Ligand-Enabled, Palladium-Catalyzed β‑C(sp3)–H Arylation of Weinreb Amides

We report the development of Pd­(II)-catalyzed C­(sp3)–H arylation of Weinreb amides. Both the inductive effect and the potential bidentate coordination mode of the Weinreb amides pose a unique challenge for this reaction development. A pyridinesulfonic acid ligand is designed to accommodate the weak, neutral-coordinating property of Weinreb amides by preserving the cationic character of Pd center through zwitterionic assembly of Pd/ligand complexes. Density functional theory (DFT) studies of the C–H cleavage step indicate that the superior reactivity of 3-pyridinesulfonic acid ligand, compared to Ac-Gly-OH and ligandless conditions, originates from the stabilization of overall substrate-bound Pd species.