Casarini Daniele, Grilli Stefano, Lunazzi Lodovico, Mazzanti Andrea
Department of Chemistry, University of Basilicata, Potenza, Italy.
J Org Chem. 2004 Jan 23;69(2):345-51. doi: 10.1021/jo035411n.
The structure of a 1,7,7-triaryl norbornane (compound 3) has been determined by X-ray diffraction and was found essentially equal to that 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 (13)C NMR spectra obtained at temperatures lower than -100 degrees C and were found to cover the range 6.0 to 7.9 kcal mol(-1). An exception was the rotation involving the o-anisyl group in compound 5, which occurs near ambient temperature since the corresponding barrier is much higher (14.4 kcal mol(-1)). In one case (compound 4) configurational enantiomers could be separated by chiral HPLC and the corresponding CD spectra recorded.
通过X射线衍射确定了1,7,7-三芳基降冰片烷（化合物3）的结构，发现其与分子力学计算预测的结构基本相同。在该化合物以及许多类似取代的降冰片烷中，通过动态核磁共振光谱也观察到芳基的受限旋转。通过对在低于-100℃的温度下获得的(13)C NMR光谱进行线形分析，测量了芳基-降冰片烷键的旋转势垒，发现其范围为6.0至7.9 kcal mol(-1)。化合物5中涉及邻甲氧基苯基的旋转是个例外，由于相应的势垒高得多（14.4 kcal mol(-1)），该旋转在接近室温时发生。在一种情况下（化合物4），构型对映体可以通过手性高效液相色谱分离，并记录相应的圆二色光谱。
