Iodine(III)-Catalyzed Oxidative Cyclization of Aryl Amines to Construct Benzimidazoles

An I(III)-catalyzed oxidative cyclization reaction using Selectfluor as the oxidant was developed that converts ortho-substituted anilines to benzimidazoles is reported. The mild reaction requires as little as 0.5 mol % of iodobenzene tolerating electron-poor groups on the aniline portion. The size of the ring can be varied to access the pyrrole, azepine, and azocines scaffolds. Preliminary mechanistic investigations suggest that benzimidazole formation occurs via cationic reactive intermediates, and an intramolecular kinetic isotope effect of 1.98±0.01 was measured.