Bypassing β-Hydride Elimination: Excited-State Pd-Catalyzed C(sp3)–C(sp2) Coupling at Room Temperature

by Dr. Kuntal Pal, Rajesh Kancherla, Sayan Dutta, Dr. Serik Zhumagazy, Dr. Bholanath Maity, Prof. Dr. Luigi Cavallo, Prof. Dr. Magnus Rueping
Year: 2025 DOI: https://doi.org/10.1002/ange.202522979

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Angewandte Chemie

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 sp3 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(sp3)–C(sp2) 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.