Synthesis of Bicyclic Isothiazoles through an Intramolecular Rhodium-Catalyzed Transannulation of Cyanothiadiazoles

An intramolecular rhodium-catalyzed
transannulation of readily
available cyanothiadiazoles containing an ester, amide, or ether as
a linker is described. It provides a wide range of bicyclic isothiazoles
in good to excellent yields together with the release of molecular
nitrogen. These results indicate that the carbon atom in the α-thiavinyl
carbene is nucleophilic and that the sulfur atom is electrophilic.