Vanadium Catalyst in Micelles: Toward a Greener Aerobic Oxidative Cleavage of Vicinal Diols in Water

Thecatalytic aerobic oxidative cleavage of vicinal diolscan be achieved in water using a vanadium aminotriphenolate complexincorporated in a recyclable micellar medium. Aqueousmicellar media offer an alternative to organicsolventsfor the development of safe and environmentally benign synthesis.A vanadium aminotriphenolate complex, known to be an effective catalystfor the aerobic oxidative C-C cleavage of vicinal diols inorganic solvents, was incorporated in zwitterionic dodecyl phosphocholine(DPC) and in mixed TPGS-750-M:DPC micelles. It efficiently performedaffording the corresponding carbonyl derivatives with no overoxidation,with catalyst loading down to 0.2 mol % and reaching TONs up to 500.The mixed micelles, which combine the enhanced stability conferredby zwitterionic DPC and the exceptional extraction properties of non-ionicTPGS-750-M, could be recycled and full conversion achieved upon reloadingwith catalyst and substrate. The study of the correlation betweenthe reactivity of different substrates and their local concentrationin the micellar core, derived from DOSY experiments, highlights that,while lipophilicity is important, the ease with which the substratecan access the catalyst, and therefore the location of the catalystin the micellar phase, must also be considered when trying to rationalizereactivity in micelles.