Author: Christian Ebner
Publisher:
ISBN: 9783954040414
Category :
Languages : en
Pages : 241

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Author: Christian Ebner
Publisher: Cuvillier Verlag
ISBN: 3736940416
Category : Science
Languages : en
Pages : 262

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This work was dedicated to the development and evaluation of new chiral catalysts for asymmetric C-C and C-H bond forming reactions. In the first part of the thesis an ESI-MS screening method is described, which allows the determination of a chiral catalyst´s selectivity in the palladium catalyzed asymmetric allylic alkylation by testing its racemic form. The value of this new method was demonstrated when different new aryl-PHOX-type ligands, which are not easily accessible in their enantiopure form, were evaluated. In the second part new PHOX-type ligands were tested in the iridium-catalyzed asymmetric hydrogenation of different unsaturated compounds. Although low activities and selectivities were found in most cases, one ligand showed promising results in the hydrogenation of allylic alcohols and imines. Furthermore air- and moisture-stable secondary phosphine oxide (SPO) containing bidentate ligands were tested in the palladium-catalyzed asymmetric allylic alkylation reaction. SPO,N-ligands bearing a PHOX type backbone were inactive in this transformation as they tend to form inactive palladium-bis-ligand complexes. SPO,P ligands however, were able to promote the desired reaction in a highly selective fashion although only low activities were found. During this work as well a new organo-catalyst, based on the structure of 2,3-dihydrobenzo[1,4]oxazine, was developed which allows for the asymmetric organo-catalyzed transfer-hydrogenation of α,β-unsaturated aldehydes. This catalyst was able to reduce for the first time β, β-diaryl acrylaldehydes with very good activities and high enantioselectivities. Moreover an ESI-MS based mechanistic study on the tripeptide catalyzed conjugate addition reaction of aldehydes to nitroolefins was carried out. By this all reaction intermediates postulated for an enamine mechanism have been detected. Furthermore the attack of the enamine onto the nitroolefin was found to be the selectivity determining step in this process. The last part of this work aimed for the asymmetric α -allylation of carbonyl compounds by a tandem-catalysis approach. An intensive screening of both the organo-catalyst and the palladium-ligand led to reaction conditions which allowed for the selective mono-allylation of ketones in high yields. The formation of a quaternary center by α -allylation of α -branched aldehydes was also achieved. However, only low enantiomeric excesses were obtained in this transformation for the different catalyst systems tested.

Author:
Publisher: Elsevier
ISBN: 044323700X
Category : Science
Languages : en
Pages : 338

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Book Description
Enantioselective C-C Bond Forming Reactions: From Metal Complex-, Organo-, and Bio-catalyzed Perspectives, Volume 73 in the Advances in Catalysis series, highlights new advances in the field, with this new volume presenting interesting chapters on topics such as An introduction to Chirality, Metal-catalyzed stereoselective C-C-bond forming reactions, Enantioselective C-C bond forming reactions promoted by organocatalysts based on unnatural amino acid derivatives, Enantioselective C-C bond formation in complex multicatalytic system, Gold-based multicatalytic systems for enantioselective C-C Bond forming reactions, Novel enzymatic tools for C-C bond formation through the development of new-to-nature biocatalysis, and more. - Provides the authority and expertise of leading contributors from an international board of authors - Presents the latest release in Advances in Catalysis serials - Updated release includes the latest information in the field

Author: Menapara Tusharkumar
Publisher: Alibaba
ISBN: 9781805294801
Category : Medical
Languages : en
Pages : 0

