Palladium-Catalyzed Ligand-Free ortho-Deuteration of Aromatic Carboxylic Acids with D2O

Abstract A ligand-free, palladium-catalyzed ortho-deuteration of aromatic carboxylic acids was developed using D2O as the deuterium source. Compared to their meta-substituted analogues, an unusually lower reactivity in para- and ortho-substituted benzoic acids toward hydrogen isotope exchange was observed. Further investigation revealed that the reaction temperature is a critical parameter for the reactivity, and the modified conditions can afford deuterated products with good to excellent deuterium incorporation.