铜催化二氟乙醇的芳基醚化反应及其机理研究

Copper-Catalyzed Arylated Etherification of 2,2-Difluoroethanol and Its Mechanistic Study

有机氟硅化合物是元素有机化学中最重要的高端产品种类之一,极具研究价值.开发了含二氟乙醇农药的新工艺技术,发展了一种条件温和和高效的铜催化二氟乙醇芳基醚化反应,通过大量的配体筛选和条件优化,建立了二氟乙醇和芳基溴或芳基碘的C—O偶联反应,简易合成出各种芳基取代的二氟乙基芳基醚.该反应以CuI为催化剂,在8-羟基喹啉和叔丁醇钾存在下顺利进行,具有广泛的底物适用性.ESI-MS分析证明,该催化过程可能存在三价铜催化机制,密度泛函理论(DFT)计算进一步表明该反应机理可能涉及三价铜的氧化加成、亲核取代及还原消除过程.

Both organofluorine and organosilicon compounds are one of the most important types of high-tech product in elementorganic chemistry,and have been received much attetions in the past decades.Considering the imporatance of difluoroethanol moeity in pesticides,the development of a mild and efficient copper-catalyzed arylated etherification reaction of difluoroethanol is highly desirable.Herein,a mild and efficient method for the preparation of difluoroethyl aryl ethers was developed by the copper-catalyzed Ullmann-type arylated etherification reaction of aryl bromides or iodides with 2,2-difluoroethanol.This reaction proceeds smoothly in the presence of CuI and 8-hydroxyquinoline/t-BuOK,and has a broad substrate scope.ESI-MS analysis supported the existence of LCu(III)Ar(OR)species during this catalytic reaction.Further density functional theory(DFT)calculations suggest a proposed mechanism of arylated etherification reaction involving oxidative addition,followed by nucleophile substitution and reductive elimination would be rational.