A versatile, practical, and inexpensive reagent, pyridine-3-carboxylic anhydride (3-PCA), for condensation reactions

A highly useful method for the preparation of carboxylic esters and carboxamides from various carboxylic acids was established by using a novel condensing reagent, pyridine-3-carboxylic anhydride (3-PCA), in the presence of 4(dimethylamino)pyridine as an activator. The reactions of various carboxylic acids with nucleophiles, such as alcohols or amines, afforded the corresponding carboxylic acids or carboxamides in good to high yields under mild conditions by using simple experimental procedure. In addition, it was confirmed that this protocol was applicable to a gram-scale synthesis and the by-products, including pyridine-3-carboxylic acid and pyridine-3-carboxylate (or pyridine-3-carboxamide) produced in situ, were easily removed by using a simple aqueous workup.