Synthesis of (2H)-Indazoles and Dihydrocinnolinones through Annulation of Azobenzenes with Vinylene Carbonate under Rh(III) Catalysis

The Rh(III)-catalyzed C-H functionalization and subsequent intramolecular cyclization between azobenzenes and vinylene carbonate is described herein. Depending on the electronic property of azobenzenes, this transformation results in the formation of (2H)-indazoles or dihydrocinnolin-4-ones through the generation of ortho-alkylated azo-intermediates followed by decarboxylation. Surprisingly, vinylene carbonate acts as an acetaldehyde or acetyl surrogate to enable the [4 + 1] or [4 + 2] annulation reaction. This transformation is characterized by its mild reaction conditions, simplicity, and excellent functional group compatibility.

Automated summary

The Rh(III)-catalyzed C-H functionalization and subsequent intramolecular cyclization between azobenzenes and vinylene carbonate leads to the formation of different compounds, such as (2H)-indazoles or dihydrocinnolin-4-ones. Vinylene carbonate surprisingly acts as an acetaldehyde or acetyl surrogate, enabling [4 + 1] or [4 + 2] annulation reaction. This transformation stands out for its mild reaction conditions, simplicity, and excellent functional group compatibility.