Direct Organocatalytic Asymmetric Aldol Reaction of α-Isothiocyanato Imides to α-Ketoesters under Low Ligand Loading: A Doubly Stereocontrolled Approach to Cyclic Thiocarbamates Bearing Chiral Quaternary Stereocenters

The first doubly stereocontrolled organocatalytic asymmetric aldol reaction of alpha-isothiocyanato imides with alpha-ketoesters by using rosin-derived tertiary amine-thiourea under low ligand loading to form cyclic thiocarbamates bearing quaternary stereogenic centers with high levels of enantio- and diastereoselectivity (up to 99% ee, and 97:3 dr) is presented. This reaction provides a convenient doubly stereocontrolled method to access synthetic useful multiply substituted cyclic thiocarbamates with high optical purity.