Stereoelectronic Effect in the Reaction of α-Methylene Lactones with Tertiary Phosphines and Its Application in Organocatalysis
作者:Alexey V. Salin、Andrey A. Shabanov、Khasan R. Khayarov、Ramil I. Nugmanov、Daut R. Islamov
DOI:10.1021/acs.joc.3c01223
日期:2023.8.18
acceleration. The observed reactivities were rationalized by DFT calculations at the RwB97XD/6-31+G(d,p) level of theory, showing that the intramolecular interaction between phosphonium and enolate oxygen centers provided by the locked s-cis-geometry of the heterocycles plays an important role in the stabilization of intermediate zwitterions. The reactivity is also controlled by the conformational flexibility
动力学数据表明,与相关开链酯的反应相比,叔膦与乙酸中的α-亚甲基内酯的加成反应大大加速。六元α-亚甲基-δ-戊内酯比五元α-亚甲基-γ-丁内酯表现出更显着的速率增加。使用α-亚甲基-γ-丁内酰胺作为α-亚甲基-γ-丁内酯的氮类似物导致反应加速完全丧失。观察到的反应性通过 RwB97XD/6-31+G(d,p) 理论水平的 DFT 计算合理化,表明由杂环锁定的顺式几何结构提供的磷鎓和烯醇氧中心之间的分子内相互作用在中间两性离子的稳定中发挥重要作用。反应性还受杂环的构象灵活性控制。五元内酯环,特别是六元内酯环的几何形状在膦的亲核攻击下发生轻微变化,通过π·Ο相互作用产生稳定的立体电子效应。α-亚甲基-γ-丁内酰胺中添加膦显着扭曲了杂环的初始几何形状,使得亲核攻击变得不利。论证了应用立体电子效应来提高膦催化的 α-亚甲基内酯的 Michael 和 Pudovik 反应的效率。