Epoxide Rearrangement II. Isomerization of 1-Methylcyclohexene Oxide over Solid Acids and Bases

The reaction of 1-methylcyclohexene oxide over solid acids and bases at 108 °C was found to give five main products, 2-methylcyclohexanone (III), 1-methylcyclohexanol (IV), 2-methyl-2-cyclohexene-1-one (V), 2-methyl-enecyclohexanol (VIa), and 2-methyl-2-cyclohexene-1-ol (VIb), with a small amount of 1-methylcyclohexene (I) and unidentified compound (II). The ketone (III) was formed predominantly over zeolite, SiO2–Al2O3, H2SO4/SiO2, AlCl3, and BBr3, while the allyl alcohol (VI) was given by Al2O3 and TiO2. HCl/SiO2 and solid H3PO4 calcined at 400–900°C gave both products, III and VI, in the same amounts, though the latter calcined at 200–300°C formed almost 100% ketone. Solid lithium perchlorate was surprisingly active for the formation of ketone, but other metal per chlorates and lithium salts were quite inactive. Alkaline earth metal oxides and NaOH/SiO2 were almost inactive. The catalytic activity and selectivity as well as the reaction path and mechanism are briefly discussed mainly in connection with acid-base property of solid catalysts.