Ring transformation of (4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitriles to 3-haloisothiazole-5-carbonitriles

Abstract

Ring transformation of readily prepared (4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitriles afford 3-haloisothiazole-5-carbonitriles in good to excellent yields. The transformation can be mediated using HBr (g), HCl (g) or BnEt₃NCl. Mechanisms for the transformations are discussed, together with rationalizations for the formation of side products. Furthermore, single crystal X-ray structures are provided for (Z)-2-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitrile and (E)-2-bromo-2-(4-chloro-5H-1,2,3-dithiazol-5-ylidene)acetonitrile confirming the stereochemistry of the exocyclic ethene bond.