Electrooxidative iridium-catalyzed sp2 C–H activation–annulation leading to cationic π-extended heteroaromatics

Abstract

This study demonstrates an electrochemically driven, Ir(III)-catalyzed method for pyridine-, azo-, and purine-directed olefinic and aromatic C(sp²)–H activation and regioselective annulation with alkynes for the synthesis of biologically useful quaternary ammonium salts. This approach notably eliminates the need for stoichiometric amounts of external oxidants, offering a broader substrate scope along with improved product regioselectivity under mild electrolysis conditions as compared to previously employed strong oxidant conditions. Detailed mechanistic insights, including the isolation, characterization, and cyclovoltammetric analysis of catalytically relevant iridium(III) and iridium(I) intermediates, provided strong supporting evidence for an Ir(III/I) catalytic cycle operation.