Stereoselective synthesis of chalcogen-tethered <i>γ</i>-lactams <i>via</i> 5-<i>exo-dig</i> cyclisation under visible-light irradiation

We report a rapid, eco-friendly, and catalyst-free method for the stereoselective synthesis of chalcogen-tethered γ-lactams under visible-light irradiation. Using dimethyl carbonate as a green solvent, the reaction proceeds <i>via</i> 5-<i>exo-dig</i> intramolecular radical cyclization, affording <i>Z</i>-configured γ-lactams with high selectivity and broad substrate scope, including sulfur and selenium derivatives. The protocol is operationally simple, metal-free, and aligns with green chemistry principles. Notably, its translation to continuous-flow conditions using a K₃PO₄ glass-packed reactor significantly improved the reaction rate and yield, demonstrating excellent scalability. This approach offers a sustainable and efficient route to valuable chalcogenated γ-lactams, relevant to medicinal and synthetic chemistry.