Dynamic Intermediates in the Radical Cation Diels-Alder Cycloaddition: Lifetime and Suprafacial Stereoselectivity.
Dynamic Intermediates in the Radical Cation Diels-Alder Cycloaddition: Lifetime and Suprafacial Stereoselectivity.
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自由基阳离子第尔斯-阿尔德环加成反应中的动态中间体：寿命和表面立体选择性。
DOI：
10.1021/acs.orglett.8b00737
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发表时间：
2018
期刊：
影响因子：
5.2
通讯作者：
Robert S Paton
中科院分区：
文献类型：
--
作者：
Jacqueline S J Tan;Viivi H. A. Hirvonen;Robert S Paton
阳离子自由基Diels-Alder环加成反应通过存在于势能面平坦区域的无环中间体进行。环化和C-C键旋转之间的竞争导致不同程度的超表面立体选择性。准经典轨迹被用来探索在这个表面上的反应动力学。即使有没有明显的能量障碍对环化，一个动态的逐步过程中发现，其中的无环中间体被发现驻留数百飞秒。在少数情况下，发现寿命特别长（>1000 fs），导致烯烃立体化学的损失。
Cation radical Diels-Alder cycloadditions proceed via an acyclic intermediate that exists on a flat region of the potential energy surface. Competition between cyclization and C-C bond rotation results in varying levels of suprafacial stereoselectivity. Quasi-classical trajectories were used to explore reaction dynamics on this surface. Even though there is no discernible energy barrier toward cyclization, a dynamically stepwise process is found, for which the acyclic intermediate is found to reside for several hundreds of femtoseconds. In a small number of cases, exceptionally long lifetimes (>1000 fs) are found, leading to a loss of alkene stereochemistry.