Conformational Studies by Dynamic NMR. 89.<sup>1</sup> Stereomutation and Cryogenic Enantioseparation of Conformational Antipodes of Hindered Aryl Oximes
作者:Francesco Gasparrini、Stefano Grilli、Rino Leardini、Lodovico Lunazzi、Andrea Mazzanti、Daniele Nanni、Marco Pierini、Marco Pinamonti
DOI:10.1021/jo0255431
日期:2002.5.1
Aryl benzyl oximes having the configuration Z give rise to stereolabile atropisomers when a halogen atom is present in the ortho position of the aryl moiety, as a consequence of the restricted aryl-CN bond rotation. By means of dynamic (1)H NMR spectroscopy it has been possible to determine the corresponding rotation barrier, hence the lifetime of the atropisomers that, in the case of the iodine derivative
当由于芳基-CN键旋转受限而在芳基部分的邻位存在卤素原子时,具有Z构型的芳基苄基肟产生立体不稳定的阻转异构体。借助动态(1)H NMR光谱,可以确定相应的旋转势垒,因此,对于碘衍生物而言,阻转异构体的寿命足够长,可以实现物理分离。在适当冷却的对映选择性HPLC柱上。通过动态NMR和动态HPLC测定的势垒的比较证明了这两种技术的等效性。当碘原子被α-萘基取代时,观察到两个动态过程。可以通过NMR来确定较低的势垒,而通过HPLC可以确定较高的势垒,