Annulation of Phthalic Anhydrides with 2-Arylbenzimidazoles toward Phenanthridine-Fused Heterocycles: TBAI-Promoted Palladium Catalysis

A palladium/PPh₃/TBAI catalyzed reaction has been developed, enabling sequential decarbonylation/decarboxylation/C-N and C-H bond formation within a single synthetic step. This innovative methodology features annulation of phthalic anhydrides with 2-arylbenzimidazoles, with TBAI serving as a vital iodide source that enhances the reactivity of the Pd(OAc)₂/PPh₃ catalytic system. Notably, the incorporation of phthalic anhydride not only streamlines the synthesis but also supports environmentally friendly practices by minimizing waste and lessening reliance on hazardous substances typically associated with conventional arylation techniques.