Electrochemical synthesis of new phenothiazine derivatives was carried out via electrochemical oxidation of hydroquinones (1a and 1b) in water/ethanol (90/10) solution containing 0.15 mol L-1 phosphate buffer (pH 6.0) in the presence of 2-aminothiophenol (3) using cyclic voltammetry (CV) and controlled potential coulometry (CPC) methods. The results show that electrochemically generated p-benzoquinones participated in the 1,4-Michael addition reaction with 3 via an ECEC mechanism to form phenothiazine derivatives 6a and 6b in good yields and high purity using a facile, one-pot, clean, and non catalyst method by three carbon electrodes in an undivided cell.