WorldWideScience

Sample records for catalyzed alkene-alkyne coupling

  1. Stereocontrolled Synthesis of Vinyl Boronates and Vinyl Silanes via Atom-Economical Ruthenium-Catalyzed Alkene-Alkyne Coupling.

    Science.gov (United States)

    Trost, Barry M; Koester, Dennis C; Herron, Alastair N

    2015-12-21

    The synthesis of vinyl boronates and vinyl silanes was achieved by employing a Ru-catalyzed alkene-alkyne coupling reaction of allyl boronates or allyl silanes with various alkynes. The double bond geometry in the generated vinyl boronates can be remotely controlled by the juxtaposing boron- and silicon groups on the alkyne substrate. The synthetic utility of the coupling products has been demonstrated in a variety of synthetic transformations, including iterative cross-coupling reactions, and a Chan-Lam-type allyloxylation followed by a Claisen rearrangement. A sequential one-pot alkene-alkyne-coupling/allylation-sequence with an aldehyde to deliver a highly complex α-silyl-β-hydroxy olefin with a handle for further functionalization was also realized. PMID:26572804

  2. Ru Catalyzed Alkene-Alkyne Coupling. Total Synthesis of Amphidinolide P

    OpenAIRE

    Trost, Barry M.; Papillon, Julien P. N.; Nussbaumer, Thomas

    2005-01-01

    A coordinatively unsaturated ruthenium complex catalyzed the formation of a carbon-carbon bond between two judiciously chosen alkene and alkyne partners in good yield, and in a chemo- and regioselective fashion, in spite of the significant degree of unsaturation of the substrates. The resulting 1,4-diene forms the backbone of the cytotoxic marine natural product amphidinolide P. The alkene partner was rapidly assembled from (R)-glycidyl tosylate, which served as a linchpin in a one-flask, seq...

  3. Evaluating Transition-Metal Catalyzed Transformations for the Synthesis of Laulimalide

    OpenAIRE

    Trost, Barry M.; Amans, Dominique; Seganish, W. Michael; Chung, Cheol K.

    2009-01-01

    Laulimalide is a structurally unique 20-membered marine macrolide displaying microtubule stabilizing activity similar to that of paclitaxel and the epothilones. The use of atom economical transformations such as a rhodium-catalyzed cycloisomerization to form the endocyclic dihydropyran, a dinuclear zinc-catalyzed asymmetric glycolate aldol to prepare the syn 1,2-diol and an intramolecular ruthenium-catalyzed alkene-alkyne coupling to build the macrocycle enabled us to synthesize laulimalide v...

  4. Switching the regioselectivity in the copper-catalyzed synthesis of iodoimidazo[1,2-a]pyridines.

    Science.gov (United States)

    Samanta, Sadhanendu; Jana, Sourav; Mondal, Susmita; Monir, Kamarul; Chandra, Swapan K; Hajra, Alakananda

    2016-06-14

    A unique copper-catalyzed binucleophilic switching of 2-aminopyridine has been developed for the regioselective synthesis of 2- and 3-iodoimidazo[1,2-a]pyridines using alkenes/alkynes as coupling partners in the presence of molecular iodine under aerobic reaction conditions. This method was also applied to the synthesis of 2-iodo-3-phenylbenzo[d]imidazo[2,1-b]thiazoles. This protocol offers an easy route towards the synthesis of 2,3-diarylimidazo[1,2-a]pyridines. PMID:27182027

  5. Pinacol Coupling Reactions Catalyzed by Active Zinc

    Institute of Scientific and Technical Information of China (English)

    Hui ZHAO; Wei DENG; Qing Xiang GUO

    2005-01-01

    Pinacol coupling reactions catalyzed by active zinc revealed high activity and extensive suitability. The efficiency of the reaction was improved apparently owing to decreasing reductive potential of zinc. In addition, the results indicated that the zinc activity has a direct relation to the coupling reactivity compared to untreated zinc or other general active zinc.

  6. Palladium-catalyzed coupling reactions

    CERN Document Server

    Molnár, Árpád

    2013-01-01

    This handbook and ready reference brings together all significant issues of practical importance for interested readers in one single volume. While covering homogeneous and heterogeneous catalysis, the text is unique in focusing on such important aspects as using different reaction media, microwave techniques or catalyst recycling. It also provides a comprehensive treatment of modern-day coupling reactions and emphasizes those topics that show potential for future development, such as continuous flow systems, water as a reaction medium, and catalyst immobilization, among others. With i

  7. Palladium(II)-Catalyzed Coupling Reactions

    OpenAIRE

    Lindh, Jonas

    2010-01-01

    Sustainable chemical processes are becoming increasingly important in all fields of synthetic chemistry. Catalysis can play an important role in developing environmentally benign chemical processes, and transition metals have an important role to play in the area of green chemistry. In particular, palladium(II) catalysis includes many key features for successful green chemistry methods, as demonstrated by a number of eco-friendly oxidation reactions catalyzed by palladium(II). The aim of the ...

  8. Recent advances in copper-catalyzed asymmetric coupling reactions

    Directory of Open Access Journals (Sweden)

    Fengtao Zhou

    2015-12-01

    Full Text Available Copper-catalyzed (or -mediated asymmetric coupling reactions have received significant attention over the past few years. Especially the coupling reactions of aryl or alkyl halides with nucleophiles became a very powerful tool for the formation of C–C, C–N, C–O and other carbon–heteroatom bonds as well as for the construction of heteroatom-containing ring systems. This review summarizes the recent progress in copper-catalyzed asymmetric coupling reactions for the formation of C–C and carbon–heteroatom bonds.

  9. Recent advances in copper-catalyzed asymmetric coupling reactions

    Science.gov (United States)

    2015-01-01

    Summary Copper-catalyzed (or -mediated) asymmetric coupling reactions have received significant attention over the past few years. Especially the coupling reactions of aryl or alkyl halides with nucleophiles became a very powerful tool for the formation of C–C, C–N, C–O and other carbon–heteroatom bonds as well as for the construction of heteroatom-containing ring systems. This review summarizes the recent progress in copper-catalyzed asymmetric coupling reactions for the formation of C–C and carbon–heteroatom bonds. PMID:26734106

  10. Oxo-rhenium catalyzed reductive coupling and deoxygenation of alcohols.

    Science.gov (United States)

    Kasner, Gabrielle R; Boucher-Jacobs, Camille; Michael McClain, J; Nicholas, Kenneth M

    2016-06-01

    Representative benzylic, allylic and α-keto alcohols are deoxygenated to alkanes and/or reductively coupled to alkane dimers by reaction with PPh3 catalyzed by (PPh3)2ReIO2 (1). The newly discovered catalytic reductive coupling reaction is a rare C-C bond-forming transformation of alcohols. PMID:27174412

  11. Transition-metal-catalyzed C-S bond coupling reaction.

    Science.gov (United States)

    Lee, Chin-Fa; Liu, Yi-Chen; Badsara, Satpal Singh

    2014-03-01

    Sulfur-containing molecules such as thioethers are commonly found in chemical biology, organic synthesis, and materials chemistry. While many reliable methods have been developed for preparing these compounds, harsh reaction conditions are usually required in the traditional methods. The transition metals have been applied in this field, and the palladium-catalyzed coupling of thiols with aryl halides and pseudo halides is one of the most important methods in the synthesis of thioethers. Other metals have also been used for the same purpose. Here, we summarize recent efforts in metal-catalyzed C-S bond cross-coupling reactions, focusing especially on the coupling of thiols with aryl- and vinyl halides based on different metals. PMID:24443103

  12. Synthesis of Aryldifluoroamides by Copper-Catalyzed Cross-Coupling.

    Science.gov (United States)

    Arlow, Sophie I; Hartwig, John F

    2016-03-24

    A copper-catalyzed coupling of aryl, heteroaryl, and vinyl iodides with α-silyldifluoroamides is reported. The reaction forms α,α-difluoro-α-aryl amides from electron-rich, electron-poor, and sterically hindered aryl iodides in high yield and tolerates a variety of functional groups. The aryldifluoroamide products can be transformed further to provide access to a diverse array of difluoroalkylarenes, including compounds of potential biological interest. PMID:26929068

  13. Palladium-catalyzed coupling reactions of tetrafluoroethylene with arylzinc compounds.

    Science.gov (United States)

    Ohashi, Masato; Kambara, Tadashi; Hatanaka, Tsubasa; Saijo, Hiroki; Doi, Ryohei; Ogoshi, Sensuke

    2011-03-16

    Organofluorine compounds are widely used in all aspects of the chemical industry. Although tetrafluoroethylene (TFE) is an example of an economical bulk organofluorine feedstock, the use of TFE is mostly limited to the production of poly(tetrafluoroethylene) and copolymers with other alkenes. Furthermore, no catalytic transformation of TFE that involves carbon-fluorine bond activation has been reported to date. We herein report the first example of a palladium-catalyzed coupling reaction of TFE with arylzinc reagents in the presence of lithium iodide, giving α,β,β-trifluorostyrene derivatives in excellent yields. PMID:21322557

  14. Magical Power of d-block transition metals. Pd-Catalyzed Cross-Coupling and Zr-Catalyzed Asymmetric Carboalumination (Zaca reaction)

    OpenAIRE

    Año Internacional de la Quimica 2011

    2011-01-01

    Magical Porwer of d-block Transition Metals. Pd-Catalyzed Cross-Coupling and Zr-Catalyzed Asymmetric Carboalumination (Zaca Reaction). Ei-ichi Negishi (Department of Chemistry - Purdue University). Premio Nobel de Química 2010

  15. Palladium-catalyzed Cascade Cyclization-Coupling Reaction of Benzyl Halides with N,N-Diallylbenzoylamide

    Institute of Scientific and Technical Information of China (English)

    Yi Min HU; Yu ZHANG; Jian Lin HAN; Cheng Jian ZHU; Yi PAN

    2003-01-01

    A novel type of palladium-catalyzed cascade cyclization-coupling reaction has been found. Reaction of N, N-diallylbenzoylamide 1 with benzyl halides 2 afforded the corresponding dihydropyrroles 3 in moderate to excellent yields.

  16. Pd/C catalyzed Suzuki-Miyaura cross coupling reaction: Is it heterogeneous or homogeneous?

    Science.gov (United States)

    Hoang, Tony Phuc

    The Suzuki-Miyaura cross-coupling reaction is a popular industrial method of creating covalent bonds between two carbons. This reaction can be catalyzed by a myriad of palladium catalyst including heterogeneous and homogeneous. The objective of this research is to study whether the Suzuki cross coupling reaction catalyzed by solid supported palladium catalysts is truly heterogeneous in nature (i.e. does the reaction occurs on the surface of the catalyst or does palladium leach from the solid support and catalyze the reaction in a homogenous manner).

  17. Iron-Catalyzed C-C Cross-Couplings Using Organometallics.

    Science.gov (United States)

    Guérinot, Amandine; Cossy, Janine

    2016-08-01

    Over the last decades, iron-catalyzed cross-couplings have emerged as an important tool for the formation of C-C bonds. A wide variety of alkenyl, aryl, and alkyl (pseudo)halides have been coupled to organometallic reagents, the most currently used being Grignard reagents. Particular attention has been devoted to the development of iron catalysts for the functionalization of alkyl halides that are generally challenging substrates in classical cross-couplings. The high functional group tolerance of iron-catalyzed cross-couplings has encouraged organic chemists to use them in the synthesis of bioactive compounds. Even if some points remain obscure, numerous studies have been carried out to investigate the mechanism of iron-catalyzed cross-coupling and several hypotheses have been proposed. PMID:27573401

  18. Palladium-catalyzed Coupling between Aryl Halides and Trimethylsilylacetylene Assisted by Dimethylaminotrimethyltin

    Institute of Scientific and Technical Information of China (English)

    Cai Liangzhen; Yang Dujuan; Sun Zhonghua; Tao Xiaochun; Cai Lisheng; Pike Victor W

    2011-01-01

    Palladium-catalyzed coupling between aryl halides, especially less reactive ones or N-heteroaryls, and trimethylsilylacetylene in the presence of dimethylaminotrimethyltin generated the coupled products in high yields. The reaction does not need CuI and base as auxiliary agents.

  19. Iron-catalyzed coupling reactions of vinylic chalcogenides with Grignard reagents

    International Nuclear Information System (INIS)

    A general new method for the cross-coupling reaction between vinylic selenides and tellurides and Grignard reagents catalyzed by Fe(acac)3 at room temperature is described. This reaction proceeded with retention of configuration, providing the respective alkenes in good to excellent yields. This method is also efficient for the coupling reaction of divinyl chalcogenides with Grignard reagents. (author)

  20. Iron-catalyzed coupling reactions of vinylic chalcogenides with Grignard reagents

    Energy Technology Data Exchange (ETDEWEB)

    Silveira, Claudio C.; Mendes, Samuel R.; Wolf, Lucas, E-mail: silveira@quimica.ufsm.b [Universidade Federal de Santa Maria (UFSM), RS (Brazil). Centro de Tecnologia. Dept. de Quimica

    2010-07-01

    A general new method for the cross-coupling reaction between vinylic selenides and tellurides and Grignard reagents catalyzed by Fe(acac){sub 3} at room temperature is described. This reaction proceeded with retention of configuration, providing the respective alkenes in good to excellent yields. This method is also efficient for the coupling reaction of divinyl chalcogenides with Grignard reagents. (author)

  1. Fe-Catalyzed Cross-Dehydrogenative Coupling Reactions.

    Science.gov (United States)

    Lv, Leiyang; Li, Zhiping

    2016-08-01

    Cross-dehydrogenative coupling (CDC), which enables the formation of carbon-carbon (C-C) and C-heteroatom bonds from the direct coupling of two C-H bonds or C-H/X-H bonds, represents a new state of the art in the field of organic chemistry. Iron, a prominent metal, has already shown its versatile application in chemical synthesis. This review attempts to provide a comprehensive understanding of the evolution of cross-dehydrogenative coupling via iron catalysis, as well as its application in synthetic chemistry. PMID:27573390

  2. Palladium-Catalyzed Cross-Coupling Reactions of Perfluoro Organic Compounds

    Directory of Open Access Journals (Sweden)

    Masato Ohashi

    2014-09-01

    Full Text Available In this review, we summarize our recent development of palladium(0-catalyzed cross-coupling reactions of perfluoro organic compounds with organometallic reagents. The oxidative addition of a C–F bond of tetrafluoroethylene (TFE to palladium(0 was promoted by the addition of lithium iodide, affording a trifluorovinyl palladium(II iodide. Based on this finding, the first palladium-catalyzed cross-coupling reaction of TFE with diarylzinc was developed in the presence of lithium iodide, affording α,β,β-trifluorostyrene derivatives in excellent yield. This coupling reaction was expanded to the novel Pd(0/PR3-catalyzed cross-coupling reaction of TFE with arylboronates. In this reaction, the trifluorovinyl palladium(II fluoride was a key reaction intermediate that required neither an extraneous base to enhance the reactivity of organoboronates nor a Lewis acid additive to promote the oxidative addition of a C–F bond. In addition, our strategy utilizing the synergetic effect of Pd(0 and lithium iodide could be applied to the C–F bond cleavage of unreactive hexafluorobenzene (C6F6, leading to the first Pd(0-catalyzed cross-coupling reaction of C6F6 with diarylzinc compounds.

  3. Silver-catalyzed coupling reactions of alkyl halides with indenyllithiums

    OpenAIRE

    Someya, Hidenori; Yorimitsu, Hideki; Oshima, Koichiro

    2010-01-01

    Coupling reactions of tertiary and secondary alkyl halides with indenyllithiums proceeded effectively in the presence of a catalytic amount of silver bromide to provide tertiary- and secondary-alkyl-substituted indene derivatives in good yields.

  4. Copper and amine free Sonogashira cross-coupling reaction catalyzed by efficient diphosphane-palladium catalyst

    Institute of Scientific and Technical Information of China (English)

    Ting He; Lei Lei Wu; Xing Li Fu; Hai Yan Fu; Hua Chen; Rui Xiang Li

    2011-01-01

    The commercially available diphosphane ligand MeO-BIPHEP was first investigated in the palladium-catalyzed Sonogashira reaction in the absence of copper and amine. The coupling of various aryl bromides and aryl chlorides with phenylacetylene gave moderate to excellent yields.

  5. Chemoselective and Sequential Palladium-Catalyzed Couplings for the Generation of Stilbene Libraries via Immobilized Substrates.

    Science.gov (United States)

    Traficante, Carla I; Fagundez, Catherine; Serra, Gloria L; Mata, Ernesto G; Delpiccolo, Carina M L

    2016-05-01

    A versatile palladium-catalyzed tandem synthetic sequence to afford E-stilbenes libraries has been developed. Excellent regio- and stereocontrol have been achieved by means of the sequence of Hiyama and Heck cross-couplings. Undesirable homocoupling byproducts were avoided employing immobilized substrates. PMID:27073985

  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. Palladium-catalyzed carbonylative sonogashira coupling of aryl bromides using near stoichiometric carbon monoxide

    DEFF Research Database (Denmark)

    Neumann, Karoline T.; Laursen, Simon R.; Lindhardt, Anders T.;

    2014-01-01

    A general procedure for the palladium-catalyzed carbonylative Sonogashira coupling of aryl bromides is reported, using near stoichiometric amounts of carbon monoxide. The method allows a broad substrate scope in moderate to excellent yields. The formed alkynone motive serves as a platform for...

  8. Preparation of fluorinated biaryls through direct palladium-catalyzed coupling of polyfluoroarenes with aryltrifluoroborates

    KAUST Repository

    Fang, Xin

    2013-07-01

    The direct palladium-catalyzed coupling of polyfluoroarenes with aryltrifluoroborates gave the desired products of fluorinated biaryls in good to excellent yields. A diverse set of important functional groups including methoxy, aldehyde, ester, nitro and halide can be well tolerated in the protocol. © 2013 Elsevier B.V. All rights reserved.

  9. Copper-catalyzed arylation of biguanide derivatives via C-N cross-coupling reactions.

    Science.gov (United States)

    Zhang, Chen; Huang, Bo; Bao, Ai-Qing; Li, Xiao; Guo, Shunna; Zhang, Jin-Quan; Xu, Jun-Zhi; Zhang, Rihao; Cui, Dong-Mei

    2015-12-21

    An efficient copper-catalyzed cross-coupling reaction of biguanide hydrochloride derivatives with both aryl iodides and bromides under mild conditions has been developed. The reaction occurred in good yields and tolerated aryl halides containing functionalities such as nitriles, sulfonamides, ethers, and halogens. Alkyl and cyclic substituted biguanidines were also well tolerated. PMID:26444146

  10. Pd-catalyzed three-component coupling of terminal alkynes, arynes, and vinyl cyclopropane dicarboxylate.

    Science.gov (United States)

    Garve, Lennart K B; Werz, Daniel B

    2015-02-01

    A palladium-catalyzed three-component coupling involving in situ generated arynes, terminal alkynes, and vinyl cyclopropane dicarboxylate has been developed. The process demonstrates the first example of aryne chemistry combined with the ring opening of vinyl cyclopropanes. This efficient method using readily available starting materials generates two new carbon-carbon bonds in one pot. PMID:25625685

  11. Cu(I)-NHC-catalyzed silylation of allenes: diastereoselective three-component coupling with aldehydes.

    Science.gov (United States)

    Rae, James; Hu, Ya Chu; Procter, David J

    2014-10-01

    Copper-catalyzed silylation of aryl allenes using a silylborane reagent affords vinyl silane building blocks with high efficiency. The use of a seven-membered NHC ligand proved crucial for high regioselectivity. The catalytically generated allylcoppper intermediates were intercepted by aldehydes in a diastereoselective three-component coupling to furnish homoallylic alcohols. PMID:25146221

  12. Why You Really Should Consider Using Palladium-Catalyzed Cross-Coupling of Silanols and Silanolates

    OpenAIRE

    Denmark, Scott E.; Ambrosi, Andrea

    2015-01-01

    The transition metal-catalyzed cross-coupling of organometallic nucleophiles derived from tin, boron, and zinc with organic electrophiles enjoys a preeminent status among modern synthetic methods for the formation of carbon-carbon bonds. In recent years, organosilanes have emerged as viable alternatives to the conventional reagents, with the added benefits of low cost, low toxicity and high chemical stability. However, silicon-based cross-coupling reactions often require heating in the presen...

  13. Copper-Catalyzed Coupling of Oxime Acetates with Isothiocyanates: A Strategy for 2-Aminothiazoles.

    Science.gov (United States)

    Tang, Xiaodong; Zhu, Zhongzhi; Qi, Chaorong; Wu, Wanqing; Jiang, Huanfeng

    2016-01-15

    A new strategy for 2-aminothiazoles is developed via the copper-catalyzed coupling of oxime acetates with isothiocyanates. Various 4-substituted and 4,5-disubstituted 2-aminothiazoles were formed smoothly under mild reaction conditions. This process involved copper-catalyzed N-O bond cleavage, activation of vinyl sp(2) C-H bonds, and C-S/C-N bond formations. It is noteworthy that the oxime acetates were used not only as a substrate but also as a single oxidant. PMID:26729578

  14. Application of quinoxaline based diimidazolium salt in palladium catalyzed cross-coupling reactions

    Indian Academy of Sciences (India)

    Mujahuddin M Siddiqui; Mohammed Waheed; Sajad A Bhat; Maravanji S Balakrishna

    2015-05-01

    The reaction of 2,3-bis(bromomethyl)quinoxaline with imidazole afforded the quinoxaline bridged diimidazolium salt (1) in good yield. Diimidazolium salt (1) in conjunction with Pd(OAc)2 was employed as a catalyst for C–C cross-coupling reactions. The diimidazolium salt was found to be efficient in catalyzing Suzuki-Miyaura cross-coupling reaction in ethanol under ambient conditions. Moderate to good selectivity of the trans product was observed in the Heck cross-coupling reaction. The molecular structure of 1 was confirmed by single crystal X-ray diffraction study.

  15. A General Palladium-Catalyzed Hiyama Cross-Coupling Reaction of Aryl and Heteroaryl Chlorides.

    Science.gov (United States)

    Yuen, On Ying; So, Chau Ming; Man, Ho Wing; Kwong, Fuk Yee

    2016-05-01

    A general palladium-catalyzed Hiyama cross-coupling reaction of aryl and heteroaryl chlorides with aryl and heteroaryl trialkoxysilanes by a Pd(OAc)2 /L2 catalytic system is presented. A newly developed water addition protocol can dramatically improve the product yields. The conjugation of the Pd/L2 system and the water addition protocol can efficiently catalyze a broad range of electron-rich, -neutral, -deficient, and sterically hindered aryl chlorides and heteroaryl chlorides with excellent yields within three hours and the catalyst loading can be down to 0.05 mol % Pd for the first time. Hiyama coupling of heteroaryl chlorides with heteroaryl silanes is also reported for the first time. The reaction can be easily scaled up 200 times (100 mmol) without any degasification and purification of reactants; this facilitates the practical application in routine synthesis. PMID:26998586

  16. Pd- and Ni-catalyzed cross-coupling reactions in the synthesis of organic electronic materials

    International Nuclear Information System (INIS)

    Organic molecules and polymers with extended π-conjugation are appealing as advanced electronic materials, and have already found practical applications in thin-film transistors, light emitting diodes, and chemical sensors. Transition metal (TM)-catalyzed cross-coupling methodologies have evolved over the past four decades into one of the most powerful and versatile methods for C–C bond formation, enabling the construction of a diverse and sophisticated range of π-conjugated oligomers and polymers. In this review, we focus our discussion on recent synthetic developments of several important classes of π-conjugated systems using TM-catalyzed cross-coupling reactions, with a perspective on their utility for organic electronic materials. (review)

  17. Heterogeneous Rhodium-Catalyzed Aerobic Oxidative Dehydrogenative Cross-Coupling: Nonsymmetrical Biaryl Amines.

    Science.gov (United States)

    Matsumoto, Kenji; Yoshida, Masahiro; Shindo, Mitsuru

    2016-04-18

    The first heterogeneously catalyzed oxidative dehydrogenative cross-coupling of aryl amines is reported herein. 2-Naphthylamine analogues were reacted with various electron-rich arenes using a heterogeneous Rh/C catalyst under mild aerobic conditions, thus affording nonsymmetrical biaryl amines in excellent yields with high selectivities. This reaction provides a mild, operationally simple, and efficient approach for the synthesis of biaryls which are important to pharmaceutical and materials chemistry. PMID:26996772

  18. Nickel-catalyzed asymmetric reductive cross-coupling between vinyl and benzyl electrophiles.

    Science.gov (United States)

    Cherney, Alan H; Reisman, Sarah E

    2014-10-15

    A Ni-catalyzed asymmetric reductive cross-coupling between vinyl bromides and benzyl chlorides has been developed. This method provides direct access to enantioenriched products bearing aryl-substituted tertiary allylic stereogenic centers from simple, stable starting materials. A broad substrate scope is achieved under mild reaction conditions that preclude the pregeneration of organometallic reagents and the regioselectivity issues commonly associated with asymmetric allylic arylation. PMID:25245492

  19. Nickel-Catalyzed Asymmetric Reductive Cross-Coupling Between Vinyl and Benzyl Electrophiles

    OpenAIRE

    Cherney, Alan H.; Reisman, Sarah E.

    2014-01-01

    A Ni-catalyzed asymmetric reductive cross-coupling between vinyl bromides and benzyl chlorides has been developed. This method provides direct access to enantioenriched products bearing aryl-substituted tertiary allylic stereogenic centers from simple, stable starting materials. A broad substrate scope is achieved under mild reaction conditions that preclude the pregeneration of organometallic reagents and the regioselectivity issues commonly associated with asymmetric allylic arylation.

  20. Nickel-Catalyzed Cross-Coupling of Redox-Active Esters with Boronic Acids.

    Science.gov (United States)

    Wang, Jie; Qin, Tian; Chen, Tie-Gen; Wimmer, Laurin; Edwards, Jacob T; Cornella, Josep; Vokits, Benjamin; Shaw, Scott A; Baran, Phil S

    2016-08-01

    A transformation analogous in simplicity and functional group tolerance to the venerable Suzuki cross-coupling between alkyl-carboxylic acids and boronic acids is described. This Ni-catalyzed reaction relies upon the activation of alkyl carboxylic acids as their redox-active ester derivatives, specifically N-hydroxy-tetrachlorophthalimide (TCNHPI), and proceeds in a practical and scalable fashion. The inexpensive nature of the reaction components (NiCl2 ⋅6 H2 O-$9.5 mol(-1) , Et3 N) coupled to the virtually unlimited commercial catalog of available starting materials bodes well for its rapid adoption. PMID:27380912

  1. Palladium-catalyzed cross-coupling reactions of aryl boronic acids with aryl halides in water.

    Science.gov (United States)

    Wang, Shaoyan; Zhang, Zhiqiang; Hu, Zhizhi; Wang, Yue; Lei, Peng; Chi, Haijun

    2009-01-01

    An efficient Suzuki cross-coupling reaction using a variety of aryl halides in neat water was developed. The Pd-catalyzed reaction between aryl bromides or chlorides and phenyl boronic acids was compatible with various functional groups and affords biphenyls in good to excellent yields without requirement of organic cosolvents. The air stability and solubility in water of the palladium-phosphinous acid complexes were considered to facilitate operation of the coupling reaction and product isolation. The reaction conditions including Pd catalyst selection, temperature, base and catalyst recoverability were also investigated. PMID:25084408

  2. Rhodium-catalyzed C-C coupling reactions via double C-H activation.

    Science.gov (United States)

    Li, Shuai-Shuai; Qin, Liu; Dong, Lin

    2016-05-18

    Various rhodium-catalyzed double C-H activations are reviewed. These powerful strategies have been developed to construct C-C bonds, which might be widely embedded in complex aza-fused heterocycles, polycyclic skeletons and heterocyclic scaffolds. In particular, rhodium(iii) catalysis shows good selectivity and reactivity to functionalize the C-H bond, generating reactive organometallic intermediates in most of the coupling reactions. Generally, intermolecular, intramolecular and multi-component coupling reactions via double C-H activations with or without heteroatom-assisted chelation are discussed in this review. PMID:27099126

  3. Cobalt-catalyzed intermolecular C(sp(2))-O cross-coupling.

    Science.gov (United States)

    Kundu, Debasish; Tripathy, Manisha; Maity, Pintu; Ranu, Brindaban C

    2015-06-01

    Cobalt(II)-catalyzed C(sp(2) )O cross-coupling between aryl/heteroaryl alcohols and vinyl/aryl halides in the presence of Cu(I) has been achieved under ligand-free conditions. In this reaction, copper plays a significant role in transmetalation rather than being directly involved in the CO coupling. This unique Co/Cu-dual catalyst system provides an easy access to a library of aryl-vinyl, heteroaryl-styryl, aryl-aryl, and heteroaryl-heteroaryl ethers in the absence of any ligand or additive. PMID:25926040

  4. Iron-catalyzed coupling of aryl sulfamates and aryl/vinyl tosylates with aryl Grignards.

    Science.gov (United States)

    Agrawal, Toolika; Cook, Silas P

    2014-10-01

    The iron-catalyzed coupling of aryl sulfamates and tosylates with aryl Grignard reagents is reported for the first time. The methodology employs air-stable, low-cost FeF3·3H2O and the N-heterocyclic carbene ligand IPr·HCl as the preligand to form a long-lived catalyst upon treatment with aryl Grignards. The reaction provides a range of cross-coupled products in good-to-excellent yields. In contrast to previous reports with aryl chlorides, these reactions proceed with low levels of Grignard homocoupling regardless of the iron source. PMID:25230097

  5. Total Synthesis of Laulimalide: Assembly of the Fragments and Completion of the Synthesis of the Natural Product and a Potent Analogue

    OpenAIRE

    Trost, Barry M.; Amans, Dominique; Seganish, W. Michael; Chung, Cheol K.

    2012-01-01

    In this manuscript, we report the full account of our efforts to couple the northern and the southern building blocks, whose synthesis were described in the preceding paper, along with the modifications required which ultimately lead to a successful synthesis of laulimalide. Key highlights include an exceptionally efficient and atom-economical intramolecular ruthenium-catalyzed alkene-alkyne coupling to build the macrocycle followed by a highly stereoselective 1,3-allylic isomerization promot...

  6. Synthesis of Biaryls through Nickel-Catalyzed Suzuki-Miyaura Coupling of Amides by Carbon-Nitrogen Bond Cleavage.

    Science.gov (United States)

    Shi, Shicheng; Meng, Guangrong; Szostak, Michal

    2016-06-01

    The first Ni-catalyzed Suzuki-Miyaura coupling of amides for the synthesis of widely occurring biaryl compounds through N-C amide bond activation is reported. The reaction tolerates a wide range of electron-withdrawing, electron-neutral, and electron-donating substituents on both coupling partners. The reaction constitutes the first example of the Ni-catalyzed generation of aryl electrophiles from bench-stable amides with potential applications for a broad range of organometallic reactions. PMID:27101428

  7. Rhodium(III)-catalyzed C-C coupling of 7-azaindoles with vinyl acetates and allyl acetates.

    Science.gov (United States)

    Li, Shuai-Shuai; Wang, Cheng-Qi; Lin, Hui; Zhang, Xiao-Mei; Dong, Lin

    2016-01-01

    The behaviour of electron-rich alkenes with 7-azaindoles in rhodium(III)-catalyzed C-H activation is investigated. Various substituted vinyl acetates and allyl acetates as coupling partners reacted smoothly providing a wide variety of 7-azaindole derivatives, and the selectivity of the coupling reaction is alkene-dependent. In addition, the approaches of rhodium(III)-catalyzed dehydrogenative Heck-type reaction (DHR) and carbonylation reaction were quite novel and simple. PMID:26553424

  8. Cobalt-Catalyzed Cross-Coupling of Grignards with Allylic and Vinylic Bromides: Use of Sarcosine as a Natural Ligand.

    Science.gov (United States)

    Frlan, Rok; Sova, Matej; Gobec, Stanislav; Stavber, Gaj; Časar, Zdenko

    2015-08-01

    Sarcosine was discovered to be an excellent ligand for cobalt-catalyzed carbon-carbon cross-coupling of Grignard reagents with allylic and vinylic bromides. The Co(II)/sarcosine catalytic system is shown to perform efficiently when phenyl and benzyl Grignards are coupled with alkenyl bromides. Notably, previously unachievable Co-catalyzed coupling of allylic bromides with Grignards to linearly coupled α-products was also realized with Co(II)/sarcosine catalyst. This method was used for efficient preparation of the key intermediate in an alternative synthesis of the antihyperglycemic drug sitagliptin. PMID:26158563

  9. Palladium-Catalyzed Negishi Cross-Coupling Reaction of Aryl Halides with (Difluoromethyl)zinc Reagent.

    Science.gov (United States)

    Aikawa, Kohsuke; Serizawa, Hiroki; Ishii, Koki; Mikami, Koichi

    2016-08-01

    The palladium-catalyzed Negishi cross-coupling reaction of aryl iodides and bromides with (difluoromethyl)zinc reagent bearing a diamine such as TMEDA is achieved to provide the difluoromethylated aromatic compounds in good to excellent yields. The advantages of (difluoromethyl)zinc reagent are that (1) the derivatives, which possess different stability and reactivity, can be readily prepared via ligand screening and (2) transmetalation of a difluoromethyl group from the zinc reagent to palladium catalyst efficiently proceeds without an activator. PMID:27442347

  10. Nickel-catalyzed Electrochemical Coupling of Phenyl Halide and Study of Mechanism

    Institute of Scientific and Technical Information of China (English)

    ZHAO, Peng; LUO, Yi-Wen; XUE, Teng; ZHANG, Ai-Jian; LU, Jia-Xing

    2006-01-01

    Electrochemical coupling of phenyl halide catalyzed by NiCl2bpy in DMF has been investigated in this paper.Stainless steel was used as cathode and zinc as anode. Effects of potential, temperature and catalyst on electrolyses were studied to optimize the electrolytic conditions, with the maximal isolated yield under potentiostatic electrolysis to be 85%. Cyclic voltammetry of NiCl2bpy in the presence of phenyl bromide has been studied and mechanisms,concerned with several kinds of nickel complex, have been summarized.

  11. Intra- and Intermolecular Nickel-Catalyzed Reductive Cross-Electrophile Coupling Reactions of Benzylic Esters with Aryl Halides.

    Science.gov (United States)

    Konev, Mikhail O; Hanna, Luke E; Jarvo, Elizabeth R

    2016-06-01

    Nickel-catalyzed cross-electrophile coupling reactions of benzylic esters and aryl halides have been developed. Both inter- and intramolecular variants proceed under mild reaction conditions. A range of heterocycles and functional groups are tolerated under the reaction conditions. Additionally, the first example of a stereospecific cross-electrophile coupling of a secondary benzylic ester is described. PMID:27099968

  12. Palladium(0)-catalyzed cross-coupling of 1,1-diboronates with vinyl bromides and 1,1-dibromoalkenes.

    Science.gov (United States)

    Li, Huan; Zhang, Zhikun; Shangguan, Xianghang; Huang, Shan; Chen, Jun; Zhang, Yan; Wang, Jianbo

    2014-10-27

    Palladium-catalyzed cross-coupling reactions of 1,1-diboronates with vinyl bromides and dibromoalkenes were found to afford 1,4-dienes and allenes, respectively. These reactions utilize the high reactivities of both 1,1-diboronates and allylboron intermediates generated in the initial coupling. PMID:25213194

  13. Copper-catalyzed coupling of oxime acetates with sodium sulfinates: an efficient synthesis of sulfone derivatives.

    Science.gov (United States)

    Tang, Xiaodong; Huang, Liangbin; Xu, Yanli; Yang, Jidan; Wu, Wanqing; Jiang, Huanfeng

    2014-04-14

    Sulfone derivatives are important synthetic intermediates. However, the general method for their preparation is through traditional coupling reaction: the alkylation of sodium sulfinates with phenacyl halides. Based on our previous work on sodium sulfinates and oxime acetates, we herein report a novel method for sulfone derivatives by oxidative coupling with sodium sulfinates and oxime acetates using copper as catalyst. The sulfonylvinylamine products could be formed in excellent yields. Upon hydrolysis by silica gel in CH2 Cl2 , β-ketosulfones could also be efficiently constructed. Various sulfonylvinylamines and β-ketosulfones were obtained in good to excellent yields under the optimized reaction conditions. Mechanistic studies indicated that this transformation involved copper-catalyzed N-O bond cleavage, activation of a vinyl sp(2) C-H bond, and C-S bond formation. The oxime acetates act as both a substrate and an oxidant, thus the reaction needs no additional oxidants or additives. PMID:24677481

  14. General Copper-Catalyzed Coupling of Alkyl-, Aryl-, and Alkynylaluminum Reagents with Organohalides.

    Science.gov (United States)

    Shrestha, Bijay; Thapa, Surendra; Gurung, Santosh K; Pike, Ryan A S; Giri, Ramesh

    2016-02-01

    We report the first example of a very general Cu-catalyzed cross-coupling of organoaluminum reagents with organohalides. The reactions proceed for the couplings of alkyl-, aryl-, and alkynylaluminum reagents with aryl and heteroaryl halides and vinyl bromides, affording the cross-coupled products in good to excellent yields. Both primary and secondary alkylaluminum reagents can be utilized as organometallic coupling partners. These reactions are not complicated by β-hydride elimination, and as a result rearranged products are not observed with secondary alkylaluminum reagents even for couplings with heteroaryl halides under "ligand-free" conditions. Radical clock experiment with a radical probe and relative reactivity study of Ph3Al with two haloarenes, 1-bromonaphthalene and 4-chlorobenzonitrile, having two different redox potentials indicates that the reaction does not involve free aryl radicals and radical anions as intermediates. These results combined with the result of the Hammett plot obtained by reacting Ph3Al with iodoarenes containing p-H, p-Me, p-F, and p-CF3 substituents, which shows a linear curve (R(2) = 0.99) with a ρ value of +1.06, suggest that the current transformation follows an oxidative addition-reductive elimination pathway. PMID:26735748

  15. Mechanism and Selectivity in Nickel-Catalyzed Cross-Electrophile Coupling of Aryl Halides with Alkyl Halides

    OpenAIRE

    Biswas, Soumik; Weix, Daniel J.

    2013-01-01

    The direct cross-coupling of two different electrophiles, such as an aryl halide with an alkyl halide, offers many advantages over conventional cross-coupling methods that require a carbon nucleophile. Despite its promise as a versatile synthetic strategy, a limited understanding of the mechanism and origin of cross selectivity has hindered progress in reaction development and design. Herein, we shed light on the mechanism for the nickel-catalyzed cross-electrophile coupling of aryl halides w...

  16. Atom-efficient metal-catalyzed cross-coupling reaction of indium organometallics with organic electrophiles.

    Science.gov (United States)

    Pérez, I; Sestelo, J P; Sarandeses, L A

    2001-05-01

    The novel metal-catalyzed cross-coupling reaction of indium organometallics with organic electrophiles is described. Triorganoindium compounds (R(3)In) containing alkyl, vinyl, aryl, and alkynyl groups are efficiently prepared from the corresponding lithium or magnesium organometallics by reaction with indium trichloride. The cross-coupling reaction of R(3)In with aryl halides and pseudohalides (iodide 2, bromide 5, and triflate 4), vinyl triflates, benzyl bromides, and acid chlorides proceeds under palladium catalysis in excellent yields and with high chemoselectivity. Indium organometallics also react with aryl chlorides as under nickel catalysis. In the cross-coupling reaction the triorganoindium compounds transfer, in a clear example of atom economy, all three of the organic groups attached to the metal, as shown by the necessity of using only 34 mol % of indium. The feasibility of using R(3)In in reactions with different electrophiles, along with the high yields and chemoselectivities obtained, reveals indium organometallics to be useful alternatives to other organometallics in cross-coupling reactions. PMID:11457178

  17. CO2 as Both a Selective Agent and Reaction Media in Palladium-Catalyzed Reductive Ullmann-Type Coupling Reaction

    Institute of Scientific and Technical Information of China (English)

    LI Jin-Heng李金恒; XIE Ye-Xiang谢叶香

    2004-01-01

    Carbon dioxide as both a selective agent and reaction media in the palladium-catalyzed Ullmann-type coupling has been described. The results showed that aryl chlorides could be easily activated in the presence of carbon dioxide and the chemoselectivity shifted toward the palladium-catalyzed Ullmann-type coupling reaction. In liquid carbon dioxide, homocoupling reactions of aryl halides, including less reactive aryl chlorides, were carried out smoothly in moderate to good yields using Pd/C, zinc, and H2O as the catalytic system at room temperature.

  18. Highly selective fluorogenic multianalyte biosensors constructed via enzyme-catalyzed coupling and aggregation-induced emission.

    Science.gov (United States)

    Wang, Xiaorui; Hu, Jinming; Zhang, Guoying; Liu, Shiyong

    2014-07-16

    The development of a highly selective and fast responsive fluorogenic biosensor for diverse analytes ranging from bioactive small molecules to specific antigens is highly desirable but remains a considerable challenge. We herein propose a new approach by integrating substrate-selective enzymatic reactions with fluorogens exhibiting aggregation-induced emission feature. Tyrosine-functionalized tetraphenylethene, TPE-Tyr, molecularly dissolves in aqueous media with negligible fluorescence emission; upon addition of horseradish peroxidase (HRP) and H2O2, effective cross-linking occurs due to HRP-catalyzed oxidative coupling of tyrosine moieties in TPE-Tyr. This leads to fluorescence emission turn-on and fast detection of H2O2 with high sensitivity and selectivity. As a validation of the new strategy's generality, we further configure it into the biosensor design for glucose through cascade enzymatic reactions and for pathologically relevant antigens (e.g., human carcinoembryonic antigen) by combining with the ELISA kit. PMID:24983204

  19. A facile synthesis of terminal arylacetylenes via Sonogashira coupling reactions catalyzed by MCM-41-supported mercapto palladium(0) complex

    Institute of Scientific and Technical Information of China (English)

    Ya Ping Xu; Rong Hua Hu; Ramesh C.Kamboj

    2008-01-01

    A variety of terminal arylacetylenes have been conveniently synthesized in good to high yields via Sonogashira coupling of aryl iodides with (trimethylsilyl)acetylene catalyzed by MCM-41-supported mercapto palladium(0) complex,followed by desilylation under mild conditions.This polymeric palladium catalyst can be reused many times without any decrease in activity.

  20. New efficient ligand for sub-mol % copper-catalyzed C–N cross-coupling reactions running under air

    Directory of Open Access Journals (Sweden)

    Per-Fredrik Larsson

    2012-11-01

    Full Text Available A new efficient ligand, N,N’’-dimethyldiethylene triamine (DMDETA, has been synthesized and evaluated for sub-mol % copper-catalyzed C–N cross-coupling reactions. The efficiency of the ligand was determined by kinetic methods. DMDETA proved to display efficiency similar to DMEDA and, in addition, the resulting catalyst was tolerant to air.

  1. Palladium-catalyzed regioselective intramolecular coupling of o-carborane with aromatics via direct cage B-H activation.

    Science.gov (United States)

    Quan, Yangjian; Xie, Zuowei

    2015-03-18

    Palladium-catalyzed intramolecular coupling of o-carborane with aromatics via direct cage B-H bond activation has been achieved, leading to the synthesis of a series of o-carborane-functionalized aromatics in high yields with excellent regioselectivity. In addition, the site selectivity can also be tuned by the substituents on cage carbon atom. PMID:25747772

  2. A copper-catalyzed coupling reaction of vinyl halides and carbazates: application in the assembly of polysubstituted pyrroles.

    Science.gov (United States)

    Zhou, Chengang; Ma, Dawei

    2014-03-21

    CuI-catalyzed coupling of vinyl halides with carbazates gives N-protected N-alkenylhydrazines, which are condensed with ketones under acidic conditions to give polysubstituted pyrroles. The pyrrole synthesis may go through a similar mechanism with Fischer indole synthesis, which involves a [3,3]-sigmatropic rearrangement and other reactions. PMID:24514455

  3. Nickel-catalyzed Kumada cross-coupling reactions of tertiary alkylmagnesium halides and aryl bromides/triflates.

    Science.gov (United States)

    Joshi-Pangu, Amruta; Wang, Chao-Yuan; Biscoe, Mark R

    2011-06-01

    We report a Ni-catalyzed process for the cross-coupling of tertiary alkyl nucleophiles and aryl bromides. This process is extremely general for a wide range of electrophiles and generally occurs with a ratio of retention to isomerization >30:1. The same procedure also accommodates the use of aryl triflates, vinyl chlorides, and vinyl bromides as the electrophilic component. PMID:21553878

  4. Configurationally Stable, Enantioenriched Organometallic Nucleophiles in Stereospecific Pd-Catalyzed Cross-Coupling Reactions: An Alternative Approach to Asymmetric Synthesis

    Science.gov (United States)

    Wang, Chao-Yuan; Derosaa, Joseph

    2015-01-01

    Several research groups have recently developed methods to employ configurationally stable, enantioenriched organometallic nucleophiles in stereospecific Pd-catalyzed cross-coupling reactions. By establishing the absolute configuration of a chiral alkyltin or alkylboron nucleophile prior to its use in cross-coupling reactions, new stereogenic centers may be rapidly and reliably generated with preservation of the known initial stereochemistry. While this area of research is still in its infancy, such stereospecific cross-coupling reactions may emerge as simple, general methods to access diverse, optically active products from common enantioenriched organometallic building blocks. This minireview highlights recent progress towards the development of general, stereospecific Pd-catalyzed cross-coupling reactions using configurationally stable organometallic nucleophiles. PMID:26388985

  5. Mild and Phosphine-Free Iron-Catalyzed Cross-Coupling of Nonactivated Secondary Alkyl Halides with Alkynyl Grignard Reagents

    OpenAIRE

    Cheung, Chi Wai; Ren, Peng; Hu, Xile

    2014-01-01

    A simple protocol for iron-catalyzed cross-coupling of nonactivated secondary alkyl bromides and iodides with alkynyl Grignard reagents at room temperature has been developed. A wide range of secondary alkyl halides and terminal alkynes are tolerated to afford the substituted alkynes in good yields. A slight modification of the reaction protocol also allows for cross-coupling with a variety of primary alkyl halides.

  6. Hydroxymethylation beyond Carbonylation: Enantioselective Iridium-Catalyzed Reductive Coupling of Formaldehyde with Allylic Acetates via Enantiotopic π-Facial Discrimination.

    Science.gov (United States)

    Garza, Victoria J; Krische, Michael J

    2016-03-23

    Chiral iridium complexes modified by SEGPHOS catalyze the 2-propanol-mediated reductive coupling of branched allylic acetates 1a-1o with formaldehyde to form primary homoallylic alcohols 2a-2o with excellent control of regio- and enantioselectivity. These processes, which rely on enantiotopic π-facial discrimination of σ-allyliridium intermediates, represent the first examples of enantioselective formaldehyde C-C coupling beyond aldol addition. PMID:26958737

  7. Copper-Catalyzed Borylative Cross-Coupling of Allenes and Imines: Selective Three-Component Assembly of Branched Homoallyl Amines.

    Science.gov (United States)

    Rae, James; Yeung, Kay; McDouall, Joseph J W; Procter, David J

    2016-01-18

    A copper-catalyzed three-component coupling of allenes, bis(pinacolato)diboron, and imines allows regio-, chemo-, and diastereoselective assembly of branched α,β-substituted-γ-boryl homoallylic amines, that is, products bearing versatile amino, alkenyl, and borane functionality. Alternatively, convenient oxidative workup allows access to α-substituted-β-amino ketones. A computational study has been used to probe the stereochemical course of the cross-coupling. PMID:26632675

  8. Synthesis of alkenyl sulfides through the iron-catalyzed cross-coupling reaction of vinyl halides with thiols.

    Science.gov (United States)

    Lin, Yun-Yung; Wang, Yu-Jen; Lin, Che-Hung; Cheng, Jun-Hao; Lee, Chin-Fa

    2012-07-20

    We report here the iron-catalyzed cross-coupling reaction of alkyl vinyl halides with thiols. While many works are devoted to the coupling of thiols with alkyl vinyl iodides, interestingly, the known S-vinylation of vinyl bromides and chlorides is limited to 1-(2-bromovinyl)benzene and 1-(2-chlorovinyl)benzene. Investigation on the coupling reaction of challenging alkyl vinyl bromides and chlorides with thiols is rare. Since the coupling of 1-(2-bromovinyl)benzene and 1-(2-chlorovinyl)benzene with thiols can be performed in the absence of any catalyst, here we focus on the coupling of thiols with alkyl vinyl halides. This system is generally reactive for alkyl vinyl iodides and bromides to provide the products in good yields. 1-(Chloromethylidene)-4-tert-butyl-cyclohexane was also coupled with thiols, giving the targets in moderate yields. PMID:22708836

  9. Resting State and Elementary Steps of the Coupling of Aryl Halides with Thiols Catalyzed by Alkylbisphosphine Complexes of Palladium

    OpenAIRE

    Alvaro, Elsa; Hartwig, John F.

    2009-01-01

    Detailed mechanistic studies on the coupling of aryl halides with thiols catalyzed by palladium complexes of the alkylbisphosphine ligand CyPF-tBu (1-dicyclohexylphosphino-2-di-tert-butylphosphinoethylferrocene) are reported. The elementary steps that constitute the catalytic cycle, i.e. oxidative addition, transmetalation and reductive elimination, have been studied, and their relative rates are reported. Each of the steps of the catalytic process occurs at temperatures that are much lower t...

  10. Synthesis of Novel Aliphatic N-sulfonylamidino Thymine Derivatives by Cu(I)-catalyzed Three-component Coupling Reaction

    OpenAIRE

    Krstulović, Luka; Ismaili, Hamit; Višnjevac, Aleksandar; Glavaš-Obrovac, Ljubica; Žinić, Biserka

    2012-01-01

    A series of new aliphatic N-sulfonylamidino thymine derivatives containing nucleobase, N-sulfonyl and amidine pharmacophores in the structure were synthesized by Cu(I)-catalyzed threecomponent coupling of 1-propargyl thymine, benzenesulfonyl azides and amines or ammonium salts. Preliminary in vitro antitumor screening (human cervix adenocarcinoma -HeLa and leukemia cells - Jurkat) revealed promising activities of N,N-diethyl- (2) and N-4-cyanobenzyl- (6) derivatives of 4-acetamido...

  11. Anti-Markovnikov Hydroalkylation of Allylic Amine Derivatives via a Palladium–Catalyzed Reductive Cross-Coupling Reaction

    OpenAIRE

    DeLuca, Ryan J.; Sigman, Matthew S.

    2011-01-01

    A palladium-catalyzed hydroalkylation reaction of allylic amine derivatives by alkylzinc reagents is reported. This reductive cross-coupling yields anti-Markovnikov products using a variety of allylic amine protecting groups. Preliminary mechanistic studies suggest that a reversible β-hydride elimination/hydride insertion process furnishes the primary Pd-alkyl intermediate, which then undergoes transmetallation followed by reductive elimination to form a new sp3-sp3 carbon-carbon bond.

  12. Palladium-catalyzed coupling of N-tosylhydrazones and β-bromostyrene derivatives: new approach to 2H-chromenes.

    Science.gov (United States)

    Xia, Yamu; Xia, Ying; Zhang, Yan; Wang, Jianbo

    2014-12-14

    2H-Chromene is an important structural motif that exists in natural products and non-natural compounds possessing interesting biological activities. In this investigation, a highly efficient approach toward 2H-chromenes has been developed based on palladium-catalyzed coupling of N-tosylhydrazones and β-bromostyrenes. The mechanism of this reaction is proposed that involves the formation of vinyl palladium by carbene migratory insertion and the intramolecular nucleophilic substitution. PMID:25327448

  13. Suzuki-Miyaura Cross-Coupling Reactions of Unactivated Alkyl Halides Catalyzed by a Nickel Pincer Complex

    OpenAIRE

    Di Franco, Thomas; Boutin, Nicolas; Hu, Xile

    2013-01-01

    A nickel(II) pincer complex, [((N2N)-N-Me)Ni-Cl], was used to catalyze alkyl-alkyl and alkyl-aryl Suzuki-Miyaura coupling reactions of unactivated alkyl halides. The coupling of 9-alkyl-9-borabicyclo[3.3.1]nonane and 9-phenyl-9-borabicyclo[3.3.1]nonane reagents with alkyl halides was achieved in modest to good yields. The reactions tolerated a variety of useful functional groups including ester, ether, furan, thioether, acetal, and Boc groups.

