Kinetic and Spectroscopic Studies of Aerobic Copper(II)-Catalyzed Methoxylation of Arylboronic Esters and Insights into Aryl Transmetalation to Copper(II)
作者:Amanda E. King、Bradford L. Ryland、Thomas C. Brunold、Shannon S. Stahl
DOI:10.1021/om300586p
日期:2012.11.26
the CuII catalyst resting state(s). EPR spectroscopic studies show that at least two copper(II) species are present under catalytic conditions, and their relative populations vary as a function of reaction time and acidity of the arylboronic ester and are influenced by addition of acetic acid or acetate to the reaction mixture. Analysis of kinetic data and 11B NMR and EPR spectra under diverse reaction
我们之前报道了有氧 Cu(OAc) 2催化的 4-甲苯基硼酸酯甲氧基化的初步机理研究(King 等人J. Am. Chem. Soc. , 2009 , 131 , 5044–5045),揭示了芳基转移从硼酸酯到 Cu II是转换限制步骤。在本研究中,更彻底的动力学和光谱研究为铜II的金属转移途径和特性提供了额外的见解催化剂静止状态。EPR 光谱研究表明,在催化条件下至少存在两种铜 (II) 物质,它们的相对数量随反应时间和芳基硼酸酯的酸度而变化,并受向反应混合物中添加乙酸或乙酸盐的影响. 对不同反应条件下的动力学数据和11 B NMR 和 EPR 光谱的分析表明,芳基金属转移是从四配位阴离子硼酸盐到阳离子 Cu II物质发生的,由甲醇桥介导。