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