Conformational states of the cyclohexanone ring were established for 3R-methyl-6-(4-phenylbenzylidene)cyclohexanone and several 2,6-bis(4-X-benzylidene)-3R-methylcyclohexanones (X = Br, OCOCH3 and C6H5) by 1H NMR spectroscopy combined with molecular simulation using the semi-empirical methods AM1 and PM3. The first compound studied contains only one arylidene group, and exists predominantly in a chair conformation of the cyclohexanone ring with an equatorial orientation of the methyl substituent in C6D6 and CDCl3 solutions at room temperature (22–23 °C). In contrast, the 2,6-bis(arylidene) derivatives of 3R-methylcyclohexanone preferentially adopt conformations with an axially oriented methyl group. The extent of twisting of enone fragments was also characterized for the compounds studied based on simulation results and comparison of chemical shifts for the arylidene protons of appropriate model compounds. Copyright © 2003 John Wiley & Sons, Ltd.
                                    通过1H NMR光谱结合使用半经验方法
AM1和PM3的分子模拟,确定了3R-甲基-6-(4-苯基苄亚基)
环己酮和几种2,6-双(4-X-苄亚基)-3R-甲基
环己酮(X = Br、OCOCH3和
C6H5)的
环己酮环构象状态。 首先研究的化合物只含有一个芳基亚基,在室温(22-23°C)下,在C6D6和CDCl3溶液中主要呈
环己酮环的椅构象,甲基取代基呈赤道取向。 相比之下,3R-甲基
环己酮的2,6-双(芳基亚基)衍
生物倾向于采用甲基呈轴向取向的构象。 还根据模拟结果和适当模型化合物芳基亚基质子的
化学位移比较,对所研究化合物的烯酮片段扭曲程度进行了表征。 版权所有 © 2003 John Wiley & Sons, Ltd.