2-Chlorophenothiazine (2CPTZ), is an important intermediate in the synthesis of neuroleptic drugs, such as chlorpromazine (CPZ), perphenazine, prochlorperazine. CPZ is subject to a significant amount of first-pass metabolism, including hydroxylation, Ndealkylation, N-oxidation, and S-oxidation. Chlorpromazine (CPZ) is primarily metabolized as chlorpromazine-S-oxide (CPZ-SO) and was found to have the same effect as CPZ in the vasomotor and central nervous systems. Chemical methods to oxidise PTZ derivatives to sulfoxide are shown in Scheme 1. Owens and co-workers prepared phenothiazine sulfoxide (PTZ-SO) using aqueous nitrous acid and hydrogen peroxide at room temperature (PTZs-SO, 95% yield with CPZ-SO, yield 74%). Ryoji and co-workers investigated the preparation of sulfoxide compounds using aqueous hydrogen peroxide, a tungstate complex, and a quaternary ammonium hydrogensulfate as an acidic phase-transfer catalyst in 95% yield. Bosch and colleagues also reported sulfoxidation using nitric oxide oxidation (CPZ-SO, 99% yield). Liu and colleagues used ferric nitrate nonahydrate (Fe(NO3)3.9H2O) as a catalyst and oxygen as a green oxidant for the selective oxidation from thioethers to sulfoxides including on CPZ with an 88% yield. Stadler and Roth reported a microfluidic electrochemical preparation of CPZ-sulfoxide. Four drugs were subjected to continuous-flow electrolysis, including the conversion of CPZ to CPZ-SO with an 83% isolated yield. However, this technique has some limitations, including 1) microfluidic-electrosynthesis can be complex to design, set up, and operate, 2) and high-cost equipment. Scheme 1. Previous approaches (a-d) towards synthesising PTZs sulfoxide using chemical oxidants and microfluidic electrosynthesis and this study: a green electrosynthesis approach.