Generation of Oxazolidine-2,4-diones Bearing Sulfur-Substituted Quaternary Carbon Atoms by Oxothiolation/Cyclization of Ynamides

A novel method for metal‐free oxothiolation of ynamides to construct oxazolidine‐2,4‐diones bearing sulfur‐substituted quaternary carbon atoms has been developed. It represents a rare C−O bond cleavage of ynamides, as well as a facile and tandem approach for the formation of C−O, C−S, and C−Cl bonds. This redox‐neutral protocol can be applied to the synthesis of multisubstituted oxazolidine‐2,4‐diones with good chemoselectivity and good yields of isolated products under mild conditions. No cat required: A new metal‐free oxothiolation/cyclization of ynamides has been developed for the synthesis of multisubstituted oxazolidine‐2,4‐diones bearing sulfur‐substituted quaternary carbon atoms (see scheme). In addition, through the use of suitable chiral auxiliaries or chiral counteranions, this approach has been applied to the stereoselective synthesis of oxazolidine‐2,4‐diones.