Diels-Alder Reactivity of a Chiral Anthracene Template with Symmetrical and Unsymmetrical Dienophiles: A DFT Study.,ChemistryOpen

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Diels-Alder Reactivity of a Chiral Anthracene Template with Symmetrical and Unsymmetrical Dienophiles: A DFT Study.
ChemistryOpen ( IF 2.5 ) Pub Date : 2020-07-10 , DOI: 10.1002/open.202000137
Jennifer P Hernández-Mancera ₁ , Francisco Núñez-Zarur ₂ , Ricardo Vivas-Reyes _{1,

3}

Affiliation

In this work, we used Density Functional Theory calculations to assess the factors that control the reactivity of a chiral anthracene template with three sets of dienophiles including maleic anhydrides, maleimides and acetoxy lactones in the context of Diels‐Alder cycloadditions. The results obtained here (at the M06‐2X/6‐311++G(d,p) level of theory) suggest that the activation energies for maleic anhydrides and acetoxy lactones are dependent on the nature of the substituent in the dienophile. Among all studied substituents, only −CN reduces the energy barrier of the cycloaddition. For maleimides, the activation energies are independent of the heteroatom of the dienophile and the R group attached to it. The analysis of frontier molecular orbitals, charge transfer and the activation strain model (at the M06‐2X/TZVP level based on M06‐2X/6‐311++G(d,p) geometries) suggest that the activation energies in maleic anhydrides are mainly controlled by the amount of charge transfer from the diene to the dienophile during cycloaddition. For maleimides, there is a dual control of interaction and strain energies on the activation energies, whereas for the acetoxy lactones the activation energies seem to be controlled by the degree of template distortion at the transition state. Finally, calculations show that considering a catalyst on the studied cycloadditions changes the reaction mechanism from concerted to stepwise and proceed with much lower activation energies.

中文翻译：

手性蒽模板与对称和不对称亲双烯体的 Diels-Alder 反应性：一项 DFT 研究。

在这项工作中，我们使用密度泛函理论计算来评估在狄尔斯-阿尔德环加成背景下控制手性蒽模板与三组亲双烯体（包括马来酸酐、马来酰亚胺和乙酰氧基内酯）反应性的因素。这里获得的结果（在 M06-2X/6-311++G( d,p ) 理论水平）表明马来酸酐和乙酰氧基内酯的活化能取决于亲二烯体中取代基的性质。在所有研究的取代基中，只有 -CN 降低了环加成的能垒。对于马来酰亚胺，活化能与亲二烯体的杂原子和与其相连的 R 基团无关。对前沿分子轨道、电荷转移和活化应变模型（基于 M06-2X/6-311++G( d,p ) 几何结构的 M06-2X/TZVP 水平）的分析表明，马来酸酐中的活化能主要受环加成过程中从二烯到亲二烯体的电荷转移量控制。对于马来酰亚胺，活化能存在相互作用和应变能的双重控制，而对于乙酰氧基内酯，活化能似乎由过渡态模板畸变程度控制。最后，计算表明，在所研究的环加成中考虑催化剂将反应机理从协同变为逐步，并且以低得多的活化能进行。

更新日期：2020-07-10

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