Allenedicarboxylate as a Stereochemically Labile Electrophile for Chiral Organic Base-Catalyzed Stereoselective Michael Addition

A highly stereoselective Michael addition of α-amino acid-derived 2-benzyloxythiazol-5(4H)-ones to dimethyl allenedicarboxylate was developed by employing P-spiro chiral triaminoiminophosphorane bearing (S)-sec-butyl groups as a catalyst. Theoretical investigation of the transition-state models for the reaction and control experiments suggested the intervention of a dynamic kinetic resolution of the axially chiral allene acceptor. The synthetic utility of this method was demonstrated through the transformation of the stereochemically homogeneous Michael adduct to an α-vinylic α-amino acid derivative.