Acid catalysed rearrangements of 8,8-dimethyl-2,3-homotropone

The Brønsted and Lewis acid catalysed rearrangements of 8,8-dimethyl-2,3-homotropone, 2, have been examined. Four major products have been identified: 2-isopropyltropone, 6; isobutyrophenone, 7; 2-isobutenylphenol, 8; and 8,8-dimethylbicyclo[3.2.1]-octa-3,6-dien-2-one, 5. The relative amounts of these products differ very markedly as the acid medium changes. Mechanisms are proposed to account for these reactions.