Visible-light-driven photocyclization reaction: photocatalyst-free mediated intramolecular N-N coupling for the synthesis of 2H-indazole-3-carboxamides from aryl azides

In this report, a visible-light-driven photocyclization reaction of aryl azides to access 2H-indazole-3-carboxamides in moderate to excellent yields has been realized efficiently under photocatalyst-free and external additive-free conditions. An N-N bond coupling was achieved for this N-atom incorporation transformation using an aryl azide as the N-atom source. The transformation of the aryl azide by photocyclization was also achieved under sunlight irradiation. Additionally, this protocol, as a green and sustainable process, possesses some advantages such as broad substrate scope, step- and atom-economy, environmental friendliness and mild reaction conditions.