Synthetic Strategies for Benzimidazole-Based Heterocycles via Transition Metal–Catalyzed C–H Annulation

The N–H-benzimidazole directing group (DG)–assisted transition metal (TM)–catalyzed C(sp2)–H activation and annulation reaction emerged as a powerful strategy for the synthesis of benzimidazole-based organic compounds, natural products and late-stage functionalization. This account highlights the recent advancements made in rhodium- and palladium-catalyzed C–H activation/annulation reactions on the benzimidazole core developed over the past decades. These strategies have facilitated the formation of C–C, C–N, C–O, and C–F bonds through Rh- and Pd-catalyzed cross-coupling annulation. A diverse array of diazo, alkynes, maleimides, olefins, ylides and aryl halides were used as the coupling partners to achieve C–H annulation. This review summarizes benzimidazole-based synthetic strategies, highlighting the substrate scope, key mechanistic insights and the nature of the coupling partners.