Novel synthesis of 3-hydroxy-2,3,4,5-tetrahydro-1-benzo-oxepins by cyclization of 2-(o-hydroxyphenyl)alkyl ketones with dimethyloxosulphonium methylide

Abstract

Reaction of dimethyloxosulphonium methylide with 2-(o-hydroxyphenyl)alkyl ketones (I) in Me₂SO or tetrahydrofuran (THF) gives the 3-hydroxy-2,3,4,5-tetrahydro-1-benzo-oxepins (VI a–e) in high yields; the corresponding 4,5-dihydro- and 2,5-dihydro-1-benzo-oxe-pins, (VIII) and (IX), respectively, are obtained from (VIc) by acid treatment or by acetylation and pyrolysis.