Synthetic Organic Chemistry Laboratory, RIKEN Cluster for Pioneering Research.
Catalysis and Integrated Research Group, RIKEN Center for Sustainable Resource Science.
Chem Pharm Bull (Tokyo). 2022;70(9):616-623. doi: 10.1248/cpb.c22-00041.
Controlling catalytic asymmetric space has received increasing attention for the on-demand synthesis of chiral molecules of interest. However, the identification of the key parameters controlling the stereo-determining step in transition metal catalysis is challenging and involves the thorough characterization of the rate- and stereo-determining transition state(s). In this paper, we describe the computational analysis of the (3 + 2) cycloaddition of Ni(II)-enolate with cyclic (E)-nitrone to provide a comprehensive analysis of how the bond-forming processes are regulated in the two-electron manifold in the triplet state. Our molecular orbital analysis, in particular, reveals the occurrence of the singly occupied molecular orbital-highest occupied molecular orbital (SOMO-HOMO) level inversion in the Ni(II)-enolate. Further, distortion and interaction analysis are also used to explain the substrate-dependent diastereodivergence in this reaction by alternating the structure of the nitrone. Using a range of computational analyses, we show that the rate- and stereo-determining step in the (3 + 2) cycloaddition of (E)-nitrone is regulated integrally by (1) isomerism of the octahedral Ni(II) complex, (2) E/Z isomerism of the Ni(II)-enolate, and (3) steric repulsion between the reactants and ligand.
控制催化不对称空间已受到越来越多的关注，以按需合成有兴趣的手性分子。然而，确定控制过渡金属催化中立体决定步骤的关键参数具有挑战性，并且涉及对速率和立体决定过渡态的彻底表征。在本文中，我们描述了 Ni(II)-烯醇盐与环状（E）-亚硝酮的（3 + 2）环加成的计算分析，为如何在三重态中的双电子组态中调节成键过程提供了全面的分析。特别是我们的分子轨道分析揭示了 Ni(II)-烯醇盐中单占据分子轨道-最高占据分子轨道（SOMO-HOMO）能级反转的发生。此外，通过交替亚硝酮的结构，还使用扭曲和相互作用分析来解释该反应中底物依赖性的非对映选择性发散。通过一系列计算分析，我们表明（E）-亚硝酮的（3 + 2）环加成的速率和立体决定步骤是由（1）八面体 Ni(II)配合物的异构体，（2）Ni(II)-烯醇盐的 E/Z 异构体，以及（3）反应物和配体之间的空间位阻整体调节的。
