Photocyclization reactions. Part 1. Synthesis of dihydrobenzofuranols using photocyclization of 2‐alkoxybenzaldehydes, 2′‐alkoxyacetophenones, 2‐formylphenoxyacetic acids and 2‐acetylphenoxyacetic acids

Photocyclization reactions were carried out on 2‐alkoxybenzaldehydes 1a‐f, 2′‐alkoxyacetophenones 2a‐h, 2‐formylphenoxyacetic acids 1i‐l and 2‐acetylphenoxyacetic acids 2i‐m. Irradiation of 1a‐f and 2a‐h in acetonitrile gave the corresponding dihydrobenzofuranols 3, 5 and dihydroisobenzofuranols 4, 6. Using carboxylic acids 1i‐1, 2i‐m as starting materials, decarboxylation occurred immediately to give the corresponding ethers 1a‐d, 2a‐e. Further irradiation of the solution afforded dihydrobenzofuranols 3, 5 and dihydroisobenzofuranols 4, 6. Substituent effects on photocyclization and reaction pathways are discussed.