Catalytic epoxidation of camphene using methyltrioxorhenium(VII) as catalyst

This work presents the epoxidation of camphene employing methyltrioxorhenium(VII) (MTO) as catalyst. The effect of different factors on the formation of camphene oxide with respect to high yield and selectivity was investigated. First, the ratio camphene:MTO:pyrazole:H₂O₂ was studied in dichloromethane as solvent in order to determine the optimal condition. Moreover, the influence of the Lewis base adduct (tert-butylpyridine, 4,4′-dimethyl-2,2′-bypridine, imidazole or pyrazole) was investigated. The effect of an aqueous oxidant, namely H₂O ₂ and a solid oxidant, namely urea hydrogen peroxide (UHP) was also examined. Finally, the solvent was varied from dichloromethane to chloroform, toluene and nitromethane. Based on the results the optimal conditions for the epoxidation of camphene using MTO as catalyst were determined. The molar ratio camphene:MTO:pyrazole:H₂O₂ of 100:0.5:10:110 in dichloromethane at room temperature leads after 3 h to 97% yield and 98% selectivity toward camphene oxide at 99% conversion.