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Book Description
The book "Asymmetric C-C Bond Formation with Chiral Catalysts" by Menapara Tusharkumar explores the fascinating field of asymmetric catalysis for carbon-carbon bond formation reactions. The book emphasizes on the use of chiral catalysts for the synthesis of enantiopure compounds that are critical for the development of new drugs, agrochemicals, and materials. The use of chiral catalysts offers high enantioselectivity and stereoselectivity, and therefore, provides an efficient way for the synthesis of organic compounds with desired stereochemistry. The book covers the design and synthesis of chiral catalysts, including ligands and transition metal complexes. The author discusses the chemical properties of chiral catalysts and their influence on the reaction mechanisms and stereoselectivity. The book also highlights the importance of molecular recognition in asymmetric catalysis and its application in various catalytic reactions. The book covers various types of asymmetric catalysis, including organocatalysis, metal-catalyzed reactions, and enzymatic catalysis. It discusses the advantages and limitations of each type of catalysis and provides examples of their applications in organic synthesis. The author also emphasizes the importance of green chemistry and sustainability in asymmetric catalysis. The book covers a range of topics related to asymmetric C-C bond formation, including diastereoselectivity, substrate specificity, kinetic resolution, and stereochemical control. The book also provides examples of the synthesis of natural products, alkene coupling, palladium-catalyzed cross-coupling reactions, oxidative coupling reactions, Diels-Alder reactions, and Michael addition reactions using chiral catalysts. Overall, "Asymmetric C-C Bond Formation with Chiral Catalysts" is an essential reference for organic chemists, catalysis researchers, and students who are interested in asymmetric catalysis, enantioselective synthesis, and stereochemistry. The book provides a comprehensive overview of the field, including recent advances and challenges, and offers practical guidance for the design and optimization of chiral catalysts for asymmetric C-C bond formation reactions.

Author: Sabine Berteina-Raboin
Publisher: MDPI
ISBN: 3039281380
Category : Technology & Engineering
Languages : en
Pages : 182

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In the last few decades, research on the elaboration by palladium-catalytic processes of C-C bonds or the activation of C–H bonds has increased considerably. Yet there is still room for much improvement in terms of selectivity, or enantioselectivity, via the development of new ligands or the study of the catalytic effect of other metals to carry out the same chemical transformations. In addition, the attention paid to environmentally friendly methods in terms of the quantities of catalysts, ligands, and solvents is currently indispensable. The Mizoroki-Heck reaction is one of these important catalytic methods which generates C-C bonds in organic synthesis and is also possible by C-H activation. This book, titled “Catalyzed Mizoroki-Heck Reaction or C-H activation” focuses on new advances in the formation of C-C bonds or new C-H activation methods. It contains original research papers and short reviews on the synthesis of biologically active compounds using these catalytic processes, the identification of new catalysts, of new conditions allowing selectivity or enantioselectivity, the activity and stability of catalyst under turnover conditions, and all improvements in catalytic processes.

Author: Souvagya Biswas
Publisher:
ISBN:
Category :
Languages : en
Pages :

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Book Description
Nature has established numerous methods for synthesis of complex molecules utilizing simple and abundant resources such as the use of CO2, H2O and N2 using sunlight as a source of energy. Even more impressive are the high chemo-, regio-, and stereoselectivites observed in these transformations with a wide variety of both prochiral and chiral substrates. However, methods for the enantioselective incorporation of feedstock materials such as CO, HCN, CO2 or simple alkenes into prochiral molecules are limited and remain an important challenge in the field. The hydrovinylation reaction (HV), where ethylene is added across a carbon-carbon double bond, has been known for nearly fifty years, starting with the works of Hata, Alderson and Wilke. During the past few years, through an approach that relied mostly on mechanistic insights and systematic examination of ligand effects, our group discovered a number of protocols for Ni(II)- and Co(II)-catalyzed enantioselective hydrovinylation (HV) reactions of vinylarenes, 1,3-dienes and strained olefins. While the Ni(II)-catalyzed hydrovinylation (HV) reaction is one of the most selective asymmetric catalyzed carbon-carbon bond forming reactions, its use has been limited to alkenes conjugated to an aromatic ring and strained alkenes. We recently found Co(II)-bisphosphine complexes show much improved regioselectivity with broader functional group compatibility in 1,3-dienes. By utilizing finely tuned catalysts derived from Co(II)-bisphosphine complexes and Me3Al or methylaluminoxane (MAO) acyclic (E) and (Z)-1,3-dienes were found to undergo efficient hydrovinylation giving mostly 1,4-hydrovinylation products in an atmosphere of ethylene. In order to expand the hydrovinylation chemistry, we turned our attention to one of the mostly widely used intermediates on organic chemistry, viz., silyl enol ethers. Trialkylsilyl enol ethers are exceptionally versatile intermediates often used as enolate surrogates for the synthesis of carbonyl compounds. Yet there are no reports of broadly applicable, catalytic methods for the synthesis of chiral silyl enol ethers carrying latent functionalities useful for synthetic operations beyond the many possible reactions of the enol ether moiety itself. The work presented herein reports a general procedure for highly catalytic (substrate : catalyst ratio up to 1000:1) and enantioselective (96% to 98% major enantiomer) synthesis of silyl enol ethers bearing a vinyl group at a chiral carbon at the beta-position. The reactions, run under ambient conditions, use trialkylsiloxy-1,3-dienes and ethylene (1 atmosphere) as precursors, and readily available (bis-phosphine)-cobalt(II) complexes as catalysts. Once we have established the HV reaction conditions of the siloxydienes, we turn our attention towards diastereoselective functionalization of the hydrovinylated products. Under optimized conditions, we are able to successfully utilize our 1,4-hydrovinylated products as reactive nucleophilic synthons for several electrophilic reactions keeping moderate to good diastereomeric ratios. The silyl enolates can be readily converted into novel enantiopure vinyl triflates, a class of highly versatile cross-coupling reagents, enabling the syntheses of other enantiomerically pure trisubstituted alkene intermediates not easily accessible by current methods.

