Highly enantioselective Mannich reactions of imines with tert-butyl acetoacetate catalyzed by squaramide organocatalyst

摘要

Highly enantioselective Mannich reactions of imines bearing a benzothiazole moiety with tert-butyl acetoacetate, catalyzed by a cinchona-based squaramide organocatalyst have been developed. The corresponding benzothiazole b-keto ester derivatives were obtained in high yields (up to 99%) and with excellent enantioselectivities (up to 98% ee).