Asymmetric Michael addition reactions of aldehydes to β-nitrostyrenes catalyzed by (S)–N-(D-prolyl-L-prolyl)-1 -triflicamido-3 -phenylpropan-2-amine

Abstract

ABSTRACT In an attempt to improve the catalytic ability of (S)-N-(D-prolyl)-1-triflicamido-3-phenylpropan-2-amine, a catalyst previously reported by us for the asymmetric Michael addition of aldehydes to β-nitrostyrenes, 4 new molecules were designed and synthesized by increasing the distance between the triflicamide group and the secondary amino group in the catalyst. Under the optimized reaction conditions (S)-N-(D-prolyl-L-prolyl)-1-triflicamido-3-phenylpropan-2-amine exhibited high and improved catalytic activity and stereoselectivity at a lower catalyst loading (3 mol%). In the studies done with a large number of aldehydes and β-nitrostyrenes, the Michael adducts were obtained in high yields (up to 94%) and with excellent enantioselectivities (up to 98% ee) and with good to excellent diastereoselectivities (up to 98:2 dr).