  14. Amide as an efficient ligand in the palladium-catalyzed Suzuki coupling reaction in water/ethanol under aerobic conditions

    Institute of Scientific and Technical Information of China (English)

    Hai Yang Liu; Kun Wang; Hai Yan Fu; Mao Lin Yuan; Hua Chen; Rui Xiang Li

    2011-01-01

    Amide, which is derived from proline and is inexpensive and air-stable, has been synthesized and characterized by 1H NMR,13C NMR, and MS. It was found to be an efficient ligand in the palladium-catalyzed Suzuki cross-coupling reaction. In the Pd/amide catalytic system, aryl bromides can be coupled with phenylboronic acid in ethanol/water (1:2;v/v) in excellent yields even with a low Pd loading of 0.01 mol%. Moreover, the scope of the reaction is broad, and a wide variety of functional groups are tolerant.

  15. Synthesis of heterocyclic triads by Pd-catalyzed cross-couplings and evaluation of their cell-specific toxicity profile.

    Science.gov (United States)

    Salamoun, Joseph; Anderson, Shelby; Burnett, James C; Gussio, Rick; Wipf, Peter

    2014-04-01

    Two complementary approaches for the preparation of linked 5-membered heterocycles were developed. The Pd-catalyzed Suzuki-Miyaura cross-coupling with halogenated furan, thiophene, and selenophene led to higher overall yields, but C,H-bond activation was a more efficient strategy for the coupling at C(2) of oxazoles. Potency and selectivity of the final hydroxymethyl products in renal (A498), lung (NCI-H226), kidney (CAKI-1), and breast (MDA-MB-468, MCF7) carcinoma cell lines were determined. PMID:24641272

  16. Synthesis of Heterocyclic Triads by Pd-Catalyzed Cross-Couplings and Evaluation of Their Cell-Specific Toxicity Profile

    OpenAIRE

    Salamoun, Joseph; Anderson, Shelby; Burnett, James C.; Gussio, Rick; Wipf, Peter

    2014-01-01

    Two complementary approaches for the preparation of linked 5-membered heterocycles were developed. The Pd-catalyzed Suzuki–Miyaura cross-coupling with halogenated furan, thiophene, and selenophene led to higher overall yields, but C,H-bond activation was a more efficient strategy for the coupling at C(2) of oxazoles. Potency and selectivity of the final hydroxymethyl products in renal (A498), lung (NCI-H226), kidney (CAKI-1), and breast (MDA-MB-468, MCF7) carcinoma cell lines were determined.

  17. Efficient Negishi coupling reactions of aryl chlorides catalyzed by binuclear and mononuclear nickel-N-heterocyclic carbene complexes.

    Science.gov (United States)

    Xi, Zhenxing; Zhou, Yongbo; Chen, Wanzhi

    2008-11-01

    We describe the first nickel-N-heterocyclic carbene catalyzed Negishi cross-coupling reaction of a variety of unactivated aryl chlorides, heterocyclic chlorides, aryl dichlorides, and vinyl chloride. The mononuclear and binuclear nickel-NHC complexes supported by heteroarene-functionalized NHC ligands are found to be highly efficient for the coupling of unactivated aryl chlorides and organozinc reagents, leading to biaryls and terphenyls in good to excellent yields under mild conditions. For all aryl chlorides, the binuclear nickel catalysts show activities higher than those of mononuclear nickel complexes because of possible bimetallic cooperative effect. PMID:18841915

  18. Synthesis of trans-disubstituted alkenes by cobalt-catalyzed reductive coupling of terminal alkynes with activated alkenes.

    Science.gov (United States)

    Mannathan, Subramaniyan; Cheng, Chien-Hong

    2012-09-10

    A cobalt-catalyzed reductive coupling of terminal alkynes, RC≡CH, with activated alkenes, R'CH=CH(2), in the presence of zinc and water to give functionalized trans-disubstituted alkenes, RCH=CHCH(2)CH(2)R', is described. A variety of aromatic terminal alkynes underwent reductive coupling with activated alkenes including enones, acrylates, acrylonitrile, and vinyl sulfones in the presence of a CoCl(2)/P(OMe)(3)/Zn catalyst system to afford 1,2-trans-disubstituted alkenes with high regio- and stereoselectivity. Similarly, aliphatic terminal alkynes also efficiently participated in the coupling reaction with acrylates, enones, and vinyl sulfone, in the presence of the CoCl(2)/P(OPh)(3)/Zn system providing a mixture of 1,2-trans- and 1,1-disubstituted functionalized terminal alkene products in high yields. The scope of the reaction was also extended by the coupling of 1,3-enynes and acetylene gas with alkenes. Furthermore, a phosphine-free cobalt-catalyzed reductive coupling of terminal alkynes with enones, affording 1,2-trans-disubstituted alkenes as the major products in a high regioisomeric ratio, is demonstrated. In the reactions, less expensive and air-stable cobalt complexes, a mild reducing agent (Zn) and a simple hydrogen source (water) were used. A possible reaction mechanism involving a cobaltacyclopentene as the key intermediate is proposed. PMID:22865622

  19. Tandem Suzuki-Miyaura coupling/acid-catalyzed cyclization between vinyl ether boronates and vinyl halides: a concise approach to polysubstituted furans.

    Science.gov (United States)

    Butkevich, Alexey N; Meerpoel, Lieven; Stansfield, Ian; Angibaud, Patrick; Corbu, Andrei; Cossy, Janine

    2013-08-01

    Polysubstituted 2-(ω-hydroxyalkyl)furans were prepared by tandem Suzuki-Miyaura coupling/acid-catalyzed cyclization starting from appropriately substituted 3-haloallylic alcohols and dihydrofuran-, dihydropyran- or glycal-derived pinacol boronates. PMID:23855589

  20. Access to Isoquinolines and Isoquinolin-3-ols via Rh(III)-Catalyzed Coupling/Cyclization Cascade Reaction of Arylimidates and Diazo Compounds.

    Science.gov (United States)

    Li, Xing Guang; Sun, Min; Jin, Qiao; Liu, Kai; Liu, Pei Nian

    2016-05-01

    A Rh(III)-catalyzed coupling/cyclization cascade reaction is described, which involves arylimidates and diazo compounds and proceeds via intermolecular C-C bond formation and subsequent intramolecular C-N bond formation. Mechanistic investigation revealed that the reaction is a two-step process: the initial Rh(III)-catalyzed coupling/cyclization proceeds very fast and the following dehydration is rather slow. The reaction provides a direct approach to isoquinolines and isoquinolin-3-ols without any oxidants. PMID:27042947

  1. Copper-catalyzed cross-coupling of boronic esters with aryl iodides and application to the carboboration of alkynes and allenes.

    Science.gov (United States)

    Zhou, Yiqing; You, Wei; Smith, Kevin B; Brown, M Kevin

    2014-03-24

    Copper-catalyzed Suzuki–Miyaura-type cross-coupling and carboboration processes are reported. The cross-couplings function well with a variety of substituted aryl iodides and aryl boronic esters and allows for orthogonal reactivity compared to palladium-catalyzed processes. The carboboration method includes both alkynes and allenes and provides access to highly substituted and stereodefined vinyl boronic esters. The alkyne carboboration method is highlighted in the simple one-pot synthesis of Tamoxifen. PMID:24677502

  2. Gold-catalyzed tandem reactions of methylenecyclopropanes and vinylidenecyclopropanes.

    Science.gov (United States)

    Zhang, Di-Han; Tang, Xiang-Ying; Shi, Min

    2014-03-18

    Gold catalysis is often the key step in the synthesis of natural products, and is a powerful tool for tandem or domino reaction processes. Both gold salts and complexes are among the most powerful soft Lewis acids for electrophilic activation of carbon-carbon multiple bonds toward a variety of nucleophiles. The core of these reactions relies on the interaction between gold catalysts and π-bonds of alkenes, alkynes, and allenes. Activation of functional groups by gold complexes provides a useful and important method for facilitating many different organic transformations with high atom efficiency. Although they are highly strained, methylenecyclopropanes (MCPs) and vinylidenecyclopropanes (VDCPs) are readily accessible molecules that have served as useful building blocks in organic synthesis. Because of their unique structural and electronic properties, significant developments have been made in the presence of transition metal catalysts such as nickel, rhodium, palladium, and ruthenium during the past decades. However, less attention has been paid to the gold-catalyzed chemistry of MCPs and VDCPs. In this Account, we describe gold-catalyzed chemical transformations of MCPs and VDCPs developed both in our laboratory and by other researchers. Chemists have demonstrated that MCPs and VDCPs have amphiphilic properties. When MCPs or VDCPs are activated by a gold catalyst, subsequent nucleophilic attack by other reagents or ring-opening (ring-expansion) of the cyclopropane moiety will occur. However, the C-C double bonds of MCPs and VDCPs can also serve as nucleophilic reagents while more electrophilic reagents are present and activated by gold catalyst, and then further cascade reactions take place as triggered by the release of ring strain of cyclopropane. Based on this strategy, both our group and others have found some interesting gold-catalyzed transformations in recent years. These transformations of MCPs and VDCPs can produce a variety of polycyclic and

  3. Titanium-catalyzed multicomponent couplings: efficient one-pot syntheses of nitrogen heterocycles.

    Science.gov (United States)

    Odom, Aaron L; McDaniel, Tanner J

    2015-11-17

    Nitrogen-based heterocycles are important frameworks for pharmaceuticals, natural products, organic dyes for solar cells, and many other applications. Catalysis for the formation of heterocyclic scaffolds, like many C-C and C-N bond-forming reactions, has focused on the use of rare, late transition metals like palladium and gold. Our group is interested in the use of Earth-abundant catalysts based on titanium to generate heterocycles using multicomponent coupling strategies, often in one-pot reactions. To be of maximal utility, the catalysts need to be easily prepared from inexpensive reagents, and that has been one guiding principle in the research. For this purpose, a series of easily prepared pyrrole-based ligands has been developed. Titanium imido complexes are known to catalyze the hydroamination of alkynes, and this reaction has been used to advantage in the production of α,β-unsaturated imines from 1,3-enynes and pyrroles from 1,4-diynes. Likewise, catalyst design can be used to find complexes applicable to hydrohydrazination, coupling of a hydrazine and alkyne, which is a method for the production of hydrazones. Many of the hydrazones synthesized are converted to indoles through Fischer cyclization by addition of a Lewis acid. However, more complex products are available in a single catalytic cycle through coupling of isonitriles, primary amines, and alkynes to give tautomers of 1,3-diimines, iminoamination (IA). The products of IA are useful intermediates for the one-pot synthesis of pyrazoles, pyrimidines, isoxazoles, quinolines, and 2-amino-3-cyanopyridines. The regioselectivity of the reactions is elucidated in some detail for some of these heterocycles. The 2-amino-3-cyanopyridines are synthesized through isolable intermediates, 1,2-dihydro-2-iminopyridines, which undergo Dimroth rearrangement driven by aromatization of the pyridine ring; the proposed mechanism of the reaction is discussed. The IA-based heterocyclic syntheses can be accomplished

  4. Carborane phosphorus-derivatives as ligands for Pd-catalyzed cross-coupling reactions

    International Nuclear Information System (INIS)

    Synthesis of carborane-containing phosphine ligands possessing different steric and electronic properties has been considered. Testing of the given ligands in Pd-catalyzed Suzuki-Miyaura reaction demonstrated that sterically volume phosphine ligands with acceptor carborane substitutes possessed the most catalytic activity

  5. Copper-Catalyzed Enantioselective Intramolecular Alkene Amination/Intermolecular Heck-Type Coupling Cascade

    OpenAIRE

    Liwosz, Timothy W.; Chemler, Sherry R.

    2012-01-01

    Enantioselective copper-catalyzed cycliza-tion of γ-alkenylsulfonamides and a δ-alkenylsulfonamide in the presence of a range of vinyl arenes results in variously functionalized 2-substituted chiral nitrogen heterocycles via a formal alkene C–H functionalization process. Application of this reaction to the concise synthesis of a 5-HT7 receptor antagonist is demonstrated.

  6. Copper-catalyzed enantioselective intramolecular alkene amination/intermolecular Heck-type coupling cascade.

    Science.gov (United States)

    Liwosz, Timothy W; Chemler, Sherry R

    2012-02-01

    Enantioselective copper-catalyzed cyclization of γ-alkenylsulfonamides and a δ-alkenylsulfonamide in the presence of a range of vinyl arenes results in variously functionalized 2-substituted chiral nitrogen heterocycles via a formal alkene C-H functionalization process. Application of this reaction to the concise synthesis of a 5-HT(7) receptor antagonist is demonstrated. PMID:22257169

  7. Atom-Economic and Stereoselective Syntheses of the A- and B-Ring Subunits of the Bryostatins

    OpenAIRE

    Trost, Barry M.; Yang, Hanbiao; Brindle, Cheyenne S.; Dong, Guangbin

    2011-01-01

    This article describes chemoselective and atom-economical methods for the stereoselective assembly of the A- and B-ring subunits of the bryostatins. A Ru-catalyzed tandem alkene-alkyne coupling/Michael addition was developed and applied to the synthesis of the bryostatin B-ring. We explored an acetylide-mediated epoxide-opening/6-exo-dig cyclization route to access the bryostatin A-ring; and the A-ring was eventually furnished via an acid-catalyzed tandem transketalization/ketalization sequen...

  8. Palladium-Catalyzed Ullmann Cross-Coupling/Tandem Reductive Cyclization Route to Key Members of the Uleine Alkaloid Family.

    Science.gov (United States)

    Tang, Fei; Banwell, Martin G; Willis, Anthony C

    2016-04-01

    The trisubstituted cyclohexenone 12, generated through a palladium-catalyzed Ullmann cross-coupling reaction between o-iodonitrobenzene and a 4,5-trans-disubstituted 2-iodo-2-cyclohexen-1-one, engaged in a tandem reductive cyclization process upon exposure to hydrogen gas in the presence of Raney cobalt. As a result, the 1,5-methanoazocino[4,3-b]indole 13 was obtained and this could be readily elaborated to the racemic modifications of the alkaloids uleine, dasycarpidone, noruleine, and nordasycarpidone (1-4, respectively). PMID:26914482

  9. B-N, B-O, and B-CN Bond Formation via Palladium-Catalyzed Cross-Coupling of B-Bromo-Carboranes.

    Science.gov (United States)

    Dziedzic, Rafal M; Saleh, Liban M A; Axtell, Jonathan C; Martin, Joshua L; Stevens, Simone L; Royappa, A Timothy; Rheingold, Arnold L; Spokoyny, Alexander M

    2016-07-27

    Carboranes are boron-rich molecules that can be functionalized through metal-catalyzed cross-coupling. Here, for the first time, we report the use of bromo-carboranes in palladium-catalyzed cross-coupling for efficient B-N, B-O, and unprecedented B-CN bond formation. In many cases bromo-carboranes outperform the traditionally utilized iodo-carborane species. This marked difference in reactivity is leveraged to circumvent multistep functionalization by directly coupling small nucleophiles (-OH, -NH2, and -CN) and multiple functional groups onto the boron-rich clusters. PMID:27384544

  10. Preparation of 5-acyl- and 5-aryl-substituted 1-(benzyloxy)pyrazoles via directed ortho-lithiation/transmetalation and palladium catalyzed cross- coupling

    DEFF Research Database (Denmark)

    Kristensen, Jesper Langgaard; Begtrup, M.; Vedsø, P.

    1998-01-01

    Palladium(0) catalyzed cross-coupling of 1-(benzyloxy)pyrazol-5-ylzinc halides 3a,b, prepared by transmetalation of 1-(benzyloxy)-5-lithiopyrazole (2), with acyl chlorides produced 5 acyl-1-(benzyloxy)pyrazoles 4a-d in high yields. Similar coupling of the pyrazol-5-ylzinc halide with amino...

  11. Peroxidase-Catalyzed Oxidative Coupling of Phenols in the Presence of Geosorbents

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qingguo; Weber, Walter J., Jr.

    2003-03-26

    This study focuses on elucidation of the reaction behaviors of peroxidase-mediated phenol coupling in the presence of soil/sediment materials. Our goal is a mechanistic understanding of the influences of geosorbent materials on enzymatic coupling reactions in general and the development of methods for predicting such influences. Extensive experimental investigations of coupling reactions were performed under strategically selected conditions in systems containing model geosorbents having different properties and chemical characteristics. The geosorbents tested were found to influence peroxidase-mediated phenol coupling through one or both of two principal mechanisms; i.e., (1) mitigation of enzyme inactivation and/or (2) participation in cross-coupling reactions. Such influences were found to correlate with the chemical characteristics of the sorbent materials and to be simulated well by a modeling approach designed in this paper. The results of the study have important implications for potential engineering implementation and enhancement of enzymatic coupling reactions in soil/subsurface remediation practice.

  12. Congested C-C Bonds by Pd-Catalyzed Enantioselective Allyl-Allyl Cross-Coupling, A Mechanism-Guided Solution

    OpenAIRE

    Ardolino, Michael J.; Morken, James P.

    2014-01-01

    Under the influence of a chiral bidentate diphosphine ligand, the Pd-catalyzed asymmetric cross-coupling of allylboron reagents and allylic electrophiles establishes 1,5-dienes with adjacent stereocenters in high regio- and stereoselectivity. . A mechanistic study of the coupling utilizing reaction calorimetry and density functional theory analysis suggests that the reaction operates through an inner-sphere 3,3'-reductive elimination pathway, which is both rate- and stereodefining. Coupled wi...

  13. Selective coupling reaction between 2,6-diiodoanisoles and terminal alkynes catalyzed by Pd(PPh32Cl2 and CuI

    Directory of Open Access Journals (Sweden)

    Allan F. C. Rossini

    2012-06-01

    Full Text Available The cross-coupling reaction between aryl halides and terminal alkynes, catalyzed by palladium complexes and copper (I salts, consists in an efficient synthetic tool for the formation of C-C bonds, resulting in disubstituted acetylenic compounds. Accordingly, in this work we present our preliminary results involving the selective cross-coupling reaction between 2,6-diiodoanisoles and terminal alkynes, catalyzed by Pd(PPh32Cl2 and CuI, in the formation of 2-iodo-alkynylanisoles (scheme 1.

  14. Recyclable heterogeneous copper oxide on alumina catalyzed coupling of phenols and alcohols with aryl halides under ligand-free conditions.

    Science.gov (United States)

    Swapna, Kokkirala; Murthy, Sabbavarapu Narayana; Jyothi, Mocharla Tarani; Nageswar, Yadavalli Venkata Durga

    2011-09-01

    An efficient alumina-supported CuO-catalyzed O-arylation of phenols and aliphatic alcohols with various aryl as well as heteroaryl halides under ligand-free conditions are reported. This protocol provides a variety of diaryl ether and bis-diaryl ether motifs by reacting different aryl/aliphatic halides with differently substituted phenols and saturated alcohols in the presence of a catalytic amount of CuO on alumina and KOH as a base at moderate temperature under nitrogen atmosphere. The described methodology is simple, straightforward and efficient to afford the cross-coupled products in high yields under ligand-free conditions. The explored catalyst is inexpensive, air-stable and recyclable up to three cycles. PMID:21695321

  15. Photoelectrochemistry of the thallic/thallous couple - The thallic ion catalyzed photo-oxidation of propylene

    Science.gov (United States)

    Switzer, J. A.; Moorehead, E. L.; Dalesandro, D. M.

    1982-10-01

    Liquid-junction photovoltaic and photoelectrosynthetic applications of the thallic/thallous couple have been investigated. In the liquid-junction photovoltaic mode the redox couple produces large photovoltages with several semiconductors (TiO2, MoS2, CdS, and GaAs), and does not absorb appreciable semiconductor ultra-bandgap light. The couple also shows photoelectrosynthetic utility, since the thallic ion is a selective two-electron oxidizing agent for a variety of organic substrates. Preliminary work on the photoassisted epoxidation of propylene at n-type semiconductor electrodes (TiO2) and powders (TiO2, WO3, and ZnO) is discussed.

  16. Pd(II/HPMoV-Catalyzed Direct Oxidative Coupling Reaction of Benzenes with Olefins

    Directory of Open Access Journals (Sweden)

    Yasutaka Ishii

    2010-03-01

    Full Text Available The direct aerobic coupling reaction of arenes with olefins was successfully achieved by the use of Pd(OAc2/molybdovanadophosphoric acid (HPMoV as a key catalyst under 1 atm of dioxygen. This catalytic system could be extended to the coupling reaction of various substituted benzenes with olefins such as acrylates, aclrolein, and ethylene through the direct aromatic C-H bond activation.

  17. Kumada coupling of aryl, heteroaryl, and vinyl chlorides catalyzed by amido pincer nickel complexes.

    Science.gov (United States)

    Liu, Ning; Wang, Zhong-Xia

    2011-12-16

    A series of amido pincer complexes of nickel were examined for their catalysis in the Kumada cross-coupling reaction. The P,N,O-pincer nickel complexes tested are active catalysts for the cross-coupling of aryl, heteroaryl, and vinyl chlorides with aryl Grignard reagents. The reactions can proceed at room temperature and tolerate functional groups in aryl chlorides with the aid of LiCl and ZnCl(2) additives. PMID:22077596

  18. Rh(III)-Catalyzed C-C/C-N Coupling of Imidates with α-Diazo Imidamide: Synthesis of Isoquinoline-Fused Indoles.

    Science.gov (United States)

    Wang, He; Li, Lei; Yu, Songjie; Li, Yunyun; Li, Xingwei

    2016-06-17

    Imidate esters and diazo compounds have been established as bifunctional substrates for the construction of biologically active fused heterocycles via rhodium-catalyzed C-H activation and C-C/C-N coupling. This reaction occurs under mild conditions with high efficiency, step economy, and low catalyst loading. PMID:27280947

  19. A facile approach to asymmetrical biaryls via coupling reaction of aryl halides with sodium tetraphenylborate catalyzed by MCM-41-supported sulfur palladium(O) complex

    Institute of Scientific and Technical Information of China (English)

    Qiu Hua Xu; Ping Ping Wang; Ming Zhong Cai

    2007-01-01

    Various functionalized asymmetrical biaryls can be synthesized in high to excellent yields via coupling reaction of aryl iodides or bromides with NaBPh4 catalyzed by MCM-41-supported sulfur palladium(O) complex. This palladium complex can be easily recovered and reused many times without loss of activity.

  20. Strategic use of nickel(0)-catalyzed enyne-epoxide reductive coupling towards the synthesis of (−)-cyatha-3,12-diene

    OpenAIRE

    Sparling, Brian A.; Simpson, Graham L.; Jamison, Timothy F.

    2009-01-01

    Various situations are explored in which the nickel(0)-catalyzed enyne-epoxide reductive coupling was utilized to access key intermediates towards the total synthesis of (−)-cyatha-3,12-diene (1). Enantioenriched 3,5-dien-1-ols with a variety of functionality were obtained in a straightforward manner from easily accessible 1,3-enynes and terminal epoxides.

  1. Palladium-catalyzed cross-coupling reaction of diazo compounds and vinyl boronic acids: an approach to 1,3-diene compounds.

    Science.gov (United States)

    Xia, Yamu; Xia, Ying; Liu, Zhen; Zhang, Yan; Wang, Jianbo

    2014-08-15

    A palladium-catalyzed oxidative cross-coupling of vinyl boronic acids and cyclic α-diazocarbonyl compounds has been reported. The reaction constitutes an efficient method for the synthesis of 1,3-diene compounds bearing a ring structure. Mechanistically, the reaction involves migratory insertion of palladium carbene as the key step. PMID:25019414

  2. Room-temperature Kumada cross-coupling of unactivated aryl chlorides catalyzed by N-heterocylic carbene-based nickel(II) complexes.

    Science.gov (United States)

    Xi, Zhenxing; Liu, Bin; Chen, Wanzhi

    2008-05-16

    The Kumada cross-coupling reaction of a variety of unactivated aryl chlorides, vinyl chlorides, and heteroaryl chlorides catalyzed by nickel(II) complexes containing pyridine-functionalized NHC ligands is described. The catalysts are so active that the reactions proceed at room temperature in excellent yields. PMID:18412386

  3. Studies with Michael addition reaction and with palladium-catalyzed cross coupling

    Czech Academy of Sciences Publication Activity Database

    Wimmer, Zdeněk; Jackson, F. W.

    Arcachon, 2002. s. P20. [COST Chemistry D12. Organic Transformations Selective Processes and Asymmetric Catalysis.. 25.09.2002-29.09.2002, Arcachon] Institutional research plan: CEZ:AV0Z4055905 Keywords : cross coupling Subject RIV: CC - Organic Chemistry

  4. Efficient Sonogashira and Suzuki-Miyaura coupling reaction catalyzed by Pd-Nanoparticles

    Indian Academy of Sciences (India)

    Kishor E Balsane; Suresh S Shendage; Jayashree M Nagarkar

    2015-03-01

    The Pd nano particles were electrochemically deposited on nafion-graphene. They showed excellent catalytic activity towards Sonogashira and Suzuki-Miyaura cross-coupling reaction. Benzenediazonium salts were used as alternative to aromatic halide. The developed protocol offers recyclability, easy workups with short reaction time and good-to-excellent product yield.

  5. Facile palladium catalyzed Suzuki-Miyaura coupling in air and water at ambient temperature

    KAUST Repository

    Marziale, Alexander N.

    2010-01-01

    A new palladacyclic catalyst yields high activities in aqueous Suzuki-Miyaura coupling at room temperature. Using an optimized protocol, a broad range of products can be isolated in good to excellent yields and high purity by simple filtration. © 2010 The Royal Society of Chemistry.

  6. Coupling of Carbon Dioxide with Epoxides Catalyzed by Amino Acid Hydrochloride Salts

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Using amino acid hydrochloride salt as a catalyst, the coupling reaction of CO2 with epoxides could proceed smoothly to give cyclic carbonates in very good yields and high selectivity. The reaction conditions such as the pressure of carbon dioxide, reaction temperature, time and catalyst loading were carefully investigated.

  7. Enantioselective CuH-Catalyzed Reductive Coupling of Aryl Alkenes and Activated Carboxylic Acids.

    Science.gov (United States)

    Bandar, Jeffrey S; Ascic, Erhad; Buchwald, Stephen L

    2016-05-11

    A new method for the enantioselective reductive coupling of aryl alkenes with activated carboxylic acid derivatives via copper hydride catalysis is described. Dual catalytic cycles are proposed, with a relatively fast enantioselective hydroacylation cycle followed by a slower diastereoselective ketone reduction cycle. Symmetrical aryl carboxyclic anhydrides provide access to enantioenriched α-substituted ketones or alcohols with excellent stereoselectivity and functional group tolerance. PMID:27121395

  8. Gas-phase studies of copper catalyzed aerobic cross coupling of thiol esters and arylboronic acids

    Czech Academy of Sciences Publication Activity Database

    Tsybizová, A.; Schröder, Detlef; Roithová, J.; Henke, A.; Šrogl, Jiří

    2014-01-01

    Roč. 27, č. 3 (2014), s. 198-203. ISSN 0894-3230 R&D Projects: GA ČR GAP207/12/0846 Grant ostatní: GA ČR(CZ) GAP207/11/0338 Institutional support: RVO:61388963 Keywords : boronic acids * catalysis * copper * cross coupling * electrospray ionization * mass spectrometry * kinetic studies Subject RIV: CC - Organic Chemistry Impact factor: 1.380, year: 2014

  9. Substrate-Directed Hydroacylation: Rh-Catalyzed Coupling of Vinyl Phenols and Non-Chelating Aldehydes

    OpenAIRE

    Murphy, Stephen K.; Bruch, Achim; Dong, Vy M.

    2014-01-01

    We report a protocol for branched-selective hydroacylation of vinylphenols with aryl, alkenyl and alkyl aldehydes. This cross-coupling yields α-aryl ketones that can be cyclized to benzofurans, and it enables access to eupomatenoid natural products in four steps or less from eugenol. Excellent reactivity and high levels of branched regioselectivity are obtained. We propose that aldehyde decarbonylation is overcome by using an anionic directing group on the olefin and a small bite-angle diphos...

  10. Practical Ni-Catalyzed Aryl-Alkyl Cross-Coupling of Secondary Redox-Active Esters.

    Science.gov (United States)

    Cornella, Josep; Edwards, Jacob T; Qin, Tian; Kawamura, Shuhei; Wang, Jie; Pan, Chung-Mao; Gianatassio, Ryan; Schmidt, Michael; Eastgate, Martin D; Baran, Phil S

    2016-02-24

    A new transformation is presented that enables chemists to couple simple alkyl carboxylic acids with aryl zinc reagents under Ni-catalysis. The success of this reaction hinges on the unique use of redox-active esters that allow one to employ such derivatives as alkyl halides surrogates. The chemistry exhibits broad substrate scope and features a high degree of practicality. The simple procedure and extremely inexpensive nature of both the substrates and pre-catalyst (NiCl2·6H2O, ca. $9.5/mol) bode well for the immediate widespread adoption of this method. PMID:26835704

  11. Palladium-catalyzed cross coupling reactions of 4-bromo-6H-1,2-oxazines

    Directory of Open Access Journals (Sweden)

    Reinhold Zimmer

    2009-09-01

    Full Text Available A number of 4-aryl- and 4-alkynyl-substituted 6H-1,2-oxazines 8 and 9 have been prepared in good yields via cross coupling reactions of halogenated precursors 2, which in turn are easily accessible by bromination of 6H-1,2-oxazines 1. Lewis-acid promoted reaction of 1,2-oxazine 9c with 1-hexyne provided alkynyl-substituted pyridine derivative 12 thus demonstrating the potential of this approach for the synthesis of pyridines.

  12. Nickel-catalyzed electrochemical couplings of vinyl halides: synthetic and stereochemical aspects

    Science.gov (United States)

    Cannes; Condon; Durandetti; Perichon; Nedelec

    2000-07-28

    Homo- and cross-coupling involving alkenyl halides have been performed efficiently using an electroassisted nickel-complex catalysis. Valuable product such as conjugated dienes, beta,gamma- or gamma,delta-unsaturated esters, ketones, or nitriles, as well as alkenylated aryl compounds are thus prepared with high yields and high stereoselectivity. Partial isomerization is only observed in a few cases, when the alkenyl halide is involved in a late step of the catalytic cycle. This is the case in the preparation of (Z,Z)-1,3-diene. PMID:10959862

  13. Cross-coupling reaction of alkyl halides with grignard reagents catalyzed by Ni, Pd, or Cu complexes with pi-carbon ligand(s).

    Science.gov (United States)

    Terao, Jun; Kambe, Nobuaki

    2008-11-18

    Transition metal-catalyzed cross-coupling reactions of organic halides and pseudo-halides containing a C-X bond (X = I, Br, Cl, OTf, OTs, etc.) with organometallic reagents are among the most important transformations for carbon-carbon bond formation between a variety of sp, sp(2), and sp(3)-hybridized carbon atoms. In particular, researchers have widely employed Ni- and Pd-catalyzed cross-coupling to synthesize complex organic structures from readily available components. The catalytic cycle of this process comprises oxidative addition, transmetalation, and reductive elimination steps. In these reactions, various organometallic reagents could bear a variety of R groups (alkyl, vinyl, aryl, or allyl), but the coupling partner has been primarily limited to sp and sp(2) carbon compounds: alkynes, alkenes, and arenes. With alkyl coupling partners, these reactions typically run into two problems within the catalytic cycle. First, oxidative addition of alkyl halides to a metal catalyst is generally less efficient than that of aryl or alkenyl compounds. Second, the alkylmetal intermediates formed tend to undergo intramolecular beta-hydrogen elimination. In this Account, we describe our efforts to overcome these problems for Ni and Pd chemistry. We have developed new catalytic systems that do not involve M(0) species but proceed via an anionic complex as the key intermediate. For example, we developed a unique cross-coupling reaction of alkyl halides with organomagnesium or organozinc reagents catalyzed by using a 1,3-butadiene as the additive. This reaction follows a new catalytic pathway: the Ni or Pd catalyst reacts first with R-MgX to form an anionic complex, which then reacts with alkyl halides. Bis-dienes were also effective additives for the Ni-catalyzed cross-coupling reaction of organozinc reagents with alkyl halides. This catalytic system tolerates a wide variety of functional groups, including nitriles, ketones, amides, and esters. In addition, we have extended

  14. Nucleus-Coupled Electron Transfer Mechanism for TiO2-Catalyzed Water Splitting

    Science.gov (United States)

    Sun, Yiyang; Lucking, Michael; West, Damien; Zhang, Shengbai

    2014-03-01

    Using first-principles calculations employing explicit interface of TiO2 crystal and liquid water, we reveal the microscopic mechanism of the oxygen evolution reaction (OER). It is found that, during the formation of an O-O species, such as HO-OH and O-OH, an occupied molecular orbital with anti-bonding character evolves from the valence band and pops up all the way into the conduction band of TiO2. This occupied high-energy orbital results in a high reaction barrier making the OER forbidden in the dark. The presence of photoholes depletes this anti-bonding orbital, which significantly reduces the reaction energy and determines the reaction barrier in the rate-limting step. A novel reaction mechanism, termed necleus-coupled electron transfer (NCET), emerges from this study. In this mechanism, the oxidation of a pair of hydroxyl groups, which is an electron transfer reaction, is enabled by the movement of the nuclei (i.e., the two O atoms moving towards O-O bond formation) that pushes the reactive orbital (the σ2p * orbital in the present case) to become the frontier orbital (i.e., above the valence band maximum of TiO). Based on the NCET mechanism, we identify a reaction pathway of the OER that exhibits a kinetic barrier surmountable at room temperature. The presenter acknowledges NSF support under Award No. DMR-1104994.

  15. Pd-Catalyzed Coupling of γ-C(sp(3))-H Bonds of Oxalyl Amide-Protected Amino Acids with Heteroaryl and Aryl Iodides.

    Science.gov (United States)

    Han, Jian; Zheng, Yongxiang; Wang, Chao; Zhu, Yan; Huang, Zhi-Bin; Shi, Da-Qing; Zeng, Runsheng; Zhao, Yingsheng

    2016-07-01

    Pd-catalyzed regioselective coupling of γ-C(sp(3))-H bonds of oxalyl amide-protected amino acids with heteroaryl and aryl iodides is reported. A wide variety of iodides are tolerated, giving the corresponding products in moderate to good yields. Various oxalyl amide-protected amino acids were compatible in this C-H transformation, thus representing a practical method for constructing non-natural amino acid derivatives. PMID:27286881

  16. A Palladium-Catalyzed Three-Component Cross-Coupling of Conjugated Dienes or Terminal Alkenes with Vinyl Triflates and Boronic Acids

    OpenAIRE

    Liao, Longyan; Jana, Ranjan; Urkalan, Kaveri Balan; Sigman, Matthew S.

    2011-01-01

    A three-component coupling of vinyl triflates and boronic acids to alkenes catalyzed by palladium is reported. Using 1,3-dienes, selective 1,2-alkene difunctionalization is observed, whereas the use of terminal alkenes results in 1,1-alkene difunctionalization. The reaction outcome is attributed to the formation of stabilized, cationic Pd-π-allyl intermediates to regulate β-hydride elimination.

  17. Copper-assisted nickel catalyzed ligand-free C(sp2)-O cross-coupling of vinyl halides and phenols.

    Science.gov (United States)

    Kundu, Debasish; Maity, Pintu; Ranu, Brindaban C

    2014-02-21

    A convenient and efficient protocol has been achieved for the cross-coupling of phenols and vinyl halides by a unique Ni/Cu catalytic system for the first time, where the reaction is catalyzed by Ni and Cu is involved in the transmetalation process. This procedure provides an easy access to a library of aryl-vinyl and aryl-styrenyl ethers. PMID:24502267

  18. Simultaneous Determination of Size and Quantification of Gold Nanoparticles by Direct Coupling Thin layer Chromatography with Catalyzed Luminol Chemiluminescence

    Science.gov (United States)

    Yan, Neng; Zhu, Zhenli; He, Dong; Jin, Lanlan; Zheng, Hongtao; Hu, Shenghong

    2016-04-01

    The increasing use of metal-based nanoparticle products has raised concerns in particular for the aquatic environment and thus the quantification of such nanomaterials released from products should be determined to assess their environmental risks. In this study, a simple, rapid and sensitive method for the determination of size and mass concentration of gold nanoparticles (AuNPs) in aqueous suspension was established by direct coupling of thin layer chromatography (TLC) with catalyzed luminol-H2O2 chemiluminescence (CL) detection. For this purpose, a moving stage was constructed to scan the chemiluminescence signal from TLC separated AuNPs. The proposed TLC-CL method allows the quantification of differently sized AuNPs (13 nm, 41 nm and 100 nm) contained in a mixture. Various experimental parameters affecting the characterization of AuNPs, such as the concentration of H2O2, the concentration and pH of the luminol solution, and the size of the spectrometer aperture were investigated. Under optimal conditions, the detection limits for AuNP size fractions of 13 nm, 41 nm and 100 nm were 38.4 μg L‑1, 35.9 μg L‑1 and 39.6 μg L‑1, with repeatabilities (RSD, n = 7) of 7.3%, 6.9% and 8.1% respectively for 10 mg L‑1 samples. The proposed method was successfully applied to the characterization of AuNP size and concentration in aqueous test samples.

  19. Simultaneous Determination of Size and Quantification of Gold Nanoparticles by Direct Coupling Thin layer Chromatography with Catalyzed Luminol Chemiluminescence

    Science.gov (United States)

    Yan, Neng; Zhu, Zhenli; He, Dong; Jin, Lanlan; Zheng, Hongtao; Hu, Shenghong

    2016-01-01

    The increasing use of metal-based nanoparticle products has raised concerns in particular for the aquatic environment and thus the quantification of such nanomaterials released from products should be determined to assess their environmental risks. In this study, a simple, rapid and sensitive method for the determination of size and mass concentration of gold nanoparticles (AuNPs) in aqueous suspension was established by direct coupling of thin layer chromatography (TLC) with catalyzed luminol-H2O2 chemiluminescence (CL) detection. For this purpose, a moving stage was constructed to scan the chemiluminescence signal from TLC separated AuNPs. The proposed TLC-CL method allows the quantification of differently sized AuNPs (13 nm, 41 nm and 100 nm) contained in a mixture. Various experimental parameters affecting the characterization of AuNPs, such as the concentration of H2O2, the concentration and pH of the luminol solution, and the size of the spectrometer aperture were investigated. Under optimal conditions, the detection limits for AuNP size fractions of 13 nm, 41 nm and 100 nm were 38.4 μg L−1, 35.9 μg L−1 and 39.6 μg L−1, with repeatabilities (RSD, n = 7) of 7.3%, 6.9% and 8.1% respectively for 10 mg L−1 samples. The proposed method was successfully applied to the characterization of AuNP size and concentration in aqueous test samples. PMID:27080702

  20. Dehydrogenative Coupling of Primary Alcohols To Form Esters Catalyzed by a Ruthenium N-Heterocyclic Carbene Complex

    DEFF Research Database (Denmark)

    Sølvhøj, Amanda Birgitte; Madsen, Robert

    2011-01-01

    The ruthenium complex [RuCl2(IiPr)(p-cymene)] catalyzes the direct condensation of primary alcohols into esters and lactones with the release of hydrogen gas. The reaction is most effective with linear aliphatic alcohols and 1,4-diols and is believed to proceed with a ruthenium dihydride as the c...

  1. Copper-catalyzed cross-coupling reactions of epoxides with gem-diborylmethane: access to γ-hydroxyl boronic esters.

    Science.gov (United States)

    Ebrahim-Alkhalil, Ahmed; Zhang, Zhen-Qi; Gong, Tian-Jun; Su, Wei; Lu, Xiao-Yu; Xiao, Bin; Fu, Yao

    2016-04-01

    Herein, we describe a novel copper-catalyzed epoxide opening reaction with gem-diborylmethane. Aliphatic, aromatic epoxides as well as aziridines are converted to the corresponding γ-pinacolboronate alcohols or amines in moderate to excellent yields. This new reaction provides beneficial applications for classic epoxide substrates as well as interesting gem-diborylalkane reagents. PMID:26973991

  2. Rh(III)-Catalyzed Oxidative Coupling of Benzoic Acids with Geminal-Substituted Vinyl Acetates: Synthesis of 3-Substituted Isocoumarins.

    Science.gov (United States)

    Zhang, Mingliang; Zhang, Hui-Jun; Han, Tiantian; Ruan, Wenqing; Wen, Ting-Bin

    2015-01-01

    The Rh(III)-catalyzed C-H activation initiated cyclization of benzoic acids with electron-rich geminal-substituted vinyl acetates was described. The reaction was employed to prepare a range of 3-aryl and 3-alkyl substituted isocoumarins selectively. PMID:25436434

  3. Solvent-Controlled, Tunable β-OAc and β-H Elimination in Rh(III)-Catalyzed Allyl Acetate and Aryl Amide Coupling via C-H Activation.

    Science.gov (United States)

    Dai, Huimin; Yu, Chao; Wang, Zihao; Yan, Hong; Lu, Changsheng

    2016-07-15

    The Heck reaction between arenes and allyl acetate has led to cinnamyl derivatives and allyl products depending on the regioselectivity of β-elimination. The regioselectivity can be controlled by the solvent in the Rh(III)-catalyzed arene-allyl acetate coupling via C-H activation: (1) in THF, cinnamyl derivatives via β-H elimination were generated; (2) in MeOH, allyl products via β-OAc elimination were produced. Both routes have advantages such as excellent γ-selectivity toward allyl acetate, good to excellent yields, and broad substrate scope. PMID:27351917

  4. Directing Group in Decarboxylative Cross-Coupling: Copper-Catalyzed Site-Selective C-N Bond Formation from Nonactivated Aliphatic Carboxylic Acids.

    Science.gov (United States)

    Liu, Zhao-Jing; Lu, Xi; Wang, Guan; Li, Lei; Jiang, Wei-Tao; Wang, Yu-Dong; Xiao, Bin; Fu, Yao

    2016-08-01

    Copper-catalyzed directed decarboxylative amination of nonactivated aliphatic carboxylic acids is described. This intramolecular C-N bond formation reaction provides efficient access to the synthesis of pyrrolidine and piperidine derivatives as well as the modification of complex natural products. Moreover, this reaction presents excellent site-selectivity in the C-N bond formation step through the use of directing group. Our work can be considered as a big step toward controllable radical decarboxylative carbon-heteroatom cross-coupling. PMID:27439145

  5. Regioselective and Stepwise Syntheses of Functionalized BODIPY Dyes through Palladium-Catalyzed Cross-Coupling Reactions and Direct C-H Arylations.

    Science.gov (United States)

    Feng, Zeya; Jiao, Lijuan; Feng, Yuanmei; Yu, Changjiang; Chen, Na; Wei, Yun; Mu, Xiaolong; Hao, Erhong

    2016-08-01

    Regioselective and stepwise syntheses of a series of functionalized BODIPY dyes through palladium-catalyzed cross-coupling reactions and direct C-H arylations have been developed. In particular, this method allows the straightforward synthesis of 2,6-dibromo-3,5-diarylBODIPYs and 2-bromo-3-arylBODIPYs from polybrominated BODIPYs. The X-ray structure of intermediates 5a-c indicated that the palladium was first inserted into the C-Br bonds at 3,5-positions of brominated BODIPYs. The resulting 2,6-dibromo-substituted BODIPYs are potential long wavelength photosensitizers which are not easily accessible using previous methods. PMID:27362954

  6. Copper-Catalyzed Coupling of 2-Siloxy-1-alkenes and Diazocarbonyl Compounds: Approach to Multisubstituted Furans, Pyrroles, and Thiophenes.

    Science.gov (United States)

    Tan, Wei Wen; Yoshikai, Naohiko

    2016-07-01

    We report herein copper(II)-catalyzed cyclization reactions of silyl enol ethers derived from methyl ketones with α-diazo-β-ketoesters or α-diazoketones to afford 2-siloxy-2,3-dihydrofuran derivatives or 2,3,5-trisubstituted furans, respectively, under mild conditions. The former cyclization products serve as versatile 1,4-diketone surrogates, allowing facile preparation of 2,3,5-trisubstituted furans, pyrroles, and thiophenes. PMID:27259097

  7. Nickel-catalyzed cross-coupling reactions of o-carboranyl with aryl iodides: facile synthesis of 1-aryl-o-carboranes and 1,2-diaryl-o-carboranes.

    Science.gov (United States)

    Tang, Cen; Xie, Zuowei

    2015-06-22

    A nickel-catalyzed arylation at the carbon center of o-carborane cages has been developed, thus leading to the preparation of a series of 1-aryl-o-carboranes and 1,2-diaryl-o-carboranes in high yields upon isolation. This method represents the first example of transition metal catalyzed C,C'-diarylation by cross-coupling reactions of o-carboranyl with aryl iodides. PMID:25959849

  8. Silicon-Carbon Bond Formation via Nickel-Catalyzed Cross-Coupling of Silicon Nucleophiles with Unactivated Secondary and Tertiary Alkyl Electrophiles.

    Science.gov (United States)

    Chu, Crystal K; Liang, Yufan; Fu, Gregory C

    2016-05-25

    A wide array of cross-coupling methods for the formation of C-C bonds from unactivated alkyl electrophiles have been described in recent years. In contrast, progress in the development of methods for the construction of C-heteroatom bonds has lagged; for example, there have been no reports of metal-catalyzed cross-couplings of unactivated secondary or tertiary alkyl halides with silicon nucleophiles to form C-Si bonds. In this study, we address this challenge, establishing that a simple, commercially available nickel catalyst (NiBr2·diglyme) can achieve couplings of alkyl bromides with nucleophilic silicon reagents under unusually mild conditions (e.g., -20 °C); especially noteworthy is our ability to employ unactivated tertiary alkyl halides as electrophilic coupling partners, which is still relatively uncommon in the field of cross-coupling chemistry. Stereochemical, relative reactivity, and radical-trap studies are consistent with a homolytic pathway for C-X bond cleavage. PMID:27187869

  9. Ruthenium Catalyzed Diastereo- and Enantioselective Coupling of Propargyl Ethers with Alcohols: Siloxy-Crotylation via Hydride Shift Enabled Conversion of Alkynes to π-Allyls.

    Science.gov (United States)

    Liang, Tao; Zhang, Wandi; Chen, Te-Yu; Nguyen, Khoa D; Krische, Michael J

    2015-10-14

    The first enantioselective carbonyl crotylations through direct use of alkynes as chiral allylmetal equivalents are described. Chiral ruthenium(II) complexes modified by Josiphos (SL-J009-1) catalyze the C-C coupling of TIPS-protected propargyl ether 1a with primary alcohols 2a-2o to form products of carbonyl siloxy-crotylation 3a-3o, which upon silyl deprotection-reduction deliver 1,4-diols 5a-5o with excellent control of regio-, anti-diastereo-, and enantioselectivity. Structurally related propargyl ethers 1b and 1c bearing ethyl- and phenyl-substituents engage in diastereo- and enantioselective coupling, as illustrated in the formation of adducts 5p and 5q, respectively. Selective mono-tosylation of diols 5a, 5c, 5e, 5f, 5k, and 5m is accompanied by spontaneous cyclization to deliver the trans-2,3-disubstituted furans 6a, 6c, 6e, 6f, 6k, and 6m, respectively. Primary alcohols 2a, 2l, and 2p were converted to the siloxy-crotylation products 3a, 3l, and 3p, which upon silyl deprotection-lactol oxidation were transformed to the trans-4,5-disubstituted γ-butyrolactones 7a, 7l, and 7p. The formation of 7p represents a total synthesis of (+)-trans-whisky lactone. Unlike closely related ruthenium catalyzed alkyne-alcohol C-C couplings, deuterium labeling studies provide clear evidence of a novel 1,2-hydride shift mechanism that converts metal-bound alkynes to π-allyls in the absence of intervening allenes. PMID:26418572

  10. Mechanisms by which reactions catalyzed by chloroplast coupling factor 1 are inhibited: ATP synthesis and ATP-H2O oxygen exchange

    International Nuclear Information System (INIS)

    The ATP-H2O back-exchange reaction catalyzed by membrane-bound chloroplast coupling factor 1 (CF1) in the light is known to be extensive; each reacting ATP molecule nearly equilibrates its gamma-PO2 oxygens with H2O before it dissociates from the enzyme. Pi, ASi, ADP, and GDP, alternate substrates of photophosphorylation, each inhibit the exchange reaction. At all concentrations of these substrate/inhibitor molecules tested, the high extent of exchange per molecule of ATP that reacts remains the same, while the number of ATP molecules experiencing exchange decreases. Thus, these inhibitors appear to act in a competitive-type manner, decreasing ATP turnover, as opposed to modulating the rate constants responsible for the partitioning of E X ATP during the exchange reaction. This is consistent with the identity of CF1 catalytic sites for ATP-H2O back-exchange and ATP synthesis. The extent of ATP-H2O forward oxygen exchange, which occurs during net ATP synthesis prior to product dissociation, is unaffected by uncouplers, whether catalyzed by native CF1 (ATPase latent) or the dithiothreitol/light-activated ATPase form

  11. Concise Synthesis of a Pateamine A Analogue with In Vivo Anticancer Activity Based on an Iron-Catalyzed Pyrone Ring Opening/Cross-Coupling.

    Science.gov (United States)

    Zhuo, Chun-Xiang; Fürstner, Alois

    2016-05-10

    The marine macrolide pateamine A and its non-natural sibling DMDA-Pat A are potent translation inhibitors targeting the eukaryotic initiation factor 4A (eIF4A), an enzyme with RNA helicase activity. Although essential for every living cell, this protein target seems "drugable" since DMDA-Pat A has previously been shown to exhibit remarkable in vivo activity against two different melanoma mouse models. The novel entry into this promising compound presented herein is shorter and significantly more productive than the literature route. Key to success was the masking of the signature Z,E-configured dienoate subunit of DMDA-Pat A in the form of a 2-pyrone ring, which was best crafted by a gold-catalyzed cyclization. While the robustness of the heterocycle facilitated the entire assembly stage, the highly isomerization-prone seco-Z,E-dienoic acid could be unlocked in due time for macrolactonization by an unconventional iron-catalyzed ring opening/cross coupling. Moreover, the crystal structure analysis of an advanced intermediate gave first insights into the conformation of the macrodilactone framework of the pateamine family, which is thought to be critical for eliciting the desired biological response. PMID:27061139

  12. Nickel-Catalyzed Suzuki-Miyaura Cross-Coupling in a Green Alcohol Solvent for an Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Hie, Liana; Chang, Jonah J.; Garg, Neil K.

    2015-01-01

    A modern undergraduate organic chemistry laboratory experiment involving the Suzuki-Miyaura coupling is reported. Although Suzuki-Miyaura couplings typically employ palladium catalysts in environmentally harmful solvents, this experiment features the use of inexpensive nickel catalysis, in addition to a "green" alcohol solvent. The…

  13. Pd-catalyzed Suzuki coupling reaction of chloroalkylidene-β-lactones with LB-Phos as the ligand.

    Science.gov (United States)

    Li, Pengbin; Lü, Bo; Fu, Chunling; Ma, Shengming

    2013-01-01

    In this paper, LB-Phos·HBF(4) salt has been applied for the Pd-catalysed Suzuki coupling reactions of optically active (Z)-α-choroalkylidene-β-lactones. Aryl, vinyl, alkyl and heteroaromatic boronic acids may be coupled with optically active β-lactones affording corresponding optically active products highly selectively and efficiently. PMID:23060006

  14. Rapid Access to 2,2'-Bithiazole-Based Copolymers via Sequential Palladium-Catalyzed C-H/C-X and C-H/C-H Coupling Reactions.

    Science.gov (United States)

    Guo, Qiang; Jiang, Ruyong; Wu, Di; You, Jingsong

    2016-05-01

    A rapid access to 2,2'-bithiazole-based copolymers has been developed on the basis of the sequential palladium-catalyzed CH/CX and CH/CH coupling reactions. To assemble a "copolymer" through homopolymerization, a type of symmetric A-B-A-type building block is designed as the monomer and prepared via the regioselective C5H arylation of thiazole. A PdCl2 /CuCl-cocatalyzed oxidative CH/CH homopolymerization has been established to afford the 2,2'-bithiazole-based copolymers with high Mn (up to 69400). The current protocol features atom- and step-economy and exhibits a potential in the highly efficient construction of conjugated copolymers. PMID:27000723

  15. Palladium-Catalyzed Heck Coupling Reaction of Aryl Bromides in Aqueous Media Using Tetrahydropyrimidinium Salts as Carbene Ligands

    Directory of Open Access Journals (Sweden)

    İsmail Özdemir

    2010-01-01

    Full Text Available An efficient and stereoselective catalytic system for the Heck cross coupling reaction using novel 1,3-dialkyl-3,4,5,6-tetrahydropyrimidinium salts (1, LHX and Pd(OAc2 loading has been reported. The palladium complexes derived from the salts 1a-f prepared in situ exhibit good catalytic activity in the Heck coupling reaction of aryl bromides under mild conditions.

  16. Nickel-Catalyzed Suzuki–Miyaura Cross-Coupling in a Green Alcohol Solvent for an Undergraduate Organic Chemistry Laboratory

    OpenAIRE

    Hie, Liana; Chang, Jonah J.; Garg, Neil K.

