis in the syntheses of biologically active compounds and natural products, and recent developments in the enantioselective phosphine catalysis. PMID:24196409

  20. Alkene hydrogenation activity of enoate reductases for an environmentally benign biosynthesis of adipic acid.

    Science.gov (United States)

    Joo, Jeong Chan; Khusnutdinova, Anna N; Flick, Robert; Kim, Taeho; Bornscheuer, Uwe T; Yakunin, Alexander F; Mahadevan, Radhakrishnan

    2017-02-01

    Adipic acid, a precursor for Nylon-6,6 polymer, is one of the most important commodity chemicals, which is currently produced from petroleum. The biosynthesis of adipic acid from glucose still remains challenging due to the absence of biocatalysts required for the hydrogenation of unsaturated six-carbon dicarboxylic acids to adipic acid. Here, we demonstrate the first enzymatic hydrogenation of 2-hexenedioic acid and muconic acid to adipic acid using enoate reductases (ERs). ERs can hydrogenate 2-hexenedioic acid and muconic acid producing adipic acid with a high conversion rate and yield in vivo and in vitro . Purified ERs exhibit a broad substrate spectrum including aromatic and aliphatic 2-enoates and a significant oxygen tolerance. The discovery of the hydrogenation activity of ERs contributes to an understanding of the catalytic mechanism of these poorly characterized enzymes and enables the environmentally benign biosynthesis of adipic acid and other chemicals from renewable resources.

  1. Sterically Overcrowded Alkenes : a Stereospecific Photochemical and Thermal Isomerization of a Benzoannulated Bithioxanthylidene

    NARCIS (Netherlands)

    Feringa, Bernard; Jager, Wolter F.; Lange, Ben de

    1993-01-01

    Enantiomerically pure sterically overcrowded 12H-benzo[a]thioxanthenyl-12-(2'-methyl-9'H-thioxanthene-9'-ylidene) shows a stereospecific photochemical and thermal isomerization of the P-trans into the M-cis isomer (and vice versa), with a large thermal isomerization barrier (ΔG‡ = 28.6 kcal mol–1)

  2. Synthesis, crystal and molecular structure and dynamic behaviour of new dimethyldioxanedione based inherently dissymmetric overcrowded alkenes.

    NARCIS (Netherlands)

    Huck, NPM; Meetsma, A; Zijlstra, R; Feringa, BL; Huck, Nina P.M.; Feringa, Bernard

    1995-01-01

    Two representatives of new chiral sterically overcrowded ethylenes, 2-methyl(9-thioxanthylidene)-2,2-dimethyl- 1,3-dioxane-4,6-dione (3) and 12H-benzo[a]thioxanthylidene-2,2-dimethyl-1,3-dioxane-4,6-dione (5), have been prepared and dynamic H-1 NMR studies revealed 1 racemization barriers of 10.3

  3. Chemotactic behavior of deep subsurface bacteria toward carbohydrates, amino acids and a chlorinated alkene

    Energy Technology Data Exchange (ETDEWEB)

    Lopez de Victoria, G. (Puerto Rico Univ., Rio Piedras (Puerto Rico). Dept. of Biology)

    1989-02-01

    The chemotactic behavior of deep terrestrial subsurface bacteria toward amino acids, carbohydrates and trichloroethylene was assayed using a modification of the capillary method and bacterial enumeration by acridine orange direct counts. Eleven isolates of bacteria isolated from six different geological formations were investigated. A bimodal response rather than an absolute positive or negative response was observed in most assays. Most of the isolates were positively chemotactic to low concentrations of substrates and were repelled by high concentrations of the same substrate. However, this was not the case for trichloroethylene (TCE) which was mostly an attractant and elicited the highest responses in all the isolates when compared with amino acids and carbohydrates. The movement rates of these isolates in aseptic subsurface sediments in the absence and presence of TCE were also determined using a laboratory model. All of the isolates showed distinct response range, peak, and threshold concentrations when exposed to the same substrates suggesting that they are possibly different species as has been inferred from DNA homology studies. 101 refs., 4 figs., 57 tabs.

  4. Synthesis of Alkyne and Alkene Ketal Derivatives of Pentacyclo[5.4 ...

    African Journals Online (AJOL)

    NICO

    2013-11-04

    Nov 4, 2013 ... Micromass Autospec-Tof- and a Thermo DFS magnetic sector mass spectrometer (HRMS-EI). Reactions were monitored with an Agilent 6890 gas chromatograph equipped with an. Agilent 7683 autosampler, HP-5 capillary column and an Agilent. 5973 mass selective detector (MSD). 300 MHz 1H NMR and.

  5. REMOVAL OF CHLORINATED ALKENE SOLVENTS FROM DRINKING WATER BY VARIOUS REVERSE OSMOSIS MEMBRANES

    Science.gov (United States)

    Historically, membranes have been used to desalinate water. As new membrane materials are developed, traditional water treatment schemes may incorporate membrane technologies, such as reverse osmosis, to address a variety of new concerns such as low molecular weight volatile org...

  6. Synthesis of novel aryl brassinosteroids through alkene cross-metathesis and preliminary biological study

    Czech Academy of Sciences Publication Activity Database

    Kořínková, Petra; Bazgier, V.; Oklešťková, Jana; Rárová, L.; Strnad, Miroslav; Kvasnica, Miroslav

    2017-01-01

    Roč. 127, NOV (2017), s. 46-55 ISSN 0039-128X R&D Projects: GA ČR GJ15-08202Y; GA MŠk(CZ) LO1204 Institutional support: RVO:61389030 Keywords : Brassinosteroids * BRI1 receptor kinase * Cross-metathesis * Molecular docking * Organic synthesis * Plant bioassays Subject RIV: CC - Organic Chemistry OBOR OECD: Organic chemistry Impact factor: 2.282, year: 2016

  7. 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...

  8. Rapid Asymmetric Transfer Hydroformylation (ATHF) of Disubstituted Alkenes Using Paraformaldehyde as a Syngas Surrogate.

    Science.gov (United States)

    Fuentes, José A; Pittaway, Rachael; Clarke, Matthew L

    2015-07-20

    As an alternative to conventional asymmetric hydroformylation (AHF), asymmetric transfer hydroformylation (ATHF) by using formaldehyde as a surrogate for syngas is reported. A catalyst derived from commercially available [Rh(acac)(CO)2 ] (acac=acetylacetonate) and 1,2-bis[(2S,5S)-2,5-diphenylphospholano]ethane(1,5-cyclooctadiene) (Ph-BPE) stands out in terms of both activity and enantioselectivity. Remarkably, not only are high selectivities achievable, the reactions are very simple to perform, and higher enantioselectivity (up to 96 % ee) and/or turnover frequencies than those achievable by using the same catalyst (or other leading catalysts) can be obtained by using typical conditions for AHF. © 2015 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

  9. Copper-Catalyzed Oxidative Dehydrogenative Carboxylation of Unactivated Alkanes to Allylic Esters via Alkenes

    Science.gov (United States)

    2015-01-01

    We report copper-catalyzed oxidative dehydrogenative carboxylation (ODC) of unactivated alkanes with various substituted benzoic acids to produce the corresponding allylic esters. Spectroscopic studies (EPR, UV–vis) revealed that the resting state of the catalyst is [(BPI)Cu(O2CPh)] (1-O2CPh), formed from [(BPI)Cu(PPh3)2], oxidant, and benzoic acid. Catalytic and stoichiometric reactions of 1-O2CPh with alkyl radicals and radical probes imply that C–H bond cleavage occurs by a tert-butoxy radical. In addition, the deuterium kinetic isotope effect from reactions of cyclohexane and d12-cyclohexane in separate vessels showed that the turnover-limiting step for the ODC of cyclohexane is C–H bond cleavage. To understand the origin of the difference in products formed from copper-catalyzed amidation and copper-catalyzed ODC, reactions of an alkyl radical with a series of copper–carboxylate, copper–amidate, and copper–imidate complexes were performed. The results of competition experiments revealed that the relative rate of reaction of alkyl radicals with the copper complexes follows the trend Cu(II)–amidate > Cu(II)–imidate > Cu(II)–benzoate. Consistent with this trend, Cu(II)–amidates and Cu(II)–benzoates containing more electron-rich aryl groups on the benzamidate and benzoate react faster with the alkyl radical than do those with more electron-poor aryl groups on these ligands to produce the corresponding products. These data on the ODC of cyclohexane led to preliminary investigation of copper-catalyzed oxidative dehydrogenative amination of cyclohexane to generate a mixture of N-alkyl and N-allylic products. PMID:25389772

  10. Measuring and predicting sooting tendencies of oxygenates, alkanes, alkenes, cycloalkanes, and aromatics on a unified scale

    Energy Technology Data Exchange (ETDEWEB)

    Das, Dhrubajyoti D.; St. John, Peter C.; McEnally, Charles S.; Kim, Seonah; Pfefferle, Lisa D.

    2018-04-01

    Databases of sooting indices, based on measuring some aspect of sooting behavior in a standardized combustion environment, are useful in providing information on the comparative sooting tendencies of different fuels or pure compounds. However, newer biofuels have varied chemical structures including both aromatic and oxygenated functional groups, which expands the chemical space of relevant compounds. In this work, we propose a unified sooting tendency database for pure compounds, including both regular and oxygenated hydrocarbons, which is based on combining two disparate databases of yield-based sooting tendency measurements in the literature. Unification of the different databases was made possible by leveraging the greater dynamic range of the color ratio pyrometry soot diagnostic. This unified database contains a substantial number of pure compounds (greater than or equal to 400 total) from multiple categories of hydrocarbons important in modern fuels and establishes the sooting tendencies of aromatic and oxygenated hydrocarbons on the same numeric scale for the first time. Using this unified sooting tendency database, we have developed a predictive model for sooting behavior applicable to a broad range of hydrocarbons and oxygenated hydrocarbons. The model decomposes each compound into single-carbon fragments and assigns a sooting tendency contribution to each fragment based on regression against the unified database. The model's predictive accuracy (as demonstrated by leave-one-out cross-validation) is comparable to a previously developed, more detailed predictive model. The fitted model provides insight into the effects of chemical structure on soot formation, and cases where its predictions fail reveal the presence of more complicated kinetic sooting mechanisms. This work will therefore enable the rational design of low-sooting fuel blends from a wide range of feedstocks and chemical functionalities.

  11. Study on the NO{sub 3} radical reactivity: Reactions with cyclic alkenes

    Energy Technology Data Exchange (ETDEWEB)

    Martinez, E.; Cabanas, B.; Aranda, A.; Martin, P.; Notario, A.; Salgado, S. [Univ. de Castilla-La Mancha, Ciudad Real (Spain). Facultad de Quimicas

    1999-07-08

    Much effort has been expended in studies of NO{sub 3} radical chemistry. The emphasis has been placed on investigating reaction rates and products of various organic and inorganic compounds to understand the behavior of this reactive radical in the atmosphere. The rate constants of the reactions of NO{sub 3} with cyclopentene, cyclohexene, cycloheptene, 1-methylcyclohexene, and methylenecyclohexane have been measured as a function of temperature at low pressure in a fast flow system with LiF detection of NO{sub 3}. The measured room temperature (298 K) rate constants for these reactions are given. The proposed Arrhenius expressions for the studied reactions are also given. The influence of substitution in the double bond and the ring size effect in unsubstituted cyclic monoalkenes has been investigated for the reactivity of the NO{sub 3} radical reactions. The rate coefficients and the activation energies for the reaction of the nitrate radical with methylenecyclohexane and 1-methylcyclohexene have also been compared with the corresponding values of some selected terpenes with similar structure to these compounds.

  12. Synthesis of Chiral Tertiary Boronic Esters: Phosphonate-Directed Catalytic Asymmetric Hydroboration of Trisubstituted Alkenes.

    Science.gov (United States)

    Chakrabarty, Suman; Takacs, James M

    2017-05-03

    Highly enantioselective rhodium-catalyzed hydroboration of allylic phosphonates by pinacolborane affords chiral tertiary boronic esters. The β-borylated phosphonates are readily converted to chiral β- and γ-hydroxyphosphonates and aminophosphonates and to phosphonates bearing a quaternary carbon stereocenter. The utility of the latter is illustrated by the synthesis of (S)-(+)-bakuchiol methyl ether.

  13. Novel polyunsaturated n-alkenes in the marine diatom Rhizosolenia setigera

    NARCIS (Netherlands)

    Damste, JSS; Rijpstra, WIC; Hopmans, EC; Peletier, H; Gieskes, WWC; Geenevasen, JAJ

    Four previously unknown n-C-25 and n-C-27 heptaenes of the marine diatom Rhizosolenia setigera were isolated and identified using NMR spectroscopy. They possess six methylene interrupted (Z)-double bonds starting at C-3 and an additional terminal or n-2 Q-double bond. Structural and stable carbon

  14. Exploring the boundaries of a light-driven molecular motor design : new sterically overcrowded alkenes with preferred direction of rotation

    NARCIS (Netherlands)

    van Delden, Richard; ter Wiel, Matthijs; de Jong, Herman; Meetsma, Auke; Feringa, Bernard

    2004-01-01

    Insight in the steric and electronic parameters governing isomerization processes in artificial molecular motors is essential in order to design more advanced motor systems. A subtle balance of steric parameters and the combination of helical and central chirality are key features of light-driven

  15. Oxidation Numbers, Oxidants, and Redox Reactions: Variants of the Electrophilic Bromination of Alkenes and Variants of the Application of Oxone

    Science.gov (United States)

    Eissen, Marco; Strudthoff, Merle; Backhaus, Solveig; Eismann, Carolin; Oetken, Gesa; Kaling, Soren; Lenoir, Dieter

    2011-01-01

    Oxidation-state and donor-acceptor concepts are important areas in the chemical education. Student worksheets containing problems that emphasize oxidation numbers, redox reactions of organic compounds, and stoichiometric reaction equations are presented. All of the examples are incorporated under one unifying topic: the production of vicinal…

  16. A combined experimental and theoretical study of the thermal [3+2] cycloaddition of carbonyl ylides with activated alkenes

    Science.gov (United States)

    Hamza-Reguig, Samira; Bentabed-Ababsa, Ghenia; Domingo, Luis R.; Ríos-Gutiérrez, Mar; Philippot, Stéphanie; Fontanay, Stéphane; Duval, Raphaël E.; Ruchaud, Sandrine; Bach, Stéphane; Roisnel, Thierry; Mongin, Florence

    2018-04-01

    4-Benzoyl-3,5-diaryltetrahydrofuran-2,2-dicarbonitriles were first synthesized from 2,2-dicyano-3-aryloxiranes and chalcones at toluene reflux; the 4,5-cis products proved to be predominantly formed and were isolated. Whereas shortened reaction times were observed by using microwave irradiation or catalytic cuprous chloride, no significant stereoselectivity change was in general noticed. Reacting 2,2-dicyano-3-aryloxiranes with 2-cyclopentenone next afforded 3-aryl-4-oxohexahydro-1H-cyclopenta[c]furan-1,1-dicarbonitriles, and the endo stereoisomers were isolated. That no stereoselectivity change was noticed in the presence of cuprous chloride rather suggests an impact of the salt on the epoxide ring opening. Finally, treatment of 2,2-dicyano-3-aryloxiranes by 2-morpholinoacrylonitrile yielded 3-cyano-3-morpholino-5-phenyltetrahydrofuran-2,2-dicarbonitriles from which the preponderant trans isomers were isolated. Importantly, the molecular mechanism of the domino reaction between 2,2-dicyano-3-phenyloxirane and 2-cyclopentenone was studied. The rate-determining thermal ring opening of the oxirane is followed by a non-concerted pseudoradical-type reaction of the carbonyl ylide with 2-cyclopentenone. Using the bond evolution theory also allowed the regioselectivity of this non-polar reaction to be explained.

  17. Metallic reductant-free synthesis of α-substituted propionic acid derivatives through hydrocarboxylation of alkenes with a formate salt.

    Science.gov (United States)

    Takaya, Jun; Miyama, Ko; Zhu, Chuan; Iwasawa, Nobuharu

    2017-04-04

    A PGeP-pincer palladium-catalyzed hydrocarboxylation of styrenes to obtain pharmaceutically important α-arylpropionic acid derivatives was achieved using a formate salt as both a reductant and a CO 2 source. The reaction was also applicable to vinylsulfone and acrylates. Isotope labeling experiments demonstrated that a CO 2 -recycling mechanism is operative through generation and reaction of a benzylpalladium complex as a carbon nucleophile. This protocol has realized a mild and atom economical CO 2 -fixation reaction without the necessity of using strong metallic reductants.

  18. Katalytické krakování vyšších alkenů

    Czech Academy of Sciences Publication Activity Database

    Kolena, J.; Morávek, P.; Bortnovskij, O.; Gonsiorová, O.; Tukač, V.; Hanika, Jiří

    2003-01-01

    Roč. 45, 3-4 (2003), s. 66-69 ISSN 1335-7727 R&D Projects: GA MŠk LN00B142 Institutional research plan: CEZ:AV0Z4072921 Keywords : higher olefins * propylene * cracking Subject RIV: CI - Industrial Chemistry, Chemical Engineering

  19. Beyond the use of modifiers in selective alkyne hydrogenation: silver and gold nanocatalysts in flow mode for sustainable alkene production

    Science.gov (United States)

    Vilé, Gianvito; Pérez-Ramírez, Javier

    2014-10-01

    We report on the excellent stereo and chemoselectivity of nanosized silver and gold catalysts in the three-phase hydrogenation of acetylenic compounds under flow chemistry conditions. The materials featuring metal nanoparticles in the range of 2-21 nm were prepared by spray deposition or incipient wetness impregnation of silver nitrate and sol immobilisation of gold chloride on different carriers (Al2O3, SiO2, TiO2, and carbon), followed by activation in various atmospheres. The samples were characterised by ICP-OES, N2 sorption, XPS, HAADF-STEM, and HRTEM, and evaluated in a continuous-flow flooded-bed micro-reactor. Both metals display optimal activities for particles below 5 nm, enabling stable operation at T = 373 K and P = 10 bar. While the performance of the silver catalysts is less influenced by the support, the gold nanoparticles exhibit significant activity only when deposited on TiO2, likely due to the strong metal-support interaction. Hydrogenations of functionalised alkynes reveal that silver and gold match, and in some cases exceed, the selectivity of benchmark palladium-based catalysts. Furthermore, in contrast to Pd, the Ag and Au samples require no modifiers, which brings fundamental and practical simplifications for their understanding and large scale manufacture. Therefore, these materials could be advantageously used for the continuous production of olefinic intermediates in the fine chemical and pharmaceutical industries.We report on the excellent stereo and chemoselectivity of nanosized silver and gold catalysts in the three-phase hydrogenation of acetylenic compounds under flow chemistry conditions. The materials featuring metal nanoparticles in the range of 2-21 nm were prepared by spray deposition or incipient wetness impregnation of silver nitrate and sol immobilisation of gold chloride on different carriers (Al2O3, SiO2, TiO2, and carbon), followed by activation in various atmospheres. The samples were characterised by ICP-OES, N2 sorption, XPS, HAADF-STEM, and HRTEM, and evaluated in a continuous-flow flooded-bed micro-reactor. Both metals display optimal activities for particles below 5 nm, enabling stable operation at T = 373 K and P = 10 bar. While the performance of the silver catalysts is less influenced by the support, the gold nanoparticles exhibit significant activity only when deposited on TiO2, likely due to the strong metal-support interaction. Hydrogenations of functionalised alkynes reveal that silver and gold match, and in some cases exceed, the selectivity of benchmark palladium-based catalysts. Furthermore, in contrast to Pd, the Ag and Au samples require no modifiers, which brings fundamental and practical simplifications for their understanding and large scale manufacture. Therefore, these materials could be advantageously used for the continuous production of olefinic intermediates in the fine chemical and pharmaceutical industries. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr02777a

  20. Rh(III)-catalyzed oxidative olefination of N-(1-naphthyl)sulfonamides using activated and unactivated alkenes.

    Science.gov (United States)

    Li, Xuting; Gong, Xue; Zhao, Miao; Song, Guoyong; Deng, Jian; Li, Xingwei

    2011-11-04

    Rhodium(III)-catalyzed oxidative olefination of N-(1-naphthyl)sulfonamides has been achieved at the peri position. Three categories of olefins have been successfully applied. Activated olefins reacted to afford five-membered azacycles as a result of oxidative olefination-hydroamination. Unactivated olefins reacted to give the olefination product. 2-fold oxidative C-C and C-N coupling was achieved for allylbenzenes. © 2011 American Chemical Society

  1. Aerobic Pd-Catalyzed sp3 C–H Olefination: A Route to Both N-Heterocyclic Scaffolds and Alkenes

    Science.gov (United States)

    Stowers, Kara J.; Fortner, Kevin C.

    2011-01-01

    This communication describes a new method for the Pd/polyoxometalate-catalyzed aerobic olefination of unactivated sp3 C–H bonds. Nitrogen heterocycles serve as directing groups, and air is used as the terminal oxidant. The products undergo reversible intramolecular Michael addition, which protects the mono-alkenylated product from over-functionalization. Hydrogenation of the Michael adducts provides access to bicyclic nitrogen-containing scaffolds that are prevalent in alkaloid natural products. Additionally, the cationic Michael adducts undergo facile elimination to release α,β-unsaturated olefins, which can be elaborated in numerous C–C and C–heteroatom bond-forming reactions. PMID:21476513

  2. Manganese porphyrin immobilized on magnetic MCM-41 nanoparticles as an efficient and reusable catalyst for alkene oxidations with sodium periodate

    Science.gov (United States)

    Hajian, Robabeh; Ehsanikhah, Amin

    2018-01-01

    This study describes the immobilization of tetraphenylporphyrinatomanganese(III) chloride, (MnPor), onto imidazole functionalized MCM-41 with magnetite nanoparticle core (Fe3O4@MCM-41-Im). The resultant material (Fe3O4@MCM-41-Im@MnPor) was characterized by X-ray diffractometry (XRD), Fourier transform infra-red (FT-IR), diffuse reflectance UV-Vis spectrophotometry (DR UV-Vis), field emission scanning electron microscopy (FESEM), Inductively coupled plasma (ICP), analyzer transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) surface area. This new heterogenized catalyst was applied as an efficient catalyst for the epoxidation of a variety of cyclic and linear olefins with NaIO4 under mild conditions. The prepared catalyst can be easily recovered through the application of an external magnet, and reused several times without any significant decrease in activity and magnetic properties.

  3. Bifunctional Molecular Photoswitches Based on Overcrowded Alkenes for Dynamic Control of Catalytic Activity in Michael Addition Reactions

    NARCIS (Netherlands)

    Pizzolato, Stefano F.; Collins, Beatrice S. L.; van Leeuwen, Thomas; Feringa, Ben L.

    2017-01-01

    The emerging field of artificial photoswitchable catalysis has recently shown striking examples of functional light-responsive systems allowing for dynamic control of activity and selectivity in organocatalysis and metal-catalysed transformations. While our group has already disclosed systems

  4. Construction of dispirocyclohexanes via amine-catalyzed [2 + 2 + 2] annulations of Morita-Baylis-Hillman acetates with exocyclic alkenes.

    Science.gov (United States)

    Chen, Rongshun; Xu, Silong; Fan, Xia; Li, Hanyuan; Tang, Yuhai; He, Zhengjie

    2015-01-14

    Amine-catalyzed [2 + 2 + 2] annulations of one molecule of Morita-Baylis-Hillman (MBH) acetates 1 with two molecules of 2-(arylmethylidene)indane-1,3-diones 2 or methyleneindolinones 4 have been developed under very mild conditions, which produce multistereogenic dispirocyclohexanes 3 and 5, respectively, in moderate to excellent yields and good diastereoselectivity. This amine-catalyzed annulation constitutes a novel and efficient method for the construction of dispirocyclohexane motifs, and also showcases the divergent catalysis between amines and phosphines with regard to the corresponding phosphine-catalyzed [3 + 2] annulations.

  5. Influences of the molecular fuel structure on combustion reactions towards soot precursors in selected alkane and alkene flames.

    Science.gov (United States)

    Ruwe, Lena; Moshammer, Kai; Hansen, Nils; Kohse-Höinghaus, Katharina

    2018-04-25

    In this study, we experimentally investigate the high-temperature oxidation kinetics of n-pentane, 1-pentene and 2-methyl-2-butene (2M2B) in a combustion environment using flame-sampling molecular beam mass spectrometry. The selected C5 fuels are prototypes for linear and branched, saturated and unsaturated fuel components, featuring different C-C and C-H bond structures. It is shown that the formation tendency of species, such as polycyclic aromatic hydrocarbons (PAHs), yielded through mass growth reactions increases drastically in the sequence n-pentane fuel-dependent reaction sequences of the gas-phase combustion mechanism that provide explanations for the observed difference in the PAH formation tendency. First, we investigate the fuel-structure-dependent formation of small hydrocarbon species that are yielded as intermediate species during the fuel decomposition, because these species are at the origin of the subsequent mass growth reaction pathways. Second, we review typical PAH formation reactions inspecting repetitive growth sequences in dependence of the molecular fuel structure. Third, we discuss how differences in the intermediate species pool influence the formation reactions of key aromatic ring species that are important for the PAH growth process underlying soot formation. As a main result it was found that for the fuels featuring a C[double bond, length as m-dash]C double bond, the chemistry of their allylic fuel radicals and their decomposition products strongly influences the combination reactions to the initially formed aromatic ring species and as a consequence, the PAH formation tendency.

  6. Mechanistic Insights of a Selective C-H Alkylation of Alkenes by a Ru-based Catalyst and Alcohols

    KAUST Repository

    Poater, Albert

    2016-09-11

    Density functional theory calculations have been used to investigate the reaction mechanism for [(C6H6)(PCy3)(CO) RuH](+) (1; Cy, cyclohexyl) mediated alkylation of indene substrate using ethanol as solvent. According to Yi et al. [ Science 2011, 333, 1613] the plausible reaction mechanism involves a cationic Rualkenyl species, which is initially formed from 1 with two equivalents of the olefin substrate via the vinylic C-H activation and an alkane elimination step. Once the active catalytic species is achieved the oxidative addition step is faced. The latter step together with the next C-C bond formation might display the upper barrier of the catalytic cycle. Having these experimental insights at hand, we investigated in detail the whole reaction pathway using several computational DFT approaches including alternative pathways, higher in energy.

