Organocatalyzed Asymmetric Reactions via Microwave Activation
摘要:
Organocatalyzed asymmetric microwave-assisted reactions are described. Significant rate enhancements and a decrease of catalyst loading via microwave activation have been observed, while maintaining good to high yields and selectivities compared to literature results.
4-Trifluoromethanesulfonamidyl prolinol tert-butyldiphenylsilyl ether as a highly efficient bifunctional organocatalyst for Michael addition of ketones and aldehydes to nitroolefins
作者:Chao Wang、Chun Yu、Changlu Liu、Yungui Peng
DOI:10.1016/j.tetlet.2009.02.211
日期:2009.5
4-Trifluoromethanesulfonamidyl prolinol tert-butyldiphenylsilyl ether bifunctionalorganocatalyst 3a is a highly efficient catalyst for the asymmetric Michaeladdition reactions of ketones and aldehydes to nitrostyrenes, leading to syn-selective adducts with excellent yields (>99%), high diastereoselectivities (up to 99:1 dr) and excellent enantioselectivities (up to 99% ee). Control experiments suggested that the
Enantioselective conjugate addition of ketones to nitroalkenes catalyzed by pyrrolidine-sulfamides
作者:Jinjia Wang、Jinhua Lao、Quansheng Du、Shaozhen Nie、Zhipeng Hu、Ming Yan
DOI:10.1002/chir.21987
日期:2012.3
A series of chiral pyrrolidine‐sulfamides were prepared and examined as the catalysts for conjugateaddition of ketones to nitroalkenes. Benzoic acid was identified as the most efficient additives for the transformation. Excellent enantioselectivities, diastereoselectivities, and yields were achieved for the reaction of cyclohexanone with β‐aryl nitroethylenes under solvent free conditions. β‐Isopropyl
The direct Michaeladdition of aldehydes and ketones to nitroolefins, catalyzed by N-i-Pr-2,2′-bipyrrolidine, is described. The desired 1,4-adducts are obtained in excellent yields with enantioselectivities up to 95% ee and dr up to 95 : 5 of the syn aldehydeaddition product. An unexpected inversion of diastereoselectivity was observed for the addition of α-hydroxy ketones to β-arylnitroolefins with
(S)-Binam-L-prolinamide as organocatalyst for the enantioselective conjugate addition of α-alkoxyketones to β-nitrostyrene derivatives
作者:Miguel Yus、Gabriela Guillena、Carmen Nájera、Santiago F. Viózquez
DOI:10.3998/ark.5550190.0012.313
日期:——
This research was supported by the Ministerio de Ciencia e Innovacion (Projects CTQ2007-62771/BQU, CTQ2007-65218/BQU and Consolider Ingenio 2010 CSD2007-00006), the Generalitat Valenciana (Project PROMETEO/2009/039, FEDER) and the University of Alicante (UA).
[GRAPHIC]The regio-, stereo-, and enantioselective direct Michael addition of alpha-hydroxyketones to beta-aryinitroolef ins catalyzed by N-/Pr-2,2'-bipyrrolidine is described. The formation of an internal hydrogen bond between the OH group of alpha-hydoxyacetone and the tertiary nitrogen of the catalyst leads to the formation of a rigid cis enamine intermediate that explains the inversion of the expected diastereoselectivity and the very high ee's.