Palladaelectro-catalyzed ortho-C-H-monoarylation of 2-phenylpyridines with arenediazonium salts.

Abstract

Metal-catalyzed electrochemical C-H activation has emerged as a promising strategy for cost-effective and sustainable molecular assembly. Herein, we describe a palladaelectro-catalyzed ortho-C-H activation/arylation of arenes, using arenediazonium salts as aryl sources. The arylation of 2-phenylpyridine derivatives with ortho-selectivity was achieved under electrochemical conditions, avoiding stoichiometric chemical oxidants and employing exceedingly mild conditions. This versatile arylation reaction also features a broad substrate scope, accommodating both electron-withdrawing and electron-donating groups on the aryl and pyridine moieties, with moderate yields. Detailed mechanistic studies using cyclic voltammetry, reactions in the presence of TEMPO, and experiments in a divided cell strongly support electrochemical palladium catalyst recycling and the formation of aryl radicals through cathodic reduction of arenediazonium salts.