Computationally Assisted Mechanistic Investigation into Hypervalent Iodine Catalysis: Cyclization of N-Allylbenzamide
Computationally Assisted Mechanistic Investigation into Hypervalent Iodine Catalysis: Cyclization of N-Allylbenzamide
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DOI：
10.1021/acs.joc.9b02623
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发表时间：
2019-12-06
影响因子：
3.6
通讯作者：
Moran, Wesley J.
中科院分区：
文献类型：
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作者：
Butt, Smaher E.;Das, Mirdyul;Moran, Wesley J.
前人的实验工作表明，2-碘苯甲醚是N-烯基酰胺氧化环化合成2-恶唑啉的最佳预催化剂。在这里，我们介绍了我们的研究结果对反应速度的影响，基于结构的碘代芳烃预催化剂。我们还基于密度泛函理论模型揭示了环化反应的机理，得到了不同碘代芳烃的观测反应速率与计算得到的活化能之间的明显关联。此外，限速步骤是底物的环化反应，即碘代芳烃预催化剂的浓度为零级。环化的速度与碘代芳烃的氧化程度有关；然而，最容易被氧化的碘代芳烃生成的碘(III)物种容易分解。最后，环化中间体中碘芳烃的损失可以通过配体偶联或S(N)2置换(还原消除)进行，这是底物依赖的。
Previous experimental work identified 2-iodoanisole as the best precatalyst for the oxidative cyclization of N-alkenylamides into 2-oxazolines. Herein, we describe our investigation into the effect on the reaction rate based on the structure of the iodoarene precatalyst. We also reveal the mechanism of the cyclization based on DFT modeling and obtain a clear correlation between observed reaction rates and computationally derived activation energies for different iodoarenes. In addition, the rate-limiting step is shown to be the cyclization of the substrate that is zero order in the concentration of the iodoarene precatalyst. The rate of cyclization is found to correlate with the ease of oxidation of the iodoarene; however, the most easily oxidized iodoarenes generate iodine(III) species that decompose readily. Finally, loss of iodoarene from the cyclized intermediate can proceed by either ligand-coupling or S(N)2 displacement (reductive elimination), and this is shown to be substrate-dependent.