Electrochemical oxidation of 4-tert-butylcatechol (1) has been studied in the presence of 1,3-dimethylbarbituric acid (2a) and 1,3-diethyl-2-thiobarbituric (2b) acid as nucleophiles in aqueous solution, using cyclic voltammetry (CV) and controlled-potential coulometry. The results indicate that the quinone derived from 4-tert-butylcatechol (1) participates in a Michael addition reaction with 2 to form the corresponding 5,5-disubstituted pyrimidine derivatives (5a-5b). In this work, we have proposed a mechanism for the electrode process. The electrochemical synthesis of 5a and 5b has been successfully performed at carbon rod electrodes in an undivided cell in good yield and purity.