Photochemical Synthesis of 1,2‐Substituted Benzimidazoles via Intramolecular Ortho‐Azido Anilines Cyclization

A new method for the synthesis of 1,2‐substituted benzimidazoles from 2‐azidoanilines has been developed. The reaction proceeds under 365 nm photoirradiation in DMSO among many other solvents in the absence of catalysts and any additives. Using the approach, 18 compounds were synthesized in yields ranging from 54% to 93%. For halogen‐containing substrates, 475 nm irradiation avoids side dehalogenation. The transformation mechanism that involves two photodependent stages was proposed.