Abstract

[3 + 2] cycloaddition (32CA) reaction of C,N-diaryl nitrone with benzylidene acetone has been studied to analyse the mechanism, selectivity and polar character of this nitrone-enone cycloaddition. Topological analysis of the electron localization function (ELF) shows the absence of pseudoradical and carbenoid centre in the nitrone, which allows its classification as a zwitter-ionic (zw) type three atom component (TAC) and hence participation in zw- type cycloadditions is associated with high activation energy barriers. This 32CA reaction follows a one-step mechanism with asynchronous TSs. Endo/meta product is obtained as the major cycloadduct experimentally, which can be rationalized from its calculated lowest activation energy among the four possible reaction pathways. Global electron density transfer (GEDT) at the TSs predict the non-polar character of this 32CA reaction. Topological analysis of the ELF and QTAIM parameters was performed at the TSs. Finally, non-covalent interaction (NCI) gradient isosurfaces are computed to obtain a visualization of non-covalent interactions at the interatomic bonding regions.

Graphic Abstract

The experimental and theoretical aspects of [3+2] cycloaddition reactions of C,N-diaryl nitrone with benzylidene acetone is described. The reaction is meta/endo selective and follows one step mechanism with non-covalent interactions. The C-C and C-O bonds are generated through coupling of pseudoradical centers.

中文翻译：

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分子电子密度理论研究，以了解理论与实验在硝酮-烯酮环加成中的相互作用

摘要

研究了C，N-二芳基硝酮与亚苄基丙酮的[3 + 2]环加成反应（32CA），以分析该硝酮-烯酮环加成反应的机理，选择性和极性特征。电子定位功能（ELF）拓扑分析显示不存在的pseudoradical在硝酮，这允许其分类为两性离子（和卡宾中心ZW）键入在三个原子组分（TAC），并因此参与zw-型环加成被与高活化能垒有关。此32CA反应遵循具有异步TS的一步机制。远藤/元实验所得产物为主要的环加合物，可从其在四种可能的反应途径中计算出的最低活化能来合理化。TS处的全局电子密度转移（GEDT）预测了此32CA反应的非极性特征。在TS处对ELF和QTAIM参数进行了拓扑分析。最后，计算非共价相互作用（NCI）梯度等值面，以获得在原子间键合区域非共价相互作用的可视化。

图形摘要

描述了C，N-二芳基硝酮与亚苄基丙酮的[3 + 2]环加成反应的实验和理论方面。该反应是间位/内位选择性的，并且遵循具有非共价相互作用的一步机理。CC和CO键是通过伪自由基中心的耦合生成的。