Iridium(III)-Catalyzed Tandem Annulation Synthesis of Pyrazolo[1,2-α]cinnolines from Pyrazolones and Sulfoxonium Ylides.

A highly efficient iridium-catalyzed cascade annulation of pyrazolones and sulfoxonium ylides to access various pyrazolo[1,2-α]cinnoline derivatives has been achieved. This novel approach expanded the application scope of coupling partners to ylides. The control experiments were performed to give insight into the mechanism of this reaction.