Direct electrosynthesis of a series of novel caffeic acid analogues through a clean and serendipitous domino oxidation/thia-Michael reaction

A series of novel caffeic acid analogues have been synthesized in an experimentally simple electrochemical procedure employing electrons as the only reagents in aqueous solution without introducing any catalyst or oxidant. It has been shown that the reactions proceed via a domino of electrochemical and chemical events (EC mechanism) with an interesting regioselectivity in the formation of arylsulfonyl-functionalized N-caffeoyl amides and caffeate esters. All products were purely obtained at the surface of anode (carbon rods) in excellent yields and no extra purification was needed. Structural characterization of these novel compounds was also performed using various spectroscopic techniques: FT-IR, (HNMR)-H-1, (CNMR)-C-13 and HR-mass.