Novel efficient aromatic arylthiolation by disulfide radical cations generated by oxidation of diaryl disulfides

Abstract

The disulfide radical cation was generated by oxidation of diphenyl disulfide using H₂SO₄ in CF₃CO₂H or SbCl₅ in CH₂Cl₂, and allowed to react with benzene, toluene, ethylbenzene, chlorobenzene, anisole and alkyl phenyl sulfides to give efficiently para-substituted diphenyl sulfides along with a small amount of the ortho-isomers. The intermediacy of the radical cation in this aromatic phenylthiolation is consistent with the evidence derived from a Hammett plot with ρ = –7.0 (using SbCl₅ in CH₂Cl₂), from effects of oxidants, counter-anions and solvents and from electronic absorptions (540 and 650 nm). Using di-4-anisyl, di-4-tolyl and di-4-chlorophenyl disulfides instead of diphenyl disulfide, the aromatic arylthiolation similarly occurs via radical cations from their disulfides.