Efficient synthesis of 1,2,4‐dithiazolidine‐3,5‐diones (dithiasuccinoyl‐amines) and observations on formation of 1,2,4‐thiadiazolidine‐3,5‐diones by related chemistry

An efficient synthesis of 1,2,4‐dithiazolidine‐3,5‐diones (1) from chlorocarbonylsulfenyl chloride (3) plus O‐dimethylaminoethyl‐N‐alkyl or aryl thiocarbamates (4) has been worked out. In this synthesis, 1,2,4‐thiadiazolidine‐3,5‐diones (5) have been shown to arise as low‐level by‐products, and experiments were conducted to elucidate the mechanism of the side reaction. N,N′‐Dimethyl‐1,2,4‐thiadiazolidine‐3,5‐dione (5a) was prepared in one step from N,N′‐dimethylurea plus 3, or from 4a plus one equivalent of sulfuryl chloride. A general route to 5 involved reaction of equimolar amounts of isocyanates (6), isothiocyanates (7) and sulfuryl chloride followed by hydrolysis of intermediate 9. Heterocycles reported have been characterized by nmr, ir, uv, ms, and hplc.