Quinoxaline-Based Cyclo(oligophenylenes).

A series of fully conjugated quinoxaline-based oligophenylene macrocycles is synthesized by Ni(0)-mediated Yamamoto-type diaryl homocoupling of (fluorinated) 2,3-bis(4'-bromophenyl)quinoxaline precursors. Cyclotrimers and cyclotetramers are obtained as the dominant reaction products. The cyclooligomers are fully characterized, including single-crystal X-ray structures, and their optoelectronic properties are analyzed with respect to possible applications in host-guest chemistry and organic electronics.

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 monomers of precursor polymers toward poly(p-phenylene vinylene) is described. Upon treating a symmetrical bissulfonium salt with a thiolate anion, an unexpected high selectivity for the monosubstituted thioethers (90%) is obtained. Optimization of the reaction conditions showed that the stoichiometry of the reactants in this reaction is important to ensure the high selectivity and to prevent unwanted side reactions. Reaction of equimolar amounts of reagents at ambient temperature gave the best results. A mechanism consistent with these results, supported by UV-vis experiments, is presented. Selective 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.