Restricted Rotation Involving the Tetrahedral Carbon. XIV. Conformational Equilibria and Attractive Interactions in Substituted 9-Benzyltriptycenes
作者:Fumio Suzuki、Michinori Oki
DOI:10.1246/bcsj.48.596
日期:1975.2
Several 9-benzyltriptycene derivatives were prepared by addition of benzynes to 9-benzylanthracenes. Rotation about the C9–Cbenzyl bond of compounds with a substituent at a peri-position to the benzyl group was found to be frozen at low temperatures on the NMR time scale but not at room temperature. In contrast, compounds with two substituents at two peri-positions to the benzyl group showed a frozen rotation about the C9–Cbenzyl bond at room temperature. Distribution of the conformers, as judged from the PMR intensities, showed preference to the dl-isomers in spite of the fact that they are the ones which are highly disfavored by steric effects. Interpretation of the phenomenon was based on the fact that attractive interactions, mainly charge-transfer type, exist between the substituted benzo group in the triptycene skeleton and the benzene ring in the benzyl group.
通过将苄基加到 9-苄基蒽中,制备了几种 9-苄基三联苯衍生物。在核磁共振时间尺度上发现,在低温下,苄基的一个周边位置上有一个取代基的化合物围绕 C9-Cbenzyl 键的旋转被冻结,而在室温下则没有。与此相反,在苄基的两个周边位置上有两个取代基的化合物在室温下显示出围绕 C9-Cbenzyl 键的冻结旋转。根据 PMR 强度判断,尽管 dl-异构体受立体效应的影响很大,但其构象的分布却偏向于 dl-异构体。对这一现象的解释是,三庚烯骨架中的取代苯并基和苄基中的苯环之间存在吸引力相互作用,主要是电荷转移类型的相互作用。