On the stereochemistry of the Baker's Yeast-mediated reduction of regioisomeric unsaturated aldehydes: Examples of enantioselectivity switch promoted by substrate-engineering
摘要:
The Baker's Yeast (BY) reduction of (Z)-2-chloromethyl-3-arylacrylaldehydes was found to afford (R)-2-methyl-3-aryl-propanols showing high enantiomeric excess values. Deuterium incorporation experiments were performed, in order to investigate the mechanism of the bioreduction: the formation of the corresponding substituted 2-benzylacrylaldehydes. as intermediates to be effectively reduced by Baker's Yeast, was suggested. These intermediates were synthesized and submitted to BY reduction to afford the corresponding saturated (R)-alcohols, thus confirming the conclusions drawn from labelling experiments. The enantioselectivity of their bioreduction was found to be opposite with respect to that observed for the corresponding regioisomeric 2-methylcinnamaldehydes. The preparation of the two enantiomers of 2-methyl-3-aryl-propanols by fermentation of two regioisomers represents an interesting example of substrate-controlled enantioselective reaction. (C) 2012 Elsevier B.V. All rights reserved.
On the stereochemistry of the Baker's Yeast-mediated reduction of regioisomeric unsaturated aldehydes: Examples of enantioselectivity switch promoted by substrate-engineering
摘要:
The Baker's Yeast (BY) reduction of (Z)-2-chloromethyl-3-arylacrylaldehydes was found to afford (R)-2-methyl-3-aryl-propanols showing high enantiomeric excess values. Deuterium incorporation experiments were performed, in order to investigate the mechanism of the bioreduction: the formation of the corresponding substituted 2-benzylacrylaldehydes. as intermediates to be effectively reduced by Baker's Yeast, was suggested. These intermediates were synthesized and submitted to BY reduction to afford the corresponding saturated (R)-alcohols, thus confirming the conclusions drawn from labelling experiments. The enantioselectivity of their bioreduction was found to be opposite with respect to that observed for the corresponding regioisomeric 2-methylcinnamaldehydes. The preparation of the two enantiomers of 2-methyl-3-aryl-propanols by fermentation of two regioisomers represents an interesting example of substrate-controlled enantioselective reaction. (C) 2012 Elsevier B.V. All rights reserved.
Pd-Catalyzed Threefold Arylation of Baylis-Hillman Bromides and Acetates with Triarylbismuth Reagents
作者:Maddali L. N. Rao、Somnath Giri
DOI:10.1002/ejoc.201200543
日期:2012.8
alkyl 2-benzylacrylates and 2-benzylacrylonitriles were synthesized by means of atom-economic cross-couplings of Baylis–Hillmanbromides or acetates with BiAr3 under palladium-catalyzed conditions. These reactions, involving threefold aryl couplings using BiAr3 reagents with bromides and acetates, are fast and are completed in 1–2 h with high product yields.
Substrate-switched dual functionalization of alkenes: catalyst-free synthetic route for β-hydroxy and β-keto thioethers
作者:Satpal Singh Badsara、Pratibha Singh、Rakhee Choudhary、Rekha Bai、Mahesh C. Sharma
DOI:10.1039/c9nj02682g
日期:——
In this study, a substrate-controlled dual functionalization of alkenes under catalyst-free and solvent-free conditions is described. Alkenes possessing different electron-withdrawing groups, namely, ester and nitrile, reacted with a variety of thiols under air to provide β-hydroxy thioethers and β-keto thioethers, respectively, in good to excellent yields.