Molybdenum‐Catalyzed Intramolecular Deoxygenative Annulation of 2‐Acylazobenzenes to Access N2,C3‐Disubstituted 2H‐indazoles

A molybdenum‐catalyzed synthesis of N2,C3‐disubstituted 2H‐indazoles from readily available 2‐acylazobenzenes via deoxygenation of C=O and annulation has been described. The non‐noble metal catalytic system has good tolerance of functional groups, and various N2,C3‐disubstituted 2H‐indazoles have been constructed in 24% to 99% yield. This reaction is easy to scale‐up and has shown its applications in deriving valuable fluorescent and bioactive compounds. The plausible mechanism shows the plausible processes of molybdenum‐catalyzed deoxygenative annulation.