Chen Xingshuo, Wei Zhenwei, Huang Kai-Hung, Uehling Mycah, Wleklinski Michael, Krska Shane, Makarov Alexey A, Nowak Timothy, Cooks R Graham
Chemistry Department, Purdue University, West Lafayette, IN 47907, USA.
Merck & Co. Inc., Kenilworth, NJ 07033, USA.
Chempluschem. 2022 Mar;87(3):e202100545. doi: 10.1002/cplu.202100545. Epub 2022 Jan 30.
Palladium-catalyzed Suzuki-Miyaura (SM) coupling is widely utilized in the construction of carbon-carbon bonds. In this study, nanoelectrospray ionization mass spectrometry (nanoESI-MS) is applied to simultaneously monitor precatalysts, catalytic intermediates, reagents, and products of the SM cross-coupling reaction of 3-Br-5-Ph-pyridine and phenylboronic acid. A set of Pd cluster ions related to the monoligated Pd (0) active catalyst is detected, and its deconvoluted isotopic distribution reveals contributions from two neutral molecules. One is assigned to the generally accepted Pd(0) active catalyst, seen in MS as the protonated molecule, while the other is tentatively assigned to an oxidized catalyst which was found to increase as the reaction proceeds. Oxidative stress testing of a synthetic model catalyst 1,5-cyclooctadiene Pd XPhos (COD-Pd-XPhos) performed using FeCl supported this assignment. The formation and conversion of the oxidative addition intermediate during the catalytic cycle was monitored to provide information on the progress of the transmetalation step.
钯催化的铃木-宫浦（SM）偶联反应在碳-碳键的构建中得到广泛应用。在本研究中，采用纳米电喷雾电离质谱（nanoESI-MS）同时监测3-溴-5-苯基吡啶与苯硼酸的SM交叉偶联反应的预催化剂、催化中间体、试剂和产物。检测到一组与单配位Pd(0)活性催化剂相关的钯簇离子，其去卷积同位素分布显示有两种中性分子的贡献。一种被指定为普遍认可的Pd(0)活性催化剂，在质谱中表现为质子化分子，而另一种被初步指定为氧化催化剂，发现其随着反应进行而增加。使用FeCl对合成模型催化剂1,5-环辛二烯钯XPhos（COD-Pd-XPhos）进行的氧化应激测试支持了这一指定。监测催化循环中氧化加成中间体的形成和转化，以提供有关转金属化步骤进展的信息。
