Photoisomerization of protonated cyclohex-2-enones

Protonated 4,4-dimethylcyclohex-2-enone, 1H, has been shown to isomerize on irradiation in FSO 3 H at −85 °C to give protonated 6,6-dimethylbicyclo[3.1.0]hexan-2-one, 5H, and protonated 3-isopropylcyclopent-2-enone, 4H. The protonated bicyclic ketone 5H was found to be both thermally and photochemically labile, in both instances rearranging to 4H. The first order rate constant for the thermal isomerization of 5H to 4H at −60 °C was 1.73 × 10 −4 …