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.
一种非常有用的方法被建立用于从各种
羧酸制备
羧酸酯和羧酰胺,采用了一种新型的缩合试剂——
吡啶-3-
羧酸酐(3-PCA),并在4-(
二甲氨基)
吡啶的激活下进行反应。各种
羧酸与亲核试剂(如醇或胺)的反应,在温和条件下通过简单的实验步骤,获得了相应的
羧酸酯或羧酰胺,产率良好到很高。此外,已确认该方法适用于克级合成,现场生成的副产物包括
吡啶-3-
羧酸和
吡啶-3-
羧酸盐(或
吡啶-3-羧酰胺)可以通过简单的
水洗步骤轻松去除。