A sustainable electrochemical phosphonylation of phenothiazine. Synthesis of a C-phosphonium betaine with powerful antibacterial activity

To demonstrate the capabilities of electrochemistry in the synthesis of organic compounds, we developed a facile and sustainable direct electrochemical phosphonylation of phenothiazine with triphenylphosphine. In this work, we demonstrated that electrochemically produced phenothiazine-5-ium can react with triphenylphosphine in a water/acetonitrile mixture under simple conditions using graphite and stainless steel electrodes in an undivided cell, galvanostatically and without the use of any catalyst, to synthesize the corresponding C-phosphonium betaine in good yield. The synthesized phosphonium betaine shows strong antibacterial activity against a variety of Gram positive and negative bacteria.