Anodic oxidation of diphenyl disulfides for preparation of oligo(p-phenylene sulfide)s in acidic media

Diphenyl disulfides yield oligo(p-phenylene sulfides) by an anodic oxidation in dichloromethane solution in the presence of protonic acids as trifluoroacetic acid. The acid suppresses the nucleophilic reaction of the cationic active species and the electro-oligomerization of diphenyl disulfide proceeds through an electrophilic reaction of a cation formed anodic oxidation. The oxidation of diphenyl disulfide proceeds through a one-electron transfer and via phenylbis(phenylthio) sulfonium cation as an active species in this oligomerization, which was confirmed electrochemically. Upon adding benzoquinones and cerium acetylacetonate to the mixture, the oligomerization proceeds efficiently to give a high yield of the oligomer and can be carried out at a lower applied potential (1.7 to 0.8 V vs. Ag/AgCl).