Asymmetric Synthesis of Trisubstituted Tetrahydrothiophenes Bearing a Quaternary Stereocenter via Double Michael Reaction Involving Dynamic Kinetic Resolution

The stereoselective synthesis of highly functionalized tetrahydrothiophenes bearing three contiguous stereocenters, one of them quaternary, can be achieved by reacting <i>trans</i>-α-cyano-α,β-unsaturated ketones and <i>trans</i>-<i>tert</i>-butyl 4-mercapto-2-butenoate in the presence of a readily available amine thiourea. The products are obtained in high yield, good diastereoselectivity, and excellent enantioselectivity. The overall formation of tetrahydrothiophenes occurs via a cascade double Michael reaction involving a highly efficient process of dynamic kinetic resolution.