Reactivity of vinyl sulphonic esters. Part VIII. Evidence for sulphur participation in the cyclisation of 2-arylthio-1,2-diphenylvinyl p-bromobenzenesulphonates from carbon-14 labelling experiments

Abstract

2-Arylthio-1,2-diphenyl[1-¹⁴C]vinyl p-bromobenzenesulphonates were prepared and cyclised to 2,3-diphenyl-benzo[b]thiophen derivatives. Fragmentation of the cyclisation products by a controlled route showed that substantial equilibration of the two ethylenic carbon atoms had occurred. The results are taken as evidence of the formation of a sulphur-bridged species along the reaction path.