Photoisomerization of dichlorocarbene adducts of 2,4-cyclohexadienones

Irradiation of the nπ* band of the dichlorocyclopropyl enones $\text{1}$ and $\text{7}$ resulted in ring expansion and 1,2-chlorine migration to give $\text{2}$ and $\text{8}$ respectively, whereas the dihydrogen analog $\text{11}$ gave the vinylcyclopropane-cyclopentene rearrangement product $\text{12}$.