Ligand-Enabled Pd-Catalyzed C(sp3)-H/C(sp2)-H Coupling
Haiwei Zhao1, Zhen Li1, Xinyu Zhu1
1Department of Chemistry, The Scripps Research Institute, La Jolla, California 92037, United States.
None:
Palladium-catalyzed β and γ-C-H arylation of free carboxylic acids with both aryl boron reagents and aryl iodides has been extensively developed in recent years. Replacing these aryl coupling partners with simple arenes remains a significant challenge. By developing pyridone-morpholine ligands, we disclosed the β-methylene C-H (hetero)arylation of acyclic aliphatic acids and the γ-(hetero)arylation of cycloalkane carboxylic acids using benzene, furan, thiophene, and C-2 substituted pyridine as coupling partners. Preliminary mechanistic studies suggest that the reaction proceeds via ligand-promoted dehydrogenation of aliphatic carboxylic acids, C(sp2)-H activation of (hetero)arenes, and subsequent hydroarylation. Building on the mechanistic insights, we developed a dual-ligand catalysis system with one ligand promoting dehydrogenation and the other enhancing subsequent steps to enable coupling of C(sp3)-H bonds with indoles and pyrroles as reaction partners.
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