Jhilik Dutta, Sayan Ghosh, Suman De Sarkar
An electrochemical protocol for the regioselective synthesis of multi-substituted pyridines via a (3+3) annulation is described. The strategy utilizes enamine-iminium cross-coupling to construct the pyridine core with high functional group tolerance under mild reaction conditions. Alongside, C5-deuterated pyridines are achieved in a single step using deuterium oxide as the inexpensive deuterium source. In addition to the electro-redox events, electrogenerated acid (EGA) plays a decisive role in key bond-forming steps. Mechanistic studies, including control experiments and cyclic voltammetry, reveal the involvement of EGA and assist in identifying crucial reaction intermediates. The synthetic utility of the method is showcased by post-annulation derivatization, affording a diverse library of pyridine derivatives.