The ring-opening reaction of fluorinated oxetanes by halides, including alkylidene oxetanes and spirocyclic oxetanes, was highly stereoselective and directed by the presence of a fluorine atom. This reaction allowed a stereoselective preparation of tetrasubstituted alkenes and substituted pyrrolidines containing all-carbon quaternary centers. Theoretical calculations were performed to shed light on experimentally observed regioselectivity in the opening of oxetane derivatives. Transition state calculations were carried out to compare the energy of transition states responsible for forming different diastereoisomers. These calculations were performed using several DFT functionals and benchmarked to DLPNO–CCSD(T)/def2-TZVP calculations. Intrinsic reaction coordinated (IRC) calculations were run to confirm if the found transition states connect reactants and products. The IRC paths were then decomposed into the electrostatic, steric hyperconjugative contributions to reaction barriers by using the natural bond orbital (NBO) analysis. The destabilizing F^δ−···Br^– electrostatic interaction directs the reaction pathway.

中文翻译：

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α-氟化氧杂烷的立体选择性开环反应：实践和理论研究


卤化物（包括烷基氧杂烷和螺环氧杂烷）对氟化氧杂烷的开环反应是高度立体选择性的，并且受氟原子的存在引导。该反应允许立体选择性制备含有全碳季铵中心的四取代烯烃和取代吡咯烷。进行理论计算以阐明实验观察到的氧杂环丁烷衍生物开口的区域选择性。进行过渡态计算以比较负责形成不同非对映异构体的过渡态的能量。这些计算是使用几个 DFT 泛函进行的，并以 DLPNO-CCSD（T）/def2-TZVP 计算为基准。运行本征反应协调 （IRC） 计算以确认发现的过渡态是否连接反应物和生成物。然后通过使用天然键轨道 （NBO） 分析，将 IRC 路径分解为对反应势垒的静电空间高共轭贡献。不稳定的 F^δ−···Br^– 静电相互作用指导反应途径。