Visible-Light-Driven B-to-C Atom Swap: Scalable Skeletal Editing Access to Benzimidazoles from Diazaborines

We report a practical and scalable boron-to-carbon atom swapping methodology that facilitates the efficient synthesis of benzimidazole-based drugs. This exogenous photocatalyst-free, visible-light-driven transformation is selective and controllable, proceeding under mild conditions. It provides a unique strategy to address a series of challenges associated with de novo synthesis and photocatalytic skeleton editing for constructing medicinal benzimidazole derivatives, including high-energy barrier obstacles, metal residue, limited UV light, scalability, and poor functional group tolerance. Specifically, it enables a 100 mmol scale synthesis with broad functional group tolerance, avoiding metal contamination that plagues catalytic systems. Our density functional theory (DFT) calculations support our proposed B-to-C atom swap mechanism and indicate that the solvent alcohol plays an auxiliary role in promoting the reaction initiation by inserting the C-O bond of the aldehyde into the N-B bond.