Atropisomerism in a Molecular Gear, 8-Bromo-1,4-dimethyl-9-(2-methylbenzyl)triptycene
作者:Gaku Yamamoto
DOI:10.1246/cl.1990.1373
日期:1990.8
Two rotamers, ap and sc1, of the title compound were separately isolated as stable entities at room temperature. The rotamers gave an equilibrium mixture of the two at elevated temperatures, K([ap]/[sc1]) being 2.26 at 60 °C in toluene-d8. The kinetic parameters for the sc1 → ap conversion are as follows: ΔH‡ = 26.3 ± 0.6 kcal mol−1 (1 cal = 4.184 J), ΔS‡ = −2.7 ± 1.8 cal mol−1 K−1, ΔG‡350K = 27.2 kcal mol−1.
在室温下,分别分离出了标题化合物的两种旋转体 ap 和 sc1,它们是稳定的实体。在高温条件下,这两种转构体形成了一种平衡混合物,在 60 ℃ 的甲苯-d8 溶液中,K([ap]/[sc1])为 2.26。sc1 → ap 转化的动力学参数如下:ΔH‡ = 26.3 ± 0.6 kcal mol-1 (1 cal = 4.184 J),ΔS‡ = -2.7 ± 1.8 cal mol-1 K-1,ΔG‡350K = 27.2 kcal mol-1。
Atropisomerism in Doubly<i>peri</i>-Substituted 9-(2-Methylbenzyl)triptycene Derivatives, 8-Chloro- and 8-Bromo-1,4-dimethyl-9-(2-methylbenzyl)triptycenes
作者:Gaku Yamamoto、Takashi Nemoto、Yuji Ohashi
DOI:10.1246/bcsj.65.1957
日期:1992.7
9-(2-methylbenzyl)triptycene has an energy barrier to gear rotation of 11.8 kcal mol−1 (1 cal = 4.184 J). Introduction of substituents at two of the peri-positions was expected to raise the barrier enough for atropisomerism to be realized in this system. Actually, two stable rotational isomers, ap and sc*(9S*), were separately isolated for 8-chloro- (7) and 8-bromo-1,4-dimethyl-9-(2-methylbenzyl)triptycene (8).