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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Metal-free catalysts for hydrogenation of both small and large imines: A computational experiment
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Metal-free catalysts for hydrogenation of both small and large imines: A computational experiment

机译：用于小亚胺和大亚胺加氢的无金属催化剂：计算实验

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This study extends our previous work of using π-FLP strategy to develop metal-free hydrogenation catalysts. Using small MeNCMe2 imine (im1) as a model, we previously designed cat1 and cat2 catalysts. But it is unclear whether they are capable of catalyzing the hydrogenations of bulky imines. Using tBuNC(H)Ph (im2) as a representative of large imines, we assessed the energetics of the cat1- and cat2-catalyzed im2 hydrogenations. The predicted energetics indicates that they can still catalyze large imine hydrogenations with experimentally accessible kinetic barriers, although the energetics becomes less favorable. To improve the catalysis, we proposed new catalysts (cat3 and cat4) by tailoring cat1 and cat2. The study indicates that cat3 and cat4 could have better performance for the hydrogenation of the bulky im2 than cat1 and cat2. Remarkably, cat3 and cat4 are also found suitable for small imine (im1) hydrogenation. Examining the hydrogen transfer substeps in the eight hydrogenations involved in this study, we observed that the mechanism for the hydrogen transfer step in the catalytic cycles depends on the steric effect between catalyst and substrate. The mechanism can be switched from stepwise one in the case of large steric effect (e.g.im2/cat2) to the concerted one in the case of small steric effect (e.g.im1/cat3). The new catalysts could be better targets for experimental realization because of their simpler constructions.
机译：这项研究扩展了我们以前使用π-FLP策略开发无金属氢化催化剂的工作。使用小型MeNCMe2亚胺（im1）作为模型，我们之前设计了cat1和cat2催化剂。但是尚不清楚它们是否能够催化大体积亚胺的氢化。使用tBuNC（H）Ph（im2）作为大型亚胺的代表，我们评估了cat1和cat2催化的im2氢化的能量。预测的能量学表明，尽管能量学变得不那么有利，但它们仍可以通过实验上可访问的动力学屏障催化大亚胺的氢化反应。为了改进催化作用，我们通过定制cat1和cat2提出了新的催化剂（cat3和cat4）。研究表明，cat3和cat4可能比cat1和cat2具有更好的氢化笨重im2的性能。值得注意的是，也发现cat3和cat4适用于小亚胺（im1）氢化。检查了这项研究涉及的八个加氢过程中的氢转移子步骤，我们观察到催化循环中氢转移步骤的机理取决于催化剂和底物之间的空间效应。该机制可以从空间效应较大（例如im2 / cat2）的逐步切换到空间效应较小（例如im1 / cat3）的协调的切换。新催化剂由于其结构简单，可能成为更好的实验目标。

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