The reaction mechanism of the Aza–Diels–Alder (A–D–A) cycloaddition reaction between X₂C═NNH₂, where X = H, F, Cl, Br, and 1,3-butadiene catalyzed by a PHCl₂ Lewis acid was characterized using density functional theory calculations. The influences of various substituents of X on the studied reaction were analyzed using the activation strain model (ASM), which is also termed as the distortion–interaction model. Calculations showed that the smallest and largest values of the activation energies belong to the substituents of F and Br, respectively. The activation energy of the studied reactions was decreased within 8.6 kcal·mol^–1 in the presence of PHCl₂ catalyst. Investigations showed that the pnicogen bonding is adequately capable of activating the A–D–A reaction. The quantum theory of atoms in molecules (QTAIM) and natural bond orbital (NBO) analysis were implemented to understand the nature of C_4,Cbut···C_XIm and C_1,Cbut···N_XIm bonds at the TS structures. Additionally, the energy decomposition analysis (EDA) based on the ETS-NOCV scheme was used to characterize the nature of C_4,Cbut···C_XIm and C_1,Cbut···N_XIm bond. The results of the study mirror the fact that the PHCl₂ Lewis acid may be suggested as a simple suitable catalyst for experimental studies on the A–D–A reactions.

中文翻译：

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PHCl ₂路易斯酸与微囊原键合催化Aza-Diels-Alder反应的理论研究

所述的反应机理氮杂狄尔斯-阿尔德（A-d-A）X之间环加成反应₂ C═NNH ₂，其中X = H，F，氯，溴，和1,3-丁二烯通过PHCl催化₂路易斯使用密度泛函理论计算对酸进行了表征。使用活化应变模型（ASM）分析了X的各种取代基对所研究反应的影响，该模型也称为变形相互作用模型。计算表明，活化能的最小值和最大值分别属于F和Br的取代基。在PHCl ₂存在下，所研究反应的活化能在8.6 kcal·mol ^–1范围内降低。催化剂。研究表明，成药原键足以激活A–D–A反应。在分子（QTAIM）和自然键轨道（NBO）分析原子的量子理论得到执行了解C的性质_4，Cbut ...Ç _XIM和C _1，Cbut ...Ñ _XIM在TS结构键。此外，基于ETS-NOCV方案的能量分解分析（EDA）用于表征C _4，Cbut ···C _XIm和C _1，Cbut ···N _XIm键的性质。研究结果反映了PHCl ₂ 路易斯酸可能被建议作为A–D–A反应实验研究的简单合适催化剂。