Cinchona alkaloid-based phosphoramide catalyzed highly enantioselective Michael addition of unprotected 3-substituted oxindoles to nitroolefins

Abstract

A newly developed cinchonidine-derived phosphoramide 6b, simple and easily available, was identified as a powerful catalyst for the highly enantioselective Michael addition of both unprotected 3-aryl and 3-alkyloxindoles to β-substituted nitroalkenes to furnish the C3 quaternary stereogenic carbon center with an adjacent tertiary stereocenter in up to 21 : 1 diastereoselectivity and up to 99% enantioselectivity.