Electrochemical oxidation of catechols (1a-d) has been studied in the presence of N,N-dimethylethylendiamine (3) as a nucleophile in aqueous solutions, using cyclic voltammetry, constant-current coulometry and control led-potential coulometry. The results indicate that the quinones derived from catechols (2a-d) participate in Michael addition reactions with N,N'-dimethylethylendiamine (3) via the ECECE mechanism to form the corresponding quinoxalinedione derivatives (6a-c). (c) 2006 Elsevier Ltd. All rights reserved.