Oxidation of N-Acyl Hydrazones of o-Aminoaryl Ketones: Synthesis of 2-Acylaminoidazoles

Synthesis of 3-substituted-7-acylaminoindazoles via the lead tetraacetate oxidative cyclization of N-carbonylhydrazones of o-aminoarylketones is reported. A mechanism involving formation of organolead, azoacetate and o-quinonemethide imine intermediates is proposed. The formation of the indazole heterocycle was confirmed by an independent synthesis of 7-benzoylamino-3-phenylindazole