The oxidation of diethyl 3-thienylmalonate (1) by metal oxidants (Fe (ClO4) 3, Mn (OAc) 3, MnO2 and CuO) in various solvents at 60° C affords dimerization products arising from side- chain and nuclear coupling of the intermediate delocalized malonyl radicals 6. Metal to sulphur binding is suggested to play a role in controlling the distribution of dimers 2–5. The higher thermodynamic stability of unsymmetric dimer 3, along with its oxidative ...