    2014-01-01

    A modern undergraduate organic chemistry laboratory experiment involving the Suzuki–Miyaura coupling is reported. Although Suzuki–Miyaura couplings typically employ palladium catalysts in environmentally harmful solvents, this experiment features the use of inexpensive nickel catalysis, in addition to a “green” alcohol solvent. The experiment employs heterocyclic substrates, which are important pharmaceutical building blocks. Thus, this laboratory procedure exposes students to a variety of co...

  17. Construction of quaternary stereogenic carbon centers through copper-catalyzed enantioselective allylic cross-coupling with alkylboranes.

    Science.gov (United States)

    Hojoh, Kentaro; Shido, Yoshinori; Ohmiya, Hirohisa; Sawamura, Masaya

    2014-05-01

    A combination of an in situ generated chiral Cu(I) /DTBM-MeO-BIPHEP catalyst system and EtOK enabled the enantioselective SN 2'-type allylic cross-coupling between alkylborane reagents and γ,γ-disubstituted primary allyl chlorides with enantiocontrol at a useful level. The reaction generates a stereogenic quaternary carbon center having three sp(3) -alkyl groups and a vinyl group. This protocol allowed the use of terminal alkenes as nucleophile precursors, thus representing a formal reductive allylic cross-coupling of terminal alkenes. A reaction pathway involving addition/elimination of a neutral alkylcopper(I) species with the allyl chloride substrate is proposed. PMID:24668885

  18. Microwave-assisted heterogeneous cross-coupling reactions catalyzed by nickel-in-charcoal (Ni/C).

    Science.gov (United States)

    Lipshutz, Bruce H; Frieman, Bryan A; Lee, Ching-Tien; Lower, Asher; Nihan, Danielle M; Taft, Benjamin R

    2006-09-18

    A study involving the relatively rare combination of heterogeneous catalysis conducted under microwave conditions is presented. Carbon-carbon bond formation, including Negishi and Suzuki couplings, can be quickly effected with aryl chloride partners by using a base metal (nickel) adsorbed in the pores of activated charcoal. Aminations were also studied, along with cross-couplings of vinyl alanes with benzylic chlorides as a means to stereodefined allylated aromatics. Reaction times for all these processes are typically reduced from several hours to minutes in a microwave reactor. PMID:17441078

  19. Synthesis of dienyl ketones via palladium(II)-catalyzed direct cross-coupling reactions between simple alkenes and vinyl ketones: application to the synthesis of vitamin A1 and bornelone.

    Science.gov (United States)

    Zhang, Xiang; Wang, Min; Zhang, Ming-Xin; Xu, Yun-He; Loh, Teck-Peng

    2013-11-01

    An efficient and general method for the synthesis of conjugated dienyl ketones via palladium(II) acetate catalyzed direct cross-coupling between simple alkenes and vinyl ketones is reported. This method has been successfully applied for the synthesis of Vitamin A1 and bornelone. PMID:24131401

  20. Pd(II)-Catalyzed Cross-Coupling of C(sp2)–H Bonds and Alkyl-, Aryl- and Vinyl-Boron Reagents via Pd(II)/Pd(0) Catalysis

    OpenAIRE

    Wasa, Masayuki; Chan, Kelvin S. L.; Yu, Jin-Quan

    2011-01-01

    Pd(II)-catalyzed cross-coupling of ortho-C–H bonds in benzoic acid and phenylacetic acid amides with alkyl-, aryl- and vinyl-boron reagents have been achieved via Pd(II)/Pd(0) catalysis, demonstrating the unprecedented versatility of C–H activation reactions.

  1. Construction of Substituted Benzenes via Pd-Catalyzed Cross-Coupling/Cyclization Reaction of Vinyl Halides and Terminal Alkynes.

    Science.gov (United States)

    Xie, Meihua; Wang, Shengke; Wang, Jun; Fang, Kuang; Liu, Changqing; Zha, Chao; Jia, Jing

    2016-04-15

    A tandem Sonogashira coupling/cyclization/aromatization sequence of β-halo vinyl sulfones/ketones with terminal alkynes has been developed for the construction of benzene rings. Polysubstituted functionalized benzenes containing a sulfonyl or an acyl group could be obtained in up to 95% yield. PMID:27015420

  2. Diastereo- and Enantioselective Iridium Catalyzed Coupling of Vinyl Aziridines with Alcohols: Site-Selective Modification of Unprotected Diols and Synthesis of Substituted Piperidines.

    Science.gov (United States)

    Wang, Gang; Franke, Jana; Ngo, Chinh Q; Krische, Michael J

    2015-06-24

    The chiral cyclometalated π-allyliridium ortho-C,O-benzoate complex (R)-Ir-VIb derived from [Ir(cod)Cl]2, allyl acetate, 4-cyano-3-nitro-benzoic acid, and (R)-MeO-BIPHEP catalyzes the coupling of N-(p-nitrophenylsulfonyl) protected vinyl aziridine 3a with primary alcohols 1a-1l to furnish branched products of C-C bond formation 4a-4l with good levels of anti-diastereo- and enantioselectivity. In the presence of 2-propanol, but under otherwise identical conditions, vinyl aziridine 3a and aldehydes 2a-2l engage in reductive coupling to furnish an equivalent set of adducts 4a-4l with roughly equivalent levels of anti-diastereo- and enantioselectivity. Using enantiomeric iridium catalysts, vinyl aziridine 3a reacts with unprotected chiral 1,3-diols 1m-1o in a site-selective manner to deliver the diastereomeric products of C-allylation syn-4m, -4n, -4o and anti-4m, -4n, -4o, respectively, with good isolated yields and excellent levels of catalyst-directed diastereoselectivity. These adducts were directly converted to the diastereomeric 2,4,5-trisubstituted piperidines syn-5m, -5n, -5o and anti-5m, -5n, -5o. PMID:26074091

  3. Synthesis and Application of Chiral Spiro Cp Ligands in Rhodium-Catalyzed Asymmetric Oxidative Coupling of Biaryl Compounds with Alkenes.

    Science.gov (United States)

    Zheng, Jun; Cui, Wen-Jun; Zheng, Chao; You, Shu-Li

    2016-04-27

    The vastly increasing application of chiral Cp ligands in asymmetric catalysis results in growing demand for novel chiral Cp ligands. Herein, we report a new class of chiral Cp ligands based on 1,1'-spirobiindane, a privileged scaffold for chiral ligands and catalysts. The corresponding Rh complexes are shown to be excellent catalysts in asymmetric oxidative coupling reactions, providing axially chiral biaryls in 19-97% yields with up to 98:2 er. PMID:27070297

  4. Synthesis of Lithium Boracarbonate Ion Pairs by Copper-Catalyzed Multi-Component Coupling of Carbon Dioxide, Diboron, and Aldehydes.

    Science.gov (United States)

    Carry, Béatrice; Zhang, Liang; Nishiura, Masayoshi; Hou, Zhaomin

    2016-05-17

    The catalytic selective multi-component coupling of CO2 , bis(pinacolato)diboron, LiOtBu, and a wide range of aldehydes has been achieved for the first time by using an NHC-copper catalyst. This transformation has efficiently afforded a series of novel lithium cyclic boracarbonate ion pair compounds in high yields from readily available starting materials. This protocol has not only provided a new catalytic process for the utilization of CO2 , but it has also constituted a novel route for the efficient synthesis of a new class of lithium borate compounds that might be of interest as potential electrolyte candidates for lithium ion batteries. PMID:27061244

  5. An efficient protocol for copper-free palladium-catalyzed Sonogashira cross-coupling in aqueous media at low temperatures

    KAUST Repository

    Marziale, Alexander N.

    2011-11-01

    A thorough study on copper-free Sonogashira cross-couplings in water was carried out using the palla-dacycle, [{Pd(μ-Cl){K2-P,C-P(iPr) 2(OC6H3-2-Ph)}}2] as pre-catalyst with different bases and palladium concentrations. The highly active pre-catalyst imparts good to near quantitative yields using a concentration of 0.25 mol % at 40 °C. This broadly applicable protocol exhibits high tolerance of functional groups and substitution patterns. © 2011 Elsevier Ltd. All rights reserved.

  6. A3-Coupling catalyzed by robust Au nanoparticles covalently bonded to HS-functionalized cellulose nanocrystalline films

    Directory of Open Access Journals (Sweden)

    Jian-Lin Huang

    2013-07-01

    Full Text Available We decorated HS-functionalized cellulose nanocrystallite (CNC films with monodisperse Au nanoparticles (AuNPs to form a novel nanocomposite catalyst AuNPs@HS-CNC. The uniform, fine AuNPs were made by the reduction of HAuCl4 solution with thiol (HS- group-functionalized CNC films. The AuNPs@HS-CNC nanocomposites were examined by X-ray photoelectron spectroscopy (XPS, TEM, ATR-IR and solid-state NMR. Characterizations suggested that the size of the AuNPs was about 2–3 nm and they were evenly distributed onto the surface of CNC films. Furthermore, the unique nanocomposite Au@HS-CNC catalyst displayed high catalytic efficiency in promoting three-component coupling of an aldehyde, an alkyne, and an amine (A3-coupling either in water or without solvent. Most importantly, the catalyst could be used repetitively more than 11 times without significant deactivation. Our strategy also promotes the use of naturally renewable cellulose to prepare reusable nanocomposite catalysts for organic synthesis.

  7. Silylesterification of oxidized multi-wall carbon nanotubes by catalyzed dehydrogenative cross-coupling between carboxylic and hydrosilane functions

    Science.gov (United States)

    Seffer, J.-F.; Detriche, S.; Nagy, J. B.; Delhalle, J.; Mekhalif, Z.

    2014-06-01

    Surface modification of oxidized carbon nanotubes (O-CNTs) with silicon based anchoring groups (R-SiR3) is a relatively uncommon approach of the CNTs functionalization. Hydrosilane derivatives constitute an attractive subclass of compounds for silanization reactions on the CNTs surface. In this work, we report on the ZnCl2 catalytically controlled reaction (hydrosilane dehydrogenative cross-coupling, DHCC) of fluorinated hydrosilane probes with the carboxylic functions present on the surface of oxidized multi-wall carbon nanotubes. Carbon nanotubes functionalized with essentially alcohol groups are also used to compare the selectivity of zinc chloride toward carboxylic groups. To assess the efficiency of functionalization, X-ray Photoelectron Spectroscopy is used to determine the qualitative and quantitative composition of the different samples. Solubility tests on the oxidized and silanized MWNTs are also carried out in the framework of the Hansen Solubility Parameters (HSP) theory to apprehend at another scale the effect of DHCC.

  8. Amine-Catalyzed Highly Regioselective and Stereoselective C(sp(2) )-C(sp(2) ) Cross-Coupling of Naphthols with trans-α,β-Unsaturated Aldehydes.

    Science.gov (United States)

    Hu, Yang; Ma, Yueyue; Sun, Rengwei; Yu, Xinhong; Xie, Hexin; Wang, Wei

    2015-09-01

    A metal-free C(sp(2) )-C(sp(2) ) cross-coupling approach to highly congested (E)-α-naphtholylenals from simple naphthols and enals is described. The mild reaction conditions with pyridine hydrobromideperbromide (PHBP) as the bromination reagent in the presence of piperidine or diphenylprolinol trimethylsilyl (TMS) ether as promoters enable the process in good yields and with high chemoselectivity, regioselectivity, and stereoselectivity. The process involves an unprecedented pathway of in situ regioselective 4-bromination of 1-naphthols and the subsequent unusual aromatic nucleophilic substitution of the resulting 4-bromo-1-naphthols with the α-C(sp(2) ) of enals through a Michael-type Friedel-Crafts alkylation-dearomatization followed by a cyclopropanation ring-opening cascade process. The noteworthy features of this strategy are highlighted by the highly efficient creation of a C(sp(2) )-C(sp(2) ) bond from readily available unfunctionalized naphthols and enals catalyzed by non-metal, readily available cyclic secondary amines under mild reaction conditions. PMID:26096893

  9. Cu-catalyzed Fe-driven C(sp)-C(sp) and C(s)p-C(sp2) cross-coupling: an access to 1,3-diynes and 1,3-enynes.

    Science.gov (United States)

    Ahammed, Sabir; Kundu, Debasish; Ranu, Brindaban C

    2014-08-15

    An efficient Csp-Csp cross-coupling of alkynyl bromide and pinacol ester of alkynyl boronic acid catalyzed by CuFe2O4 nanoparticles has been accomplished in dimethyl carbonate to produce unsymmetric 1,3-diynes. This protocol is also extended for the Csp-Csp2 coupling of alkynyl bromide and alkenyl boronic acid to provide conjugated 1,3-enynes. The aliphatic, aromatic, and heteroaromatic alkynes couple with various substituted alkynyl/alkenyl boronates/boronic acids by this procedure to furnish a library of 1,3-diynes and enynes in high yields. The catalyst was easily separated by an external magnet and recycled 10 times. PMID:25046329

  10. Rhodium(III)-Catalyzed Directed ortho-C-H Bond Functionalization of Aromatic Ketazines via C-S and C-C Coupling.

    Science.gov (United States)

    Wen, Jing; Wu, An; Wang, Mingyang; Zhu, Jin

    2015-11-01

    Described herein is a convenient and efficient method for sulfuration and olefination of aromatic ketazines via rhodium-catalyzed oxidative C-H bond activation. A range of substituted substrates are supported, and a possible mechanism is proposed according to experimental results of kinetic isotopic effect, reversibility studies, and catalysis of rhodacycle intermediate c1. PMID:26417874

  11. Conjugate addition vs Heck reaction: a theoretical study on competitive coupling catalyzed by isoelectronic metal (Pd(II) and Rh(I)).

    Science.gov (United States)

    Peng, Qian; Yan, Hong; Zhang, Xinhao; Wu, Yun-Dong

    2012-09-01

    Density functional theory studies have been carried out to investigate the mechanism of the Pd(II)(bpy)- and Rh(I)(bpy)-catalyzed conjugate additions and their competitive Heck reactions involving α,β-unsaturated carbonyl compounds. The critical steps of the mechanism are insertion and termination. The insertion step favors 1,2-addition of the vinyl-coordinated species to generate a stable C-bound enolate intermediate, which then may isomerize to either an oxa-π-allyl species or an O-bound enolate. The termination step involves a competition between β-hydride elimination, leading to a Heck reaction product, and protonolysis reaction that gives a conjugate addition product. These two pathways are competitive in the Pd(II)-catalyzed reaction, while a preference for protonolysis has been found in the Rh(I)-catalyzed reaction. The calculations are in good agreement with the experimental observations. The potential energy surface and the rate-determining step of the β-hydride elimination are similar for both Pd(II)- and Rh(I)-catalyzed processes. The rate-determining steps of the Pd(II)- and Rh(I)-catalyzed protonolysis are different. Introduction of an N- or P-ligand significantly stabilizes the protonolysis transition state via the O-bound enolate or oxa-π-allyl complex intermediate, resulting in a reduced free energy of activation. However, the barrier of the β-hydride elimination is less sensitive to ligands. For the Rh(I)-catalyzed reaction, protonolysis is calculated to be more favorable than the β-hydride elimination for all investigated N and P ligands due to the significant ligand stabilization to the protonolysis transition state. For the Pd(II)-catalyzed reaction, the complex with monodentate pyridine ligands prefers the Heck-type product through β-hydride elimination, while the complex with bidentate N and P ligands favors the protonolysis. The theoretical finding suggests the possibility to control the selectivity between the conjugate addition and

  12. Palladium-Catalyzed Cross-Coupling Reaction of Organoboron Compounds with Carboxylic Derivatives%钯催化的有机硼化物与羧酸衍生物的交叉偶联反应

    Institute of Scientific and Technical Information of China (English)

    杨军; 邓敏智; 于涛

    2013-01-01

    钯催化的交叉偶联反应是构建C—C键的常用方法,近年来,钯催化的有机硼化物与羧酸衍生物的交叉偶联反应已成为偶联反应研究中的热点.本文综述了最近十几年多种有机硼化物与酰氯、酸酐、羧酸、氯甲酸衍生物、羧酸活性酯、羧酸硫酯的交叉偶联反应研究进展,并对该反应在有机合成中的应用进行了讨论.%Palladium-catalyzed cross-coupling reaction has emerged as an important strategy to the formation of C-C bond. Recently, palladium-catalyzed cross-coupling reaction between organoboron compounds and carboxylic derivatives has become a hotspot of organic chemistry. In this paper, recent researches of organoboron compounds with acyl chlorides, acid anhydrides, carboxylic acids, chloroformic derivatives, carboxylic esters and thiol esters in Suzuki cross-coupling are summarized, and the examples of these reactions in synthesis are also discussed.

  13. Reações de acoplamento cruzado de organossilanos catalisadas por paládio: aspectos históricos, sintéticos e mecanísticos Palladium catalyzed cross coupling reactions of organosilicon compounds: historical, synthetic and mechanistic aspects

    Directory of Open Access Journals (Sweden)

    Róbson R. Teixeira

    2007-01-01

    Full Text Available The development of the palladium catalyzed cross-coupling reactions employing organosilicon compounds is described. Important synthetic methods utilized to prepare organosilicons and different types of cross-coupling reactions involving these compounds are presented. Mechanistic aspects are also discussed.

  14. Palladium-Catalyzed Carbonylation and Arylation Reactions

    OpenAIRE

    Sävmarker, Jonas

    2012-01-01

    Palladium-catalyzed reactions have found widespread use in contemporary organic chemistry due to their impressive range of functional group tolerance and high chemo- and regioselectivity. The pioneering contributions to the development of the Pd-catalyzed C-C bond forming cross-coupling reaction were rewarded with the Nobel Prize in Chemistry in 2010. Today, this is a rapidly growing field, and the development of novel methods, as well as the theoretical understanding of the various processes...

  15. Hydroxymethylations of aryl halides by Pd-catalyzed cross-couplings with (benzoyloxy)methylzinc iodide - the scope and limitations of the reaction

    Czech Academy of Sciences Publication Activity Database

    Hasník, Zbyněk; Šilhár, Peter; Hocek, Michal

    -, č. 4 (2008), s. 543-546. ISSN 0936-5214 R&D Projects: GA MŠk 1M0508; GA AV ČR 1QS400550501 Institutional research plan: CEZ:AV0Z40550506 Keywords : cross-coupling reactions * hydroxymethylations * organozinc reagents Subject RIV: CC - Organic Chemistry Impact factor: 2.659, year: 2008

  16. 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...

  17. The Oxidative Coupling of 2,6-Xylenol Catalyzed by Polymeric Complexes of Copper, 2. Physicochemical Study on Copper(II) Complexes of Partially Dimethylaminomethylated Polystyrene

    NARCIS (Netherlands)

    Schouten, Arend Jan; Wiedijk, Dick; Challa, Ger; Borkent, J.

    1977-01-01

    The polymeric catalyst formed by complexation of copper(II) chloride and partially dimethylaminomethylated polystyrene was investigated to explain its behaviour in the oxidative coupling of 2,6-xylenol. Viscometric studies indicated that at low polymer concentrations coordination of tertiary amine g

  18. Label-free and enzyme-free colorimetric detection of microRNA by catalyzed hairpin assembly coupled with hybridization chain reaction.

    Science.gov (United States)

    Wu, Hao; Liu, Yaling; Wang, Hongyong; Wu, Jun; Zhu, Feifan; Zou, Pei

    2016-07-15

    In this study, a simple, label-free, and enzyme-free colorimetric biosensor has been developed for amplified detection of let-7a microRNA (miRNA) on the basis of dual signal amplification strategy. The sensing system mainly consists of four unlabeled hairpin probes termed H1, H2, H3, and H4. Upon sensing of the target miRNA, hairpin H1 is opened. Then hairpin H2 hybridizes with H1 forming H1-H2 duplex and frees the target miRNA that can be recycled to trigger another reaction cycle. In addition, the newly formed H1-H2 duplex hybridizes with hairpin H3, and this triggers the autonomous cross-opening of the two hairpins H3 and H4 through hybridization chain reaction. During this process, numerous split G-quadruplex structures are generated and further associate with cofactor hemin to form massive peroxidase-mimicking DNAzymes. The resulting DNAzymes catalyze the H2O2-mediated oxidation of colorless 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(2-)) to the green-colored ABTS(•-), inducing a remarkably amplified colorimetric signal. This newly developed sensing system exhibits high sensitivity toward miRNA with a detection limit of 7.4fM and a large dynamic range of 6 orders of magnitude from 10fM to 10nM. Furthermore, it exhibits a good performance to discriminate single-base difference among the miRNA family members and holds a great potential for early diagnosis in gene-related diseases. PMID:26985582

  19. Pd-catalyzed Suzuki-Miyaura coupling reaction in the synthesis of 5-aryl-1-[2-(phosphonomethoxy)ethyl]uracils as potential multisubstrate inhibitors of thymidine phosphorylase

    Czech Academy of Sciences Publication Activity Database

    Pomeisl, Karel; Holý, Antonín; Pohl, Radek

    2007-01-01

    Roč. 48, č. 17 (2007), s. 3065-3067. ISSN 0040-4039 R&D Projects: GA MŠk 1M0508 Grant ostatní: Descartes Prize(XE) HPAW-CT-2002-9001 Institutional research plan: CEZ:AV0Z40550506 Keywords : acyclic nucleoside phosphonates * thymidine phosphorylase * Suzuki coupling * pyrimidine Subject RIV: CC - Organic Chemistry Impact factor: 2.615, year: 2007

  20. Pd-catalyzed Suzuki-Miyaura coupling reaction in the synthesis of 5-aryl substituted pyrimidine acyclic nucleoside phosphonates as potential multisubstrate inhibitors of thymidine phosphorylase

    Czech Academy of Sciences Publication Activity Database

    Pomeisl, Karel; Holý, Antonín; Pohl, Radek

    Dublin : University College Dublin, 2007. s. 329. [European Symposium on Organic Chemistry /15./. 08.07.2007-13.07.2007, Dublin] R&D Projects: GA MŠk 1M0508 Grant ostatní: Descartes Prize(XE) HPAW-CT-2002-9001 Institutional research plan: CEZ:AV0Z40550506 Keywords : acyclic nucleoside phosphonates * thymidine phosphorylase * Suzuki coupling Subject RIV: CC - Organic Chemistry

  1. C(sp2)–C(sp2) cross coupling reaction catalyzed by a palladacycle phosphine complex: A simple and sustainable protocol in aqueous media

    Indian Academy of Sciences (India)

    Seyyed Javad Sabounchei; Marjan Hosseinzadeh

    2015-11-01

    The Heck reactions of various aryl halides with olefins using {[Ph2PCH2PPh2CH=C(O)(C10H7)] PdCl2} as efficient catalyst has been investigated. The mononuclear palladacycle complex showed excellent activity in aqueous phase including the C(sp2)–C(sp2) cross coupling reactions. The advantages of the protocol are high yields, short reaction time, a cleaner reaction profile and notable simplicity.

  2. Coupled evolution of BrOx-ClOx-HOx-NOx chemistry during bromine-catalyzed ozone depletion events in the arctic boundary layer

    OpenAIRE

    M. J. Evans; Jacob, Daniel James; Atlas, E.; Cantrell, C; Eisele, F.; Flocke, F.; Fried, A.; Mauldin, R; Ridley, B.; Wert, B; Talbot, R.; Blake, D.; B. Heikes; Snow, J.; Walega, J

    2003-01-01

    Extensive chemical characterization of ozone (O3) depletion events in the Arctic boundary layer during the TOPSE aircraft mission in March–May 2000 enables analysis of the coupled chemical evolution of bromine (BrOx), chlorine (ClOx), hydrogen oxide (HOx) and nitrogen oxide (NOx) radicals during these events. We project the TOPSE observations onto an O3 chemical coordinate to construct a chronology of radical chemistry during O3 depletion events, and we compare this chronology to results from...

  3. Palladium-phosphinous acid complexes catalyzed Suzuki cross-coupling reaction of heteroaryl bromides with phenylboronic acid in water/alcoholic solvents

    Institute of Scientific and Technical Information of China (English)

    Ben Li; Cuiping Wang; Guang Chen; Zhiqiang Zhang

    2013-01-01

    Highly active,air-stable and water-soluble palladium-phosphinous acid complexes have been applied to Suzuki cross-coupling reaction of heteroaryl bromides under mild conditions in water/alcoholic solvents.Suzuki cross-coupling reaction of heteroaryl bromides with phenylboronic acid occurred efficiently using palladium phosphinous acid complexes (POPd) and phase transfer catalyst (tetrabutylammonium bromide and polyethylene glycol) in water/ethanol mixture,water/propanol mixture and neat water respectively,the corresponding yields of cross-coupling heteroaryl-aryls were satisfied.The tert-butyl substituted ligand di-tert-butylphosphino in combination with POPd was found to be more active than the same family derived catalysts dipalladium complexes POPdl and POPd2,and other two kinds of Pd-catalysts Pd(PPh3)4 and Pd2(dba)3.The mechanism of Suzuki cross-coupling reaction between heteroaryl bromides and phenylboronic acid in water was proposed with respect to the key role of phase transfer catalyst on the transmetallation step.Compared with other solid phase transfer catalysts,TBAB was tested as the ideal one.The alkalinity of base and the molar proportion between POPd and TBAB were investigated in water and alcoholic solvents.Notably,in the presence of TBAB adding alcoholic solvents into water enhanced the yields of target products.However in terms of the liquid phase transfer catalyst of PEGs,mixing water into PEGs could slightly decrease the yields with respect to the water free PEGs bulk phase,which was probably due to the homogenous liquid conditions in pure PEGs and weak interactions between PEGs and heteroaryl bromide molecules in water depending on their molecular chain lengths.

  4. Highly efficient palladium-catalyzed hydrostannation of ethyl ethynyl ether

    OpenAIRE

    Andrews, Ian P.; Kwon, Ohyun

    2008-01-01

    The palladium-catalyzed hydrostannation of acetylenes is widely exploited in organic synthesis as a means of forming vinyl stannanes for use in palladium-catalyzed cross-coupling reactions. Application of this methodology to ethyl ethynyl ether results in an enol ether that is challenging to isolate from the crude reaction mixture because of incompatibility with typical silica gel chromatography. Reported here is a highly efficient procedure for the palladium-catalyzed hydrostannation of ethy...

  5. Palladium-catalyzed double cross-coupling of E-vinylic dibromides with PhZnCl and the synthesis of tamoxifen

    Energy Technology Data Exchange (ETDEWEB)

    Pilli, Ronaldo A.; Robello, Luis Gustavo [Universidade Estadual de Campinas, SP (Brazil). Inst. de Quimica]. E-mail: pilli@iqm.unicamp.br

    2004-12-01

    (E)-1,2-vinylic dibromides 11a-f were stereoselectively prepared via bromination of acetylenic compounds with pyridinium tribromide in MeOH/CCl{sub 4} at low temperature and double cross-coupled with PhZnCl under Pd(0) catalysis (Negishi protocol) to afford tri- and tetrasubstituted olefins 14a-e. Tamoxifen, a selective estrogen receptor modulator clinically prescribed in breast cancer therapy, was prepared in 7 steps and 30% overall yield from 4-iodophenol (3) as a 2.3:1 mixture of (Z)- and (E)-isomers. (author)

  6. Palladium-catalyzed C(sp(3))-H Arylation of N-Boc benzylalkylamines via a deprotonative cross-coupling process.

    Science.gov (United States)

    Hussain, Nusrah; Kim, Byeong-Seon; Walsh, Patrick J

    2015-07-27

    Diarylmethylamines are key intermediates and products in the pharmaceutical industry. Herein we disclose a novel method toward the synthesis of these important compounds via CH functionalization. Presented is a reversible deprotonation of N-Boc benzylalkylamines at the benzylic CH with in situ arylation by a NiXantPhos-based palladium catalyst (50-93 % yield, 29 examples). The method is also successful with N-Boc-tetrahydroisoquinolines. The advantages of this method are it avoids strong bases, low temperatures, and the need to transmetallate to main group metals for the coupling. PMID:26129922

  7. Hemin/G-quadruplex-based DNAzyme concatamers for in situ amplified impedimetric sensing of copper(II) ion coupling with DNAzyme-catalyzed precipitation strategy.

    Science.gov (United States)

    Xu, Mingdi; Gao, Zhuangqiang; Wei, Qiaohua; Chen, Guonan; Tang, Dianping

    2015-12-15

    A new signal-amplification strategy based on copper(II) (Cu(2+))-dependent DNAzyme was developed for sensitive impedimetric biosensing of Cu(2+) in aqueous solution by coupling with target-induced formation of hemin/G-quadruplex-based DNAzyme and enzymatic catalytic precipitation technique. Initially, the target analyte cleaved the Cu(2+)-specific DNAzyme to generate an initiator strand on the sensor. Thereafter, the initiator strand underwent an unbiased strand-displacement reaction between hairpin probes in turn to construct a nicked double-helix, accompanying the formation of hemin/G-quadruplex DNAzyme on the long duplex DNA. The newly formed DNAzyme could oxidize the 4-chloro-1-naphthol (4-CN) to produce an insoluble precipitation on the sensor, thus resulting in a local alteration of the conductivity. Under the optimal conditions, the resistance increased with the increasing Cu(2+) in the sample, and exhibited a wide dynamic working range from 0.1 pM to 5.0 nM with a detection limit of 60 fM. The methodology also displayed a high selectivity for Cu(2+) relative to other potentially interfering ions owing to the highly specific Cu(2+)-dependent DNAzyme, and was applicable for monitoring Cu(2+) in real river samples. Thus, our strategy has a good potential in the environment surveys. PMID:26093122

  8. Muon Catalyzed Fusion

    Science.gov (United States)

    Armour, Edward A.G.

    2007-01-01

    Muon catalyzed fusion is a process in which a negatively charged muon combines with two nuclei of isotopes of hydrogen, e.g, a proton and a deuteron or a deuteron and a triton, to form a muonic molecular ion in which the binding is so tight that nuclear fusion occurs. The muon is normally released after fusion has taken place and so can catalyze further fusions. As the muon has a mean lifetime of 2.2 microseconds, this is the maximum period over which a muon can participate in this process. This article gives an outline of the history of muon catalyzed fusion from 1947, when it was first realised that such a process might occur, to the present day. It includes a description of the contribution that Drachrnan has made to the theory of muon catalyzed fusion and the influence this has had on the author's research.

  9. Gold-catalyzed naphthalene functionalization

    Directory of Open Access Journals (Sweden)

    Iván Rivilla

    2011-05-01

    Full Text Available The complexes IPrMCl (IPr = 1,3-bis(diisopropylphenylimidazol-2-ylidene, M = Cu, 1a; M = Au, 1b, in the presence of one equiv of NaBAr'4 (Ar' = 3,5-bis(trifluoromethylphenyl, catalyze the transfer of carbene groups: C(RCO2Et (R = H, Me from N2C(RCO2Et to afford products that depend on the nature of the metal center. The copper-based catalyst yields exclusively a cycloheptatriene derivative from the Buchner reaction, whereas the gold analog affords a mixture of products derived either from the formal insertion of the carbene unit into the aromatic C–H bond or from its addition to a double bond. In addition, no byproducts derived from carbene coupling were observed.

  10. Palladium-catalyzed oxidative carbonylation reactions.

    Science.gov (United States)

    Wu, Xiao-Feng; Neumann, Helfried; Beller, Matthias

    2013-02-01

    Palladium-catalyzed coupling reactions have become a powerful tool for advanced organic synthesis. This type of reaction is of significant value for the preparation of pharmaceuticals, agrochemicals, as well as advanced materials. Both, academic as well as industrial laboratories continuously investigate new applications of the different methodologies. Clearly, this area constitutes one of the major topics in homogeneous catalysis and organic synthesis. Among the different palladium-catalyzed coupling reactions, several carbonylations have been developed and widely used in organic syntheses and are even applied in the pharmaceutical industry on ton-scale. Furthermore, methodologies such as the carbonylative Suzuki and Sonogashira reactions allow for the preparation of interesting building blocks, which can be easily refined further on. Although carbonylative coupling reactions of aryl halides have been well established, palladium-catalyzed oxidative carbonylation reactions are also interesting. Compared with the reactions of aryl halides, oxidative carbonylation reactions offer an interesting pathway. The oxidative addition step could be potentially avoided in oxidative reactions, but only few reviews exist in this area. In this Minireview, we summarize the recent development in the oxidative carbonylation reactions. PMID:23307763

  11. Tritium catalyzed deuterium tokamaks

    International Nuclear Information System (INIS)

    A preliminary assessment of the promise of the Tritium Catalyzed Deuterium (TCD) tokamak power reactors relative to that of deuterium-tritium (D-T) and catalyzed deuterium (Cat-D) tokamaks is undertaken. The TCD mode of operation is arrived at by converting the 3He from the D(D,n)3He reaction into tritium, by neutron capture in the blanket; the tritium thus produced is fed into the plasma. There are three main parts to the assessment: blanket study, reactor design and economic analysis and an assessment of the prospects for improvements in the performance of TCD reactors (and in the promise of the TCD mode of operation, in general)

  12. Kinase-Catalyzed Biotinylation

    OpenAIRE

    Senevirathne, Chamara; Green, Keith D.; Pflum, Mary Kay H.

    2012-01-01

    Kinase-catalyzed protein phosphorylation plays an essential role in a variety of biological processes. Methods to detect phosphoproteins and phosphopeptides in cellular mixtures will aid in cell biological and signaling research. Our laboratory recently discovered the utility of γ-modified ATP analogues as tools for studying phosphorylation. Specifically, ATP-biotin can be used for labeling and visualizing phosphoproteins from cell lysates. Because the biotin tag is suitable for protein detec...

  13. Hydrogen evolution catalyzed by cobaloximes.

    Science.gov (United States)

    Dempsey, Jillian L; Brunschwig, Bruce S; Winkler, Jay R; Gray, Harry B

    2009-12-21

    Natural photosynthesis uses sunlight to drive the conversion of energy-poor molecules (H(2)O, CO(2)) to energy-rich ones (O(2), (CH(2)O)(n)). Scientists are working hard to develop efficient artificial photosynthetic systems toward the "Holy Grail" of solar-driven water splitting. High on the list of challenges is the discovery of molecules that efficiently catalyze the reduction of protons to H(2). In this Account, we report on one promising class of molecules: cobalt complexes with diglyoxime ligands (cobaloximes). Chemical, electrochemical, and photochemical methods all have been utilized to explore proton reduction catalysis by cobaloxime complexes. Reduction of a Co(II)-diglyoxime generates a Co(I) species that reacts with a proton source to produce a Co(III)-hydride. Then, in a homolytic pathway, two Co(III)-hydrides react in a bimolecular step to eliminate H(2). Alternatively, in a heterolytic pathway, protonation of the Co(III)-hydride produces H(2) and Co(III). A thermodynamic analysis of H(2) evolution pathways sheds new light on the barriers and driving forces of the elementary reaction steps involved in proton reduction by Co(I)-diglyoximes. In combination with experimental results, this analysis shows that the barriers to H(2) evolution along the heterolytic pathway are, in most cases, substantially greater than those of the homolytic route. In particular, a formidable barrier is associated with Co(III)-diglyoxime formation along the heterolytic pathway. Our investigations of cobaloxime-catalyzed H(2) evolution, coupled with the thermodynamic preference for a homolytic route, suggest that the rate-limiting step is associated with formation of the hydride. An efficient water splitting device may require the tethering of catalysts to an electrode surface in a fashion that does not inhibit association of Co(III)-hydrides. PMID:19928840

  14. Copper-catalyzed arylation of alkyl halides with arylaluminum reagents

    Science.gov (United States)

    Shrestha, Bijay

    2015-01-01

    Summary We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N’,N’-tetramethyl-o-phenylenediamine (NN-1) as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields. PMID:26734088

  15. Copper-catalyzed arylation of alkyl halides with arylaluminum reagents

    Directory of Open Access Journals (Sweden)

    Bijay Shrestha

    2015-12-01

    Full Text Available We report a Cu-catalyzed coupling between triarylaluminum reagents and alkyl halides to form arylalkanes. The reaction proceeds in the presence of N,N,N’,N’-tetramethyl-o-phenylenediamine (NN-1 as a ligand in combination with CuI as a catalyst. This catalyst system enables the coupling of primary alkyl iodides and bromides with electron-neutral and electron-rich triarylaluminum reagents and affords the cross-coupled products in good to excellent yields.

  16. Palladium-Catalyzed Environmentally Benign Acylation.

    Science.gov (United States)

    Suchand, Basuli; Satyanarayana, Gedu

    2016-08-01

    Recent trends in research have gained an orientation toward developing efficient strategies using innocuous reagents. The earlier reported transition-metal-catalyzed carbonylations involved either toxic carbon monoxide (CO) gas as carbonylating agent or functional-group-assisted ortho sp(2) C-H activation (i.e., ortho acylation) or carbonylation by activation of the carbonyl group (i.e., via the formation of enamines). Contradicting these methods, here we describe an environmentally benign process, [Pd]-catalyzed direct carbonylation starting from simple and commercially available iodo arenes and aldehydes, for the synthesis of a wide variety of ketones. Moreover, this method comprises direct coupling of iodoarenes with aldehydes without activation of the carbonyl and also without directing group assistance. Significantly, the strategy was successfully applied to the synthesis n-butylphthalide and pitofenone. PMID:27377566

  17. Palladium-Catalyzed Arylation of Fluoroalkylamines

    Science.gov (United States)

    Brusoe, Andrew T.; Hartwig, John F.

    2015-01-01

    We report the synthesis of fluorinated anilines by palladium-catalyzed coupling of fluoroalkylamines with aryl bromides and aryl chlorides. The products of these reactions are valuable because anilines typically require the presence of an electron-withdrawing substituent on nitrogen to suppress aerobic or metabolic oxidation, and the fluoroalkyl groups have steric properties and polarity distinct from those of more common electron-withdrawing amide and sulfonamide units. The fluoroalkylaniline products are unstable under typical conditions for C–N coupling reactions (heat and strong base). However, the reactions conducted with the weaker base KOPh, which has rarely been used in cross-coupling to form C–N bonds, occurred in high yield in the presence of a catalyst derived from commercially available AdBippyPhos and [Pd(allyl)Cl]2. Under these conditions, the reactions occur with low catalyst loadings (<0.50 mol % for most substrates) and tolerate the presence of various functional groups that react with the strong bases that are typically used in Pd-catalyzed C–N cross-coupling reactions of aryl halides. The resting state of the catalyst is the phenoxide complex, (BippyPhosPd(Ar)OPh); due to the electron-withdrawing property of the fluoroalkyl substituent, the turnover-limiting step of the reaction is reductive elimination to form the C–N bond. PMID:26065341

  18. Catalyzed Ceramic Burner Material

    Energy Technology Data Exchange (ETDEWEB)

    Barnes, Amy S., Dr.

    2012-06-29

    Catalyzed combustion offers the advantages of increased fuel efficiency, decreased emissions (both NOx and CO), and an expanded operating range. These performance improvements are related to the ability of the catalyst to stabilize a flame at or within the burner media and to combust fuel at much lower temperatures. This technology has a diverse set of applications in industrial and commercial heating, including boilers for the paper, food and chemical industries. However, wide spread adoption of catalyzed combustion has been limited by the high cost of precious metals needed for the catalyst materials. The primary objective of this project was the development of an innovative catalyzed burner media for commercial and small industrial boiler applications that drastically reduce the unit cost of the catalyzed media without sacrificing the benefits associated with catalyzed combustion. The scope of this program was to identify both the optimum substrate material as well as the best performing catalyst construction to meet or exceed industry standards for durability, cost, energy efficiency, and emissions. It was anticipated that commercial implementation of this technology would result in significant energy savings and reduced emissions. Based on demonstrated achievements, there is a potential to reduce NOx emissions by 40,000 TPY and natural gas consumption by 8.9 TBtu in industries that heavily utilize natural gas for process heating. These industries include food manufacturing, polymer processing, and pulp and paper manufacturing. Initial evaluation of commercial solutions and upcoming EPA regulations suggests that small to midsized boilers in industrial and commercial markets could possibly see the greatest benefit from this technology. While out of scope for the current program, an extension of this technology could also be applied to catalytic oxidation for volatile organic compounds (VOCs). Considerable progress has been made over the course of the grant

  19. Diversity synthesis using the complimentary reactivity of rhodium(II)- and palladium(II)-catalyzed reactions.

    Science.gov (United States)

    Ni, Aiwu; France, Jessica E; Davies, Huw M L

    2006-07-21

    Rhodium(II)-catalyzed reactions of aryldiazoacetates can be conducted in the presence of iodide, triflate, organoboron, and organostannane functionality, resulting in the formation of a variety of cyclopropanes or C-H insertion products with high stereoselectivity. The combination of the rhodium(II)-catalyzed reaction with a subsequent palladium(II)-catalyzed Suzuki coupling offers a novel strategy for diversity synthesis. PMID:16839138

  20. Modern Arylation Methods

    CERN Document Server

    Ackermann, Lutz

    2009-01-01

    Today, arylation methods are belonging to the most important reaction types in organic synthesis. Lutz Ackermann, a young and ambitious professor has gathered a number of top international authors to present the first comprehensive book on the topic. Starting from a historical review, the book covers hot topics like Palladium-catalyzed arylation of N-H and alpha-C-H-acidic Bonds, Copper-catalyzed arylation of N-H and O-H Bonds, direct arylation reactions, carbanion aromatic synthesis, arylation reactions of alkenes, alkynes and much more. This compact source of high quality information is indi

  1. Catalyzing alignment processes

    DEFF Research Database (Denmark)

    Lauridsen, Erik Hagelskjær; Jørgensen, Ulrik

    2004-01-01

    time and in combination with other social processes establish more aligned and standardized environmental performance between countries. However, examples of the introduction of environmental management suggests that EMS’ only plays a minor role in developing the actual environmental objectives......This paper describes how environmental management systems (EMS) spur the circulation of processes that support the constitution of environmental issues as specific environ¬mental objects and objectives. EMS catalyzes alignmentprocesses that produce coherence among the different elements involved...... they are implemented in and how the changing context is reflected in the environmental objectives that are established and prioritised. Our argument is, that the ability of the standard to achieve an impact is dependant on the constitution of ’coherent’ environmental issues in the context, where the management system...

  2. Palladium(0)-catalyzed methylenecyclopropanation of norbornenes with vinyl bromides.

    Science.gov (United States)

    Mao, Jiangang; Bao, Weiliang

    2014-05-16

    Highly strained methylenecyclopropane derivatives have been achieved via a novel and efficient Pd(0)-catalyzed domino reaction. The formal [2 + 1] cycloaddition reaction of vinyl bromides to norbornenes involves a Heck-type coupling and a C(sp(2))-H bond activation. PMID:24784731

  3. 钯催化的交叉偶联反应——2010年诺贝尔化学奖获奖工作介绍%Palladium-Catalyzed Cross-Coupling ReactionsIntroduction of Nobel Prize in Chemistry in 2010

    Institute of Scientific and Technical Information of China (English)

    王乃兴

    2011-01-01

    钯催化的交叉偶联反应是非常实用的合成新方法.文章给出了Heck反应、Negishi反应和Suzuki反应的概念,对其反应机理作了详细的说明,并对其在复杂化合物和天然产物全合成中的应用作了评价.%Palladium-catalyzed cross-coupling reactions provide chemists with a more precise and efficient new methodologies. The concepts of the Heck reaction and Negishi reaction as well as Suzuki reaction are given, the reaction mechanisms are proposed, and applications of these reactions in the total synthesis of natural products are commented.

  4. Scope and Mechanistic Investigations on the Solvent-Controlled Regio- and Stereoselective Formation of Enol Esters from the Ruthenium-Catalyzed Coupling Reaction of Terminal Alkynes and Carboxylic Acids

    OpenAIRE

    Yi, Chae S.; Gao, Ruili

    2009-01-01

    The ruthenium-hydride complex (PCy3)2(CO)RuHCl was found to be a highly effective catalyst for the alkyne-to-carboxylic acid coupling reaction to give synthetically useful enol ester products. Strong solvent effect was observed for the ruthenium catalyst in modulating the activity and selectivity; the coupling reaction in CH2Cl2 led to the regioselective formation of gem-enol ester products, while the stereoselective formation of (Z)-enol esters was obtained in THF. The coupling reaction was ...

  5. TBAHS CATALYZED COUPLING REACTIONS OF ARYL IODIDES AND ARYL BROMIDES WITH THIOLS UNDER SOLVENT FREE CONDITIONS TBAHS katalysierten Kupplungen von Aryliodiden und-Arylbromiden mit Thiolen unter lösungsmittelfreien freien Bedingungen

    Directory of Open Access Journals (Sweden)

    Gajendera Singha, Ajay kumarb , Sakshi Malikc, Preeti Chaudharyd

    2013-04-01

    Full Text Available A recyclable and efficient Tetrabutylammonium hydrogensulfate (TBAHS catalysed coupling reaction of aryl halides (iodide and bromide with aryl and alkyl thiols under solvent-free conditions were developed.

  6. A kinetic and spectroscopic study on the copper catalyzed oxidative coupling polymerization of 2,6-dimethylphenol. X-ray structure of the catalyst precursor tetrakis(N-methylimidazole)bis(nitrato)copper(II)

    NARCIS (Netherlands)

    Baesjou, PJ; Driessen, WL; Challa, G; Reedijk, J

    1996-01-01

    The complex of copper(II) nitrate with N-methylimidazole (Nmiz) ligand has been studied as a catalyst for the oxidative coupling of 2,6-dimethylphenol by means of kinetic and spectroscopic measurements. The order of the reaction in copper is fractional and depends on the N/Cu ratio and the base/Cu r

  7. A broadly applicable NHC-Cu-catalyzed approach for efficient, site-, and enantioselective coupling of readily accessible (pinacolato)alkenylboron compounds to allylic phosphates and applications to natural product synthesis.

    Science.gov (United States)

    Gao, Fang; Carr, James L; Hoveyda, Amir H

    2014-02-01

    A set of protocols for catalytic enantioselective allylic substitution (EAS) reactions that allow for additions of alkenyl units to readily accessible allylic electrophiles is disclosed. Transformations afford 1,4-dienes that contain a tertiary carbon stereogenic site and are promoted by 1.0-5.0 mol % of a copper complex of an N-heterocyclic carbene (NHC). Aryl- as well as alkyl-substituted electrophiles bearing a di- or trisubstituted alkene may be employed. Reactions can involve a variety of robust alkenyl-(pinacolatoboron) [alkenyl-B(pin)] compounds that can be either purchased or prepared by various efficient, site-, and/or stereoselective catalytic reactions, such as cross-metathesis or proto-boryl additions to terminal alkynes. Vinyl-, E-, or Z-disubstituted alkenyl-, 1,1-disubstituted alkenyl-, acyclic, or heterocyclic trisubstituted alkenyl groups may be added in up to >98% yield, >98:2 SN2':SN2, and 99:1 enantiomeric ratio (er). NHC-Cu-catalyzed EAS with alkenyl-B(pin) reagents containing a conjugated carboxylic ester or aldehyde group proceed to provide the desired 1,4-diene products in good yield and with high enantioselectivity despite the presence of a sensitive stereogenic tertiary carbon center that could be considered prone to epimerization. In most instances, the alternative approach of utilizing an alkenylmetal reagent (e.g., an Al-based species) represents an incompatible option. The utility of the approach is illustrated through applications to enantioselective synthesis of natural products such as santolina alcohol, semburin, nyasol, heliespirone A, and heliannuol E. PMID:24467274

  8. 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

    OpenAIRE

    Yi, Chae S.; Lee, Do W.

    2010-01-01

    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.

  9. Cobalt-Catalyzed Enantioselective Vinylation of Activated Ketones and Imines.

    Science.gov (United States)

    Huang, Yuan; Huang, Rui-Zhi; Zhao, Yu

    2016-05-25

    We present here an unprecedented cobalt-catalyzed enantioselective vinylation of α-ketoesters, isatins, and imines to deliver a range of synthetically useful allylic alcohols and amines in high enantiopurity. This method employs commercially available and easy to handle catalysts and reagents and exhibits a high degree of practicality. The efficiency, selectivity, and operational simplicity of this catalytic system coupled with the substrate generality render this method a valuable tool in organic synthesis. PMID:27139596

  10. An efficient synthesis of isocoumarins via a CuI catalyzed cascade reaction process

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    3-Alkyl isocoumarins are provided by CuI/amino acid-catalyzed Sonogashira coupling reaction of o-bromo benzoic acids and terminal alkynes and the subsequent additive cyclization. This cascade process allows synthesis of diverse isocoumarins by varying both coupling partners bearing a wide range of functional groups.

  11. Effect of enzyme dehydration on alcalase-catalyzed dipeptide synthesis in near-anhydrous organic media.

    NARCIS (Netherlands)

    Vossenberg, P.; Beeftink, H.H.; Cohen Stuart, M.A.; Tramper, J.

    2013-01-01

    The effect of enzyme dehydration by molecular sieves on the coupling of phenylalanine amide and the carbamoylmethyl ester of N-protected phenylalanine in near-anhydrous tetrahydrofuran was investigated. This coupling was catalyzed by Alcalase covalently immobilized onto macroporous acrylic beads (Co

  12. Kinetics of Alcalase-catalyzed dipeptide synthesis in near-anhydrous organic media

    NARCIS (Netherlands)

    Vossenberg, P.; Beeftink, H.H.; Cohen Stuart, M.A.; Tramper, J.

    2013-01-01

    The coupling kinetics of phenylalanine amide and the carbamoylmethyl ester of N-protected phenylalanine in near-anhydrous tetrahydrofuran were investigated. This coupling was catalyzed by Alcalase covalently immobilized onto macroporous acrylic beads; these immobilized enzymes were hydrated prior to

  13. Iodine-catalyzed coal liquefaction

    Energy Technology Data Exchange (ETDEWEB)

    Joseph, J.T.; Duffield, J.E.; Davidson, M.G. (Amoco Oil Company, Naperville, IL (USA). Research and Development Dept.)

    Coals of two different ranks were liquefied in high yields using catalytic quantities of elemental iodine or iodine compounds. Iodine monochloride was found to be especially effective for enhancing both coal conversion and product quality. It appears that enhancement in coal conversion is due to the unique ability of iodine to catalyze radical-induced bond scission and hydrogen addition to the coal macromolecule or coal-derived free radicals. The starting iodine can be fully accounted for in the reaction products as both organic-bound and water-soluble forms. Unconverted coal and the heavy product fractions contain the majority of the organic-bound iodine. The results of iodine-catalyzed coal reactions emphasize the need for efficient hydrogen atom transfer along with bond scission to achieve high conversion and product quality. 22 refs., 12 tabs.

  14. Stau-catalyzed Nuclear Fusion

    OpenAIRE

    Hamaguchi, K.; Hatsuda, T.(Theoretical Research Division, Nishina Center, RIKEN, Saitama, 351-0198, Japan); Yanagida, T. T.

    2006-01-01

    We point out that the stau may play a role of a catalyst for nuclear fusions if the stau is a long-lived particle as in the scenario of gravitino dark matter. In this letter, we consider d d fusion under the influence of stau where the fusion is enhanced because of a short distance between the two deuterons. We find that one chain of the d d fusion may release an energy of O(10) GeV per stau. We discuss problems of making the stau-catalyzed nuclear fusion of practical use with the present tec...

  15. Gold-catalyzed naphthalene functionalization

    OpenAIRE

    Iván Rivilla; M. Mar Díaz-Requejo; Pedro J. Pérez

    2011-01-01

    The complexes IPrMCl (IPr = 1,3-bis(diisopropylphenyl)imidazol-2-ylidene, M = Cu, 1a; M = Au, 1b), in the presence of one equiv of NaBAr'4 (Ar' = 3,5-bis(trifluoromethyl)phenyl), catalyze the transfer of carbene groups: C(R)CO2Et (R = H, Me) from N2C(R)CO2Et to afford products that depend on the nature of the metal center. The copper-based catalyst yields exclusively a cycloheptatriene derivative from the Buchner reaction, whereas the gold analog affords a mixture of products derived either f...

  16. Thermodynamics of Enzyme-Catalyzed Reactions Database

    Science.gov (United States)

    SRD 74 Thermodynamics of Enzyme-Catalyzed Reactions Database (Web, free access)   The Thermodynamics of Enzyme-Catalyzed Reactions Database contains thermodynamic data on enzyme-catalyzed reactions that have been recently published in the Journal of Physical and Chemical Reference Data (JPCRD). For each reaction the following information is provided: the reference for the data, the reaction studied, the name of the enzyme used and its Enzyme Commission number, the method of measurement, the data and an evaluation thereof.

  17. Direct activation of allylic alcohols in palladium catalyzed coupling reactions

    OpenAIRE

    Gümrükçü, Y.

    2014-01-01

    The direct use of allylic alcohols in substitution reactions without pre-activation of the hydroxyl-group into a better leaving group or the use of additional stoichiometric in situ activators remains challenging due to the poor leaving group ability of the hydroxyl-group. Hence, it is important to develop new methods to activate (bio-mass derived) allyl-alcohols, which allow ‘green’ chemical processes for a broad substrate range. This may have a considerable impact on the methodology for fin...

