Biphasic Selective Oxidation of Cyclohexene with Dilute Aqueous Hydrogen Peroxide Using Phase Transfer Catalysts

Hydrogen peroxide (H2O2) can be produced electrochemically as a replacement for conventional anthraquinone oxidation routes. From a sustainability perspective, it would be best to use it in chemical applications without further purification or added cosolvents. Here, cyclohexene oxidation is carried out with dilute (0.08–0.25 M) aqueous H2O2 containing sulfate salts as a probe of the direct use of electrochemically produced oxidants. As catalysts, tungsten and molybdenum salts were combined with ammonium and imidazolium phase transfer agents. A mixture of [CH3(n-C8H17)3N][H2PO4] and [Et3NH][H2PO4] with Na2WO4 resulted in 95% overall yield of cyclohexene oxidation products─cyclohexene oxide (80%) and cyclohexene-1,2-diol (15%)─using a solution of 0.25 M H2O2 and 0.5 M K2SO4 in pH 5 water, with no added cosolvent. Results were validated with authentic electrochemically produced H2O2, demonstrating the practical applicability of this approach.