Anthracene–diacetylene cyclic dimers having two alkoxy groups (OMe, OEt, or OPr groups) at the intraannular positions were synthesized by dimerization of 1,8-diethynylanthracene precursors. For the OEt and OPr compounds, anti- and syn-stereoisomers that differed in the direction of the alkyl groups were separated by chromatography. Kinetic measurements showed that the barriers to isomerization from syn-isomer to anti-isomer were 124 and >146 kJ mol−1 for the OEt and OPr compounds, respectively. The molecular structures of these compounds were examined by X-ray analysis and DFT calculations. The preference for anti-isomers is attributable to the intramolecular C–H···O hydrogen bonds. The effects of substituents on the molecular structures and the barriers to isomerization are discussed.
通过对 1,8-二
乙炔蒽前驱物进行二聚化,合成了在环内位置具有两个烷氧基(OMe、OEt 或 OPr 基团)的
蒽-二
乙炔环状二聚体。对于 OEt 和 OPr 化合物,可通过色谱法分离出烷基方向不同的反立体异构体和同立体异构体。动力学测量结果表明,OEt 和 OPr 化合物从合成异构体到反异构体的异构化障碍分别为 124 kJ mol-1 和 >146 kJ mol-1。通过 X 射线分析和 DFT 计算研究了这些化合物的分子结构。反异构体的偏好归因于分子内的 C-H-O 氢键。本文讨论了取代基对分子结构的影响以及异构化的障碍。