In the presence of boron trifluoride diethyl etherate (BF3·OEt2), direct acylation of phenols with free carboxylic acid is chemoselective and regioselective and no demethylation, if any, was observed. The para-directing effect of BF3·OEt2 is attributed to the large steric hindrance of the boron trifluoride-phenolic hydroxyl group complex, which blocks the ortho-acylation from occurrence. Microwave irradiation could not change the regioselectivity of BF3·OEt2 except the reaction time being greatly shortened.
在
三氟化硼二
乙醚合物(
BF3·OEt2)的存在下,
酚类化合物直接与游离
羧酸酰化反应具有
化学选择性和区域选择性,并且没有观察到脱甲基化现象。 ·OEt2的导向效应归因于
硼三
氟化物-
酚羟基络合物的大位阻,这阻碍了邻位酰化的发生。微波照射不能改变 ·OEt2的区域选择性,除了反应时间大大缩短。