Mechanistic Details of the Pd‐catalyzed and MPAA Ligand‐Enabled β‐C(sp3)‐H Acetoxylation of Free Carboxylic Acid

The Pd-catalyzed C(sp³)-H bond acetoxylation of aliphatic carboxylic acid is studied at the DFT level. The ligand and base are important in determining the mechanism and selectivity of the reaction. Acetic anhydride is critical in leading the reaction to acetoxylation, instead of lactonization. This study sheds light on the further development of transition metal-catalyzed C−H bond oxidation reactions.

Abstract

Transition metal-catalyzed C−H bond oxidation of free carboxylic acid stands as an economic, selective, and efficient strategy to generate lactones, hydroxylated products, and acetoxylated products and attracts much of the chemists’ attention. Herein, we performed a density functional theory study on the mechanism and selectivity in Pd-catalyzed and MPAA ligand-enabled C−H bond acetoxylation reaction. It was found that the ligand, base, and substrate are important in determining the reaction mechanism and the selectivity. The acetic anhydride additive is critical in leading the reaction to be acetoxylation, instead of the lactonization, through a facile σ-bond metathesis mechanism that leads to the Pd-OAc in-termediate. Our study sheds light on the further development of transition metal-catalyzed C−H bond oxidation reactions.

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