Conformational Effects in the Alkali-Metal Reduction of Diaryl Sulfides. 2. Evidence for Episulfide Intermediates

Article abstract of DOI:10.1021/jo00255a030

Alkali-metal reduction of a series of diaryl sulfides shows that, if both aryl moieties possess aromatic stabilization energies less than that of the phenyl group ( i.e., able to generate relatively more stable radical anions), the diaryl sulfide forms an episulfide intermediate via regiospecific coupling of the aryl moieties at the stage of a reactive intermediate.The formation of the episulfide intermediate explains why double carbon-sulfur bond cleavage and extrusion of sulfur is observed only in such diaryl sulfides and why there is preference for the formation ofsingle regioisomeric biaryl.