Ruthenium‐catalyzed C−H Functionalization/Annulation of N‐Aryl Indazoles/Phthalazines with Sulfoxonium Ylides to access Tetracyclic‐fused Cinnolines

Abstract A ruthenium‐catalyzed cascade C−H functionalization/intramolecular annulation of N ‐phenylindazoles with sulfoxonium ylides was developed for the synthesis of indazolo[1,2‐ a ]cinnolinones. This transformation features with C−H/N−H functionalization in one pot , the utilization of cost‐effective ruthenium catalyst, wide substrate scope and good functional group tolerance. Moreover, the reaction of 2‐arylphthalazine‐1,4‐diones with sulfoxonium ylides led to phthalazino[2,3‐ a ]cinnolindiones under standard conditions.