Lipophilic N-Hydroxyphthalimide Catalysts for the Aerobic Oxidation of Cumene: Towards Solvent-Free Conditions and Back

A new class of lipophilic N-hydroxyphthalimide (NHPI) catalysts designed for the aerobic oxidation of cumene in solvent-free conditions was synthesized and tested. The specific strategy proposed for the introduction of lipophilic tails on the NHPI moiety leads to lipophilic catalysts thatâ while completely preserving the activity of the precursorâ allow the catalytic oxidation to be conducted in neat cumene, for the first time. The corresponding cumyl hydroperoxide is obtained in good yields (28â 52 %) and with high selectivity (95â 97 %), under mild conditions. Importantly, the presence of a polar solvent is no longer required to guarantee complete solubilization of the catalyst. On the other hand, the oxidation conducted in neat cumene reveals the unexpected necessity of using small amounts of acetonitrile to fully promote the hydrogen atom transfer process and prevent the catalyst from detrimental hydrogen-bond (HB) driven aggregation.