Catalytic Epoxidation of Olefins with t-Butyl Hydroperoxide in the Presence of Polymer-supported Vanadium(V) and Molybdenum(VI) Complexes

Oxovanadium(V) and oxomolybdenum(VI) ions have been incorporated into cross-linked polystyrene resins functionalized with iminodiacetic acid or diethylenetriamine derivatives. The polymer complexes have been used as catalysts in the epoxidation of olefins with t-butyl hydroperoxide. Vanadium(V) complexes promote epoxidation of allylic alcohols in a highly regioselective manner, e.g., 2,3-epoxide has been preferentially obtained in 98% selectivity from (E)-geraniol at 80 °C. The catalytic activity of the vanadium(V) complexes is generally higher than that of the molybdenum(VI) complexes in the epoxidation of allylic alcohols whereas an opposed trend holds for the epoxidation of cyclohexene. Life time of catalysts have been examined by repeated use of the complexes in the epoxidation of (E)-geraniol at 80 °C in benzene. Approximately 15–25% of vanadium has been leaked out of the polymer beads on five time recycles leading to the decrease in the yield of 2,3-epoxide from initial value of 98% to 95–93%. Neither appreciable loss of metal nor reduction of catalytic activity has been observed in the molybdenum complex systems over five runs.