Carbonsulfur (CS) bond formation is one of the important synthetic routes in organic chemistry. Among sulfur sources for CS bond formation, organosulfur cations (RS + ) and their synthetic equivalents are unique reagents. These cationic sulfur species are easily prepared as compared with the oxonium analogues, because of their low ionization potentials. This review describes various synthetic methods for CS bond formation, mainly focusing on electrophilic reactions, addition to olefins, and substitution to aromatic rings. A breakthrough has been anticipated for RS + electrophiles, based on their versatile utility in aromatic polymer synthesis.

Oxidative polymerization of diphenyl disulfide under molten conditions at moderately elevated temperatures gave poly(1,4-phenylene sulfide) (PPS), using a vanadyl complex–strong acid catalyst with oxygen as the ultimate oxidant. Origin of the selectivity of the sulfonium electrophile for the formation of the 1,4-thiophenylene chain, characterized by the presence of a disulfide bond at the chain end, was determined by the behavior of polymerization and structural analysis of the product together with a computational calculation, which revealed a unique chain growth-type polycondensation process.

The first VO(salen) catalyzed oxidative polymerization of PhSSPh and bromanil-assisted acceleration of the polymerization were reported.