  18. Can laccases catalyze bond cleavage in lignin?

    DEFF Research Database (Denmark)

    Munk, Line; Sitarz, Anna Katarzyna; Kalyani, Dayanand;

    2015-01-01

    these enzymes may help degrading lignin, using oxygen as the oxidant. Laccases can catalyze polymerization of lignin, but the question is whether and how laccases can directly catalyze modification of lignin via catalytic bond cleavage. Via a thorough review of the available literature and detailed...

  19. Catalyzed electrolytic plutonium oxide dissolution

    International Nuclear Information System (INIS)

    Catalyzed electrolytic plutonium oxide dissolution (CEPOD) was first demonstrated at Pacific Northwest Laboratory (PNL) in early 1974 in work funded by the Exxon Corporation. The work, aimed at dissolution of Pu-containing residues remaining after the dissolution of spent mixed-oxide reactor fuels, was first publicly disclosed in 1981. The process dissolves PuO2 in an anolyte containing small (catalytic) amounts of elements that form kinetically fast, strongly oxidizing ions. These are continuously regenerated at the anode. Catalysts used, in their oxidized form, include Ag2+, Ce4+, Co3+, and AmO22+. This paper reviews the chemistry involved in CEPOD and the results of its application to the dissolution of the Pu content of a variety of PuO2-containing materials such as off-standard oxide, fuels dissolution residues, incinerator ash, contaminated soils, and other scraps or wastes. Results are presented for both laboratory-scale and plant-scale dissolves

  20. Coupling of Vinyl Aziridines and Isocyanates

    OpenAIRE

    Zhang, Kainan; Chopade, Pramod R.; Louie, Janis

    2008-01-01

    Thermal coupling of vinyl aziridines and phenyl isocyanate was evaluated. Although oxazolidinone products were predominant, some reactions afforded a seven-membered ring heterocycle. When Ni/IMes was employed as a catalyst, a wider array of vinyl aziridines underwent coupling reactions. The Ni catalyzed reactions generally afforded vinyl imidazolidinones as major products.

  1. Palladium-Catalyzed Polyfluorophenylation of Porphyrins with Bis(polyfluorophenylzinc Reagents

    Directory of Open Access Journals (Sweden)

    Toshikatsu Takanami

    2013-10-01

    Full Text Available A facile and efficient method for the synthesis of pentafluorophenyl- and related polyfluorophenyl-substituted porphyrins has been achieved via palladium-catalyzed cross-coupling reactions of brominated porphyrins with bis(polyfluorophenylzinc reagents. The reaction is applicable to a variety of free-base bromoporphyrins, their metal complexes, and a number of bis(polyfluorophenylzinc reagents.

  2. C3 functionalization of indolizines via In(iii)-catalyzed three-component reaction.

    Science.gov (United States)

    Jung, Youngeun; Kim, Ikyon

    2015-12-01

    Post-functionalization at the C3 position of indolizines via In(iii)-catalyzed three-component coupling reaction with amines and aldehydes allowed rapid access to a new class of indolizines with diverse functional groups at the C3 position in good to excellent yields. PMID:26380932

  3. A new manganese-mediated, cobalt-catalyzed three-component synthesis of (diarylmethylsulfonamides

    Directory of Open Access Journals (Sweden)

    Antoine Pignon

    2014-02-01

    Full Text Available The synthesis of (diarylmethylsulfonamides and related compounds by a new manganese-mediated, cobalt-catalyzed three-component reaction between sulfonamides, carbonyl compounds and organic bromides is described. This organometallic Mannich-like process allows the formation of the coupling products within minutes at room temperature. A possible mechanism, emphasizing the crucial role of manganese is proposed.

  4. A new manganese-mediated, cobalt-catalyzed three-component synthesis of (diarylmethyl)sulfonamides

    Science.gov (United States)

    Pignon, Antoine; Martens, Thierry

    2014-01-01

    Summary The synthesis of (diarylmethyl)sulfonamides and related compounds by a new manganese-mediated, cobalt-catalyzed three-component reaction between sulfonamides, carbonyl compounds and organic bromides is described. This organometallic Mannich-like process allows the formation of the coupling products within minutes at room temperature. A possible mechanism, emphasizing the crucial role of manganese is proposed. PMID:24605162

  5. An Improved Protocol for the Pd-catalyzed α-Arylation of Aldehydes with Aryl Halides

    OpenAIRE

    Martín, Rubén; Buchwald, Stephen L.

    2008-01-01

    An improved protocol for the Pd-catalyzed α-arylation of aldehydes with aryl halides has been developed. The new catalytic system allows for the coupling of an array of substrates including challenging electron-rich aryl bromides and less reactive aryl chlorides. The utility of this method has been demonstrated in a new total synthesis of (±)-sporochnol.

  6. Synthesis of sulfonamides via copper-catalyzed oxidative C-N bond cleavage of tertiary amines.

    Science.gov (United States)

    Ji, Jing; Liu, Zhengyi; Liu, Ping; Sun, Peipei

    2016-08-01

    A copper-catalyzed coupling reaction of sulfonyl chlorides with tertiary amines via the oxidative C-N bond cleavage of tertiary amines was developed. Sulfonamides were synthesized using this strategy in moderate to good yields. The reaction was applicable to various tertiary amines, as well as sulfonyl chlorides. PMID:27356858

  7. Palladium-Catalyzed Carbonylation of Aryl Bromides with N-Substituted Cyanamides

    DEFF Research Database (Denmark)

    Lian, Zhong; Friis, Stig D.; Lindhardt, Anders T.;

    2014-01-01

    The palladium(0)-catalyzed three-component coupling reaction of aryl bromides, carbon monoxide, and N-alkyl cyan­amides has been developed employing a two-chamber system with ex situ generation of carbon monoxide from a silacarboxylic acid. The reactions proceeded well and were complete with a...

  8. Homocoupling of benzyl halides catalyzed by POCOP-nickel pincer complexes

    KAUST Repository

    Chen, Tao

    2012-08-01

    Two types of POCOP-nickel(II) pincer complexes were prepared by mixing POCOP pincer ligands and NiX 2 in toluene at reflux. The resulting nickel complexes efficiently catalyze the homocoupling reactions of benzyl halides in the presence of zinc. The coupled products were obtained in excellent to quantitative yields. © 2012 Elsevier Ltd. All rights reserved.

  9. Synthesis of Flurbiprofen via Suzuki Reaction Catalyzed by Palladium Charcoal in Water

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Flurbiprofen 1, an excellent nonsteroidal an tiinflammatory drug, was synthesized in 5steps in 69% overall yield. The key step of constructing the biaryl fragment was successfully achieved via Pd/C-catalyzed Suzuki coupling reaction in water using sodium tetraphenylborate as phenylation reagent.

  10. Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process

    Directory of Open Access Journals (Sweden)

    Jiancan Zhao

    2013-08-01

    Full Text Available A Fe(acac3-catalyzed decarboxylative coupling of 2-(arylvinyl carboxylic acids with cycloalkanes was developed by using DTBP as an oxidant through a radical process. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields (71–95%. The reaction also shows excellent stereoselectivity, and only trans-isomers are obtained.

  11. Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process

    OpenAIRE

    Jiancan Zhao; Hong Fang; Jianlin Han; Yi Pan

    2013-01-01

    A Fe(acac)3-catalyzed decarboxylative coupling of 2-(aryl)vinyl carboxylic acids with cycloalkanes was developed by using DTBP as an oxidant through a radical process. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields (71–95%). The reaction also shows excellent stereoselectivity, and only trans-isomers are obtained.

  12. Z-Selective copper-catalyzed asymmetric allylic alkylation with Grignard reagents.

    Science.gov (United States)

    Giannerini, Massimo; Fañanás-Mastral, Martín; Feringa, Ben L

    2012-03-01

    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 1,3-cis,trans dienes. PMID:22352853

  13. Iron-catalyzed decarboxylative alkenylation of cycloalkanes with arylvinyl carboxylic acids via a radical process.

    Science.gov (United States)

    Zhao, Jiancan; Fang, Hong; Han, Jianlin; Pan, Yi

    2013-01-01

    A Fe(acac)3-catalyzed decarboxylative coupling of 2-(aryl)vinyl carboxylic acids with cycloalkanes was developed by using DTBP as an oxidant through a radical process. This reaction tolerates a wide range of substrates, and products are obtained in good to excellent yields (71-95%). The reaction also shows excellent stereoselectivity, and only trans-isomers are obtained. PMID:24062833

  14. Z-Selective Copper-Catalyzed Asymmetric Allylic Alkylation with Grignard Reagents

    OpenAIRE

    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 1,3-cis,trans dienes.

  15. Palladium-catalyzed cross-couplings in organic synthesis:An introduction to the 2010 Nobel Prize in Chemistry%有机合成中钯催化交叉偶联反应:2010年诺贝尔化学奖成果简介

    Institute of Scientific and Technical Information of China (English)

    陈垚; 赖文勇; 解令海; 黄维

    2011-01-01

    The 2010 Nobel Prize in Chemistry was awarded by the Royal Swedish Academy of Sciences to Professor Richard F. Heck, Professor Ei-ichi Negishi and Professor Akira Suzuki for “palladium-catalyzed cross-couplings in organic synthesis”. The discoveries made by the these three organic chemists have had a great impact on academic research and industrial applications. Their reactions have proved extremely powerful and are widely used for the synthesis of organic electronic materials, new drugs, pharmaceuticals and biologically active compounds. In this report, we present a brief introduction to the 2010 Nobel Prize in Chemistry and the related Heck, Nigishi,and Suzuki-Miyaura reactions. We also discuss the recent advances and applications involving these reactions, especially in the field of organic electronics.%瑞典皇家科学院将2010年诺贝尔化学奖授予美国和日本的3位科学家理查德.海克(Richard F.Heck)、根岸英-(Ei-ichi Negishi)和铃木章(Akira Suzuki),以表彰他们在"有机合成中钯催化交叉偶联反应"方面所做出的杰出贡献.他们的研究成果极大地促进了有机合成化学的发展,广泛应用于合成制备具有特殊光电功能的高性能有机电子材料、具有复杂结构的天然产物和生物活性化合物以及一些精细化学品,对学术界和工业界产生了重要影响.本文简要介绍了Heck反应、Negishi反应和Suzuki-Miyaura反应的基本知识,并讨论了其发展和应用概况.

  16. Palladium-Catalyzed α-Arylation of Aryl Acetic Acid Derivatives via Dienolate Intermediates with Aryl Chlorides and Bromides

    OpenAIRE

    Sha, Sheng-Chun; Zhang, Jiadi; Walsh, Patrick J.

    2015-01-01

    To date, examples of α-arylation of carboxylic acids remain scarce. Using a deprotonative cross-coupling process (DCCP), a method for palladium-catalyzed γ-arylation of aryl acetic acids with aryl halides has been developed. This protocol is applicable to a wide range of aryl bromides and chlorides. A procedure for the palladium-catalyzed α-arylation of styryl acetic acids is also described.

  17. Microwave-assisted Cu-catalyzed Ullmann ether synthesis in a continuous-flow milli-plant

    OpenAIRE

    Benaskar, F.; Patil, N G; Meuldijk, J.; Hulshof, L.A.; Hessel, V.; Schouten, J.C.; Engels, V.; Wheatley, A.E.H.; Rebrov, E.V.

    2012-01-01

    The combination of milli-scale processing and microwave heating has been investigated for the Cu-catalyzed Ullmann etherification in fine-chemical synthesis, providing improved catalytic activity and selective catalyst heating. Wall-coated and fixed-bed milli-reactors were designed and applied in the Cu-catalyzed Ullmann-type CO coupling of phenol and 4-chloropyridine. In a batch reactor the results show clearly increased yields for the microwave heated process at low microwave powers, wherea...

  18. Palladium-Catalyzed C–C Bond Formations via Activation of Carboxylic Acids and Their Derivatives

    OpenAIRE

    Song, Bingrui

    2013-01-01

    Applications of carboxylic acids and their derivatives in transition metal-catalyzed cross-coupling reactions regio-selectively forming Csp3-Csp2, and Csp2-Csp2 bonds were explored in this thesis. Several important organic building blocks such as aryl acetates, diaryl acetates, imines, ketones, biaryls, styrenes and polysubstituted alkenes were successfully accessed from carboxylic acids and their derivatives by the means of C–H activation and decarboxylative cross-couplings. An efficient ...

  19. Palladium-catalyzed insertion of N-tosylhydrazones and trapping with carbon nucleophiles.

    Science.gov (United States)

    Zhou, Ping-Xin; Ye, Yu-Ying; Liang, Yong-Min

    2013-10-01

    A Pd-catalyzed three-component cross-coupling reaction of vinyl iodide, N-tosylhydrazone, and carbon nucleophiles is reported, and a one-pot procedure is also developed. The cross-coupling is proposed to proceed through a palladium-carbene migratory insertion, carbopalladation other than classic palladium-carbene migratory insertion, and β-H elimination. Moreover, the reaction proceeds under mild conditions and with high stereoselectivity. PMID:24070001

  20. Advances in nickel-catalyzed cycloaddition reactions to construct carbocycles and heterocycles.

    Science.gov (United States)

    Thakur, Ashish; Louie, Janis

    2015-08-18

    Transition-metal catalysis has revolutionized the field of organic synthesis by facilitating the construction of complex organic molecules in a highly efficient manner. Although these catalysts are typically based on precious metals, researchers have made great strides in discovering new base metal catalysts over the past decade. This Account describes our efforts in this area and details the development of versatile Ni complexes that catalyze a variety of cycloaddition reactions to afford interesting carbocycles and heterocycles. First, we describe our early work in investigating the efficacy of N-heterocyclic carbene (NHC) ligands in Ni-catalyzed cycloaddition reactions with carbon dioxide and isocyanate. The use of sterically hindered, electron donating NHC ligands in these reactions significantly improved the substrate scope as well as reaction conditions in the syntheses of a variety of pyrones and pyridones. The high reactivity and versatility of these unique Ni(NHC) catalytic systems allowed us to develop unprecedented Ni-catalyzed cycloadditions that were unexplored due to the inefficacy of early Ni catalysts to promote hetero-oxidative coupling steps. We describe the development and mechanistic analysis of Ni/NHC catalysts that couple diynes and nitriles to form pyridines. Kinetic studies and stoichiometric reactions confirmed a hetero-oxidative coupling pathway associated with this Ni-catalyzed cycloaddition. We then describe a series of new substrates for Ni-catalyzed cycloaddition reactions such as vinylcyclopropanes, aldehydes, ketones, tropones, 3-azetidinones, and 3-oxetanones. In reactions with vinycyclopropanes and tropones, DFT calculations reveal noteworthy mechanistic steps such as a C-C σ-bond activation and an 8π-insertion of vinylcyclopropane and tropone, respectively. Similarly, the cycloaddition of 3-azetidinones and 3-oxetanones also requires Ni-catalyzed C-C σ-bond activation to form N- and O-containing heterocycles. PMID:26200651

  1. Muon catalyzed fusion under compressive conditions

    International Nuclear Information System (INIS)

    The viability of a symbiotic combination of Muon Catalyzed Fusion (μCF) and high density generation processes has been investigated. The muon catalyzed fusion reaction rates are formulated in the temperature and density range found under moderate compressive conditions. Simplified energy gain and power balance calculations indicate that significant energy gain occurs only if standard type deuterium-tritium (dt) fusion is ignited. A computer simulation of the hydrodynamics and fusion kinetics of a spherical deuterium-tritium pellet implosion including muons is performed. Using the muon catalyzed fusion reaction rates formulated and under ideal conditions, the pellet ignites (and thus has a significant energy gain) only if the initial muon concentration is approximately 1017 cm-3. The muons need to be delivered to the pellet within a very short-time (≅ 1 ns). The muon pulse required in order to make the high density and temperature muon catalyzed fusion scheme viable is beyond the present technology for muon production. (orig.)

  2. Ruthenium-Catalyzed Transformations of Alcohols: Mechanistic Investigations and Methodology Development

    DEFF Research Database (Denmark)

    Makarov, Ilya; Madsen, Robert; Fristrup, Peter

    The mechanism of the ruthenium-catalyzed dehydrogenative synthesis of amides from alcohols and amines was studied in detail by employing the combination of experimental and theoretical techniques. The Hammett study revealed that a small positive charge is formed at the benzylic position in the......-substituted ruthenium complex afforded the amide in 38% yield. It indicated that in silico ligand screening might be used for catalyst optimization if it is combined with a more comprehensive experimental study. An improved protocol was developed for the ruthenium-catalyzed dehydrogenative self-coupling of primary...... unknown ruthenium-catalyzed dehydrogenative Guerbet reaction with secondary alcohols to give ketones was discovered. The reaction conditions were optimized and the scope and the limitations were studied. It was found that only acyclic 2-methyl carbinols and simple cyclic alcohols underwent this...

  3. Rhodium-catalyzed acyloxy migration of propargylic esters in cycloadditions, inspiration from the recent "gold rush".

    Science.gov (United States)

    Shu, Xing-Zhong; Shu, Dongxu; Schienebeck, Casi M; Tang, Weiping

    2012-12-01

    Transition metal-catalyzed acyloxy migration of propargylic esters offers versatile entries to allene and vinyl carbene intermediates for various fascinating subsequent transformations. Most π-acidic metals (e.g. gold and platinum) are capable of facilitating these acyloxy migration events. However, very few of these processes involve redox chemistry, which are well-known for most other transition metals such as rhodium. The coupling of acyloxy migration of propargylic esters with oxidative addition, migratory insertion, and reductive elimination may lead to ample new opportunities for the design of new reactions. This tutorial review summarizes recent developments in Rh-catalyzed 1,3- and 1,2-acyloxy migration of propargylic esters in a number of cycloaddition reactions. Related Au- and Pt-catalyzed cycloadditions involving acyloxy migration are also discussed. PMID:22895533

  4. Cross-Coupling Reaction with Lithium Methyltriolborate

    Directory of Open Access Journals (Sweden)

    Norio Miyaura

    2012-12-01

    Full Text Available We newly developed lithium methyltriolborate as an air-stable white solid that is convenient to handle. The good performance of this triolborate for metal-catalyzed bond-forming reactions was demonstrated in palladium-catalyzed cross-coupling reactions with haloarenes. Cross-coupling reaction of [MeB(OCH23CCH3]Li with aryl halides occurred in the presence of Pd(OAc2/RuPhos complex in refluxing MeOH/H2O and the absence of bases.

  5. Cross-Coupling Reaction with Lithium Methyltriolborate

    OpenAIRE

    Norio Miyaura; Hajime Ito; Yasunori Yamamoto; Kazuya Ikizakura

    2012-01-01

    We newly developed lithium methyltriolborate as an air-stable white solid that is convenient to handle. The good performance of this triolborate for metal-catalyzed bond-forming reactions was demonstrated in palladium-catalyzed cross-coupling reactions with haloarenes. Cross-coupling reaction of [MeB(OCH2)3CCH3]Li with aryl halides occurred in the presence of Pd(OAc)2/RuPhos complex in refluxing MeOH/H2O and the absence of bases.

  6. Cross-Coupling Reaction with Lithium Methyltriolborate

    OpenAIRE

    Yamamoto, Yasunori; Ikizakura, Kazuya; Ito, Hajime; Miyaura, Norio

    2013-01-01

    We newly developed lithium methyltriolborate as an air-stable white solid that is convenient to handle. The good performance of this triolborate for metal-catalyzed bond-forming reactions was demonstrated in palladium-catalyzed cross-coupling reactions with haloarenes. Cross-coupling reaction of [MeB(OCH2)3CCH3]Li with aryl halides occurred in the presence of Pd(OAc)2/RuPhos complex in refluxing MeOH/H2O and the absence of bases.

  7. Homogeneous and heterogeneous photoredox-catalyzed hydroxymethylation of ketones and keto esters: catalyst screening, chemoselectivity and dilution effects

    Directory of Open Access Journals (Sweden)

    Axel G. Griesbeck

    2014-05-01

    Full Text Available The homogeneous titanium- and dye-catalyzed as well as the heterogeneous semiconductor particle-catalyzed photohydroxymethylation of ketones by methanol were investigated in order to evaluate the most active photocatalyst system. Dialkoxytitanium dichlorides are the most efficient species for chemoselective hydroxymethylation of acetophenone as well as other aromatic and aliphatic ketones. Pinacol coupling is the dominant process for semiconductor catalysis and ketone reduction dominates the Ti(OiPr4/methanol or isopropanol systems. Application of dilution effects on the TiO2 catalysis leads to an increase in hydroxymethylation at the expense of the pinacol coupling.

  8. Gold-Catalyzed Direct Arylation

    OpenAIRE

    Ball, L. T.; Lloyd-jones, G. C.; Russell, C. A.

    2012-01-01

    Biaryls (two directly connected aromatic rings, Ar1-Ar2) are common motifs in pharmaceuticals, agrochemicals, and organic materials. Current methods for establishing the Ar1-Ar2 bond are dominated by the cross-coupling of aryl halides (Ar1-X) with aryl metallics (Ar2-M). We report that, in the presence of 1 to 2 mole percent of a gold catalyst and a mild oxidant, a wide range of arenes (Ar1-H) undergo site-selective arylation by arylsilanes (Ar2-SiMe3) to generate biaryls (Ar1-Ar2), with litt...

  9. G Protein-coupled receptors

    OpenAIRE

    Ross, Elliott M.

    2014-01-01

    G protein-coupled receptors and heterotrimeric G proteins can diffuse laterally in the plasma membrane such that one receptor can catalyze the activation (GDP/GTP exchange) of multiple G proteins. In some cases, these processes are fast enough to support molecular signal amplification, where a single receptor maintains the activation of multiple G proteins at steady-state. Amplification in cells is probably highly regulated. It depends upon the identities of the G receptor and G protein - som...

  10. Attractor Explosions and Catalyzed Vacuum Decay

    Energy Technology Data Exchange (ETDEWEB)

    Green, Daniel; Silverstein, Eva; Starr, David

    2006-05-05

    We present a mechanism for catalyzed vacuum bubble production obtained by combining moduli stabilization with a generalized attractor phenomenon in which moduli are sourced by compact objects. This leads straightforwardly to a class of examples in which the Hawking decay process for black holes unveils a bubble of a different vacuum from the ambient one, generalizing the new endpoint for Hawking evaporation discovered recently by Horowitz. Catalyzed vacuum bubble production can occur for both charged and uncharged bodies, including Schwarzschild black holes for which massive particles produced in the Hawking process can trigger vacuum decay. We briefly discuss applications of this process to the population and stability of metastable vacua.

  11. Palladium-Catalyzed Amination of Bromoanthancene

    Institute of Scientific and Technical Information of China (English)

    YU Ming-Xin; CHEN Xiao-Hang; CHENG Chien-Hong

    2003-01-01

    @@ Triarylamines are an important class of compounds, because they have been used as the hole-transport layer in electroluminescent devices. [1] New palladium catalyzed methods to form arylamines have emerged recently from Hartwing and Bucchwald . [2,3] Our group have investigated unusual diboration of allenes catalyzed by palladium complex and organic iodides. [4] Here we will report that arylamines react with bromoanthrancene (or dibromoanthancene) to afford triarylamines in the presence of Ligand-palladium complex. The structures of products were de termined by 1H NMR, 13C NMR, 13C (DEPT), IR and MS (HREI and EI) spectra.

  12. Peroxidase catalyzed conjugation of peptides, proteins and polysaccharides via endogenous and exogenous phenols.

    OpenAIRE

    Oudgenoeg, G.

    2004-01-01

    The research was directed towards peroxidase mediated cross-linking of proteins and polysaccharides. Two approaches were explored, cross-linking by use of ferulic acid (FA)oand cross-linking by use of catechol. Within each approach, first model studies were performed with small peptides, of which the findings were applied in subsequent studies with proteins. First, a kinetically controlled incubation that leads to covalently coupled adducts of the tripeptide Gly-Tyr-Gly (GYG) and FA, catalyze...

  13. Synthesis of alpha-tetrasubstituted triazoles by copper-catalyzed silyl deprotection/azide cycloaddition

    OpenAIRE

    Zachary L. Palchak; Nguyen, Paula T; Larsen, Catharine H

    2015-01-01

    Propargylamines are popular substrates for triazole formation, but tetrasubstituted variants have required multistep syntheses involving stoichiometric amounts of metal. A recent cyclohexanone–amine–silylacetylene coupling forms silyl-protected tetrasubstituted propargylamines in a single copper-catalyzed step. The development of the tandem silyl deprotection–triazole formation reported herein offers rapid access to alpha-tetrasubstituted triazoles. A streamlined two-step approach to this unc...

  14. Regiochemical Control in the Metal-Catalyzed Transposition of Allylic Silyl Ethers

    OpenAIRE

    Hansen, Eric C.; Lee, Daesung

    2006-01-01

    A novel mode of regiochemical control over the allylic [1,3]-transposition of silyloxy groups catalyzed by Re2O7 has been developed. This strategy relies on a cis-oriented vinyl boronate, generated from the Alder ene reaction of homoallylic silyl ethers and alkynyl boronates, to trap out the allylic hydroxyl group. The resulting cyclic boronic acids are excellent partners for cross coupling reactions. High chirality transfer is observed for the rearrangement of enantioenriched allylic silyl e...

  15. Diastereoselective metal-catalyzed synthesis of C-aryl and C-vinyl glycosides.

    Science.gov (United States)

    Nicolas, Lionel; Angibaud, Patrick; Stansfield, Ian; Bonnet, Pascal; Meerpoel, Lieven; Reymond, Sébastien; Cossy, Janine

    2012-10-29

    Cobalt, the catalyst of choice: The diastereoselective cobalt-catalyzed cross-coupling of 1-bromo glycosides and aryl or vinyl Grignard reagents is described. A convenient and inexpensive catalyst, [Co(acac)(3)]/tmeda (acac = acetylacetonate, tmeda = N,N'-tetramethylethylenediamine), gives full α selectivity in the mannose and galactose series, and an α selectivity in the glucose series with α/β ratios of 1.3:1-3:1. PMID:23023954

  16. Thermodynamic driving force effects in the oxygen reduction catalyzed by a metal-free porphyrin

    International Nuclear Information System (INIS)

    Graphical abstract: - Abstract: Cyclic voltammetry and the stopped-flow kinetic measurements are used to investigate the thermodynamic driving force effects in the molecular oxygen reduction with the methyl (Me)-substituted ferrocenes MenFc (n = 0, 2, 4, 6, 8, 10) at the polarized water|1,2-dichloroethane (DCE) interface and in the homogeneous DCE phase, which is catalyzed by 5,10,15,20-meso-tetraphenylporphyrin (H2TPP) dissolved in DCE. Ferrocene derivatives are characterized by their reversible half-wave potentials E1/2rev which are inferred from cyclic voltammetric data, and by the coresponding formal potentials E′0(SHE,o) referenced to the standard hydrogen electrode in DCE. It is shown that the reduction of the activated oxygen with MenFc is the rate-determining step in both electrochemical and chemical catalytic cycles. Plots of the logarithm of the rate constant of the catalyzed, non-catalyzed and electrocatalyzed oxygen reduction vs. the reversible half-wave potential for the MenFc+/MenFc redox couples in DCE have approximately the same slopes. Their values correspond to the Brønsted coefficient of about 1/2, which is characteristic for reactions with the symmetric activation barrier. A comparison of rates of the catalyzed and non-catalyzed oxygen reduction points to the inhibitory effect of water in the former case. Observed difference between the rates of the catalyzed and electrocatalyzed oxygen reduction was ascribed to the inhibitory effect of the present counteranion.

  17. 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...

  18. Palladium Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Engelin, Casper Junker; Fristrup, Peter

    2011-01-01

    The atom-efficiency of one of the most widely used catalytic reactions for forging C-C bonds, the Tsuji-Trost reaction, is limited by the need of preoxidized reagents. This limitation can be overcome by utilization of the recently discovered palladium-catalyzed C-H activation, the allylic C...

  19. Sulfilimimines in metal-catalyzed redox reactions

    Czech Academy of Sciences Publication Activity Database

    Voltrová, Svatava; Šrogl, Jiří

    Praha : -, 2009. s. 593-593. ISBN 978-80-02-02160-5. [ESOC 2009. European Symposium on Organic Chemistry /16./. 12.07.2009-16.07.2009, Praha] Institutional research plan: CEZ:AV0Z40550506 Keywords : sulfilimines * metal catalyzed oxidations * benzoisothiazolone Subject RIV: CC - Organic Chemistry

  20. Biodiesel production by enzyme-catalyzed transesterification

    Directory of Open Access Journals (Sweden)

    Stamenković Olivera S.

    2005-01-01

    Full Text Available The principles and kinetics of biodiesel production from vegetable oils using lipase-catalyzed transesterification are reviewed. The most important operating factors affecting the reaction and the yield of alkyl esters, such as: the type and form of lipase, the type of alcohol, the presence of organic solvents, the content of water in the oil, temperature and the presence of glycerol are discussed. In order to estimate the prospects of lipase-catalyzed transesterification for industrial application, the factors which influence the kinetics of chemically-catalysed transesterification are also considered. The advantages of lipase-catalyzed transesterification compared to the chemically-catalysed reaction, are pointed out. The cost of down-processing and ecological problems are significantly reduced by applying lipases. It was also emphasized that lipase-catalysed transesterification should be greatly improved in order to make it commercially applicable. The further optimization of lipase-catalyzed transesterification should include studies on the development of new reactor systems with immobilized biocatalysts and the addition of alcohol in several portions, and the use of extra cellular lipases tolerant to organic solvents, intracellular lipases (i.e. whole microbial cells and genetically-modified microorganisms ("intelligent" yeasts.

  1. Palladium catalyzed hydrogenation of bio-oils and organic compounds

    Science.gov (United States)

    Elliott, Douglas C.; Hu, Jianli; Hart, Todd R.; Neuenschwander, Gary G.

    2008-09-16

    The invention provides palladium-catalyzed hydrogenations of bio-oils and certain organic compounds. Experimental results have shown unexpected and superior results for palladium-catalyzed hydrogenations of organic compounds typically found in bio-oils.

  2. CuO-Al2O3 catalyzed oxidation of primary benzylamines and secondary dibenzylamines to N-benzylbenzaldimines

    Directory of Open Access Journals (Sweden)

    Jing Hui Zeng

    2013-06-01

    Full Text Available CuO-Al 2O 3 catalyzed one-pot oxidation with O 2 and self-coupling of benzylamines to give N-benzylbenzaldimines was described in good yields. Similarly, secondary dibenzylamines were oxidized to N-benzylbenzaldimines.

  3. N-Arylation of amines, amides, imides and sulfonamides with arylboroxines catalyzed by simple copper salt/EtOH system

    OpenAIRE

    Zheng, Zhang-Guo; Wen, Jun; Wang, Na; Wu, Bo; Yu, Xiao-Qi

    2008-01-01

    The coupling of arylboroxines with a variety of amines, amides, imides and sulfonamides catalyzed by a copper salt/EtOH system has been developed. In the absence of a base or additive the corresponding N-arylation products were obtained in moderate to excellent yields.

  4. Kinetics of aggregation growth with competition between catalyzed birth and catalyzed death

    International Nuclear Information System (INIS)

    An aggregation growth model of three species A, B and C with the competition between catalyzed birth and catalyzed death is proposed. Irreversible aggregation occurs between any two aggregates of the like species with the constant rate kernels In(n = 1,2,3). Meanwhile, a monomer birth of an A species aggregate of size k occurs under the catalysis of a B species aggregate of size j with the catalyzed birth rate kernel K(k,j) = Kkjv and a monomer death of an A species aggregate of size k occurs under the catalysis of a C species aggregate of size j with the catalyzed death rate kernel L(k,j)=Lkjv, where v is a parameter reflecting the dependence of the catalysis reaction rates of birth and death on the size of catalyst aggregate. The kinetic evolution behaviours of the three species are investigated by the rate equation approach based on the mean-field theory. The form of the aggregate size distribution of A species ak(t) is found to be dependent crucially on the competition between the catalyzed birth and death of A species, as well as the irreversible aggregation processes of the three species: (1) In the v k(t) satisfies the conventional scaling form; (2) In the v ≥ 0 case, the competition between the catalyzed birth and death dominates the process. When the catalyzed birth controls the process, ak(t) takes the conventional or generalized scaling form. While the catalyzed death controls the process, the scaling description of the aggregate size distribution breaks down completely

  5. Nickel-catalyzed vinylation of aryl chlorides and bromides with vinyl ZnBr.MgBrCl.

    Science.gov (United States)

    Yamamoto, Tetsuya; Yamakawa, Tetsu

    2009-05-01

    The Ni-catalyzed cross-coupling of aryl halides and vinylzinc bromide for the synthesis of styrene derivatives was investigated. Of the catalysts surveyed, the combination of Ni(acac)(2) and Xantphos was found to be the most effective for this cross-coupling. This catalyst could be used in reactions with various aryl bromides and chlorides, including electron-rich aryl chlorides such as chloroanisoles. PMID:19354270

  6. Palladium-Catalyzed Regioselective Diarylation of o-Carboranes By Direct Cage B-H Activation.

    Science.gov (United States)

    Quan, Yangjian; Xie, Zuowei

    2016-01-22

    Palladium-catalyzed intermolecular coupling of o-carborane with aromatics by direct cage B-H bond activation has been achieved, leading to the synthesis of a series of cage B(4,5)-diarylated-o-carboranes in high yields with excellent regioselectivity. Traceless directing group -COOH plays a crucial role for site- and di-selectivity of such intermolecular coupling reaction. A Pd(II)-Pd(IV)-Pd(II) catalytic cycle is proposed to be responsible for the stepwise arylation. PMID:26463595

  7. Copper-catalyzed decarboxylative sulfonylation of α,β-unsaturated carboxylic acids.

    Science.gov (United States)

    Rokade, Balaji V; Prabhu, Kandikere Ramaiah

    2014-09-01

    Copper-catalyzed, ligand-promoted decarboxylative coupling of readily available α,β-unsaturated acids with sodium aryl sulfinates is presented. This method provides a new avenue for the synthesis of vinyl sulfones via a decarboxylative radical coupling strategy by employing a catalytic amount of Cu(ClO4)2·6H2O, TBHP in decane as an oxidant, and 1,10-phenanthroline as a ligand. The salient feature of this method is that it furnishes exclusively the (E)-isomer. PMID:25098975

  8. Parameters critical to muon-catalyzed fusion

    International Nuclear Information System (INIS)

    We have demonstrated that muon catalysis cycling rates increase rapidly with increasing deuterium-tritium gas temperatures and densities. Furthermore, muon-capture losses are significantly smaller than predicted before the experiments. There remains a significant gap between observation and theoretical expectation for the muon-alpha sticking probability in dense d-t mixtures. We have been able to achieve muon-catalyzed yields of 150 fusion/muon (average). While the fusion energy thereby released significantly exceeds expectations, enhancements by nearly a factor of twenty would be needed to realize energy applications for a pure (non-hybrid) muon-catalyzed fusion reactor. The process could be useful in tritium-breeding schemes. We have also explored a new form of cold nuclear fusion which occurs when hydrogen isotopes are loaded into metals. 22 refs., 10 figs

  9. Cold fusion catalyzed by muons and electrons

    International Nuclear Information System (INIS)

    Two alternative methods have been suggested to produce fusion power at low temperature. The first, muon catalyzed fusion or MCF, uses muons to spontaneously catalyze fusion through the muon mesomolecule formation. Unfortunately, this method fails to generate enough fusion energy to supply the muons, by a factor of about ten. The physics of MCF is discussed, and a possible approach to increasing the number of MCF fusions generated by each muon is mentioned. The second method, which has become known as ''Cold Fusion,'' involves catalysis by electrons in electrolytic cells. The physics of this process, if it exists, is more mysterious than MCF. However, it now appears to be an artifact, the claims for its reality resting largely on experimental errors occurring in rather delicate experiments. However, a very low level of such fusion claimed by Jones may be real. Experiments in cold fusion will also be discussed

  10. Copper Catalyzed Oceanic Methyl Halide Production

    OpenAIRE

    Robin Kim, Jae Yun; Rhew, Robert

    2014-01-01

    Methyl halides are found in all of Earth’s biomes, produced naturally or through manmade means. Their presence in the atmosphere is problematic, as they catalyze depletion of stratospheric ozone. To understand the full environmental impact of these compounds, it is important to identify their chemical cycling processes. Iron increases methyl halide production in soils and oceans, yet copper’s influence remains unknown despite its similar chemical oxidation properties to iron. I experimentally...

  11. Antibody-Catalyzed Degradation of Cocaine

    Science.gov (United States)

    Landry, Donald W.; Zhao, Kang; Yang, Ginger X.-Q.; Glickman, Michael; Georgiadis, Taxiarchis M.

    1993-03-01

    Immunization with a phosphonate monoester transition-state analog of cocaine provided monoclonal antibodies capable of catalyzing the hydrolysis of the cocaine benzoyl ester group. An assay for the degradation of radiolabeled cocaine identified active enzymes. Benzoyl esterolysis yields ecgonine methyl ester and benzoic acid, fragments devoid of cocaine's stimulant activity. Passive immunization with such an artificial enzyme could provide a treatment for dependence by blunting reinforcement.

  12. Palladium(II-catalyzed Heck reaction of aryl halides and arylboronic acids with olefins under mild conditions

    Directory of Open Access Journals (Sweden)

    Tanveer Mahamadali Shaikh

    2013-08-01

    Full Text Available A series of general and selective Pd(II-catalyzed Heck reactions were investigated under mild reaction conditions. The first protocol has been developed employing an imidazole-based secondary phosphine oxide (SPO ligated palladium complex (6 as a precatalyst. The catalytic coupling of aryl halides and olefins led to the formation of the corresponding coupled products in excellent yields. A variety of substrates, both electron-rich and electron-poor olefins, were converted smoothly to the targeted products in high yields. Compared with the existing approaches employing SPO–Pd complexes in a Heck reaction, the current strategy features mild reaction conditions and broad substrate scope. Furthermore, we described the coupling of arylboronic acids with olefins, which were catalyzed by Pd(OAc2 and employed N-bromosuccinimide as an additive under ambient conditions. The resulted biaryls have been obtained in moderate to good yields.

  13. Aminophenols as Efficient Ligand for Copper-Catalyzed Ullmann-type Synthesis of Diaryl Ethers

    International Nuclear Information System (INIS)

    An efficient Cu-catalyzed synthesis of diaryl ethers from various aromatic iodides (bromides) and phenols was developed by using L2(2-((o-toluidino)methyl)phenol) as the ligand. The present protocol is applicable to a variety of phenols and aryl iodides (bromides) containing electron-withdrawing, electron-donating, and sterically demanding substrate combinations under mild conditions. The further study on design and application of new ligands in copper based Ullmann-type coupling reaction is currently ongoing. Carbon-oxygen bonds extensively exist in all kinds of biologically active natural products, important pharmaceutical compounds and polymers. The palladium-catalyzed formation of carbon-oxygen bonds is one of the two major methods available for aryl ether synthesis. However, palladium-based protocols, although successful, have some inherent limitations such as moisture sensitivity, costly metal catalysts, and environmental toxicity

  14. Cobalt-Catalyzed Annulation of Salicylaldehydes and Alkynes to Form Chromones and 4-Chromanones.

    Science.gov (United States)

    Yang, Junfeng; Yoshikai, Naohiko

    2016-02-01

    A unique cobalt(I)-diphosphine catalytic system has been identified for the coupling of salicylaldehyde (SA) and an internal alkyne affording a dehydrogenative annulation product (chromone) or a reductive annulation product (4-chromanone) depending on the alkyne substituents. Distinct from related rhodium(I)- and rhodium(III)-catalyzed reactions of SA and alkynes, these annulation reactions feature aldehyde C-H oxidative addition of SA and subsequent hydrometalation of the C=O bond of another SA molecule as common key steps. The reductive annulation to 4-chromanones also involves the action of Zn as a stoichiometric reductant. In addition to these mechanistic features, the Co(I) catalysis described herein is complementary to the Rh(I) - and Rh(III) -catalyzed reactions of SA and internal alkynes, particularly in the context of chromone synthesis. PMID:26804050

  15. Dissection of an antibody-catalyzed reaction.

    OpenAIRE

    Stewart, J D; Krebs, J F; Siuzdak, G; Berdis, A J; Smithrud, D B; Benkovic, S J

    1994-01-01

    Antibody 43C9 accelerates the hydrolysis of a p-nitroanilide by a factor of 2.5 x 10(5) over the background rate in addition to catalyzing the hydrolysis of a series of aromatic esters. Since this represents one of the largest rate accelerations achieved with an antibody, we have undertaken a series of studies aimed at uncovering the catalytic mechanism of 43C9. The immunogen, a phosphonamidate, was designed to mimic the geometric and electronic characteristics of the tetrahedral intermediate...

  16. Ligand Intermediates in Metal-Catalyzed Reactions

    Energy Technology Data Exchange (ETDEWEB)

    Gladysz, John A.

    1999-07-31

    The longest-running goal of this project has been the synthesis, isolation, and physical chemical characterization of homogeneous transition metal complexes containing ligand types believed to be intermediates in the metal-catalyzed conversion of CO/H{sub 2}, CO{sub 2}, CH{sub 4}, and similar raw materials to organic fuels, feedstocks, etc. In the current project period, complexes that contain unusual new types of C{sub x}(carbide) and C{sub x}O{sub y} (carbon oxide) ligands have been emphasized. A new program in homogeneous fluorous phase catalysis has been launched as described in the final report.

  17. Chiral Diamine-catalyzed Asymmetric Aldol Reaction

    Institute of Scientific and Technical Information of China (English)

    LI Hui; XU Da-zhen; WU Lu-lu; WANG Yong-mei

    2012-01-01

    A highly efficient catalytic system composed of a simple and commercially available chiral primary diamine (1R,2R)-cyclohexane-1,2-diamine(6) and trifluoroacetic acid(TFA) was employed for asymmetric Aldol reaction in i-PrOH at room temperature.A loading of 10%(molar fraction) catalyst 6 with TFA as a cocatalyst could catalyze the Aldol reactions of various ketones or aldehydes with a series of aromatic aldehydes,furnishing Aldol products in moderate to high yields(up to >99%) with enantioselectivities of up to >99% and diastereoselectivities of up to 99:1.

  18. Biginelli reaction catalyzed by copper nanoparticles.

    Directory of Open Access Journals (Sweden)

    Manika Dewan

    Full Text Available We recently reported a novel synthesis of copper nanoparticles from copper sulphate utilizing the charge-compensatory effect of ionic liquid [bmim]BF(4 and ethylene glycol. The nanoparticles were characterized and found to be stable for one year. Here we hypothesize that the stabilized nanoparticles should be able to catalyze one-pot multicomponent organic reactions. We show that the nanoparticles catalyzed Biginelli reaction at room temperature to give the product 3,4-dihydopyrimidinone (>90% yield in ~15 minutes from aldehydes, β-diketoester (ethylacetoacetate and urea (or thiourea. . Remarkably, such high yields and rapid kinetics was found to be independent of the electronic density on the reactant aryl-aldehyde. This was probably because even the surface-active particles reacted faster in the presence of ionic liquid as compared to conventional methods. The heterocyclic dihydropyrimidinones (DHPMs and their derivatives are widely used in natural and synthetic organic chemistry due to their wide spectrum of biological and therapeutic properties (resulting from their antibacterial, antiviral, antitumor and anti-inflammatory activities. Our method has an easy work-up procedure and the nanoparticles could be recycled with minimal loss of efficiency.

  19. Fe-promoted cross coupling of homobenzylic methyl ethers with Grignard reagents via sp3 C-O bond cleavage.

    Science.gov (United States)

    Luo, Shuang; Yu, Da-Gang; Zhu, Ru-Yi; Wang, Xin; Wang, Lei; Shi, Zhang-Jie

    2013-09-14

    The first iron-catalyzed formal cross coupling of homobenzylic methyl ethers with alkyl Grignard reagents is realized. The reaction is proposed to proceed through a sequence of dehydroalkoxylation to form the vinyl-intermediate, followed by Fe-catalyzed selective carbometalation to form a benzylic Grignard reagent. PMID:23884449

  20. Occurrence and Characteristics of a Rapid Exchange of Phosphate Oxygens Catalyzed by Sarcoplasmic Reticulum Vesicles

    Science.gov (United States)

    Kanazawa, T.; Boyer, P. D.

    1972-01-01

    Sarcoplasmic reticulum vesicles isolated from skeletal muscle actively take up Ca{sup ++} from the medium in the presence of Mg{sup ++} and ATP. This transport is coupled to ATP hydrolysis catalyzed by membrane-bound Ca{sup++}, Mg{sup ++}-ATPase which is activated by concurrent presence of Ca{sup ++} and Mg{sup ++}. Considerable informations have accumulated that give insight into the ATPase and its coupling to the calcium transport. The hydrolysis of ATP by this enzyme occurs through a phosphorylated intermediate. Formation and decomposition of the intermediate show vectorial requirements for Ca{sup ++} and Mg{sup ++}, suggesting an intimate involvement of the intermediate in the transport process. ATP synthesis from P{sub i} and ADP coupled to outflow of Ca{sup ++} from sarcoplasmic reticulum vesicles has recently been demonstrated. This indicates the reversibility of the entire process of calcium transport in sarcoplasmic reticulum vesicles.

  1. Manganese Catalyzed C-H Halogenation.

    Science.gov (United States)

    Liu, Wei; Groves, John T

    2015-06-16

    The remarkable aliphatic C-H hydroxylations catalyzed by the heme-containing enzyme, cytochrome P450, have attracted sustained attention for more than four decades. The effectiveness of P450 enzymes as highly selective biocatalysts for a wide range of oxygenation reactions of complex substrates has driven chemists to develop synthetic metalloporphyrin model compounds that mimic P450 reactivity. Among various known metalloporphyrins, manganese derivatives have received considerable attention since they have been shown to be versatile and powerful mediators for alkane hydroxylation and olefin epoxidation. Mechanistic studies have shown that the key intermediates of the manganese porphyrin-catalyzed oxygenation reactions include oxo- and dioxomanganese(V) species that transfer an oxygen atom to the substrate through a hydrogen abstraction/oxygen recombination pathway known as the oxygen rebound mechanism. Application of manganese porphyrins has been largely restricted to catalysis of oxygenation reactions until recently, however, due to ultrafast oxygen transfer rates. In this Account, we discuss recently developed carbon-halogen bond formation, including fluorination reactions catalyzed by manganese porphyrins and related salen species. We found that biphasic sodium hypochlorite/manganese porphyrin systems can efficiently and selectively convert even unactivated aliphatic C-H bonds to C-Cl bonds. An understanding of this novel reactivity derived from results obtained for the oxidation of the mechanistically diagnostic substrate and radical clock, norcarane. Significantly, the oxygen rebound rate in Mn-mediated hydroxylation is highly correlated with the nature of the trans-axial ligands bound to the manganese center (L-Mn(V)═O). Based on the ability of fluoride ion to decelerate the oxygen rebound step, we envisaged that a relatively long-lived substrate radical could be trapped by a Mn-F fluorine source, effecting carbon-fluorine bond formation. Indeed, this idea

  2. Critical behavior of a model for catalyzed autoamplification.

    Science.gov (United States)

    Tchernookov, Martin; Warmflash, Aryeh; Dinner, Aaron R

    2009-04-01

    We examine the critical behavior of a model of catalyzed autoamplification inspired by a common motif in genetic networks. Similar to models in the directed percolation (DP) universality class, a phase transition between an absorbing state with no copies of the autoamplifying species A and an active state with a finite amount of A occurs at the point at which production and removal of A are balanced. A suitable coordinate transformation shows that this model corresponds to one with three fields, one of which relaxes exponentially, one of which displays critical behavior, and one of which has purely diffusive dynamics but exerts an influence on the critical field. Using stochastic simulations that account for discrete molecular copy numbers in one, two, and three dimensions, we show that this model has exponents that are distinct from previously studied reaction-diffusion systems, including the few with more than one field (unidirectionally coupled DP processes and the diffusive epidemic process). Thus the requirement of a catalyst changes the fundamental physics of autoamplification. Estimates for the exponents of the diffusive epidemic process in two dimensions are also presented. PMID:19355779

  3. Oxidative 4-dechlorination of polychlorinated phenols is catalyzed by extracellular fungal lignin peroxidases

    International Nuclear Information System (INIS)

    The extracellular lignin peroxidases (ligninases) of Phanerochaete chrysosporium catalyzed H2O2-dependent spectral changes in several environmentally significant polychlorinated phenols: 2,4-dichloro-, 2,4,5-trichloro-, 2,4,6-trichloro-, and pentachlorophenol. Gas chromatography/mass spectrometry of reduced and acetylated reaction products showed that, in each case, lignin peroxidase catalyzed a 4-dechlorination of the starting phenol to yield a p-benzoquinone. The oxidation of 2,4-dichlorophenol also yielded a dechlorinated coupling dimer, tentatively identified as 2-chloro-6-(2,4-dichlorophenoxy)-p-benzoquinone. Experiments on the stoichiometry of 2,4,6-trichlorophenol oxidation showed that this substrate was quantitatively dechlorinated to give the quinone and inorganic chloride. H218O-labeling experiments on 2,4,6-trichlorophenol oxidation demonstrated that water was the source of the new 4-oxo substituent in 2,6-di-chloro-p-benzoquinone. The results indicate a mechanism whereby lignin peroxidase oxidizes a 4-chlorinated phenol to an electrophilic intermediate, perhaps the 4-chlorocyclohexadienone cation. Nucleophilic attack by water and elimination of HCl then ensue at the 4-position, which produces the quinone. Lignin peroxidases have previously been implicated in the degradation by Phanerochaete of several nonphenolic aromatic pollutants. It appears likely from their results that these peroxidases could also catalyze the initial dechlorination of certain polychlorinated phenols in vivo

  4. Palladium-Catalyzed Deaminative Phenanthridinone Synthesis from Aniline via C-H Bond Activation.

    Science.gov (United States)

    Yedage, Subhash L; Bhanage, Bhalchandra M

    2016-05-20

    This work reports palladium-catalyzed phenanthridinone synthesis using the coupling of aniline and amide by formation of C-C and C-N bonds in a one-pot fashion via dual C-H bond activation. It involves simultaneous cleavage of four bonds and the formation of two new bonds. The present protocol is ligand-free, takes place under mild reaction conditions, and is environmentally benign as nitrogen gas and water are the only side products. This transformation demonstrates a broad range of aniline and amide substrates with different functional groups and has been scaled up to gram level. PMID:27088815

  5. Transition Metal Catalyzed Reactions for Forming Carbon–Oxygen and Carbon–Carbon Bonds

    DEFF Research Database (Denmark)

    Sølvhøj, Amanda Birgitte

    Dehydrogenative ester formation with a ruthenium NHC complex A new atom-economical methodology for synthesizing esters by the dehydrogenative coupling of primary alcohols was developed. The reaction is catalyzed by the ruthenium N-heterocyclic carbene complex RuCl2(IiPr)(p-cymene). By screening the...... alcohols could be used as substrates, but the yields were generally poor due to decarbonylation of the substrate as a considerable side reaction. Some preliminary mechanistic investigations were performed. The results of these confirmed that the reaction is indeed dehydrogenative with the liberation of two...

  6. Palladium-Catalyzed Multicomponent Synthesis of 2-Imidazolines from Imines and Acid Chlorides

    Directory of Open Access Journals (Sweden)

    Boran Xu

    2012-11-01

    Full Text Available We describe the palladium-catalyzed multicomponent synthesis of 2-imidazolines. This reaction proceeds via the coupling of imines, acid chlorides and carbon monoxide to form imidazolinium carboxylates, followed by a decarboxylation. Decarboxylation in CHCl3 is found to result in a mixture of imidazolinium and imidazolium salts. However, the addition of benzoic acid suppresses aromatization, and generates the trans-disubstituted imidazolines in good yield. Combining this reaction with subsequent nitrogen deprotection provides an overall synthesis of imidazolines from multiple available building blocks.

  7. Synthesis of alpha-tetrasubstituted triazoles by copper-catalyzed silyl deprotection/azide cycloaddition

    Directory of Open Access Journals (Sweden)

    Zachary L. Palchak

    2015-08-01

    Full Text Available Propargylamines are popular substrates for triazole formation, but tetrasubstituted variants have required multistep syntheses involving stoichiometric amounts of metal. A recent cyclohexanone–amine–silylacetylene coupling forms silyl-protected tetrasubstituted propargylamines in a single copper-catalyzed step. The development of the tandem silyl deprotection–triazole formation reported herein offers rapid access to alpha-tetrasubstituted triazoles. A streamlined two-step approach to this uncommon class of hindered triazoles will accelerate exploration of their therapeutic potential. The superior activity of copper(II triflate in the formation of triazoles from sensitive alkyne substrates extends to simple terminal alkynes.

