Enantioselective catalysis of the Henry reaction by a chiral macrocyclic ytterbium complex in aqueous media
作者:Shashi U. Pandya、Rachel S. Dickins、David Parker
DOI:10.1039/b712470h
日期:——
A chiral macrocyclic ytterbium cationic complex catalyses the nitro-aldol reaction between α-ketocarboxylates and nitromethane under ambient aqueous conditions, leading to the formation of for example, methyl-2-hydroxy-2-methyl-3-nitropropanoate in 96% yield and 59% enantiomeric purity. Monitoring of the paramagnetically shifted intermediate Yb species by 1H NMR allows several different species on the catalytic cycle to be identified and is consistent with the intermediacy of stereoisomeric chelated pyruvates of differing reactivity towards the nucleophile, as well as product inhibition of turnover.
一种手性大环镱阳离子配合物在常温水溶液条件下催化了 α-酮羧酸盐和硝基甲烷之间的硝基-醛醇反应,生成了例如 2-羟基-2-甲基-3-硝基丙酸甲酯,产率为 96%,对映体纯度为 59%。通过 1H NMR 监测顺磁偏移的中间体 Yb 物种,可以确定催化循环中的几种不同物种,并与对亲核体具有不同反应性的立体异构体螯合丙酮酸盐的中间体以及产物对周转的抑制作用相一致。