The electrochemical synthesis of organic diseleno and ditelluro derivatives from an alkyl RX or aryl halide ArX, and elemental Se and Te, is carried out under controlled potential in a divided cell, or at constant current in an undivided cell filled with an aprotic solvent/supporting electrolyte system. The undivided cell is equipped with a Mg anode and contains a fluoride salt (Et4NF.2H2O) which gives the MgF2 complex and avoids the formation of MgE2 (E = Se, Te) during electrolysis. Elemental Se or Te is reduced as powder with sonication, or as a sacrificial cathode. Diorganyl dichalcogenides are thus prepared at room temperature by SN2 substitution reactions in aliphatic series, and by SNAr and SRN1 substitution reactions in aromatic series. In the SRN1 process, the key step, which is the coupling reaction Ar·/E22-, is in competition with two main side-reactions, that is the hydrogenation of Ar· by the solvent and the cathodic reduction of Ar· to Ar-. The highest yield of ArEEAr are obtained in MeCN and in the presence of a redox mediator. The technique involving the SRN1 process is particularly suitable for aryl halides for which lithiation followed by Se or Te insertion cannot be carried out.
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