Abstract: Oxidation of cyclohexene catalyzed by vanadium pentoxide was carried out under mild conditions with aqueous hydrogen peroxide as the oxidant. The effects of the solvent type, solvent amount, catalyst amount, and reaction temperature on the reaction were investigated. The allylic oxidation of cyclohexene was the dominate reaction, and cyclohexene-2-one was obtained as the major product. The solvent type significantly affects the catalyst activity and the selectivity for cyclohexene-2-one. Particularly acetone is an optimal choice for improving the conversion of cyclohexene. Under the conditions of V(acetone)∶V(cyclohexene)=4, m(V2O5)∶m(cyclohexene)=1∶40, n(H2O2)∶n(cyclohexene)=3, 20 ℃, and 24 h, the conversion of cyclohexene reached up to 60% and the selectivity for cyclohexene-2-one was 85%. It is proposed that the oxidation of cyclohexene catalyzed by vanadium pentoxide involves a reversible V5+/V4+ species redox cycle using acetone as the oxygen transfer agent.

Key words: vanadium pentoxide, cyclohexene, hydrogen peroxide, allylic oxidation, cyclohexene-2-one