Synthesis of Iodinated Semisaturated Heterobicycles via a Temporal Dual Metal-Catalyzed Cycloaddition/Photochemical Carbohalogenation.

A dual-catalytic approach for the regioselective synthesis of iodinated semisaturated fused heterobicycles is reported. The one-pot sequential use of copper and palladium under blue-light irradiation enables the efficient synthesis of 1,2,3-triazole-fused piperidines in high yields from acyclic precursors, avoiding the need for highly reactive small-ring alkynes. Medicinally relevant compounds and functionally diverse product derivatives are described. The cooperativity between two independent bond-forming cycles is explored, and mechanistic studies of the photochemical palladium-catalyzed carboiodination suggest that cyclization is light-dependent.