Rotational Isomerism Involving an Acetylenic Carbon: Synthesis of and Barrier to Rotation around C(sp)-C(sp<sup>3</sup>) Bonds in Bis(1,4-disubstituted 9-triptycyl)ethynes
作者:Shinji Toyota、Takao Yamamori、Mitsuhiro Asakura、Michinori Oki
DOI:10.1246/bcsj.73.205
日期:2000.1
compounds. The rotational barriers are in the range of 9—15 kcal mol-1, and are enhanced as the steric size of the substituents is increased (H < OMe < Me). This substituent effect is attributed to the destabilization of the transition state of the rotation process, where the two triptycyl groups are almost eclipsed about the central axis, by the steric interactions between the peri substituents. The acetylenic
对于在 9-三苯乙烯基团的 1,4-位上带有 Me 或 OMe 取代基的标题化合物,研究了取代基对炔烃到四面体 CC 键的旋转势垒的影响。这些化合物是通过使用 Diels-Alder 和 Sonogashira 反应从 9-乙炔蒽衍生物制备的。动力学参数通过对五种化合物的变温 1 H NMR 观察到的信号进行总线形分析来确定。旋转势垒在 9-15 kcal mol-1 的范围内,并且随着取代基空间尺寸的增加而增强(H < OMe < Me)。这种取代基效应归因于旋转过程过渡态的不稳定,其中两个三苯乙烯基几乎围绕中心轴黯然失色,通过周围取代基之间的空间相互作用。在四甲基化合物的 X 射线结构中,炔碳显着变形为线性几何形状。取代基效应...