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Catalytic Asymmetric Hydrogenation (catalytic + asymmetric_hydrogenation)
Selected AbstractsA General Approach to the Synthesis of ,2 -Amino Acid Derivatives via Highly Efficient Catalytic Asymmetric Hydrogenation of ,-AminomethylacrylatesADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 9 2010Yujuan Guo Abstract A new strategy was developed for the synthesis of a valuable class of ,-aminomethylacrylates via the Baylis,Hillman reaction of different aldehydes with methyl acrylate followed by acetylation of the resulting allylic alcohols and SN2,-type amination of the allylic acetates. Asymmetric hydrogenation of these diverse olefinic precursors using rhodium(Et-Duphos) catalysts provided the corresponding ,2 -amino acid derivatives with excellent enantioselectivities and exceedingly high reactivities (up to >99.5% ee and S/C=10,000). The first hydrogenation of (Z)-configurated substrates was studied for the synthesis of ,2 -amino acid derivatives. The high influence of the substrate geometry and steric hindrance on the reactivity and enantioselectivity was also disclosed for this reaction. This protocol provides a highly practical, facile and scalable method for the preparation of optically pure ,2 -amino acids and their derivatives under mild reaction conditions. [source] Convenient General Asymmetric Synthesis of Roche Ester Derivatives through Catalytic Asymmetric Hydrogenation: Steric and Electronic Effects of LigandsADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 16 2008Cyrielle Pautigny Abstract An efficient and concise asymmetric hydrogenation of acrylate esters promoted by the cationic ruthenium monohydride complex [Ru(H)(,6 -cot)SYNPHOS]+BF4, is reported. A full investigation of the effects of catalyst precursors, solvents, temperature, hydrogen pressure, substrates as well as steric and electronic properties of ligands was carried out. The corresponding valuable Roche ester derivatives were obtained in good to excellent isolated yields and high enantioselectivities under mild conditions. The robustness and practicability of this highly enantioselective hydrogenation was demonstrated by the synthesis of the 3-hydroxy-2-methylpropanoic acid tert -butyl ester on a multigram scale, resulting in excellent yield and ee up to 94%. [source] ChemInform Abstract: Efficient Synthesis of Chiral ,-Arylisopropylamines by Using Catalytic Asymmetric Hydrogenation.CHEMINFORM, Issue 21 2009Jian Chen Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Catalytic Asymmetric Hydrogenation of Aldehydes.CHEMINFORM, Issue 36 2007Xiaoguang Li Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF. [source] Preparation of Synthetically Useful Chiral Building Blocks , 5-Alkylated ,-Lactones via Catalytic Asymmetric Hydrogenation of 4-Oxo Esters.CHEMINFORM, Issue 14 2003G. Juszkiewicz Abstract For Abstract see ChemInform Abstract in Full Text. [source] Synthesis and spectroscopic studies of 5-arylidene-3-substituted tetramic acids as possible substrates for catalytic asymmetric hydrogenationJOURNAL OF HETEROCYCLIC CHEMISTRY, Issue 5 2001Giorgos Athanasellis A new series of 5-arylidene-3-substituted tetramic acids 6,19 have been synthesized by a condensation reaction of 3-butanoyl tetramic acid 3, 3-ethoxycarbonyl tetramic acid 4 and 3 -acetyl tetramic acid 5 with a variety of substituted benzaldehydes. The structures of the isolated compounds 6,19 have been elucidated using FT-IR, 1H and 13C-NMR spectroscopy, FAB-MS spectroscopy as well as elemental analyses. [source] Natural alkaloids and synthetic relatives as chiral templates of the Orito's reactionCHIRALITY, Issue 1 2010Emília Tálas Abstract The enantioselective hydrogenation of methyl or ethyl pyruvate over cinchona-platinum catalyst system (Orito's reaction) is one of the most intensively studied heterogeneous catalytic asymmetric hydrogenation reactions. Studies aiming at systematic changes of the chiral template have played a crucial role in creating hypotheses for the mechanism of Orito's reaction. It is very important to clarify which structural unit of the alkaloid takes part in the enantiodifferentiation, and learn about the role of the different structural units of chiral templates. In this article, we made an attempt to describe the behavior of natural alkaloids, their synthetic derivatives, and analogues as chiral templates in the heterogeneous catalytic asymmetric hydrogenation of activated ketones. Chirality, 2010. © 2009 Wiley-Liss, Inc. [source] | ||||||||||