Synthesis of 1,2-Fused/Disubstituted Benzimidazoles and Benzimidazolium Salts by I 2 -Mediated sp 3 C-H Amination.

An intramolecular sp 3 C-H amination reaction of aniline derivatives has been established. This reaction employs molecular iodine (I 2 ) under transition-metal-free conditions and produces 1,2-fused or 1,2-disubstituted benzimidazoles. This operationally simple synthetic process works well with N -substituted aniline substrates, forming novel benzimidazolium frameworks. Under the optimal reaction conditions, a broad variety of 1,2-fused/disubstituted benzimidazoles and benzimidazolium salts, including several bioactive compounds, were synthesized from readily accessible precursors in an efficient and scalable fashion.