Iron-Catalyzed 1,4-Phenyl Migration/Ring Expansion of α-Azido N-Phenyl Amides

Herein, we report a novel iron-catalyzed skeleton rearrangement of alkyl azides. Upon treatment with FeCl2 and N-heterocyclic carbene SIPr·HCl in the presence of H2O and Et3N, 2-azido-N,N-diphenylamides underwent 1,4-phenyl migration and ring expansion to give azepin-2-ones in good yield. The reaction proceeds via intramolecular nitrene cycloaddition followed by C-N cleavage, water addition, and electrocyclic ring opening.