Cobalt-Photoredox-Catalyzed C-H Annulation of N-Aryl Benzamides with 2,5-Dihydrofuran: Double Stereo Induction.

The resurgence of photocatalysis, a green, eco-friendly strategy that harnesses light to enable valuable organic transformations, offers a blueprint for developing green synthetic methodologies for the synthesis of chiral molecules via enantioselective C-H activation. Although there are several methods for single-chirality induction, multi stereo-element induction with photoredox remains underexplored. Herein, we report an effective one-step method for inducing central and C-N axial chirality via photoredox-mediated C-H annulation of benzamides. This methodology avoids the stoichiometric amount of metal oxidant, and the reaction proceeds under mild reaction conditions. This photoredox strategy enables C-H annulation of various benzamides with good functional group tolerance, affording central and atropo-chiral products with high enantio- and diastereoselectivity (28 examples, up to >99% ee and >20:1 dr). Catalytic and stoichiometric reactions with a cobaltacycle suggested its involvement in the catalytic cycle and potential role in enantiocontrol. The gram-scale reaction demonstrates the practicality of the developed protocol. Notably, both the solvent and the ligand can be recovered and reused, highlighting the potential sustainability of the developed methodology.