Squaramide-tertiary amine catalyzed asymmetric cascade sulfa-Michael/ Michael addition via dynamic kinetic resolution: Access to highly functionalized chromans with three contiguous stereocenters

摘要

An efficient asymmetric cascade sulfa-Michael/Michael addition reaction catalyzed by a chiral bifunctional squaramide-tertiary amine catalyst has been developed. This organocatalytic cascade reaction provides easy access to highly functionalized chromans with three contiguous stereocenters, including one quaternary center. In addition, a novel cascade sulfa Michael/retro-sulfa- Michael/sulfa-Michael/Michael reaction process, involving dynamic kinetic resolution, is described.