An electrochemical carbon-skeleton rearrangement of methylmalonate skeleton to succinate was successfully mediated by an imine/oxime-type cobalt complex using diethyl 2-bromomethyl-2-phenylmalonate as a model substrate of a coenzyme B-12-dependent enzymatic reaction. Cyclic voltammetric and mass spectrometric studies revealed that this electrocatalysis of the alkyl bromide with 1,2-migration of a carboxylic ester group was achieved by the duet redox process between the reduction of the monoalkylated complex and the oxidation of the dialkylated complex.