  7. Measurements of a potential interference with laser-induced fluorescence measurements of ambient OH from the ozonolysis of biogenic alkenes

    Science.gov (United States)

    Rickly, Pamela; Stevens, Philip S.

    2018-01-01

    Reactions of the hydroxyl radical (OH) play a central role in the chemistry of the atmosphere, and measurements of its concentration can provide a rigorous test of our understanding of atmospheric oxidation. Several recent studies have shown large discrepancies between measured and modeled OH concentrations in forested areas impacted by emissions of biogenic volatile organic compounds (BVOCs), where modeled concentrations were significantly lower than measurements. A potential reason for some of these discrepancies involves interferences associated with the measurement of OH using the laser-induced fluorescence-fluorescence assay by gas expansion (LIF-FAGE) technique in these environments. In this study, a turbulent flow reactor operating at atmospheric pressure was coupled to a LIF-FAGE cell and the OH signal produced from the ozonolysis of α-pinene, β-pinene, ocimene, isoprene, and 2-methyl-3-buten-2-ol (MBO) was measured. To distinguish between OH produced from the ozonolysis reactions and any OH artifact produced inside the LIF-FAGE cell, an external chemical scrubbing technique was used, allowing for the direct measurement of any interference. An interference under high ozone (between 2 × 1013 and 10 × 1013 cm-3) and BVOC concentrations (between approximately 0.1 × 1012 and 40 × 1012 cm-3) was observed that was not laser generated and was independent of the ozonolysis reaction time. For the ozonolysis of α- and β-pinene, the observed interference accounted for approximately 40 % of the total OH signal, while for the ozonolysis of ocimene the observed interference accounted for approximately 70 % of the total OH signal. Addition of acetic acid to the reactor eliminated the interference, suggesting that the source of the interference in these experiments involved the decomposition of stabilized Criegee intermediates (SCIs) inside the FAGE detection cell. Extrapolation of these measurements to ambient concentrations suggests that these interferences should be below the detection limit of the instrument.

  8. Effect of multi-walled carbon nanotubes aspect ratio and temperature on the dielectric behavior of alternating alkene-carbon monoxide polyketone nanocomposites

    Science.gov (United States)

    Abu-Surrah, Adnan S.; Abdul Jawad, Saadi; Al-Ramahi, Esraa; Hallak, Awni B.; Khattari, Z.

    2015-04-01

    New alternating poly(propylene-alt-carbon monoxide/ethylene-alt-carbon monoxide) (PECO)/multiwalled carbon nanotubes (MWCNTs) composites have been prepared. Dielectric permittivity, electric modulus and ac conductivity of the isolated materials were investigated as a function of fiber aspect ratio, frequency and temperature. For aspect ratio of 30 and 200, a transition from insulator to semiconductor was observed at frequency 1×104. However, for high aspect ratio sample (660), no transition was observed and the conductivity is frequency independent in the measured frequency range of 10-106 Hz. The conductivity increases from about 1×10-4 for the sample that contain fibers of aspect ratio 30 and reaches 5×10-2 (Ω m)-1 for aspect ratio was 660. This behavior can be modeled by a circuit that consists of a contact resistance in series with a parallel combination of resistance (R) and capacitance (C). The calculated activation energy for sample filled with fibers having aspect ratio 30 is about 0.26 eV and decreases to about 0.16 eV when the aspect ratio is 660.

  9. 40 CFR 721.6900 - Polymer of bisphenol A di-glyc-i-dal ether, substituted al-kenes, and but-a-diene.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Polymer of bisphenol A di-glyc-i-dal... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.6900 Polymer of bisphenol A di-glyc-i... subject to reporting. (1) The chemical substances identified generically as polymer of bisphenol A...

  10. Development of (2-bromo-1,1,2,2-tetrafluoroethyl)(phenyl)sulfane as tetrafluoroethyl-radical and tetrafluoroethylene-diradical synthons for additions to alkenes

    Czech Academy of Sciences Publication Activity Database

    Chernykh, Yana; Beier, Petr

    2013-01-01

    Roč. 156, December (2013), s. 307-313 ISSN 0022-1139 R&D Projects: GA ČR GAP207/11/0421 Institutional support: RVO:61388963 Keywords : radical addition * sulfide * tetrafluoroethyl * tetrafluoroethylene Subject RIV: CC - Organic Chemistry Impact factor: 1.952, year: 2013

  11. The isolation of [Pd{OC(O)H}(H)(NHC)(PR3)] (NHC = N-heterocyclic carbene) and its role in alkene and alkyne reductions using formic acid

    KAUST Repository

    Broggi, Julie

    2013-03-27

    The [Pd(SIPr)(PCy3)] complex efficiently promotes a tandem process involving dehydrogenation of formic acid and hydrogenation of C-C multiple bonds using H2 formed in situ. The isolation of a key catalytic hydridoformatopalladium species, [Pd{OC(O)H}(H)(IPr)(PCy 3)], is reported. The complex plays a key role in the Pd(0)-mediated formation of hydrogen from formic acid. Mechanistic and computational studies delineate the operational role of the palladium complex in this efficient tandem sequence. © 2013 American Chemical Society.

  12. Formation of highly oxidized multifunctional compounds: autoxidation of peroxy radicals formed in the ozonolysis of alkenes - deduced from structure-product relationships

    Science.gov (United States)

    Mentel, T. F.; Springer, M.; Ehn, M.; Kleist, E.; Pullinen, I.; Kurtén, T.; Rissanen, M.; Wahner, A.; Wildt, J.

    2015-06-01

    It has been postulated that secondary organic particulate matter plays a pivotal role in the early growth of newly formed particles in forest areas. The recently detected class of extremely low volatile organic compounds (ELVOC) provides the missing organic vapors and possibly contributes a significant fraction to atmospheric SOA (secondary organic aerosol). The sequential rearrangement of peroxy radicals and subsequent O2 addition results in ELVOC which are highly oxidized multifunctional molecules (HOM). Key for efficiency of such HOM in early particle growth is that their formation is induced by one attack of the oxidant (here O3), followed by an autoxidation process involving molecular oxygen. Similar mechanisms were recently observed and predicted by quantum mechanical calculations e.g., for isoprene. To assess the atmospheric importance and therewith the potential generality, it is crucial to understand the formation pathway of HOM. To elucidate the formation path of HOM as well as necessary and sufficient structural prerequisites of their formation we studied homologous series of cycloalkenes in comparison to two monoterpenes. We were able to directly observe highly oxidized multifunctional peroxy radicals with 8 or 10 O atoms by an Atmospheric Pressure interface High Resolution Time of Flight Mass Spectrometer (APi-TOF-MS) equipped with a NO3--chemical ionization (CI) source. In the case of O3 acting as an oxidant, the starting peroxy radical is formed on the so-called vinylhydroperoxide path. HOM peroxy radicals and their termination reactions with other peroxy radicals, including dimerization, allowed for analyzing the observed mass spectra and narrowing down the likely formation path. As consequence, we propose that HOM are multifunctional percarboxylic acids, with carbonyl, hydroperoxy, or hydroxy groups arising from the termination steps. We figured that aldehyde groups facilitate the initial rearrangement steps. In simple molecules like cycloalkenes, autoxidation was limited to both terminal C atoms and two further C atoms in the respective α positions. In more complex molecules containing tertiary H atoms or small, constrained rings, even higher oxidation degrees were possible, either by simple H shift of the tertiary H atom or by initialization of complex ring-opening reactions.

  13. Metallacyclobutane substitution and its effect on alkene metathesis for propylene production over W-H/Al2O3: Case of isobutene/2-butene cross-metathesis

    KAUST Repository

    Szeto, Kaï Chung

    2013-09-06

    Cross metathesis between 2-butenes and isobutene yielding the valuable products propylene and 2-methyl-2-butene has been investigated at low pressure and temperature using WH3/Al2O3, a highly active and selective catalyst. Two parallel catalytic cycles for this reaction have been proposed where the cycle involving the less sterically hindered tungstacyclobutane intermediates is most likely favored. Moreover, it has been found that the arrangement of substituents on the least thermodynamically favored tungstacyclobutane governs the conversion rate of the cross metathesis reaction for propylene production from butenes and/or ethylene. © 2013 American Chemical Society.

  14. Rate acceleration of the heterogeneous reaction of ozone with a model alkene at the air-ice interface at low temperatures.

    Science.gov (United States)

    Ray, Debajyoti; Malongwe, Joseph K'Ekuboni; Klán, Petr

    2013-07-02

    The kinetics of the ozonation reaction of 1,1-diphenylethylene (DPE) on the surface of ice grains (also called "artificial snow"), produced by shock-freezing of DPE aqueous solutions or DPE vapor-deposition on pure ice grains, was studied in the temperature range of 268 to 188 K. A remarkable and unexpected increase in the apparent ozonation rates with decreasing temperature was evaluated using the Langmuir-Hinshelwood and Eley-Rideal kinetic models, and by estimating the apparent specific surface area of the ice grains. We suggest that an increase of the number of surface reactive sites, and possibly higher ozone uptake coefficients are responsible for the apparent rate acceleration of DPE ozonation at the air-ice interface at lower temperatures. The increasing number of reactive sites is probably related to the fact that organic molecules are displaced more to the top of a disordered interface (or quasi-liquid) layer on the ice surface, which makes them more accessible to the gas-phase reactants. The effect of NaCl as a cocontaminant on ozonation rates was also investigated. The environmental implications of this phenomenon for natural ice/snow are discussed. DPE was selected as an example of environmentally relevant species which can react with ozone. For typical atmospheric ozone concentrations in polar areas (20 ppbv), we estimated that its half-life on the ice surface would decrease from ∼5 days at 258 K to ∼13 h at 188 K at submonolayer DPE loadings.

  15. Group 11 Metal Compounds with Tripodal Bis(imidazole Thioether Ligands. Applications as Catalysts in the Oxidation of Alkenes and as Antimicrobial Agents

    Directory of Open Access Journals (Sweden)

    Armando Varela-Ramírez

    2011-08-01

    Full Text Available New group 11 metal complexes have been prepared using the previously described tripodal bis(imidazole thioether ligand (N-methyl-4,5-diphenyl-2-imidazolyl2C(OMeC(CH32S(tert-Bu ({BITOMe,StBu}, 2. The pincer ligand offers a N2S donor atom set that can be used to coordinate the group 11 metals in different oxidation states [AuI, AuIII, AgI, CuI and CuII]. Thus the new compounds [Au{BITOMe,StBu}Cl][AuCl4]2 (3, [Au{BITOMe,StBu}Cl] (4, [Ag{BITOMe,StBu}X] (X = OSO2CF3- 5, PF6- 6 and [Cu{BITOMe,StBu}Cl2] (7 have been synthesized from reaction of 2 with the appropriate metal precursors, and characterized in solution. While attempting characterization in the solid state of 3, single crystals of the neutral dinuclear mixed AuIII-AuI species [Au2{BITOMe,S}Cl3] (8 were obtained and its crystal structure was determined by X-ray diffraction studies. The structure shows a AuIII center coordinated to the pincer ligand through one N and the S atom. The soft AuI center coordinates to the ligand through the same S atom that has lost the tert-butyl group, thus becoming a thiolate ligand. The short distance between the AuI-AuIII atoms (3.383 Å may indicate a weak metal-metal interaction. Complexes 2-7 and the previously described CuI compound [Cu{BITOMe,StBu}]PF6 (9 have been evaluated in the oxidation of biphenyl ethylene with tert-butyl hydrogen peroxide (TBHP as the oxidant. Results have shown that the AuI and AgI complexes 4 and 6 (at 10 mol % loading are the more active catalysts in this oxidative cleavage. The antimicrobial activity of compounds 2-5, 7 and 9 against Gram-positive and Gram-negative bacteria and yeast has also been evaluated. The new gold and silver compounds display moderate to high antibacterial activity, while the copper derivatives are mostly inactive. The gold and silver complexes were also potent against fungi. Their cytotoxic properties have been analyzed in vitro utilizing HeLa human cervical carcinoma cells. The compounds displayed a very low cytotoxicity on this cell line (5 to 10 times lower than cisplatin and on normal primary cells derived from C57B6 mouse muscle explants, which may make them promising candidates as potential antimicrobial agents and safer catalysts due to low toxicity in human and other mammalian tissues.

  16. Cobalt dinitrosoalkane complexes in the C-H functionalization of olefins.

    Science.gov (United States)

    Schomaker, Jennifer M; Boyd, W Christopher; Stewart, Ian C; Toste, F Dean; Bergman, Robert G

    2008-03-26

    The use of cobalt dinitrosoalkane complexes in the C-H functionalization of alkenes has been demonstrated. Reaction of a series of alkenes with Me4CpCo(CO)2 in the presence of NO generates intermediate cobalt dinitrosoalkane complexes that can be deprotonated alpha to the nitrosyl group and added to various Michael acceptors. The resultant products can then undergo retrocycloaddition reactions in the presence of the original alkene to regenerate the starting cobalt dinitrosoalkane complex and release the functionalized alkene.

  17. Palladium-catalyzed C-H olefination of uracils and caffeines using molecular oxygen as the sole oxidant.

    Science.gov (United States)

    Zhang, Xinyu; Su, Lv; Qiu, Lin; Fan, Zhenwei; Zhang, Xiaofeng; Lin, Shen; Huang, Qiufeng

    2017-04-18

    The palladium-catalyzed oxidative C-H olefination of uracils or caffeines with alkenes using an atmospheric pressure of molecular oxygen as the sole oxidant has been disclosed. This novel strategy offers an efficient and environmentally friendly method to biologically important C5-alkene uracil derivatives or C8-alkene caffeine derivatives.

  18. Synthesis and Characterization of Bis-benzyl and Bis-allyl Complexes of Titanium(III) and Vanadium(III); Catalytic Isomerization of Alkenes with CpV(η3-C3H5)2

    NARCIS (Netherlands)

    Nieman, J.; Pattiasina, J.W.; Teuben, J.H.

    1984-01-01

    Reactions of CpTiCl2 (Cp = η5-C5H5) with RMgX (X = Cl, Br) yield the complexes CpTiR2 (R = CH2Ph, η3-C3H5). The complex Cp*Ti(η3-C3H5)2 (Cp* = η5-C5Me5) was prepared analogously from Cp*TiCl2(THF). CpVCl2(PEt3)2 and Cp´VCl2(PEt3)2 (Cp´ = η5-C5H4Me) were used for the preparation of CpV(CH2Ph)2,

  19. Alkene insertion reactions of nitrogen-coordinated acylpalladium(II) complexes : the X-ray structure of the dicyclopentadiene insertion product [Pd(C20H23COMe)(bpy)]SO3CF3

    NARCIS (Netherlands)

    Koten, G. van; Markies, B.A.; Rietveld, M.H.P.; Boersma, J.; Spek, A.L.

    1992-01-01

    The new acylpalladium(II) complex [PdI(COMe)(bpy)] (2b, bpy = 2, 2'-bipyridyl) has been obtained by two routes; (i) by insertion of carbon monoxide into the Pd@?C bond of [PdIMe(bpy)] (1b), and (ii) by ligand exchange from [PdI(COMe)(tmeda)] (2a, tmeda = N,N,N',N'-tetramethylethanediamine). The

  20. Alkene hydrogenation activity of enoate reductases for an environmentally benign biosynthesis of adipic acid† †Electronic supplementary information (ESI) available. See DOI: 10.1039/c6sc02842j Click here for additional data file.

    Science.gov (United States)

    Khusnutdinova, Anna N.; Flick, Robert; Kim, Taeho; Bornscheuer, Uwe T.

    2017-01-01

    Adipic acid, a precursor for Nylon-6,6 polymer, is one of the most important commodity chemicals, which is currently produced from petroleum. The biosynthesis of adipic acid from glucose still remains challenging due to the absence of biocatalysts required for the hydrogenation of unsaturated six-carbon dicarboxylic acids to adipic acid. Here, we demonstrate the first enzymatic hydrogenation of 2-hexenedioic acid and muconic acid to adipic acid using enoate reductases (ERs). ERs can hydrogenate 2-hexenedioic acid and muconic acid producing adipic acid with a high conversion rate and yield in vivo and in vitro. Purified ERs exhibit a broad substrate spectrum including aromatic and aliphatic 2-enoates and a significant oxygen tolerance. The discovery of the hydrogenation activity of ERs contributes to an understanding of the catalytic mechanism of these poorly characterized enzymes and enables the environmentally benign biosynthesis of adipic acid and other chemicals from renewable resources. PMID:28616142

  1. Intermolecular Dehydrative Coupling Reaction of Arylketones with Cyclic Alkenes Catalyzed by a Well-Defined Cationic Ruthenium-Hydride Complex: A Novel Ketone Olefination Method via Vinyl C–H Bond Activation

    Science.gov (United States)

    Yi, Chae S.; Lee, Do W.

    2010-01-01

    Summary The cationic ruthenium-hydride complex [(η6-C6H6)(PCy3)(CO)RuH]+BF4− was found to be a highly effective catalyst for the intermolecular olefination reaction of arylketones with cycloalkenes. The preliminary mechanistic analysis revealed that electrophilic ruthenium-vinyl complex is the key species for mediating both vinyl C–H bond activation and the dehydrative olefination steps of the coupling reaction. PMID:20567607

  2. Maghemite decorated with ultra-small palladium nanoparticles (γ-Fe2O3–Pd): applications in the Heck–Mizoroki olefination, Suzuki reaction and allylic oxidation of alkenes

    Science.gov (United States)

    A nanocatalyst comprising ultra-small Pd/PdO nanoparticles (<5 nm) supported on maghemite was prepared by a co-precipitation protocol using inexpensive raw materials and was deployed successfully in various significant synthetic transformations, namely the Heck–Mizoroki olefinati...

  3. Regio- and stereoselective synthesis of pregnane-fused isoxazolines by nitril-oxide/alkene 1,3-dipolar cycloaddition and an evaluation of their cell-growth inhibitory effect in vitro

    Science.gov (United States)

    Mótyán, Gergő; Baji, Ádám; Zupkó, István; Frank, Éva

    2016-04-01

    Efficient syntheses of some pregnane-fused isoxazolines from 16-dehydropregnenolone acetate with different arylnitrile oxides were carried out by 1,3-dipolar cycloadditions. The intermolecular ring-closures occurred in a highly regio- and stereoselective manner permitting the formation of a single 16α,17α-condensed diastereomer in which the O terminus of the nitrile oxide dipole is attached to C-17 of the sterane core. The conversions were found to be affected significantly by the electronic character of the substituents on the aromatic moiety of the 1,3-dipoles. Deacetylation of the primary products resulted in the corresponding 3β-OH analogs. All of the synthesized compounds were subjected to in vitro pharmacological studies for the determination of their antiproliferative effects on four breast cancer cell lines (MCF7, T47D, MDA-MB-231 and MDA-MB-361).

  4. Kinetics and mechanism of the oxidation of alkenes and silanes by hydrogen peroxide catalyzed by methylrhenium trioxide (MTO) and a novel application of electrospray mass spectrometry to study the hydrolysis of MTO

    Energy Technology Data Exchange (ETDEWEB)

    Tan, Haisong [Iowa State Univ., Ames, IA (United States)

    1999-11-08

    Conjugated dienes were oxidized by hydrogen peroxide with methylrhenium trioxide (MTO) as catalyst. Methylrhenium bis-peroxide was the major reactive catalyst present. Hydroxyalkenes and trisubstituted silane were also tested. Mechanisms for each of these reactions are presented.

  5. Photochemical reaction dynamics of 2,2'-dithiobis(benzothiazole): direct observation of the addition product of an aromatic thiyl radical to an alkene with time-resolved vibrational and electronic absorption spectroscopy.

    Science.gov (United States)

    Koyama, Daisuke; Orr-Ewing, Andrew J

    2016-04-28

    The photochemical reaction dynamics of the benzothiazole-2-thiyl (BS) radical, produced by 330 nm ultraviolet photolysis of 2,2'-dithiobis(benzothiazole) (BSSB), are examined on the picosecond time scale. The initial addition product of a thiol-ene reaction between the BS radical and styrene is directly observed by transient vibrational absorption spectroscopy (TVAS). Transient electronic absorption spectroscopy (TEAS) in the ultraviolet and visible spectral regions reveals rapid formation of the ground state BS radical with a time constant of ∼200 fs. The photolytically generated BS radical decays through geminate recombination to the parent molecule BSSB and competitive formation of a BS radical dimer with a rate coefficient of (3.7 ± 0.2) × 10(10) M(-1) s(-1) in methanol, and thereafter (36 ± 1)% of the initially formed BS radicals survive at the longest time delay (1.3 ns). In styrene solution, in contrast to methanol and toluene solutions, kinetic traces of the BS radical show an additional decay with a time constant of 305 ± 13 ps, and a broad band at 345-500 nm grows with the same time constant, suggesting a bimolecular reaction of the BS radical with styrene. The TVAS measurements reveal an absorption band of the ground state BS radical at 1301 cm(-1) in toluene solution, and the band decays with a time constant of 294 ± 32 ps in styrene solution. Two product bands grow at 1239 cm(-1) and 1429 cm(-1) with respective time constants of 312 ± 68 ps and 325 ± 33 ps, and are attributed to the addition product BS-St radical formed from the BS radical and styrene. A bimolecular reaction rate coefficient of kreact = (3.8 ± 0.2) × 10(8) M(-1) s(-1) is deduced and 22 ± 1% of the initially formed BS radicals are converted to the BS-St radical in neat styrene solution.

  6. Thermoset polymers via ring opening metathesis polymerization of functionalized oils

    Science.gov (United States)

    Larock, Richard C; Henna, Phillip H; Kessier, Michael R

    2012-11-27

    The invention provides a method for producing a thermosetting resin from renewable oils, the method comprising supplying renewable oil molecules containing strained ring alkene moieties; reacting the alkene moieties with cyclic alkenes to create a polymer; and repeating the above two steps until the resin having desired characteristics are obtained. Also provided is a thermoset resin comprising functionalized renewable oil polymerized with a co-monomer.

  7. Organic synthesis

    Energy Technology Data Exchange (ETDEWEB)

    Thomas, S.E.

    1991-01-01

    This paper reports on reactions of organoboranes. Organoboron routes to unsaturated hydrocarbons. Boronic ester homologation. Properties of organosilicon compounds. Alkene synthesis (Peterson olefination). Allylsilanes and acylsilanes.

  8. Fulltext PDF

    Indian Academy of Sciences (India)

    The addition of free nitrenes to alkene substrates is studied using DFT and MP2 methods. The B3LYP results predict that concerted azide decomposition can yield singlet nitrenes, unlike the MP2 results. Singlet nitrenes insert into alkenes with a modest or no barrier. Triplet nitrenes employ a step-wise pathway to give ...

  9. Factors influencing ring closure through olefin metathesis-A ...

    Indian Academy of Sciences (India)

    Success of ring closure reactions of substrates having two terminal alkenes through olefin metathesis depends on a number of factors such as catalysts, nature and size of the rings to be formed and the substituents/functional groups present on the alkenes as well as at the allylic position. This article presents an overview of ...

  10. dichlorodiazene dioxides using levulinic acid under solvent-free ...

    Indian Academy of Sciences (India)

    Administrator

    preparation of these compounds starting from alkenes adopting the Green Chemistry principle of solvent- free reaction. The procedure involves addition of NOCl generated in situ by the reaction of AcOH–HCl. (3 :1) with amyl nitrite to alkenes and treating the α-chloronitroso compounds obtained as dimers with levulinic acid ...

  11. Water Mediated Wittig Reactions of Aldehydes in the Teaching Laboratory: Using Sodium Bicarbonate for the in Situ Formation of Stabilized Ylides

    Science.gov (United States)

    Kelly, Michael J. B.; Fallot, Lucas B.; Gustafson, Jeffrey L.; Bergdahl, B. Mikael

    2016-01-01

    The synthesis of alkenes using the Wittig reaction is a traditional part of many undergraduate organic chemistry teaching laboratory curricula. The aqueous medium version of the Wittig reaction presented is a reliable adaptation of this alkene formation reaction as a very safe alternative in the introductory organic chemistry laboratory. The…

  12. CHEMISTRY OF THIENOPYRIDINES .39. SYNTHESIS OF [1]BENZOTHIENO[2,3-H]ISOQUINOLINE AND RELATED STUDIES

    NARCIS (Netherlands)

    KLEMM, LH; SEVERNS, B; WYNBERG, H

    Benzo[b]thiophene-2-carboxaldehyde undergoes condensation with 4-methylpyridine and with 2-methylquinoline to produce trans-diarylethenes (52% and 76%, respectively). The former alkene photocyclizes in cyclohexane to yield [1]benzo[2,3-h]isoquinoline (35%), while the latter alkene does not give

  13. Preparation of different amides via Ritter reaction from alcohols and ...

    Indian Academy of Sciences (India)

    Ritter reaction; SBNPSA; alcohol; nitrile; amide. 1. Introduction. The conversion of nitriles to amides by reaction with alcohols or alkenes in the presence of sulphuric acid is named Ritter reaction. Acidification of the appro- priate alcohol or alkene generates a carbenium ion which reacts with nitrile. While the successful ...

  14. EFSA CEF Panel (EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids), 2013. Scientific Opinion on Flavouring Group Evaluation 216, Revision 1 (FGE.216Rev1). Consideration of genotoxic potential for α,β-unsaturated 2-Phenyl -2-Alkenals from Subgroup 3.3 of FGE.19

    DEFF Research Database (Denmark)

    Beltoft, Vibe Meister; Binderup, Mona-Lise; Lund, Pia

    The Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids of the European Food Safety Authority was requested to evaluate the genotoxic potential of five flavouring substances from subgroup 3.3 of FGE.19. In the Flavouring Group Evaluation 216 (FGE.216) additional genotoxicity...... data were requested. Additional genotoxicity studies have now been provided for the representative substance 2-phenylcrotonaldehyde [FL-no: 05.062]. Based on these new data the Panel concluded that the concern for genotoxicity could not be ruled out and requests a proof of sufficient systemic exposure...

