Cyclization of Azobenzenes Via Electrochemical Oxidation Induced Benzylic Radical Generation.

An electrochemical oxidation-induced cyclization of -alkyl-substituted azobenzenes has been developed. The direct electrochemical benzylic C-H functionalization with respect to azobenzenes could proceed in the absence of any catalyst or external chemical oxidant to afford a number of 2-indazole derivatives in moderate to good yields. This protocol enables the reuse of the byproduct to the same 2-indazoles, thus significantly reducing pollution discharge in synthetic chemistry.