Intramolecular Fe(II)-Catalyzed N−O or N−N Bond Formation from Aryl Azides

Iron(II) bromide catalyzes the transformation of aryl and vinyl azides with ketone or methyl oxime substituents into 2,1-benzisoxazoles, indazoles, or pyrazoles through the formation of an N-O or N-N bond. This transformation tolerates a variety of different functional groups to facilitate access to a range of benzisoxazoles or indazoles. The unreactivity of the Z-methyloxime indicates that N-heterocycle formation occurs through a nucleophilic attack of the ketone or oxime onto an activated planar iron azide complex.