Epoxidation of cyclohexene catalyzed by transition-metal substituted α-titanium arsenate using tert-butyl hydroperoxide as an oxidant

Abstract

Epoxidation of cyclohexene, using transition-metal substituted α-titanium arsenate {α-TiMAs, where MCu(II), Co(II), Mn(II), Fe(III), Cr(III) and Ru(III)} as a catalyst and dry tert-butyl hydroperoxide as an oxidant, was studied. In the epoxidation reaction, cyclohexene was oxidized to cyclohexene oxide, cyclohexenol and cyclohexenone. It was found that the reactivity of the epoxidation reaction decreased in the order α-TiRuAs>α-TiMnAs>α-TiFeAs>α-TiCrAs>α-TiCoAs>α-TiCuAs. A maximum selectivity for epoxidation of cyclohexene (89.89%) was observed for α-TiRuAs/dryTBHP system after 4 h of reaction when concentrations of the catalyst and the substrate were 0.20 and 20 mmol, respectively. The competitive epoxidation of cyclic olefins were studied and the reactivity-order in the relative rates of epoxidation of cyclic olefins was found to decrease in the order norbornene>cyclooctene>cyclohexene>cyclopentene. The mechanism for epoxidation of cyclohexene catalyzed by α-TiMAs/dryTBHP system is proposed.