Abstract: Several o-alkoxybenzophenones and o-(benzy1oxy) benzophenones and- acetophenones photocyclize to 3-hydroxy-2, 3-dihydrobenzofurans. Quantum yields generally are quite high, except for o-(benzy1oxy) acetophenone. The o-ethoxy and o- benzyloxy ketones form two diastereomeric products, the Z isomer being highly preferred in hydrocarbon solvents, the E isomer being formed in comparable yield in methanol or with ...