  15. A cw EPR and ENDOR investigation on a series of Cr(I) carbonyl complexes with relevance to alkene oligomerization catalysis: [Cr(CO)4L]+ (L = Ph2PN(R)PPh2, Ph2P(R)PPh2).

    Science.gov (United States)

    McDyre, Lucia E; Hamilton, Tracy; Murphy, Damien M; Cavell, Kingsley J; Gabrielli, William F; Hanton, Martin J; Smith, David M

    2010-09-07

    The preparation and characterisation of the Cr(I) complexes [Cr(CO)(4)L](+) (L = Ph(2)PN(R)PPh(2), Ph(2)P(R)PPh(2)), which are used as pre-catalysts for the selective oligomerization of ethylene, are reported. The electronic properties and structural features of these complexes in frozen solution have been established via continuous wave X-band Electron Paramagnetic Resonance (cw-EPR) and continuous wave (1)H, (14)N and (31)P Electron Nuclear Double Resonance (cw-ENDOR) spectroscopy. The EPR spectra are dominated by the g anisotropy, with notably large (P)A couplings from the two equivalent (31)P nuclei. The spin Hamiltonian parameters (g(perpendicular) (g(xx) = g(yy)) > g(e) > g(parallel) (g(zz))) are consistent with a low-spin d(5) system possessing C(2v) symmetry, with a SOMO where the metal contribution is primarily d(xy) for all complexes. The isotropic Fermi contact term ((P)a(iso), determined by EPR and ENDOR) was found to be largest for complexes containing ligands e, d, f and g, indicating that the (31)P 3 s character in the SOMO is higher for the PNP type ligands than the PCP type. Subtle structural differences in the complexes were also identified through variations in the Deltag shifts (identified by EPR), and through differences in the phenyl ring conformations (identified by (1)H ENDOR). Attempts to correlate trends in EPR-derived parameters with data measured for catalysis using these pre-catalysts are also made, but no clear connections were found.

  16. Stearoyl-acyl carrier protein desaturases are associated with floral isolation in sexually deceptive orchids

    Energy Technology Data Exchange (ETDEWEB)

    Schluter, P.M.; Shanklin, J.; Xu, S.; Gagliardini, V.; Whittle, E.; Grossniklaus, U.; Schiestl, F. P.

    2011-04-05

    The orchids Ophrys sphegodes and O. exaltata are reproductively isolated from each other by the attraction of two different, highly specific pollinator species. For pollinator attraction, flowers chemically mimic the pollinators sex pheromones, the key components of which are alkenes with different double-bond positions. This study identifies genes likely involved in alkene biosynthesis, encoding stearoyl-acyl carrier protein (ACP) desaturase (SAD) homologs. The expression of two isoforms, SAD1 and SAD2, is flower-specific and broadly parallels alkene production during flower development. SAD2 shows a significant association with alkene production, and in vitro assays show that O. sphegodes SAD2 has activity both as an 18:0-ACP {Delta}{sup 9} and a 16:0-ACP {Delta}{sup 4} desaturase. Downstream metabolism of the SAD2 reaction products would give rise to alkenes with double-bonds at position 9 or position 12, matching double-bond positions observed in alkenes in the odor bouquet of O. sphegodes. SAD1 and SAD2 show evidence of purifying selection before, and positive or relaxed purifying selection after gene duplication. By contributing to the production of species-specific alkene bouquets, SAD2 is suggested to contribute to differential pollinator attraction and reproductive isolation among these species. Taken together, these data are consistent with the hypothesis that SAD2 is a florally expressed barrier gene of large phenotypic effect and, possibly, a genic target of pollinator-mediated selection.

  17. Subnanometer-sized Pt/Sn alloy cluster catalysts for the dehydrogenation of linear alkanes.

    Science.gov (United States)

    Hauser, Andreas W; Gomes, Joseph; Bajdich, Michal; Head-Gordon, Martin; Bell, Alexis T

    2013-12-21

    The reaction pathways for the dehydrogenation of ethane, propane, and butane, over Pt are analyzed using density functional theory (DFT). Pt nanoparticles are represented by a tetrahedral Pt4 cluster. The objectives of this work were to establish which step is rate limiting and which one controls the selectivity for forming alkenes as opposed to causing further dehydrogenation of adsorbed alkenes to produce precursors responsible for catalyst deactivation due to coking. Further objectives of this work are to identify the role of adsorbed hydrogen, derived from H2 fed together with the alkane, on the reaction pathway, and the role of replacing one of the four Pt atoms by a Sn atom. A comparison of Gibbs free energies shows that in all cases the rate-determining step is cleavage of a C-H bond upon alkane adsorption. The selectivity to alkene formation versus precursors to coking is dictated by the relative magnitudes of the activation energies for alkene desorption and dehydrogenation of the adsorbed alkene. The presence of an adsorbed H atom on the cluster facilitates alkene desorption relative to dehydrogenation of the adsorbed alkene. Substitution of a Sn atom in the cluster to produce a Pt3Sn cluster leads to a downward shift of the potential energy surface for the reaction and causes an increase of the activity of the catalyst as suggested by recent experiments due to the lower net activation barrier for the rate limiting step. However, the introduction of Sn does not alter the relative activation barriers for gas-phase alkene formation versus loss of hydrogen from the adsorbed alkene, the process leading to the formation of coke precursors.

  18. Homogeneous catalysis by transition metals

    International Nuclear Information System (INIS)

    Masters, K.

    1983-01-01

    Fundamentals of homogeneous catalysis by metal complex aAe presented in the monograph along with the mechanisms of practically all types of catalytic reactions proceeding in the presence of transition metal complexes. In particular, considered are: catalytic cycles for olefin hydrogenation in the presence of Ru(2) complex; for alkene epoxidation catalyzed by Mo(6); for alkene metathesis reaction catalyzed by Ta and W compounds. Catalytic systems on the basis of Zr, Mo, W, Ru complexes being in the stage of development of the processes of nitrogen fixation reductive oligomerization alkene activation are described. Bibliography contains more than 400 references

  19. Polysiloxane-based lacquer binding agent suited for electron radiation hardening

    International Nuclear Information System (INIS)

    Johnson, O.B.; Nordstrom, J.D.

    1976-01-01

    The binding agent has a high degree of weather resistance and is suitable for use in varnishes and paints applied to wood, metals and plastics. It consists of 20-90% by weight of an alkene-unsaturated reaction product of a polysiloxane and 10-80% by weight of another alkene-unsaturated compound. The reaction product of polysiloxane is produced by etherisation of the polysiloxane with a hydroxyester of an α,β-alkene-unsaturated carboxylic acid and the other component may be an unsaturated epoxy resin, an unsaturated diurethane, or an unsaturated copolymer of vinyl monomers, preferably together with one or more vinyl monomers. (JIW)

  20. Oxidative Reactions with Nonaqueous Enzymes

    Energy Technology Data Exchange (ETDEWEB)

    Jonathan S. Dordick; Douglas Clark; Brian H Davison; Alexander Klibanov

    2001-12-30

    The objective of this work is to demonstrate a proof-of-concept of enzymatic oxidative processing in nonaqueous media using alkene epoxidation and phenolic polymerization as relevant targets. This project will provide both the fundamental and applied investigations necessary to initiate the implementation of oxidative biocatalysts as commercially relevant alternatives to chemical processing in general, and to phenolic polymerizations and alkene epoxidation specifically. Thus, this work will address the Bioprocessing Solicitation Area to: (1) makes major improvements to phenolic polymerization and alkene epoxidation technologies; (2) is expected to be cost competitive with competing conventional processes; and (3) produces higher yields with less waste.

  1. Lactone radical cyclizations and cyclization cascades mediated by SmI2-H2O.

    Science.gov (United States)

    Parmar, Dixit; Matsubara, Hiroshi; Price, Kieran; Spain, Malcolm; Procter, David J

    2012-08-01

    Unsaturated lactones undergo reductive radical cyclizations upon treatment with SmI(2)-H(2)O to give decorated cycloheptanes in a single highly selective operation during which up to three contiguous stereocenters are generated. Furthermore, cascade processes involving lactones bearing two alkenes, an alkene and an alkyne, or an allene and an alkene allow "one-pot" access to biologically significant molecular scaffolds with the construction of up to four contiguous stereocenters. The cyclizations proceed by the trapping of radical anions formed by electron transfer reduction of the lactone carbonyl.

  2. Conjugate addition–enantioselective protonation reactions

    Directory of Open Access Journals (Sweden)

    James P. Phelan

    2016-06-01

    Full Text Available The addition of nucleophiles to electron-deficient alkenes represents one of the more general and commonly used strategies for the convergent assembly of more complex structures from simple precursors. In this review the addition of diverse protic and organometallic nucleophiles to electron-deficient alkenes followed by enantioselective protonation is summarized. Reactions are first categorized by the type of electron-deficient alkene and then are further classified according to whether catalysis is achieved with chiral Lewis acids, organocatalysts, or transition metals.

  3. A Facile and Efficient Synthesis of (15R)-Latanoprost from Chiral ...

    Indian Academy of Sciences (India)

    15R)-latanoprost using Corey lactone diol as chiral substrate under Swern oxidation, allylic reduction and Wittig reaction conditions has been developed. In this method, reduction of keto and alkene functional groups has been achieved in a ...

  4. Structural and Pharmacological Effects of Ring-Closing Metathesis in Peptides

    Directory of Open Access Journals (Sweden)

    Pål Rongved

    2010-09-01

    Full Text Available Applications of ring-closing alkene metathesis (RCM in acyclic α- and β-peptides and closely related systems are reviewed, with a special emphasis on the structural and pharmacological effects of cyclization by RCM.

  5. Magnetic Carbon Supported Palladium Nanoparticles: An Efficient and Sustainable Catalyst for Hydrogenation Reactions

    Science.gov (United States)

    Magnetic carbon supported Pd catalyst has been synthesized via in situ generation of nanoferrites and incorporation of carbon from renewable cellulose via calcination; the catalyst can be used for the hydrogenation of alkenes and reduction of aryl nitro compounds.

  6. Ritter Reaction in Liquid Sulfur Dioxide

    OpenAIRE

    Posevins, D; Kumpiņš, V; Turks, M

    2015-01-01

    Ritter reaction is associated with a one-pot process for amide bond formation, that involves nitrile and a group, capable of giving a relatively stable carbenium ion (originally - alcohol or alkene) in strongly ionizing acidic medium.

  7. Organic chemistry: Nickel steps towards selectivity

    Science.gov (United States)

    Gaunt, Matthew; Williamson, Patrick

    2017-05-01

    Hydrocarbons called alkenes are isolated from petroleum as mixtures of isomers, often making it hard to use them as reagents for synthesis. A reaction involving a migrating nickel atom offers a possible solution. See Letter p.84

  8. Source characterisation of Sedimentary organic matter in mangrove ecosystems of northern Kerala, India: Inferences from bulk characterisation and hydrocarbon biomarkers

    Digital Repository Service at National Institute of Oceanography (India)

    Resmi, P.; Manju, M.N.; Gireeshkumar, T.R.; RatheeshKumar, C.S.; Chandramohanakumar, N.

    Surface sediment samples from five mangrove ecosystems along the Kerala coast, north of Kochi were analysed for elemental ratios, stable isotopes of carbon and hydrocarbon biomarkers (n-alkanes, n-alkenes and hopanes) to assess the sources and early...

  9. A Facile and Efficient Synthesis of (15R)-Latanoprost from Chiral ...

    Indian Academy of Sciences (India)

    glaucoma agent, (15R)-latanoprost using Corey lactone diol as chiral substrate under Swern oxidation, allylic reduction and Wittig reaction condi- tions has been developed. In this method, reduction of keto and alkene functional groups has been ...

  10. Dermal uptake of petroleum substances

    NARCIS (Netherlands)

    Jakasa, Ivone; Kezic, Sanja; Boogaard, Peter J.

    2015-01-01

    Petroleum products are complex substances comprising varying amounts of linear and branched alkanes, alkenes, cycloalkanes, and aromatics which may penetrate the skin at different rates. For proper interpretation of toxic hazard data, understanding their percutaneous absorption is of paramount

  11. Protein modifications by electrophilic lipoxidation products: Adduct formation, chemical strategies and tandem mass spectrometry for their detection and identification

    OpenAIRE

    Vasil’ev, Yury V.; Tzeng, Shin-Chen; Huang, Lin; Maier, Claudia S.

    2014-01-01

    The post-translational modification of proteins by electrophilic oxylipids is emerging as an important mechanism that contributes to the complexity of proteomes. Enzymatic and nonenzymatic oxidation of biological lipids results in the formation of chemically diverse electrophilic carbonyl compounds, such as 2-alkenals and 4-hydroxy alkenals, epoxides and eicosanoids with reactive cyclopentenone structures. These lipoxidation products are capable of modifying proteins. Originally considered so...

  12. Metal–Organic Frameworks Stabilize Mono(phosphine)–Metal Complexes for Broad-Scope Catalytic Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Sawano, Takahiro; Lin, Zekai; Boures, Dean; An, Bing; Wang, Cheng; Lin, Wenbin (UC); (Xiamen)

    2016-08-10

    Mono(phosphine)–M (M–PR3; M = Rh and Ir) complexes selectively prepared by postsynthetic metalation of a porous triarylphosphine-based metal–organic framework (MOF) exhibited excellent activity in the hydrosilylation of ketones and alkenes, the hydrogenation of alkenes, and the C–H borylation of arenes. The recyclable and reusable MOF catalysts significantly outperformed their homogeneous counterparts, presumably via stabilizing M–PR3 intermediates by preventing deleterious disproportionation reactions/ligand exchanges in the catalytic cycles.

  13. The metathesis of alkynes

    Directory of Open Access Journals (Sweden)

    H. C. M. Vosloo

    1991-07-01

    Full Text Available The alkyne metathesis reaction is a direct result of the known and intensively studied alkene or olefin metathesis reaction. Unfortunately this reaction was never studied as intensively as the alkene metathesis reaction, mainly because of a lack of active catalytic systems. In the alkyn metathesis reaction the carbon-carbon triple bonds are broken and rearranged to give a redistribution of alkylidyne groups.

  14. E- and Z-Selective Transfer Semihydrogenation of Alkynes Catalyzed by Standard Ruthenium Olefin Metathesis Catalysts.

    Science.gov (United States)

    Kusy, Rafał; Grela, Karol

    2016-12-02

    Selective transfer semihydrogenation of alkynes to yield alkenes was achieved with commercial first and second generation Hoveyda-Grubbs catalysts and formic acid as a hydrogen donor. This catalytic system is distinguished by its selectivity and compatibility with many functional groups (halogens, cyano, nitro, sulfide, alkenes). The metathetic activity of the ruthenium catalysts may be utilized in tandem sequences of olefin metathesis plus alkyne reduction.

  15. Radical cations in condensed phases

    Energy Technology Data Exchange (ETDEWEB)

    Symons, M.C.R. (Leicester Univ. (UK). Dept. of Chemistry)

    The subject is covered in sections, entitled: introduction (scope of present Review); preparative procedures; alkane and cycloalkane cations; alkene and cyclic alkene cations; alkyl-halide cations; alcohol and ether cations; carbonyl cations (aldehyde, ketone and ester cations); sulphur-centred cations; selenium-centred cations; nitrogen-centred cations; phosphorus-centred cations; tin- and lead-centred cations; aromatic cations; five membered hetero-aromatic cations; vinyl cations; inorganic cations.

  16. Hydride Transfer versus Deprotonation Kinetics in the Isobutane–Propene Alkylation Reaction: A Computational Study

    OpenAIRE

    Liu, Chong; van Santen, Rutger A.; Poursaeidesfahani, Ali; Vlugt, Thijs J. H.; Pidko, Evgeny A.; Hensen, Emiel J. M.

    2017-01-01

    The alkylation of isobutane with light alkenes plays an essential role in modern petrochemical processes for the production of high-octane gasoline. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of isobutane–propene alkylation catalyzed by zeolitic solid acids. Particular emphasis was given to addressing the selectivity of the alkylate formation versus alkene formation, which requires a high rate o...

  17. Chromium oxide catalysts in the dehydrogenation of alkanes

    OpenAIRE

    Airaksinen, Sanna

    2005-01-01

    Light alkenes, such as propene and butenes, are important intermediates in the manufacture of fuel components and chemicals. The direct catalytic dehydrogenation of the corresponding alkanes is a selective way to produce these alkenes and is frequently carried out using chromia/alumina catalysts. The aim of this work was to obtain structure–activity information, which could be utilised in the optimisation of this catalytic system. The properties of chromia/alumina catalysts were investigated ...

  18. Potential of metal nanoparticles in organic reactions

    Science.gov (United States)

    Ranu, B. C.; Chattopadhyay, K.; Saha, A.; Adak, L.; Jana, R.; Bhadra, S.; Dey, R.; Saha, D.

    2008-03-01

    Palladium(0) nanoparticle has been used as efficient catalyst for (a) the stereoselective synthesis of (E)- and (Z)-2-alkene-4-ynoates and —nitriles by a simple reaction of vic-diiodo-(E)-alkenes with acrylic esters and nitriles and (b) for the allylation of active methylene compounds by allylacetate and its derivatives. Copper(0) nanoparticle catalyzes aryl-sulfur bond formation very efficiently. All these reactions are ligand-free.

  19. Catalytic Z-selective olefin cross-metathesis for natural product synthesis.

    Science.gov (United States)

    Meek, Simon J; O'Brien, Robert V; Llaveria, Josep; Schrock, Richard R; Hoveyda, Amir H

    2011-03-24

    Alkenes are found in many biologically active molecules, and there are a large number of chemical transformations in which alkenes act as the reactants or products (or both) of the reaction. Many alkenes exist as either the E or the higher-energy Z stereoisomer. Catalytic procedures for the stereoselective formation of alkenes are valuable, yet methods enabling the synthesis of 1,2-disubstituted Z alkenes are scarce. Here we report catalytic Z-selective cross-metathesis reactions of terminal enol ethers, which have not been reported previously, and of allylic amides, used until now only in E-selective processes. The corresponding disubstituted alkenes are formed in up to >98% Z selectivity and 97% yield. These transformations, promoted by catalysts that contain the highly abundant and inexpensive metal molybdenum, are amenable to gram-scale operations. Use of reduced pressure is introduced as a simple and effective strategy for achieving high stereoselectivity. The utility of this method is demonstrated by its use in syntheses of an anti-oxidant plasmalogen phospholipid, found in electrically active tissues and implicated in Alzheimer's disease, and the potent immunostimulant KRN7000.

  20. Secondary organic aerosol formation from cyclohexene ozonolysis: effect of OH scavenger and the role of radical chemistry.

    Science.gov (United States)

    Keywood, M D; Kroll, J H; Varutbangkul, V; Bahreini, R; Flagan, R C; Seinfeld, J H

    2004-06-15

    To isolate secondary organic aerosol (SOA) formation in ozone-alkene systems from the additional influence of hydroxyl (OH) radicals formed in the gas-phase ozone-alkene reaction, OH scavengers are employed. The detailed chemistry associated with three different scavengers (cyclohexane, 2-butanol, and CO) is studied in relation to the effects of the scavengers on observed SOA yields in the ozone-cyclohexene system. Our results confirm those of Docherty and Ziemann that the OH scavenger plays a role in SOA formation in alkene ozonolysis. The extent and direction of this influence are shown to be dependent on the specific alkene. The main influence of the scavenger arises from its independent production of HO2 radicals, with CO producing the most HO2, 2-butanol an intermediate amount, and cyclohexane the least. This work provides evidence for the central role of acylperoxy radicals in SOA formation from the ozonolysis of alkenes and generally underscores the importance of gas-phase radical chemistry beyond the initial ozone-alkene reaction.

  1. Ethene, propene, butene and isoprene emissions from a ponderosa pine forest measured by relaxed eddy accumulation

    Science.gov (United States)

    Rhew, Robert C.; Deventer, Malte Julian; Turnipseed, Andrew A.; Warneke, Carsten; Ortega, John; Shen, Steve; Martinez, Luis; Koss, Abigail; Lerner, Brian M.; Gilman, Jessica B.; Smith, James N.; Guenther, Alex B.; de Gouw, Joost A.

    2017-11-01

    Alkenes are reactive hydrocarbons that influence local and regional atmospheric chemistry by playing important roles in the photochemical production of tropospheric ozone and in the formation of secondary organic aerosols. The simplest alkene, ethene (ethylene), is a major plant hormone and ripening agent for agricultural commodities. The group of light alkenes (C2-C4) originates from both biogenic and anthropogenic sources, but their biogenic sources are poorly characterized, with limited field-based flux observations. Here we report net ecosystem fluxes of light alkenes and isoprene from a semiarid ponderosa pine forest in the Rocky Mountains of Colorado, USA using the relaxed eddy accumulation (REA) technique during the summer of 2014. Ethene, propene, butene and isoprene emissions have strong diurnal cycles, with median daytime fluxes of 123, 95, 39 and 17 µg m-2 h-1, respectively. The fluxes were correlated with each other, followed general ecosystem trends of CO2 and water vapor, and showed similar sunlight and temperature response curves as other biogenic VOCs. The May through October flux, based on measurements and modeling, averaged 62, 52, 24 and 18 µg m-2 h-1 for ethene, propene, butene and isoprene, respectively. The light alkenes contribute significantly to the overall biogenic source of reactive hydrocarbons: roughly 18 % of the dominant biogenic VOC, 2-methyl-3-buten-2-ol. The measured ecosystem scale fluxes are 40-80 % larger than estimates used for global emissions models for this type of ecosystem.

  2. Inhibition and Promotion of Pyrolysis by Hydrogen Sulfide (H2S) and Sulfanyl Radical (SH)

    DEFF Research Database (Denmark)

    Zeng, Zhe; Altarawneh, Mohammednoor; Oluwoye, Ibukun

    2016-01-01

    the weakest C–H sites in alkenes and alkynes, except for ethylene, appears noticeably exothermic. Furthermore, abstraction of H from propene, 1-butene, and iso-butene displays pronounced spontaneity (i.e., ΔrG° hydrogen bond. However......, an alkyl radical readily abstracts H atom from H2S, with H2S acting as a potent scavenger for alkyl radicals in combustion processes. That is, these reactions proceed in the opposite direction than those involving SH and alkene or alkyne species, exhibiting shallow barriers and strong spontaneity. Our...... findings demonstrate that the documented inhibition effect of hydrogen sulfide (H2S) on pyrolysis of alkanes does not apply to alkenes and alkynes. During interaction with hydrocarbons, the inhibitive effect of H2S and promoting interaction of SH radical depend on the reversibility of the H abstraction...

  3. Catalytic and Atom-Economic Csp3 -Csp3 Bond Formation: Alkyl Tantalum Ureates for Hydroaminoalkylation.

    Science.gov (United States)

    DiPucchio, Rebecca C; Roşca, Sorin-Claudiu; Schafer, Laurel L

    2018-03-19

    Atom-economic and regioselective Csp3 -Csp3 bond formation has been achieved by rapid C-H alkylation of unprotected secondary arylamines with unactivated alkenes. The combination of Ta(CH 2 SiMe 3 ) 3 Cl 2 , and a ureate N,O-chelating-ligand salt gives catalytic systems prepared in situ that can realize high yields of β-alkylated aniline derivatives from either terminal or internal alkene substrates. These new catalyst systems realize C-H alkylation in as little as one hour and for the first time a 1:1 stoichiometry of alkene and amine substrates results in high yielding syntheses of isolated amine products by simple filtration and concentration. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Methods of making organic compounds by metathesis

    Science.gov (United States)

    Abraham, Timothy W.; Kaido, Hiroki; Lee, Choon Woo; Pederson, Richard L.; Schrodi, Yann; Tupy, Michael John

    2015-09-01

    Described are methods of making organic compounds by metathesis chemistry. The methods of the invention are particularly useful for making industrially-important organic compounds beginning with starting compositions derived from renewable feedstocks, such as natural oils. The methods make use of a cross-metathesis step with an olefin compound to produce functionalized alkene intermediates having a pre-determined double bond position. Once isolated, the functionalized alkene intermediate can be self-metathesized or cross-metathesized (e.g., with a second functionalized alkene) to produce the desired organic compound or a precursor thereto. The method may be used to make bifunctional organic compounds, such as diacids, diesters, dicarboxylate salts, acid/esters, acid/amines, acid/alcohols, acid/aldehydes, acid/ketones, acid/halides, acid/nitriles, ester/amines, ester/alcohols, ester/aldehydes, ester/ketones, ester/halides, ester/nitriles, and the like.

  5. Catalytic enantioselective synthesis of chiral organic compounds of ultra-high purity of >99% ee.

    Science.gov (United States)

    Negishi, Ei-ichi; Xu, Shiqing

    2015-01-01

    Shortly after the discovery of Zr-catalyzed carboalumination of alkynes in 1978, we sought expansion of the scope of this reaction so as to develop its alkene version for catalytic asymmetric C-C bond formation, namely the ZACA (Zr-catalyzed asymmetric carboalumination of alkenes). However, this seemingly easy task proved to be quite challenging. The ZACA reaction was finally discovered in 1995 by suppressing three competitive side reactions, i.e., (i) cyclic carbometalation, (ii) β-H transfer hydrometalation, and (iii) alkene polymerization. The ZACA reaction has been used to significantly modernize and improve syntheses of various natural products including deoxypolypropionates and isoprenoids. This review focuses on our recent progress on the development of ZACA-lipase-catalyzed acetylation-transition metal-catalyzed cross-coupling processes for highly efficient and enantioselective syntheses of a wide range of chiral organic compounds with ultra-high enantiomeric purities.

  6. Mechanistic studies of the reactions of 2-methylpropene with deuterium over supported metal catalysts

    International Nuclear Information System (INIS)

    Brown, R.; Kemball, C.; Sadler, I.H.

