High-Valent Pentamethylcyclopentadienylcobalt(III) or -iridium(III)-Catalyzed CH Annulation with Alkynes: Synthesis of Heterocyclic Quaternary Ammonium Salts

Nine types of diversely fused heterocyclic quaternary ammonium salts were constructed through an oxidative CH annulation reaction. Both high-valent pentamethylcyclopentadienylcobalt(III) and pentamethylcyclopentadienyliridium(III) were found to be effective as catalyst for this reaction. Broad substrate scope and good functional group tolerance were observed.