Fluorine Labeling of ortho -Phenylenes to Facilitate Conformational Analysis
Fluorine Labeling of ortho -Phenylenes to Facilitate Conformational Analysis
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邻亚苯基的氟标记促进构象分析
DOI：
10.1021/acs.joc.1c01770
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Hartley, C. Scott
中科院分区：
文献类型：
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作者：
Kirinda, Viraj C.;Vemuri, Gopi Nath;Kress, Nicholas G.;Flynn, Kaitlyn M.;Kumarage, Nuwanthika Dilrukshi;Schrage, Briana R.;Tierney, David L.;Ziegler, Christopher J.;Hartley, C. Scott
1H核磁共振波谱是分析溶液中邻苯二甲酸酯构象的有力工具。然而，邻苯乙烯被集成到更复杂的系统中，我们正在达到基于1h和13c的核磁共振技术可以分析的极限。在这里，我们探索了邻苯低聚物的氟标记，用于19f核磁共振光谱分析。合成了两个系列的氟化低聚物。铃木偶联的单体优化使低聚物的高效逐步合成成为可能。通过1h核磁共振波谱和x射线晶体学确定，这些低聚物在溶液中都具有良好的折叠几何形状。19F核磁共振实验很好地补充了这些方法。一维19f {1H}光谱的分辨单重线对于确定相对的构象族是非常有用的。在进行1h分配时，来自二维19f核磁共振光谱的附加信息显然也是有价值的。然而，将19f各向同性屏蔽预测与实验化学位移进行比较，目前还不足以建立-苯基的几何结构。
1H NMR spectroscopy is a powerful tool for the conformational analysis ofortho-phenylene foldamers in solution. However, aso-phenylenes are integrated into ever more complex systems, we are reaching the limits of what can be analyzed by1H- and13C-based NMR techniques. Here, we explore fluorine labeling ofo-phenylene oligomers for analysis by19F NMR spectroscopy. Two series of fluorinated oligomers have been synthesized. Optimization of monomers for Suzuki coupling enables an efficient stepwise oligomer synthesis. The oligomers all adopt well-folded geometries in solution, as determined by1H NMR spectroscopy and X-ray crystallography.19F NMR experiments complement these methods well. The resolved singlets of one-dimensional19F{1H} spectra are very useful for determining relative conformer populations. The additional information from two-dimensional19F NMR spectra is also clearly valuable when making1H assignments. The comparison of19F isotropic shielding predictions to experimental chemical shifts is not, however, currently sufficientby itselfto establisho-phenylene geometries.