Epoxidation of alpha-pinene catalyzed by methyltrioxorhenium(VII): Influence of additives, oxidants and solvents

The epoxidation of -pinene employing methyltrioxorhenium as catalyst is examined. The influence of mono- and bidentate Lewis basic additives (e.g. tbutylpyridine, 4,4-dimethyl-2,2-bipyridine, and Schiff-bases) is investigated. Additionally the impact of the oxidant (H 2O2 in water or urea-hydrogen peroxide (UHP)) on the catalytic performance is studied. The effect of the solvent is also examined in order to determine the optimal conditions for the epoxidation of -pinene. The best and straightforwardly applicable result is obtained when a ratio -pinene:MTO:tbutylpyridine:UHP of 200:1:40:600 is applied at 0 °C in nitromethane. In this case, -pinene oxide is formed with 95% yield after 3 h with a turnover frequency (TOF) of 610 h-1.