Asymmetric Michael Addition of Malonate Anions to Prochiral Acceptors Catalyzed by l-Proline Rubidium Salt
摘要:
L-Proline rubidium salt catalyzes the asymmetric Michael addition of malonate anions to prochiral enones and enals. This method can be applied to a wide range of substrates to give adducts with a predictable absolute configuration: (S)-adducts from (E)-enones/enals and (R)-adducts from cyclic (Z)-enones. Both the secondary amine moiety and the carboxylate moiety are critical for the catalytic activity and asymmetric induction. Varying the countercation also affects the reaction course. High enantiomeric excesses were attained when di(tert-butyl) malonate was added to (E)-enones in the presence of CsF. The stereochemistry of the Michael reaction indicates that asymmetric induction takes place via enantioface discrimination involving the acceptor alpha-carbon atom rather than the beta-carbon atom.
Asymmetric Michael addition reactions using a chiral La–Na aminodiolate catalyst
作者:N Prabagaran、G Sundararajan
DOI:10.1016/s0957-4166(02)00240-9
日期:2002.6
(R,R)-(+)-2-[Benzyl-(2-hydroxy-2-phenylethyl)amino]-1-phenylethanol 1 is used as a chiral ligand in the synthesis of an optically active lanthanum-sodium amino diol complex LS-1. This heterobimetallic catalyst is quite effective its an asymmetric catalyst for various Michael addition reactions, H-1 NMR Study indicates the co-ordination of enone to the central lanthanum atom in LS-1. The reaction conditions were optimized and the adducts were obtained in high yield with moderate to high enantiomeric excess under extremely mild conditions. (C) 2002 Elsevier Science Ltd. All rights reserved.