    1989-01-01

    Deuterium NMR spectroscopy, gas chromatography and mass spectrometry have been used to examine the products from the reaction of 2-methylpropene with deuterium over supported metal catalysts. The detailed information, so obtained, about the number, location and grouping of deuterium atoms in both the exchanged alkenes and the 2-methylpropanes formed by addition provided evidence about possible mechanisms. With palladium, exchange was faster than addition and the deuterium atoms were randomly distributed in the alkene, probably through a π-allyl dissociative mechanism. With platinum and rhodium, exchange occurred preferentially in the methylene groups of the alkene and the results indicated a dissociative mechanism involving adsorbed vinyl intermediates together with some intramolecular double-bond movement through a π-allyl type of species. Relatively little exchange occurred with iridium. (author)

  7. Olefination reactions of phosphorus-stabilized carbon nucleophiles.

    Science.gov (United States)

    Gu, Yonghong; Tian, Shi-Kai

    2012-01-01

    A range of phosphorus-stabilized carbon nucleophiles have been employed for alkene synthesis with high chemo-, regio-, and stereoselectivity. The Wittig, Horner-Wadsworth-Emmons, Horner-Wittig, and Evans-Akiba reactions utilize phosphonium-, phosphonate-, phosphine oxide-, and pentacoordinated phosphorane-stabilized carbanions as nucleophiles, respectively, to undergo olefination with aldehydes or ketones, and each of these transformations has its own advantages and limitations. Modifying the structures of these nucleophiles along with optimizing reaction conditions results in the formation of a wide variety of polysubstituted alkenes in a highly stereoselective manner. The olefination of imines with phosphonium ylides has recently emerged as a useful approach to tune the stereoselectivity for alkene synthesis. This review focuses on recent advances in the stereoselective olefination of phosphorus-stabilized carbon nucleophiles.

  8. Epoxidation catalyst and process

    Science.gov (United States)

    Linic, Suljo; Christopher, Phillip

    2010-10-26

    Disclosed herein is a catalytic method of converting alkenes to epoxides. This method generally includes reacting alkenes with oxygen in the presence of a specific silver catalyst under conditions suitable to produce a yield of the epoxides. The specific silver catalyst is a silver nanocrystal having a plurality of surface planes, a substantial portion of which is defined by Miller indices of (100). The reaction is performed by charging a suitable reactor with this silver catalyst and then feeding the reactants to the reactor under conditions to carry out the reaction. The reaction may be performed in batch, or as a continuous process that employs a recycle of any unreacted alkenes. The specific silver catalyst has unexpectedly high selectivity for epoxide products. Consequently, this general method (and its various embodiments) will result in extraordinarily high epoxide yields heretofore unattainable.

  9. Volatile Organic Compounds Selection for Incorporation in Photochemical Mechanisms and the Development of Secondary Pollution Reduction Strategies

    Energy Technology Data Exchange (ETDEWEB)

    Karathanasis, Stavros [Directorate of Environment and Land Planning, Region of Central Macedonia (Greece)], E-mail: stkarath@rcm.gr; Ziomas, Ioannis [National Technical University of Athens, Zografou Campus, Department of Chemical Engineering (Greece)

    2009-04-15

    In the present work a method for the evaluation of the importance of the VOCs species is presented, aiming to provide criteria for the incorporation of these species into atmospheric photochemical mechanisms and for the successful application of secondary pollution reduction strategies. According to the method presented here, the species can be divided into more important and less important ones, taking into account their mixing ratios and emission values in combination with their reactivity. For this classification three quantitative and one qualitative criteria were introduced. Overall, it is concluded that alkenes with more than a few carbon atoms in their chain appear to be more important in urban and suburban areas, while in background conditions the alkanes, having the smaller chain (ethane, propane), become more important. In the case of alkenes there is no clear species classification, except for the biogenically emitted compounds, isoprene and limonene. In general, more important alkenes appear to be those with the smaller chain (ethene, propene, butene). Most abundant aromatics are benzene, toluene, and xylene. In background conditions higher aromatics are also important, especially 1,2,3-, 1,3,5-, and 1,2,4-trimethylbenzene. The most important carbonylic compounds are formaldehyde, acetaldehyde, and acetone. Finally, taking into account the results mentioned above, a new photochemical mechanism was developed. The species and species groups used in the proposed mechanism are: ethane, higher alkanes, ethene, propene, 2- butene, 1-alkenes, 2-alkenes, higher alkenes, benzene, toluene, m-, o-, p-xylene, 1,3,5-, 1,2,3-, 1,2,4-trimethylbenzene, higher aromatics, formaldehyde, acetaldehyde, higher aldehydes, isoprene, limonene, and other biogenic VOCs.

  10. Control of ozonolysis kinetics and aerosol yield by nuances in the molecular structure of volatile organic compounds

    Science.gov (United States)

    Harvey, Rebecca M.; Petrucci, Giuseppe A.

    2015-12-01

    Secondary organic aerosol (SOA) plays integral roles in climate and human health, yet there remains a limited understanding of the mechanisms that lead to its formation and ultimate fate, as evidenced by a disparity between modeled atmospheric SOA loadings and field measurements. This disparity highlights the need for a more accurate representation of the molecular-level interactions between SOA sources and oxidative pathways. Due to the paucity of detailed chemical data for most SOA precursors of atmospheric relevance, models generally predict SOA loadings using structure activity relationships generalized to classes of SOA precursors. However, the kinetics and SOA forming potential of molecules are nuanced by seemingly minor structural differences in parent molecules that may be neglected in models. Laboratory chamber studies were used to measure SOA yields and rate constants for the ozonolysis of several linear, cyclic and oxygenated C5-C7 alkenes whose molecular structure vary in the site of unsaturation and/or the presence/position of functional groups and that represent atmospherically relevant classes of molecules. For the alkenes studied in this work, we found greater SOA yields for cyclic compounds compared to their linear analogs. For 1-alkenes, SOA yield increased with carbon number but was also dependent on the position of the double bond (internal vs terminal). Both the identity and position of oxygenated functional groups influenced SOA yield and kinetics through steric and electronic effects. Additionally, terminal alkenes generally resulted in a greater SOA yield than analogous internal alkenes, indicating that the position of the double bond in alkenes plays an important role in its atmospheric fate. Herein, we demonstrate the nuanced behavior of these ozonolysis reactions and discuss relationships between parent compound molecular structure and SOA yield and kinetics.

  11. Highly Chemo- and Stereoselective Transfer Semihydrogenation of Alkynes Catalyzed by a Stable, Well-defined Manganese(II) Complex

    KAUST Repository

    Brzozowska, Aleksandra

    2018-03-30

    The first example of manganese catalyzed semihydrogenation of internal alkynes to (Z)-alkenes using ammonia borane as a hydrogen donor is reported. The reaction is catalyzed by a pincer complex of the earth abundant manganese(II) salt in the absence of any additives, base or super hydride. The ammonia borane smoothly reduces the manganese pre-catalyst [Mn(II)-PNP][Cl]2 to the catalytically active species [Mn(I)-PNP]-hydride in the triplet spin state. This manganese hydride is highly stabilized by complexation with the alkyne substrate. Computational DFT analysis studies of the reaction mechanism rationalizes the origin of stereoselectivity towards formation of (Z)-alkenes.

  12. Mild Two-Step Method to Construct DNA-Conjugated Silicon Nanoparticles: Scaffolds for the Detection of MicroRNA-21

    OpenAIRE

    Su, Xiaoye; Kuang, Li; Battle, Cooper; Shaner, Ted; Mitchell, Brian S.; Fink, Mark J.; Jayawickramarajah, Janarthanan

    2014-01-01

    We describe a novel two-step method, starting from bulk silicon wafers, to construct DNA conjugated silicon nanoparticles (SiNPs). This method first utilizes reactive high-energy ball milling (RHEBM) to obtain alkene grafted SiNPs. The alkene moieties are subsequently reacted with commercially available thiol-functionalized DNA via thiol–ene click chemistry to produce SiNP DNA conjugates wherein the DNA is attached through a covalent thioether bond. Further, to show the utility of this synthe...

  13. Wittig Reaction: Domino Olefination and Stereoselectivity DFT Study. Synthesis of the Miharamycins' Bicyclic Sugar Moiety.

    Science.gov (United States)

    Cachatra, Vasco; Almeida, Andreia; Sardinha, João; Lucas, Susana D; Gomes, Ana; Vaz, Pedro D; Florêncio, M Helena; Nunes, Rafael; Vila-Viçosa, Diogo; Calhorda, Maria José; Rauter, Amélia P

    2015-11-20

    2-O-Acyl protected-d-ribo-3-uloses reacted with [(ethoxycarbonyl)methylene]triphenylphosphorane in acetonitrile to afford regio- and stereoselectively 2-(Z)-alkenes in 10-60 min under microwave irradiation. This domino reaction is proposed to proceed via tautomerization of 3-ulose to enol, acyl migration, tautomerization to the 3-O-acyl-2-ulose, and Wittig reaction. Alternatively, in chloroform, regioselective 3-olefination of 2-O-pivaloyl-3-uloses gave (E)-alkenes, key precursors for the miharamycins' bicyclic sugar moiety.

  14. Methylenation of perfluoroalkyl ketones using a Peterson olefination approach.

    Science.gov (United States)

    Hamlin, Trevor A; Kelly, Christopher B; Cywar, Robin M; Leadbeater, Nicholas E

    2014-02-07

    An operationally simple, inexpensive, and rapid route for the olefination of a wide array of trifluoromethyl ketones to yield 3,3,3-trifluoromethylpropenes is reported. Using a Peterson olefination approach, the reaction gives good to excellent yields of the alkene products and can be performed without purification of the β-hydroxysilyl intermediate. The reaction can be extended to other perfluoroalkyl substituents and is easily scaled up. The alkenes prepared can be readily transformed into a variety of other perfluoroalkyl-containing compounds.

  15. Synthesis of Silyloxy Dienes by Silylene Tranfer to Divinyl Ketones: Application to the Asymmetric Sythesis of Substituted Cyclohexanes

    Science.gov (United States)

    Ventocilla, Christian C.; Woerpel, K. A.

    2012-01-01

    Silver-catalyzed silylene transfer to divinyl ketones provided 2-silyloxy-1,3-dienes with control of stereochemistry and regioselectivity. The products participated in Diels–Alder reactions with electron-deficient alkenes and imines to form six-membered ring products diastereoselectively. Cycloaddition reactions with alkenes bearing chiral auxiliaries provided access to chiral, non-racemic cyclohexenes. The methodology therefore represents a synthesis of diastereomerically and enantiomerically pure products in a single flask. The highly substituted cyclohexene products could be functionalized stereoselectively to provide cyclohexanols after oxidation of the carbon–silicon bond. PMID:22372733

  16. Synthesis of silyloxy dienes by silylene transfer to divinyl ketones: application to the asymmetric synthesis of substituted cyclohexanes.

    Science.gov (United States)

    Ventocilla, Christian C; Woerpel, K A

    2012-04-06

    Silver-catalyzed silylene transfer to divinyl ketones provided 2-silyloxy-1,3-dienes with control of stereochemistry and regioselectivity. The products participated in Diels-Alder reactions with electron-deficient alkenes and imines to form six-membered-ring products diastereoselectively. Cycloaddition reactions with alkenes bearing chiral auxiliaries provided access to chiral, nonracemic cyclohexenes. The methodology, therefore, represents a synthesis of diastereomerically and enantiomerically pure products in a single flask. The highly substituted cyclohexene products could be functionalized stereoselectively to provide cyclohexanols after oxidation of the carbon-silicon bond.

  17. Teaching Green Chemistry with Epoxidized Soybean Oil

    Science.gov (United States)

    Barcena, Homar; Tuachi, Abraham; Zhang, Yuanzhuo

    2017-01-01

    The synthesis of epoxidized soybean oil (ESO) provides students a vantage point on the application of green chemistry principles in a series of experiments. Qualitative tests review the reactions of alkenes, whereas spectroscopic analyses provide insight in monitoring functional group transformations.

  18. Ni(0-CMC-Na Nickel Colloids in Sodium Carboxymethyl-Cellulose: Catalytic Evaluation in Hydrogenation Reactions

    Directory of Open Access Journals (Sweden)

    Abdallah Karim

    2011-01-01

    Full Text Available A recyclable catalyst, Ni(0-CMC-Na, composed of nickel colloids dispersed in a water soluble bioorganic polymer, sodium carboxymethylcellulose (CMC-Na, was synthesized by a simple procedure from readily available reagents. The catalyst thus obtained is stable and highly active in alkene hydrogenations.

  19. Exchange of alkanes with deuterium over γ-alumina

    International Nuclear Information System (INIS)

    John, C.S.; Kemball, C.; Pearce, E.A.; Pearman, A.J.

    1979-01-01

    Exchange reactions of hydrocarbons with deuterium over γ-alumina have been extensively studied but less attention has been directed to the effect of catalyst activation temperature. It has been shown that activity for propane/D 2 exchange passes through a sharp maximum at approximately 823 K and similar behaviour has been shown for the various exchange processes of propene. In this work, the first objective was to examine the effect of varying catalyst activation temperature, Tsub(a), on the subsequent activity of γ-alumina for the exchange of cyclopentane with D 2 ; the effect of chloriding the alumina was also studied. The second objective was to study the influence on the activity for cyclopentane/D 2 exchange of pretreating the catalyst with alkene at various temperatures to determine whether poisoning occurred. The literature indicates that for alkene exchange with deuterium on alumina reaction occurs preferentially for the vinyl hydrogen atoms as opposed to the hydrogen atoms attached to saturated carbon atoms. On this evidence one might expect the presence of alkene to interfere with the exchange of alkanes and indeed there is work which reports that alkene poisons both CH 4 /D 2 and H 2 /D 2 exchange. Finally, the effect of chain-length on the relative rates of methylene and methyl exchange in straight-chain hydrocarbons was examined to follow up previous work on propane and butane. The results are presented and discussed. (author)

  20. SHORT COMMUNICATION A CONVENIENT METHOD FOR ...

    African Journals Online (AJOL)

    Preferred Customer

    allyloxy chalcones to flavones encouraged us to use this reagent system for the cyclization of α- allyl esters. 2'-Allyloxy chalcones with iodine (20%) in dimethylsulphoxide result in attack of the allyloxy oxygen towards reactive alkene group. This results in the deallylation of 2'-allyloxy chalcones followed by cyclization to give ...

  1. Chemistry of Unique Chiral Olefins. 4. Theoretical Studies of the Racemization Mechanism of trans- and cis-1,1',2,2',3,3',4,4'-Octahydro-4,4'-biphenanthrylidenes

    NARCIS (Netherlands)

    Zijlstra, Robert W.J.; Jager, Wolter F.; Lange, Ben de; Duijnen, Piet Th. van; Goto, Hitoshi; Saito, Akira; Koumura, Nagatoshi; Harada, Nobuyuki; Feringa, Bernard

    1999-01-01

    The minimum energy conformations and racemization barriers for the chiral sterically overcrowded helical alkenes, trans- and cis-1,1',2,2',3,3',4,4'-octahydro-4,4'-biphenanthrylidenes (1 and 2), are reported. The trans-1 and cis-2 isomers can each adapt three different conformations, (P,P) and (M,M)

  2. Physicochemical parameters related to organoleptic properties of flavour components

    NARCIS (Netherlands)

    Boelens, M.H.; Gemert, L.J. van

    1986-01-01

    Straight chain, saturated and unsarurated, aldehydes are important constituents of citrus fruit, dairy, vegetable, meat and other flavours. For instance, alkanals and 2-alkenals (C6 to C14) have been detected and quantified in Bitter Orange Oil. The organoleptic qualities and threshold values of

  3. In silico screening of metal-organic frameworks in separation applications

    NARCIS (Netherlands)

    Krishna, R.; van Baten, J.M.

    2011-01-01

    Porous materials such as metal-organic frameworks (MOFs) and zeolitic imidazolate frameworks (ZIFs) offer considerable potential for separating a variety of mixtures such as those relevant for CO2 capture (CO2/H2, CO2/CH4, CO2/N2), CH4/H2, alkanes/alkenes, and hydrocarbon isomers. There are

  4. Methods for the synthesis of donor-acceptor cyclopropanes

    Science.gov (United States)

    Tomilov, Yu V.; Menchikov, L. G.; Novikov, R. A.; Ivanova, O. A.; Trushkov, I. V.

    2018-03-01

    The interest in cyclopropane derivatives is caused by the facts that, first, the three-carbon ring is present in quite a few natural and biologically active compounds and, second, compounds with this ring are convenient building blocks for the synthesis of diverse molecules (acyclic, alicyclic and heterocyclic). The carbon–carbon bonds in cyclopropane are kinetically rather inert; hence, they need to be activated to be involved in reactions. An efficient way of activation is to introduce vicinal electron-donating and electron-withdrawing substituents into the ring; these substrates are usually referred to as donor-acceptor cyclopropanes. This review gives a systematic account of the key methods for the synthesis of donor-acceptor cyclopropanes. The most important among them are reactions of nucleophilic alkenes with diazo compounds and iodonium ylides and approaches based on reactions of electrophilic alkenes with sulfur ylides (the Corey–Chaykovsky reaction). Among other methods used for this purpose, noteworthy are cycloalkylation of CH-acids, addition of α-halocarbonyl compounds to alkenes, cyclization via 1,3-elimination, reactions of alkenes with halocarbenes followed by reduction, the Simmons–Smith reaction and some other. The scope of applicability and prospects of various methods for the synthesis of donor-acceptor cyclopropanes are discussed. The bibliography includes 530 references.

  5. Covalently attached organic monolayers on SiC and SixN4 surfaces: Formation using UV light at room temperature

    NARCIS (Netherlands)

    Rosso, M.; Giesbers, M.; Arafat, A.; Schroën, C.G.P.H.; Zuilhof, H.

    2009-01-01

    We describe the formation of alkyl monolayers on silicon carbide (SiC) and silicon-rich silicon nitride (SixN4) surfaces, using UV irradiation in the presence of alkenes. Both the surface preparation and the monolayer attachment were carried out under ambient conditions. The stable coatings obtained

  6. Covalently Attached Monolayers on Crystalline Hydrogen-Terminated Silicon: Extremely Mild Attachment by Visible Light

    NARCIS (Netherlands)

    Sun, Q.Y.; Smet, de L.C.P.M.; Lagen, van B.; Giesbers, M.; Thüne, P.C.; Engelenburg, van J.; Wolf, de F.A.; Zuilhof, H.; Sudhölter, E.J.R.

    2005-01-01

    A very mild method was developed for the attachment of high-quality organic monolayers on crystalline silicon surfaces. By using visible light sources, from 447 to 658 nm, a variety of 1-alkenes and 1-alkynes were attached to hydrogen-terminated Si(100) and Si(111) surfaces at room temperature. The

  7. Design, synthesis, and application of a hydrazide-functionalized isotope-coded affinity tag for the quantification of oxylipid-protein conjugates.

    Science.gov (United States)

    Han, Bingnan; Stevens, Jan F; Maier, Claudia S

    2007-05-01

    An isotopically coded affinity probe was developed and evaluated for the characterization and quantification of proteins adducted by 2-alkenals derived from lipid peroxidation (LPO) processes. Lipid-derived 2-alkenals, such as acrolein and 4-hydroxy-2-nonenal (HNE), have the ability to react with cysteine, histidine, and lysine residues in proteins, thus causing protein damage and loss of protein function. Such modifications of proteins are difficult to characterize in biological samples by mass spectrometry due to the complexity of protein extracts and the low abundance of adducted proteins. The novel aldehyde-reactive, hydrazide-functionalized, isotope-coded affinity tag (HICAT) described in this study was found effective for the selective isolation, detection, and quantification of Michael-type adducts of 2-alkenals with proteins using a combination of affinity isolation, nanoLC, and matrix-assisted laser desorption ionization tandem mass spectrometry (MALDI-MS/MS). The chemical and mass spectrometric properties of the new probe are demonstrated on a model protein treated with HNE. The efficacy of HICAT for the analysis of complex samples was tested using preparations of mitochondrial proteins that were modified in vitro with HNE. The potential of the HICAT strategy for the identification, characterization, and quantification of in vivo oxylipid-protein conjugates is demonstrated on cardiac mitochondrial protein preparations, in which, for example, the ADP/ATP translocase 1 was found adducted to the 2-alkenals, acrolein and 4-hydroxy-2-hexenal, at Cys-256.

  8. Reactions of Nitroso Hetero Diels-Alder Cycloadducts with Azides: Stereoselective Formation of Triazolines and Aziridines

    Science.gov (United States)

    Bodnar, Brian S.

    2011-01-01

    The addition of azides to acylnitroso hetero Diels-Alder cycloadducts derived from cyclopentadiene affords exo triazolines in excellent yield. The reaction is greatly affected by reducing the level of alkene strain, while sterically demanding azides do not hinder the reaction. Conversion of the triazolines to aziridines is also described. PMID:17429998

  9. SYNTHESIS, CHARACTERIZATION AND ANTIBACTERIAL ...

    African Journals Online (AJOL)

    B. S. Chandravanshi

    compounds. Tetradentate Schiff bases with a N2O2 donor atom set are well known to coordinate with various metal ions, and this has attracted many authors [17, 18]. Some Co(II), Cu(II) and Fe(II) Schiff base chelate complexes show catalytic activity in oxygenation of alkene and increase the rate of hydrolysis more than ...

  10. SYNTHESIS OF 7-DEHYDROCHOLESTEROL THROUGH ...

    African Journals Online (AJOL)

    Preferred Customer

    allylic moiety like acetate, halide, hydroxide, etc. are alkylated by molybdenum catalyst in the presence of a nucleophile [16]. Allyl-molybdenum complex formation of alkene and subsequent .... temperature molybdenum has the ability to eliminate any acetoxyl group attached to carbon [19] in the form of acetic acid molecule.

  11. Bromination of olefins with HBr and DMSO.

    Science.gov (United States)

    Karki, Megha; Magolan, Jakob

    2015-04-03

    A simple and inexpensive methodology is reported for the conversion of alkenes to 1,2-dibromo alkanes via oxidative bromination using HBr paired with dimethyl sulfoxide, which serves as the oxidant as well as cosolvent. The substrate scope includes 21 olefins brominated in good to excellent yields. Three of six styrene derivatives yielded bromohydrins under the reaction conditions.

  12. Experimental and theoretical study of Hoveyda-Grubbs catalysts modified by perfluorohexyl ponytail in the alkoxybenzylidene ligand

    Czech Academy of Sciences Publication Activity Database

    Kvíčala, J.; Schindler, M.; Kelbichová, V.; Babuněk, M.; Rybáčková, M.; Kvíčalová, M.; Cvačka, Josef; Březinová, Anna

    2013-01-01

    Roč. 153, September (2013), s. 12-25 ISSN 0022-1139 Grant - others:GA ČR(CZ) GAP207/10/1533 Institutional support: RVO:61388963 Keywords : Hoveyda-Grubbs catalyst * NHC ligand * ruthenium complex * fluorous * alkene metathesis * DFT Subject RIV: CC - Organic Chemistry Impact factor: 1.952, year: 2013

  13. Z-Selective Copper-Catalyzed Asymmetric Allylic Alkylation with Grignard Reagents

    NARCIS (Netherlands)

    Giannerini, Massimo; Fananas-Mastral, Martin; Feringa, Ben L.; Fañanás-Mastral, Martín

    2012-01-01

    Allylic gem-dichlorides undergo regio- and enanantioselective (er up to 99:1) copper-catalyzed allylic alkylation with Grignard reagents affording chiral Z-vinyl chlorides. This highly versatile class of synthons can be subjected to Suzuki cross coupling affording optically active Z-alkenes and

  14. Diversity-Oriented Enantioselective Synthesis of Highly Functionalized Cyclic and Bicyclic Alcohols

    NARCIS (Netherlands)

    Mao, Bin; Fananas Mastral, Martin; Lutz, Martin; Feringa, Ben L.

    The copper-catalyzed hetero-allylic asymmetric alkylation (h-AAA) of functionalized Grignard reagents that contain alkene or alkyne moieties has been achieved with excellent regio-and enantioselectivity. The corresponding alkylation products were further transformed into a variety of highly

  15. Identification and Characterisation of Major Hydrocarbons in ...

    African Journals Online (AJOL)

    Identification and Characterisation of Major Hydrocarbons in Thermally Degraded Low Density Polyethylene Films. ... There were alkanes, alkenes, halogenated alkanes, and very few aromatics in the liquid product and, the hydrocarbons were observed to range between C10 - C27. The FTIR and GC-MS results show the ...

  16. Origin and palaeoenvironmental significance of C

    NARCIS (Netherlands)

    van Bree, L.G.J.; Rijpstra, W.I.C.; Cocquyt, C.; Al-Dhabi, N.-A.; Verschuren, D.; Sinninghe Damsté, J.S.; de Leeuw, J.W.

    2014-01-01

    We studied the distribution of long-chain alkenes (n-C23 to n-C31) in well-dated sediments from Lake Challa, a deep crater lake near Mt. Kilimanjaro in equatorial East Africa, to reveal signatures of palaeo-environmental and palaeo-climatic changes affecting the production of these compounds during

  17. Light-driven rotary molecular motors : an ultrafast optical study

    NARCIS (Netherlands)

    Augulis, Ramunas; Klok, Martin; Loosdrecht, Paul H.M. van; Feringa, Bernard

    2009-01-01

    Molecular rotary motors, though common in nature, were first synthesized rather recently. One of the most promising categories of light-driven rotary molecular motors which allow for optical control is based on helical overcrowded alkenes. In this category of motors, the rotation of the motor’s

  18. Dynamic control of function by light-driven molecular motors

    NARCIS (Netherlands)

    van Leeuwen, Thomas; Lubbe, Anouk S.; Stacko, Peter; Wezenberg, Sander J.; Feringa, Ben L.