  8. Synthesis of (-)-Piperitylmagnolol Featuring ortho-Selective Deiodination and Pd-Catalyzed Allylation.

    Science.gov (United States)

    Ikoma, Atsushi; Ogawa, Narihito; Kondo, Daiki; Kawada, Hiroki; Kobayashi, Yuichi

    2016-05-01

    A 1,4-addition strategy using an enone and a copper reagent was studied for the synthesis of (-)-piperitylmagnolol. A MOM-protected biphenol copper reagent was added to BF3·OEt2-activated 4-isopropylcyclohexenone, whereas 1,4-addition of protected monophenol reagents possessing an allyl group was found to be unsuccessful. The allyl group was later attached to the p-,p'-diiodo-biphenol ring by Pd-catalyzed coupling with allylborate. The aforementioned iodide was synthesized using a new method for ortho-selective deiodination of o-,p-diiodophenols. PMID:27109890

  9. Synthetic applications of gold-catalyzed ring expansions

    Directory of Open Access Journals (Sweden)

    Cristina Nevado

    2011-06-01

    Full Text Available The development of new methodologies catalyzed by late transition metals involving cycloisomerizations of strained rings can open new venues for the synthesis of structurally complex molecules with interesting biological activities. Herein we summarize, from both a synthetic as well as a mechanistic point of view, the most recent developments in gold-catalyzed ring expansions.

  10. Hydrolysis of toxic natural glucosides catalyzed by cyclodextrin dicyanohydrins

    DEFF Research Database (Denmark)

    Bjerre, J.; Nielsen, Erik Holm Toustrup; Bols, M.

    2008-01-01

    The hydrolysis of toxic 7-hydroxycoumarin glucosides and other aryl and alkyl glucosides, catalyzed by modified a- and ß-cyclodextrin dicyanohydrins, was investigated using different UV, redox, or HPAEC detection assays. The catalyzed reactions all followed Michaelis-Menten kinetics, and an...

  11. The renaissance of palladium(II)-catalyzed oxidation chemistry

    OpenAIRE

    Sigman, Matthew S.; Schultz, Mitchell J.

    2004-01-01

    Palladium(II)-catalyzed oxidations constitute a paramount reaction class but have remained immature over the past few decades. Recently, this field has reappeared at the forefront of organometallic catalysis. This emerging area article outlines recent developments in palladium(II)-catalyzed oxidation chemistry with discussion of potential future growth.

  12. Toward Efficient Palladium-Catalyzed Allylic C-H Alkylation

    DEFF Research Database (Denmark)

    Jensen, Thomas; Fristrup, Peter

    2009-01-01

    Recent breakthroughs have proved that direct palladium (II)-catalyzed allylic C-H alkylation can be achieved. This new procedure shows that the inherent requirement for a leaving group in the Tsuji-Trost palladium-catalyzed allylic alkylation can be lifted. These initial reports hold great promise...

  13. Fabrication of silicon nanowire arrays by macroscopic galvanic cell-driven metal catalyzed electroless etching in aerated HF solution.

    Science.gov (United States)

    Liu, Lin; Peng, Kui-Qing; Hu, Ya; Wu, Xiao-Ling; Lee, Shuit-Tong

    2014-03-01

    Macroscopic galvanic cell-driven metal catalyzed electroless etching (MCEE) of silicon in aqueous hydrofluoric acid (HF) solution is devised to fabricate silicon nanowire (SiNW) arrays with dissolved oxygen acting as the one and only oxidizing agent. The key aspect of this strategy is the use of a graphite or other noble metal electrode that is electrically coupled with silicon substrate. PMID:24323873

  14. An approach to the synthesis of dimeric resveratrol natural products via a palladium-catalyzed domino reaction

    OpenAIRE

    Jeffrey, Jenna L.; Sarpong, Richmond

    2009-01-01

    A route for the rapid assembly of the carbon framework of several resveratrol natural products is presented. A palladium-catalyzed domino reaction of bromostilbene derivative 6 and tolane 7, involving two sequential Heck coupling reactions, provides access to the benzofulvene-based core of various resveratrol-derived natural products. The carbon skeleton of pallidol and its congeners is achieved by a Lewis acid-induced Nazarov-type oxidative cyclization of 9.

  15. Rhodium-Catalyzed Acyloxy Migration of Propargylic Esters in Cycloadditions, Inspiration from Recent “Gold Rush”

    OpenAIRE

    Shu, Xing-Zhong; Shu, Dongxu; Schienebeck, Casi M.; TANG, WEIPING

    2012-01-01

    Transition metal-catalyzed acyloxy migration of propargylic esters offers versatile entries to allene and vinyl carbene intermediates for various fascinating subsequent transformations. Most π-acidic metals (e.g. gold and platinum) are capable of facilitating these acyloxy migration events. However, very few of these processes involve redox chemistry, which are well-known for most other transition metals such as rhodium. The coupling of acyloxy migration of propargylic esters with oxidative a...

  16. Synthetic and Mechanistic Studies on the Solvent-Dependent Copper-Catalyzed Formation of Indolizines and Chalcones

    OpenAIRE

    Albaladejo Maricó, María José; Alonso Valdés, Francisco; González Soria, María José

    2015-01-01

    Copper nanoparticles supported on activated carbon have been found to catalyze the multicomponent synthesis of indolizines from pyridine-2-carbaldehyde derivatives, secondary amines, and terminal alkynes in dichloromethane; in the absence of solvent, however, heterocyclic chalcones are formed. We provide compelling evidence that both processes take place through aldehyde–amine–alkyne coupling intermediates. In contrast to other well-known mechanisms for chalcone formation from aldehydes and a...

  17. Convergent Synthesis of Diverse Nitrogen Heterocycles via Rh(III)-Catalyzed C-H Conjugate Addition/Cyclization Reactions.

    Science.gov (United States)

    Weinstein, Adam B; Ellman, Jonathan A

    2016-07-01

    The development of Rh(III)-catalyzed C-H conjugate addition/cyclization reactions that provide access to synthetically useful fused bi- and tricyclic nitrogen heterocycles is reported. A broad scope of C-H functionalization substrates and electrophilic olefin coupling partners is effective, and depending on the nature of the directing group, cyclic imide, amide, or heteroaromatic products are obtained. An efficient synthesis of a pyrrolophenanthridine alkaloid natural product, oxoassoanine, highlights the utility of this method. PMID:27337641

  18. Transition metal-catalyzed C(vinyl)-C(vinyl) bond formation via double C(vinyl)-H bond activation.

    Science.gov (United States)

    Shang, Xiaojie; Liu, Zhong-Quan

    2013-04-21

    Transition metal-catalyzed oxidative dehydrogenative coupling reactions of Caryl-H bonds with Cvinyl-H bonds to generate a Caryl-Cvinyl bonds have been well developed in recent decades. However, only a few studies have focused on the direct Cvinyl-Cvinyl bond formation via double Cvinyl-H bond activation. Recent developments in this active area have been highlighted in this tutorial review. PMID:23318664

  19. Catalyzed deuterium fueled tandem mirror reactor assessment

    International Nuclear Information System (INIS)

    This study was part of a Department of Energy supported alternate fusion fuels program at Science Applications International Corp. The purpose of this portion of the study is to perform an assessment of a conceptual tandem mirror reactor (TMR) that is fueled by the catalyzed-deuterium (Cat-d) fuel cycle with respect to the physics, technology, safety, and cost. Achievable stable betas and magnet configurations are found to be comparable for the Cat-d and d-t fueled TMR. A comparison with respect to cost, reactor performance, and technology requirements for a Cat-d fueled reactor and a comparable d-t fueled reactor such as MARS is also made

  20. Transition Metal Catalyzed Synthesis of Aryl Sulfides

    Directory of Open Access Journals (Sweden)

    Chad C. Eichman

    2011-01-01

    Full Text Available The presence of aryl sulfides in biologically active compounds has resulted in the development of new methods to form carbon-sulfur bonds. The synthesis of aryl sulfides via metal catalysis has significantly increased in recent years. Historically, thiolates and sulfides have been thought to plague catalyst activity in the presence of transition metals. Indeed, strong coordination of thiolates and thioethers to transition metals can often hinder catalytic activity; however, various catalysts are able to withstand catalyst deactivation and form aryl carbon-sulfur bonds in high-yielding transformations. This review discusses the metal-catalyzed arylation of thiols and the use of disulfides as metal-thiolate precursors for the formation of C-S bonds.

  1. Theoretical survey of muon catalyzed fusion

    International Nuclear Information System (INIS)

    The main steps in the muon-catalyzed d-t fusion cycle are given in this report. Most of the stages are very fast, and therefore do not contribute significantly to the cycling time. Thus at liquid H2 densities (/phi/ = 1 in the standard convention) the time for stopping the negative muon, its subsequent capture and deexcitation to the ground state is estimated to be /approximately/ 10/sup/minus/11/ sec.1 The muon spends essentially all of its time in either the (dμ) ground state, waiting for transfer to a (tμ) ground state to occur, or in the (tμ) ground state, writing for molecular formation to occur. Following the formation of this ''mesomolecule'' (actually a muonic molecular ion), deexcitation and fusion are again fast. Then the muon is (usually) liberated to go around again. We will discuss these steps in some detail. 5 refs., 3 figs

  2. Thioglycoside hydrolysis catalyzed by β-glucosidase

    International Nuclear Information System (INIS)

    Sweet almond β-glucosidase (EC 3.2.1.21) has been shown to have significant thioglycohydrolase activity. While the Km values for the S- and O-glycosides are similar, the kcat values are about 1000-times lower for the S-glycosides. Remarkably, the pH-profile for kcat/Km for hydrolysis of p-nitrophenyl thioglucoside (pNPSG) shows the identical dependence on a deprotonated carboxylate (pKa 4.5) and a protonated group (pKa 6.7) as does the pH-profile for hydrolysis of the corresponding O-glycoside. Not surprisingly, in spite of the requirement for the presence of this protonated group in catalytically active β-glucosidase, thioglucoside hydrolysis does not involve general acid catalysis. There is no solvent kinetic isotope effect on the enzyme-catalyzed hydrolysis of pNPSG

  3. Gallium-Catalyzed Silicon Oxide Nanowire Growth

    Institute of Scientific and Technical Information of China (English)

    Zheng Wei Pan; Sheng Dai; Douglas H.Lowndes

    2005-01-01

    Silicon oxide nanowires tend to assemble into various complex morphologies through a metalcatalyzed vapor-liquid-solid (VLS) growth process. This article summarizes our recent efforts in the controlled growth of silicon oxide nanowire assemblies by using molten gallium as the catalyst and silicon wafer,SiO powder, or silane (SiH4) as the silicon sources. Silicon oxide nanowire assemblies with morphologies of carrotlike, cometlike, gourdlike, spindlelike, badmintonlike, sandwichlike, etc. were obtained. Although the morphologies of the nanowire assemblies are temperature- and silicon source-dependent, they share similar structural and compositional features: all the assemblies contain a microscale spherical liquid Ga ball and a highly aligned, closely packed amorphous silicon oxide nanowire bunch. The Ga-catalyzed silicon oxide nanowire growth reveals several interesting new nanowire growth phenomena that expand our knowledge of the conventional VLS nanowire growth mechanism.

  4. Direct conversion of muon catalyzed fusion energy

    International Nuclear Information System (INIS)

    In this paper a method of direct conversion of muon catalyzed fusion (MCF) energy is proposed in order to reduce the cost of muon production. This MCF concept is based on a pellet composed of many thin solid deuterium-tritium (DT) rods encircled by a metallic circuit immersed in a magnetic field. The direct energy conversion is the result of the heating of the pellet by beam injection and fusion alphas. The expanding DT rods causes the change of magnetic flux linked by the circuit. Our calculation shows that the direct conversion method reduces the cost of one muon by a factor of approximately 2.5 over the previous methods. The present method is compatible with a reactor using the pellet concept, where the muon sticking is reduced by the ion cyclotron resonance heating and the confinement of the exploding pellet is handled by magnetic fields and the coronal plasma. 17 refs., 6 figs

  5. Heterogeneously Catalyzed Oxidation Reactions Using Molecular Oxygen

    DEFF Research Database (Denmark)

    Beier, Matthias Josef

    Heterogeneously catalyzed selective oxidation reactions have attracted a lot of attention in recent time. The first part of the present thesis provides an overview over heterogeneous copper and silver catalysts for selective oxidations in the liquid phase and compared the performance and catalytic...... that both copper and silver can function as complementary catalyst materials to gold showing different catalytic properties and being more suitable for hydrocarbon oxidation reactions. Potential opportunities for future research were outlined. In an experimental study, the potential of silver as a...... properties to the widely discussed gold catalysts. Literature results were summarized for alcohol oxidation, epoxidation, amine oxidation, phenol hydroxylation, silane and sulfide oxidation, (side-chain) oxidation of alkyl aromatic compounds, hydroquinone oxidation and cyclohexane oxidation. It was found...

  6. Enzyme-catalyzed degradation of carbon nanomaterials

    Science.gov (United States)

    Kotchey, Gregg P.

    Carbon nanotubes and graphene, the nanoscale sp 2 allotropes of carbon, have garnered widespread attention as a result of their remarkable electrical, mechanical, and optical properties and the promise of new technologies that harness these properties. Consequently, these carbon nanomaterials (CNMs) have been employed for diverse applications such as electronics, sensors, composite materials, energy conversion devices, and nanomedicine. The manufacture and eventual disposal of these products may result in the release of CNMs into the environment and subsequent exposure to humans, animals, and vegetation. Given the possible pro-inflammatory and toxic effects of CNMs, much attention has been focused on the distribution, toxicity, and persistence of CNMs both in living systems and the environment. This dissertation will guide the reader though recent studies aimed at elucidating fundamental insight into the persistence of CNMs such as carbon nanotubes (CNTs) and graphene derivatives (i.e., graphene oxide and reduced graphene oxide). In particular, in-testtube oxidation/degradation of CNMs catalyzed by peroxidase enzymes will be examined, and the current understanding of the mechanisms underlying these processes will be discussed. Finally, an outlook of the current field including in vitro and in vivo biodegradation experiments, which have benefits in terms of human health and environmental safety, and future directions that could have implications for nanomedical applications such as imaging and drug delivery will be presented. Armed with an understanding of how and why CNMs undergo enzyme-catalyzed oxidation/biodegradation, researchers can tailor the structure of CNMs to either promote or inhibit these processes. For example, in nanomedical applications such as drug delivery, the incorporation of carboxylate functional groups could facilitate biodegradation of the nanomaterial after delivery of the cargo. Also, the incorporation of CNMs with defect sites in consumer

  7. Sonogashira Reaction of Aryl and Heteroaryl Halides with Terminal Alkynes Catalyzed by a Highly Efficient and Recyclable Nanosized MCM-41 Anchored Palladium Bipyridyl Complex

    Directory of Open Access Journals (Sweden)

    Chung-Yuan Mou

    2010-12-01

    Full Text Available A heterogeneous catalyst, nanosized MCM-41-Pd, was used to catalyze the Sonogashira coupling of aryl and heteroaryl halides with terminal alkynes in the presence of CuI and triphenylphosphine. The coupling products were obtained in high yields using low Pd loadings to 0.01 mol%, and the nanosized MCM-41-Pd catalyst was recovered by centrifugation of the reaction solution and re-used in further runs without significant loss of reactivity.

  8. Sonogashira Reaction of Aryl and Heteroaryl Halides with Terminal Alkynes Catalyzed by a Highly Efficient and Recyclable Nanosized MCM-41 Anchored Palladium Bipyridyl Complex

    OpenAIRE

    Chung-Yuan Mou; Fu-Yu Tsai; Wei-Yi Wu; Shao-Hsien Huang; Bo-Nan Lin

    2010-01-01

    A heterogeneous catalyst, nanosized MCM-41-Pd, was used to catalyze the Sonogashira coupling of aryl and heteroaryl halides with terminal alkynes in the presence of CuI and triphenylphosphine. The coupling products were obtained in high yields using low Pd loadings to 0.01 mol%, and the nanosized MCM-41-Pd catalyst was recovered by centrifugation of the reaction solution and re-used in further runs without significant loss of reactivity.

  9. Palladium-Catalyzed Carbonylation of (Hetero)Aryl, Alkenyl and Allyl Halides by Means of N-Hydroxysuccinimidyl Formate as CO Surrogate.

    Science.gov (United States)

    Barré, Anaïs; Ţînţaş, Mihaela-Liliana; Alix, Florent; Gembus, Vincent; Papamicaël, Cyril; Levacher, Vincent

    2015-07-01

    An efficient Pd-catalyzed carbonylation protocol is described for the coupling of a large panel of aryl, heteroaryl, benzyl, vinyl and allyl halides 2 with the unusual N-hydroxysuccinimidyl (NHS) formate 1 as a CO surrogate to afford the corresponding valuable NHS esters 3. High conversion to the coupling products was achieved with up to 98% yield by means of Pd(OAc)2/Xantphos catalyst system. PMID:26098725

  10. Coupling oxygen consumption with hydrocarbon oxidation in bacterial multicomponent monooxygenases

    OpenAIRE

    Wang, Weixue; Liang, Alexandria D.; Lippard, Stephen J.

    2015-01-01

    A fundamental goal in catalysis is the coupling of multiple reactions to yield a desired product. Enzymes have evolved elegant approaches to address this grand challenge. A salient example is the biological conversion of methane to methanol catalyzed by soluble methane monooxygenase (sMMO), a member of the bacterial multicomponent monooxygenase (BMM) superfamily.

  11. Total Synthesis of Chiral Biaryl Natural Products by Asymmetric Biaryl Coupling

    OpenAIRE

    Kozlowski, Marisa C.; Morgan, Barbara J.; Linton, Elizabeth C.

    2009-01-01

    This tutorial review highlights the use of catalytic asymmetric 2-naphthol couplings in total synthesis. The types of chirality, chiral biaryl natural products, prior approaches to chiral biaryl natural products, and other catalytic asymmetric biaryl couplings are outlined. The three main categories of chiral catalysts for 2-naphthol coupling (Cu, V, Fe) are described with discussion of their limitations and advantages. Applications of the copper catalyzed couplings in biomimetic syntheses ar...

  12. Carbon Isotope Measurements of Experimentally-Derived Hydrothermal Mineral-Catalyzed Organic Products by Pyrolysis-Isotope Ratio Mass Spectrometry

    Science.gov (United States)

    Socki, Richard A.; Fu, Qi; Niles, Paul B.

    2011-01-01

    We report results of experiments to measure the C isotope composition of mineral catalyzed organic compounds derived from high temperature and high pressure synthesis. These experiments make use of an innovative pyrolysis technique designed to extract and measure C isotopes. To date, our experiments have focused on the pyrolysis and C isotope ratio measurements of low-molecular weight intermediary hydrocarbons (organic acids and alcohols) and serve as a proof of concept for making C and H isotope measurements on more complicated mixtures of solid-phase hydrocarbons and intermediary products produced during high temperature and high pressure synthesis on mineral-catalyzed surfaces. The impetus for this work stems from recently reported observations of methane detected within the Martian atmosphere [1-4], coupled with evidence showing extensive water-rock interaction during Martian history [5-7]. Methane production on Mars could be the result of synthesis by mineral surface-catalyzed reduction of CO2 and/or CO by Fischer-Tropsch Type (FTT) reactions during serpentization reactions [8,9]. Others have conducted experimental studies to show that FTT reactions are plausible mechanisms for low-molecular weight hydrocarbon formation in hydrothermal systems at mid-ocean ridges [10-12]. Further, recent experiments by Fu et al. [13] focus on examining detailed C isotope measurements of hydrocarbons produced by surface-catalyzed mineral reactions. Work described in this paper details the experimental techniques used to measure intermediary organic reaction products (alcohols and organic acids).

  13. Lipase-catalyzed process in an anhydrous medium with enzyme reutilization to produce biodiesel with low acid value.

    Science.gov (United States)

    Azócar, Laura; Ciudad, Gustavo; Heipieper, Hermann J; Muñoz, Robinson; Navia, Rodrigo

    2011-12-01

    One major problem in the lipase-catalyzed production of biodiesel or fatty acid methyl esters (FAME) is the high acidity of the product, mainly caused by water presence, which produces parallel hydrolysis and esterification reactions instead of transesterification to FAME. Therefore, the use of reaction medium in absence of water (anhydrous medium) was investigated in a lipase-catalyzed process to improve FAME yield and final product quality. FAME production catalyzed by Novozym 435 was carried out using waste frying oil (WFO) as raw material, methanol as acyl acceptor, and 3Å molecular sieves to extract the water. The anhydrous conditions allowed the esterification of free fatty acids (FFA) from feedstock at the initial reaction time. However, after the initial esterification process, water absence avoided the consecutives reactions of hydrolysis and esterification, producing FAME mainly by transesterification. Using this anhydrous medium, a decreasing in both the acid value and the diglycerides content in the product were observed, simultaneously improving FAME yield. Enzyme reuse in the anhydrous medium was also studied. The use of the moderate polar solvent tert-butanol as a co-solvent led to a stable catalysis using Novozym 435 even after 17 successive cycles of FAME production under anhydrous conditions. These results indicate that a lipase-catalyzed process in an anhydrous medium coupled with enzyme reuse would be suitable for biodiesel production, promoting the use of oils of different origin as raw materials. PMID:21889401

  14. 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.

  15. Vinyl Tris(trimethylsilyl)silanes: Substrates for Hiyama Coupling

    OpenAIRE

    WANG, ZHIZHONG; Pitteloud, Jean-Philippe; Montes, Lucresia; Rapp, Magdalena; Derane, Djenny; Wnuk, Stanislaw F.

    2008-01-01

    The oxidative treatment of vinyl tris(trimethylsilyl)silanes with hydrogen peroxide in aqueous sodium hydroxide in tetrahydrofuran generates reactive silanol or siloxane species that undergo Pd-catalyzed cross-couplings with aryl, heterocyclic and alkenyl halides in the presence of Pd(PPh3)4 and tetrabutylammonium fluoride. Hydrogen peroxide and base are necessary for the coupling to occur while activation of the silanes with fluoride is not required. The conjugated and unconjugated tris(trim...

  16. Elucidation of Mechanisms and Selectivities of Metal-Catalyzed Reactions using Quantum Chemical Methodology.

    Science.gov (United States)

    Santoro, Stefano; Kalek, Marcin; Huang, Genping; Himo, Fahmi

    2016-05-17

    Quantum chemical techniques today are indispensable for the detailed mechanistic understanding of catalytic reactions. The development of modern density functional theory approaches combined with the enormous growth in computer power have made it possible to treat quite large systems at a reasonable level of accuracy. Accordingly, quantum chemistry has been applied extensively to a wide variety of catalytic systems. A huge number of problems have been solved successfully, and vast amounts of chemical insights have been gained. In this Account, we summarize some of our recent work in this field. A number of examples concerned with transition metal-catalyzed reactions are selected, with emphasis on reactions with various kinds of selectivities. The discussed cases are (1) copper-catalyzed C-H bond amidation of indoles, (2) iridium-catalyzed C(sp(3))-H borylation of chlorosilanes, (3) vanadium-catalyzed Meyer-Schuster rearrangement and its combination with aldol- and Mannich-type additions, (4) palladium-catalyzed propargylic substitution with phosphorus nucleophiles, (5) rhodium-catalyzed 1:2 coupling of aldehydes and allenes, and finally (6) copper-catalyzed coupling of nitrones and alkynes to produce β-lactams (Kinugasa reaction). First, the methodology adopted in these studies is presented briefly. The electronic structure method in the great majority of these kinds of mechanistic investigations has for the last two decades been based on density functional theory. In the cases discussed here, mainly the B3LYP functional has been employed in conjunction with Grimme's empirical dispersion correction, which has been shown to improve the calculated energies significantly. The effect of the surrounding solvent is described by implicit solvation techniques, and the thermochemical corrections are included using the rigid-rotor harmonic oscillator approximation. The reviewed examples are chosen to illustrate the usefulness and versatility of the adopted methodology in

  17. Mechanisms of bacterially catalyzed reductive dehalogenation

    Energy Technology Data Exchange (ETDEWEB)

    Picardal, F.W.

    1992-12-31

    Nine bacteria were tested for the ability to dehalogenate tetrachloromethane (CT), tetrachloroethene (PCE), and 1, 1, 1-trichloroethane (TCA) under anaerobic conditions. Three bacteria were able to reductively dehalogenate CT. Dehalogenation ability was not readily linked to a common metabolism or changes in culture redox potential. None of the bacteria tested were able to dehalogenate PCE or TCA. One of the bacteria capable of dehalogenating CT, Shewanella putrefaciens, was chosen as a model organism to study mechanisms of bacterially catalyzed reductive dehalogenation. The effect of a variety of alternate electron acceptors on CT dehalogenation ability by S. putrefaciens was determined. oxygen and nitrogen oxides were inhibitory but Fe (III), trimethylamine oxide, and fumarate were not. A model of the electron transport chain of S. putrefaciens was developed to explain inhibition patterns. A period of microaerobic growth prior to CT exposure increased the ability of S. putrefaciens to dehalogenate CT. A microaerobic growth period also increased cytochrome concentrations. A relationship between cytochrome content and dehalogenation ability was developed from studies in which cytochrome concentrations in S. putrefaciens were manipulated by changing growth conditions. Stoichiometry studies using {sup 14}C-CT suggested that CT was first reduced to form a trichloromethyl radical. Reduction of the radical to produce chloroform and reaction of the radical with cellular biochemicals explained observed product distributions. Carbon dioxide or other fully dehalogenated products were not found.

  18. Horseradish peroxidase catalyzed hydroxylations: mechanistic studies.

    Science.gov (United States)

    Dordick, J S; Klibanov, A M; Marletta, M A

    1986-05-20

    The hydroxylation of phenol to hydroquinone and catechol in the presence of dihydroxyfumaric acid and oxygen catalyzed by horseradish peroxidase was studied under conditions where the product yield was high and the side reactions were minimal. The reaction is partially uncoupled with a molar ratio of dihydroxyfumaric acid consumed to hydroxylated products of 12:1. Hydrogen peroxide does not participate in the reaction as evidenced by the lack of effect of catalase and by the direct addition of hydrogen peroxide. Conversely, superoxide and hydroxyl radicals are involved as their scavengers are potent inhibitors. Experiments were all consistent with the involvement of compound III (oxygenated ferrous complex) of peroxidase in the reaction. Compound III is stable in the presence of phenol alone but decomposes rapidly in the presence of both phenol and dihydroxyfumaric acid with the concomitant formation of product. Therefore, phenol and dihydroxyfumaric acid must be present with compound III in order for the hydroxylation reaction to occur. A mechanism consistent with the experimental results is proposed. PMID:3718931

  19. Stereoselective Palladium Catalyzed Cyclizations of Enediyne Compounds

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Chang Ho; Rhim, Chul Yun; Jung, Hyung Hoon; Jung, Seung Hyun [Hanyang University, Seoul (Korea, Republic of)

    1999-06-15

    Hydropalladium carboxylates, formed from {pi}-allylpalladium chloride dimer plus carboxylic acids, have been shown to catalyze cyclization of structurally diverse enediynes to form the corresponding six- or five-membered rings depending upon the reaction conditions. Some enediynes having an oxygen linker in an appropriate position under the similar condition yielded the corresponding cyclopropanation products in highly stereoselective manner. A study using deuterated formic acid has proven that the alkylpalladium intermediates formed in our conditions were reduced by the pendant formate ligand. The dienediyne 10 yielded only the tricyclic product 12 in 67% yield, although it was expected to form the cyclic product 11. All these cyclizations seemed to occur via the corresponding alkylpalladium intermediates I, which could proceed to the corresponding cyclic products depending on the reaction conditions and the substrates. The study using deuterated formic acid could provide an important information to understand the present cyclization mechanism. Overall the present study could play an important role in developing new synthetic methodologies for constructing complex polycyclic compounds

  20. Optical coupling

    Energy Technology Data Exchange (ETDEWEB)

    Bock, J J [Jet Propulsion Laboratory, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Gundersen, J [Department of Physics, University of Miami, Coral Gables, FL 33146 (United States); Lee, A T [Department of Physics, University of California, Berkeley CA 94720 Physics Division, Lawrence Berkeley National Laboratory, Berkeley CA 94720 (United States); Richards, P L [Department of Physics, University of California, Berkeley CA 94720 (United States); Wollack, E, E-mail: James.Bock@jpl.nasa.go, E-mail: gunder@physics.miami.ed, E-mail: Adrian.Lee@berkeley.ed, E-mail: Richards@cosmology.berkeley.ed, E-mail: Edward.j.wollack@nasa.go [Observational Cosmology Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States)

    2009-03-01

    This paper describes contributions to the CMBpol Technology Study Workshop concerning optical coupling structures. These are structures in or near the focal plane which convert the free space wave to a superconducting microstrip on a SI wafer, or to the waveguide input to a HEMT receiver. In addition to an introduction and conclusions by the editor, this paper includes independent contributions by Bock on 'Planar Antenna-Coupled Bolometers for CMB Polarimetry', by Gunderson and Wollack on 'Millimeter-Wave Platlet Feeds', and by Lee on 'Multi-band Dual-Polarization Lens-coupled Planar Antennas for Bolometric CMB polarimetry.'

  1. Lipase catalyzed synthesis of epoxy-fatty acids

    Institute of Scientific and Technical Information of China (English)

    CHEN, Qian; LI, Zu-Yi

    2000-01-01

    Lipase catalyzed synthesis of epoxy-fatty acidas from unsaturated carboxylic acids was investigated.Under mild conditions unsaturated arboxylic acids were convcveed to peroxide,then the unsaturated peroxycarboxylic acids epoxidised the C=C bond of themselves

  2. Functioned Calix[4]arenes as Artificial Enzymes Catalyze Aldol Condensation

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Aldolase models derived from calix[4]arene were designed and synthesized. The aldol condensation of p-nitrobenzaldehyde with acetone was catalyzed by the synthetic enzymes proceeded under mild conditions to offer chiefly aldol-type product in good yield.

  3. Amino Acids Catalyzed Direct Aldol Reactions in Aqueous Micelles

    Institute of Scientific and Technical Information of China (English)

    PENG Yi-Yuan; WANG Qi; DING Qiu-Ping; HE Jia-Qi; CHENG Jin-Pei

    2003-01-01

    @@ Since the discovery of its roles as a good small-organic-molecule catalyst in intramolecular aldol reactions, pro line has drawn considerable attention in synthetic chemistry due to its similarity to the type-Ⅰ aldolases. Recently,List and others have reported some new direct asymmetric intermolecular reactions catalyzed by proline, including aldol, Mannich, Michael, and other analogous reactions. Except for two recent examples, [1,2] proline catalyzed aldol reactions in aqueous micelles have not been reported, nor have other amino acids as organocatalysts in directly catalyzing aldol reaction been reported. Herein we wish to present our recent results regarding environmentally be nign direct aldol reactions catalyzed by amino acids including proline, histidine and arginine in aqueous media.

  4. The Iron-Catalyzed Oxidation of Hydrazine by Nitric Acid

    Energy Technology Data Exchange (ETDEWEB)

    Karraker, D.G.

    2001-07-17

    To assess the importance of iron to hydrazine stability, the study of hydrazine oxidation by nitric acid has been extended to investigate the iron-catalyzed oxidation. This report describes those results.

  5. Heterocycles via intramolecular platinum-catalyzed propargylic substitution

    OpenAIRE

    Liang, Qiren; De Brabander, Jef K

    2011-01-01

    We report a Pt(II)-catalyzed cyclization of nucleophile-tethered propargylic acetates yielding substituted heterocycles containing multiple heteroatoms including morpholines, dioxanes and sulfamates with high cis-selectivity.

  6. Muon-catalyzed fusion-an energy production perspective

    International Nuclear Information System (INIS)

    The nuclear fission reaction can be catalyzed in a suitable fusion fuel by muons, which can temporarily form very tightly bound mu-molecules. Muons can be produced by the decay of negative pions, which, in turn, have been produced by an accelerated beam of light ions impinging on a target. Muon-catalyzed fusion is appropriately called cold fusion because the nuclear fusion also occurs at room temperature. For practical fusion energy generation, it appears to be necessary to have a fuel mixture of deuterium and tritium at about liquid density and at a temperature of the order of 1000 K. The current status of muon-catalyzed fusion is limited to demonstrations of scientific breakeven by showing that it is possible to sustain an energy balance between muon production and catalyzed fusion. Conceptually, a muon-catalyzed fusion reactor is seen to be an energy amplifier that increases by fusion reactions that energy invested in nuclear pion-muon beams. The physical quantity that determines this balance is Xμ, the number of fusion reactions each muon can catalyze before it is lost. Showing the feasibility of useful power production is equivalent to showing that Xμ can exceed a sufficiently large number, which is estimated to be ∼104 if standard technology is used or ∼103 if more advanced physics and technology can be developed. Since a muon can be produced with current technology for an expenditure of ∼5000 MeV and 17.6 MeV is produced per fusion event, it follows that Xμ ∼ 250 would be a significant demonstration of scientific breakeven. Therefore, the energy cost of producing muons must be reduced substantially before muon-catalyzed fusion reactors could seriously be considered. The physics of muon-catalyzed fusion is summarized and discussed. Muon catalysis is surveyed for the following systems: proton-deuteron, deuteron-deuteron, deuteron-triton, and non-hydrogen elements. 95 refs., 6 figs., 4 tabs

  7. Branching Out: Rhodium-Catalyzed Allylation with Alkynes and Allenes.

    Science.gov (United States)

    Koschker, Philipp; Breit, Bernhard

    2016-08-16

    We present a new and efficient strategy for the atom-economic transformation of both alkynes and allenes to allylic functionalized structures via a Rh-catalyzed isomerization/addition reaction which has been developed in our working group. Our methodology thus grants access to an important structural class valued in modern organic chemistry for both its versatility for further functionalization and the potential for asymmetric synthesis with the construction of a new stereogenic center. This new methodology, inspired by mechanistic investigations by Werner in the late 1980s and based on preliminary work by Yamamoto and Trost, offers an attractive alternative to other established methods for allylic functionalization such as allylic substitution or allylic oxidation. The main advantage of our methodology consists of the inherent atom economy in comparison to allylic oxidation or substitution, which both produce stoichiometric amounts of waste and, in case of the substitution reaction, require prefunctionalization of the starting material. Starting out with the discovery of a highly branched-selective coupling reaction of carboxylic acids with terminal alkynes using a Rh(I)/DPEphos complex as the catalyst system, over the past 5 years we were able to continuously expand upon this chemistry, introducing various (pro)nucleophiles for the selective C-O, C-S, C-N, and C-C functionalization of both alkynes and the double-bond isomeric allenes by choosing the appropriate rhodium/bidentate phosphine catalyst. Thus, valuable compounds such as branched allylic ethers, sulfones, amines, or γ,δ-unsaturated ketones were successfully synthesized in high yields and with a broad substrate scope. Beyond the branched selectivity inherent to rhodium, many of the presented methodologies display additional degrees of selectivity in regard to regio-, diastereo-, and enantioselective transformations, with one example even proceeding via a dynamic kinetic resolution. Many advances

  8. Conservation Kickstart- Catalyzing Conservation Initiatives Worldwide

    Science.gov (United States)

    Treinish, G.

    2014-12-01

    Adventurers and Scientists for Conservation (ASC) is a nonprofit organization that collects environmental data to catalyze conservation initiatives worldwide. Adventure athletes have the skills and motivation to reach the most remote corners of the world. ASC utilizes those skills to provide the scientific community with data while providing the outdoor community with purpose beyond the personal high of reaching a summit or rowing across an ocean. We carefully select projects, choosing partnerships that will maximize the impact of ASC volunteers. Each project must have a clear path to a tangible conservation outcome and demonstrate a clear need for our brand of volunteers. We partner with government agencies, universities, and independant reseachers to kickstart data collection efforts around the world. Last year, through a partnership with the Olympic National Forest, 20 volunteers from the Seattle area set up and monitored camera traps in an effort to survey for costal Pacific marten. Our work led to the species' listing as "critically imperiled" with NatureServe. A partnership with the inaugural Great Pacific Race, engaging trans-Pacific rowing teams, searched for microplastics in the Pacific Ocean as part of our ongoing microplastics campaign. In a multi-year partnership with the American Prairie Reserve (APR), ASC volunteer crews live and work on the Reserve collecting wildlife data year round. The data we obtain directly informs the Reserve's wildlife management decisions. On this project, our crews have safely and effectively navigated temperature extremes from -30 degrees to 100+ degrees while traveling in a remote location. We are currently scouting projects in the Okavango Delta of Botswana and the rainforest of Suriname where we will be able to cover large amounts of area in a short periord of time. ASC is at the crossroads of the adventure and coservation science communities. Our approach of answering specific questions by using highly skilled and

  9. Prosthesis coupling

    Science.gov (United States)

    Reswick, J. B.; Mooney, V.; Bright, C. W.; Owens, L. J. (Inventor)

    1979-01-01

    A coupling for use in an apparatus for connecting a prosthesis to the bone of a stump of an amputated limb is described which permits a bio-compatible carbon sleeve forming a part of the prosthesis connector to float so as to prevent disturbing the skin seal around the carbon sleeve. The coupling includes a flexible member interposed between a socket that is inserted within an intermedullary cavity of the bone and the sleeve. A lock pin is carried by the prosthesis and has a stem portion which is adapted to be coaxially disposed and slideably within the tubular female socket for securing the prosthesis to the stump. The skin around the percutaneous carbon sleeve is able to move as a result of the flexing coupling so as to reduce stresses caused by changes in the stump shape and/or movement between the bone and the flesh portion of the stump.

  10. Entrepreneurial Couples

    DEFF Research Database (Denmark)

    Dahl, Michael S.; Van Praag, Mirjam; Thompson, Peter

    We study possible motivations for co-entrepenurial couples to start up a joint firm, using a sample of 1,069 Danish couples that established a joint enterprise between 2001 and 2010. We compare their pre-entry characteristics, firm performance and postdissolution private and financial outcomes with......, are larger in co-entrepreneurial firms, both during the life of the business and post-dissolution. The start-up of co-entrepreneurial firms seems therefore a sound investment in the human capital of both spouses as well as in the reduction of income inequality in the household. We find no evidence of...

  11. Entrepreneurial Couples

    DEFF Research Database (Denmark)

    Dahl, Michael S.; Van Praag, Mirjam; Thompson, Peter

    We study possible motivations for co-entrepenurial couples to start up a joint firm, us-ing a sample of 1,069 Danish couples that established a joint enterprise between 2001 and 2010. We compare their pre-entry characteristics, firm performance and post-dissolution private and financial outcomes...... female, are larger in co-entrepreneurial firms, both during the life of the business and post-dissolution. The start-up of co-entrepreneurial firms seems therefore a sound in-vestment in the human capital of both spouses as well as in the reduction of income inequality in the household. We find no...

  12. Entrepreneurial Couples

    DEFF Research Database (Denmark)

    2015-01-01

    We study possible motivations for co-entreprenurial couples to start up a joint firm, using a sample of 1,069 Danish couples that established a joint enterprise between 2001 and 2010. We compare their pre-entry characteristics, firm performance and post-dissolution private and financial outcomes...... female, are larger in co-entrepreneurial firms, both during the life of the business and post-dissolution. The start-up of co-entrepreneurial firms seems therefore a sound investment in the human capital of both spouses as well as in the reduction of income inequality in the household. We find no...

  13. Inhibitory effect of water on the oxygen reduction catalyzed by cobalt(II) tetraphenylporphyrin.

    Science.gov (United States)

    Trojánek, Antonín; Langmaier, Jan; Kvapilová, Hana; Záliš, Stanislav; Samec, Zdeněk

    2014-03-20

    Stopped-flow kinetic measurements, UV-vis spectroscopy, rotating disk voltammetry, and quantum chemical calculations are used to clarify the role of water in the homogeneous two-electron reduction of O2 to H2O2 in 1,2-dichloroethane (DCE) using ferrocene (Fc) as an electron donor, tetrakis(pentafluorophenyl)boric acid (HTB) as a proton donor, and [5,10,15,20-tetraphenyl-21H,23H-porphine]cobalt(II) (Co(II)TTP) as a catalyst. Kinetic analysis suggests that the reaction is controlled by the intramolecular proton coupled electron transfer to the O2 molecule coordinated to the metal center producing the O2H(•) radical. This rate-determining step is common to both the O2 reduction by Fc catalyzed by Co(II)TPP and the O2 reduction by Co(II)TPP itself. Experimental data point to the competitive coordination of water to the metal center leading to a strong inhibition of the catalytic reaction. In agreement with this finding, quantum chemical calculations indicate that water is bound to the metal center much more strongly than triplet O2. A similar effect is demonstrated also for the O2 reduction catalyzed by the porphyrin free base (H2TPP), though its rate is lower by 2 orders of magnitude. PMID:24564521

  14. In situ Regeneration of NADH via Lipoamide Dehydrogenase-catalyzed Electron Transfer Reaction Evidenced by Spectroelectrochemistry

    Energy Technology Data Exchange (ETDEWEB)

    Tam, Tsz Kin; Chen, Baowei; Lei, Chenghong; Liu, Jun

    2012-08-01

    NAD/NADH is a coenzyme found in all living cells, carrying electrons from one reaction to another. We report on characterizations of in situ regeneration of NADH via lipoamide dehydrogenase (LD)-catalyzed electron transfer reaction to regenerate NADH using UV-vis spectroelectrochemistry. The Michaelis-Menten constant (Km) and maximum velocity (Vmax) of NADH regeneration were measured as 0.80 {+-} 0.15 mM and 1.91 {+-} 0.09 {micro}M s-1 in a 1-mm thin-layer spectroelectrochemical cell using gold gauze as the working electrode at the applied potential -0.75 V (vs. Ag/AgCl). The electrocatalytic reduction of the NAD system was further coupled with the enzymatic conversion of pyruvate to lactate by lactate dehydrogenase to examine the coenzymatic activity of the regenerated NADH. Although the reproducible electrocatalytic reduction of NAD into NADH is known to be difficult compared to the electrocatalytic oxidation of NADH, our spectroelectrochemical results indicate that the in situ regeneration of NADH via LD-catalyzed electron transfer reaction is fast and sustainable and can be potentially applied to many NAD/NADH-dependent enzyme systems.

  15. Recent Advances of Modern Protocol for C-C Bonds—The Suzuki Cross-Coupling

    OpenAIRE

    Jadwiga Sołoducho; Kamila Olech; Agnieszka Świst; Dorota Zając; Joanna Cabaj

    2013-01-01

    Over the past 20 years, small molecule solid phase synthesis has become a powerful tool in the discovery of novel molecular materials. In the development of organic chemistry, the carbon-carbon bond formation has always been one of the most useful and fundamental reaction. The current review summarizes recent developments in metal-catalyzed coupling reactions. The following method is discussed in detail—the cross-coupling of aryl halides with aryl boronic acids (the Suzuki coupling), and the...

  16. The Structural Basis of Ribozyme-Catalyzed RNA Assembly

    Energy Technology Data Exchange (ETDEWEB)

    Robertson, M.P.; Scott, W.G.; /UC, Santa Cruz

    2007-07-12

    Life originated, according to the RNA World hypothesis, from self-replicating ribozymes that catalyzed ligation of RNA fragments. We have solved the 2.6 angstrom crystal structure of a ligase ribozyme that catalyzes regiospecific formation of a 5' to 3' phosphodiester bond between the 5'-triphosphate and the 3'-hydroxyl termini of two RNA fragments. Invariant residues form tertiary contacts that stabilize a flexible stem of the ribozyme at the ligation site, where an essential magnesium ion coordinates three phosphates. The structure of the active site permits us to suggest how transition-state stabilization and a general base may catalyze the ligation reaction required for prebiotic RNA assembly.

  17. New Palladium-Catalyzed Approaches to Heterocycles and Carbocycles

    Energy Technology Data Exchange (ETDEWEB)

    Qinhua Huang

    2004-12-19

    The tert-butylimines of o-(1-alkynyl)benzaldehydes and analogous pyridinecarbaldehydes have been cyclized under very mild reaction conditions in the presence of I{sub 2}, ICl, PhSeCl, PhSCl and p-O{sub 2}NC{sub 6}H{sub 4}SCl to give the corresponding halogen-, selenium- and sulfur-containing disubstituted isoquinolines and naphthyridines, respectively. Monosubstituted isoquinolines and naphthyridines have been synthesized by the metal-catalyzed ring closure of these same iminoalkynes. This methodology accommodates a variety of iminoalkynes and affords the anticipated heterocycles in moderate to excellent yields. The Pd(II)-catalyzed cyclization of 2-(1-alkynyl)arylaldimines in the presence of various alkenes provides an efficient way to synthesize a variety of 4-(1-alkenyl)-3-arylisoquinolines in moderate to excellent yields. The introduction of an ortho-methoxy group on the arylaldimine promotes the Pd-catalyzed cyclization and stabilizes the resulting Pd(II) intermediate, improving the yields of the isoquinoline products. Highly substituted naphthalenes have been synthesized by the palladium-catalyzed annulation of a variety of internal alkynes, in which two new carbon-carbon bonds are formed in a single step under relatively mild reaction conditions. This method has also been used to synthesize carbazoles, although a higher reaction temperature is necessary. The process involves arylpalladation of the alkyne, followed by intramolecular Heck olefination and double bond isomerization. This method accommodates a variety of functional groups and affords the anticipated highly substituted naphthalenes and carbazoles in good to excellent yields. Novel palladium migratiodarylation methodology for the synthesis of complex fused polycycles has been developed, in which one or more sequential Pd-catalyzed intramolecular migration processes involving C-H activation are employed. The chemistry works best with electron-rich aromatics, which is in agreement with the idea that

  18. Nickel-Catalyzed Aromatic C-H Functionalization.

    Science.gov (United States)

    Yamaguchi, Junichiro; Muto, Kei; Itami, Kenichiro

    2016-08-01

    Catalytic C-H functionalization using transition metals has received significant interest from organic chemists because it provides a new strategy to construct carbon-carbon bonds and carbon-heteroatom bonds in highly functionalized, complex molecules without pre-functionalization. Recently, inexpensive catalysts based on transition metals such as copper, iron, cobalt, and nickel have seen more use in the laboratory. This review describes recent progress in nickel-catalyzed aromatic C-H functionalization reactions classified by reaction types and reaction partners. Furthermore, some reaction mechanisms are described and cutting-edge syntheses of natural products and pharmaceuticals using nickel-catalyzed aromatic C-H functionalization are presented. PMID:27573407

  19. Graphene oxide catalyzed cis-trans isomerization of azobenzene

    Directory of Open Access Journals (Sweden)

    Dongha Shin

    2014-09-01

    Full Text Available We report the fast cis-trans isomerization of an amine-substituted azobenzene catalyzed by graphene oxide (GO, where the amine functionality facilitates the charge transfer from azobenzene to graphene oxide in contrast to non-substituted azobenzene. This catalytic effect was not observed in stilbene analogues, which strongly supports the existence of different isomerization pathways between azobenzene and stilbene. The graphene oxide catalyzed isomerization is expected to be useful as a new photoisomerization based sensing platform complementary to GO-based fluorescence quenching methods.

  20. Molecular Mechanism by which One Enzyme Catalyzes Two Reactions

    Science.gov (United States)

    Nishimasu, Hiroshi; Fushinobu, Shinya; Wakagi, Takayoshi

    Unlike ordinary enzymes, fructose-1,6-bisphosphate (FBP) aldolase/phosphatase (FBPA/P) catalyzes two distinct reactions : (1) the aldol condensation of dihydroxyacetone phosphate (DHAP) and glyceraldehyde-3-phosphate to FBP, and (2) the dephosphorylation of FBP to fructose-6-phosphate. We solved the crystal structures of FBPA/P in complex with DHAP (its aldolase form) and FBP (its phosphatase form). The crystal structures revealed that FBPA/P exhibits the dual activities through a dramatic conformational change in the active-site architecture. Our findings expand the conventional concept that one enzyme catalyzes one reaction.

  1. Muon-catalyzed fusion theory: Introduction and review

    International Nuclear Information System (INIS)

    Muon-catalyzed fusion (μCF) has proved to be a fruitful subject for basic physics research as well as a source of cold nuclear fusion. Experiments have demonstrated that over 100 fusions per muon can be catalyzed by formation of the dtμ molecule in mixtures of deuterium and tritium. After a brief review of the subject's history, the dtμ catalysis cycle and the principal relations used in its analysis are described. Some of the important processes in the μCF cycle are then discussed. Finally, the status of current research is appraised. 52 refs., 7 figs

  2. The mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol

    Institute of Scientific and Technical Information of China (English)

    竹湘锋; 徐新华

    2004-01-01

    Fe (Ⅲ)-catalyzed ozonation yielded better degradation rate and extent of COD (Chemical Oxygen Demand) or oxalic acid as compared with oxidation by ozone alone. Two parameters with strong effects on the efficiency of ozonation are pH of the solution and the catalyst (Fe3+) dosage. The existence of a critical pH value determining the catalysis of Fe (Ⅲ) in acid conditions was observed in phenol and oxalic acid systems. The best efficiency of catalysis was obtained at a moderate concentration of the catalyst. A reasonable mechanism of Fe (Ⅲ)-catalyzed ozonation of phenol was obtained based on the results and literature.

  3. Power coupling

    OpenAIRE

    D. AlesiniLNF, INFN, Frascati

    2015-01-01

    Power coupling is the subject of a huge amount of literature and material since for each particular RF structure it is necessary to design a coupler that satisfies some requirements, and several approaches are in principle possible. The choice of one coupler with respect to another depends on the particular RF design expertise. Nevertheless some 'design criteria' can be adopted and the scope of this paper is to give an overview of the basic concepts in power coupler design and techniques. We ...

  4. X-ray photoelectron spectroscopy study of catalyzed aluminum carbide formation at aluminum-carbon interfaces

    Science.gov (United States)

    Rabenberg, L.; Maruyama, Benji

    1990-01-01

    Aluminum carbide may form at aluminum-graphite interfaces during the high-temperature processing of graphite fiber-reinforced aluminum metal matrix composites. The chemical interactions leading to the formation of the aluminum carbide in the solid state involve the breaking of the carbon-carbon bonds within the graphite, the transport of the carbon atoms across the interface, and the reaction with the aluminum to form Al4C3. The aluminum carbide formation process has been followed using X-ray photoelectron spectroscopy of model, thin-film, reaction couples. The overall reaction is shown to be catalyzed by the presence of water vapor. Water at the interface increases reaction kinetics by apparently weakening the bonds between the surface carbon atoms and their substrate. This result is in general agreement with what is known to occur during the oxidation of graphite in air.

  5. 水相钯催化Suzuki反应%Palladium-Catalyzed Suzuki Reaction in Aqueous Media

    Institute of Scientific and Technical Information of China (English)

    刘宁; 刘春; 金子林

    2012-01-01

    The palladium-catalyzed Suzuki cross-coupling reaction has become one of the most powerful tools for sp2-sp2 carbon-carbon bond formation. This coupling reaction is increasingly being applied in the synthesis of Pharmaceuticals, natural products and advanced functional materials. In recent years, developing aqueous systems for the Suzuki reaction has attracted attention from many researchers. This paper reviews the recent progress in the Suzuki reaction using neat water and aqueous-organic co-solvent as reaction media. A large number of different strategies for the Suzuki reaction in water have been developed, in which the authors aim at the solutions to the enhancement of the reactivity of the palladium-catalyzed Suzuki reaction using water-soluble ligands, surfactants, microwave assistance, or ligand-free system.%钯催化的Suzuki反应是构建Csp2-Csp2键的主要方法之一,已广泛应用于医药、天然产物及先进功能材料等联芳类化合物的合成.近年来,水相Suzuki反应引起了人们的高度关注.对以纯水及水/有机混溶剂为介质的水相Suzuki反应的研究进展作一综述,特别是围绕如何解决水相Suzuki反应活性的问题,以催化体系为主线,重点介绍了水溶性配体/钯、表面活性剂、微波促进的非水溶性配体/钯及无配体钯等催化体系在水相Suzuki反应中的应用.

  6. From a Sequential to a Concurrent Reaction in Aqueous Medium: Ruthenium-Catalyzed Allylic Alcohol Isomerization and Asymmetric Bioreduction.

