Molecular Iodine-Promoted [3 + 2] Oxidative Cyclization for the Synthesis of Heteroarene-Fused [1,2,4] Thiadiazoles/Selenadiazoles

Two new classes of heteroarene-fused [1,2,4]­thiadiazole and [1,2,4]­selenadiazole are synthesized through the iodine-mediated [3 + 2] oxidative cyclization of 2-aminoheteroarenes and isothiocyanates/isoselenocyanates. This oxidative [3 + 2] annulation strategy is highly regiospecific to proceed a selective C–N bond formation at the endo-nitrogen of 2-aminoheteroarenes followed by an intramolecular oxidative N–S/N–Se bond formation. It is the first example of an I₂-mediated oxidative nitrogen–selenium (N–Se) bond formation.