The Co(ii)/spiroBox-catalyzed enantioselective Mukaiyama-Mannich reaction for the synthesis of quaternary α-amino acid derivatives

Abstract

The Mukaiyama–Mannich reaction of enol silyl ether with cyclic N-sulfonyl ketimino ester catalyzed by a cobalt complex of a chiral spiroBox ligand was examined. Excellent yields (up to 99%) and ee values (up to 99%) were obtained with a broad scope of substrates. This catalytic system was shown to allow the facile synthesis of quaternary α-amino acid derivatives in high yields and with excellent enantioselectivities.