A Selenourea-Thiourea Bronsted Acid Catalyst Facilitates Asymmetric Conjugate Additions of Amines to α,β-Unsaturated Esters

beta-Amino esters are obtained with high levels of enantioselectivity via the conjugate addition of cyclic amines to unactivated alpha,beta-unsaturated esters. A related strategy enables the kinetic resolution of racemic cyclic 2-arylamines, using benzyl acrylate as the resolving agent. Reactions are facilitated by an unprecedented selenourea-thiourea organocatalyst. As elucidated by DFT calculations and C-13 kinetic isotope effect studies, the ratelimiting and enantiodetermining step of the reaction is the protonation of a zwitterionic intermediate by the catalyst. This represents a rare case in which a thiourea compound functions as an asymmetric Bronsted acid catalyst.