3-Mercaptopropionic acid-nitrile imine adducts. An unprecedented cyclization into 1,3,4-thiadiazol-2(3H)-ones and -2(3H)-thiones.

3-Mercaptopropionic acid-nitrile imine acyclic adducts (6a-c) undergo cyclocondensation with 1,1'-carbonyldiimidazole to afford the respective 1,3,4-thiadiazol-2-(3H)-ones (7a-c). Corresponding 1,3,4-thiadiazol-2(3H)-thiones (8a-c) were likewise produced from 6a-cand 1,1'-thiocarbonyldiimidazole, with consequent elimination of the propionate moiety. The constitution of these heterocyclic products follows from analytical and spectral data and is confirmed by single crystal X-ray structure determination for 7b.