Homolytic aromatic substitution of heterocyclic compounds. Part V. The phenylation of benzo[b]thiophen and benzo[b]furan

Abstract

The homolytic phenylation of benzo[b]thiophen and benzo[b]furan has been carried out, with the thermal decomposition of N-nitrosoacetanilide as the source of phenyl radicals. The isomer ratios and the relative reactivities have been determined. Homolytic substitution in benzo[b]furan takes place almost exclusively in the heterocyclic ring, in contrast with benzo[b]thiophen, in which all the available positions show a comparable reactivity towards substitution by phenyl radicals.

The syntheses of a number of phenylbenzo[b]furans and phenylbenzo[b]thiophens are reported.