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.