One-step arylthiolation of aromatic compounds by disulfide radical cations generated from oxidation of diaryl disulfides with aluminium chloride

Reactions of di(phenyl and 4-tolyl) disulfides 1a and 1b with PhX 3a-e (X=H, Me, Et, Ph and Cl) in the presence of AlCl3 at 25 degrees C give diaryl sulfides 4-6 by aromatic arylthiolation via the disulfide radical cations 2, along with thiophenols 7 formed in the incomplete reactions. Competitive intramolecular reactions of 2a also yield diphenyl sulfide 4a or/and thianthrene 8. However, the reactions of bis(4-chlorophenyl and 4-fluorophenyl) disulfides 1c and 1d selectively lead to the aromatic arylthiolation in high yields. The Hammett rho=-8.8 at 25 degrees C for the phenylthiolation in the reactions of 1a is more negative than that (rho=-7.0 at -30 degrees C) using SbCl5 instead of AlCl3, and the value rho=-8.0 for the arylthiolation using 1d is less negative than that using 1a. These and the other mechanistic aspects support the arylthiolations via 2.