Highly selective route for producing unsymmetrically substituted monomers toward synthesis of conjugated polymers derived from poly(p-phenylene vinylene)

A new convenient route for producing unsymmetrically substituted sulfinyl m onomers of precursor polymers toward poly(p-phenylene vinylene) is describe d. Upon treating a symmetrical bissulfonium salt with a thiolate anion, an unexpected high selectivity for the monosubstituted thioethers (90%) is obt ained. Optimization of the reaction conditions showed that the stoichiometr y of the reactants in this reaction is important to ensure the high selecti vity and to prevent unwanted side reactions. Reaction of equimolar amounts of reagents at ambient temperature gave the best results. A mechanism consi stent with these results, supported by UV-vis experiments, is presented. Se lective oxidation of the thioethers yielded the sulfinyl monomers. By using this new route, it was possible to increase the overall yield by a factor of 2, as compared to the route previously used to obtain these compounds.