Chemo and regioselective serendipitous electrochemically initiated spirocyclization of caffeic acid esters with barbituric acid derivatives

An interesting sequence of oxidation/Michael addition/oxidation/spirocyclization is observed in the electrolysis of caffeic acid esters in the presence of barbituric acid derivatives leading to the synthesis of a series of novel spirocycles. In an experimentally simple and clean procedure, the electrolyses proceed via a domino of electrochemical (E) and chemical (C) events with employing electrons as the only reagents in aqueous solution without introducing any catalyst or oxidant. From mechanistic point of view, a new type of domino mechanism (ECEC_i, C_i = spirocyclization) is proven with a unique C_i phenomenon at final step. Also, in light of experimental and theoretical NMR investigations, highly chemo and regioselectivities have been detected in these synthetic electrolyses.