Author: Kuiling Ding
Publisher: John Wiley & Sons
ISBN: 3527623027
Category : Science
Languages : en
Pages : 466

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In this most up-to-date handbook each chapter contains a general introduction, followed by the principles of the immobilization and, finally, applications. In this way, it covers the most important approaches currently employed for the heterogenization of chiral catalysts, including data tables, applications, reaction types and literature citations. For chemists in both academia and industry as well as those working in the fine chemical and pharmaceutical industry.

Author: Shengming Ma
Publisher: Springer Science & Business Media
ISBN: 3642194729
Category : Science
Languages : en
Pages : 368

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Book Description
Qi-Lin Zhou and Jian-Hua Xie: Chiral Spiro Catalysts.- Fuk Loi Lam, Fuk Yee Kwong and Albert S. C. Chan: Chiral Phosphorus Ligands with Interesting Properties and Practical Applications.- Jiang Pan, Hui-Lei Yu, Jian-He Xu, Guo-Qiang Lin: Advances in Biocatalysis: Enzymatic Reactions and Their Applications.- Mei-Xiang Wang: Enantioselective Biotransformations of Nitriles.- Man Kin Wong, Yiu Chung Yip and Dan Yang: Asymmetric Epoxidation Catalyzed by Chiral Ketones.- W. J. Liu, N. Li and L. Z. Gong: Asymmetric Organocatalysis.- Qing-Hua Fan and Kuiling Ding: Enantioselective Catalysis with Structurally Tunable Immobilized Catalysts.- Chang-Hua Ding, Xue-Long Hou: Transition Metal-Catalyzed Asymmetric Allylation.- Jian Zhou and Yong Tang: Enantioselective Reactions with Trisoxazolines.- Xiang-Ping Hu, Duo-Sheng Wang, Chang-Bin Yu, Yong-Gui Zhou, and Zhuo Zheng: Adventure in Asymmetric Hydrogenation: Synthesis of Chiral Phosphorus Ligands and Asymmetric Hydrogenation of Heteroaromtics.

Author: Vijaya Bhasker Gondi
Publisher:
ISBN:
Category : Asymmetric synthesis
Languages : en
Pages :

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Author: Stanley M. Roberts
Publisher: John Wiley & Sons
ISBN: 0470862009
Category : Science
Languages : en
Pages : 268

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Book Description
The chemist has a vast range of high-tech catalysts to use when working in fine chemical synthesis but the catalysts are generally hard to use and require both time, skill and experience to handle properly. The Catalysts for Fine Chemical Synthesis series contains tested and validated procedures which provide a unique range resources for chemists who work in organic chemistry. "... of great value to synthetic organic chemists..." (The Chemists, Summer 2003) Volume 3 in the series focuses on catalysts for carbon-carbon bond formation and presents practical and detailed protocols on how to use sophisticated catalysts by the "inventors" and "developers" who created them. The combination of protocols and review commentaries helps the reader to easily and quickly understand and use the new high-tech catalysts.