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

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 sp³-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.