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

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. Co( ii )/spiroBox-catalyzed Mukaiyama-Mannich reactions of enol silyl ethers with cyclic N -sulfonyl ketimino esters were examined and showed excellent yields and enantioselectivity values.