Asymmetric Michael addition reactions catalyzed by a novel upper-rim functionalized calix[4]squaramide organocatalyst
作者:Ke Yang、Zhiyan Ma、Hong-Xiao Tong、Xiao-Qiang Sun、Xiao-Yu Hu、Zheng-Yi Li
DOI:10.1016/j.cclet.2020.02.057
日期:2020.12
Abstract A novel upper-rim functionalizedcalix[4]squaramide organocatalyst bearing bis-squaramide and cyclohexanediamine scaffolds was designed and prepared to catalyse a serial of asymmetric Michael addition of 1,3-dicarbonyl compounds to α,β-unsaturated carbonyl compounds in high yields (up to 99 %) and good to excellent enantiomeric excesses (up to 99% ee). The comparative experiments indicated
Azetidine-derived bifunctional organocatalysts for Michael reactions
作者:Laurence Menguy、François Couty
DOI:10.1016/j.tetasy.2010.08.003
日期:2010.10
2-Cyano azetidines, easily accessible from beta-amino alcohols, are precursors of stereodefined homochiral azetidinic or pyrrolidinic 1,2-diamines. A small library of these original diamines was screened as precatalysts for the enantioselective addition of 1,3-dicarbonyl compounds onto beta-nitro styrenes. An azetidinic diamine derived from (-)-ephedrine and derivatized as a thiourea was found to catalyze the conjugate addition of acetylacetone with good levels of enantioselectivities (up to 84% ee). Interestingly, the absolute configuration of the Michael adduct depends on the nature of the 1,3 dicarbonyl nucleophile (diethyl malonate or acetylacetone), which is indicative of a different mechanism involved in the reaction of these two nucleophiles. (C) 2010 Elsevier Ltd. All rights reserved.