A decarboxylation process for coupling aromatic compounds wherein cyclic hydrocarbons and heterocyclic compounds having at least one labile ring hydrogen are reacted with the mono silver salts of aromatic carboxylic acids, or mono silver salts of unsaturated compounds such as .alpha.,.beta.-ethylenically unsaturated acid compounds, or silver trifluoroacetate, or the mono silver salts are reacted with themselves, by heating to temperatures of 100.degree. to 500.degree. C. at pressures of 0.1 to 10 atmospheres, or by irradiating the reactants with ultraviolet light of 200 to 400 nanometers at temperatures of -30.degree. to 100.degree. C. The resulting dimers, trimers, polysubstituted polyphenyls, polyheterocyclics and trifluoromethylated aromatics are useful as heat transfer media, as intermediates for high molecular weight polymers, pesticides and petroleum additives, and as scintillation counters.