A Copper-Catalyzed Tandem C–H ortho-Hydroxylation and N–N Bond-Formation Transformation: Expedited Synthesis of 1-(ortho-Hydroxyaryl)-1H-indazoles

A facile, one-pot synthesis of 1H-indazoles featuring a Cu-catalyzed C–H ortho-hydroxylation and N–N bond-formation sequence with the use of pure oxygen as the terminal oxidant was developed. The reaction of readily available 2-arylaminobenzonitriles with various organometallic reagents led to ortho-arylamino N–H ketimine species. Subsequent Cu-catalyzed hydroxylation at the ortho position of the aromatic ring followed by N–N bond formation in DMSO under a pure-oxygen atmosphere afforded a wide variety of 1-(ortho-hydroxyaryl)-1H-indazoles in good to excellent yields. This efficient method does not require the utilization of noble-metal catalysts, elaborate directing groups, or privileged ligands.

A Cu-catalyzed C(sp²)–H ortho-hydroxylation and N–N bond-formation sequence is described for the synthesis of 1-(ortho-hydroxyaryl)-1H-indazoles by using pure oxygen as the terminal oxidant. The ortho-arylamino N–H ketimine moiety serves as an effective directing group for C(sp²)–H oxidation. acac = acetylacetonate.

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