An efficient transition-metal-free synthesis of 1H-indazoles from arylhydrazones with montmorillonite K-10 under O2 atmosphere.

An efficient transition-metal-free synthetic method of 1 H -indazoles has been developed. The reaction of arylhydrazones in the presence of montmorillonite K-10 in 1,2-dichlorobenzene at 130 °C afforded 1 H -indazoles in good yields most likely via a sequential intramolecular nucleophilic cyclization and an aerobic oxidation pathway. [ABSTRACT FROM AUTHOR]