    Science.gov (United States)

    Ríos-Lombardía, Nicolás; Vidal, Cristian; Liardo, Elisa; Morís, Francisco; García-Álvarez, Joaquín; González-Sabín, Javier

    2016-07-18

    The ruthenium-catalyzed redox isomerization of allylic alcohols was successfully coupled with the enantioselective enzymatic ketone reduction (mediated by KREDs) in a concurrent process in aqueous medium. The overall transformation, formally the asymmetric reduction of allylic alcohols, took place with excellent conversions and enantioselectivities, under mild reaction conditions, employing commercially and readily available catalytic systems, and without external coenzymes or cofactors. Optimization resulted in a multistep approach and a genuine cascade reaction where the metal catalyst and biocatalyst coexist from the beginning. PMID:27258838

  7. A Cell-Free Fluorometric High-Throughput Screen for Inhibitors of Rtt109-Catalyzed Histone Acetylation

    OpenAIRE

    Dahlin, Jayme L; Sinville, Rondedrick; Solberg, Jonathan; Zhou, Hui; Han, Junhong; Francis, Subhashree; Strasser, Jessica M.; John, Kristen; Hook, Derek J.; Walters, Michael A.; Zhang, Zhiguo

    2013-01-01

    The lysine acetyltransferase (KAT) Rtt109 forms a complex with Vps75 and catalyzes the acetylation of histone H3 lysine 56 (H3K56ac) in the Asf1-H3-H4 complex. Rtt109 and H3K56ac are vital for replication-coupled nucleosome assembly and genotoxic resistance in yeast and pathogenic fungal species such as Candida albicans. Remarkably, sequence homologs of Rtt109 are absent in humans. Therefore, inhibitors of Rtt109 are hypothesized as potential and minimally toxic antifungal agents. Herein, we ...

  8. CuO hollow nanosphere-catalyzed cross-coupling of aryl iodides with thiols

    OpenAIRE

    Woo, Hyunje; Mohan, Balaji; Heo, Eunjung; Park, Ji Chan; Song, Hyunjoon; Park, Kang Hyun

    2013-01-01

    New functionalized CuO hollow nanospheres on acetylene black (CuO/AB) and on charcoal (CuO/C) have been found to be effective catalysts for C-S bond formation under microwave irradiation. CuO catalysts showed high catalytic activity with a wide variety of substituents which include electron-rich and electron-poor aryl iodides with thiophenols by the addition of two equivalents of K2CO3 as base in the absence of ligands.

  9. Ruthenium-catalyzed self-coupling of primary and secondary alcohols with the liberation of dihydrogen

    DEFF Research Database (Denmark)

    Makarov, Ilya; Madsen, Robert

    2013-01-01

    The dehydrogenative self-condensation of primary and secondary alcohols has been studied in the presence of RuCl2(IiPr)(p-cymene). The conversion of primary alcohols into esters has been further optimized by using magnesium nitride as an additive, which allows the reaction to take place at a...... temperature and catalyst loading lower than those described previously. Secondary alcohols were dimerized into racemic ketones by a dehydrogenative Guerbet reaction with potassium hydroxide as the additive. The transformation gave good yields of the ketone dimers with a range of alkan-2-ols, whereas more...... substituted secondary alcohols were unreactive. The reaction proceeds by dehydrogenation to the ketone, followed by an aldol reaction and hydrogenation of the resulting enone. © 2013 American Chemical Society....

  10. Palladium-catalyzed cross-coupling: a historical contextual perspective to the 2010 Nobel Prize.

    Science.gov (United States)

    Johansson Seechurn, Carin C C; Kitching, Matthew O; Colacot, Thomas J; Snieckus, Victor

    2012-05-21

    In 2010, Richard Heck, Ei-ichi Negishi, and Akira Suzuki joined the prestigious circle of Nobel Laureate chemists for their roles in discovering and developing highly practical methodologies for C-C bond construction. From their original contributions in the early 1970s the landscape of the strategies and methods of organic synthesis irreversibly changed for the modern chemist, both in academia and in industry. In this Review, we attempt to trace the historical origin of these powerful reactions, and outline the developments from the seminal discoveries leading to their eminent position as appreciated and applied today. PMID:22573393

  11. Imidazole-2-ylidenes as Ligands for Palladium Catalyzed Heck Cross Coupling Reaction

    Institute of Scientific and Technical Information of China (English)

    CHEN Jing-Bo; LIU Jing-Ping; SHAO Zhi-Hui; LI Jie; ZHANG Hong-Bin

    2003-01-01

    @@ N-Heterocyclic carbenes have become universal ligands in coordination chemistry. [1] The design, synthesis, and application of imidazolium salts as precursors of imidazole-2-ylidenes are therefore of substantial interest. [2] The free carbenes with imidazole-2-ylidene structure of A (Scheme 1 ), so called "phosphine mimics", can form metal complexes with high thermal and hydrolytic durability, while N-substituted by different functional groups could produce, in principle, water-soluble; unsymmetrical; and immobilized catalysts. [3

  12. Stereospecific Ni-catalyzed cross-coupling of potassium alkenyltrifluoroborates with alkyl halides.

    Science.gov (United States)

    Molander, Gary A; Argintaru, O Andreea

    2014-04-01

    A general method for the alkenylation of alkyl electrophiles using nearly stoichiometric amounts of the air- and moisture-stable potassium organotrifluoroborates has been developed. Various functional groups were tolerated on both the nucleophilic and electrophilic partner. Reactions of highly substituted E- and Z-alkenyltrifluoroborates, as well as vinyl- and propenyltrifluoroborates, were successful, and no loss of stereochemistry or regiochemistry was observed. PMID:24666316

  13. Stereospecific Ni-Catalyzed Cross-Coupling of Potassium Alkenyltrifluoroborates with Alkyl Halides

    OpenAIRE

    Molander, Gary A.; Argintaru, O. Andreea

    2014-01-01

    A general method for the alkenylation of alkyl electrophiles using nearly stoichiometric amounts of the air- and moisture-stable potassium organotrifluoroborates has been developed. Various functional groups were tolerated on both the nucleophilic and electrophilic partner. Reactions of highly substituted E- and Z-alkenyltrifluoroborates, as well as vinyl- and propenyltrifluoroborates, were successful, and no loss of stereochemistry or regiochemistry was observed.

  14. Palladium(ii)-catalyzed C-C and C-O bond formation for the synthesis of C1-benzoyl isoquinolines from isoquinoline N-oxides and nitroalkenes.

    Science.gov (United States)

    Li, Jiu-Ling; Li, Wei-Ze; Wang, Ying-Chun; Ren, Qiu; Wang, Heng-Shan; Pan, Ying-Ming

    2016-08-01

    C1-Benzoyl isoquinolines can be generated via a palladium(ii)-catalyzed C-C and C-O coupling of isoquinoline N-oxides with aromatic nitroalkenes. The reaction proceeds through remote C-H bond activation and subsequent intramolecular oxygen atom transfer (OAT). In this reaction, the N-O bond was designed as a directing group in the C-H bond activation as well as the source of an oxygen atom. PMID:27443150

  15. Role of divalent metal cations in ATP hydrolysis catalyzed by the hepatitis C virus NS3 helicase: Magnesium provides a bridge for ATP to fuel unwinding

    OpenAIRE

    Frick, David N.; Banik, Sukalyani; Rypma, Ryan S.

    2006-01-01

    This study investigates the role of magnesium ions in coupling ATP hydrolysis to the nucleic acid unwinding catalyzed by the NS3 protein encoded by the hepatitis C virus. Analyses of steady-state ATP hydrolysis rates at various RNA and magnesium concentrations were used to determine values for the 15 dissociation constants describing the formation of a productive enzyme-metal-ATP-RNA complex and the 4 rate constants describing hydrolysis of ATP by the possible enzyme-ATP complexes. These valu...

  16. The facile synthesis of 1-benzoazepine derivatives via gold-catalyzed regioselective cycloisomerization reactions of N-(o-alkynylaryl)-N-vinyl sulfonamides.

    Science.gov (United States)

    Undeela, Sridhar; Ravikumar, Gurram; Nanubolu, Jagadeesh Babu; Singarapu, Kiran Kumar; Menon, Rajeev S

    2016-04-01

    Gold-catalyzed, regioselective cycloisomerization of N-(o-alkynylaryl)-N-vinyl sulfonamides afforded high yields of 2-sulfonylmethyl-1-benzoazepine derivatives. This 7-endo-dig selective cyclization proceeds via the incorporation of an exocyclic double bond by a labile 1-benzoazepine intermediate. The cyclization substrates were assembled in two steps from readily available materials using Sonogashira coupling and a Cs2CO3-mediated formal vinylic substitution. PMID:26964664

  17. Tubular Coupling

    Science.gov (United States)

    Rosenbaum, Bernard J. (Inventor)

    2000-01-01

    A system for coupling a vascular overflow graft or cannula to a heart pump. A pump pipe outlet is provided with an external tapered surface which receives the end of a compressible connula. An annular compression ring with a tapered internal bore surface is arranged about the cannula with the tapered internal surface in a facing relationship to the external tapered surface. The angle of inclination of the tapered surfaces is converging such that the spacing between the tapered surfaces decreases from one end of the external tapered surface to the other end thereby providing a clamping action of the tapered surface on a cannula which increases as a function of the length of cannula segment between the tapered surfaces. The annular compression ring is disposed within a tubular locking nut which threadedly couples to the pump and provides a compression force for urging the annular ring onto the cannula between the tapered surfaces. The nut has a threaded connection to the pump body. The threaded coupling to the pump body provides a compression force for the annular ring. The annular ring has an annular enclosure space in which excess cannula material from the compression between the tapered surfaces to "bunch up" in the space and serve as an enlarged annular ring segment to assist holding the cannula in place. The clamped cannula provides a seamless joint connection to the pump pipe outlet where the clamping force is uniformly applied to the cannula because of self alignment of the tapered surfaces. The nut can be easily disconnected to replace the pump if necessary.

  18. Recent developments in gold-catalyzed cycloaddition reactions

    Directory of Open Access Journals (Sweden)

    Fernando López

    2011-08-01

    Full Text Available In the last years there have been extraordinary advances in the development of gold-catalyzed cycloaddition processes. In this review we will summarize some of the most remarkable examples, and present the mechanistic rational underlying the transformations.

  19. Ruthenium-catalyzed C–H activation of thioxanthones

    OpenAIRE

    Danny Wagner; Stefan Bräse

    2015-01-01

    Thioxanthones – being readily available in one step from thiosalicylic acid and arenes – were used in ruthenium-catalyzed C–H-activation reaction to produce 1-mono- or 1,8-disubstituted thioxanthones in good to excellent yields. Scope and limitation of this reaction are presented.

  20. Ruthenium-catalyzed C–H activation of thioxanthones

    Science.gov (United States)

    Wagner, Danny

    2015-01-01

    Summary Thioxanthones – being readily available in one step from thiosalicylic acid and arenes – were used in ruthenium-catalyzed C–H-activation reaction to produce 1-mono- or 1,8-disubstituted thioxanthones in good to excellent yields. Scope and limitation of this reaction are presented. PMID:25977717

  1. DNA strand exchange catalyzed by molecular crowding in PEG solutions

    KAUST Repository

    Feng, Bobo

    2010-01-01

    DNA strand exchange is catalyzed by molecular crowding and hydrophobic interactions in concentrated aqueous solutions of polyethylene glycol, a discovery of relevance for understanding the function of recombination enzymes and with potential applications to DNA nanotechnology. © 2010 The Royal Society of Chemistry.

  2. Transfer Methane to Fragrant Hydrocarbon by Direct Catalyzed Dehydrogenation

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    @@ Sponsored by NSFC,a research project -"Transfer methane to fragrant hydrocarbon by direct catalyzed dehydrogenation",directed by Prof.Xin Bao from Dalian Institute of Chemical Physics of CAS,honored the 2nd class National Science & Technology Award in 2005.

  3. Polyphosphorous acid catalyzed cyclization in the synthesis of cryptolepine derivatives

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    11-Oxo-10,11-dihydroxy-5H-indolo[3,2,b]quinoline7-carboxylic acid was obtained specifically by polyphosphorous acid catalyzed cyclization with optimal reaction conditions. Biological assays showed that it potentially inhibits the proteasomal chymotrypsin-like activity in vitro and suppresses breast cancer cell growth.

  4. Asymmetric Catalytic Reactions Catalyzed by Chiral Titanium Complexes

    Institute of Scientific and Technical Information of China (English)

    FENG; XiaoMing

    2001-01-01

    Chiral titanium complexes is very importance catalyst to asymmetric catalytic reactions. A series of catalytic systems based on titanium-chiral ligands complexes has been reported. This presentation will discuss some of our recent progress on asymmetric catalytic reactions catalyzed by chiral titanium complexes.  ……

  5. Asymmetric Catalytic Reactions Catalyzed by Chiral Titanium Complexes

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    @@ Chiral titanium complexes is very importance catalyst to asymmetric catalytic reactions. A series of catalytic systems based on titanium-chiral ligands complexes has been reported. This presentation will discuss some of our recent progress on asymmetric catalytic reactions catalyzed by chiral titanium complexes.

  6. Kinetic Resolution of Aryl Alkenylcarbinols Catalyzed by Fc-PIP

    Institute of Scientific and Technical Information of China (English)

    胡斌; 孟萌; 姜山山; 邓卫平

    2012-01-01

    An effective kinetic resolution of a variety of aryl alkenylcarbinols catalyzed by nonenzymatic acyl transfer catalyst Fe-PIP was developed, affording corresponding unreacted alcohols in good to excellent ee value up to 99% and with selectivity factors up to 24.

  7. Lactam hydrolysis catalyzed by mononuclear metallo-ß-bactamases

    DEFF Research Database (Denmark)

    Olsen, Lars; Antony, J; Ryde, U;

    2003-01-01

    Two central steps in the hydrolysis of lactam antibiotics catalyzed by mononuclear metallo-beta-lactamases, formation of the tetrahedral intermediate and its breakdown by proton transfer, are studied for model systems using the density functional B3LYP method. Metallo-beta-lactamases have two met...

  8. Mechanistic approaches to palladium-catalyzed alkene difunctionalization reactions

    OpenAIRE

    Jensen, Katrina H.; Sigman, Matthew S.

    2008-01-01

    Alkene difunctionalization, the addition of two functional groups across a double bond, exemplifies a class of reactions with significant synthetic potential. This emerging area examines recent developments of palladium-catalyzed difunctionalization reactions, with a focus on mechanistic strategies that allow for functionalization of a common palladium alkyl intermediate.

  9. A Palladium-catalyzed Synthesis of 2-Substituted Indoles

    OpenAIRE

    Kasahara, Akira; YANAI, Hiroshi; Murakami, Satoshi

    1986-01-01

    Abstract In the presence of palladium (II) acetate, tri-o-tolylphosphine, and triethylamine, o-bromoaniline derivatives react readily with olefins such as ethylene, 1-hexene, styrene, ethyl acrylate, and acrylonitriIe, to produce o-alkenylaniline derivatives. A palladium (II) -catalyzed cyclization of o-alkenylaniline p-toluenesulfonamide led to a formation of a number of 1-tosylindole derivatives.

  10. Metal-Catalyzed Cleavage of tRNA[superscript Phe

    Science.gov (United States)

    Kirk, Sarah R.; Silverstein, Todd P.; McFarlane Holman, Karen L.

    2008-01-01

    This laboratory project is one component of a semester-long advanced biochemistry laboratory course that uses several complementary techniques to study tRNA[superscript Phe] conformational changes induced by ligand binding. In this article we describe a set of experiments in which students assay metal-catalyzed hydrolysis of tRNA[superscript Phe]…

  11. Gal3 Catalyzed Tetrahydropyranylation of Alcohols and Phenols

    Institute of Scientific and Technical Information of China (English)

    SUN, Pei-Pei(孙培培); HU, Zhi-Xin(胡志新)

    2004-01-01

    In dichloromethane, the nucleophilic addition of alcohols or phenols to 3,4-dihydro-2H-pyran (DHP) was catalyzed effectively by gallium triiodide which was generated in situ by the reaction of gallium metal and iodine to give the corresponding tetrahydropyranyl acetals in good to excellent yields.

  12. CU(II): catalyzed hydrazine reduction of ferric nitrate

    International Nuclear Information System (INIS)

    A method is described for producing ferrous nitrate solutions by the cupric ion-catalyzed reduction of ferric nitrate with hydrazine. The reaction is complete in about 1.5 hours at 400C. Hydrazoic acid is also produced in substantial quantities as a reaction byproduct

  13. 4-Dimenthylaminopyridine or Acid-Catalyzed Synthesis of Esters: A Comparison

    Science.gov (United States)

    van den Berg, Annemieke W. C.; Hanefeld, Ulf

    2006-01-01

    A set of highly atom-economic experiments was developed to highlight the differences between acid- and base-catalyzed ester syntheses and to introduce the principles of atom economy. The hydrochloric acid-catalyzed formation of an ester was compared with the 4-dimethylaminopyradine-catalyzed ester synthesis.

  14. Kinetics of Imidazole Catalyzed Ester Hydrolysis: Use of Buffer Dilutions to Determine Spontaneous Rate, Catalyzed Rate, and Reaction Order.

    Science.gov (United States)

    Lombardo, Anthony

    1982-01-01

    Described is an advanced undergraduate kinetics experiment using buffer dilutions to determine spontaneous rate, catalyzed rate, and reaction order. The reaction utilized is hydrolysis of p-nitro-phenyl acetate in presence of imidazole, which has been shown to enhance rate of the reaction. (Author/JN)

  15. Structural insights into G-protein-coupled receptor activation☆

    OpenAIRE

    Weis, William I.; Kobilka, Brian K.

    2008-01-01

    G-protein-coupled receptors (GPCRs) are the largest family of eukaryotic plasma membrane receptors, and are responsible for the majority of cellular responses to external signals. GPCRs share a common architecture comprising seven transmembrane (TM) helices. Binding of an activating ligand enables the receptor to catalyze the exchange of GTP for GDP in a heterotrimeric G protein. GPCRs are in a conformational equilibrium between inactive and activating states. Crystallographic and spectroscop...

  16. Regioselective Heck Coupling Reactions : Focus on Green Chemistry

    OpenAIRE

    Vallin, Karl S. A.

    2003-01-01

    Carbon-carbon bond formation reactions are among the most important processes in chemistry, as they represent key steps in the synthesis of more complex molecules from simple precursors. This thesis describes mainly the development of novel regioselective applications of the mild and versatile palladium-catalyzed carbon-carbon coupling method, commonly known as the Heck reaction. In addition, this thesis will focus on environmentally friendly developments of the Heck reaction. Novel ligand-co...

  17. Membrane Assembly Driven by a Biomimetic Coupling Reaction

    OpenAIRE

    Budin, Itay; Devaraj, Neal K.

    2011-01-01

    One of the major goals of synthetic biology is the development of non-natural cellular systems. In this work we describe a catalytic biomimetic coupling reaction capable of driving the de novo self-assembly of phospholipid membranes. Our system features a copper catalyzed azide-alkyne cycloaddition that results in the formation of a triazole containing phospholipid analog. Concomitant assembly of membranes occurs spontaneously, not requiring preexisting membranes to house catalysts or precurs...

  18. Ruthenium-BINAP Catalyzed Alcohol C-H tert-Prenylation via 1,3-Enyne Transfer Hydrogenation: Beyond Stoichiometric Carbanions in Enantioselective Carbonyl Propargylation.

    Science.gov (United States)

    Nguyen, Khoa D; Herkommer, Daniel; Krische, Michael J

    2016-04-27

    The chiral ruthenium complex formed in situ from (TFA)2Ru(CO)(PPh3)2 and (R)-BINAP is found to catalyze the enantioselective C-C coupling of diverse primary alcohols with the 1,3-enyne, TMSC≡CC(Me)═CH2, to form secondary homopropargyl alcohols bearing gem-dimethyl groups. All reagents for this byproduct-free coupling are inexpensive and commercially available, making this protocol a practical alternative to stoichiometric carbanions in enantioselective carbonyl reverse prenylation. PMID:27079149

  19. A reductive coupling strategy towards ripostatin A

    Directory of Open Access Journals (Sweden)

    Kristin D. Schleicher

    2013-07-01

    Full Text Available Synthetic studies on the antibiotic natural product ripostatin A have been carried out with the aim to construct the C9−C10 bond by a nickel(0-catalyzed coupling reaction of an enyne and an epoxide, followed by rearrangement of the resulting dienylcyclopropane intermediate to afford the skipped 1,4,7-triene. A cyclopropyl enyne fragment corresponding to C1−C9 has been synthesized in high yield and demonstrated to be a competent substrate for the nickel(0-catalyzed coupling with a model epoxide. Several synthetic approaches toward the C10−C26 epoxide have been pursued. The C13 stereocenter can be set by allylation and reductive decyanation of a cyanohydrin acetonide. A mild, fluoride-promoted decarboxylation enables construction of the C15−C16 bond by an aldol reaction. The product of this transformation is of the correct oxidation state and potentially three steps removed from the targeted epoxide fragment.

  20. Palladium coupling catalysts for pharmaceutical applications.

    Science.gov (United States)

    Doucet, Henri; Hierso, Jean-Cyrille

    2007-11-01

    This review discusses recent advances made in the area of palladium-catalyzed coupling reactions and describes a selection of the catalytic systems that are useful in the preparation of valuable compounds for the pharmaceutical industry. Most of these types of syntheses have used either simple palladium salts or palladium precursors associated with electron-rich mono- or bidentate phosphine ligands as catalysts. For some reactions, ligands such as triphenyl phosphine, 1,1'-bis(diphenylphosphino)ferrocene, a carbene or a bipyridine have also been employed. Several new procedures for the Suzuki cross-coupling reaction, the activation of aryl chlorides, the functionalization of aromatics and the synthesis of heteroaromatics are discussed. The C-H activation/ functionalization reactions of aryl and heteroaryl derivatives have emerged as powerful tools for the preparation of biaryl compounds, and the recent procedures and catalysts employed in this promising field are also highlighted herein. PMID:17987520

  1. Efficient Synthesis of Pyrrolo[2,1-a]isoquinoline and Pyrrolo[1,2-a]quinoline Derivatives via One-pot Two- step Metal-catalyzed Three-component Reactions

    Institute of Scientific and Technical Information of China (English)

    吴磊; 孙晶; 颜朝国

    2012-01-01

    A sequential one-pot two-step reaction for efficient synthesis of pyrrolo[2,1-a]isoquinoline and pyrrolo[1,2-a]- quinoline derivatives in good yields has been successfully developed. The reaction included firstly Cu-catalyzed three-component reaction of isoquinoline (quinoline), acetylenedicarboxylate and alkynylbenzene and then Pd-catalyzed intramolecular C(sp)-C(sp^2) coupling reaction of initially formed 1-alkenyl-2-alkynyl- 1,2-dihydroiso- quinoline (1,2-dihydroquinoline).

  2. Metal catalyzed atmospheric oxidation reactions. A challenge to coordination chemists

    Energy Technology Data Exchange (ETDEWEB)

    Coichev, N. (Sao Paulo Univ., SP (Brazil). Inst. de Quimica); Van Eldik, R. (Universitaet Witten/Herdecke (Germany))

    1994-01-01

    Oxidation reactions of SO[sub x] and NO[sub y] species in the aqueous phase can play an important role in atmospheric chemistry and are of major environmental concern. The auto-oxidation processes are known to be catalyzed by trace metal ions and complexes. An overview of the most important reactions in metal catalyzed autoxidation processes is presented. Attention is given to the oxidation of the SO[sub x] and NO[sub y] species separately, as well as to the combined chemistry that results from the interaction of SO[sub x] and NO[sub y] species in the absence and presence of metal ions. Our work has revealed a fascinating redox cycling of the metal ions and complexes during such autoxidation processes, which has turned out to present quite a challenge to coordination chemists. (authors). 118 refs., 4 figs., 1 tab.

  3. Cytochrome c catalyzes the in vitro synthesis of arachidonoyl glycine

    International Nuclear Information System (INIS)

    Long chain fatty acyl glycines are an emerging class of biologically active molecules that occur naturally and produce a wide array of physiological effects. Their biosynthetic pathway, however, remains unknown. Here we report that cytochrome c catalyzes the synthesis of N-arachidonoyl glycine (NAGly) from arachidonoyl coenzyme A and glycine in the presence of hydrogen peroxide. The identity of the NAGly product was verified by isotope labeling and mass analysis. Other heme-containing proteins, hemoglobin and myoglobin, were considerably less effective in generating arachidonoyl glycine as compared to cytochrome c. The reaction catalyzed by cytochrome c in vitro points to its potential role in the formation of NAGly and other long chain fatty acyl glycines in vivo

  4. Synthesis of heterocycles through transition-metal-catalyzed isomerization reactions

    DEFF Research Database (Denmark)

    Ishøy, Mette; Nielsen, Thomas Eiland

    2014-01-01

    versatile method to form iminium and oxocarbenium ions. Given the number of reactions involving these highly electrophilic intermediates, this concept provides a sea of opportunities for heterocycle synthesis, (see scheme; Nu=nucleophile). © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.......Metal-catalyzed isomerization of N- and O-allylic systems is emerging as an effective method to form synthetically useful iminium and oxocarbenium intermediates. In the presence of tethered nucleophiles, several recent examples illuminate this approach as a powerful strategy for the synthesis...... of structurally complex and diverse heterocycles. In this Concept article, we attempt to cover this area of research through a selection of recent versatile examples. A sea of opportunities! Transition-metal-catalyzed isomerization of N- and O-allylic compounds provides a mild, selective and synthetically...

  5. Microcalorimetric Study on Tyrosine Oxidation Catalyzed by Tyrosinase

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Through the method of initial heat release rate, the kinetic property of tyrosine oxidationcatalyzed by tyrosinase from Pseudomonas maltophilia was investigated using a LKB-2107 batchmicrocalorimeter. Tyrosine was catalyzed and oxidized into L-dopa, then into melanin catalyzed bytyrosinase. We found that the tyrosinase reaction obeyed the Michaelis-Menten kinetics, and at298.15K and pH 7.0, the initial exothermic rate (Ω0) are in the range of0.1567~0.5704 mJ@ s-1, themaximum exothermic rate (Ωmax) are in 0.4152 ~ 0.8143mol @ L-1, and mean value of the Michaelisconstant (Km) is 2.199±0.105×104 mol @ L-1.

  6. Highly Efficient C--N Bond Forming Reactions in Water Catalyzed by Copper(I) Iodide with Calix[4]arene Supported Amino Acid Ionic Liquid%Highly Efficient C--N Bond Forming Reactions in Water Catalyzed by Copper(I) Iodide with Calix[4]arene Supported Amino Acid Ionic Liquid

    Institute of Scientific and Technical Information of China (English)

    黄利; 金灿; 苏为科

    2012-01-01

    A novel and effective protocol has been developed for the Ullmann-type C--N coupling reaction catalyzed by calix[4]arene supported amino acid ionic liquid and copper(I) iodide in water under microwave irradiation condition The protocol uses ealix[4]arene supported amino acid ionic liquid as double function of the ligand and phase-transfer catalyst, and shows good tolerance in good to excellent yields.

  7. Ruthenium(II)-PNN pincer complex catalyzed dehydrogenation of benzyl alcohol to ester: A DFT study

    Science.gov (United States)

    Tao, Jingcong; Wen, Li; Lv, Xiaobo; Qi, Yong; Yin, Hailiang

    2016-04-01

    The molecular mechanism of the dehydrogenation of primary alcohol to ester catalyzed by the ruthenium(II)-PNN pincer complex Ru(H)(η2-BH4)(PNN), [PNN: (2-(di-tert-butylphosphinomethyl)-6-(diethlaminomethyl)-pyridine)] has been investigated using density functional theory calculations. The catalytic cycle includes three stages: (stage I) alcohol dehydrogenation to form aldehyde, (stage II) coupling of aldehyde with alcohol to give hemiacetal or ester, and (stage III) hemiacetal dehydrogenation to form ester. Two dehydrogenation reactions occur via the β-H elimination mechanism rather than the bifunctional double hydrogen transfer mechanism, which could be rationalized as the fluxional behavior of the BH4- ligand. At the second stage, the coupling reaction requires alcohol or the ruthenium catalyst as mediator. The formation of hemiacetal through the alcohol-mediated pathway is kinetically favorable than the ruthenium catalyst-mediated one, which may be attributed to the smaller steric hindrance when the aldehyde approaches the alcohol moiety in the reaction system. Our results would be helpful for experimental chemists to design more effective transition metal catalysts for dehydrogenation of alcohols.

  8. Practical carbon-carbon bond formation from olefins through nickel-catalyzed reductive olefin hydrocarbonation.

    Science.gov (United States)

    Lu, Xi; Xiao, Bin; Zhang, Zhenqi; Gong, Tianjun; Su, Wei; Yi, Jun; Fu, Yao; Liu, Lei

    2016-01-01

    New carbon-carbon bond formation reactions expand our horizon of retrosynthetic analysis for the synthesis of complex organic molecules. Although many methods are now available for the formation of C(sp(2))-C(sp(3)) and C(sp(3))-C(sp(3)) bonds via transition metal-catalyzed cross-coupling of alkyl organometallic reagents, direct use of readily available olefins in a formal fashion of hydrocarbonation to make C(sp(2))-C(sp(3)) and C(sp(3))-C(sp(3)) bonds remains to be developed. Here we report the discovery of a general process for the intermolecular reductive coupling of unactivated olefins with alkyl or aryl electrophiles under the promotion of a simple nickel catalyst system. This new reaction presents a conceptually unique and practical strategy for the construction of C(sp(2))-C(sp(3)) and C(sp(3))-C(sp(3)) bonds without using any organometallic reagent. The reductive olefin hydrocarbonation also exhibits excellent compatibility with varieties of synthetically important functional groups and therefore, provides a straightforward approach for modification of complex organic molecules containing olefin groups. PMID:27033405

  9. Transition metal-catalyzed one-pot synthesis of water-soluble dendritic molecular nanocarriers.

    Science.gov (United States)

    Chen, Guanghui; Guan, Zhibin

    2004-03-10

    Here, we report the first example of transition metal-catalyzed one-pot synthesis of water-soluble dendritic molecular nanocarriers behaving like unimolecular micelles. Using the palladium-alpha-diimine chain walking catalyst, copolymerization of ethylene and comonomer 3 afforded, in one step, amphiphilic copolymer 1 having a hydrophobic core and a hydrophilic shell. A much larger amphiphilic core-shell copolymer 2 was synthesized by a two-step approach: a copolymer having many free hydroxyl groups was first prepared, which was subsequently coupled to poly(ethylene glycol) (PEG) to afford the copolymer 2. Light-scattering, fluorescence, and UV/vis spectroscopic studies with Nile Red in aqueous solution showed unimolecular micellar properties for both copolymers 1 and 2. The dye encapsulation capacity for the core-shell copolymers is nearly proportional to the molecular weight of the hydrophobic core. The unimolecular micellar properties coupled with the good water solubility and biocompatibility of the PEG moieties make these molecular nanocarriers promising candidates for many applications including drug delivery and controlled drug release. PMID:14995158

  10. Iridium-catalyzed intramolecular [4 + 2] cycloadditions of alkynyl halides

    OpenAIRE

    Andrew Tigchelaar; William Tam

    2012-01-01

    Iridium-catalyzed intramolecular [4 + 2] cycloadditions of diene-tethered alkynyl halides were investigated by using [IrCl(cod)]2 as catalyst, and dppe was found to be the most suitable phosphine ligand for the reaction. No oxidative insertion of the iridium into the carbon–halide bond was observed, and the reactions proceeded to provide the halogenated cycloadducts in good yield (75–94%). These results are the first examples of cycloadditions of alkynyl halides using an iridium c...

  11. DNA-Catalyzed Hydrolysis of Esters and Aromatic Amides

    OpenAIRE

    Brandsen, Benjamin M.; Hesser, Anthony R.; Castner, Marissa A.; Chandra, Madhavaiah; Silverman, Scott K.

    2013-01-01

    We previously reported that DNA catalysts (deoxyribozymes) can hydrolyze DNA phosphodiester linkages, but DNA-catalyzed amide bond hydrolysis has been elusive. Here we used in vitro selection to identify DNA catalysts that hydrolyze ester linkages as well as DNA catalysts that hydrolyze aromatic amides, for which the leaving group is an aniline moiety. The aromatic amide-hydrolyzing deoxyribozymes were examined using linear free energy relationship analysis. The hydrolysis reaction is unaffec...

  12. Polyoxometalate catalyzed ozonation of chemical pulps in organic solvent media

    OpenAIRE

    Shatalov, Anatoly A.; Pereira, Helena

    2009-01-01

    Polyoxometalate (POM) catalyzed ozonation of chemical pulps in organic solvent media was found to be particularly effective and selective environmentally benign bleaching approach providing a way for substantial increase in pulp brightness, viscosity and degree of delignification in comparison with other ozone-based bleaching techniques. A series of tested low-boiling polar aprotic and protic organic solvents showed awell-defined capacity for ozonation improvement in the presence ...

  13. A Simple Strategy for Glycosyltransferase-Catalyzed Aminosugar Nucleotide Synthesis

    OpenAIRE

    Zhang, Jianjun; Singh, Shanteri; Hughes, Ryan R.; Zhou, Maoquan; Sunkara, Manjula; Morris, Andrew J.; Thorson, Jon S.

    2014-01-01

    A set of 2-chloro-4-nitrophenyl glucosamino/xylosaminosides were synthesized and assessed as potential substrates in the context of glycosyltransferase-catalyzed formation of the corresponding UDP/TDP-α-D-glucosamino-/xylosaminosugars and single vessel transglycosylation reactions with a model acceptor. This study highlights a robust platform for aminosugar nucleotide synthesis and reveals OleD Loki as a proficient catalyst for U/TDP-aminosugar synthesis and utilization.

  14. Ultrasound enhances lipase-catalyzed synthesis of poly (ethylene glutarate)

    OpenAIRE

    Xiaoman Zhao; Bansode, Sneha Ramrao; Ribeiro, Artur J.; Abreu, Ana S.; de Oliveira, César; Parpot, Pier; Gogate, P. R.; V. K. Rathod; Paulo, Artur Cavaco

    2016-01-01

    The present work explores the best conditions for the enzymatic synthesis of poly (ethylene glutarate) for the first time. The start-up materials are the liquids; diethyl glutarate and ethylene glycol diacetate, without the need of addition of extra solvent. The reactions are catalyzed by lipase B from Candida antarctica immobilized on glycidyl methacrylate-ter-divinylbenzene-ter-ethylene glycol dimethacrylate at 40 °C during 18 h in water bath with mechanical stirring or 1 h in ultrasonic ba...

  15. Blankets for tritium catalyzed deuterium (TCD) fusion reactors

    International Nuclear Information System (INIS)

    The TCD fusion fuel cycle - where the 3He from the D(D,n)3He reaction is transmuted, by neutron capture in the blanket, into tritium which is fed back to the plasma - was recently recognized as being potentially more promising than the Catalyzed Deuterium (Cat-D) fuel cycle for tokamak power reactors. It is the purpose of the present work to assess the feasibility of, and to identify promising directions for designing blankets for TCD fusion reactors

  16. Copper-catalyzed stereoselective conjugate addition of alkylboranes to alkynoates

    Science.gov (United States)

    Wakamatsu, Takamichi; Nagao, Kazunori

    2015-01-01

    Summary A copper-catalyzed conjugate addition of alkylboron compounds (alkyl-9-BBN, prepared by hydroboration of alkenes with 9-BBN-H) to alkynoates to form β-disubstituted acrylates is reported. The addition occurred in a formal syn-hydroalkylation mode. The syn stereoselectivity was excellent regardless of the substrate structure. A variety of functional groups were compatible with the conjugate addition. PMID:26734092

  17. Lipase-catalyzed polyester synthesis – A green polymer chemistry

    OpenAIRE

    Kobayashi, Shiro

    2010-01-01

    This article is a short comprehensive review describing in vitro polyester synthesis catalyzed by a hydrolysis enzyme of lipase, most of which has been developed for these two decades. Polyesters are prepared by repeated ester bond-formation reactions; they include two major modes, ring-opening polymerization (ROP) of cyclic monomers such as cyclic esters (lactones) and condensation polymerization via the reaction between a carboxylic acid or its ester group and an alcohol group. Polyester sy...

  18. Amylase catalyzed synthesis of glycosyl acrylates and their polymerization

    OpenAIRE

    Kloosterman, Wouter M. J.; Jovanovic, Danijela; Brouwer, Sander; Loos, Katja

    2014-01-01

    The enzymatic synthesis of novel (di)saccharide acrylates from starch and 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate and 4-hydroxybutyl acrylate (2-HEA, 2-HEMA and 4-HBA) catalyzed by various commercially available amylase preparations is demonstrated. Both liquefaction and saccharification amylases were tested as biocatalysts. Transglycosidation products were only detected in reaction mixtures containing saccharification amylases. The glycoamylase from Aspergillus niger was found t...

  19. Synthesis of Optically Active Polystyrene Catalyzed by Monophosphine Pd Complexes.

    Science.gov (United States)

    Jouffroy, Matthieu; Armspach, Dominique; Matt, Dominique; Osakada, Kohtaro; Takeuchi, Daisuke

    2016-07-11

    Cationic Pd(II) monophosphine complexes derived from α- and β-cyclodextrins (CDs) promote the homopolymerization of styrene under carbon monoxide pressure. Although reversible CO coordination takes place under catalytic conditions according to (13) C NMR studies with (13) C-enriched CO, both complexes catalyze the formation of CO-free styrene polymers. These macromolecules display optical activity as a result of the presence of stereoregular sequences within the overall atactic polymer. PMID:27218801

  20. Rhodium(II)-catalyzed enantioselective synthesis of troponoids.

    Science.gov (United States)

    Murarka, Sandip; Jia, Zhi-Jun; Merten, Christian; Daniliuc, Constantin-G; Antonchick, Andrey P; Waldmann, Herbert

    2015-06-22

    We report a rhodium(II)-catalyzed highly enantioselective 1,3-dipolar cycloaddition reaction between the carbonyl moiety of tropone and carbonyl ylides to afford troponoids in good to high yields with excellent enantioselectivity. We demonstrate that α-diazoketone-derived carbonyl ylides, in contrast to carbonyl ylides derived from diazodiketoesters, undergo [6+3] cycloaddition reactions with tropone to yield the corresponding bridged heterocycles with excellent stereoselectivity. PMID:25959033

  1. Palladium-Catalyzed Synthesis and Transformation of Organoboranes

    OpenAIRE

    Sebelius, Sara

    2006-01-01

    This thesis presents the development of new palladium-catalyzed transformations involving synthesis and application of allylborane reagents. In these reactions various palladium sources, including pincer complexes and commonly used catalysts were applied. A new transformation for allylation of aldehyde and imine substrates was devised using allyl acetates, diboronate reagents and catalytic amounts of Pd2(dba)3. By employment of commercially available chiral diboronates enantioenriched homoall...

  2. Novel Pincer Complex-Catalyzed Transformations : Including Asymmetric Catalysis

    OpenAIRE

    Aydin, Juhanes

    2009-01-01

    This thesis is focused on the development of new pincer complex-catalyzed transformations. Optimization of the catalytic properties (fine-tuning) was directed to increase the catalytic activity as well as the chemo-, stereo- and enantioselectivity of the complexes. This was achieved by varying the heteroatoms in the terdentate pincer ligand, by changing the electronic properties of the coordinated aryl moiety and by implementing chiral functionalities in the pincer complexes. In the cross-cou...

  3. Microwave-Enhanced Cross-Coupling Reactions Involving Alkynyltrifluoroborates with Aryl Bromides

    Directory of Open Access Journals (Sweden)

    George W. Kabalka

    2013-01-01

    Full Text Available Palladium-catalyzed alkynylation has emerged as one of the most reliable methods for the synthesis of alkynes which are often used in natural product syntheses and material science. An efficient method for coupling alkynyltrifluoroborates with various aryl bromides in the presence of a palladium catalyst has been developed using microwave irradiation. The microwave reactions are rapid and efficient.

  4. $a \\to e^+ e^-$ decay in a model with induced coupling to leptons

    OpenAIRE

    Mikheev, N. V.; Ovchinnikov, O. S.; Vassilevskaya, L. A.

    1998-01-01

    The process of electron-positron pair production by axion propagating in an external magnetic field is investigated in a model with only induced axion coupling to leptons. Contributions of the lowest and higher Landau levels are analyzed. The results we have obtained demonstrate a strong catalyzing influence of the field.

  5. Cross-Coupling of Acrylamides and Maleimides under Rhodium Catalysis: Controlled Olefin Migration.

    Science.gov (United States)

    Sharma, Satyasheel; Han, Sang Hoon; Oh, Yongguk; Mishra, Neeraj Kumar; Lee, Suk Hun; Oh, Joa Sub; Kim, In Su

    2016-06-01

    The rhodium(III)-catalyzed direct cross-coupling reaction of electron-deficient acrylamides with maleimides is described. This protocol displays broad functional group tolerance and high efficiency, which offers a new opportunity to access highly substituted succinimides. Dependent on the substituent positions of acrylamides and reaction conditions, olefin migrated products were obtained with high regio- and stereoselectivity. PMID:27182717

  6. A Novel and Efficient Catalytic System for Aerobic Oxidative Coupling of 2-Naphthol Derivatives

    Institute of Scientific and Technical Information of China (English)

    Li CHEN; Jing Bo LAN; Zhi Hua MAO; Xiao Qi YU; Ru Gang XIE

    2004-01-01

    The paper reported a novel and efficient aerobic oxidative coupling reaction of 2-naphthol derivatives catalyzed by CuCu (I or II)N-alkylimidazole complexes in excellent yields.The crystal structure of CuCu (II)N-methylimidazole complex to be determined by X-Ray.

  7. Tandem aldehyde–alkyne–amine coupling/cycloisomerization: A new synthesis of coumarins

    OpenAIRE

    Reddy, Maddi Sridhar; Thirupathi, Nuligonda; Haribabu, Madala

    2013-01-01

    Cu-catalyzed A3 coupling of ethoxyacetylene, pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to moderate yields.

  8. Tandem aldehyde–alkyne–amine coupling/cycloisomerization: A new synthesis of coumarins

    Directory of Open Access Journals (Sweden)

    Maddi Sridhar Reddy

    2013-01-01

    Full Text Available Cu-catalyzed A3 coupling of ethoxyacetylene, pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to moderate yields.

  9. Tandem aldehyde-alkyne-amine coupling/cycloisomerization: A new synthesis of coumarins.

    Science.gov (United States)

    Reddy, Maddi Sridhar; Thirupathi, Nuligonda; Haribabu, Madala

    2013-01-01

    Cu-catalyzed A(3) coupling of ethoxyacetylene, pyrrolidine and salicylaldehydes led to a concomitant cycloisomerization followed by hydrolysis of the resultant vinyl ether to afford coumarins in a cascade process. The reaction proceeded through exclusive 6-endo-dig cyclization and is compatible with halo and keto groups giving coumarins in good to moderate yields. PMID:23400373

  10. Synthesis and characterization of sulfonated polyphenylene containing benzophenone moiety via nickel catalyzed polymerization

    International Nuclear Information System (INIS)

    Graphical abstract: Synthesis and characterization of sulfonated polyphenylene containing benzophenone moiety via nickel catalyzed polymerization. - Highlights: • The active new monomer, 1,6-dichloro-2,5-dibenzoylbenzene, was synthesized. • The sulfonated polyphenylenes containing benzoyl moiety were synthesized with high molecular weight using Ni(II) and Zn catalysts. • Carbon-carbon structures membranes showed good performance with high proton conductivity. - Abstract: The synthesis of polyphenylenes containing benzoyl moiety (PPBP), their functionalization with sulfonic acid groups, and the measurement of properties for PEMs are described. The new monomer was synthesized from an oxidation reaction of 2,5-dichloro-p-xylene, followed by Fridel-craft reaction with benzene. The polymerization was performed by a Ni-catalyzed carbon-carbon coupling reaction of 1,6-dichloro-2,5-dibenzoylbenzene, followed by a sulfonation reaction with chlorosulfuric acid. Compared with Nafion 211® membrane, these SPPBPs showed rational IECs from 1.47 to 2.51 meq./g, water uptake from 54.1 to 88.4%, proton conductivity from 80.6 to 108.6 mS/cm, and high thermal stability. The proton conductivity was higher than Nafion 211®. These results showed that the morphology of the polymer matrix was greatly affected by the membranes’ properties and stability. Membranes, including benzoyl segments without ether linkage, also provided good dimensional stability in spite of high IEC values. The properties of SPPBPs were very remarkable for fuel cell membrane application. This research demonstrated the possibility of promising SPPBP membranes for excellent proton conductivity

  11. Development of Copper-Catalyzed Electrophilic Trifluoromethylation and Exploiting Cu/Cu2O Nanowires with Novel Catalytic Reactivity

    KAUST Repository

    Li, Huaifeng

    2014-06-01

    area of the active component, thereby enhancing the contact between reactants and catalyst dramatically. Based on the above-mentioned concepts and with the aim of achieving one “green and sustainable” approach, C-S bond formation and click reactions catalyzed by Cu/Cu2O nanowires were investigated. It was found that the recyclable core-shell structured Cu/Cu2O nanowires could be applied as a highly reactive catalysts for the cross-coupling reaction between aryl iodides and the cycloaddition of terminal alkynes and azides under ligand-free conditions. Furthermore, these results were the first report for the crosscoupling reaction and click reaction catalyzed by one-dimensional (1D) copper nanowires.

  12. Cost analysis of simulated base-catalyzed biodiesel production processes

    International Nuclear Information System (INIS)

    Highlights: • Two semi-continuous biodiesel production processes from sunflower oil are simulated. • Simulations were based on the kinetics of base-catalyzed methanolysis reactions. • The total energy consumption was influenced by the kinetic model. • Heterogeneous base-catalyzed process is a preferable industrial technology. - Abstract: The simulation and economic feasibility evaluation of semi-continuous biodiesel production from sunflower oil were based on the kinetics of homogeneously (Process I) and heterogeneously (Process II) base-catalyzed methanolysis reactions. The annual plant’s capacity was determined to be 8356 tonnes of biodiesel. The total energy consumption was influenced by the unit model describing the methanolysis reaction kinetics. The energy consumption of the Process II was more than 2.5 times lower than that of the Process I. Also, the simulation showed the Process I had more and larger process equipment units, compared with the Process II. Based on lower total capital investment costs and biodiesel selling price, the Process II was economically more feasible than the Process I. Sensitivity analysis was conducted using variable sunflower oil and biodiesel prices. Using a biodiesel selling price of 0.990 $/kg, Processes I and II were shown to be economically profitable if the sunflower oil price was 0.525 $/kg and 0.696 $/kg, respectively

  13. Cell-surface acceleration of urokinase-catalyzed receptor cleavage

    DEFF Research Database (Denmark)

    Høyer-Hansen, G; Ploug, M; Behrendt, N;

    1997-01-01

    or indirectly mediated by uPA itself. In a soluble system, uPA can cleave purified uPAR, but the low efficiency of this reaction has raised doubts as to whether uPA is directly responsible for uPAR cleavage on the cells. We now report that uPA-catalyzed cleavage of uPAR on the cell surface is...... strongly favored relative to the reaction in solution. The time course of uPA-catalyzed cleavage of cell-bound uPAR was studied using U937 cells stimulated with phorbol 12-myristate 13-acetate. Only 30 min was required for 10 nM uPA to cleave 50% of the cell-bound uPAR. This uPA-catalyzed cleavage reaction...... was inhibited by a prior incubation of the cells with uPA inactivated by diisopropyl fluorophosphate, demonstrating a requirement for specific receptor binding of the active uPA to obtain the high-efficiency cleavage of cell-bound uPAR. Furthermore, amino-terminal sequence analysis revealed that u...

  14. Palladium-catalyzed C–N and C–O bond formation of N-substituted 4-bromo-7-azaindoles with amides, amines, amino acid esters and phenols

    Directory of Open Access Journals (Sweden)

    Rajendra Surasani

    2012-11-01

    Full Text Available Simple and efficient procedures for palladium-catalyzed cross-coupling reactions of N-substituted 4-bromo-7-azaindole (1H-pyrrole[2,3-b]pyridine, with amides, amines, amino acid esters and phenols through C–N and C–O bond formation have been developed. The C–N cross-coupling reaction of amides, amines and amino acid esters takes place rapidly by using the combination of Xantphos, Cs2CO3, dioxane and palladium catalyst precursors Pd(OAc2/Pd2(dba3. The combination of Pd(OAc2, Xantphos, K2CO3 and dioxane was found to be crucial for the C–O cross-coupling reaction. This is the first report on coupling of amides, amino acid esters and phenols with N-protected 4-bromo-7-azaindole derivatives.

  15. Acid-Catalyzed Preparation of Biodiesel from Waste Vegetable Oil: An Experiment for the Undergraduate Organic Chemistry Laboratory

    Science.gov (United States)

    Bladt, Don; Murray, Steve; Gitch, Brittany; Trout, Haylee; Liberko, Charles

    2011-01-01

    This undergraduate organic laboratory exercise involves the sulfuric acid-catalyzed conversion of waste vegetable oil into biodiesel. The acid-catalyzed method, although inherently slower than the base-catalyzed methods, does not suffer from the loss of product or the creation of emulsion producing soap that plagues the base-catalyzed methods when…

  16. Cross-coupling reactions of organosilicon compounds: new concepts and recent advances.

    Science.gov (United States)

    Denmark, Scott Eric; Sweis, Ramzi Farah

    2002-12-01

    This review highlights the rapid evolution of the newly-developed class of palladium-catalyzed cross-coupling reactions of organosilicon compounds. A myriad of heteroatom-containing silicon moieties (silyl hydrides, siletanes, silanols, silyl ethers, orthosiliconates, di- and polysiloxanes and pyridylsilanes) undergo mild and stereospecific cross-coupling. The diversity of methods for introduction of silicon groups into organic molecules and the range of organic electrophiles that can be used are emphasized. PMID:12499586

  17. Aqueous microwave-assisted cross-coupling reactions applied to unprotected nucleosides

    Science.gov (United States)

    Hervé, Gwénaëlle; Len, Christophe

    2015-01-01

    Metal catalyzed cross-coupling reactions have been the preferred tools to access to modified nucleosides (on the C5-position of pyrimidines and on the C7- or C8-positions of purines). Our objective is to focus this mini-review on the Suzuki-Miyaura and on the Heck cross-couplings of nucleosides using microwave irradiations which is an alternative technology compatible with green chemistry and sustainable development PMID:25741506

  18. Ammonia and hydrazine. Transition-metal-catalyzed hydroamination and metal-free catalyzed functionalization

    Energy Technology Data Exchange (ETDEWEB)

    Bertrand, Guy [Univ. of California, San Diego, CA (United States)

    2012-06-29

    high temperatures and long reaction times. To address this issue, we have developed several new families of carbon- and boron-based ligands, which are even better donors. The corresponding metal complexes (particularly gold, rhodium, iridium, and ruthenium) of all these species will be tested in the Markovnikov and anti-Markovnikov hydroamination of alkynes, allenes, and also alkenes with ammonia and hydrazine. We will also develop metal-free catalytic processes for the functionalization of ammonia and hydrazine. By possessing both a lone pair of electrons and an accessible vacant orbital, singlet carbenes resemble and can mimic the chemical behavior of transition metals. Our preliminary results demonstrate that specially designed carbenes can split the N–H bond of ammonia by an initial nucleophilic activation that prevents the formation of Lewis acid-base adducts, which is the major hurdle for the transition metal catalyzed functionalization of NH3. The use of purely organic compounds as catalysts will eliminate the major drawbacks of transition-metal-catalysis technology, which are the excessive cost of metal complexes (metal + ligands) and in many cases the toxicity of the metal.

  19. Development and industrial application of catalyzer for low-temperature hydrogenation hydrolysis of Claus tail gas

    Directory of Open Access Journals (Sweden)

    Honggang Chang

    2015-10-01

    Full Text Available With the implementation of more strict national environmental protection laws, energy conservation, emission reduction and clean production will present higher requirements for sulfur recovery tail gas processing techniques and catalyzers. As for Claus tail gas, conventional hydrogenation catalyzers are gradually being replaced by low-temperature hydrogenation catalyzers. This paper concentrates on the development of technologies for low-temperature hydrogenation hydrolysis catalyzers, preparation of such catalyzers and their industrial application. In view of the specific features of SO2 hydrogenation and organic sulfur hydrolysis during low-temperature hydrogenation, a new technical process involving joint application of hydrogenation catalyzers and hydrolysis catalyzers was proposed. In addition, low-temperature hydrogenation catalyzers and low-temperature hydrolysis catalyzers suitable for low-temperature conditions were developed. Joint application of these two kinds of catalyzers may reduce the inlet temperatures in the conventional hydrogenation reactors from 280 °C to 220 °C, at the same time, hydrogenation conversion rates of SO2 can be enhanced to over 99%. To further accelerate the hydrolysis rate of organic sulfur, the catalyzers for hydrolysis of low-temperature organic sulfur were developed. In lab tests, the volume ratio of the total sulfur content in tail gas can be as low as 131 × 10−6 when these two kinds of catalyzers were used in a proportion of 5:5 in volumes. Industrial application of these catalyzers was implemented in 17 sulfur recovery tail gas processing facilities of 15 companies. As a result, Sinopec Jinling Petrochemical Company had outstanding application performances with a tail gas discharging rate lower than 77.9 mg/m3 and a total sulfur recovery of 99.97%.

