Conformational Studies by Dynamic NMR. 97.<sup>1</sup> Structure, Conformation, Stereodynamics and Enantioseparation of Aryl Substituted Norbornanes
作者:Daniele Casarini、Stefano Grilli、Lodovico Lunazzi、Andrea Mazzanti
DOI:10.1021/jo035411n
日期:2004.1.1
predicted by molecular mechanics calculations. Restricted rotation of the aryl groups also has been observed by dynamic NMR spectroscopy in this compound and in a number of analogously substituted norbornanes. The aryl−norbornane bond rotation barriers were measured by line shape analysis of the 13C NMR spectra obtained at temperatures lower than −100 °C and were found to cover the range 6.0 to 7.9 kcal mol-1
1,7,7-三芳基降冰片烷(化合物3)的结构已通过X射线衍射确定,发现与分子力学计算所预测的基本相同。通过动态NMR光谱在该化合物和许多类似取代的降冰片烷中也观察到芳基的旋转受限。芳基-降冰片烷键旋转势垒是通过在低于-100°C的温度下获得的13 C NMR光谱进行线形分析而测得的,其覆盖范围为6.0至7.9 kcal mol - 1。化合物5中涉及邻茴香基的旋转是一个例外由于相应的势垒要高得多(14.4 kcal mol - 1),因此会在环境温度附近发生。在一种情况下(化合物4),可以通过手性HPLC分离构型对映异构体,并记录相应的CD光谱。