Unexpected Ring Opening During the Imination of Camphor‐Type Bicyclic Ketones

A new ring opening reaction was found while attempting to isolate the imines from ortho‐heteroatom substituted anilines and camphor‐like bicyclic ketones. The benzoazoles containing a cyclopentanemethyl group at position 2 of the heterocycle were isolated instead of the expected imines. The detailed study of the transformation, including EPR experiments, revealed the most probable radical mechanism. The proposed reaction pathways were confirmed by quantum chemical calculations. The dichotomy of 1–2 and 2–3 bonds cleavage is discussed together with the evaluation of the stereochemical outcome of the reactions. The benzoazoles obtained via the new reaction are of particular interest for the medicinal chemistry. New condensation reaction of camphor‐like ketones with o‐substituted anilines leading to formation of 2‐substituted benzoazoles is reported. A new reaction proceeds via ring opening of the bicyclic core. Quantum chemical calculations and EPR spectroscopy study suggest that imine radicals are key‐intermediates responsible for this unusual process.