Transition-metal catalyst free C=N coupling with phenol/phenoxide: a green synthesis of a benzoxazole scaffold by an anodic oxidation reaction

By utilizing an anodic oxidative reaction and consuming 2.2 F mol(-1) of electricity, C=N coupling with phenol/phenoxide to obtain the five-membered N,O-heteroatom ring of a benzoxazole has been achieved at room temperature. Transition-metal catalysts, chemical oxidants, strong acids, reactive chemical reagents and refluxing are not required. Studies of the electrode, solvent, electrolyte and additive effects to promote the anodic cyclization are included. From the CV studies, the reaction mechanisms of the anodic cyclization are proposed.