  20. Facile Synthesis of N-Tosyl Aza-Baylis-Hillman Adducts of Acrylamide via a Pd-Catalyzed Hydration of Nitrile to Amide

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Eun Sun; Kim, Yu Mi; Kim, Jae Nyoung [Chonnam National Univ., Gwangju (Korea, Republic of)

    2010-03-15

    We developed an efficient palladium-catalyzed two-step protocol for the synthesis of N-tosyl aza-Baylis-Hillman adducts of acrylamide. The method involved the preparation of the corresponding Baylis-Hillman adducts of acrylonitrile and the following Pd-catalyzed hydration of nitrile with acetaldoxime. The Baylis-Hillman reaction, which involves the coupling of activated vinyl compounds with electrophiles under the catalytic influence of a tertiary amine, gives rise to adducts, so called Baylis-Hillman adducts, with a new stereocenter and has proven to be a very useful carbon-carbon bond-forming method in the synthesis of highly functionalized molecules. As the activated vinyl compounds, various compounds have been used in the Baylis-Hillman reaction including acrylates, acrylonitrile, vinyl ketones, vinyl sulfones and acrylamides. However, among the activated vinyl compounds acrylamide has not been used much for the synthesis of the corresponding Baylis-Hillman adducts due to its sluggish reactivity.

  1. Facile Synthesis of N-Tosyl Aza-Baylis-Hillman Adducts of Acrylamide via a Pd-Catalyzed Hydration of Nitrile to Amide

    International Nuclear Information System (INIS)

    We developed an efficient palladium-catalyzed two-step protocol for the synthesis of N-tosyl aza-Baylis-Hillman adducts of acrylamide. The method involved the preparation of the corresponding Baylis-Hillman adducts of acrylonitrile and the following Pd-catalyzed hydration of nitrile with acetaldoxime. The Baylis-Hillman reaction, which involves the coupling of activated vinyl compounds with electrophiles under the catalytic influence of a tertiary amine, gives rise to adducts, so called Baylis-Hillman adducts, with a new stereocenter and has proven to be a very useful carbon-carbon bond-forming method in the synthesis of highly functionalized molecules. As the activated vinyl compounds, various compounds have been used in the Baylis-Hillman reaction including acrylates, acrylonitrile, vinyl ketones, vinyl sulfones and acrylamides. However, among the activated vinyl compounds acrylamide has not been used much for the synthesis of the corresponding Baylis-Hillman adducts due to its sluggish reactivity

  2. Oxidation of Cucurbitadienol Catalyzed by CYP87D18 in the Biosynthesis of Mogrosides from Siraitia grosvenorii.

    Science.gov (United States)

    Zhang, Jiangsheng; Dai, Longhai; Yang, Jiangang; Liu, Can; Men, Yan; Zeng, Yan; Cai, Yi; Zhu, Yueming; Sun, Yuanxia

    2016-05-01

    Mogrosides, the principally bioactive compounds extracted from the fruits of Siraitia grosvenorii, are a group of glycosylated cucurbitane-type tetracyclic triterpenoid saponins that exhibit a wide range of notable biological activities and are commercially available worldwide as natural sweeteners. The biosynthesis of mogrosides involves initial cyclization of 2,3-oxidosqualene to the triterpenoid skeleton of cucurbitadienol, followed by a series of oxidation reactions catalyzed by Cyt P450s (P450s) and then glycosylation reactions catalyzed by UDP glycosyltransferases (UGTs). We previously reported the identification of a cucurbitadienol synthase (SgCbQ) and a mogrol C-3 hydroxyl glycosyltransferase (UGT74AC1). However, molecular characterization of further transformation of cucurbitadienol to mogrol by P450s remains unavailable. In this study, we report the successful identification of a multifunctional P450 (CYP87D18) as being involved in C-11 oxidation of cucurbitadienol. In vitro enzymatic activity assays showed that CYP87D18 catalyzed the oxidation of cucurbitadienol at C-11 to produce 11-oxo cucurbitadienol and 11-hydroxy cucurbitadienol. Furthermore, 11-oxo-24,25-epoxy cucurbitadienol as well as 11-oxo cucurbitadienol and 11-hydroxy cucurbitadienol were produced when CYP87D18 was co-expressed with SgCbQ in genetic yeast, and their structures were confirmed by liquid chromatography-solid-phase extraction-nuclear magnetic resonance-mass spectrometry coupling (LC-SPE-NMR-MS). Taken together, these results suggest a role for CYP87D18 as a multifunctional cucurbitadienol oxidase in the mogrosides pathway. PMID:26903528

  3. A SABATH Methyltransferase from the moss Physcomitrella patens catalyzes

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Nan [ORNL; Ferrer, Jean-Luc [Universite Joseph Fourier, France; Moon, Hong S [Department of Plant Sciences, University of Tennessee; Kapteyn, Jeremy [Institute of Biological Chemistry, Washington State University; Zhuang, Xiaofeng [Department of Plant Sciences, University of Tennessee; Hasebe, Mitsuyasu [Laboratory of Evolutionary Biology, National Institute for Biology, 38 Nishigounaka; Stewart, Neal C. [Department of Plant Sciences, University of Tennessee; Gang, David R. [Institute of Biological Chemistry, Washington State University; Chen, Feng [University of Tennessee, Knoxville (UTK)

    2012-01-01

    Known SABATH methyltransferases, all of which were identified from seed plants, catalyze methylation of either the carboxyl group of a variety of low molecular weight metabolites or the nitrogen moiety of precursors of caffeine. In this study, the SABATH family from the bryophyte Physcomitrella patens was identified and characterized. Four SABATH-like sequences (PpSABATH1, PpSABATH2, PpSABATH3, and PpSABATH4) were identified from the P. patens genome. Only PpSABATH1 and PpSABATH2 showed expression in the leafy gametophyte of P. patens. Full-length cDNAs of PpSABATH1 and PpSABATH2 were cloned and expressed in soluble form in Escherichia coli. Recombinant PpSABATH1 and PpSABATH2 were tested for methyltransferase activity with a total of 75 compounds. While showing no activity with carboxylic acids or nitrogen-containing compounds, PpSABATH1 displayed methyltransferase activity with a number of thiols. PpSABATH2 did not show activity with any of the compounds tested. Among the thiols analyzed, PpSABATH1 showed the highest level of activity with thiobenzoic acid with an apparent Km value of 95.5 lM, which is comparable to those of known SABATHs. Using thiobenzoic acid as substrate, GC MS analysis indicated that the methylation catalyzed by PpSABATH1 is on the sulfur atom. The mechanism for S-methylation of thiols catalyzed by PpSABATH1 was partially revealed by homology-based structural modeling. The expression of PpSABATH1 was induced by the treatment of thiobenzoic acid. Further transgenic studies showed that tobacco plants overexpressing PpSABATH1 exhibited enhanced tolerance to thiobenzoic acid, suggesting that PpSABATH1 have a role in the detoxification of xenobiotic thiols.

  4. Physio-pathological roles of transglutaminase-catalyzed reactions

    Institute of Scientific and Technical Information of China (English)

    Mariangela; Ricotta; Maura; Iannuzzi; Giulia; De; Vivo; Vittorio; Gentile

    2010-01-01

    Transglutaminases(TGs) are a large family of related and ubiquitous enzymes that catalyze post-translational modifications of proteins.The main activity of these enzymes is the cross-linking of a glutaminyl residue of a protein/peptide substrate to a lysyl residue of a protein/peptide co-substrate.In addition to lysyl residues,other second nucleophilic co-substrates may include monoamines or polyamines(to form mono-or bi-substituted/crosslinked adducts) or-OH groups(to form ester linkages) .In the absence of co-substrates,the nucleophile may be water,resulting in the net deamidation of the glutaminyl residue.The TG enzymes are also capable of catalyzing other reactions important for cell viability.The distribution and the physiological roles of TG enzymes have been widely studied in numerous cell types and tissues and their roles in several diseases have begun to be identified."Tissue" TG(TG2) ,a member of the TG family of enzymes,has definitely been shown to be involved in the molecular mechanisms responsible for a very widespread human pathology:i.e.celiac disease(CD) .TG activity has alsobeen hypothesized to be directly involved in the pathogenetic mechanisms responsible for several other human diseases,including neurodegenerative diseases,which are often associated with CD.Neurodegenerative diseases,such as Alzheimer’s disease,Parkinson’s disease,supranuclear palsy,Huntington’s disease and other recently identified polyglutamine diseases,are characterized,in part,by aberrant cerebral TG activity and by increased cross-linked proteins in affected brains.In this review,we discuss the physio-pathological role of TG-catalyzed reactions,with particular interest in the molecular mechanisms that could involve these enzymes in the physio-pathological processes responsible for human neurodegenerative diseases.

  5. Ruthenium-Catalyzed meta-Selective C—H Bromination

    Science.gov (United States)

    Teskey, Christopher J; Lui, Andrew Y W; Greaney, Michael F

    2015-01-01

    The first example of a transition-metal-catalyzed, meta-selective C–H bromination procedure is reported. In the presence of catalytic [{Ru(p-cymene)Cl2}2], tetrabutylammonium tribromide can be used to functionalize the meta C–H bond of 2-phenylpyridine derivatives, thus affording difficult to access products which are highly predisposed to further derivatization. We demonstrate this utility with one-pot bromination/arylation and bromination/alkenylation procedures to deliver meta-arylated and meta-alkenylated products, respectively, in a single step. PMID:26288217

  6. Ruthenium-Catalyzed meta-Selective C—H Bromination

    OpenAIRE

    Teskey, Christopher J; Lui, Andrew Y W; Greaney, Michael F.

    2015-01-01

    The first example of a transition-metal-catalyzed, meta-selective C–H bromination procedure is reported. In the presence of catalytic [{Ru(p-cymene)Cl2}2], tetrabutylammonium tribromide can be used to functionalize the meta C–H bond of 2-phenylpyridine derivatives, thus affording difficult to access products which are highly predisposed to further derivatization. We demonstrate this utility with one-pot bromination/arylation and bromination/alkenylation procedures to deliver meta-arylated and...

  7. Palladium-Catalyzed alpha-Arylation of Tetramic Acids

    DEFF Research Database (Denmark)

    Storgaard, Morten; Dorwald, F. Z.; Peschke, B.;

    2009-01-01

    A mild, racemization-free, palladium-Catalyzed alpha-arylation of tetramic acids (2,4-pyrrolidinediones) has been developed. Various amino acid-derived tetramic acids were cleanly arylated by treatment with 2 mol % of Pd(OAc)(2), 4 mol % of a sterically demanding biaryl phosphine, 2.3 equiv of K2...... effect on their reactivity: both electron-rich and electron-poor aryl chlorides and bromides or triflates led to good yields. Ortho-substituted aryl halides and heteroaryl halides, however, did not undergo the title reaction....

  8. Pt-Catalyzed Synthesis of Functionalized Symmetrical and Unsymmetrical Disilazanes.

    Science.gov (United States)

    Kuciński, Krzysztof; Szudkowska-Frątczak, Justyna; Hreczycho, Grzegorz

    2016-09-01

    In nearly every total synthesis, silylating agents are employed in synthetic steps to protect sensitive functional groups. A Pt-catalyzed hydrosilylation of various unsaturated substrates to prepare novel symmetrical and unsymmetrical disilazanes is described. The developed synthetic methodology is widely applicable and tolerates all manner of functional groups (e.g., amines, ethers, esters, halogens, silanes, etc.). To demonstrate the value of the described method, mono-substituted 1,1,3,3-tetramethyldisilazanes were further selectively converted to completely new unsymmetrical derivatives. PMID:27414042

  9. Comparing Ru and Fe-catalyzed olefin metathesis

    KAUST Repository

    Poater, Albert

    2014-01-01

    Density functional theory calculations have been used to explore the potential of Fe-based complexes with an N-heterocyclic carbene ligand, as olefin metathesis catalysts. Apart from a less endothermic reaction energy profile, a small reduction in the predicted upper energy barriers (≈ 2 kcal mol -1) is calculated in the Fe catalyzed profile with respect to the Ru catalysed profile. Overall, this study indicates that Fe-based catalysts have the potential to be very effective olefin metathesis catalysts. This journal is © the Partner Organisations 2014.

  10. Zinc oxide catalyzed growth of single-walled carbon nanotubes

    International Nuclear Information System (INIS)

    We demonstrate that zinc oxide can catalyze the growth of single-walled carbon nanotubes (SWNTs) with high efficiency by a chemical vapor deposition process. The zinc oxide nanocatalysts, prepared using a diblock copolymer templating method and characterized by atomic force microscopy (AFM), were uniformly spaced over a large deposition area with an average diameter of 1.7 nm and narrow size distribution. Dense and uniform SWNTs films with high quality were obtained by using a zinc oxide catalyst, as characterized by scanning electron microscopy (SEM), Raman spectroscopy, AFM, and high-resolution transmission electron microscopy (HRTEM).

  11. Ruthenium-Catalyzed Cascade C—H Functionalization of Phenylacetophenones**

    OpenAIRE

    Mehta, Vaibhav P; García-López, José-Antonio; Greaney, Michael F.

    2014-01-01

    Three orthogonal cascade C—H functionalization processes are described, based on ruthenium-catalyzed C—H alkenylation. 1-Indanones, indeno indenes, and indeno furanones were accessed through cascade pathways by using arylacetophenones as substrates under conditions of catalytic [{Ru(p-cymene)Cl2}2] and stoichiometric Cu(OAc)2. Each transformation uses C—H functionalization methods to form C—C bonds sequentially, with the indeno furanone synthesis featuring a C—O bond formation as the terminat...

  12. Deoxyribonucleoside kinases: two enzyme families catalyze the same reaction

    DEFF Research Database (Denmark)

    Sandrini, Michael; Piskur, Jure

    2005-01-01

    Mammals have four deoxyribonucleoside kinases, the cytoplasmic (TK1) and mitochondrial (TK2) thymidine kinases, and the deoxycytidine (dCK) and deoxyguanosine (dGK) kinases, which salvage the precursors for nucleic acids synthesis. In addition to the native deoxyribonucleoside substrates, the kin...... kinases can phosphorylate and thereby activate a variety of anti-cancer and antiviral prodrugs. Recently, the crystal structure of human TK1 has been solved and has revealed that enzymes with fundamentally different origins and folds catalyze similar, crucial cellular reactions....

  13. Iron-Catalyzed C-H Functionalization Processes.

    Science.gov (United States)

    Cera, Gianpiero; Ackermann, Lutz

    2016-10-01

    Iron-catalyzed C-H activation has recently emerged as an increasingly powerful tool for the step-economical transformation of unreactive C-H bonds. Particularly, the recent development of low-valent iron catalysis has set the stage for novel C-H activation strategies via chelation assistance. The low-cost, natural abundance, and low toxicity of iron prompted its very recent application in organometallic C-H activation catalysis. An overview of the use of iron catalysis in C-H activation processes is summarized herein up to May 2016. PMID:27573499

  14. Iodine - catalyzed prins cyclization of aliphatic and aromatic ketones

    Energy Technology Data Exchange (ETDEWEB)

    Kishore, K.R.; Reddy, K.; Silva Junior, Luiz F., E-mail: luizfsjr@iq.usp.br [Universidade de Sao Paulo (IQ/USP), SP (Brazil). Inst. de Quimica. Dept. de Quimica Fundamental

    2013-09-15

    Iodine-catalyzed Prins cyclization of homoallylic alcohols and ketones was investigated. Anhydrous conditions and inert atmosphere are not required in this metal-free protocol. The reaction of 2-(3,4-dihydronaphthalene-1-yl)propan-1-ol with six aliphatic symmetric ketones gave the desired products in 67-77% yield. Cyclization was performed with four aliphatic unsymmetric ketones, leading to corresponding pyrans in 66-76% yield. Prins cyclization was also accomplished with four aromatic ketones in 37-66% yield. Finally, Prins cyclization of the monoterpene isopulegol and acetone was successfully achieved. (author)

  15. MOLYBDENUM CATALYZED ACID PEROXIDE BLEACHING OF EUCALYPTUS KRAFT PULP

    OpenAIRE

    Marcos S. Rabelo; Jorge L. Colodette; Vera M. Sacon; Marcelo R. Silva; Marco A. B. Azevedo

    2008-01-01

    Molybdenum catalyzed peroxide bleaching (PMo Stage) consists of pulp treatment with hydrogen peroxide under acidic conditions in the presence of a molybdenum catalyst. Molybdenum is applied in catalytic doses (50-200 mg/kg pulp) and may originate from various sources, including (NH4)6Mo7O24.4H2O, Na2MoO4.2H2O, siliconmolybdate, etc. This work is aimed at optimizing the PMo stage and evaluating its industrial application in the OAZDP sequence. Optimum PMo stage conditions for bleaching eucalyp...

  16. Triphenylphosphine-Catalyzed Michael Addition of Alcohols to Acrylic Compounds

    Institute of Scientific and Technical Information of China (English)

    LIU, Hai-Ling; JIANG, Huan-Feng; WANG, Yu-Gang

    2007-01-01

    A facile triphenylphosphine-catalyzed Michael addition of alcohols to acrylic compounds was described. The reaction was carried out in open air at refluxing temperature in the presence of 10 mol% PPh3. Michael addition of saturated and unsaturated alcohols to acrylonitrile or acrylates has been examined. The reaction gaveβ-alkoxy derivatives with isolated yields of 5%-79%. PPh3 is cheaper and more stable than those trialkylphosphines previously used for the similar reactions, and the products can be easily separated from the reaction mixture via distillation.

  17. Synthesis of Rosin Acid Starch Catalyzed by Lipase

    OpenAIRE

    Rihui Lin; He Li; Han Long; Jiating Su; Wenqin Huang

    2014-01-01

    Rosin, an abundant raw material from pine trees, was used as a starting material directly for the synthesis of rosin acid starch. The esterification reaction was catalyzed by lipase (Novozym 435) under mild conditions. Based on single factor experimentation, the optimal esterification conditions were obtained as follows: rosin acid/anhydrous glucose unit in the molar ratio 2 : 1, reaction time 4 h at 45°C, and 15% of lipase dosage. The degree of substitution (DS) reaches 0.098. Product from e...

  18. FBH1 Catalyzes Regression of Stalled Replication Forks

    DEFF Research Database (Denmark)

    Fugger, Kasper; Mistrik, Martin; Neelsen, Kai J;

    2015-01-01

    DNA replication fork perturbation is a major challenge to the maintenance of genome integrity. It has been suggested that processing of stalled forks might involve fork regression, in which the fork reverses and the two nascent DNA strands anneal. Here, we show that FBH1 catalyzes regression of a...... model whereby FBH1 promotes early checkpoint signaling by remodeling of stalled DNA replication forks....... model replication fork in vitro and promotes fork regression in vivo in response to replication perturbation. Cells respond to fork stalling by activating checkpoint responses requiring signaling through stress-activated protein kinases. Importantly, we show that FBH1, through its helicase activity, is...

  19. Update on muon-catalyzed fusion research at LAMPF

    International Nuclear Information System (INIS)

    An experimental investigation of muon-catalyzed fusion in mixtures of the hydrogen isotopes (and helium) began in 1982 at the Los Alamos Meson Physics Facility. The explorations cover a wide range of mixture densities (12 to 140% liquid hydrogen density) and temperatures (13 to 1800K). Many parameters of muon catalysis have been measured for the first time, including distinct dtμ-molecular formation rates as functions of temperature and density. The discovery that the effective α-μ sticking probability becomes quite small for elevated mixture densities is particularly intriguing and challenging to our understanding. Preliminary new results will be presented in the context of acquired results

  20. Iron-Catalyzed Hydroboration: Unlocking Reactivity through Ligand Modulation.

    Science.gov (United States)

    Espinal-Viguri, Maialen; Woof, Callum R; Webster, Ruth L

    2016-08-01

    Iron-catalyzed hydroboration (HB) of alkenes and alkynes is reported. A simple change in ligand structure leads to an extensive change in catalyst activity. Reactions proceed efficiently over a wide range of challenging substrates including activated, unactivated and sterically encumbered motifs. Conditions are mild and do not require the use of reducing agents or other additives. Large excesses of borating reagent are not required, allowing control of chemo- and regioselectivity in the presence of multiple double bonds. Mechanistic insight reveals that the reaction is likely to proceed via a highly reactive iron hydride intermediate. PMID:27321704

  1. Synthesis of Dihydrobenzofurans via Palladium-Catalyzed Heteroannulations

    Energy Technology Data Exchange (ETDEWEB)

    Roman Vladimirovich Rozhkov

    2004-12-19

    Palladium-catalyzed heteroannulation of 1,3-dienes with 3-iodo-2-alkenols, and 2-iodo-2-alkenols, as well as their amino analogs, affords the corresponding cyclic ethers and amines respectively. The presence of a {beta}-hydrogen in the vinylic halide results in {beta}-hydride elimination giving the corresponding alkyne. The presence of a bulky group in the {alpha}-position of the vinylic halide results in failure or reduced amounts of annulation products. A chloride source, pyridine base and electron-rich phosphine are essential for this reaction.

  2. Output-input coupling in thermally fluctuating biomolecular machines

    CERN Document Server

    Kurzynski, Michal; Chelminiak, Przemyslaw

    2011-01-01

    Biological molecular machines are proteins that operate under isothermal conditions hence are referred to as free energy transducers. They can be formally considered as enzymes that simultaneously catalyze two chemical reactions: the free energy-donating reaction and the free energy-accepting one. Most if not all biologically active proteins display a slow stochastic dynamics of transitions between a variety of conformational substates composing their native state. In the steady state, this dynamics is characterized by mean first-passage times between transition substates of the catalyzed reactions. On taking advantage of the assumption that each reaction proceeds through a single pair (the gate) of conformational transition substates of the enzyme-substrates complex, analytical formulas were derived for the flux-force dependence of the both reactions, the respective stalling forces and the degree of coupling between the free energy-accepting (output) reaction flux and the free energy-donating (input) one. Th...

  3. Biotinylated phosphoproteins from kinase-catalyzed biotinylation are stable to phosphatases: Implications for phosphoproteomics

    OpenAIRE

    Senevirathne, Chamara; Pflum, Mary Kay H.

    2013-01-01

    Kinase-catalyzed protein phosphorylation is involved in a wide variety of cellular events. Development of methods to monitor phosphorylation is critical to understand cell biology. Our lab recently discovered kinase-catalyzed biotinylation, where ATP-biotin is utilized by kinases to label phosphopeptides or phosphoproteins with a biotin tag. To exploit kinase-catalyzed biotinylation for phosphoprotein purification and identification in a cellular context, the susceptibility of the biotin tag ...

  4. Mechanism of carbon monoxide reactions under high pressure catalyzed by acids and bases

    Energy Technology Data Exchange (ETDEWEB)

    Takezaki, Y.

    1978-05-01

    A review, based mainly on work done at Kyoto University, covers the mechanisms and kinetics of acid-catalyzed carbonylations, including the hydrogen fluoride-catalyzed addition of carbon monoxide to methallyl chloride, the sulfuric acid-catalyzed synthesis of succinic acid from acrylic acid, and the conversion of toluene to p-tolualdehyde in hydrogen fluoride/boron trifluoride by the Gattermann-Koch reaction; and of base-catalyzed reactions, including the production of methyl formate from methanol with 1,8-diazabicyclo (5,4,0)undec-7-ene catalyst and of malonic acid from potassium acetate and potassium carbonate. Graphs, tables, and 34 references.

  5. Control of particle size and morphology in compatiblized self-catalyzed co-polyimide/sio/sub 2/ nanocomposites

    International Nuclear Information System (INIS)

    The size of the silica particles and morphology of hybrids were controlled in copolyimide based hybrids through amino-silane functionalization of silica particles prepared in situ through a self-catalyzed sol-gel process using atmospheric moisture. The particles were generated using tetraethoxysilane in the uncompatiblized (UPISH) system whereas a mixture of 3-aminopropyltrietoxysilane and tetraethoxysilane was used in the compatiblized Co-PI/silica hybrid (CPISH) system. The properties of resulting hybrid films were measured by Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy, Thermogravimetirc Analysis, Dynamic Mechanical Analysis and Universal Testing Machine. FTIR results confirmed the formation of silica particles and Co-PI matrix. FE-SEM images revealed spherical silica particles with sharp boundaries in UPISH; whereas nano-sized coupled silica network structures with totally different morphologies were observed in CPISH system. The CPISH system exhibited better thermal stability, higher modulus and Tg values than UPISH system. The improvement in thermal and mechanical properties has been discussed with reference to morphological changes due to incorporation of 3-aminopropyltrietoxysilane in aerobic condition and in a self-catalyzed sol-gel process. (author)

  6. Direct Functionalization of Nitrogen Heterocycles via Rh-Catalyzed C-H Bond Activation

    Energy Technology Data Exchange (ETDEWEB)

    Lewis, Jared; Bergman, Robert; Ellman, Jonathan

    2008-02-04

    heterocycles, including azoles, azolines, dihydroquinazolines, pyridines, and quinolines, with a wide range of functionalized olefins. They demonstrated the utility of this methodology in the synthesis of natural products, drug candidates, and other biologically active molecules. In addition, they developed conditions to directly arylate these heterocycles with aryl halides. The initial conditions that used PCy{sub 3} as a ligand were successful only for aryl iodides. However, efforts designed to avoid catalyst decomposition led to the development of ligands based on 9-phosphabicyclo[4.2.1]nonane (Phoban) that also facilitated the coupling of aryl bromides. They then replicated the unique coordination environment, stability, and catalytic activity of this complex using the much simpler tetrahydrophosphepine ligands and developed conditions that coupled aryl bromides bearing diverse functional groups without the use of a glovebox or purified reagents. With further mechanistic inquiry, they anticipate that researchers will better understand the details of the aforementioned Rh-catalyzed C-H bond functionalization reactions, resulting in the design of more efficient and robust catalysts, expanded substrate scope, and new transformations.

  7. Metal-Catalyzed Oxidation and Photo-oxidation of Glucagon.

    Science.gov (United States)

    Zhang, Jian

    2016-08-01

    The oxidation of glucagon by the H2O2/Cu(2+) system and by simulated sunlight was studied using HPLC-MS methodologies. It was found that copper ion-catalyzed oxidation is much faster in the residue 1-12 region than in photo-oxidation, but it is slower than photo-oxidation in the residue 18-29 region. This difference is due to the unique feature of the primary sequence of glucagon. The residue 1-12 region contains His-1 and Asp-9 that can bind to Cu(2+) ions and catalyze the oxidation of His-1 and Tyr-10, while the residue 18-29 region lacks these charged residues near the liable Met-27 and Trp-25 and hence no catalysis by the neighboring groups occurs. Fragment (residue 13-17) was more stable than the other regions of the peptide toward photo-oxidation because it contains only one oxidizable residue, Tyr-13. These findings may help explain the mechanism of action of glucagon and provide some hints for the development of effective anti-diabetic drug molecules and stable glucagon formulations. PMID:27435200

  8. Acid-catalyzed kinetics of indium tin oxide etching

    International Nuclear Information System (INIS)

    We report the kinetic characterization of indium tin oxide (ITO) film etching by chemical treatment in acidic and basic electrolytes. It was observed that film etching increased under more acidic conditions, whereas basic conditions led to minimal etching on the time scale of the experiments. Quartz crystal microbalance was employed in order to track the reaction kinetics as a function of the concentration of hydrochloric acid and accordingly solution pH. Contact angle measurements and atomic force microscopy experiments determined that acid treatment increases surface hydrophilicity and porosity. X-ray photoelectron spectroscopy experiments identified that film etching is primarily caused by dissolution of indium species. A kinetic model was developed to explain the acid-catalyzed dissolution of ITO surfaces, and showed a logarithmic relationship between the rate of dissolution and the concentration of undisassociated hydrochloric acid molecules. Taken together, the findings presented in this work verify the acid-catalyzed kinetics of ITO film dissolution by chemical treatment, and support that the corresponding chemical reactions should be accounted for in ITO film processing applications. - Highlights: • Acidic conditions promoted indium tin oxide (ITO) film etching via dissolution. • Logarithm of the dissolution rate depended linearly on the solution pH. • Acid treatment increased ITO surface hydrophilicity and porosity. • ITO film etching led to preferential dissolution of indium species over tin species

  9. Muon catalyzed fusion: old and new aspects of energy production

    International Nuclear Information System (INIS)

    Muon catalyzed fusion of deuterium and tritium (μCF) yields the same energy gain per reaction as fusion with magnetic or inertial confinement (17.6 MeV). The crucial points of μCf are, however, very different, namely (a) the energy cost W(μ) for production of one μ- and (b) the number n of reactions a single muon can catalyze on the average. (b) is ultimately limited by the effective sticking probability ωf : n≤1/ωf. With ''standard'' methods one has W(μ)∼5 GeV, ωf = 0.5%. Hence a ''standard'' μCF reactor can never reach a net energy gain. To solve this problem, ways discussed since about a decade are to increase the efficiency by both (i) energy multiplication using a fissionable blanket and (ii) breeding. A new way to increase the safety of fission devices mostly due to Yu. Petrov is outlined. On the other hand there is a hope to lower W(μ) slightly and ωf drastically, the latter by artificial reactivation. New theoretical results for beam cooling in an omegatron type driven integrated μCF reactor, important for W(μ) and, in particular, ωf, is presented. (orig.)

  10. The mechanisms of platinum-catalyzed silicon nanowire growth

    International Nuclear Information System (INIS)

    Platinum (Pt) has been known as a catalyst material for vapor-liquid-solid (VLS) synthesis since the mid 1960s with the potential to grow electronic grade silicon nanowires (SiNWs). In contrast to gold-based growth, Pt-catalyzed SiNW synthesis has rarely been studied, most likely due to higher synthesis temperatures and the formation of multiple Pt silicide phases. Here we present the growth of SiNWs from a Pt catalyst deposited by a focused ion or electron beam, which opens new strategies for the assembly of Pt-catalyzed SiNW-based devices, as well as SiNW growth from Pt nanoparticles and thin films. We show that single-crystalline SiNWs exhibit either the well-known catalyst tip or a polycrystalline silicon tip so far not reported. The local Pt concentration was found to be one key parameter triggering the growth mode. The proposed growth model for both types of SiNWs is based on a solid-state silicide-mediated crystallization rather than VLS. The discussion of the growth modes is supported by a variation of several growth parameters and SiNW synthesis using the substrate materials silicon nitride, single-crystalline silicon, fused silica, and sapphire. (paper)

  11. Porous silicon formation during Au-catalyzed etching

    International Nuclear Information System (INIS)

    The formation of “black” nano-textured Si during the Au-catalyzed wet-chemical etch process was investigated with respect to photovoltaic applications. Cross-sectional scanning electron microscopy (SEM) images recorded at different stages of the etch process exhibit an evolution of a two-layer structure, consisting of cone-like Si hillocks covered with a nano-porous Si (np-Si) layer. Optical measurements confirm the presence of a np-Si phase which appears after the first ∼10 s of the etch process and continuously increases with the etch time. Furthermore, the etch process was investigated on Si substrates with different doping levels (∼0.01–100 Ω cm). SEM images show a transition from the two-layer morphology to a structure consisting entirely of np-Si for higher doping levels (<0.1 Ω cm). The experimental results are discussed on the basis of the model of a local electrochemical etch process. A better understanding of the metal-catalyzed etch process facilitates the fabrication of “black” Si on various Si substrates, which is of significant interest for photovoltaic applications

  12. IRC analysis of methanol carbonylation reaction catalyzed by rhodium complex

    Institute of Scientific and Technical Information of China (English)

    HAO Maorong; FENG Wenlin; JI Yongqiang; LEI Ming

    2004-01-01

    In the reaction cycle for methanol carbonylation catalyzed by Rh complex, the structure geometries of the reactant, intermediates, transition states and product of each elemental reaction have been studied by using the energy gradient method at HF/LANL2DZ level, and the changes of their potential profiles have also been calculated. Through IRC analyses of the transition states for each elemental reaction, it is confirmed that the various structure geometries obtained are stationary points on the cycle reaction pathway of methanol carbonylation catalyzed by Rh complex, and the changes are given in energies and structure geometries of the reactant molecules along the reaction pathway of lowest energy. It has been proposed that the geometrical conversions of intermediates play an important role during the cycle reaction. Through analyses of structure geometries, it has been suggested that, in addition to cis- and trans- structure exchange linkage of catalysis reactive species, the two pathways, cis- and trans-cata- lyzed cycle reactions, can also be linked through geometrical conversion of intermediates, of which the activation energy is 49.79 kJ/mol. Moreover, the reductive elimination elemental reaction may be neither cis-cycle nor trans- one, showing that the cycle reaction can be achieved through various pathways. However different the pathway, the oxidative addition elemental reaction of CH3I is the rate-controlling step.

  13. Acid base catalyzed transesterification kinetics of waste cooking oil

    Energy Technology Data Exchange (ETDEWEB)

    Jain, Siddharth; Sharma, M.P.; Rajvanshi, Shalini [Alternate Hydro Energy Centre, Indian Institute of Technology, Roorkee (India)

    2011-01-15

    The present study reports the results of kinetics study of acid base catalyzed two step transesterification process of waste cooking oil, carried out at pre-determined optimum temperature of 65 C and 50 C for esterification and transesterification process respectively under the optimum condition of methanol to oil ratio of 3:7 (v/v), catalyst concentration 1%(w/w) for H{sub 2}SO{sub 4} and NaOH and 400 rpm of stirring. The optimum temperature was determined based on the yield of ME at different temperature. Simply, the optimum concentration of H{sub 2}SO{sub 4} and NaOH was determined with respect to ME Yield. The results indicated that both esterification and transesterification reaction are of first order rate reaction with reaction rate constant of 0.0031 min{sup -1} and 0.0078 min{sup -1} respectively showing that the former is a slower process than the later. The maximum yield of 21.50% of ME during esterification and 90.6% from transesterification of pretreated WCO has been obtained. This is the first study of its kind which deals with simplified kinetics of two step acid-base catalyzed transesterification process carried under the above optimum conditions and took about 6 h for complete conversion of TG to ME with least amount of activation energy. Also various parameters related to experiments are optimized with respect to ME yield. (author)

  14. The mechanisms of platinum-catalyzed silicon nanowire growth

    Science.gov (United States)

    Hibst, N.; Knittel, P.; Biskupek, J.; Kranz, C.; Mizaikoff, B.; Strehle, S.

    2016-02-01

    Platinum (Pt) has been known as a catalyst material for vapor-liquid-solid (VLS) synthesis since the mid 1960s with the potential to grow electronic grade silicon nanowires (SiNWs). In contrast to gold-based growth, Pt-catalyzed SiNW synthesis has rarely been studied, most likely due to higher synthesis temperatures and the formation of multiple Pt silicide phases. Here we present the growth of SiNWs from a Pt catalyst deposited by a focused ion or electron beam, which opens new strategies for the assembly of Pt-catalyzed SiNW-based devices, as well as SiNW growth from Pt nanoparticles and thin films. We show that single-crystalline SiNWs exhibit either the well-known catalyst tip or a polycrystalline silicon tip so far not reported. The local Pt concentration was found to be one key parameter triggering the growth mode. The proposed growth model for both types of SiNWs is based on a solid-state silicide-mediated crystallization rather than VLS. The discussion of the growth modes is supported by a variation of several growth parameters and SiNW synthesis using the substrate materials silicon nitride, single-crystalline silicon, fused silica, and sapphire.

  15. Chloride-catalyzed corrosion of plutonium in glovebox atmospheres

    International Nuclear Information System (INIS)

    Characterization of glovebox atmospheres and the black reaction product formed on plutonium surfaces shows that the abnormally rapid corrosion of components in the fabrication line is consistent with a complex salt-catalyzed reaction involving gaseous hydrogen chloride (HCl) and water. Analytical data verify that chlorocarbon and HCl vapors are presented in stagnant glovebox atmospheres. Hydrogen chloride concentrations approach 7 ppm at some locations in the glovebox line. The black corrosion product is identified as plutonium monoxide monohydride (PuOH), a product formed by hydrolysis of plutonium in liquid water and salt solutions at room temperature. Plutonium trichloride (PuCl3) produced by reaction of HCl at the metal surface is deliquescent and apparently forms a highly concentrated salt solution by absorbing moisture from the glovebox atmosphere. Rapid corrosion is attributed to the ensuing salt-catalyzed reaction between plutonium and water. Experimental results are discussed, possible involvement of hydrogen fluoride (HF) is examined, and methods of corrective action are presented in this report

  16. Ionic Liquid Catalyzed Electrolyte for Electrochemical Polyaniline Supercapacitors

    Science.gov (United States)

    Inamdar, A. I.; Im, Hyunsik; Jung, Woong; Kim, Hyungsang; Kim, Byungchul; Yu, Kook-Hyun; Kim, Jin-Sang; Hwang, Sung-Min

    2013-05-01

    The effect of different wt.% of ionic liquid "1,6-bis (trimethylammonium-1-yl) hexane tetrafluoroborate" in 0.5 M LiClO4+PC electrolyte on the supercapacitor properties of polyaniline (PANI) thin film are investigated. The PANI film is synthesized using electropolymerization of aniline in the presence of sulfuric acid. The electrochemical properties of the PANI thin film are studied by cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy (EIS) measurements. The optimum amount of the ionic liquid is found to be 2 wt.% which provides better ionic conductivity of the electrolyte. The highest specific capacitance of 259 F/g is obtained using the 2 wt.% electrolyte. This capacitance remains at up to 208 F/g (80% capacity retention) after 1000 charge-discharge cycles at a current density of 0.5 mA/g. The PANI film in the 2 wt.% ionic liquid catalyzed 0.5 M LiClO4+PC electrolyte shows small electrochemical resistance, better rate performance and higher cyclability. The increased ionic conductivity of the 2 wt.% ionic liquid catalyzed electrolyte causes a reduction in resistance at the electrode/electrolyte interface, which can be useful in electrochemically-preferred power devices for better applicability.

  17. Build/Couple/Pair and Multifunctional Catalysis Strategies for the Synthesis of Heterocycles from Simple Starting Materials

    DEFF Research Database (Denmark)

    Ascic, Erhad

    Chapter 1. Build/Couple/Pair Strategy Combining the Petasis 3-Component Reaction with Ru-Catalyzed Ring-Closing Metathesis A “build/couple/pair” strategy for the efficient and concise (2-5 step) synthesis of structurally distinct skeletons is described. A Petasis 3-component reaction is used to...... synthesize anti-amino alcohols displaying pairwise reactive combinations of alkene moieties. Upon treatment with a ruthenium alkylidene catalyst, these dienes selectively undergo ring-closing metathesis reactions to form skeletally distinct heterocycles. In addition, a ruthenium-catalyzed tandem RCM...... generate reactive Nacyliminium intermediates which undergo intramolecular cyclization reactions with tethered heteroatom and carbon nucleophiles. In the tandem process, two new rings are formed, where a single metal catalyzes two mechanistically distinct reactions in one chemical operation. In this way, a...

  18. Palladium-Catalyzed One-Pot Reaction of Hydrazones, Dihaloarenes, and Organoboron Reagents: Synthesis and Cytotoxic Activity of 1,1-Diarylethylene Derivatives.

    Science.gov (United States)

    Roche, Maxime; Salim, Salim Mmadi; Bignon, Jérôme; Levaique, Hélène; Brion, Jean-Daniel; Alami, Mouad; Hamze, Abdallah

    2015-07-01

    A new three-component assembly reaction between N-tosylhydrazones, dihalogenated arenes, and boronic acids or boronate esters was developed, producing highly substituted 1,1-diarylethylenes in good yields. The two C-C bonds formed through this coupling have been catalyzed by a single Pd-catalyst in a one-pot fashion. It is noted that the one-pot pinacol boronate cross-coupling reaction generally provides products in high yields, offers an expansive substrate scope, and can address a broad range of aryl, styrene, vinyl, and heterocyclic olefinic targets. The scope of this one-pot coupling has been also extended to the synthesis of the 1,1-diarylethylene skeleton of the natural product ratanhine. The new compounds were evaluated for their cytotoxic activity, and this allowed the identification of compound 4ab that exhibits excellent antiproliferative activity in the nanomolar concentration range against HCT116 cancer cell lines. PMID:26036279

  19. Wet strength improvement of unbleached kraft pulp through laccase catalyzed oxidation.

    Science.gov (United States)

    Lund, M; Felby, C

    2001-06-01

    Previous investigations have shown that laccase catalyzed oxidation of lignin containing wood fibers can enhance the strength of medium density fiberboards. In the present work it was investigated if laccase treatment had any impact on the tensile strength of a high yield unbleached kraft pulp. Treatment with laccase alone had only a very little effect on the wet strength of the pulp, whereas addition of lignin rich extractives increased the wet strength after the enzyme treatment significantly. A mediated oxidation gave a similar improvement of the wet tensile strength although no lignin was added to the fiber suspension. Furthermore, it was found that a heat treatment combined with a mediated oxidation gave a higher improvement in wet tensile strength than could be accounted for by the individual treatments. No change in dry tensile strength from the laccase treatment was observed. It is suggested that the observed improvement in wet tensile strength is related to polymerization of lignin on fibers in the hand sheet and/or coupling of phenoxy radicals on lignin associated to adjacent fibers. For the different mediators studied, a correlation was found between oxygen consumption upon mediated oxidation and generation of wet strength in the pulp. PMID:11397456

  20. Interconversion between formate and hydrogen carbonate by tungsten-containing formate dehydrogenase-catalyzed mediated bioelectrocatalysis

    Directory of Open Access Journals (Sweden)

    Kento Sakai

    2015-09-01

    Full Text Available We have focused on the catalytic properties of tungsten-containing formate dehydrogenase (FoDH1 from Methylobacterium extorquens AM1 to construct a bioelectrochemical interconversion system between formate (HCOO− and hydrogen carbonate (HCO3−. FoDH1 catalyzes both of the HCOO oxidation and the HCO3− reduction with several artificial dyes. The bi-molecular reaction rate constants between FoDH1 and the artificial electron acceptors and NAD+ (as the natural electron acceptor show the property called a linear free energy relationship (LFER, indicating that FoDH1 would have no specificity to NAD+. Similar LFER is also observed for the catalytic reduction of HCO3−. The reversible reaction between HCOO− and HCO3− through FoDH1 has been realized on cyclic voltammetry by using methyl viologen (MV as a mediator and by adjusting pH from the thermodynamic viewpoint. Potentiometric measurements have revealed that the three redox couples, MV2+/MV·−+, HCOO−/HCO3−, FoDH1 (ox/red, reach an equilibrium in the bulk solution when the two-way bioelectrocatalysis proceeds in the presence of FoDH1 and MV. The steady-state voltammograms with two-way bioelectrocatalytic properties are interpreted on a simple model by considering the solution equilibrium.

  1. A Study of Fuel and Reactor Design for Platinum Nanoparticle Catalyzed Microreactors

    Directory of Open Access Journals (Sweden)

    Dylan McNally

    2015-01-01

    Full Text Available Typical microcombustion-based power devices entail the use of catalyst to sustain combustion in less than millimeter scale channels. This work explores the use of several other candidate fuels for ~8 nm diameter Pt particle catalyzed combustion within 800 μm channel width cordierite substrates. The results demonstrate while commercial hydrocarbon fuels such as methane, propane, butane, and ethanol can be used to sustain catalytic combustion, room temperature ignition was only observed using methanol-air mixtures. Fuels, other than methanol, required preheating at temperatures >200°C, yet repeated catalytic cycling similar to methanol-air mixtures was demonstrated. Subsequently, a new reactor design was investigated to couple with thermoelectric generators. The modified reactor design enabled ignition of methanol-air mixtures at room temperature with the ability to achieve repeat catalytic cycles. Preliminary performance studies achieved a maximum temperature difference ΔT of 55°C with a flow rate of 800 mL/min. While the temperature difference indicates a respectable potential for power generation, reduced exhaust temperature and improved thermal management could significantly enhance the eventual device performance.

  2. Coverage Effects on the Palladium-Catalyzed Synthesis of Vinyl Acetate: Comparison between Theory and Experiment

    Energy Technology Data Exchange (ETDEWEB)

    Calaza, Florencia; Stacchiola, Dario; Neurock, Matthew; Tysoe, Wilfred T.

    2010-02-24

    The high adsorbate coverages that form on the surfaces of many heterogeneous catalysts under steady-state conditions can significantly lower the activation energies for reactions that involve the coupling of two adsorbed intermediates while increasing those which result in adsorbate bond-breaking reactions. The influence of the surface coverage on the kinetics of metal-catalyzed reactions is often ignored in theoretical and even in some ultrahigh vacuum experimental studies. Herein, first principle density functional theoretical calculations are combined with experimental surface titration studies carried out over well-defined Pd(111) surfaces to explicitly examine the influence of coverage on the acetoxylation of ethylene to form vinyl acetate over Pd. The activation energies calculated for elementary steps in the Samanos and Moiseev pathways for vinyl acetate synthesis carried out on acetate-saturated palladium surfaces reveal that the reaction proceeds via the Samanos mechanism which is consistent with experimental results carried out on acetate-saturated Pd(111) surfaces. The rate-limiting step involves a β-hydride elimination from the adsorbed acetoxyethyl intermediate, which proceeds with an apparent calculated activation barrier of 53 kJ/mol which is in very good agreement with the experimental barrier of 55 ± 4 kJ/mol determined from kinetic measurements.

  3. Copper-Catalyzed Three-Component Reaction for Regioselective Aryl- and Heteroarylselenation of Indoles using Selenium Powder.

    Science.gov (United States)

    Luo, Dongping; Wu, Ge; Yang, Hang; Liu, Miaochang; Gao, Wenxia; Huang, Xiaobo; Chen, Jiuxi; Wu, Huayue

    2016-06-01

    A new and efficient copper-catalyzed C3 aryl- and heteroarylselenation of indoles employing selenium powder has been developed. The advantages of this chemistry involve the use of cheap selenating reagents, tolerance of a variety of functional groups, and practicality. In addition, this protocol has been further elaborated in an intramolecular phenylselenation of a (hetero) aryl C-H bond to construct an important motif of benzoselenopheno[3,2-b]indole. A preliminary mechanism study suggests that the reaction starts with a Ullman-type selenation between aryl iodides and selenium, followed by an oxidative cross-coupling with indole. The utility of this method has been demonstrated in an efficient gram-scale synthesis and an application to the synthesis of tubulin polymerization inhibitor. PMID:27191713

  4. Ligand-Free, Cu- and Fe-Catalyzed Selective Ring-Opening Arylations of Benzoxazoles with Aryl Iodides.

    Science.gov (United States)

    He, Yue; Mao, Jincheng; Rong, Guangwei; Yan, Hong; Zhang, Guoqi

    2016-06-01

    Cu- or Fe-based catalyst systems have been reported to selectively catalyze the N,N-diarylation or N-monoarylation of benzoxazoles ring-opening with aryl iodides in the absence of additional added ligand in polyethylene glycol under an inert atmosphere. Two types of coupling products (triphenylamines and diphenylamines) have been examined and the reaction routes can be simply controlled by changing the metal salts (Cu or Fe) as catalyst. A range of substrates have been investigated for the diverse reactions, and the corresponding arylation products were achieved in good to high yields. This selective, low-cost, and environmentally friendly protocol displays great potential for replacing existing methodologies as well as extending the synthetic applications of benzoxazoles. PMID:27037845

  5. Ligand-Controlled Synthesis of Azoles via Ir-Catalyzed Reactions of Sulfoxonium Ylides with 2-Amino Heterocycles.

    Science.gov (United States)

    Phelps, Alicia M; Chan, Vincent S; Napolitano, José G; Krabbe, Scott W; Schomaker, Jennifer M; Shekhar, Shashank

    2016-05-20

    An iridium-catalyzed method was developed for the synthesis of imidazo-fused pyrrolopyrazines. The presence or absence of a nitrogenated ligand controlled the outcome of the reaction, leading to simple β-keto amine products in the absence of added ligand and the cyclized 7- and 8-substituted-imidazo[1,2-a]pyrrolo[2,3-e]pyrazine products in the presence of ligand. This catalyst control was conserved across a variety of ylide and amine coupling partners. The substrate was shown to act as a ligand for the iridium catalyst in the absence of other ligands via NMR spectroscopy. Kinetic studies indicated that formation of the Ir-carbene was reversible and the slow step of the reaction. These mechanistic investigations suggest that the β-keto amine products form via an intramolecular carbene N-H insertion, and the imidazopyrrolopyrazines form via an intermolecular carbene N-H insertion. PMID:27104299

  6. LIPASE-CATALYZED TRANSESTERIFICATION OF PALM KERNEL OIL WITH DIALKYLCARBONATES

    Directory of Open Access Journals (Sweden)

    Tjahjono Herawan

    2014-01-01

    Full Text Available Lipase-catalyzed transesterifications-especially in a solvent-free medium-are important for industrial applications because such systems would have an enormous advantage by avoiding the problem of separation, toxicity and flammability of organic solvents. However, the organic solvent-free alcoholysis, especially methanolysis, does not give high conversions. The same problem also occurs when ethyl or methyl acetate are used as acyl acceptors. The main problems of lipase-catalyzed organic solvent-free alcoholysis are first, the solubility of the plant oil in the substrate or solvent and second, the fact that transesterification is an equilibrium reaction. Dialkyl carbonates, versatile compounds due to their chemical reactivity and physical properties, may provide an alternative to solve both problems. Using dialkyl carbonates transesterification is not an equilibrium reaction, because the intermediate compound immediately decomposes to carbon dioxide and an alcohol. Moreover, dialkyl carbonates (especially dimethyl carbonate are cheap and widely available. For single step lipase-catalyzed transesterification of palm kernel oil, diakyl carbonates (in this case dimethyl and diethyl carbonate gave better yields compared to those of short chain alcohols. The rate of ester formation with dialkyl carbonates as substrate was about 6-7 times higher than that obtained with short chain alcohols. The formation of esters was gradually increased by a higher enzyme amount from 5-20% (w/w of oil for 8 h reaction time. However from the economic point of view, an enzyme amount of 10% on the weight base of oil was proposed for further reaction. Generally, the highest ester formation was observed when a temperature of 60°C was used. However, in the case of dimethyl carbonate little difference was observed at reaction temperatures of 60 and 70oC and the reactions proceeded nearly identically. The esters formation increased drastically up to more than 70% when water

  7. Assessment of the Full Compatibility of Copper(I)-Catalyzed Alkyne-Azide Cycloaddition and Oxime Click Reactions for bis-Labelling of Oligonucleotides

    OpenAIRE

    Estalayo-Adriàn, Sandra; Lartia, Rémy; Meyer, Albert; Vasseur, Jean-Jacques; Morvan, François; Defrancq, Eric

    2014-01-01

    The conjugation of oligonucleotides with reporters is of great interest for improving their intrinsic properties or endowing new ones. In this context, we report herein a new procedure for the bis-labelling of oligonucleotides through oxime ligation (Click-O) and copper(I)-catalyzed alkyne–azide cycloaddition (Click-H). 5′-Azido and 3′-aldehyde precursors were incorporated into oligonucleotides, and subsequent coupling reactions through Click-O and Click-H (or vice versa) were successfully ac...

  8. Synthesis of N-Aryl-2-allyl Pyrrolidines via Palladium-catalyzed Carboamination Reactions of γ-(N-Arylamino)alkenes with Vinyl Bromides

    OpenAIRE

    Ney, Joshua E.; Hay, Michael B.; Yang, Qifei; Wolfe, John P.

    2005-01-01

    A palladium-catalyzed carboamination reaction of γ-N-arylamino alkenes with vinyl bromides that affords N-aryl-2-allyl pyrrolidines is described. These reactions proceed with high diastereoselectivity for the formation of trans-2,3- and cis-2,5-disubstituted pyrrolidines. Conditions for a tandem N-arylation/carboamination sequence that leads to the formation of an N-aryl-2-allyl pyrrolidine or indoline via the coupling of a primary γ-amino alkene, an aryl bromide, and a vinyl bromide are also...

  9. Coupling Reaction of Organoboronic Acids with Chloropyrimidines and Trichlorotriazine

    Institute of Scientific and Technical Information of China (English)

    TAN Jiu-Qing谭久青; CHANG Jian-Hua常建华; DENG Min-Zhi邓敏智

    2004-01-01

    Pd-catalyzed cross-coupling reactions of chloropyrimidines with alkenylboronic acids readily proceed to give the corresponding alkenylpyrimidines in high to excellent yields. The coupling reaction of 2,4-dichloropyrimidine or 2,4,6-trichloropyrimidine with one equivalent of alkenylboronic acid occurred more easily on 4-position than on2-position, which implied that the reaction is highly regioselective. The reaction is stereospecific since the configuration of C=C remained intact. The preliminary study on the cross-coupling reactions of 2,4,6-trichlorotriazine with one equivalent of arylboronic acids showed that the reactions afforded the monosubstituted triazines in moderate yields. The effect of steric hindrance of the substitutents on the reactions was found.

