PIDA-Mediated Oxidative Ring-Opening of 2H-Indazoles with N-Hydroxyphthalimide

Abstract

A fast and convenient phenyliodine(III) diacetate (PIDA) mediated oxidative ring-opening of 2H-indazole with N-hydroxyphthalimide via C–N bond cleavage has been developed under metal-free reaction conditions. The new protocol afforded a range of unsymmetrical ortho-amide substituted azobenzenes with wide functional group tolerance in good yields. Mechanistic investigations suggest that the reaction likely proceeds through the formation of a phthalimide-N-oxyl (PINO) radical adduct with 2H-indazoles, followed by a rearrangement to produce the unsymmetrical azobenzene derivative.