Epoxide Rearrangement III. Isomerization of 1-Methylcyclohexene Oxide over TiO2–ZrO2, NiSO4 and FeSO4

The reaction of 1-methylcyclohexene oxide at 108 °C was found to give predominantly 2-methylcyclohexanone (III) over FeSO4, but predominantly allyl alcohols (VI) over TiO2–ZrO2 of various compositions. NiSO4 gave the same amount of both products, III and VI. The selectivities over FeSO4 and NiSO4 were not much varied with calcination temperatures from 150 °C to 700 °C, while the catalytic activities were higher with NiSO4 calcined at low temperature and with FeSO4 calcined at high temperature. FeSO4 and NiSO4 gave the preferential formation of an allyl alcohol with exo-double bond, 2-methylene cyclohexanol (VIa), while TiO2–ZrO2 formed predominantly an allyl alcohol with endo-double bond, 2-methyl-2-cyclohexene-1-ol (VIb). Both the acidity and basicity of TiO2–ZrO2 were observed to increase by mixing each oxide and to correlate with the catalytic activity. The allyl alcohol formation was explained by an acid-base bifunctional mechanism.