Reactivity of vinyl sulphonic esters. Part IX. Cyclisation of aryloxyvinyl p-bromobenzenesulphonates to benzo[b]furans

Abstract

1,2-Diaryl-2-aryloxyvinyl p-bromobenzenesulphonates (7) have been prepared by reaction of 2-aryl-2-aryloxyacetophenone (6) with p-bromobenzenesulphonyl chloride in the presence of sodium hydride. Compounds (7) give upon reaction with BF₃ in dichloromethane 2,3-diarylbenzo[b]furans (8) and p-bromobenzenesulphonic acid. Evidence is presented that the β-oxygen, in contrast to the corresponding sulphur atom in analogous reactions of thiovinylsulphonates (1), does not participate at any significant extent in the reaction.