Copper-catalyzed synthesis of substituted indazoles from 2-chloroarenes at low catalyst-loading.

An efficient and convenient access to 1-substituted indazol-3-ones 2 has been achieved throughout the intramolecular C-N bond formations of 2-chloro-benzoic acid-N'-aryl and alkyl-hydrazides employing 0.5 mol% of cuprous (I) iodide and 20 mol% of L-proline as catalyst precursors under mild conditions in moderate to excellent yields.