    2017-01-01

    The field of dynamic functional molecular systems has progressed enormously over the past few decades. By coupling the mechanical properties of molecular switches and motors to chemical and biological processes, exceptional control of function has been attained. Overcrowded alkene-based light-driven

  19. Author Details

    African Journals Online (AJOL)

    Preparation of Tetramethylguanidine-Functionalized Mesoporous Silica as a Catalyst for the Epoxidation of Electron Deficient Alkenes Abstract PDF · Vol 38, No 1 (2012) - Articles Synthesis of organoamine-silica hybrids using cashew nut shell liquid components as templates for the catalysis of a model Henry reaction

  20. Molybdenum-catalyzed deoxydehydration of vicinal diols

    DEFF Research Database (Denmark)

    Dethlefsen, Johannes Rytter; Lupp, Daniel; Oh, Byung Chang

    2014-01-01

    The commercially available (NH4)6Mo7O24 and other molybdenum compounds are shown to be viable substitutes for the typically employed rhenium compounds in the catalytic deoxydehydration of aliphatic diols into the corresponding alkenes. The transformation, which represents a model system for the v...

  1. Protein-Repellent Silicon Nitride Surfaces: UV-Induced Formation of Oligoethylene Oxide Monolayers

    NARCIS (Netherlands)

    Rosso, M.; Nguyen, A.T.; Jong, de E.; Baggerman, J.; Paulusse, J.M.J.; Giesbers, M.; Fokkink, R.G.; Norde, W.; Schroën, C.G.P.H.; Rijn, van C.J.M.; Zuilhof, H.

    2011-01-01

    The grafting of polymers and oligomers of ethylene oxide onto surfaces is widely used to prevent nonspecific adsorption of biological material on sensors and membrane surfaces. In this report, we show for the first time the robust covalent attachment of short oligoethylene oxide-terminated alkenes

  2. Bio-olefins via tandem isomerization-decarboxylation catalysis upon fatty acids

    Science.gov (United States)

    A facile Ru-catalyzed route to bio-alkenes from alkenoic fatty acids will be discussed. A readily accessible pre-catalyst [Ru(CO)2RCO2]n. apparently functions in a tandem mode by dynamically isomerizing the positions of double bonds in an aliphatic chain and, subsequently, decarboxylating specific i...

  3. Synthesis and Antimicrobial Activity of the Essential Oil Compounds ...

    African Journals Online (AJOL)

    In particular, it was found that the use of triethylamine as a co-solvent was necessary to avoid acid-mediated isomerization of the alkenes, which resulted in an inseparable mixture of products. The antimicrobial activity of the four hexenyl and hexyl nonanoate compounds was undertaken using microdilution minimum ...

  4. cis- and trans-Stilbenes: Chromatographic Separation and Photochemical Isomerization.

    Science.gov (United States)

    Levine, Samuel G.; And Others

    1988-01-01

    Describes an experiment that is to be performed midway in the first semester of an undergraduate organic chemistry laboratory coinciding with the students' introduction to cis-trans isomerism in the study of alkenes. Discusses the apparatus, materials, experimental procedure, historical significance, and results. (CW)

  5. Enyne Metathesis Catalyzed by Ruthenium Carbene Complexes

    DEFF Research Database (Denmark)

    Poulsen, Carina Storm; Madsen, Robert

    2003-01-01

    Enyne metathesis combines an alkene and an alkyne into a 1,3-diene. The first enyne metathesis reaction catalyzed by a ruthenium carbene complex was reported in 1994. This review covers the advances in this transformation during the last eight years with particular emphasis on methodology...

  6. Kinetic analysis of the rotation rate of light-driven unidirectional molecular motors

    NARCIS (Netherlands)

    Klok, Martin; Browne, Wesley R.; Feringa, Ben L.

    2009-01-01

    The combination of a photochemical and a thermal equilibrium in overcrowded alkenes, which is the basis for unidirectional rotation of light-driven molecular rotary motors, is analysed in relation to the actual average rotation rates of such structures. Experimental parameters such as temperature,

  7. Preparation of Tetramethylguanidine-Functionalized Mesoporous ...

    African Journals Online (AJOL)

    The catalyst was characterized by various techniques including Diffuse Reflectance FTIR, 13C NMR, elemental analysis and simultaneous thermogravimetric and differential scanning calorimetry analyses. It was then screened in the epoxidation of electron deficient alkenes. The results obtained show that indeed the ...

  8. Production of advanced fuels and of chemicals by yeasts on the basis of second generation feedstocks

    NARCIS (Netherlands)

    Bont, de J.A.M.; Raab, A.; Schilling, M.; Tamame González, M.M.; los Ángeles Santos García, De M.; Martins Dos Santos, V.A.P.; Arjona Antolín, R.; Gutiérrez Gómez, P.

    2014-01-01

    The present invention relates to modified eukaryotic microbial cells that have been engineered for producing fermentation products such as fatty acids, 1-alcohols, [beta]- keto-acids and -alcohols, [beta]-hydroxyacids, 1,3-diols, trans-[Delta]2-fatty acids, alkenes, alkanes and derivatives thereof,

  9. Transition metal complexes supported on metal-organic frameworks for heterogeneous catalysts

    Energy Technology Data Exchange (ETDEWEB)

    Farha, Omar K.; Hupp, Joseph T.; Delferro, Massimiliano; Klet, Rachel C.

    2017-02-07

    A robust mesoporous metal-organic framework comprising a hafnium-based metal-organic framework and a single-site zirconium-benzyl species is provided. The hafnium, zirconium-benzyl metal-organic framework is useful as a catalyst for the polymerization of an alkene.

  10. "Decarbonization" of an imino N-heterocyclic carbene via triple benzyl migration from hafnium

    Science.gov (United States)

    An imino N-heterocyclic carbene underwent three sequential benzyl migrations upon reaction with tetrabenzylhafnium, resulting in complete removal of the carbene carbon from the ligand. The resulting eneamido-amidinato hafnium complex showed alkene polymerization activity comparable to that of a prec...

  11. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Homogeneous oxidation of alcohol and alkene with copper (II) complex in water · HAKAN ÜNVER IBRAHIM KANI · More Details Abstract Fulltext PDF .... Article ID 39. Evaluation of micellar properties of sodium dodecylbenzene sulphonate in the presence of some salts · ASHWANI KUMAR SOOD MEENU AGGARWAL.

  12. Allosteric Regulation of the Rotational Speed in a Light-Driven Molecular Motor

    NARCIS (Netherlands)

    Faulkner, Adele; van Leeuwen, Thomas; Feringa, Ben L; Wezenberg, Sander J

    2016-01-01

    The rotational speed of an overcrowded alkene-based molecular rotary motor, having an integrated 4,5-diazafluorenyl coordination motif, can be regulated allosterically via the binding of metal ions. DFT calculations have been used to predict the relative speed of rotation of three different (i.e.

  13. Hoveyda-Grubbs type metathesis catalyst immobilized on mesoporous molecular sieves MCM-41 and SBA-15

    Czech Academy of Sciences Publication Activity Database

    Balcar, Hynek; Shinde, Tushar; Žilková, Naděžda; Bastl, Zdeněk

    2011-01-01

    Roč. 7, January (2011), s. 22-28 ISSN 1860-5397 R&D Projects: GA AV ČR IAA400400805; GA AV ČR KAN100400701 Institutional research plan: CEZ:AV0Z40400503 Keywords : alkene metathesis * catalyst immobilization * hybrid catalysis Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 2.517, year: 2011

  14. Molecular Modeling of Alkyl and Alkenyl Mono layers on Hydrogen-Terminated Si(111)

    NARCIS (Netherlands)

    Scheres, L.M.W.; Rijksen, B.M.G.; Giesbers, M.; Zuilhof, H.

    2011-01-01

    On H-Si(111) surfaces monolayer formation with 1-alkenes results in alkyl monolayers with a Si-C-C linkage, while 1-alkynes yield alkenyl monolayers with a Si-C-C linkage. Recently, considerable structural differences between both types of monolayers were observed, including an increased thickness,

  15. Side-chain liquid-crystalline poly(ketone)s : effect of spacer length, mesogen type and mesogen density on mesomorphic behavior

    NARCIS (Netherlands)

    Nieuwhof, R.P.; Marcelis, A.T.M.; Sudhölter, E.J.R.; Wursche, R.; Rieger, B.

    2000-01-01

    Novel side-chain liquid-crystalline copolymers (SCLCPs) were synthesized via the Pd(II) catalyzed alternating copolymerization of mesogenic 1-alkenes and carbon monoxide. For methoxybiphenyl mesogens, these copolymers exhibited highly ordered smectic E mesophases and high glass transition

  16. Using Molecular Modeling to Understand Some of the More Subtle Aspects of Aromaticity and Antiaromaticity

    Science.gov (United States)

    Box, Vernon G. S.

    2011-01-01

    pi-Electron delocalization exerts one of the most significant structure or energy influences in organic chemistry. Apart from determining the shapes of alkenes and alkynes, the planarity of aromatic molecules is a hallmark of pi-electron delocalization. Huckel's rules for aromaticity are easily applied in the teaching of undergraduates, but…

  17. Comparative Studies of Gasoline Samples Used in Nigeria *1U.Z ...

    African Journals Online (AJOL)

    INTRODUCTION. Gasoline is obtained from crude oil through blending of atmospheric distillation naphtha and products from other complex refinery processes (Handwerk, ... and catalytic reforming (Handwerk, 2001). The typical composition of gasoline hydrocarbons (% volume) is: 4-8% alkanes; 2-5% alkenes; 25-40% iso-.

  18. Electrophilic Selenium Catalysis with Electrophilic N-F Reagents as the Oxidants.

    Science.gov (United States)

    Guo, Ruizhi; Liao, Lihao; Zhao, Xiaodan

    2017-05-19

    A suitable oxidative system is crucial to electrophilic selenium catalysis (ESC). This short review offers the overview of recent development in ESC with electrophilic N-F reagents as the oxidants. Several highly selective transformations of alkenes such as allylic or vinylic imidation, pyridination, syn -dichlorination, oxidative cyclization and asymmetric cyclization have been described.

  19. Catálise assimétrica na ciclopropanação de olefinas Asymmetric catalysis in the cyclopropanation of olefins

    Directory of Open Access Journals (Sweden)

    Raquel A. C. Leão

    2007-01-01

    Full Text Available The main methodologies in the asymmetric cyclopropanation of alkenes with emphasis on asymmetric catalysis are covered. Exemples are the Simmons-Smith reaction, the use of diazoalkanes and reactions carried out by decomposition of alpha-diazoesters in the presence of transition metals.

  20. A new Organopalladium compound containing four Iron (III ...

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences; Volume 128; Issue 3. A new Organopalladium compound containing four Iron (III) Porphyrins for the selective oxidation of alkanes/alkenes by t-BuOOH. Manoj Kumar Singh Debkumar Bandyopadhyay. Regular Articles Volume 128 Issue 3 March 2016 pp 383-389 ...

  1. (S)-Garner aldehyde derived Baylis-Hillman adduct: A potential ...

    Indian Academy of Sciences (India)

    organic synthesis which involves the coupling of acti- vated vinylic system and an ... natural products. Moreover, the trisubstituted alkene moiety found abundantly in various naturally occur- ring bioactive molecules including important antibi- otics and pheromones is a ... Waters Micromass q-Tof Micro spectrometer. Elemen-.

  2. Adekoyeni (7)

    African Journals Online (AJOL)

    DELL

    alcohols, aldehydes, esters, alkenes, ketones, and amine while Ofada rice components include acids, alcohols, aldehydes, esters, alkanes, alkynes, ketones, phenol and others. The results showed high percentages of organic ..... of exogenous origin and usually found in milk fat from cow (Wolk et al., 2001). According to ...

  3. An Undergraduate Organic Chemistry Laboratory: The Facile Hydrogenation of Methyl Trans-Cinnamate

    Science.gov (United States)

    O'Connor, Kenneth J.; Zuspan, Kimberly; Berry, Lonnie

    2011-01-01

    Hydrogenation of alkenes is an important reaction in the synthesis of organic molecules. In this experiment, students conduct a high-yield microscale hydrogenation reaction of methyl "trans"-cinnamate using a readily available, safe, and convenient hydrogen source. The conditions are similar to those seen in an organic chemistry textbook for an…

  4. cyclo-addition reaction of triplet carbonyl compounds to substituted ...

    Indian Academy of Sciences (India)

    Abstract. Regioselectivity of the photochemical [2 + 2] cyclo-addition of triplet carbonyl compounds with a series of ground state electron-rich and electron-poor alkenes, the Paterno-Büchi reaction, is studied. Activation barriers for the first step of the triplet reaction are computed in the case of the O-attack. Next, the observed ...

  5. Metal-Organic Frameworks Stabilize Solution-Inaccessible Cobalt Catalysts for Highly Efficient Broad-Scope Organic Transformations.

    Science.gov (United States)

    Zhang, Teng; Manna, Kuntal; Lin, Wenbin

    2016-03-09

    New and active earth-abundant metal catalysts are critically needed to replace precious metal-based catalysts for sustainable production of commodity and fine chemicals. We report here the design of highly robust, active, and reusable cobalt-bipyridine- and cobalt-phenanthroline-based metal-organic framework (MOF) catalysts for alkene hydrogenation and hydroboration, aldehyde/ketone hydroboration, and arene C-H borylation. In alkene hydrogenation, the MOF catalysts tolerated a variety of functional groups and displayed unprecedentedly high turnover numbers of ∼2.5 × 10(6) and turnover frequencies of ∼1.1 × 10(5) h(-1). Structural, computational, and spectroscopic studies show that site isolation of the highly reactive (bpy)Co(THF)2 species in the MOFs prevents intermolecular deactivation and stabilizes solution-inaccessible catalysts for broad-scope organic transformations. Computational, spectroscopic, and kinetic evidence further support a hitherto unknown (bpy(•-))Co(I)(THF)2 ground state that coordinates to alkene and dihydrogen and then undergoing σ-complex-assisted metathesis to form (bpy)Co(alkyl)(H). Reductive elimination of alkane followed by alkene binding completes the catalytic cycle. MOFs thus provide a novel platform for discovering new base-metal molecular catalysts and exhibit enormous potential in sustainable chemical catalysis.

  6. Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis.

    Science.gov (United States)

    Manley, David W; Walton, John C

    2015-01-01

    Heterogeneous semiconductor photoredox catalysis (SCPC), particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can either (i) interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii) interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C-N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas.

  7. Oxidative decarboxylation of unsaturated fatty acids

    NARCIS (Netherlands)

    Klis, van der F.; Hoorn, van den M.H.; Blaauw, R.; Haveren, van J.; Es, van D.S.

    2011-01-01

    Long-chain internal olefins were prepared by silver(II)-catalyzed oxidative decarboxylation of unsaturated fatty acids by sodium peroxydisulfate. Similar to saturated carboxylic acids, 1-alkenes were the major decarboxylation product in the additional presence of copper(II), whereas in the absence

  8. A Series of Synthetic Organic Experiments Demonstrating Physical Organic Principles.

    Science.gov (United States)

    Sayed, Yousry; And Others

    1989-01-01

    Describes several common synthetic organic transformations involving alkenes, alcohols, alkyl halides, and ketones. Includes concepts on kinetic versus thermodynamic control of reaction, rearrangement of a secondary carbocation to a tertiary cation, and the effect of the size of the base on orientation during elimination. (MVL)

  9. The Synthesis and Crystal Structure of a Remarkable Binuclear, Double Pd–Cl–H–O–Pd Bridged Palladium Alcohol Complex. Catalytic Oxidations with Molecular Oxygen mediated by [{[Me2C(OH)CH2CONMe2]Pd(Cl)NO2}2

    NARCIS (Netherlands)

    Kiers, Niklaas H.; Kooijman, Huub; Spek, Anthony L.; Leeuwen, Piet W.N.M. van; Feringa, Bernard

    1992-01-01

    The Pd(Cl)NO2 complex of N,N-3-trimethyl-3-hydroxybutyramide is dimeric in the solid state with two Pd–Cl–H–O–Pd hydrogen-bond bridges; however, in solution the complex is monomeric and catalytically active in the oxidation of alkenes.

  10. Organic Lecture Demonstrations.

    Science.gov (United States)

    Silversmith, Ernest F.

    1988-01-01

    Provides a listing of 35 demonstrations designed to generate interest in organic chemistry and help put points across. Topics include opening lecture; molecular structure and properties; halogenation; nucleophilic substitution, alkenes and dienes, stereochemistry, spectroscopy, alcohols and phenols, aldehydes and ketones; carboxylic acids, amines,…

  11. Safety in the Chemical Laboratory: Tested Disposal Methods for Chemical Wastes from Academic Laboratories.

    Science.gov (United States)

    Armour, M. A.; And Others

    1985-01-01

    Describes procedures for disposing of dichromate cleaning solution, picric acid, organic azides, oxalic acid, chemical spills, and hydroperoxides in ethers and alkenes. These methods have been tested under laboratory conditions and are specific for individual chemicals rather than for groups of chemicals. (JN)

  12. DNA binding, anti-tumour activity and reactivity toward cell thiols of ...

    Indian Academy of Sciences (India)

    Ester 2 was shown to have a stronger cytostatic effect on leukemia cell line L1210 than alkene 1. The incubation of ligands 1 and 2 with the ovarian carcinoma cell line A2780 confirmed their extensive cytotoxic effects, an effect which was particularly pronounced in the case of ligand 2. Cytotoxicity tests against A2780 cells ...

  13. Synthesis and reduction of 2-nitroalkyl polysaccharide ethers

    NARCIS (Netherlands)

    Heeres, A.; Spoelma, F.F.; Doren, H.A. van; Gotlieb, K.F.; Bleeker, I.P.; Kellogg, R.M.

    2000-01-01

    Several 2-nitroalkyl polysaccharide ethers (from pullulan (1), guar (2), agarose (3), inulin (4), cellulose (5), Na-α-polyglucuronate (6) and hydroxyethyl cellulose (7)) were synthesized by reaction with 2-nitro-1-alkenes (2-nitro-1-propene and 2-nitro-1-butene) formed in situ from 2-nitroalkyl

  14. Synthesis and reduction of 2-nitroalkyl polysaccharide ethers

    NARCIS (Netherlands)

    Heeres, A; Spoelma, FF; van Doren, HA; Gotlieb, KF; Bleeker, IP; Kellogg, RM

    Several 2-nitroalkyl polysaccharide ethers (from pullulan (1), guar (2), agarose (3), inulin (4), cellulose (5), Na-alpha-polyglucuronate (6) and hydroxyethyl cellulose (7)) were synthesized by reaction with 2-nitro-1-alkenes (2-nitro-1-propene and 2-nitro-1-butene) formed in situ from 2-nitroalkyl

  15. Asymmetric Synthesis of (-)-Incarvillateine Employing an Intramolecular Alkylation via Rh-Catalyzed Olefinic C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Andy; Bergman, Robert; Ellman, Jonathan

    2008-02-18

    An asymmetric total synthesis of (-)-incarvillateine, a natural product having potent analgesic properties, has been achieved in 11 steps and 15.4% overall yield. The key step is a rhodium-catalyzed intramolecular alkylation of an olefinic C-H bond to set two stereocenters. Additionally, this transformation produces an exocyclic, tetrasubstituted alkene through which the bicyclic piperidine moiety can readily be accessed.

  16. Mass transfer effects in the H2SO4 catalyzed pivalic acid synthesis

    NARCIS (Netherlands)

    Brilman, D.W.F.; Meesters, N.G.; Swaaij, W.P.M. van; Versteeg, G.F.

    2001-01-01

    The synthesis of carboxylic acids from alkenes, carbon monoxide and water according to the Koch process is usually carried out in a stirred gas–liquid–liquid multiphase reactor. Due to the complex reaction system with fast, equilibrium reactions and fast, irreversible reactions the yield and product

  17. Mass transfer effects in H2SO4 catalyzed pivalic acid synthesis

    NARCIS (Netherlands)

    Brilman, Derk Willem Frederik; Meesters, N.G.; van Swaaij, Willibrordus Petrus Maria; Versteeg, Geert

    2001-01-01

    The synthesis of carboxylic acids from alkenes, carbon monoxide and water according to the Koch process is usually carried out in a stirred gas–liquid–liquid multiphase reactor. Due to the complex reaction system with fast, equilibrium reactions and fast, irreversible reactions the yield and product

  18. Non-metallocene rare-earth organometallic derivatives: synthesis, structure and application in the catalysis of transformations of unsaturated substrates

    International Nuclear Information System (INIS)

    Trifonov, A A

    2007-01-01

    The post-metallocene period of development of the chemistry of rare-earth organometallic compounds is analysed. The synthesis, structures and reactivities of complexes containing metal-carbon and metal-hydrogen bonds and stabilised by N-, P, and O-donor ligands are considered. The catalytic activities of these compounds in alkene polymerisation, hydroamination, hydrosilylation and hydroboration are discussed.

  19. Non-metallocene rare-earth organometallic derivatives: synthesis, structure and application in the catalysis of transformations of unsaturated substrates

    Energy Technology Data Exchange (ETDEWEB)

    Trifonov, A A [G.A. Razuvaev Institute of Organometallic Chemistry, Russian Academy of Sciences, Nizhnii Novgorod (Russian Federation)

    2007-11-30

    The post-metallocene period of development of the chemistry of rare-earth organometallic compounds is analysed. The synthesis, structures and reactivities of complexes containing metal-carbon and metal-hydrogen bonds and stabilised by N-, P, and O-donor ligands are considered. The catalytic activities of these compounds in alkene polymerisation, hydroamination, hydrosilylation and hydroboration are discussed.

  20. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Reaction of ,-unsaturated aromatic carboxylic acids with KBr and H2O2 in the presence of Na2MoO4 ⋅ H2O in aqueous medium affords -bromo alkenes in high yields. Metallocene dichlorides, Cp2MCl2 (M = Ti, Zr, or V) catalyse polymerisation of olefins in aqueous medium to afford high molecular weight polymers ...

  1. Non-metallocene rare-earth organometallic derivatives: synthesis, structure and application in the catalysis of transformations of unsaturated substrates

    Science.gov (United States)

    Trifonov, A. A.

    2007-11-01

    The post-metallocene period of development of the chemistry of rare-earth organometallic compounds is analysed. The synthesis, structures and reactivities of complexes containing metal-carbon and metal-hydrogen bonds and stabilised by N-, P, and O-donor ligands are considered. The catalytic activities of these compounds in alkene polymerisation, hydroamination, hydrosilylation and hydroboration are discussed.

  2. (SalenMn(III Catalyzed Asymmetric Epoxidation Reactions by Hydrogen Peroxide in Water: A Green Protocol

    Directory of Open Access Journals (Sweden)

    Francesco Paolo Ballistreri

    2016-07-01

    Full Text Available Enantioselective epoxidation reactions of some chosen reactive alkenes by a chiral Mn(III salen catalyst were performed in H2O employing H2O2 as oxidant and diethyltetradecylamine N-oxide (AOE-14 as surfactant. This procedure represents an environmentally benign protocol which leads to e.e. values ranging from good to excellent (up to 95%.

  3. Visible-Light-Driven Photoisomerization and Increased Rotation Speed of a Molecular Motor Acting as a Ligand in a Ruthenium(II) Complex

    NARCIS (Netherlands)

    Wezenberg, Sander J.; Chen, Kuang-Yen; Feringa, Ben L.

    2015-01-01

    Toward the development of visible-light-driven molecular rotary motors, an overcrowded alkene-based ligand and the corresponding ruthenium(II) complex is presented. In our design, a 4,5-diazafluorenyl coordination motif is directly integrated into the motor function. The photochemical and thermal

  4. Ultrafast isomerization dynamics of a unidirectional molecular rotor revealed by femtosecond stimulated raman spectroscopy (FSRS)

    NARCIS (Netherlands)

    Hall, Christopher R.; Conyard, Jamie; Laptenok, Siarhei; Browne, Wesley R.; Feringa, Ben L.; Heisler, Ismael A.; Meech, Stephen R.

    2016-01-01

    Unidirectional molecular rotors based on chiral overcrowded alkenes operate via sequential photochemical- and thermal-activated steps. Over the last decade the rotation rate limiting thermal step has been optimized through modification of the molecular structure. In recent years we have shown the

  5. Light-driven rotary molecular motors : an ultrafast optical study

    NARCIS (Netherlands)

    Augulis, Ramunas; Klok, Martin; Feringa, Ben L.; van Loosdrecht, Paul H. M.; Itoh, T; Tanaka, K; Schreiber, M

    2009-01-01

    Molecular rotary motors, though common in nature, were first synthesized rather recently. One of the most promising categories of light-driven rotary molecular motors which allow for optical control is based on helical overcrowded alkenes. In this category of motors, the rotation of the motor's

  6. DFT Investigation of the Palladium-Catalyzed Ene-Yne Coupling

    DEFF Research Database (Denmark)

    Henriksen, Signe Teuber; Tanner, David Ackland; Skrydstrup, T.

    2010-01-01

    The mechanism of the recently developed palladium-catalyzed ene-yne coupling has been evaluated by DFT methods. The calculations validate the previously proposed reaction mechanism and explain the stereoselectivity of the reaction (exclusive formation of the E isomer of the disubstituted alkene)....

  7. Unprecedented Selective Oxidation of Styrene Derivatives using a Supported Iron Oxide Nanocatalyst in Aqueous Medium

    Science.gov (United States)

    Iron oxide nanoparticles supported on mesoporous silica-type materials have been successfully utilized in the aqueous selective oxidation of alkenes under mild conditions using hydrogen peroxide as a green oxidant. Catalysts could be easily recovered after completion of the reac...

  8. Modern Reduction Methods

    CERN Document Server

    Andersson, Pher G

    2008-01-01

    With its comprehensive overview of modern reduction methods, this book features high quality contributions allowing readers to find reliable solutions quickly and easily. The monograph treats the reduction of carbonyles, alkenes, imines and alkynes, as well as reductive aminations and cross and heck couplings, before finishing off with sections on kinetic resolutions and hydrogenolysis. An indispensable lab companion for every chemist.

  9. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Hydroxyphthalimide (NHPI) Combined with CoTPP-Zn2sub>Al-LDH · WEIYOU ZHOU ... Highly efficient epoxidation of alkenes with m-chloroperbenzoic acid catalyzed by nanomagnetic Co(III)@Fe₃O₄/SiO₂ salen complex · ALI ALLAHRESANI ...

