Iodine(III)-mediated bicyclic diazenium salt formation

The hypervalent iodine(III) reagent PhI(OTf)2 has been shown to be an effective oxidant for the conversion of linear aryl-hydrazones bearing a pendant alkene into bicyclic diazenium salts. This oxidative cyclization presumably occurs by the iodine(III) mediated formation of a 1-aza-2-azoniaallene salt intermediate that undergoes a subsequent intramolecular 1,3-dipolar cycloaddition with the pendant alkene.