Enantioselective Protonation in the Aza-Michael Reaction Using a Combination of Chiral Pd-µ-Hydroxo Complex with an Amine Salt

Abstract

A highly enantioselective protonation of enolate intermediates in aza-Michael reaction was achieved by using the combination of a bifunctional chiral Pd-µ-hydroxo complex with aromatic amine salts. The reaction proceeded smoothly to give the desired β-amino carbonyl compounds bearing a stereogenic carbon center at the α-position in good yield with excellent enantioselectivity (up to 97% ee). Although reactions with salts of electron-deficient amines were slow, the introduction of free amine as an additive promoted the reaction to a synthetically useful level.