Synthesis of Isothiazole via the Rhodium-Catalyzed Transannulation of 1,2,3-Thiadiazoles with Nitriles

A synthetic method for obtaining a wide variety of isothiazoles by the Rh-catalyzed transannulation of 1,2,3-thiadiazoles with alkyl, aryl, and heteroaryl nitriles, which proceeds via an α-thiavinyl Rh-carbenoid intermediate, was developed. The results suggest that during its reaction with nitriles, the α-thiavinyl carbene acts as an umpolung 1,3-dipole equivalent, in contrast to its behavior during its reaction with alkynes. The developed method was successfully employed to synthesize pentaoligomeric arylene compounds consisting of three benzene and two isothiazole rings.