Photolysis of 3-oxo-δ5(10)-steroids in alcoholic solvents and in the solid phase

Irradiation of the β, γ-unsaturated ketone 1a in alcoholic solvents afforded the 1,2 and 1,3-acyl shift products 2a and 3 respectively. The cyclobutanone 3 underwent further photochemistry incorporating a molecule of solvent and affording the ring expanded cyclic acetal 6. Solid phase irradiation of 1a yielded 2a and 3 but 1b was photostable.