  10. Metal triflate-mediated coupling of allylgermanes with thiols: a facile route to thiogermanes.

    Science.gov (United States)

    Kuciński, K; Pawluć, P; Hreczycho, G

    2015-06-28

    A novel coupling reaction of thiols with (2-methylallyl)germanes catalyzed by metal triflates has been developed. This reaction provides a direct and efficient method to afford thiogermanes and opens a valuable and general synthetic route for the Ge-S cross-coupling with the elimination of isobutylene as a single by-product. Scandium(iii) triflate demonstrates the highest catalytic activity among the tested triflates. All reactions were carried out under extremely mild conditions to give thiogermanes in excellent yields. This Ge-S coupling reaction shows high generality for the variety of thiols. PMID:26006777

  11. Application of organoselenides in the Suzuki, Negishi, Sonogashira and Kumada cross-coupling reactions.

    Science.gov (United States)

    Stein, A L; Bilheri, F N; Zeni, G

    2015-11-01

    We reported herein the regio- and stereoselective palladium-catalyzed cross-coupling reactions of unsaturated organoselenides with Sonogashira, Suzuki, Negishi and Kumada partners. The reactions were in general carried out with Pd(PPh3)4 (10 mol%), in DMF at 80 °C to afford the cross-coupling products in good yields. This strategy tolerated a wide range of substrates, such as alkynyl, vinyl, aryl and heteroaryl selenides with a variety of sensitive functional groups and gave the cross-coupling products in good yields. PMID:26348229

  12. Palladium- and Copper-Catalyzed Solution Phase Synthesis of a Diverse Library of Isoquinolines

    OpenAIRE

    Roy, Sudipta; Roy, Sujata; Neuenswander, Benjamin; Hill, David; Larock, Richard C.

    2009-01-01

    The solution phase synthesis of a 111 member isoquinoline library is described. The isoquinoline scaffold has been accessed through the palladium- and copper-catalyzed cyclization of iminoalkynes and the palladium-catalyzed iminoannulation of internal alkynes, followed by diversification of hydroxyl functionality where it is present.

  13. Kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid

    NARCIS (Netherlands)

    Girisuta, B.; Janssen, L. P. B. M.; Heeres, H. J.

    2007-01-01

    A variety of interesting bulk chemicals is accessible by the acid-catalyzed hydrolysis of cellulose. An interesting example is levulinic acid, a versatile precursor for fuel additives, polymers, and resins. A detailed kinetic study on the acid-catalyzed hydrolysis of cellulose to levulinic acid is r

  14. ROLE OF COPPER,ZINC-SUPEROXIDE DISMUTASE IN CATALYZING NITROTYROSINE FORMATION IN MURINE LIVER

    Science.gov (United States)

    The solely known function of Cu,Zn-superoxide dismutase (SOD1) is to catalyze the dismutation of superoxide anion into hydrogen peroxide. Our objective was to determine if SOD1 catalyzed murine liver protein nitration induced by acetaminophen (APAP) and lipopolysaccharide (LPS). Liver and plasma ...

  15. Fe-Catalyzed reactions of 2-chloro-1,7-dienes and allylmalonates

    OpenAIRE

    Drabina, Pavel; Nečas, David; Sedlák, Miloš; Kotora, Martin

    2007-01-01

    Fe(III)(BIAP)Cl-3 complex catalyzes alkylative cyclization of 2-chloro-1,7-heptadiene in the presence of triethylaluminum. It also catalyzes deallylation of certain 2-allyl-2-substituted malonates under the same reaction conditions. (c) 2007 Elsevier Ltd. All rights reserved.

  16. Synthesis of star and H-shape polymers via a combination of cobalt-mediated radical polymerization and nitrone-mediated radical coupling reactions

    OpenAIRE

    Detrembleur, Christophe; Debuigne, Antoine; Altintas, Ozcan; Conradi, Matthias; Wong, Edgar H. H.; Jerome, Christine; Barner-Kowollik, Christopher; Junkers, Thomas

    2012-01-01

    Via consecutive cobalt-mediated radical polymerization (CMRP), nitrone-mediated radical coupling (NMRC) and copper catalyzed azide-alkyne cycloaddition (CuAAC), polymers with mikto-arm star and H-shape architecture were synthesized. Poly(vinyl acetate)(40)-block-poly(acrylonitrile)(78)-Co(acac)(2) polymers were synthesized via CMRC and subsequently coupled using an alkyne functional nitrone. The coupling efficiency of the NMRC process was assessed employing N-tert-butyl alpha-phenyl nitrone (...

  17. Mild and Efficient Nickel-Catalyzed Heck Reactions with Electron-Rich Olefins

    DEFF Research Database (Denmark)

    Gøgsig, Thomas; Kleimark, Jonatan; Lill, Sten O. Nilsson;

    2012-01-01

    A new efficient protocol for the nickel-catalyzed Heck reaction of aryl triflates with vinyl ethers is presented. Mild reaction conditions that equal those of the corresponding palladium-catalyzed Heck reaction are applied, representing a practical and more sustainable alternative to the conventi......A new efficient protocol for the nickel-catalyzed Heck reaction of aryl triflates with vinyl ethers is presented. Mild reaction conditions that equal those of the corresponding palladium-catalyzed Heck reaction are applied, representing a practical and more sustainable alternative to the...... proved compatible, and the corresponding aryl methyl ketone could be secured after hydrolysis in yields approaching quantitative. Good functional group tolerance was observed matching the characteristics of the analogous Pd-catalyzed Heck reaction. The high levels of catalytic activity were explained by...

  18. Cobalt catalyzed hydroesterification of a wide range of olefins

    Energy Technology Data Exchange (ETDEWEB)

    Van Rensburg, H.; Hanton, M.; Tooze, R.P.; Foster, D.F. [Sasol Technology UK, St Andrews (United Kingdom)

    2011-07-01

    Petrochemical raw materials are an essential raw material for the production of detergents with a substantial portion of synthetic fatty alcohols being produced via hydroformylation of oil or coal derived olefins. Carbonylation processes other than hydroformylation have to date not been commercially employed for the production of fatty esters or alcohols. In this document we highlight the opportunities of converting olefins to esters using cobalt catalyzed alkoxycarbonylation. This process is highly versatile and applicable to a wide range of olefins, linear or branched, alpha or internal in combination with virtually any chain length primary or secondary alcohol allowing the synthesis of a diverse array of compounds such as ester ethoxylated surfactants, methyl branched detergents, lubricants and alkyl propanoates. Furthermore, alkoxycarbonylation of a broad olefin/paraffin hydrocarbon range could be used to produce the corresponding broad cut detergent alcohols. (orig.)

  19. Hemoglobin-catalyzed fluorometric method for the determination of glutathione

    Science.gov (United States)

    Wang, Ruiqiang; Tang, Lin; Li, Hua; Wang, Yi; Gou, Rong; Guo, Yuanyuan; Fang, Yudong; Chen, Fengmei

    2016-01-01

    A new spectrofluorometric method for the determination of glutathione based on the reaction catalyzed by hemoglobin was reported. The reaction product gave a highly fluorescent intensity with the excitation and emission wavelengths of 320.0 nm and 413.0 nm, respectively. The optimum experimental conditions were investigated. Results showed that low concentration glutathione enhanced the fluorescence intensity significantly. The line ranges were 1.0 × 10-6-1.0 × 10-5 mol L-1 of glutathione and 6.0 × 10-10 mol L-1-1.0 × 10-8 mol L-1, respectively. The detection limit was calculated to be 1.1 × 10-11 mol L-1. The recovery test by the standard addition method gave values in the range of 90.78%-102.20%. This method was used for the determination of glutathione in synthetic and real samples with satisfactory results.

  20. Catalyzed deuterium fueled reversed-field pinch reactor assessment

    International Nuclear Information System (INIS)

    This study is part of a Department of Energy supported alternate fusion fuels program at Science Applications International Corporation. The purpose of this portion of the study is to perform an assessment of a conceptual compact reversed-field pinch reactor (CRFPR) that is fueled by the catalyzed-deuterium (Cat-d) fuel cycle with respect to physics, technology, safety, and cost. The Cat-d CRFPR is compared to a d-t fueled fusion reactor with respect to several issues in this study. The comparison includes cost, reactor performance, and technology requirements for a Cat-d fueled CRFPR and a comparable cost-optimized d-t fueled conceptual design developed by LANL

  1. Multi-enzyme catalyzed processes: Next generation biocatalysis

    DEFF Research Database (Denmark)

    Andrade Santacoloma, Paloma de Gracia; Sin, Gürkan; Gernaey, Krist;

    2011-01-01

    Biocatalysis has been attracting increasing interest in recent years. Nevertheless, most studies concerning biocatalysis have been carried out using single enzymes (soluble or immobilized). Currently, multiple enzyme mixtures are attractive for the production of many compounds at an industrial...... level. In this review, a classification of multienzyme-catalyzed processes is proposed. Special emphasis is placed on the description of multienzyme ex-vivo systems where several reactions are carried out by a combination of enzymes acting outside the cell. Furthermore, reaction and process...... considerations for mathematical modeling are discussed for the specific case where the synthetic reactions are carried out in a single reactor, the so-called multienzyme ‘in-pot’ process. In addition, options for multienzyme ‘in-pot’ process improvements via process engineering and enzyme immobilization...

  2. Towards a methanol economy: Zeolite catalyzed production of synthetic fuels

    DEFF Research Database (Denmark)

    Mentzel, Uffe Vie

    The main focus of this thesis is zeolite catalyzed conversion of oxygenates to hydrocarbon fuels and chemicals. Furthermore, conversion of ethane to higher hydrocarbons has also been studied. After a brief introduction to the concept of “the methanol economy” in the first chapter, the second...... chapter is a literature study of Mobil’s “methanol to hydrocarbons” (MTH) process, giving an overview of the history of the process, the nature of the employed catalysts, and the reaction mechanism. In the third chapter, a series of experiments concerning co conversion of ethane and methanol over a...... commercial H-ZSM-5 zeolite impregnated with gallium and/or molybdenum is described. The object was to investigate if the presence of methanol in the feed could enhance the conversion of ethane, but in all cases the opposite is observed; the presence of methanol actually suppresses the conversion of ethane...

  3. Solid acid catalyzed biodiesel production from waste cooking oil

    Energy Technology Data Exchange (ETDEWEB)

    Jacobson, Kathlene; Gopinath, Rajesh; Meher, Lekha Charan; Dalai, Ajay Kumar [Catalysis and Chemical Reaction Engineering Laboratories, Department of Chemical Engineering, University of Saskatchewan, 57 Campus Drive, Saskatoon, SK, S7N 5A9 (Canada)

    2008-12-17

    Various solid acid catalysts were evaluated for the production of biodiesel from low quality oil such as waste cooking oil (WCO) containing 15 wt.% free fatty acids. The zinc stearate immobilized on silica gel (ZS/Si) was the most effective catalyst in simultaneously catalyzing the transesterification of triglycerides and esterification of free fatty acid (FFA) present in WCO to methyl esters. The optimization of reaction parameters with the most active ZS/Si catalyst showed that at 200 C, 1:18 oil to alcohol molar ratio and 3 wt.% catalysts loading, a maximum ester yield of 98 wt.% could be obtained. The catalysts were recycled and reused many times without any loss in activity. (author)

  4. Specific miRNA Stabilization by Gld2-Catalyzed Monoadenylation

    Directory of Open Access Journals (Sweden)

    Andrea D’Ambrogio

    2012-12-01

    Full Text Available MicroRNAs (miRNAs are small, noncoding RNAs that inhibit translation and promote mRNA decay. The levels of mature miRNAs are the result of different rates of transcription, processing, and turnover. The noncanonical polymerase Gld2 has been implicated in the stabilization of miR-122, possibly through catalyzing 3′ monoadenylation; however, there is little evidence that this relationship is one of cause and effect. Here, we biochemically characterize Gld2’s involvement in miRNA monoadenylation and its effect on miRNA stability. We find that Gld2 directly monoadenylates and stabilizes specific miRNA populations in human fibroblasts and that sensitivity to monoadenylation-induced stability depends on nucleotides in the miRNA 3′ end. These results establish a mechanism of miRNA stability and resulting posttranscriptional gene regulation.

  5. WILDCAT: a catalyzed D-D tokamak reactor

    International Nuclear Information System (INIS)

    WILDCAT is a conceptual design of a catalyzed D-D, tokamak, commercial, fusion reactor. WILDCAT utilizes the beneficial features of no tritium breeding, while not extrapolating unnecessarily from existing D-T designs. The reactor is larger and has higher magnetic fields and plasma pressures than typical D-T devices. It is more costly, but eliminates problems associated with tritium breeding and has tritium inventories and throughputs approximately two orders of magnitude less than typical D-T reactors. There are both a steady-state version with Alfven-wave current drive and a pulsed version. Extensive comparison with D-T devices has been made, and cost and safety analyses have been included. All of the major reactor systems have been worked out to a level of detail appropriate to a complete, conceptual design

  6. Synthesis of Rosin Acid Starch Catalyzed by Lipase

    Directory of Open Access Journals (Sweden)

    Rihui Lin

    2014-01-01

    Full Text Available Rosin, an abundant raw material from pine trees, was used as a starting material directly for the synthesis of rosin acid starch. The esterification reaction was catalyzed by lipase (Novozym 435 under mild conditions. Based on single factor experimentation, the optimal esterification conditions were obtained as follows: rosin acid/anhydrous glucose unit in the molar ratio 2 : 1, reaction time 4 h at 45°C, and 15% of lipase dosage. The degree of substitution (DS reaches 0.098. Product from esterification of cassava starch with rosin acid was confirmed by FTIR spectroscopy and iodine coloration analysis. Scanning electron microscopy and X-ray diffraction analysis showed that the morphology and crystallinity of the cassava starch were largely destroyed. Thermogravimetric analysis indicated that thermal stability of rosin acid starch decreased compared with native starch.

  7. Ti-catalyzed straightforward synthesis of exocyclic allenes.

    Science.gov (United States)

    Muñoz-Bascón, Juan; Hernández-Cervantes, Carmen; Padial, Natalia M; Alvarez-Corral, Míriam; Rosales, Antonio; Rodríguez-García, Ignacio; Oltra, J Enrique

    2014-01-13

    Exocyclic allenes constitute useful building blocks in organic synthesis and have recently been identified as key intermediates in the synthesis of natural products. Here the first general method for the most straightforward synthesis of exocyclic allenes reported to date is presented. This method is based on the Barbier-type cyclization of propargyl halides catalyzed by titanium; a safe, abundant, and ecofriendly metal. The reaction proceeds under mild conditions compatible with different functional groups and provides good yields of five-, six-, and seven-membered carbocycles and nitrogen-containing heterocycles bearing an exocyclic allene group. Experimental evidence supporting the proposed reaction mechanism is also provided. Moreover, this procedure can be carried out in an enantioselective manner by using chiral titanocene(III) catalysts. The utility of this method has been proved in the synthesis of the natural alkaloid stemoamide. PMID:24339337

  8. Solvent effects in acid-catalyzed biomass conversion reactions.

    Science.gov (United States)

    Mellmer, Max A; Sener, Canan; Gallo, Jean Marcel R; Luterbacher, Jeremy S; Alonso, David Martin; Dumesic, James A

    2014-10-27

    Reaction kinetics were studied to quantify the effects of polar aprotic organic solvents on the acid-catalyzed conversion of xylose into furfural. A solvent of particular importance is γ-valerolactone (GVL), which leads to significant increases in reaction rates compared to water in addition to increased product selectivity. GVL has similar effects on the kinetics for the dehydration of 1,2-propanediol to propanal and for the hydrolysis of cellobiose to glucose. Based on results obtained for homogeneous Brønsted acid catalysts that span a range of pKa values, we suggest that an aprotic organic solvent affects the reaction kinetics by changing the stabilization of the acidic proton relative to the protonated transition state. This same behavior is displayed by strong solid Brønsted acid catalysts, such as H-mordenite and H-beta. PMID:25214063

  9. Radiochemical methods for studying lipase-catalyzed interesterification of lipids

    International Nuclear Information System (INIS)

    Reactions involving lipase-catalyzed interesterification of lipids, which are of commendable interest in biotechnology, have been monitored and assayed by radiochemical methods using 14C-labeled substrates. Medium chain (C12 plus C14) triacylglycerols were reacted in the presence of an immobilized lipase from Mucor miehei and hexane at 450C with methyl [1-14C]oleate, [1-14C]oleic acid, [carboxyl-14C]trioleoylglycerol, [1-14C]octadecenyl alcohol, and [U-14C]glycerol, each of known specific activity. The reactions were monitored and the rate of interesterification determined by radio thin layer chromatography from the incorporation of radioactivity into acyl moieties of triacylglycerols (from methyl oleate, oleic acid, and trioleoylglycerol), alkyl moieties of wax esters (from octadecenyl alcohol), and into glycerol backbone of monoacylglycerols and diacylglycerols (from glycerol). (orig.)

  10. Cathodic oxygen reduction catalyzed by bacteria in microbial fuel cells.

    Science.gov (United States)

    Rabaey, Korneel; Read, Suzanne T; Clauwaert, Peter; Freguia, Stefano; Bond, Philip L; Blackall, Linda L; Keller, Jurg

    2008-05-01

    Microbial fuel cells (MFCs) have the potential to combine wastewater treatment efficiency with energetic efficiency. One of the major impediments to MFC implementation is the operation of the cathode compartment, as it employs environmentally unfriendly catalysts such as platinum. As recently shown, bacteria can facilitate sustainable and cost-effective cathode catalysis for nitrate and also oxygen. Here we describe a carbon cathode open to the air, on which attached bacteria catalyzed oxygen reduction. The bacteria present were able to reduce oxygen as the ultimate electron acceptor using electrons provided by the solid-phase cathode. Current densities of up to 2.2 A m(-2) cathode projected surface were obtained (0.303+/-0.017 W m(-2), 15 W m(-3) total reactor volume). The cathodic microbial community was dominated by Sphingobacterium, Acinetobacter and Acidovorax sp., according to 16S rRNA gene clone library analysis. Isolates of Sphingobacterium sp. and Acinetobacter sp. were obtained using H(2)/O(2) mixtures. Some of the pure culture isolates obtained from the cathode showed an increase in the power output of up to three-fold compared to a non-inoculated control, that is, from 0.015+/-0.001 to 0.049+/-0.025 W m(-2) cathode projected surface. The strong decrease in activation losses indicates that bacteria function as true catalysts for oxygen reduction. Owing to the high overpotential for non-catalyzed reduction, oxygen is only to a limited extent competitive toward the electron donor, that is, the cathode. Further research to refine the operational parameters and increase the current density by modifying the electrode surface and elucidating the bacterial metabolism is warranted. PMID:18288216

  11. Monomeric G protein-coupled receptor rhodopsin in solution activates its G protein transducin at the diffusion limit

    OpenAIRE

    Ernst, Oliver P.; Gramse, Verena; Kolbe, Michael; Hofmann, Klaus Peter; Heck, Martin

    2007-01-01

    G protein-coupled receptors mediate biological signals by stimulating nucleotide exchange in heterotrimeric G proteins (Gαβγ). Receptor dimers have been proposed as the functional unit responsible for catalytic interaction with Gαβγ. To investigate whether a G protein-coupled receptor monomer can activate Gαβγ, we used the retinal photoreceptor rhodopsin and its cognate G protein transducin (Gt) to determine the stoichiometry of rhodopsin/Gt binding and the rate of catalyzed nucleotide exchan...

  12. Growth and Raman spectroscopy studies of gold-free catalyzed semiconductor nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Zardo, Ilaria

    2010-12-15

    The present Ph.D. thesis proposes two aims: the search for catalysts alternative to gold for the growth of silicon nanowires and the investigation of the structural properties of the gold-free catalyzed Si, Ge, and GaAs nanowires. The successful growth of gold free catalyzed silicon nanowires was obtained using Ga and In as catalyst. Hydrogen plasma conditions were needed during the growth process. We proposed a growth mechanism where the role of the hydrogen plasma is taken into account. The influence of the growth conditions on nanowire growth morphology and structural properties was investigated in detail. The TEM studies showed the occurrence of different kind of twin defects depending on the nanowire growth direction. The intersection of twins in different spatial directions in <111>-oriented nanowires or the periodicity of highly dense twins in <112>-oriented nanowires leads to the formation of hexagonal domains embedded in the diamond silicon structure. A simple crystallographic model which illustrates the formation of the hexagonal phase was proposed. The presence of the hexagonal domains embedded in the diamond silicon structure was investigated also by means of Raman spectroscopy. The measured frequencies of the E2g and A1g modes were found to be in agreement with frequencies expected from phonon dispersion folding. An estimation of the percentage of hexagonal structure with respect to the cubic structure was given. The relative percentage of the two structures was found to change with growth temperature. Spatially resolved Raman scattering experiments were also realized on single Si nanowires. The lattice dynamics of gold-free catalyzed Ge and GaAs nanowires was studied by means of Raman spectroscopy. We performed spatially resolved Raman spectroscopy experiments on single crystalline- amorphous core-shell Ge nanowires. The correlation with TEM studies on nanowires grown under the same conditions and with AFM measurements realized of the same nanowires

  13. [Desire disorders in the couple: accident, dream, sexuality].

    Science.gov (United States)

    Stauffacher, M; Godat, A

    2013-03-20

    Eros, as few only would doubt about it, takes part in the deepest and most intimate area of the human being. Our contemporaries attach great importance to sexuality, but feed the illusion that mastering it could lead to miracles in the couple. We suggest that giving up control and committing himself to fully listening to the patient, the physician will be able to orient him in the blind rules of desire and to accept fortuity. Unexpected (?) accident, dream, hypnosis, often powerfully catalyze changes. Some clinical situations are described in this article with their evolution as consultations develop, without foreseeing their interpretation. PMID:23547363

  14. Biorhythm in Couple Counseling

    Science.gov (United States)

    Araoz, Daniel L.

    1977-01-01

    Twelve couples in marital counseling were studied during 12 months on the basis of their biorhythms. For each couple a compatibility percentage was obtained. It was found that difficulties in their interaction correlated highly with dissonance in their biorhythms. (Author)

  15. Kinetics of thermal decomposition of nano magnesium oxide catalyzed ammonium perchlorate

    International Nuclear Information System (INIS)

    Arrhenius kinetic parameters of ammonium perchlorate (AP) catalyzed with nano-sized magnesium oxide (MgO) has been determined in this work. Nano particles of MgO with an average size of approximately 20 to 30 nm have been used to catalyze the AP. The particles were characterized using Scanning electron microscope (SEM) and X-ray diffraction (XRD) techniques before mixing with AP. Simultaneous Thermal Analysis (STA) shows that MgO nanoparticles have a strong catalytic effect on the thermal decomposition of ammonium perchlorate. The addition of MgO nano particles reduces the two stage decomposition of ammonium perchlorate to a single stage. Arrhenius kinetic parameters of pure and the catalyzed AP have been calculated using non isothermal kinetic approach based on Kissinger method. The comparison of the thermal behavior and kinetic parameters of pure and catalyzed AP has also been carried out to elucidate the reaction mechanism. The results show that the activation energy of the catalyzed AP has increased from 138.1 kJ/mole to 159.1kJ/mole. The rate of reaction, however, has increased in the catalyzed AP showing that it has become more reactive by the addition of MgO nano particles. The enthalpy of activation has increased by 16 percent in the catalyzed AP. (author)

  16. Spectroscopic and QM/MM investigations of Chloroperoxidase catalyzed degradation of orange G.

    Science.gov (United States)

    Zhang, Rui; He, Qinghao; Huang, Yi; Wang, Xiaotang

    2016-04-15

    Chloroperoxidase (CPO), a heme-thiolate protein, from Caldariomyces fumago catalyzes a plethora of reactions including halogenation, dismutation, epoxidation, and oxidation. Although all CPO-catalyzed reactions go through a common intermediate, compound I, different mechanisms are followed in subsequent transformations. To understand the mechanism of CPO-catalyzed halide-dependent degradation of orange G, the role of halide and pH was systematically investigated. It is revealed that formation and protonation of compound X, a long-sought after hypochlorite heme adduct intermediate existed during CPO-catalyzed halide-dependent reactions, significantly lowers the reaction barrier and increases the efficiency of CPO-catalyzed orange G degradation. The extremely acidic optimal reaction pH suggests the protonation of a residue, presumably, Glu 183 in CPO catalysis. Halide dependent studies showed that Kcat is higher in the presence of Br(-) than in the presence of Cl(-). The degradation products of orange G indicate the cleavage at a single position of orange G, demonstrating a high regioselectivity of CPO-catalyzed degradation. Based on our kinetic, NMR and QM/MM studies, the mechanism of CPO-catalyzed orange G degradation was proposed. PMID:26926259

  17. Lipase catalyzed ester synthesis for food processing industries

    Directory of Open Access Journals (Sweden)

    Aravindan Rajendran

    2009-02-01

    Full Text Available Lipases are one of the most important industrial biocatalyst which catalyzes the hydrolysis of lipids. It can also reverse the reaction at minimum water activity. Because of this pliable nature, it is widely exploited to catalyze the diverse bioconversion reactions, such as hydrolysis, esterification, interesterification, alcoholysis, acidolysis and aminolysis. The property to synthesize the esters from the fatty acids and glycerol promotes its use in various ester synthesis. The esters synthesized by lipase finds applications in numerous fields such as biodiesel production, resolution of the recemic drugs, fat and lipid modification, flavour synthesis, synthesis of enantiopure pharmaceuticals and nutraceuticals. It plays a crucial role in the food processing industries since the process is unaffected by the unwanted side products. Lipase modifications such as the surfactant coating, molecular imprinting to suit for the non-aqueous ester synthesis have also been reported. This review deals with lipase catalyzed ester synthesis, esterification strategies, optimum conditions and their applications in food processing industries.Lipases são catalizadores industriais dos mais importantes, os quais catalizam a hidrólise de lipídeos. Também podem reverter a reação a um mínimo de atividade de água. Devido sua natureza flexível, é amplamente explorada para catalizar uma diversidade de reações de bioconversão como hidrólise, esterificação, interesterificação, alcoólise, acidólise e aminólise. A propriedade de síntese de esteres a partir de ácidos graxos e glicerol promoveu seu uso em várias sínteses de esteres. Os esteres sintetizados por lipases encontram aplicação em numerosos campos como a produção de biodiesel, resolução de drogas racêmicas, modificação de gorduras e lipídios, sintese de aromas, síntese de produtos farmacêuticos enantiopuro e nutracêuticos. As lipases possuem um papel crucial nas indústrias de

  18. High power density yeast catalyzed microbial fuel cells

    Science.gov (United States)

    Ganguli, Rahul

    Microbial fuel cells leverage whole cell biocatalysis to convert the energy stored in energy-rich renewable biomolecules such as sugar, directly to electrical energy at high efficiencies. Advantages of the process include ambient temperature operation, operation in natural streams such as wastewater without the need to clean electrodes, minimal balance-of-plant requirements compared to conventional fuel cells, and environmentally friendly operation. These make the technology very attractive as portable power sources and waste-to-energy converters. The principal problem facing the technology is the low power densities compared to other conventional portable power sources such as batteries and traditional fuel cells. In this work we examined the yeast catalyzed microbial fuel cell and developed methods to increase the power density from such fuel cells. A combination of cyclic voltammetry and optical absorption measurements were used to establish significant adsorption of electron mediators by the microbes. Mediator adsorption was demonstrated to be an important limitation in achieving high power densities in yeast-catalyzed microbial fuel cells. Specifically, the power densities are low for the length of time mediator adsorption continues to occur. Once the mediator adsorption stops, the power densities increase. Rotating disk chronoamperometry was used to extract reaction rate information, and a simple kinetic expression was developed for the current observed in the anodic half-cell. Since the rate expression showed that the current was directly related to microbe concentration close to the electrode, methods to increase cell mass attached to the anode was investigated. Electrically biased electrodes were demonstrated to develop biofilm-like layers of the Baker's yeast with a high concentration of cells directly connected to the electrode. The increased cell mass did increase the power density 2 times compared to a non biofilm fuel cell, but the power density

  19. Recent advances in osmium-catalyzed hydrogenation and dehydrogenation reactions.

    Science.gov (United States)

    Chelucci, Giorgio; Baldino, Salvatore; Baratta, Walter

    2015-02-17

    CONSPECTUS: A current issue in metal-catalyzed reactions is the search for highly efficient transition-metal complexes affording high productivity and selectivity in a variety of processes. Moreover, there is also a great interest in multitasking catalysts that are able to efficiently promote different organic transformations by careful switching of the reaction parameters, such as temperature, solvent, and cocatalyst. In this context, osmium complexes have shown the ability to catalyze efficiently different types of reactions involving hydrogen, proving at the same time high thermal stability and simple synthesis. In the catalytic reduction of C═X (X = O, N) bonds by both hydrogenation (HY) and transfer hydrogenation (TH) reactions, the most interest has been focused on homogeneous systems based on rhodium, iridium, and in particular ruthenium catalysts, which have proved to catalyze chemo- and stereoselective hydrogenations with remarkable efficiency. By contrast, osmium catalysts have received much less attention because they are considered less active on account of their slower ligand exchange kinetics. Thus, this area remained almost neglected until recent studies refuted these prejudices. The aim of this Account is to highlight the impressive developments achieved over the past few years by our and other groups on the design of new classes of osmium complexes and their applications in homogeneous catalytic reactions involving the hydrogenation of carbon-oxygen and carbon-nitrogen bonds by both HY and TH reactions as well as in alcohol deydrogenation (DHY) reactions. The work described in this Account demonstrates that osmium complexes are emerging as powerful catalysts for asymmetric and non-asymmetric syntheses, showing a remarkably high catalytic activity in HY and TH reactions of ketones, aldehydes, imines, and esters as well in DHY reactions of alcohols. Thus, for instance, the introduction of ligands with an NH function, possibly in combination with a

  20. Preparation of 15N-labeled L-alanine by coupling the alanine dehydrogenase and alcohol dehydrogenase reactions

    International Nuclear Information System (INIS)

    A simple enzymatic procedure for the preparation of L-[15N]alanine, one of the metabolically most active amino acids in all types of cells, is reported. The procedure is based on the coupling of two reactions, one catalyzed by bacterial alanine dehydrogenase, the second catalyzed by yeast alcohol dehydrogenase. An impediment in the use of this procedure could be the high cost of commercial AlaDH. However, the enzyme is widespread in the Bacillus species and partially purified samples, adequate preparative purposes, could be obtained relatively easily by chromatography on blue-Sepharose. (Auth.)

  1. Escherichia coli DnaE Polymerase Couples Pyrophosphatase Activity to DNA Replication.

    Directory of Open Access Journals (Sweden)

    Fabio Lapenta

    Full Text Available DNA Polymerases generate pyrophosphate every time they catalyze a step of DNA elongation. This elongation reaction is generally believed as thermodynamically favoured by the hydrolysis of pyrophosphate, catalyzed by inorganic pyrophosphatases. However, the specific action of inorganic pyrophosphatases coupled to DNA replication in vivo was never demonstrated. Here we show that the Polymerase-Histidinol-Phosphatase (PHP domain of Escherichia coli DNA Polymerase III α subunit features pyrophosphatase activity. We also show that this activity is inhibited by fluoride, as commonly observed for inorganic pyrophosphatases, and we identified 3 amino acids of the PHP active site. Remarkably, E. coli cells expressing variants of these catalytic residues of α subunit feature aberrant phenotypes, poor viability, and are subject to high mutation frequencies. Our findings indicate that DNA Polymerases can couple DNA elongation and pyrophosphate hydrolysis, providing a mechanism for the control of DNA extension rate, and suggest a promising target for novel antibiotics.

  2. Catalytic conjunctive cross-coupling enabled by metal-induced metallate rearrangement.

    Science.gov (United States)

    Zhang, Liang; Lovinger, Gabriel J; Edelstein, Emma K; Szymaniak, Adam A; Chierchia, Matteo P; Morken, James P

    2016-01-01

    Transition metal catalysis plays a central role in contemporary organic synthesis. Considering the tremendously broad array of transition metal-catalyzed transformations, it is remarkable that the underlying elementary reaction steps are relatively few in number. Here, we describe an alternative to the organometallic transmetallation step that is common in many metal-catalyzed reactions, such as Suzuki-Miyaura coupling. Specifically, we demonstrate that vinyl boronic ester ate complexes, prepared by combining organoboronates and organolithium reagents, engage in palladium-induced metallate rearrangement wherein 1,2-migration of an alkyl or aryl group from boron to the vinyl α-carbon occurs concomitantly with C-Pd σ-bond formation. This elementary reaction enables a powerful cross-coupling reaction in which a chiral Pd catalyst merges three simple starting materials-an organolithium, an organoboronic ester, and an organotriflate-into chiral organoboronic esters with high enantioselectivity. PMID:26721996

  3. The glycosyltransferase involved in thurandacin biosynthesis catalyzes both O- and S-glycosylation

    OpenAIRE

    Wang, Huan; Oman, Trent J.; Zhang, Ran; Garcia De Gonzalo, Chantal V.; Zhang, Qi; van der Donk, Wilfred A.

    2013-01-01

    The S-glycosyltransferase SunS is a recently discovered enzyme that selectively catalyzes the conjugation of carbohydrates to the cysteine thiol of proteins. This study reports the discovery of a second S-glycosyltransferase, ThuS, and shows that ThuS catalyzes both S-glycosylation of the thiol of cysteine and O-glycosylation of the hydroxyl group of serine in peptide substrates. ThuS-catalyzed S-glycosylation is more efficient than O-glycosylation and the enzyme demonstrates high tolerance w...

  4. Electromagnetic clutches and couplings

    CERN Document Server

    Vorob'Yeva, T M; Fry, D W; Higinbotham, W

    2013-01-01

    Electromagnetic Clutches and Couplings contains a detailed description of U.S.S.R. electromagnetic friction clutches, magnetic couplings, and magnetic particle couplings. This book is divided into four chapters. The first chapter discusses the design and construction of magnetic (solenoid-operated) couplings, which are very quick-acting devices and used in low power high-speed servo-systems. Chapter 2 describes the possible fields of application, design, construction, and utilization of magnetic particle couplings. The aspects of construction, design, and utilization of induction clutches (sli

  5. Catalytic Chemo- and Regioselective Coupling of 1,3-Dicarbonyls with N-Heterocyclic Nucleophiles.

    Science.gov (United States)

    Kenny, Miles; Kitson, Daniel J; Franckevičius, Vilius

    2016-06-17

    The development of a decarboxylative palladium-catalyzed coupling of 1,3-dicarbonyl compounds with indole, pyrrole, imidazole, and pyrazole nucleophiles via an allylic linker under neutral conditions is disclosed. This process enables the installation of an all-carbon quaternary center and new C-C and C-N bonds in a single operation. Despite the weakly acidic nature of N-heterocycles, the reactions proceed with good efficiency and complete regio- and chemoselectivity. PMID:27211875

  6. Selective Functionalization of Independently Addressed Microelectrodes by Electrochemical Activation and Deactivation of a Coupling Catalyst

    OpenAIRE

    Devaraj, Neal. K.; Dinolfo, Peter H.; Chidsey, Christopher E. D.; Collman, James P.

    2006-01-01

    We demonstrate selective functionalization of independently addressed microelectrodes by electrochemical activation and deactivation of a coupling catalyst. 1,2,3-Triazole formation between terminal acetylenes and organic azides is efficiently catalyzed by copper(I) complexes (a Sharpless “click” reaction) while the oxidized copper (II) complexes are inactive. By electrochemically activating or deactivating the catalyst by switching its redox state, we demonstrate control over triazole format...

  7. Enantioselective Cross-Coupling of meso-Epoxides with Aryl Halides

    OpenAIRE

    Zhao, Yang; Weix, Daniel J.

    2015-01-01

    The first enantioselective cross-electrophile coupling of aryl bromides with meso-epoxides to form trans-β-arylcycloalkanols is presented. The reaction is catalyzed by a combination of (bpy)NiCl2 and a chiral titanocene under reducing conditions. Yields range from 57 to 99% with 78–95% enantiomeric excess. The 30 examples include a variety of functional groups (ether, ester, ketone, nitrile, ketal, trifluoromethyl, sulfonamide, sulfonate ester), both aryl and vinyl halides, and five- to seven...

  8. Acetylcholinesterase-catalyzed acetate - water oxygen exchange studied by 13C-NMR

    International Nuclear Information System (INIS)

    The kinetics of the oxygen exchange reaction between [l-13C,18O2]acetate and H216O catalyzed by homogeneous acetyl-cholinesterase from the electric eel, Electrophorus electricus, was studied using the 18O-isotope-induced shift on 13C-nuclear magnetic resonance spectra. Pseudo-first-order rate constants for the exchange reactions were determined at pH values from 4.5 to 8. The exchange reaction exhibits a maximum at pH 5.8. The apparent catalytic rate constant for the exchange reaction is 102 to 104 times smaller than that for the deacylation of the acetyl-enzyme intermediate over the pH range tested. Oxygen exchange occurs by a random sequential pathway rather than by multiple (coupled) exchange. The inhibition of acetylcholinesterase by sodium acetate showed a sigmoidal dependence on pH, with K/sub i/ increasing 2.5 orders of magnitude over the pH range. Protonation of an active site residue having an apparent pKa of 6.8 is associated with an increase in acetate binding. Deacylation also exhibits a sigmoidal dependence on [H+]. The experimental data fits titration curves with inflection points at 5.0 +/- 0.3 and 6.7 +/-0.1. Results support the role of histidine in acetylation of the active site serine, but the conjugate base of another active site residue with a pKa of 5.0 appears necessary for maximal catalytic activity in both the deacylation and exchange reactions

  9. MOLYBDENUM CATALYZED ACID PEROXIDE BLEACHING OF EUCALYPTUS KRAFT PULP

    Directory of Open Access Journals (Sweden)

    Marcos S. Rabelo

    2008-08-01

    Full Text Available Molybdenum catalyzed peroxide bleaching (PMo Stage consists of pulp treatment with hydrogen peroxide under acidic conditions in the presence of a molybdenum catalyst. Molybdenum is applied in catalytic doses (50-200 mg/kg pulp and may originate from various sources, including (NH46Mo7O24.4H2O, Na2MoO4.2H2O, siliconmolybdate, etc. This work is aimed at optimizing the PMo stage and evaluating its industrial application in the OAZDP sequence. Optimum PMo stage conditions for bleaching eucalyptus pulp were 90 ºC, pH 3.5, 2 h, 0.1 kg/adt Mo and 5 kg/adt H2O2. The PMo stage was more efficient to remove pulp hexenuronic acids than lignin. Its efficiency decreased with increasing pH in the range of 1.5-5.5, while it increased with increasing temperature and peroxide and molybdenum doses. The application of the PMo stage as replacement for the A-stage of the AZDP sequence significantly decreased chlorine dioxide demand. The PMo stage caused a decrease of 20-30% in the generation of organically bound chlorine. The quality parameters of the pulp produced during the PMo stage mill trial were comparable to those obtained with the reference A-stage.

  10. Enzyme-catalyzed Sequential Reduction of Carbon Dioxide to Formaldehyde☆

    Institute of Scientific and Technical Information of China (English)

    Wenfang Liu; Yanhui Hou; Benxiang Hou; Zhiping Zhao

    2014-01-01

    It has been reported that enzymatic-catalyzed reduction of CO2 is feasible. Most of literature focuses on the con-version of CO2 to methanol. Herein we put emphasis on the sequential conversion of CO2 to formaldehyde and its single reactions. It appears that CO2 pressure plays a critical role and higher pressure is greatly helpful to form more HCOOH as well as HCHO. The reverse reaction became severe in the reduction of CO2 to formaldehyde after 10 h, decreasing HCHO production. Increasing the mass ratio of formate dehydrogenase to formaldehyde dehydrogenase could promote the sequential reaction. At concentrations of nicotinamide adenine dinucleotide lower than 100 mmol·L−1, the reduction of CO2 was accelerated by increasing cofactor concentration. The opti-mum pH value and concentration of phosphate buffer were determined as 6.0 and 0.05 mol·L−1, respectively, for the overall reaction. It seems that thermodynamic factor such as pH is restrictive to the sequential reaction due to distinct divergence in appropriate pH range between its single reactions.

  11. Production of chemoenzymatic catalyzed monoepoxide biolubricant: optimization and physicochemical characteristics.

    Science.gov (United States)

    Salimon, Jumat; Salih, Nadia; Abdullah, Bashar Mudhaffar

    2012-01-01

    Linoleic acid (LA) is converted to per-carboxylic acid catalyzed by an immobilized lipase from Candida antarctica (Novozym 435). This per-carboxylic acid is only intermediate and epoxidized itself in good yields and almost without consecutive reactions. Monoepoxide linoleic acid 9(12)-10(13)-monoepoxy 12(9)-octadecanoic acid (MEOA) was optimized using D-optimal design. At optimum conditions, higher yield% (82.14) and medium oxirane oxygen content (OOC) (4.91%) of MEOA were predicted at 15 μL of H(2)O(2), 120 mg of Novozym 435, and 7 h of reaction time. In order to develop better-quality biolubricants, pour point (PP), flash point (FP), viscosity index (VI), and oxidative stability (OT) were determined for LA and MEOA. The results showed that MEOA exhibited good low-temperature behavior with PP of -41(°)C. FP of MEOA increased to 128(°)C comparing with 115(°)C of LA. In a similar fashion, VI for LA was 224 generally several hundred centistokes (cSt) more viscous than MEOA 130.8. The ability of a substance to resist oxidative degradation is another important property for biolubricants. Therefore, LA and MEOA were screened to measure their OT which was observed at 189 and 168(°)C, respectively. PMID:22346338

  12. Feasibility of an antiproton catalyzed fission fragment rocket

    Science.gov (United States)

    Hidinger, David S.

    1992-03-01

    The purpose of this project was to investigate the feasibility of an antiproton catalyzed fission fragment rocket (FFR). The FFR is characterized by the extraction of fission fragments from the fuel, and the utilization of their kinetic energy for thrust generation. A significant drawback to previous FFR designs was the required critical nuclear pile as the fission fragment source. The author examined the possibility of replacing the critical pile with a sub-critical pile driven by antiprotons. Recent experiments have revealed that antiprotons stimulate highly energetic fissions in 238U, with a neutron multiplicity of 13.7 neutrons per fissions. This interaction was used as a throttled neutron source. The pile consisted of layers of fissile coated fibers which are designed to allow fission fragments to escape them, where the fragments collide with a fluid. The heated fluid is then ejected from the rocket to provide thrust. The calculations performed indicate that each antiproton injected into the pile can stimulate 8 or more fissions while maintaining a neutron multiplication of less than 0.4. Based on the results, the specific design presented was inadequate. Despite this, the concept of using the antiproton-U interaction as a source of thrust warrants further study.

  13. Isothermal Kinetics of Catalyzed Air Oxidation of Diesel Soot

    Directory of Open Access Journals (Sweden)

    R. Prasad

    2011-01-01

    Full Text Available To comply with the stringent emission regulations on soot, diesel vehicles manufacturers more and more commonly use diesel particulate filters (DPF. These systems need to be regenerated periodically by burning soot that has been accumulated during the loading of the DPF. Design of the DPF requires rate of soot oxidation. This paper describes the kinetics of catalytic oxidation of diesel soot with air under isothermal conditions. Kinetics data were collected in a specially designed mini-semi-batch reactor. Under the high air flow rate assuming pseudo first order reaction the activation energy of soot oxidation was found to be, Ea = 160 kJ/ mol. ©2010 BCREC UNDIP. All rights reserved(Received: 14th June 2010, Revised: 18th July 2010, Accepted: 9th August 2010[How to Cite: R. Prasad, V.R. Bella. (2010. Isothermal Kinetics of Catalyzed Air Oxidation of Diesel Soot. Bulletin of Chemical Reaction Engineering and Catalysis, 5(2: 95-101. doi:10.9767/bcrec.5.2.796.95-101][DOI:http://dx.doi.org/10.9767/bcrec.5.2.796.95-101 || or local:  http://ejournal.undip.ac.id/index.php/bcrec/article/view/796]Cited by in: ACS 1 |

  14. Cobalt-Catalyzed Vinylation of Organozinc Reagents with Aldehydes

    Institute of Scientific and Technical Information of China (English)

    WANG; JinXian

    2001-01-01

    Transtion metal catalyzed vinylation of organic halides are known to be a very convenient method for forming carbon-carbon bonds at unsubstituted vinylic position. The versatility of stilbenes is well known because of its various biological active components, the variety of its reactions in organic syntheses, and its ability to function as a bonding partner for metals in complexes.  Many methods have been described for the synthesis of stilbenes. The reduction, dehydrogenation, and elimination reactions leading to stilbenes without formation of new carbon-carbon bonds are known to be a very convenient methods. Synthetically more important are the dimerization reactions: oxidative or eleminative dimerization of a suitable methylarene often constitutes the method of choice for the preparation of a symmetric stilbene. Meerwein arylation and Heck reaction are prominent examples for the synthesis of stilbenes from arenes and styrenes. Moreover, condensation reactions of a nucleophilic with an electrophilic arylmethyl compound include Knoevenagel type reactions and the very general Wittig and Wittig-Horner reactions are also known methods.  ……

  15. Oxidation of limonene catalyzed by Metal(Salen complexes

    Directory of Open Access Journals (Sweden)

    L. F. Lima

    2006-03-01

    Full Text Available The compound R-(+limonene is available and cheap than its oxidized products. Consequently, the selective oxidation of R(+limonene has attracted attention as a promising process for the production of compounds with a higher market value, such as cis/trans-1,2-limoneneoxide, cis/trans-carveol and/or carvone. One of the these processes, described in the recent literature, is submission of R-(+limonene to an oxidation reaction catalyzed by neutral or cationic Metal(Salen complexes, in the presence of effective terminal oxidants such as NaOCl or PhIO. These reactions are commonly carried out in organic solvents (dichromethane, ethyl acetate, acetonitrile or acetone. Thus, the main objective of the present work was to study the effect of several factors (type of oxidant, catalyst, solvent and time on reaction selectivity for the high-priced compounds referred to above. For this purposes, experimental statistical multivariate analysis was used in conjunction with a complete experimental design. From the results it was observed that for the three targeted products (1,2-limoneneoxide, carveol or carvone some factors, including the nature of the terminal oxidant and the catalyst, were significant for product selectivity (with a confidence level of 95%. Therefore, this statistical analysis proved to be suitable for choosing of the best reaction conditions for a specific desired product.

  16. Production of Chemoenzymatic Catalyzed Monoepoxide Biolubricant: Optimization and Physicochemical Characteristics

    Directory of Open Access Journals (Sweden)

    Jumat Salimon

    2012-01-01

    Full Text Available Linoleic acid (LA is converted to per-carboxylic acid catalyzed by an immobilized lipase from Candida antarctica (Novozym 435. This per-carboxylic acid is only intermediate and epoxidized itself in good yields and almost without consecutive reactions. Monoepoxide linoleic acid 9(12-10(13-monoepoxy 12(9-octadecanoic acid (MEOA was optimized using D-optimal design. At optimum conditions, higher yield% (82.14 and medium oxirane oxygen content (OOC (4.91% of MEOA were predicted at 15 μL of H2O2, 120 mg of Novozym 435, and 7 h of reaction time. In order to develop better-quality biolubricants, pour point (PP, flash point (FP, viscosity index (VI, and oxidative stability (OT were determined for LA and MEOA. The results showed that MEOA exhibited good low-temperature behavior with PP of −41°C. FP of MEOA increased to 128°C comparing with 115°C of LA. In a similar fashion, VI for LA was 224 generally several hundred centistokes (cSt more viscous than MEOA 130.8. The ability of a substance to resist oxidative degradation is another important property for biolubricants. Therefore, LA and MEOA were screened to measure their OT which was observed at 189 and 168°C, respectively.

  17. Base-catalyzed depolymerization of lignin : separation of monomers

    Energy Technology Data Exchange (ETDEWEB)

    Vigneault, A. [Sherbrooke Univ., PQ (Canada). Dept. of Chemical Engineering; Johnson, D.K. [National Renewable Energy Laboratory, Golden, CO (United States); Chornet, E. [Sherbrooke Univ., PQ (Canada). Dept. of Chemical Engineering; National Renewable Energy Laboratory, Golden, CO (United States)

    2007-12-15

    Biofuels produced from residual lignocellulosic biomass range from ethanol to biodiesel. The use of lignin for the production of alternate biofuels and green chemicals has been studied with particular emphasis on the structure of lignin and its oxyaromatic nature. In an effort to fractionate lignocellulosic biomass and valorize specific constitutive fractions, the authors developed a strategy for the separation of 12 added value monomers produced during the hydrolytic base catalyzed depolymerization (BCD) of a Steam Exploded Aspen Lignin. The separation strategy was similar to vanillin purification to obtain pure monomers, but combining more steps after the lignin depolymerization such as acidification, batch liquid-liquid-extraction (LLE), followed by vacuum distillation, liquid chromatography (LC) and crystallization. The purpose was to develop basic data for an industrial size process flow diagram, and to evaluate both the monomer losses during the separation and the energy requirements. Experimentally testing of LLE, vacuum distillation and flash LC in the laboratory showed that batch vacuum distillation produced up to 4 fractions. Process simulation revealed that a series of 4 vacuum distillation columns could produce 5 distinct monomer streams, of which 3 require further chromatography and crystallization operations for purification. 22 refs., 4 tabs., 8 figs.

  18. Alkylation of Benzene with Propylene Catalyzed by Ionic Liquids

    Institute of Scientific and Technical Information of China (English)

    Sun Xuewen; Zhao Suoqi

    2006-01-01

    The alkylation of benzene with propylene catalyzed by ionic liquids to obtain cumene was investigated. Propylene conversion and cumene selectivity under mild reaction conditions were improved greatly after the ionic liquid was modified with HCl. Under the conditions of 20 oC, 0.1MPa, 5 min of reaction time, and a molar ratio of benzene to propylene of 10:1, propylene conversion increased from 83.6% to 100%, and cumene selectivity increased from 90.86% to 98.47%. In addition, it was found that the reaction could be carried out in two different stages so as to obtain a better result. At the first stage, the key reaction was alkylation and a higher propylene conversion was obtained at a lower temperature;At the second stage, the key reaction was transalkylation and a higher temperature was used to improve cumene selectivity. The reaction temperature, pressure and the amount of catalyst used in this work were lower than those used in traditional alkylation processes.

  19. Interesterification of rapeseed oil catalyzed by tin octoate

    International Nuclear Information System (INIS)

    The interesterification of rapeseed oil was performed for the first time by using tin octoate as Lewis acid homogeneous catalysts and methyl or ethyl acetate as acyl acceptors in a batch reactor, within the temperature range 393–483 K. The yields in fatty acid ethyl esters (FAEE) and triacetin (TA) after 20 h of reaction time increased from 8% and 2%–to 61% and 22%, respectively, when the reaction temperature increased from 423 to 483 K. An optimum value of 40 for the acyl acceptor to oil molar ratio was found to be necessary to match good fatty acid alkyl ester yields with high enough reaction rate. The rate of generation of esters was significantly higher when methyl acetate was used as acyl acceptor instead of its ethyl homologue. The collected results suggest that tin octoate can be used as effective catalyst for the interesterification of rapeseed oil with methyl or ethyl acetate being highly soluble in the reaction system, less expensive than enzymes and allowing the operator to work under milder conditions than supercritical interesterification processes. - Highlights: • We study the interesterification of rapeseed oil catalyzed by tin(II) octoate. • Tin(II) octoate is an effective homogeneous catalyst at 483 K. • The acyl acceptor to oil molar ratio must be optimized. • Higher rate of reaction is obtained with methyl acetate as acyl acceptor

  20. On Transition Metal Catalyzed Reduction of N-nitrosodimethlamine

    CERN Document Server

    Zhou, Jun; Tian, Junhua; Zhao, Zhun

    2014-01-01

    This report provides a critical review on "Metal-Catalyzed Reduction of N-Nitrosodimethylamine with Hydrogen in Water", by Davie et al. N-nitrosodimethlamine (NDMA) is a contaminant in drinking and ground water which is difficult to remove by conventional physical methods, such as air stripping. Based on the reported robust capability of metal based powder shaped catalysts in hydrogen reduction, several monometallic and bimetallic catalyst are studied in this paper on the reduction of NDMA with hydrogen. Two kinds of kinetics, metal weight normalized and surface area normalized, are compared between each catalyst in terms of pseudo-first order reaction rate. Palladium, copper enhanced palladium and nickel are found to be very efficient in NDMA reduction, with half-lives on the order of hours per 10 mg/l catalyst metal. Preliminary LC-MS data and carbon balance showed no intermediates. Finally, a simple hydrogen and NMDA surface activated reaction mechanism is proposed by the author for palladium and nickel.