Novel bifunctional l-prolinamide derivatives as highly efficient organocatalysts for asymmetric nitro-Michael reactions
作者:Dan Xu、Junliang Wang、Lijun Yan、Mingquan Yuan、Xiaotian Xie、Yongchao Wang
DOI:10.1016/j.tetasy.2016.08.019
日期:2016.12
A series of novel bifunctional L-prolinamide derivatives was synthesised, of which (S)-N-((S)-2-oxo-1-phenyl-2-(tritylamino)ethyl)pyrrolidine-2-carboxamide 6 was found to be the most effective catalyst in terms of both the yield and stereoselectivity for the nitro-Michael reaction of aldehydes to nitroalkenes. Under these optimized reaction conditions, 17 corresponding novel nitro-Michael addition adducts had high yields (up to 94%) and showed excellent diastereoselectivity (up to 99:1 dr) and enantioselectivity (up to 98 ee) under mild reaction conditions. (C) 2016 Elsevier Ltd. All rights reserved.
Enantioselective Organocatalytic Conjugate Addition of Aldehydes to Nitrodienes
The asymmetric organocatalyzed Michael addition of aldehydes to alpha,beta-gamma,delta-unsaturated nitro compounds has been accomplished using only 5 mol % of (S)-diphenylprolinol silyl ether and 2 equiv of aldehyde in a mixture of ethanol and water (5% v/v). The Michael adducts were obtained in good yields, diastereoselectivities up to 94/6, and ee's up to 99%. This process provides synthetically useful compounds which can easily lead to more complex molecules, as exemplified with substituted tetrahydropyran or cyclohexene.