Blue Light-Mediated Multicomponent Synthesis of 5-Amino-4-chalcogenyl-1H-pyrazoles.

Visible-light-mediated multicomponent reactions offer a simple and efficient approach for constructing functionalized heterocycles. Herein, we report a photocatalyst-free, iodine-mediated multicomponent protocol for the synthesis of 5-amino-4-chalcogenyl-1H-pyrazoles from 3-oxo-3-phenylpropanenitriles, arylhydrazines, and diorganyl dichalcogenides under blue-LED irradiation. The transformation proceeds without transition metals, external oxidants, or additives. Notably, the same optimized reaction conditions enable access to both selenium- and sulfur-containing derivatives without reoptimization, demonstrating the robustness and generality of the methodology. The protocol exhibits a broad substrate scope, enabling the preparation of more than 30 structurally diverse examples and tolerating electron-donating and -withdrawing substituents on both the dichalcogenide and hydrazine partners. Selenium derivatives were obtained in excellent yields, while disulfide analogues were also formed in high yields (up to 98). The synthetic utility was further demonstrated through gram-scale reactions, crossover experiments, and downstream derivatization via the Clauson-Kaas reaction. Control and radical-trapping experiments support a visible light-induced radical pathway, where photoirradiation is responsible for radical generation, enabling the formation of chalcogen-centered species. Overall, this study provides a straightforward strategy for the synthesis of chalcogen-functionalized pyrazoles under mild, metal-free conditions.