  10. Tetramethyl(perfluoroalkyl)cyclopentadienyl Rhodium(I) Complexes with Ethylene or Diene Ligands. Crystal Structure of [(eta-5-C5Me4C6F13)Rh(CO)2

    Czech Academy of Sciences Publication Activity Database

    Čermák, Jan; Krupková, Alena; Auerová, Kateřina; Zamrzla, M.; Nguyen Thi, T.H.; Vojtíšek, P.; Císařová, I.

    2010-01-01

    Roč. 695, č. 3 (2010), s. 375-381 ISSN 0022-328X R&D Projects: GA AV ČR IAA4072203; GA MŠk(CZ) LC06070 Institutional research plan: CEZ:AV0Z40720504 Keywords : fluorous cyclopentadienes * rhodium complexes * alkene complexes Subject RIV: CC - Organic Chemistry Impact factor: 2.205, year: 2010

  11. Aza-Morita–Baylis–Hillman reaction of maleimides with ...

    Indian Academy of Sciences (India)

    ... preparation of bile pigments,17 and of several classes of bioactive nat- ural compounds with a wide range of activity.13(b),18. Figure 1 shows some of the pyrrole-based bioactive natural products. During the course of our investigations, we found that maleimides act as activated alkenes in the MBH reaction to synthesize ...

  12. Synthesis and Antioxidant Activity of 3,3'-Diselanediylbis (N,N ...

    African Journals Online (AJOL)

    Aseries of novel diselenides 5a–e were synthesized from-haloketones, α-picoline alkenes and various secondary amines under a dry nitrogen atmosphere. The structures of these compounds were established by means of their spectral data and they were screened for scavenging activity against 1 ...

  13. Enantioselective Copper-Catalyzed Arylation-Driven Semipinacol Rearrangement of Tertiary Allylic Alcohols with Diaryliodonium Salts.

    Science.gov (United States)

    Lukamto, Daniel H; Gaunt, Matthew J

    2017-07-12

    A copper-catalyzed enantioselective arylative semipinacol rearrangement of allylic alcohols using diaryliodonium salts is reported. Chiral Cu(II)-bisoxazoline catalysts initiate an electrophilic alkene arylation, triggering a 1,2-alkyl migration to afford a range of nonracemic spirocyclic ketones with high yields, diastereo- and enantioselectivities.

  14. Dehydration of Methylcyclohexanol Isomers in the Undergraduate Organic Laboratory and Product Analysis by Gas Chromatography-Mass Spectroscopy (GC-MS)

    Science.gov (United States)

    Clennan, Malgorzata M.; Clennan, Edward L.

    2011-01-01

    Dehydrations of "cis"- and "trans"-2-methylcyclohexanol mixtures were carried out with 60% sulfuric acid at 78-80 [degrees]C as a function of time and the products were identified by gas chromatography-mass spectroscopy (GC-MS) analysis. The compounds identified in the reaction mixtures include alkenes, 1-, 3-, and 4-methylcyclohexenes and…

  15. Percutaneous nephrolithotripsy under assisted local anaesthesia for ...

    African Journals Online (AJOL)

    T.KH. Fathelbab

    fluoroscopy using high pressure balloon catheter in 35 and Alken's metal dilators in 12 cases. Stones were then retrieved after disintegration in the same cession in 33 patients, while the other 14 patients underwent staged PNL, where a 12 Fr. nephrostomy tube was placed in the first stage, followed by tract dilatation and.

  16. Synthesis and Antimicrobial Activity of the Essential Oil Compounds ...

    African Journals Online (AJOL)

    NICO

    2012-08-26

    Aug 26, 2012 ... Essential oil constituent, (E)- and (Z)-3-hexenyl nonanoate, antimicrobial, ester synthesis, acid-induced alkene isomerizations. Numerous studies and reviews on the subject matter of com- pounds isolated from plants have demonstrated that essential oil compounds display antimicrobial activity1–7.

  17. Copolymerization of Ethene and Functionalized Comonomers with Cationic α-Diimine Palladium Catalysts

    NARCIS (Netherlands)

    Li, Weidong

    2008-01-01

    Polyolefins form a highly important class of materials, with a wide range of applications, which are produced industrially on a huge scale (> 85 Mton per year). By far the largest volume of these polyolefins is polyethene (HDPE) and its copolymers with 1-alkenes (LLDPE), and isotactic polypropene.

  18. Alkenenitrile Transmissive Olefination: Synthesis of the Putative Lignan "Morinol I"

    Science.gov (United States)

    Fleming, Fraser F.; Liu, Wang; Yao, Lihua; Pitta, Bhaskar; Purzycki, Matthew; Ravikumar, P. C.

    2012-01-01

    Grignard reagents trigger an addition-elimination with α'-hydroxy acrylonitriles to selectively generate Z-alkenenitriles. The modular assembly of Z-alkenenitriles from a Grignard reagent, acrylonitrile, and an aldehyde is ideal for stereoselectively synthesizing alkenes as illustrated in the synthesis of the putative lignan "morinol I." PMID:22545004

  19. Asymmetric Synthesis of Second-Generation Light-Driven Molecular Motors

    NARCIS (Netherlands)

    van Leeuwen, Thomas; Danowski, Wojciech; Otten, Edwin; Wezenberg, Sander J; Feringa, Ben L

    2017-01-01

    The enantiomeric homogeneity of light-driven molecular motors based on overcrowded alkenes is crucial in their application as either unidirectional rotors or as chiral multistate switches. It was challenging to obtain these compounds as single enantiomers via the established synthetic procedures due

  20. Olefination of carbonyl compounds: modern and classical methods

    Energy Technology Data Exchange (ETDEWEB)

    Korotchenko, V N; Nenajdenko, Valentine G; Balenkova, Elizabeth S [Department of Chemistry, M.V. Lomonosov Moscow State University, Moscow (Russian Federation); Shastin, Aleksey V [Institute of Problems of Chemical Physics, Russian Academy of Sciences, Chernogolovka, Moscow Region (Russian Federation)

    2004-10-31

    The published data on the methods for alkene synthesis by olefination of carbonyl compounds are generalised and systematised. The main attention is given to the use of transition metals and organoelement compounds. The review covers the data on both classical and newly developed methods that are little known to chemists at large.

  1. Generation of Stoichiometric Ethylene and Isotopic Derivatives and Application in Transition Metal-Catalyzed Vinylation and Enyne Metathesis

    DEFF Research Database (Denmark)

    Min, Geanna; Bjerglund, Klaus Meier; Kramer, Søren

    2013-01-01

    labeled ethylene, from simple alkene precursors by using Ru catalysis. Applying a two-chamber reactor allows both the synthesis of ethylene and its immediate consumption in a chemical transformation permitting reactions to be performed with only stoichiometric amounts of this two carbon olefin...

  2. Olefination of carbonyl compounds: modern and classical methods

    Science.gov (United States)

    Korotchenko, V. N.; Nenajdenko, Valentine G.; Balenkova, Elizabeth S.; Shastin, Aleksey V.

    2004-10-01

    The published data on the methods for alkene synthesis by olefination of carbonyl compounds are generalised and systematised. The main attention is given to the use of transition metals and organoelement compounds. The review covers the data on both classical and newly developed methods that are little known to chemists at large.

  3. Hybrid diphosphorus ligands in rhodium catalysed asymmetric hydroformylation

    NARCIS (Netherlands)

    Chikkali, S.H.; van der Vlugt, J.I.; Reek, J.N.H.

    2014-01-01

    This review aims to illustrate recent advances in the application of hybrid diphosphorus ligands for the Rh catalysed hydroformylation of alkenes, discussing the most prevalent classes of hybrid systems, i.e. phosphine-phosphinite, phosphine-phosphonite, phosphine-phosphite,

  4. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    Home; Journals; Journal of Chemical Sciences. R H DUNCAN LYNGDOH. Articles written in Journal of Chemical Sciences. Volume 128 Issue 5 May 2016 pp 681-693 Regular Articles. Uncatalyzed thermal gas phase aziridination of alkenes by organic azides. Part I: Mechanisms with discrete nitrene species · S PREMILA ...

  5. N-halossacarinas: reagentes úteis (e alternativos em síntese orgânica

    Directory of Open Access Journals (Sweden)

    Soraia P. L. de Souza

    2006-10-01

    Full Text Available N-halosaccharins proved to be useful and alternative reagents for diverse organic transformations, such as halogenation of aromatic compounds, benzylic and alpha-carbonylic positions, cohalogenation of alkenes, oxidation of secondary alcohols, etc. Their preparation from saccharin, a cheap and readly available starting material, is simple.

  6. Silyl-Heck Reactions for the Preparation of Unsaturated Organosilanes.

    Science.gov (United States)

    Martin, Sara E S; Watson, Donald A

    2013-01-01

    Few methods exist to directly install silyl functionality onto olefins. This Synpacts highlights the state of the art of the silyl-Heck reaction and our recently developed conditions for preparing allyl and vinyl silanes from terminal alkenes using this method.

  7. Chiral phosphines in nucleophilic organocatalysis

    Directory of Open Access Journals (Sweden)

    Yumei Xiao

    2014-09-01

    Full Text Available This review discusses the tertiary phosphines possessing various chiral skeletons that have been used in asymmetric nucleophilic organocatalytic reactions, including annulations of allenes, alkynes, and Morita–Baylis–Hillman (MBH acetates, carbonates, and ketenes with activated alkenes and imines, allylic substitutions of MBH acetates and carbonates, Michael additions, γ-umpolung additions, and acylations of alcohols.

  8. Morita-Baylis-Hillman reaction of acrylamide with isatin derivatives.

    Science.gov (United States)

    Singh, Radhey Mohan; Bharadwaj, Kishor Chandra; Tiwari, Dharmendra Kumar

    2014-01-01

    The Morita-Baylis-Hillman reaction of acrylamide, as an activated alkene, has seen little development due to its low reactivity. We have developed the reaction using isatin derivatives with acrylamide, DABCO as a promoter and phenol as an additive in acetonitrile. The corresponding aza version with acrylate and acrylonitrile has also been developed resulting in high product yields.

  9. Preparative semiconductor photoredox catalysis: An emerging theme in organic synthesis

    Directory of Open Access Journals (Sweden)

    David W. Manley

    2015-09-01

    Full Text Available Heterogeneous semiconductor photoredox catalysis (SCPC, particularly with TiO2, is evolving to provide radically new synthetic applications. In this review we describe how photoactivated SCPCs can either (i interact with a precursor that donates an electron to the semiconductor thus generating a radical cation; or (ii interact with an acceptor precursor that picks up an electron with production of a radical anion. The radical cations of appropriate donors convert to neutral radicals usually by loss of a proton. The most efficient donors for synthetic purposes contain adjacent functional groups such that the neutral radicals are resonance stabilized. Thus, ET from allylic alkenes and enol ethers generated allyl type radicals that reacted with 1,2-diazine or imine co-reactants to yield functionalized hydrazones or benzylanilines. SCPC with tertiary amines enabled electron-deficient alkenes to be alkylated and furoquinolinones to be accessed. Primary amines on their own led to self-reactions involving C–N coupling and, with terminal diamines, cyclic amines were produced. Carboxylic acids were particularly fruitful affording C-centered radicals that alkylated alkenes and took part in tandem addition cyclizations producing chromenopyrroles; decarboxylative homo-dimerizations were also observed. Acceptors initially yielding radical anions included nitroaromatics and aromatic iodides. The latter led to hydrodehalogenations and cyclizations with suitable precursors. Reductive SCPC also enabled electron-deficient alkenes and aromatic aldehydes to be hydrogenated without the need for hydrogen gas.

  10. Covalently Attached Organic Monolayers onto Silicon Carbide from 1-Alkynes: Molecular Structure and Tribological Properties

    NARCIS (Netherlands)

    Pujari, S.P.; Scheres, L.M.W.; Weidner, T.; Baio, J.E.; Cohen Stuart, M.A.; Rijn, van C.J.M.; Zuilhof, H.

    2013-01-01

    In order to achieve improved tribological and wear properties at semiconductor interfaces, we have investigated the thermal grafting of both alkylated and fluorine-containing ((CxF2x+1)–(CH2)n-) 1-alkynes and 1-alkenes onto silicon carbide (SiC). The resulting monolayers display static water contact

  11. Platinum-catalyzed hydroformylation of terminal and internal octenes

    NARCIS (Netherlands)

    van Duren, R.; van der Vlugt, J.I.; Kooijman, H.; Spek, A.L.; Vogt, D.

    2007-01-01

    A brief historic overview of Pt/Sn-catalyzed hydroformylation as well as recent advances in the hydroformylation of internal alkenes is provided. This serves as background for the results obtained with the [Pt(Sixantphos)Cl2] system, for which the molecular structure and the spectroscopic data are

  12. Percutaneous nephrolithotripsy under assisted localanaesthesia for ...

    African Journals Online (AJOL)

    Narcotics were given 30 min prior to the procedure and medazolam was given intraoperatively upondemand. Utrasound guided puncture was performed in all cases and tract dilatation was then done underfluoroscopy using high pressure balloon catheter in 35 and Alken's metal dilators in 12 cases. Stones werethen ...

  13. Volatile aromatic components of two varieties of parboiled Nigerian ...

    African Journals Online (AJOL)

    The compounds were extracted using the solvent extraction method and the concentrated extract was analysed with Gas Chromatography-Mass Spectrometry. Some of the volatile compounds varied with the varieties. The classification of components in Caroline rice are organic acids, alcohols, aldehydes, esters, alkenes, ...

  14. Isomerization Reactions of Allylic Alcohols into Ketones with the Grubbs Reagent

    Directory of Open Access Journals (Sweden)

    Motoo Tori

    2004-06-01

    Full Text Available Allylic alcohols were isomerized into ketones by the action of the Grubbs reagent. Some model alcohols were prepared and tested under similar conditions to reveal that less substituted alkenes rearrange more easily. More hindered alcohols are stable under these conditions, however, the simple allylic alcohols tend to isomerize producing ethyl ketone and the corresponding degraded methyl ketone.

  15. Journal of Chemical Sciences | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    In this method, reduction of keto and alkene functional groups has been achieved in a single step using low cost catalyst NiCl2/NaBH4 in methanol. ... Department of Chemistry, JNTUH College of Engineering Jagtial, Karimnagar 505 501, India; R&D Division, Aspen Bio Pharma Labs Pvt. Ltd, Genome Vally, Turkapally, ...

  16. Pd-catalyzed Z-selective semihydrogenation of alkynes: determining the type of active species

    NARCIS (Netherlands)

    Drost, R.M.; Rosar, V.; Marta, S.D.; Lutz, M.; Demitri, N.; Milani, B.; de Bruin, B.; Elsevier, C.J.

    2015-01-01

    A protocol was developed to distinguish between well-defined molecular and nanoparticle-based catalysts for the Pd-catalyzed semihydrogenation reaction of alkynes to Z-alkenes. The protocol applies quantitative partial poisoning and dynamic light scattering methods, which allow the institution of

  17. Pd-Catalyzed Z-Selective Semihydrogenation of Alkynes : Determining the Type of Active Species

    NARCIS (Netherlands)

    Drost, Ruben M.; Rosar, Vera; Marta, Silvia Dalla; Lutz, Martin; Demitri, Nicola; Milani, Barbara; De Bruin, Bas; Elsevier, Cornelis J.

    2015-01-01

    A protocol was developed to distinguish between well-defined molecular and nanoparticle-based catalysts for the Pd-catalyzed semihydrogenation reaction of alkynes to Z-alkenes. The protocol applies quantitative partial poisoning and dynamic light scattering methods, which allow the institution of

  18. Water-soluble diphosphadiazacyclooctanes as ligands for aqueous organometallic catalysis

    KAUST Repository

    Boulanger, Jérôme

    2012-12-01

    Two new water-soluble diphosphacyclooctanes been synthesized and characterized by NMR and surface tension measurements. Both phosphanes proved to coordinate rhodium in a very selective way as well-defined bidentates were obtained. When used in Rh-catalyzed hydroformylation of terminal alkenes, both ligands positively impacted the reaction chemoselectivity. © 2012 Elsevier B.V.

  19. Chemical analysis of Agbabu Bitumen Exudate as potential refinery ...

    African Journals Online (AJOL)

    The proportions of the constituents in the bitumen were 44.59 % cyclop-araffin, 28.61 % alkanes, 3.47 % monoaromatic hydrocarbons, 6.44 % alkenes, 3.23 % nitrogen compounds, 1.95 % sulphur compounds and 4.27 % oxygen compounds. The composition compared favourably to the resp-ective percent ranges in ...

  20. A Mnemonic for Ozonolysis

    Science.gov (United States)

    Ruekberg, Ben

    2011-01-01

    Many students find product prediction in ozonolysis reactions of alkenes and alkynes difficult, and they often have greater difficulty discerning the starting compounds when presented with ozonolysis products. The mnemonic device suggested here can help students figure out what the ozonolysis product (or products) will be. Once mastered, this…

  1. Morita–Baylis–Hillman reaction of acrylamide with isatin derivatives

    Directory of Open Access Journals (Sweden)

    Radhey M. Singh

    2014-12-01

    Full Text Available The Morita–Baylis–Hillman reaction of acrylamide, as an activated alkene, has seen little development due to its low reactivity. We have developed the reaction using isatin derivatives with acrylamide, DABCO as a promoter and phenol as an additive in acetonitrile. The corresponding aza version with acrylate and acrylonitrile has also been developed resulting in high product yields.

  2. Co-factor regeneration in the production of 1,2-epoxypropane by Mycobacterium strain E3: the role of storage material.

    NARCIS (Netherlands)

    Haan, de A.; Smit, M.R.; Voorhorst, W.G.B.; Bont, de J.A.M.

    1993-01-01

    When grown on ethene Mycobacterium strain E3 produces epoxyalkanes from alkenes in an oxygen- and NADH-dependent reaction. The process of co-factor regeneration was studied by analysing the intracellular pools of NADH and storage material during the production of 1,2-epoxypropane from propene. With

  3. Rhodium(III)-Catalyzed Ortho-Alkenylation of Anilines Directed by a Removable Boc-Protecting Group.

    Science.gov (United States)

    Morita, Tomohiro; Satoh, Tetsuya; Miura, Masahiro

    2017-04-07

    The rhodium(III)-catalyzed ortho-alkenylation of N-Boc-anilines with alkenes such as acrylate ester and styrene proceeds smoothly through C-H bond cleavage. Obtained o-alkenylanilines can be readily transformed to nitrogen-containing fused heteroaromatic compounds including indoles and quinolines.

  4. Tetrameric DABCO™-Bromine: an Efficient and Versatile Reagent ...

    African Journals Online (AJOL)

    Tetrameric DABCO™-bromine is a powerful brominating agent but shows reasonable selectivity with certain substrates. The selective bromination for activated aromatic compounds and alkenes is reported. Synthesis of -bromo ketones and nitriles has also been achieved by using this reagent and the results are also ...

  5. Chloride ion-catalyzed generation of difluorocarbene for efficient preparation of gem-difluorinated cyclopropenes and cyclopropanes

    KAUST Repository

    Wang, Fei

    2011-01-01

    A chloride ion-catalyzed generation of difluorocarbene from a relatively non-toxic and inexpensive precursor, Me3SiCF2Cl (1), under mild and neutral conditions leads to an efficient preparation of gem-difluorocyclopropenes and difluorocyclopropanes through [2 + 1] cycloaddition reactions with alkynes and alkenes, respectively. © 2011 The Royal Society of Chemistry.

  6. South African Journal of Chemistry - Vol 60 (2007)

    African Journals Online (AJOL)

    The Synthesis of 5-, 6-, 7- and 8-Membered Oxygen-containing Benzo-fused Rings using Alkene Isomerization and Ring-closing Metathesis Reactions · EMAIL FREE FULL TEXT EMAIL FREE FULL TEXT DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT. R Pathak, J Panayides, TD Jeftic, CB de Koning, WAL van Otterlo ...

  7. Recent developments in isobutane/olefin alkylation

    Energy Technology Data Exchange (ETDEWEB)

    Lercher, J.A.; Feller, A. [Inst. fuer Technische Chemie, Technische Univ. Muenchen (Germany)

    2002-07-01

    The isobutane/alkene alkylation is reviewed with respect to recent process developments based on liquid and solid acid catalysts. A brief overview about the established processes is given followed by the description of new processes based on solid acids under development. (orig.)

  8. Hydride transfer versus deprotonation kinetics in the isobutane−propene alkylation reaction : A computational study

    NARCIS (Netherlands)

    Liu, Chong; Van Santen, Rutger A.; Poursaeidesfahani, A.; Vlugt, T.J.H.; Pidko, Evgeny A.; Hensen, Emiel J M

    2017-01-01

    The alkylation of isobutane with light alkenes plays an essential role in modern petrochemical processes for the production of high-octane gasoline. In this study we have employed periodic DFT calculations combined with microkinetic simulations to investigate the complex reaction mechanism of

  9. Industrial tests of a new technology for sulfuric acid alkylation of isobutane by olefines

    Energy Technology Data Exchange (ETDEWEB)

    Tarakanov, V.S.; Karamyshev, M.S.; Khadzhiyev, S.N.; Mel' man, A.Z.

    1971-01-01

    A complex of elements of a new technology for sulfuric acid alkylation of isobutane by alkenes with the use of a KSG-2 reactor and an acetic settler of a new design is realized as a result of the joint work of the Novo-Yaroslav oil refinery, GrozNII, VNIIOINeft and VNIINeftemash in an alkylation installation.

  10. Isobutane/olefin alkylation - present state and recent developments

    Energy Technology Data Exchange (ETDEWEB)

    Feller, A.; Lercher, J.A. [Inst. fuer Technische Chemie, Technische Univ. Muenchen (Germany)

    2002-12-01

    Isobutane/alkene alkylation is reviewed with respect to recent process developments based on liquid and solid acid catalysts. The reaction mechanism and its consequences for both liquid and solid acid based processes is briefly discussed. Established liquid acid catalyzed processes are introduced followed by the description of new processes based on solid acids, which are currently under development. (orig.)

  11. Fulltext PDF

    Indian Academy of Sciences (India)

    Number system primarily using 0 and"I (6). 13. The sun, for e.g. (4). 16. Nourishment for a growing embryo (4). 17. Alkene (6). 18. Relating to the area of part shadow in an eclipse (9). Solutions will appear in a subsequent issue. DOWN. 1. One gram molecular weight in solution? (5). 2. Uncharged but heavy part of atom (7).

  12. 4-Oxalocrotonate tautomerase, its homologue YwhB, and active vinylpyruvate hydratase : Synthesis and evaluation of 2-fluoro substrate analogues

    NARCIS (Netherlands)

    Johnson, William H; Wang, Susan C; Stanley, Thanuja M; Czerwinski, Robert M; Almrud, Jeffrey J; Poelarends, Gerrit J; Murzin, Alexey G; Whitman, Christian P

    2004-01-01

    A series of 2-fluoro-4-alkene and 2-fluoro-4-alkyne substrate analogues were synthesized and examined as potential inhibitors of three enzymes: 4-oxalocrotonate tautomerase (4-OT) and vinylpyruvate hydratase (VPH) from the catechol meta-fission pathway and a closely related 4-OT homologue found in

  13. Pt0.02Sn0.003Mg0.06 on γ-alumina: a stable catalyst for oxidative dehydrogenation of ethane

    NARCIS (Netherlands)

    de Graaff, E.A.; Rothenberg, G.; Kooyman, P.J.; Andreini, A.; Bliek, A.

    2005-01-01

    The advantages of two-step oxidative dehydrogenation as an alternative method for manufacturing small alkenes are outlined. In a nutshell, the process is based on separating the gaseous oxygen and hydrocarbon feeds in time. In the first step, alkanes are dehydrogenated in the presence of a solid

  14. On the Absorption of Isobutene and trans-2-Butene in Sulfuric Acid Solutions

    NARCIS (Netherlands)

    Brilman, D.W.F.; Swaaij, W.P.M. van; Versteeg, G.F.

    1997-01-01

    In reactions in which alkenes react in the presence of homogeneous Brønstedt acid catalysts, the protonation step is rate determining. Existing reaction rate correlations for protonation of butenes in sulfuric acid solutions are not consistent and limited to sulfuric acid concentrations below 80 wt

  15. Photochemical Grafting and Patterning of Organic Monolayers on Indium Tin Oxide Substrates

    NARCIS (Netherlands)

    Li, Y.; Zuilhof, H.

    2012-01-01

    Covalently attached organic layers on indium tin oxide (ITO) surfaces were prepared by the photochemical grafting with 1-alkenes. The surface modification was monitored with static water contact angle, X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) measurements.

  16. Photochemical attachment of organic monolayers onto H-terminated Si(111): Radical chain propagation observed via STM studies

    NARCIS (Netherlands)

    Eves, B.J.; Sun, Q.Y.; Lopinski, G.P.; Zuilhof, H.

    2004-01-01

    Photochemical reactions of terminal alkenes with hydrogen-terminated silicon surfaces are being used by many groups to produce covalently attached organic monolayers with a wide range of terminal functionalities. Despite the considerable activity in this area, the mechanism for these reactions has

  17. Development of Thermal and Photochemical Strategies for Thiol−Ene Click Polymer Functionalization

    NARCIS (Netherlands)

    Campos, Luis M.; Killops, Kato L.; Sakai, Ryosuke; Paulusse, Jos Marie Johannes; Damiron, Denis; Drockenmuller, Eric; Messmore, Benjamin W.; Hawker, Craig J.

