Silyl Radical-Mediated Carbocyclization of Acrylamide-/Vinyl Sulfonamide-Attached Alkylidenecyclopropanes via Photoredox Catalysis with a Catalytic Amount of Silane Reagent

Abstract

A silyl radical-mediated carbocyclization of acrylamide-/vinyl sulfonamide-attached alkylidenecyclopropanes via photoredox catalysis with a catalytic amount of silane reagent is reported in this paper. With this protocol, a highly efficient synthesis for the construction of lactam- and sultam-containing polycyclic derivatives in 63–95% yields was achieved with a broad substrate scope. A reasonable reaction mechanism was proposed based on control experiments, where the catalytic amount of tris­(trimethylsilyl)­silane was used as the radical-based reagent.

Visible-light-induced reactions of methylenecyclopropanes (MCPs)

“…In 2021, our group reported multiple-step catalysis to realize the tandem cyclization of MCPs tethered with acrylamide 81 (or vinyl sulfonamide) under visible-light irradiation (Scheme 19). 52 Multicatalysis has conspicuously contributed to the field of catalysis in synthetic chemistry, but the complicated details remain underinvestigated. 53 Clearly, governing several perfectly cooperative active catalysts in one pot without considerable entropic penalties is challenging when attempting to achieve mechanistic insight (Scheme 18).…”

Radical Covalent Catalysis: Recent Advances and Future Developments

“…In 2021, Shi and coworkers developed the silyl radical catalyzed carbocyclization of alkylidenecyclopropanes under visible light (Scheme 16). [29] Lactam‐ and sultam‐containing polycyclic derivatives were rapidly constructed in 63 %–95 % yields. The authors believed that the intermediate 83 , generated through the addition of silyl radical to alkylidenecyclopropanes 83 a , was the key intermediate in this reaction.…”

The synthesis of seven- and eight-membered rings by radical strategies

“…Wei, Shi, and co-workers subsequently reported a similar reaction, in which 4CzIPN as the photosensitizer, quinuclidine as the HAT catalyst, Co-(dmgH) 2 PyCl as the catalyst, and pyridine as the base, achieved the synthesis of polycyclic derivatives containing sultam and lactam (Scheme 26). 51 Notably, the generated silyl radical was not attached to the final product, which suggested that the main function of the silyl radical was to mediate the cyclization. A wide range of functional groups on the aryl ring were found to be well tolerated in this transformation.…”