An electrochemical oxidative homo-coupling reaction of imidazopyridine heterocycles to biheteroaryls

Abstract

An electrochemical homo-coupling reaction of imidazopyridine heterocycles has been developed for the synthesis of biheteroaryls. This reaction features good compatibility, high yields and excellent regioselectivities, which provides an efficient access to biheteroaryl compounds.

Electrochemical C−H/N−H Oxidative Cross Coupling of Imidazopyridines with Diarylamines to Synthesize Triarylamine Derivatives

“…During current controlled electrolysis, the oxidation potential of anode ( vs Ag/AgCl) ranged from 1.51 to 2.52 V. Thus, both 1 a and 2 a could be oxidized at anode during the electrolysis. Also, the homo‐coupling of imidazopyridines was isolated in 26 % yield in the standard reaction, which has further proved the existence of imidazopyridines radical cation (Scheme ) …”

Recent Advances in Radical C−H Bond Functionalization of Imidazoheterocycles

“…Few transformations on imidazo[1,2-a]pyridines were summarized in this review using oxidation induced CÀ H activation. [41,61,83] We believe that the summarized pieces of literature along with mechanistic details will be useful for further development toward functionalization of imidazo[1,2a]pyridines and other similar kind of pharmaceutically relevant heterocycles. Current studies mainly deal with functionalization at C3-position of imidazo[1,2-a]pyridines and methods for functionalization of other positions are limited.…”

“…In 2018, Han and co-workers described an electrochemical strategy for the oxidative homo-coupling of imidazo[1,2-a]pyridines 1 to afford 2,2'-diphenyl-3,3'biimidazo[1,2-a]pyridines 39 using graphite plate as the anode and platinum plate as the cathode (Scheme 23). [41] This reaction was successfully applied for the homocoupling of other imdazoheterocycles viz. with arylboronic acids 40 using K 2 S 2 O 8 as an oxidant in a mixture of dichlrormethane (DCM) and water as solvent at room temperature (Scheme 24).…”

Electrochemical strategies for C–H functionalization and C–N bond formation

“…Finally, rearomatization of the generated arene radical through oxidation and loss of a proton provides (aza)indoles 391. A related mediator-based radical cyclization cascade approach was applied to the preparation of imidazo-fused N-heteroaromatic compounds (395) 921,922 However, here tetraarylhydrazine 393 was found to be the optimal redox catalyst. Nitrogen-centered radicals have also been harnessed for synthesis of nitrogen-doped polycyclic aromatic hydrocarbons (Scheme 116).…”