Unique solvent effect on photochemistry of ortho-alkylphenacyl benzoates

Photolysis of 2,4,6-trialkylphenacyl benzoates gives not only the corresponding indanones and benzoic acid, but also the corresponding benzocyclobutenols (CBs), which are also detected in the photolysis of mono-alkylphenacyl benzoates for the first time. The product selectivity was heavily dependent upon solvents and o-alkyl group. H-bonding acceptor solvents strongly favor the formation of the CB. As the size of the o-alkyl group increases, the relative amount of the CB increases.