Construction of chiral quaternary carbon center via catalytic asymmetric aza-Henry reaction with α-substituted nitroacetates

Abstract

The catalytic enantioselective aza-Henry reaction of N-Boc aldimines 2 and 2-nitropropionic acid ethyl ester 3 in the mixed solvents of toluene–saturated brine (10 : 1) was catalyzed by cinchona quaternary ammonium salts to form a new quaternary carbon center. High yields (up to 90%), and excellent enantioselectivities (up to 99% ee) and diastereoselectivity ratio (up to 22 : 1) were successfully obtained with mild conditions.