Rhodium-Catalyzed C-H Activation/Annulation of N-Aryl-pyrazolidinones with Vinylene Carbonate

A rhodium-catalyzed C-H activation/annulation of N-aryl-pyrazolidinones with vinylene carbonate was developed. The utilization of vinylene carbonate as the acetylene surrogate furnished the successful construction of non-substituted 5,6-pyrazolo[1,2-a]cinnoline derivatives, which are difficult to synthesize through other procedures. In this work, a series of variously substituted pyrazolo[1,2-a]cinnolines were obtained in yields up to 98 % with broad substrate scope and excellent selectivity. Moreover, external oxidants were not required in this protocol with H2O and CO2 as the clean by-products.

Automated summary

A rhodium-catalyzed C-H activation/annulation of N-aryl-pyrazolidinones with vinylene carbonate was developed, leading to the successful construction of non-substituted 5,6-pyrazolo[1,2-a]cinnoline derivatives. This method provides an efficient and selective approach to synthesizing these derivatives, which are challenging to obtain using other procedures. Importantly, the protocol does not require external oxidants and generates water and carbon dioxide as clean by-products.