    2008-01-01

    A series of alkene-functional polymers were synthesized by controlled polymerization techniques in order to investigate and compare the efficiency and orthogonality of both photochemically and thermally initiated thiol−ene click coupling reactions. The copolymers were designed to have single or

  18. Determination of lipid oxidation products in vegetable oils and marine omega-3 supplements

    Directory of Open Access Journals (Sweden)

    Rune Blomhoff

    2011-06-01

    Full Text Available Background : There is convincing evidence that replacing dietary saturated fats with polyunsaturated fats (PUFA decreases risk of cardiovascular diseases. Therefore, PUFA rich foods such as vegetable oils, fatty fish, and marine omega-3 supplements are recommended. However, PUFA are easily oxidizable and there is concern about possible negative health effects from intake of oxidized lipids. Little is known about the degree of lipid oxidation in such products. Objective : To assess the content of lipid oxidation products in a large selection of vegetable oils and marine omega-3 supplements available in Norway. Both fresh and heated vegetable oils were studied. Design : A large selection of commercially available vegetable oils and marine omega-3 supplements was purchased from grocery stores, pharmacies, and health food stores in Norway. The content of lipid oxidation products were measured as peroxide value and alkenal concentration. Twelve different vegetable oils were heated for a temperature (225°C and time (25 minutes resembling conditions typically used during cooking. Results : The peroxide values were in the range 1.04–10.38 meq/kg for omega-3 supplements and in the range 0.60–5.33 meq/kg for fresh vegetable oils. The concentration range of alkenals was 158.23–932.19 nmol/mL for omega-3 supplements and 33.24–119.04 nmol/mL for vegetable oils. After heating, a 2.9–11.2 fold increase in alkenal concentration was observed for vegetable oils. Conclusions : The contents of hydroperoxides and alkenals in omega-3 supplements are higher than in vegetable oils. After heating vegetable oils, a large increase in alkenal concentration was observed.

  19. Fuels characterization studies. [jet fuels

    Science.gov (United States)

    Seng, G. T.; Antoine, A. C.; Flores, F. J.

    1980-01-01

    Current analytical techniques used in the characterization of broadened properties fuels are briefly described. Included are liquid chromatography, gas chromatography, and nuclear magnetic resonance spectroscopy. High performance liquid chromatographic ground-type methods development is being approached from several directions, including aromatic fraction standards development and the elimination of standards through removal or partial removal of the alkene and aromatic fractions or through the use of whole fuel refractive index values. More sensitive methods for alkene determinations using an ultraviolet-visible detector are also being pursued. Some of the more successful gas chromatographic physical property determinations for petroleum derived fuels are the distillation curve (simulated distillation), heat of combustion, hydrogen content, API gravity, viscosity, flash point, and (to a lesser extent) freezing point.

  20. Clean-chemistry synthesis of 2-tetralones in a single-stage acylation-cycloalkylation process.

    Science.gov (United States)

    Gray, A D; Smyth, T P

    2001-10-19

    The preparation of substituted-2-tetralones by direct reaction of a 1-alkene with a substituted phenylacetic acid in a reaction system of trifluoroacetic anhydride (TFAA) and phosphoric acid is described. This single-stage process involves in situ formation of a mixed anhydride of the phenylacetic acid and acylation of the alkene by this species followed by cycloalkylation of the aromatic ring. This is a cleaner approach to the synthesis of 2-tetralones compared to Friedel-Crafts aliphatic acylation-cycloalkylation in that use of thionyl chloride, aluminum trichloride, and a chlorinated hydrocarbon solvent is eliminated. In addition, the atom efficiency is augmented by recovery of the spent TFAA as trifluoroacetic acid (TFA) and conversion of this back to TFAA by dehydration.

  1. Catalytic hydrogenation using complexes of base metals with tridentate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Hanson, Susan K.; Zhang, Guoqi; Vasudevan, Kalyan V.

    2017-02-14

    Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.

  2. Catalytic hydrogenation using complexes of base metals with tridentate ligands

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Kalyan V.; Zhang, Guoqi; Hanson, Susan K.

    2016-09-06

    Complexes of cobalt and nickel with tridentate ligand PNHP.sup.R are effective for hydrogenation of unsaturated compounds. Cobalt complex [(PNHP.sup.Cy)Co(CH.sub.2SiMe.sub.3)]BAr.sup.F.sub.4 (PNHP.sup.Cy=bis[2-(dicyclohexylphosphino)ethyl]amine, BAr.sup.F.sub.4=B(3,5-(CF.sub.3).sub.2C.sub.6H.sub.3).sub.4)) was prepared and used with hydrogen for hydrogenation of alkenes, aldehydes, ketones, and imines under mild conditions (25-60.degree. C., 1-4 atm H.sub.2). Nickel complex [(PNHP.sup.Cy)Ni(H)]BPh.sub.4 was used for hydrogenation of styrene and 1-octene under mild conditions. (PNP.sup.Cy)Ni(H) was used for hydrogenating alkenes.

  3. An efficient Pd–NHC catalyst system in situ generated from Na2PdCl4 and PEG-functionalized imidazolium salts for Mizoroki–Heck reactions in water

    Directory of Open Access Journals (Sweden)

    Nan Sun

    2017-08-01

    Full Text Available Three PEG-functionalized imidazolium salts L1–L3 were designed and prepared from commercially available materials via a simple method. Their corresponding water soluble Pd–NHC catalysts, in situ generated from the imidazolium salts L1–L3 and Na2PdCl4 in water, showed impressive catalytic activity for aqueous Mizoroki–Heck reactions. The kinetic study revealed that the Pd catalyst derived from the imidazolium salt L1, bearing a pyridine-2-methyl substituent at the N3 atom of the imidazole ring, showed the best catalytic activity. Under the optimal conditions, a wide range of substituted alkenes were achieved in good to excellent yields from various aryl bromides and alkenes with the catalyst TON of up to 10,000.

  4. Effects of elevated temperature postharvest on color aspect, physiochemical characteristics, and aroma components of pineapple fruits.

    Science.gov (United States)

    Liu, Chuanhe; Liu, Yan

    2014-12-01

    In this work, 2 separate experiments were performed to describe the influence of elevated temperature treatments postharvest on the color, physiochemical characteristics and aroma components of pineapple fruits during low-temperature seasons. The L* (lightness) values of the skin and pulp of pineapple fruits were decreased. The a* (greenness-redness) and b* (blueness-yellowness) values of the skin and pulp were all markedly increased. The elevated temperature significantly increased the contents of total soluble solids (TSS) and slightly affected contents of vitamin C (nonsignificant). Titratable acidity (TA) of pineapple fruits were notably decreased, whereas the values of TSS/TA of pineapple fruits were significantly increased. The firmness of the pineapple fruits decreased and more esters and alkenes were identified. The total relative contents of esters were increased, and the total relative contents of alkenes were decreased. © 2014 Institute of Food Technologists®

  5. Kinetic studies of 2-(2'-Haloethyl) and 2-ethenyl substituted quinazolinone alkylating agents. Acid-catalyzed dehydrohalogenation and alkylation involving a quinazolinone prototropic tautomer.

    Science.gov (United States)

    Dempcy, R O; Skibo, E B

    1993-07-01

    The mechanism of halide elimination from 2-haloethyl-5,8-dihydroxyquinazolin-4(3H)-ones was studied in aqueous buffer by means of a pH-rate profile, buffer dilution studies, isotopic labeling, and kinetic isotope effects. From the results of these studies, it is apparent that a quinazolinone tautomer, arising from a prototropic shift of the C(l') proton to the N(1) position, is formed in the rate determining step of elimination. Monobasic phosphate acts as a bifunctional catalyst for the tautomerism. The halide then eliminates from the tautomer to afford the alkene derivative. Conversely, hydroxyethyl mercaptide adds to the alkene to afford the tautomer. The significance of these studies lies in the discovery of a prototropic tautomer of quinazolinone, which is reversibly formed in aqueous buffer under mild conditions, and in the discovery of alkylation chemistry useful in the design of quinazolinone-based enzyme inhibitors.

  6. Zeolites as Catalysts for Fuels Refining after Indirect Liquefaction Processes

    Directory of Open Access Journals (Sweden)

    Arno de Klerk

    2018-01-01

    Full Text Available The use of zeolite catalysts for the refining of products from methanol synthesis and Fisher–Tropsch synthesis was reviewed. The focus was on fuels refining processes and differences in the application to indirect liquefaction products was compared to petroleum, which is often a case of managing different molecules. Processes covered were skeletal isomerisation of n-butenes, hydroisomerisation of n-butane, aliphatic alkylation, alkene oligomerisation, methanol to hydrocarbons, ethanol and heavier alcohols to hydrocarbons, carbonyls to hydrocarbons, etherification of alkenes with alcohols, light naphtha hydroisomerisation, catalytic naphtha reforming, hydroisomerisation of distillate, hydrocracking and fluid catalytic cracking. The zeolite types that are already industrially used were pointed out, as well as zeolite types that have future promise for specific conversion processes.

  7. Activation and discovery of earth-abundant metal catalysts using sodium tert-butoxide.

    Science.gov (United States)

    Docherty, Jamie H; Peng, Jingying; Dominey, Andrew P; Thomas, Stephen P

    2017-06-01

    First-row, earth-abundant metals offer an inexpensive and sustainable alternative to precious-metal catalysts. As such, iron and cobalt catalysts have garnered interest as replacements for alkene and alkyne hydrofunctionalization reactions. However, these have required the use of air- and moisture-sensitive catalysts and reagents, limiting both adoption by the non-expert as well as applicability, particularly in industrial settings. Here, we report a simple method for the use of earth-abundant metal catalysts by general activation with sodium tert-butoxide. Using only robust air- and moisture-stable reagents and pre-catalysts, both known and, significantly, novel catalytic activities have been successfully achieved, covering hydrosilylation, hydroboration, hydrovinylation, hydrogenation and [2π+2π] alkene cycloaddition. This activation method allows for the easy use of earth-abundant metals, including iron, cobalt, nickel and manganese, and represents a generic platform for the discovery and application of non-precious metal catalysis.

  8. Radiation curable resistant coatings and their preparation

    International Nuclear Information System (INIS)

    Brack, K.

    1976-01-01

    A prepolymer containing unsaturated hydrocarbon groups is prepared and mixed on a roller mill with one or more acrylic ester monomers and various additives to make a coating formulation of a desired viscosity. In general, low viscosity formulations are used for overprint varnishes, on paper or foil, or with pigments, for certain types of printing inks. Higher viscosity formulations are used to apply thick films on panels, tiles, or other bodies. Thin films are cured to hardness by brief exposure to ultraviolet light. Thicker films require more energetic radiation such as plasma arc and electron beam radiation. The prepolymers particularly useful for making such radiation curable coatings are the reaction products of polyether polyols and bis- or polyisocyanates and hydroxy alkenes or acrylic (or methacrylic) hydroxy esters, and, likewise, reactive polyamides modified with dicarboxy alkenes, their anhydrides or esters. A small amount of wax incorporated in the coating formulations results in coatings with release characteristics similar to those of PTFE coatings. 10 claims

  9. Elusive silane-alane complex [Si-H⋅⋅⋅Al]: isolation, characterization, and multifaceted frustrated Lewis pair type catalysis.

    Science.gov (United States)

    Chen, Jiawei; Chen, Eugene Y-X

    2015-06-01

    The super acidity of the unsolvated Al(C6F5)3 enabled isolation of the elusive silane-alane complex [Si-H⋅⋅⋅Al], which was structurally characterized by spectroscopic and X-ray diffraction methods. The Janus-like nature of this adduct, coupled with strong silane activation, effects multifaceted frustrated-Lewis-pair-type catalysis. When compared with the silane-borane system, the silane-alane system offers unique features or clear advantages in the four types of catalytic transformations examined in this study, including: ligand redistribution of tertiary silanes into secondary and quaternary silanes, polymerization of conjugated polar alkenes, hydrosilylation of unactivated alkenes, and hydrodefluorination of fluoroalkanes. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Playing with the Soccer Ball-an Experimental Introduction to Fullerene Chemistry

    Science.gov (United States)

    Hildebrand, Achim; Hilgers, Uwe; Blume, Rudiger; Wiechoczek, Dagmar

    1996-11-01

    The "molecule of the year 1991", C60 buckminsterfullerene, has found its way to experimental chemistry courses in high schools and universities. For the first time a selection of simple experiments with C60 on high-school and university level are presented: the bromination with Winkler's solution, hydroxylation with an alkaline permanganate solution, cycloadditions of dichlorcarbene and cyclopentadiene and the formation of a molecular complex with o-dimethoxybenzene. They are easy to carry out due to the high reactivity of C60. The experiments demonstrate some chemical properties of this new form of carbon. C60 reacts like a giant alkene with electron acceptor properties. To stress this fact, one should compare C60 with other alkenes and aromatic compounds. The characteristic color change of the C60 solutions during the reactions make them easy to observe, even without spectroscopic methods.

  11. Functional screening of aldehyde decarbonylases for long-chain alkane production by Saccharomyces cerevisiae

    DEFF Research Database (Denmark)

    Kang, Min-Kyoung; Zhou, Yongjin J.; Buijs, Nicolaas A.

    2017-01-01

    performed functional screening to identify efficient ADs that can improve alkane production by S. cerevisiae. Results: A comparative study of ADs originated from a plant, insects, and cyanobacteria were conducted in S. cerevisiae. As a result, expression of aldehyde deformylating oxygenases (ADOs), which......Background: Low catalytic activities of pathway enzymes are often a limitation when using microbial based chemical production. Recent studies indicated that the enzyme activity of aldehyde decarbonylase (AD) is a critical bottleneck for alkane biosynthesis in Saccharomyces cerevisiae. We therefore...... are cyanobacterial ADs, from Synechococcus elongatus and Crocosphaera watsonii converted fatty aldehydes to corresponding Cn-1 alkanes and alkenes. The CwADO showed the highest alkane titer (0.13 mg/L/OD600) and the lowest fatty alcohol production (0.55 mg/L/OD600). However, no measurable alkanes and alkenes were...

  12. A three-membered ring approach to carbonyl olefination.

    Science.gov (United States)

    Niyomchon, Supaporn; Oppedisano, Alberto; Aillard, Paul; Maulide, Nuno

    2017-10-23

    The carbon-carbon double bond, with its diverse and multifaceted reactivity, occupies a prominent position in organic synthesis. Although a variety of simple alkenes are readily available, the mild and chemoselective introduction of a unit of unsaturation into a functionalized organic molecule remains an ongoing area of research, and the olefination of carbonyl compounds is a cornerstone of such approaches. Here we show the direct olefination of hydrazones via the intermediacy of three-membered ring species generated by addition of sulfoxonium ylides, departing from the general dogma of alkenes synthesis from carbonyls. Moreover, the mild reaction conditions and operational simplicity of the transformation render the methodology appealing from a practical point of view.

  13. Ligand-enabled ortho-C–H olefination of phenylacetic amides with unactivated alkenes† †Electronic supplementary information (ESI) available: Data for new compounds and experimental procedures. See DOI: 10.1039/c7sc04827k

    Science.gov (United States)

    Lu, Ming-Zhu; Chen, Xing-Rong; Xu, Hui

    2017-01-01

    Although chelation-assisted C–H olefination has been intensely investigated, Pd(ii)-catalyzed C–H olefination reactions are largely restricted to acrylates and styrenes. Here we report a quinoline-derived ligand that enables the Pd(ii)-catalyzed olefination of the C(sp2)–H bond with simple aliphatic alkenes using a weakly coordinating monodentate amide auxiliary. Oxygen is used as the terminal oxidant with catalytic copper as the co-oxidant. A variety of functional groups in the aliphatic alkenes are tolerated. Upon hydrogenation, the ortho-alkylated product can be accessed. The utility of this reaction is also demonstrated by the late-stage diversification of drug molecules. PMID:29675177

  14. The absolute structure of ptilosarcenone 2.5-hydrate, a diterpenoid briarane from the orange sea pen Ptilosarcus gurneyi (Gray

    Directory of Open Access Journals (Sweden)

    Elaine Tran

    2011-01-01

    Full Text Available In the title compound, C24H29ClO8·2.5H2O, which contains two organic molecules (A and B and five heavily disordered water molecules in the asymmetric unit, the γ-lactone ring and the cyclohexenone ring are both trans-fused to the central cyclodecene ring. The cyclehexenone ring features an α,β-unsaturated ketone with torsion angles between the conjugated carbonyl and alkene bonds of 0.6 (3 and 7.4 (4° for molecules A and B, respectively. The ptilosarcenone torsion angles between conjugated alkene bonds are 56.2 (5 and 55.4 (6° for A and B, respectively. In the crystal, the components are linked by O—H...O hydrogen bonds. The absolute configuration of ptilosarcenone was determined unambiguously and exhibits similar absolute stereochemistry to that found in the crystal structures of other octocoralline briaranes.

  15. Mechanistic investigations of the ethylene tetramerisation reaction.

    Science.gov (United States)

    Overett, Matthew J; Blann, Kevin; Bollmann, Annette; Dixon, John T; Haasbroek, Daleen; Killian, Esna; Maumela, Hulisani; McGuinness, David S; Morgan, David H

    2005-08-03

    The unprecedented selective tetramerisation of ethylene to 1-octene was recently reported. In the present study various mechanistic aspects of this novel transformation were investigated. The unusually high 1-octene selectivity in chromium-catalyzed ethylene tetramerisation reactions is caused by the unique extended metallacyclic mechanism in operation. Both 1-octene and higher 1-alkenes are formed by further ethylene insertion into a metallacycloheptane intermediate, whereas 1-hexene is formed by elimination from this species as in other reported trimerisation reactions. This is supported by deuterium labeling studies, analysis of the molar distribution of 1-alkene products, and identification of secondary co-oligomerization reaction products. In addition, the formation of two C6 cyclic products, methylenecyclopentane and methylcyclopentane, is discussed, and a bimetallic disproportionation mechanism to account for the available data is proposed.

  16. Gold (I)-Catalyzed Diastereo- and Enantioselective 1,3-Dipolar Cycloaddition and Mannich Reactions of Azlactones

    Science.gov (United States)

    Melhado, Asa D.; Amarante, Giovanni W.; Wang, Z. Jane; Luparia, Marco; Toste, F. Dean

    2011-01-01

    Azlactones participate in stereoselective reactions with electron-deficient alkenes and N-sulfonyl aldimines to give products of 1,3-dipolar cycloaddition and Mannich addition reactions respectively. Both of these reactions proceed with good to excellent diastereo- and enantioselectivity using a single class of gold-catalysts, namely C2-symmetric bis(phosphinegold(I) carboxylate)complexes. The development of the azlactone Mannich reaction to provide fully protected anti-α,β-diamino acid derivatives is described. 1,3-Dipolar cycloaddition reactions of several acyclic 1,2-disubstituted alkenes, and the chemistry of the resultant cycloadducts, are examined to probe the stereochemical course of this reaction. Reaction kinetics and tandem MS studies of both the cycloaddition and Mannich reactions are reported. These studies support a mechanism in which the gold complexes catalyze addition reactions through nucleophile activation rather than the more typical activation of the electrophilic reaction component. PMID:21341677

  17. Olefin-Stabilized Cobalt Nanoparticles for C=C, C=O, and C=N Hydrogenations.

    Science.gov (United States)

    Sandl, Sebastian; Schwarzhuber, Felix; Pöllath, Simon; Zweck, Josef; Jacobi von Wangelin, Axel

    2018-03-07

    The development of cobalt catalysts that combine easy accessibility and high selectivity constitutes a promising approach to the replacement of noble-metal catalysts in hydrogenation reactions. This report introduces a user-friendly protocol that avoids complex ligands, hazardous reductants, special reaction conditions, and the formation of highly unstable pre-catalysts. Reduction of CoBr 2 with LiEt 3 BH in the presence of alkenes led to the formation of hydrogenation catalysts that effected clean conversions of alkenes, carbonyls, imines, and heteroarenes at mild conditions (3 mol % cat., 2-10 bar H 2 , 20-80 °C). Poisoning studies and nanoparticle characterization by TEM, EDX, and DLS supported the notion of a heterotopic catalysis mechanism. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Alkylation of isobutane by ethylene: A thermodynamic study

    Energy Technology Data Exchange (ETDEWEB)

    Goupil, J.M.; Poirier, J.L.; Cornet, D. (Univ. of Caen (France). Lab. Catalyse et Spectrochimie)

    1994-03-01

    Alkylation of isobutane by ethylene produces mainly hexanes, but a variety of other compounds, alkanes or alkenes, may be formed by secondary reactions such as successive alkylations, isomerization, and ethylene polymerization. The equilibrium distribution of products is evaluated in the temperature range 280--680 K and at various initial compositions and pressures. Isomer groups are treated using Alberty's formulation. Calculations show that alkenes are thermodynamically unstable under usual reaction conditions. The equilibrium amounts of alkanes are such that C[sub 6] [much gt] C[sub 8] [much gt] C[sub 10] and heavy alkanes also appear unstable. The selective formation of particular isomers (dimethylbutanes, trimethylpentanes) is also integrated in the equilibrium equations. The calculated compositions (C[sub 6]:C[sub 8]:C[sub 10]) are compared with experimental data.

  19. Diastereoselective Au-Catalyzed Allene Cycloisomerizations to Highly Substituted Cyclopentenes.

    Science.gov (United States)

    Reeves, Ryan D; Phelps, Alicia M; Raimbach, William A T; Schomaker, Jennifer M

    2017-07-07

    Site- and regiocontrolled Au-catalyzed allene carbocyclizations furnish highly substituted cyclopentenes in >1:1 dr. Significant substitution on the substrate is tolerated, with potential to install five contiguous stereocenters after alkene functionalization. Major challenges include identifying a Au/Cu catalyst that controls both the relative rates of allene epimerization/cyclization and the facial selectivity in addition of a metal enolate to the allene. Experiments to achieve stereodivergent cyclizations and transform key cyclopentenes into useful synthetic building blocks are described.

  20. Phosphine Catalysis using Allenoates with pro-Nucleophiles or Arylidenes; Development of an Asymetric Phosphine Catalyst; and Allenes as π-Ligands in Copper-Mediated Cross-Coupling

    OpenAIRE

    Martin, Tioga Jarrett

    2014-01-01

    The unique characteristics of 1,2-dienes have proven to be a dynamic and ever growing field of study in organic chemistry. Allenes have been manipulated into a myriad of transformations, and have offered their unique characteristics to a number of fields of study. Chapter 1 discusses a phosphine catalyzed annulation between allenoates and alkenes to form cyclohexenes. In Chapter 2 the new phosphine catalyzed β'-Addition of a Pronucleophile to an allenoate is examined. Chapter 3 presents ...

  1. dichlorodiazene dioxides using levulinic acid under solvent-free ...

    Indian Academy of Sciences (India)

    Administrator

    The procedure involves addition of NOCl generated in situ by the reaction of AcOH–HCl. (3 :1) with amyl nitrite to alkenes and treating the α-chloronitroso compounds obtained as dimers with levulinic acid in presence of a few drops of 6N HCl, the latter being a three-step domino reaction, in which the first is dissociation of ...

  2. HBr-DMPU: The First Aprotic Organic Solution of Hydrogen Bromide.

    Science.gov (United States)

    Li, Zhou; Ebule, Rene; Kostyo, Jessica; Hammond, Gerald B; Xu, Bo

    2017-09-18

    HBr and DMPU (1,3-dimethyl-3,4,5,6-tetrahydro-2-pyrimidinone) form a room-temperature-stable complex that provides a mild, effective, and selective hydrobrominating reagent toward alkynes, alkenes, and allenes. HBr-DMPU could also replace other halogenating reagents in the halo-Prins reaction, ether cleavage, and deoxy-bromination reactions. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. An Evaluation of Peptide-Bond Isosteres

    OpenAIRE

    Choudhary, Amit; Raines, Ronald T.

    2011-01-01

    Peptide-bond isosteres can enable a deep interrogation of the structure and function of a peptide or protein by amplifying or attenuating particular chemical properties. In this minireview, the electronic, structural, and conformational attributes of four such isosteres—thioamides, esters, alkenes, and fluoroalkenes—are examined in detail. In particular, the ability of these isosteres to partake in noncovalent interactions is compared with that of the peptide bond. The consequential perturbat...

  4. Gas chromatographic study of the volatile products from co-pyrolysis of coal and polyethylene wastes.

    Science.gov (United States)

    Domínguez, A; Blanco, C G; Barriocanal, C; Alvarez, R; Díez, M A

    2001-05-18

    The aim of this study was to determine the volatile products distribution of co-processing of coal with two plastic wastes, low-density polyethylene from agriculture greenhouses and high-density polyethylene from domestic uses, in order to explain the observed decrease in coal fluidity caused by polyethylene waste addition. Polymeric materials, although they are not volatile themselves, may be analysed by gas chromatography through the use of pyrolysis experiments. In this way, a series of pyrolysis tests were performed at 400 and 500 degrees C in a Gray-King oven with each of the two plastic wastes, one high-volatile bituminous coal and blends made up of coal and plastic waste (9:1, w/w, ratio). The pyrolysis temperatures, 400 and 500 degrees C, were selected on the basis of the beginning and the end of the coal plastic stage. The organic products evolved from the oven were collected, dissolved in pyridine and analysed by capillary gas chromatography using a flame ionization detector. The analysis of the primary tars indicated that the amount of n-alkanes is always higher than that of n-alkenes and the formation of the alkenes is favoured by increasing the pyrolysis temperature. However, this effect may be influenced by the size of the hydrocarbon. Thus, the fraction C17-C31 showed a higher increase of n-alkenes/n-alkanes ratio than other fractions. On the other hand, the difference between the experimental and estimated values from tars produced from single components was positive for n-alkanes and n-alkenes, indicating that co-pyrolysis of the two materials enhanced the chemical reactivity during pyrolysis and produced a higher conversion than that from individual components.

  5. Build/Couple/Pair Strategy Combining the Petasis 3-Component Reaction with Ru-Catalyzed Ring-Closing Metathesis and Isomerization

    DEFF Research Database (Denmark)

    Ascic, Erhad; Le Quement, Sebastian Thordal; Ishøy, Mette

    2012-01-01

    A “build/couple/pair” pathway for the systematic synthesis of structurally diverse small molecules is presented. The Petasis 3-component reaction was used to synthesize anti-amino alcohols displaying pairwise reactive combinations of alkene moieties. Upon treatment with a ruthenium alkylidene-cat......-catalyst, these dienes selectively underwent ring-closing metathesis reactions to form 5- and 7-membered heterocycles and cyclic aminals via a tandem isomerization/N-alkyliminium cyclization sequence....

