Cobalt‐Promoted <i>Para</i> C─H Amination of 3‐Acetyl Substituted Nitroarenes with Arylhydrazines

Abstract We report a method to furnish substituted 1H ‐indazoles via a coupling of 3‐acetyl substituted nitroarenes and arylhydrazines. Reactions progressed in the presence of cobalt(II) acetylacetonate catalyst, TEMPO oxidant, and Cs 2 CO 3 base. Functional groups including bromo, chloro, nitro, and trifluoromethoxy groups were compatible with reaction conditions. The proposed mechanism was based on a nucleophilic substitution of hydrogen para to nitro group. Our method feature a convenient pathway to directly obtain substituted 1H ‐indazoles which avoid the use of pre‐functionalized starting materials. Indazole could play a role as the directing group for a palladium‐catalyzed C(sp 2 )─H arylation with iodobenzene.