Synthesis and Dynamic Stereochemistry of Azulene-Substituted 9-Fluorenyl, 9,10-Dihydro-10,10-dimethyl-9-anthryl, 10,11-Dihydro-5<i>H</i>-dibenzo[<i>a</i>,<i>d</i>]cyclohepten-5-yl, and 5<i>H</i>-Dibenzo[<i>a</i>,<i>d</i>]cyclohepten-5-yl Cations. Correlations of Stabilities of the Carbocations and Rotational Barrier of Azulene Ring
作者:Shunji Ito、Jun Kawakami、Akio Tajiri、Daisuke Ryuzaki、Noboru Morita、Toyonobu Asao、Masataka Watanabe、Nobuyuki Harada
DOI:10.1246/bcsj.78.2051
日期:2005.11
The carbocations in the title: 9-(1-Azulenyl)-9-fluorenyl, 9-(1-azulenyl)-9,10-dihydro-10,10-dimethyl-9-anthryl, 5-(1-azulenyl)-10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-yl, and 5-(1-azulenyl)-5H-dibenzo[a,d]cyclohepten-5-yl cations (4c, 5a–c, 6a–c, and 7a–c) were prepared by hydride abstraction of the corresponding hydrocarbon derivatives and their properties were fully characterized. The pKR+ values of 4c, 5a–c, 6a–c, and 7a–c were determined as −2.7, 0.5–2.7, 8.4–9.1, and 7.4–8.5, respectively, which were higher by 8.1, 6.0–8.2, 15.1–16.1, and 13.1–14.3 pK units, respectively, than those of the corresponding phenyl derivatives. Conformations and energy barriers for 4c, 5a–c, 6a–c, and 7a–c were studied by means of dynamic nuclear magnetic resonance spectroscopy (DNMR) techniques. The thermodynamic stability of the cations and the barrier to the rotation of the 1-azulenyl group were significantly affected by not only the electron density effect but also the dynamic stereochemistry of the connected-ring systems.
标题中的碳阳离子:9-(1-薁基)-9-芴基、9-(1-薁基)-9,10-二氢-10,10-二甲基-9-蒽基、5-(1-薁基)- 10,11-二氢-5H-二苯并[a,d]环庚烯-5-基和5-(1-薁基)-5H-二苯并[a,d]环庚烯-5-基阳离子(4c、5a–c、 6a-c和7a-c)是通过相应烃衍生物的氢化物抽提制备的,并且它们的性质得到了充分表征。 4c、5a–c、6a–c 和 7a–c 的 pKR+ 值分别确定为 -2.7、0.5–2.7、8.4–9.1 和 7.4–8.5,分别高出 8.1、6.0–8.2、15.1分别比相应的苯基衍生物高 –16.1 和 13.1–14.3 pK 单位。通过动态核磁共振波谱 (DNMR) 技术研究了 4c、5a–c、6a–c 和 7a–c 的构象和能垒。阳离子的热力学稳定性和 1-azulenyl 基团的旋转势垒不仅受到电子密度效应的显着影响,而且还受到连接环系统的动态立体化学的影响。