Recently, planar‐chiral phosphine‐olefin ligands based on (η6‐arene)chromium(0) and (η5‐cyclopentadienyl)manganese(I), which are known as first‐ and second‐generation, respectively, have been developed. These ligands were employed for Rh‐catalyzed asymmetric 1,4‐addition to enones. First‐generation ligands involve high enantioselectivity for cyclic enones (>98% ee). Second‐generation ligands involve high enantioselectivity for not only cyclic enones but also for acyclic enones (>98% ee). In this study, we have performed DFT calculations to investigate the origin of enantioselectivity. The theoretical values of enantioselectivities were found to be in good agreement with the experimental values obtained for a cyclic enone, 2‐cyclopenten‐1‐one, using both the first‐ and second‐generation ligands. Regarding an acyclic enone, 3‐penten‐2‐one, it was found that the s‐cis type decreases the enantioselectivity because the transition states in the s‐cis type have a large steric repulsion. Energy decomposition analysis (EDA) and natural bond orbital (NBO) analysis indicate that it is important to study the orbital interactions in the transition states of the insertion step for the acyclic enone attacked from si‐face with the second‐generation ligand. © 2018 Wiley Periodicals, Inc.

中文翻译：

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使用平面手性膦烯烃配体对 Rh 催化的烯酮不对称 1,4-加成的理论研究

最近，已经开发了基于（η6-芳烃）铬（0）和（η5-环戊二烯基）锰（I）的平面手性膦-烯烃配体，它们分别被称为第一代和第二代。这些配体用于 Rh 催化的烯酮不对称 1,4-加成。第一代配体对环烯酮具有高对映选择性（>98% ee）。第二代配体不仅对环烯酮具有高对映选择性，而且对非环烯酮 (>98% ee) 也具有高对映选择性。在这项研究中，我们进行了 DFT 计算以研究对映选择性的起源。发现对映选择性的理论值与使用第一代和第二代配体获得的环烯酮、2-环戊烯-1-one 的实验值非常一致。关于无环烯酮，3-penten-2-one，发现 s-cis 型降低了对映选择性，因为 s-cis 型中的过渡态具有大的空间排斥。能量分解分析 (EDA) 和自然键轨道 (NBO) 分析表明，重要的是研究从 si-face 与第二代配体攻击的无环烯酮插入步骤过渡态中的轨道相互作用。© 2018 Wiley Periodicals, Inc.