Ferrocenium Promoted Oxidation of Benzyl Amines to Imines Using Water as the Solvent and Air as the Oxidant

A ferrocenium promoted method for the chemoselective oxidation of benzylic amines to imines has been developed with yields varying from 53% to 93%. Use of 5 mol % ferrocenium hexafluorophosphate as a promoter was sufficient for this radical based oxidation reaction. Air was bubbled into the reaction mixture, which worked as the oxidant for this transformation. Most importantly, the reaction was carried out in pure aqueous medium at 65 °C. A 10 gram scale reaction with benzylamine was successfully carried out to show the practical applicability of this methodology.