Construction of Vinyl‐SubstitutedN‐HeterocyclesviaRh(III)‐Catalyzed C−H Functionalization/Annulation of Pyrazolidinones

Abstract The transition‐metal‐catalyzed C−H activation and annulation reactions of pyrazolidinones with 4‐vinyl‐1,3‐dioxolan‐2‐one or vinylene carbonate are described herein. This protocol provided two types of pyrazolo[1,2‐a]cinnolines as essential assets for the development of bioactive compounds, and the synthetic practicality was performed and explained with 44 examples. The possible mechanism of these two reactions is proposed based on preliminary studies and previous reports, and no oxidant was added to both reactions. magnified image