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The rearrangement of 2-benzylidenecyclohexanone oxide (I) to 2-phenylcycloheptane-1,3-dione (II) was carried out in the presence of a Lewis acid or a Brφnsted acid in various media-liquid sulfur dioxide, benzene, and ether. The only reaction product of I with a Brφnsted acid in these solvents was the rearranged compound, II. In addition to II, 2-(α-halobenzyl)-2-hydroxycyclohexanone, (III) or (IV), was also obtained in the reaction of I with a Lewis acid in solutions. Drastic solvent effects were observed on the rate and the distribution of products in this reaction; however, no solvent effect was observed when a Brφnsted acid, which could donate a proton to I, was used as the catalyst. From the variations in the concentrations of the reactant, the intermediate, and the product during the reaction course, the solvent effects upon the reaction pathways were discussed.

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