Oxidation Potential-Guided Electrochemical Radical–Radical Cross-Coupling Approaches to 3-Sulfonylated Imidazopyridines and Indolizines

Abstract

Oxidation potential-guided electrochemical radical− radical cross-coupling reactions between N-heteroarenes and sodium sulfinates have been established. Thus, simple cyclic voltammetry measurement of substrates predicts the likelihood of successful radical−radical coupling reactions, allowing the simple and direct synthetic access to 3-sulfonylated imidazopyridines and indolizines. The developed electrochemical radical−radical cross-coupling reactions to sulfonylated N-heteroarenes boast the green synthetic nature of the reactions that are oxidant-and metal-free.

Recent advances in metal catalyst- and oxidant-free electrochemical C-H bond functionalization of nitrogen-containing heterocycles

“…In 2021, Oh and co-workers (Kim et al, 2021) also developed an electrochemical oxidative radical C-H sulfonylation of imidazopyridines 81 and indolizines 80 under mild redox reagentfree and metal catalyst-free reaction conditions. A series of sulfonylated N-heteroarenes were achieved in moderate to good yields in an undivided cell equipped with a carbon rod anode and a platinum plate cathode/a nickel plate cathode at a constant current of 7 mA using LiClO 4 as the electrolyte (Scheme 18).…”

Visible Light‐Promoted, Photocatalyst‐Free C(sp2)−H Bond Functionalization of Indolizines via EDA Complexes

“…To do that, transition metals are commonly employed in catalyzing borylation, [10] arylation, [11] acyloxylation [12] and propargylation [13] reactions. Despite this, few metal-free approaches are available in the literature for CÀ H functionalization of indolizines such as electrochemical sulfonylation, [14] alkylation, [15] and CÀ H dithiocarbamation [16] www.eurjoc.org reactions. More recently, visible light-induced operations on indolizines have arisen as a new functionalization strategy.…”

Chiral Phosphoric Acid-Catalyzed Asymmetric Arylation of Indolizines: Atroposelective Access to Axially Chiral 3-Arylindolizines

“…Similarly to its isomer indole, indolizine is also a pharmaceutically important scaffold and prevails in numerous biologically active natural products in addition to fluoroscent materials . Accordingly, much interest has been paid to the functionalization of indolizine, including transition-metal-catalyzed cross-couplings, electrochemical coupling, organocatalytic alkylation, and others . Among these advances, several excellent asymmetric C3-functionalizations of indolizine scaffolds were established due to the electron-rich property of the aromatic ring .…”