Cu-Catalyzed Regioselective C-H Amination of 2 H -Indazoles for the Synthesis of Indazole-Containing Indazol-3(2 H )-ones.

A copper-catalyzed C3 amination of 2-indazoles with 2-indazoles and indazol-3(2)-ones under mild conditions was developed. A series of indazole-containing indazol-3(2)-one derivatives were produced in moderate to excellent yields. The mechanistic studies suggest that the reactions probably proceed through a radical pathway.