Iodine-Mediated Aryl C−H Amination for the Synthesis of Benzimidazoles and Pyrido[1,2-a]benzimidazoles

An intramolecular aryl C−H amination reaction has been achieved using molecular iodine as the sole oxidant for the synthesis of benzimidazole derivatives. The required substrates were readily prepared by addition or coupling of arylamines with the corresponding nitriles or aryl iodides. Iodine-mediated oxidative cyclization of these substrates in the presence of potassium carbonate (K 2 CO 3 ) as base afforded the corresponding products in moderate to good yields. The transition metal-free protocol presented here is insensitive to air and operationally simple. This versatile and eco-friendly synthetic methodology is broadly applicable to a variety of N -aryl-substituted amidines and pyridin-2-amines, and provides direct access to both 1 H -benzo[ d ]imidazole and pyrido[1,2- a ]benzimidazole derivatives from the corresponding precursors.