PHOTOCYCLIZATION REACTIONS .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-l, 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.