Mechanistic investigations into the cyclopropanation of electron deficient alkenes with ethyl diazoacetate using [Co(MeTAA)]
Mechanistic investigations into the cyclopropanation of electron deficient alkenes with ethyl diazoacetate using [Co(MeTAA)]
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DOI：
10.1016/j.jcat.2018.02.013
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发表时间：
2018-05-01
影响因子：
7.3
通讯作者：
de Bruin, Bas
中科院分区：
文献类型：
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作者：
Chirila, Andrei;Brands, Maria B.;de Bruin, Bas
对缺电子烯烃（即丙烯酸甲酯与重氮乙酸乙酯（EDA）的环丙烷化反应）进行了详细的机理研究，旨在了解四甲基二苯并四氮杂钴[14]轮烯[Co(MeTAA)]催化剂与四苯基卟啉钴(II)[Co(TPP)]相比具有优异的活性和更高的灵敏度。通过结合动力学研究、实验性 EPR 自旋捕获实验和支持 DFT 研究，证明钴 (III)-卡宾自由基是反应中的关键中间体。通过观察 N-2 的形成并在等温条件下测量其分压来实时监测反应进程。使用反应进程动力学分析（RPKA）来分析实验数据。结果表明，该反应在[催化剂]和[EDA]中均为一级反应，在[丙烯酸甲酯]中为零级反应，与DFT计算的机理一致。计算出的反应速率决定步骤对应的活化参数与实验值一致，从而为所提出的金属自由基机理提供了强有力的支持。 (C) 2018 作者。由爱思唯尔公司出版
A detailed mechanistic study of the cyclopropanation of electron-deficient alkenes, namely methyl acrylate with ethyl diazoacetate (EDA), was carried out, aiming at understanding both the superior activity and the higher sensitivity of the cobalt(II) tetramethyldibenzotetraazal[14]annulene [Co(MeTAA)] catalyst as compared with cobalt(II) tetraphenylporphyrin [Co(TPP)]. Cobalt(lll)-carbene radicals were demonstrated to be present as key intermediates in the reaction, using a combination of kinetic studies, experimental EPR spin-trapping experiments, and supporting DFT studies. Reaction progress was monitored in real time by observing N-2 formation and measuring its partial pressure under isothermal conditions. Reaction progress kinetic analysis (RPKA) was used to analyze the experimental data. Results showed that the reaction is first-order in both [catalyst] and [EDA] and zero-order in [methyl acrylate], in agreement with the DFT-calculated mechanism. The calculated activation parameters corresponding to the rate-determining step of the reaction are in agreement with the experimental values, thus providing strong support for the proposed metalloradical mechanism. (C) 2018 The Authors. Published by Elsevier Inc.