Bypassing β‐Hydride Elimination: Excited‐State Pd‐Catalyzed C(sp ³ )–C(sp ² ) Coupling at Room Temperature

Abstract Catalytic modification of C−H bonds using palladium is highly appealing, but transformations involving alkyl‐Pd(II) intermediates with β ‐hydrogens are challenging due to the propensity for β ‐hydride elimination. To address this, selective arylation of sp 3 C−H bonds in amides and alcohols has been achieved using divalent palladium as an excited‐state transition metal (TM) species at room temperature. Our approach unveils a non‐redox‐neutral pathway to achieve C(sp 3 )–C(sp 2 ) cross‐couplings, utilizing aryl iodides as both hydrogen atom transfer (HAT) and arylating agents for the first time under Pd‐photochemical conditions. The mechanism involves photo‐induced Pd(II)‐catalyzed aryl radical generation, HAT, and aryl migration, effectively bypassing the common β ‐hydride elimination and annulation pathways. Mechanistic investigations using isotope‐labeled compounds and density functional theory (DFT) studies support the mechanistic rationale, affirming both the feasibility and intricacies of this effective transformation.