Copper‐Catalyzed Regio‐ and Diastereoselective Dearomative Carbosilylation of Unactivated Arenes by Intercepting the Dienyl Radical

Abstract The radical‐mediated dearomatization of aromatic systems to generate cyclohexadienyl radical intermediates represents a crucial strategy for constructing three‐dimensional molecular architectures. Conventional approaches typically through ipso ‐addition and subsequent proton/oxygen/carbon dioxide trapping to suppress rapid re‐aromatization, significantly constraining product diversity. Furthermore, dearomative bifunctionalization reactions—which offer enhanced step‐ and atom‐economy—remain substantially underdeveloped. Herein, we disclose a copper‐catalyzed radical dearomative 1,4‐ and 1,2‐carbosilylation strategy applicable to diverse unactivated (hetero)aromatic substrates to selectively construct spiro‐ or fused‐cyclic products. The resulting vinyl and allylic silanes serve as versatile synthetic handles for downstream transformations, enabling the rapid construction of sp 3 ‐rich polycyclic scaffolds that are highly valuable in drug discovery. Mechanistic and DFT studies indicate that the reaction commences with copper(I)‐silicon‐mediated halogen atom transfer of readily available aryl iodides to generate aryl radicals. These reactive species exhibit dual pathways: direct ipso ‐addition to aromatic rings or 1,5‐hydrogen atom transfer followed by alkyl radical‐mediated ortho ‐addition. Subsequent trapping of the resulting dienyl radicals by copper(II)‐silicon species yields complex polycyclic systems containing cyclohexadienylsilicon frameworks with excellent chemo‐, regio‐ and diastereoselectivity. This methodology not only establishes a novel paradigm for copper‐catalyzed radical dearomative bifunctionalization but also provides an efficient radical ipso‐ and ortho ‐addition platform for synthesizing architecturally intricate polycyclic compounds.