In the present work, a molecular electron density theory (MEDT) study is carried out to shed light on the regio- and stereochemistry in two Diels–Alder (DA) reactions explored experimentally by Lemos and coworkers. These reactions involve the aza-Diels–Alder (ADA) reaction of an azoalkene AA with both furan FU and dihydrofuran DHFU in the presence of dichloromethane at room temperature. The regiochemistry of the obtained cycloadducts is completely opposite in the considered ADA reactions. The results of the local reactivity indices analysis based on the Parr functions confirmed the regiochemistry experimentally observed. Exploration of potential energy surfaces (PESs) indicated that the formation of endo adducts, P-1n and P DH -2n , are more favorable than exo ones. It was found that the electrostatic as well as the stabilizing π···π stacking interactions between two interacting fragments in the transition states associated with the endo attack can be considered as the origin of the endo stereochemistry predominance.

中文翻译：

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偶氮烯烃与呋喃和 2,3-二氢呋喃的 aza-Diels-Alder 反应中的区域和立体化学：分子电子密度理论研究

在目前的工作中，进行了分子电子密度理论 (MEDT) 研究，以阐明 Lemos 及其同事通过实验探索的两个 Diels-Alder (DA) 反应中的区域和立体化学。这些反应包括偶氮烯烃 AA 与呋喃 FU 和二氢呋喃 DHFU 在二氯甲烷存在下在室温下发生的氮杂-狄尔斯-阿尔德 (ADA) 反应。所获得的环加合物的区域化学与所考虑的 ADA 反应完全相反。基于帕尔函数的局部反应性指数分析结果证实了实验观察到的区域化学。对势能面 (PES) 的探索表明，内加合物 P-1n 和 P DH -2n 的形成比外加物更有利。