Cyclopropanation and epoxidation of tricyclo[5.2.1.02,6]deca-2(6),8-dien-3-one

Cyclopropanation of tricyclo[5.2.1.02,6]deca-2(6),8-dien-3-one using dimethylsulfoxonium ylide gave a highly strained annulated cyclopropane in 68% yield with complete exo-face selectivity. Nucleophilic epoxidation gave a strained epoxide in 68% yield, again completely exo-face selective. Surprisingly, using methanol as the co-solvent in this epoxidation yielded a disubstituted tricyclodecenone in 85% yield instead of the epoxide. This result can be explained by a Payne-type rearrangement of the initially formed epoxide.