Gara Rayene, Zouaghi Mohamed Oussama, ALshandoudi Laila Mohammed Humaid, Arfaoui Youssef
Department of Chemistry, Laboratory of Characterizations, Applications and Modeling of Materials LR18ES08, University of Tunis El Manar, Tunis, Tunisia.
Department of Science, College of Education, University of Technology & Applied Sciences Rustaq, P.O. Box: 10, 329, Rustaq, Oman.
J Mol Model. 2021 Apr 7;27(5):125. doi: 10.1007/s00894-021-04729-w.
In this study, we report on a DFT investigation of two intramolecular Diels-Alder furan reactions. Optimizations of the studied structures, TS and IRC calculations, were carried out at B3LYP/6-31G(d) level. We have studied the effect of substituent, solvent and Lewis acid catalyst on cyclization-retrocyclization equilibria, activation energies, and stability of the desired products. The analysis of orbital coefficients, IRC curves, and Wiberg indices have proved that both reactions are under orbital control. We have found that for the reaction I (2↔4 + 5), where R = H, the exo attack is favored by hydrogen bond interaction, while for R = t-Bu, the steric hindrance leads to the endo attack. For the reaction II (3 → 6 + 7), the t-Bu-substituted products are the most stable ones. At another level, we have found that it is recommended to use polar organic solvents as DMSO with Lewis acid catalyst BF. The latest leads to accelerate the reaction II with stabilization of the desired products.
在本研究中，我们报告了对两个分子内狄尔斯-阿尔德呋喃反应的密度泛函理论（DFT）研究。在所研究结构的优化、过渡态（TS）和内禀反应坐标（IRC）计算方面，是在B3LYP/6-31G(d)水平上进行的。我们研究了取代基、溶剂和路易斯酸催化剂对环化-逆环化平衡、活化能以及所需产物稳定性的影响。轨道系数分析、IRC曲线和维伯格指数已证明这两个反应均受轨道控制。我们发现，对于反应I（2↔4 + 5），当R = H时，外型进攻因氢键相互作用而更有利，而当R =叔丁基（t-Bu）时，空间位阻导致内型进攻。对于反应II（3 → 6 + 7），叔丁基取代的产物是最稳定的。在另一个层面上，我们发现建议使用极性有机溶剂如二甲基亚砜（DMSO）并搭配路易斯酸催化剂BF。后者能加速反应II并使所需产物稳定。