  6. Mise au point de réactions tandems catalytiques incluant une étape d'isomérisation pour la synthèse de molécules naturelles

    OpenAIRE

    Hémelaere , Rémy

    2013-01-01

    Some of the new challenges of modern synthetic chemistry are: atom economy, employment of catalytic processes, avoidance of toxic reactants and limitation of purification steps. A lot of work has been devoted to the development of tandem reactions. A new reactivity could be generated in a molecule thanks to an isomerisation (or migration) reaction of an alkene. This reaction often needs an hydride specie which comes from a transition metal catalyst. This PhD thesis is about the development of...

  7. Transformation of methylcyclohexane on an FCC catalyst

    Directory of Open Access Journals (Sweden)

    Rabeharitsara A.

    2003-01-01

    Full Text Available The transformation of methylcyclohexane at 723 K over on a USHY sample and on an FCC catalyst composed of 30% USHY and 70% matrix containing 25% Al2O3 was studied. With both samples, C2-C7 alkenes and alkanes, cyclopentane and methylcyclopentane (cracking products, dimethylcyclopentanes and ethylcyclopentane (isomers and aromatics appeared as primary products. The activity and selectivity of fresh samples as well as the influence of coke deposits on porosity and selectivity are discussed.

  8. Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

    Directory of Open Access Journals (Sweden)

    Carmen Moreno-Marrodan

    2017-04-01

    Full Text Available The catalytic partial hydrogenation of substituted alkynes to alkenes is a process of high importance in the manufacture of several market chemicals. The present paper shortly reviews the heterogeneous catalytic systems engineered for this reaction under continuous flow and in the liquid phase. The main contributions appeared in the literature from 1997 up to August 2016 are discussed in terms of reactor design. A comparison with batch and industrial processes is provided whenever possible.

  9. Use of Alkyl Ethers as Traceless Hydride Donors in Brønsted Acid-Catalyzed Intramolecular Hydrogen Atom Transfer.

    Science.gov (United States)

    Gandamana, Dhika Aditya; Wang, Bin; Tejo, Ciputra; Bolte, Benoit; Gagosz, Fabien; Chiba, Shunsuke

    2018-03-25

    A new protocol for the deoxygenation of alcohols and the hydrogenation of alkenes under Brønsted acid catalysis has been developed. The method is based on the use of a benzyl or an isopropyl ether as a traceless hydrogen atom donor and involves an intramolecular hydride transfer as a key step that can be achieved in regio- and stereoselective manners. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Kinetics and mechanisms of some atomic oxygen reactions

    Science.gov (United States)

    Cvetanovic, R. J.

    1987-01-01

    Mechanisms and kinetics of some reactions of the ground state of oxygen atoms, O(3P), are briefly summarized. Attention is given to reactions of oxygen atoms with several different types of organic and inorganic compounds such as alkanes, alkenes, alkynes, aromatics, and some oxygen, nitrogen, halogen and sulfur derivatives of these compounds. References to some recent compilations and critical evaluations of reaction rate constants are given.

  11. Allenyl esters as quenching agents for ruthenium olefin metathesis catalysts.

    Science.gov (United States)

    Roy, Animesh; Silvestri, Maximilian A; Hall, Robert A; Lepore, Salvatore D

    2017-01-04

    In the attempt to synthesize substituted allenyl esters through a metathesis coupling of unsubstituted allenyl esters and alkenes using a variety of ruthenium catalysts, it was discovered that allenyl esters themselves cleanly arrested the activity of the catalysts. Further studies suggests possible utility of allene esters as general quenching agents for metathesis reactions. To explore this idea, several representative olefin metathesis reactions, including ring closing, were successfully terminated by the addition of simple allenyl esters for more convenient purification.

  12. Loss and Reformation of Ruthenium Alkylidene: Connecting Olefin Metathesis, Catalyst Deactivation, Regeneration, and Isomerization.

    Science.gov (United States)

    Engel, Julien; Smit, Wietse; Foscato, Marco; Occhipinti, Giovanni; Törnroos, Karl W; Jensen, Vidar R

    2017-11-22

    Ruthenium-based olefin metathesis catalysts are used in laboratory-scale organic synthesis across chemistry, largely thanks to their ease of handling and functional group tolerance. In spite of this robustness, these catalysts readily decompose, via little-understood pathways, to species that promote double-bond migration (isomerization) in both the 1-alkene reagents and the internal-alkene products. We have studied, using density functional theory (DFT), the reactivity of the Hoveyda-Grubbs second-generation catalyst 2 with allylbenzene, and discovered a facile new decomposition pathway. In this pathway, the alkylidene ligand is lost, via ring expansion of the metallacyclobutane intermediate, leading to the spin-triplet 12-electron complex (SIMes)RuCl 2 ( 3 R21, SIMes = 1,3-bis(2,4,6-trimethylphenyl)-4,5-dihydroimidazol-2-ylidene). DFT calculations predict 3 R21 to be a very active alkene isomerization initiator, either operating as a catalyst itself, via a η 3 -allyl mechanism, or, after spin inversion to give R21 and formation of a cyclometalated Ru-hydride complex, via a hydride mechanism. The calculations also suggest that the alkylidene-free ruthenium complexes may regenerate alkylidene via dinuclear ruthenium activation of alkene. The predicted capacity to initiate isomerization is confirmed in catalytic tests using p-cymene-stabilized R21 (5), which promotes isomerization in particular under conditions favoring dissociation of p-cymene and disfavoring formation of aggregates of 5. The same qualitative trends in the relative metathesis and isomerization selectivities are observed in identical tests of 2, indicating that 5 and 2 share the same catalytic cycles for both metathesis and isomerization, consistent with the calculated reaction network covering metathesis, alkylidene loss, isomerization, and alkylidene regeneration.

  13. Nitro-Grela-type complexes containing iodides - robust and selective catalysts for olefin metathesis under challenging conditions.

    Science.gov (United States)

    Tracz, Andrzej; Matczak, Mateusz; Urbaniak, Katarzyna; Skowerski, Krzysztof

    2015-01-01

    Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM) and cross metathesis (CM) reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities.

  14. Strategy for O-Alkylation of Serine and Threonine from Serinyl and Threoninyl Acetic Acids by Photoinduced Decarboxylative Radical Reactions: Connection between Serine/Threonine and Carbohydrates/Amino Acids at the Side Chain.

    Science.gov (United States)

    Yamamoto, Takashi; Iwasaki, Tomoya; Morita, Toshio; Yoshimi, Yasuharu

    2018-04-06

    O-Alkylations of serine and threonine derivatives at the hydroxy group were achieved using photoinduced decarboxylative radical reactions of serinyl and threoninyl acetic acids with an organic photocatalyst without racemization under mild conditions. Photoinduced decarboxylative radical additions of serinyl and threoninyl acetic acids to electron-deficient alkenes provided linked serine and threonine with carbohydrates and amino acids at the side chain. In addition, O-methylations containing deuterium and O-benzylation of serine were performed under similar photochemical conditions.

  15. Special Topic 2D: Reduction & Organometallic

    OpenAIRE

    Christiansen, Mike A

    2012-01-01

    The purpose of this video is to help second-year organic chemistry students review the concepts and questions that most frequently appear on standardized entrance exams, like the MCAT, DAT, PCAT, and GRE. In this video I'll review the following reduction reactions: hydrogenations of alkenes and alkynes, reductive amination, and Clemmensen and Wolff-Kishner reductions. I'll also teach you the following organometallic reactions: Grignard reactions; hydride (sodium borohydride, lithium aluminum ...

  16. Modelling a process for dimerisation of 2-methylpropene

    OpenAIRE

    Ouni, Tuomas

    2005-01-01

    Isooctane can be used to replace methyl-tert-butyl ether (MTBE) as a fuel additive. Isooctane is hydrogenated from isooctene, which is produced by dimerizing 2-methylpropene. In dimerization, two 2-methylpropene molecules react on ion-exchange resin catalyst to produce isooctene isomers (2,4,4-trimethyl-1-pentene, 2,4,4-trimethyl-2-pentene). Presence of 2-methyl-2-propanol (TBA) improves reaction selectivity. Trimers and tetramers are formed as side products. Water and alkenes have reaction e...

  17. Organic chemistry

    International Nuclear Information System (INIS)

    2003-08-01

    This book with sixteen chapter explains organic chemistry on linkage isomerism such as alkane, cycloalkane, alkene, aromatic compounds, stereo selective isomerization, aromatic compounds, stereo selective isomerization, organic compounds, stereo selective isomerization, organic halogen compound, alcohol, ether, aldehyde and ketone, carboxylic acid, dicarboxylic acid, fat and detergent, amino, carbohydrate, amino acid and protein, nucleotide and nucleic acid and spectroscopy, a polymer and medical chemistry. Each chapter has introduction structure and characteristic and using of organic chemistry.

  18. Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes

    Science.gov (United States)

    Moreno-Marrodan, Carmen; Liguori, Francesca

    2017-01-01

    The catalytic partial hydrogenation of substituted alkynes to alkenes is a process of high importance in the manufacture of several market chemicals. The present paper shortly reviews the heterogeneous catalytic systems engineered for this reaction under continuous flow and in the liquid phase. The main contributions appeared in the literature from 1997 up to August 2016 are discussed in terms of reactor design. A comparison with batch and industrial processes is provided whenever possible. PMID:28503209

  19. Manganese-Mediated Coupling Reaction of Vinylarenes and Aliphatic Alcohols

    Science.gov (United States)

    Zhang, Wei; Wang, Nai-Xing; Bai, Cui-Bing; Wang, Yan-Jing; Lan, Xing-Wang; Xing, Yalan; Li, Yi-He; Wen, Jia-Long

    2015-10-01

    Alcohols and alkenes are the most abundant and commonly used organic building blocks in the large-scale chemical synthesis. Herein, this is the first time to report a novel and operationally simple coupling reaction of vinylarenes and aliphatic alcohols catalyzed by manganese in the presence of TBHP (tert-butyl hydroperoxide). This coupling reaction provides the oxyalkylated products of vinylarenes with good regioselectivity and accomplishes with the principles of step-economies. A possible reaction mechanism has also been proposed.

  20. Gordon Research Conference in Organometallic Chemistry, held August 16-20, 1982 Andover, New Hampshire.

    Science.gov (United States)

    1983-03-01

    34Heterometallacycles and a-Hydrogen Elimination in Catalytic Alkene Oxidation by Transition Metal Nitro and Related Complexes." 2. Thomas B. Brill and Shayne J...Occidental Research Corporation, " Amphoteric Ligands: Facile Migrations in Alkyl- and Hydridometal Carbonyl Complexes." 19. Mary Therese Zoeckler and...Thomas E. Cole and Clifford P. Kubiak, Purdue University, "CO/3 Fuel Cells: Catalysis of CO Oxidation at Electrode/Electrolyte Inter~aces." I

  1. Nitro-Grela-type complexes containing iodides – robust and selective catalysts for olefin metathesis under challenging conditions

    Directory of Open Access Journals (Sweden)

    Andrzej Tracz

    2015-10-01

    Full Text Available Iodide-containing nitro-Grela-type catalysts have been synthesized and applied to ring closing metathesis (RCM and cross metathesis (CM reactions. These new catalysts have exhibited improved efficiency in the transformation of sterically, non-demanding alkenes. Additional steric hindrance in the vicinity of ruthenium related to the presence of iodides ensures enhanced catalyst stability. The benefits are most apparent under challenging conditions, such as very low reaction concentrations, protic solvents or with the occurrence of impurities.

  2. (2E-3-Phenylprop-2-en-1-yl thiocyanate

    Directory of Open Access Journals (Sweden)

    Ezzat Khan

    2017-04-01

    Full Text Available In the title compound, C10H9NS, the C—S—C bond angle is 99.41 (9° and the dihedral angle between the trans-alkene fragment and the benzene ring is 16.49 (19°. In the crystal, inversion dimers linked by pairs of extremely weak C—H...N interactions occur, as does a short S...N contact [3.2258 (19 Å].

  3. Comparison of the catalytic activity of MOFs and zeolites in Knoevenagel condensation

    Czech Academy of Sciences Publication Activity Database

    Opanasenko, Maksym; Dhakshinamoorthy, A.; Shamzhy, Mariya; Nachtigall, P.; Horáček, Michal; Garcia, H.; Čejka, Jiří

    2013-01-01

    Roč. 3, č. 2 (2013), s. 500-507 ISSN 2044-4753 R&D Projects: GA ČR GBP106/12/G015 Grant - others:European Commission(XE) FP7/2007-2013, contract 228862 Institutional support: RVO:61388955 Keywords : SOLVENT-FREE CONDITIONS * METAL-ORGANIC FRAMEWORKS * ELECTROPHILIC ALKENES Subject RIV: CF - Physical ; Theoretical Chemistry Impact factor: 4.760, year: 2013

  4. Mechanism of Oxygen Atom Transfer from Fe(V)(O) to Olefins at Room Temperature.

    Science.gov (United States)

    Singh, Kundan K; Tiwari, Mrityunjay K; Dhar, Basab B; Vanka, Kumar; Sen Gupta, Sayam

    2015-07-06

    In biological oxidations, the intermediate Fe(V)(O)(OH) has been proposed to be the active species for catalyzing the epoxidation of alkenes by nonheme iron complexes. However, no study has been reported yet that elucidates the mechanism of direct O-atom transfer during the reaction of Fe(V)(O) with alkenes to form the corresponding epoxide. For the first time, we study the mechanism of O-atom transfer to alkenes using the Fe(V)(O) complex of biuret-modified Fe-TAML at room temperature. The second-order rate constant (k2) for the reaction of different alkenes with Fe(V)(O) was determined under single-turnover conditions. An 8000-fold rate difference was found between electron-rich (4-methoxystyrene; k2 = 216 M(-1) s(-1)) and electron-deficient (methyl trans-cinnamate; k2 = 0.03 M(-1) s(-1)) substrates. This rate difference indicates the electrophilic character of Fe(V)(O). The use of cis-stilbene as a mechanistic probe leads to the formation of both cis- and trans-stilbene epoxides (73:27). This suggests the formation of a radical intermediate, which would allow C-C bond rotation to yield both stereoisomers of stilbene-epoxide. Additionally, a Hammett ρ value of -0.56 was obtained for the para-substituted styrene derivatives. Detailed DFT calculations show that the reaction proceeds via a two-step process through a doublet spin surface. Finally, using biuret-modified Fe-TAML as the catalyst and NaOCl as the oxidant under catalytic conditions epoxide was formed with modest yields and turnover numbers.

  5. Rh(III) -Catalyzed C-H Olefination of Benzoic Acids under Mild Conditions using Oxygen as the Sole Oxidant.

    Science.gov (United States)

    Jiang, Quandi; Zhu, Changlei; Zhao, Huaiqing; Su, Weiping

    2016-02-04

    Phthalide skeletons have been synthesized for the first time through a Rh(III) -catalyzed C-H olefination of benzoic acids under mild conditions using oxygen as the sole oxidant. Aromatic acids bearing a variety of functional groups could react with diverse alkenes to afford the desired cyclized lactones or uncyclized alkenylarenes in moderate-to-excellent yields. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Total syntheses of (-)-haemanthidine, (+)-pretazettine, and (+)-tazettine.

    Science.gov (United States)

    Baldwin, S W; Debenham, J S

    2000-01-27

    [structures: see text] The total syntheses of the amaryllidaceae alkaloids haemanthidine, pretazettine, and tazettine as optically pure enantiomers are reported. Using D-mannose as the starting material, the critical relative stereochemical relationships are established with an intramolecular nitrone-alkene cycloaddition reaction. The synthetic route leads successively to (-)-haemanthidine and then to (+)-pretazettine and (+)-tazettine, taking advantage of the well-established complex relationships among these three alkaloids.

  7. Exposure of bus and taxi drivers to urban air pollutants as measured by DNA and protein adducts

    DEFF Research Database (Denmark)

    Hemminki, K.; Zhang, L.F.; Krüger, J.

    1994-01-01

    Urinary 1-hydroxypyrene, lymphocyte DNA adducts, serum protein-bound PAH and hemoglobin-bound alkene adducts were analysed from 4 groups of non-smoking men: urban and suburban bus drivers, taxi drivers and suburban controls. The only differences between the groups were in DNA adducts between...... suburban bus drivers and controls, and in DNA adduct and plasma protein PAH-adducts between taxi drivers and controls....

  8. Synthesis of alpha,beta-unsaturated 4,5-disubstituted gamma-lactones via ring-closing metathesis catalyzed by the first-generation Grubbs' catalyst.

    Science.gov (United States)

    Bassetti, Mauro; D'Annibale, Andrea; Fanfoni, Alessia; Minissi, Franco

    2005-04-28

    [reaction: see text] 4-Methyl-5-alkyl-2(5H)-furanones have been prepared by ruthenium-catalyzed ring-closing metathesis of the suitable methallyl acrylates. Despite the electron deficiency of the conjugated double bond and of the gem-disubstitution of the allylic alkene moiety in the starting acrylates, the first-generation Grubbs' catalyst I proved to be an effective promoter for the ring closure, affording the expected butenolides in good to high yields.

  9. Asymmetric conjugate addition of alkylzirconium reagents to α,β-unsaturated lactones.

    Science.gov (United States)

    Maciver, Eleanor E; Maksymowicz, Rebecca M; Wilkinson, Nancy; Roth, Philippe M C; Fletcher, Stephen P

    2014-06-20

    The asymmetric synthesis of β-substituted lactones by catalytic asymmetric conjugate addition of alkyl groups to α,β-unsaturated lactones is reported. The method uses alkylzirconium nucleophiles prepared in situ from alkenes and the Schwartz reagent. Enantioselective additions to 6- and 7-membered lactones proceed at rt, tolerate a wide variety of functional groups, and are readily scalable. The method was used in a formal asymmetric synthesis of mitsugashiwalactone.

  10. Kinetic resolution of hindered Morita-Baylis-Hillman adducts by Rh(I)-catalyzed asymmetric 1,4-addition/β-hydroxyelimination.

    Science.gov (United States)

    Wang, Yazhou; Feng, Xiangqing; Du, Haifeng

    2011-09-16

    A kinetic resolution of hindered Morita-Baylis-Hillman adducts has been successfully achieved in excellent selectivities via Rh(I)-catalyzed asymmetric 1,4-addition/β-hydroxyelimination with the use of a chiral sulfinamide/olefin hybrid ligand. This study provides a novel and efficient access to both optically active hindered highly functionalized alkenes and Morita-Baylis-Hillman adducts. © 2011 American Chemical Society

  11. Study of Plasma Chemistry and Plasma Processing.

    Science.gov (United States)

    1983-01-01

    ethanol , chloroform, carbon L I 111.4.29 tetrachloride, water and methanol. No color change was observed at any point and the PPVF film was not...34EC Catalysis of Ascorbic Acid Oxidation Using Plasma Polymerized Vinylferrocene Film Electrodes", J. Electroanal. Chem., 109, 301 (1980). 7...photolyzed at 254 ntm in the gas phase in the presence of 15-20 torf of certain alkenes or aromatics. The products were analyzed by GC-MS. Ethene gave

  12. The Reactivity of Stable Metallacyclobutenes and Vinylcarbenes

    OpenAIRE

    Holland, Ryan Lynn

    2016-01-01

    Chapter 1. Historical Development of Stable Metallacyclobutenes Fred Tebbe and co-workers synthesized the first stable metallacyclobutene complexes in the late 1970’s by treatment of an intermediate titanium methylene species – later popularized as the “Tebbe reagent” – with acetylenes. Robert Grubbs at Caltech further studied this system, using it to detail a degenerate metathesis reaction and to isolate a metallacyclobutane complex – which was implicated in the emerging field of alkene meta...

  13. Oxidation of Group 8 transition-Metal Hydrides and Ionic Hydrogenation of Ketones and Aldehydes

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Kjell-Tore

    1996-08-01

    Transition-metal hydrides have received considerable attention during the last decades because of their unusual reactivity and their potential as homogeneous catalysts for hydrogenation and other reactions of organic substrates. An important class of catalytic processes where transition-metal hydrides are involved is the homogeneous hydrogenation of alkenes, alkynes, ketones, aldehydes, arenes and nitro compounds. This thesis studies the oxidation of Group 8 transition-metal hydrides and the ionic hydrogenation of ketones and aldehydes.

  14. The use of ultrasmall iron(0) nanoparticles as catalysts for the selective hydrogenation of unsaturated C-C bonds.

    Science.gov (United States)

    Kelsen, Vinciane; Wendt, Bianca; Werkmeister, Svenja; Junge, Kathrin; Beller, Matthias; Chaudret, Bruno

    2013-04-28

    The performance of well-defined ultrasmall iron(0) nanoparticles (NPs) as catalysts for the selective hydrogenation of unsaturated C-C and C=X bonds is reported. Monodisperse iron nanoparticles of about 2 nm size are synthesized by the decomposition of {Fe(N[Si(CH3)3]2)2}2 under dihydrogen. They are found to be active for the hydrogenation of various alkenes and alkynes under mild conditions and weakly active for C=O bond hydrogenation.

  15. Formation of gas-phase peroxides in a rural atmosphere: An interpretation of the recent SOS/SERON field results

    Energy Technology Data Exchange (ETDEWEB)

    Lee, J.H.; Tang, I.N. [Brookhaven National Lab., Upton, NY (United States); Weinstein-Lloyd, J.B. [State Univ. of New York, Old Westbury, NY (United States). Chemistry/Physics Dept.

    1993-09-01

    Hydrogen perioxide (H{sub 2}O{sub 2}) and certain organic peroxides such as hydroxymethyl-hydroperoxide (HMHP), are gas-phase oxidants present in the atmosphere at ppbv concentration levels. These oxidants play an important role in atmospheric chemistry. In addition, precipitation containing H{sub 2}O{sub 2} is toxic to trees, and it has also been suggested that organic peroxides formed presumably by ozone reactions with biogenic alkenes are responsible for leaf disorders. Recently, we have developed a nonenzymatic method or aqueous-phase H{sub 2}O{sub 2} measurement, using Fenton reagent and fluorescent hydroxy- benzoic acid. The new method, in conjunction with the well-known method of p-hydroxyphenylacetic acid and horseradish peroxidase for total peroxides, and together with an improved gas scrubber to mitigate sampling line problems, has been successfully deployed in recent SOS/SERON field measurements in rural Georgia. For the first time, continuously measured and speciated gas-phase peroxide data have become available, making it possible to examine some aspects of the ozone chemistry leading to the formation of these oxidants. It is observed that daily H{sub 2}O{sub 2} maximum frequently occurs at a different time than does HMHP, and that H{sub 2}O{sub 2} concentration, but not HMHP, tends to correlate with solar fluxes measured at the same location. These findings seem to indicate that the formation mechanisms for H{sub 2}O{sub 2} and organic peroxides are basically different. It is likely that H{sub 2}O{sub 2} is formed from radical-radical recombination, while HMHP is formed by ozone-alkene reactions. Since the gas-phase ozone-alkene reactions are usually too slow to account for the diurnal concentration variations observed for HMHP, heterogeneous processes involving ozone and alkenes are also a possibility.

  16. Synthesis of Aminolactones Using Capto-Dative Effect

    OpenAIRE

    Hatakeyama, Yuki; Nishino, Hiroshi; ハタケヤマ, ユキ; ニシノ, ヒロシ; 畠山, 由紀; 西野, 宏

    2011-01-01

    Manganese(III)-based oxidation of alkenes substituted both with an electron-withdrawing (captor) group and an electron-releasing (donor) group gave γ-lactones via radical intermediates stabilized by the capto-dative effect. 2-Aminoacrylate 3 underwent the lactonization to give 5-aminotetrahydro-2-furanone-5-carboxylate 4 in good yield. 2-Methoxyacrylate 7 also yielded the corresponding 5-methoxytetrahydro-2-furanone-5-carboxylate 8 in a similar yield. 2-Furancarboxylate 9 and pyrrolinecarboxy...

  17. The Use of Nitrone Cycloadditions in the Synthesis of Beta-Amino Aldehydes and Unsaturated Amines.

    Science.gov (United States)

    1986-01-01

    8217-’ OMe 25 26 Me - H NH 2 22 , **o.° 12 prepared by the Mannich reaction or one of its modern variants.’ s However, the Nannich reaction in efficient...product mixtures. The nitrone strategy is clearly advantagous to the Mannich reaction for the prepartion of these systems. More recent results from...with alkenes (dipolarophiles) to produce isoxazolidines (2) in a fashion similar to the (4+2] Diels-Alder reaction .’ The cycloaddition results in

  18. The development of a one-pot 1,4-addition/nitro-Mannich reaction

    OpenAIRE

    Mills, M. R.

    2010-01-01

    The introduction of this thesis reviews the three areas of importance to the research carried out. These are the nitro-Mannich reaction, the conjugate addition of nucleophiles to nitro-alkenes and the diastereoselectivity of electrophilic additions to substrates bearing an α-stereocentre. The Results and Discussion details the research carried out into the development of a one-pot 1,4-addition/nitro-Mannich reaction. Initially the research focused on triggering the reaction ...

  19. Photoredox-Catalyzed Ketyl–Olefin Coupling for the Synthesis of Substituted Chromanols

    KAUST Repository

    Fava, Eleonora

    2016-07-21

    A visible light photoredox-catalyzed aldehyde olefin cyclization is reported. The method represents a formal hydroacylation of alkenes and alkynes and provides chromanol derivatives in good yields. The protocol takes advantage of the double role played by trialkylamines (NR3) which act as (i) electron donors for reducing the catalyst and (ii) proton donors to activate the substrate via a proton-coupled electron transfer. © 2016 American Chemical Society.

  20. Well-defined single-site monohydride silica-supported zirconium from azazirconacyclopropane

    KAUST Repository

    Hamzaoui, Bilel

    2015-01-13

    The silica-supported azazirconacyclopropane ≡SiOZr(HNMe2)(η2-NMeCH2)(NMe2) (1) leads exclusively under hydrogenolysis conditions (H2, 150°C) to the single-site monopodal monohydride silica-supported zirconium species ≡SiOZr(HNMe2)(NMe2)2H (2). Reactivity studies by contacting compound 2 with ethylene, hydrogen/ethylene, propene, or hydrogen/propene, at a temperature of 200°C revealed alkene hydrogenation.