Small-ring annulation and ring expansion of the dodecahedrane framework. Homododecahedranone and the 21-homododecahedryl cation
Small-ring annulation and ring expansion of the dodecahedrane framework. Homododecahedranone and the 21-homododecahedryl cation
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DOI：
10.1021/jo00273a028
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发表时间：
1989-06
影响因子：
3.6
通讯作者：
L. Paquette;T. Kobayashi;M. A. Kesselmayer;J. Gallucci
中科院分区：
文献类型：
--
作者：
L. Paquette;T. Kobayashi;M. A. Kesselmayer;J. Gallucci
环丙烷环与十二面体骨架的融合已经在两步法中从母体烃实现。在相转移条件下用二氯卡宾处理得到（二氯甲基）十二烷（6），当在-100 ℃下与乙醚中的叔丁基锂反应时，它经历了快速的分子内CH插入。过量的甲基或苯基锂在0 ℃的乙醚溶液中与6作用，得到甲基和苯基类似物8和9。后一种碳氢化合物的X射线晶体学分析表明，它的三元环没有变形，而紧邻的那些五边形环则发生了非常有意义的变形。与其他环丙烷化螺桨烷的~（13）cNMR进行了比较，并讨论了环合过程的可能途径。通过银离子促进的6的还原-水解，有效地实现了引入酮碳的十二烷骨架的扩展。通过X射线晶体学分析阐明的高十二面体酮（4）的结构特征表明，21-高十二面体磺酸酯的SN 1溶剂分解应以与相应的2-金刚烷基衍生物相当的速率进行。通过电导法测定的乙酰解速率与这些预期非常一致。此外，电离为21-同十二面体阳离子（5）进行，保留完整的多环框架。通过制备单氘代甲磺酸酯和通过NMR光谱分析二乙酸酯产物混合物来评估5中CH乱序的水平。结果表明，主要采用了一个非立体有择的过程，涉及一个完全溶剂化的碳阳离子，并证实了事实，5确实能够简并rearrangement.The分子阵列体现在dodecahedrane（1）是reknown其异常高的对称性和美学的吸引力。[3]它也可以被认为是一系列不寻常的、理论上令人着迷的结构的基石，这些结构包含了多学科感兴趣的广泛性质。随着1在合理数量的可用性，4在这些实验室中已经开发出一个针对这些理想目标的选择代表性的合成的程序。到目前为止，十二烯（2）只在气相中被观察到，还没有作为一种可行的实验室中间体。因此，任何制备环丙十二烷（3）的计划目前都不能依赖2作为祖分子。虽然二氯卡宾加成到环烯烃上，然后脱氯，可以很好地合成含有横向稠合环丙烷环的螺桨烷小分子6，但这种策略显然不适用于本文。我们对3的兴趣源于这样的认识：三元环与双环系统的关键CC键的融合普遍会导致相当大的结构扭曲，并伴随着地面应变的增强。7 8”9
Fusion of a cyclopropane ring to the dodecahedrane framework has been achieved in a two-step process from the parent hydrocarbon. Treatmentwith dichlorocarbene under phase-transfer conditions delivers (dichloro-methyl) dodecahedrane (6), which undergoes rapid intramolecular CH insertion when reacted withtert-butyllithium in ether at-100 C. The action of excess methyl-or phenyllithium on 6 in ether solution at 0 C gives rise to the methyl and phenyl analogues 8 and 9. X-ray crystallographic analysis of the latter hydrocarbon shows its three-membered ring to be free of distortion, whilethose pentagonal rings in the immediate vicinity are very meaningfully distorted. A13c NMR comparison with other cyclopropanated propellanes is made, and the probable path of the ring-closure process is discussed. Expansion of thedodecahedrane frameworkwith incorporation of a ketonic carbon was efficiently realized by silver ion promoted rearrangement-hydrolysis of 6. The structural features of homododecahedranone (4), elucidated by X-ray crystallographic analysis, suggested that SN1 solvolysis of a 21-homododecahedryl sulfonate ester should proceed at a rate comparable to that of the corresponding 2-adamantyl derivative. Acetolysis rates, determined conductometrically, fall nicely in line with these expectations. Furthermore, ionization to the 21-homododecahedryl cation (5) proceeds with retention of the intact polycyclic framework. The level of CH scrambling in 5 was assessed by preparation of the monodeuterated mesylate and analysis of the di acetate product mixture by NMR spectroscopy. The results point to predominant adoption of a nonstereospecific process involving a fully solvated carbocation and confirm the fact that 5 is indeed capable of degenerate rearrangement.The molecular array embodied in dodecahedrane (1) is reknown for its exceptionally high symmetry and aesthetic allure. 3 It also may be considered the cornerstone of a family of unusual and theoretically fascinating structures that encompass a wide range of properties of multidisciplinary interest. With the availability of 1 in reasonable quantities, 4 there has developed in these laboratories a program directed toward the synthesis of select repre-sentatives of these desirable targets. To date, dodecahedrene (2) has been observed only in the gas phase5 and is not yet available as a viable labora-tory intermediate. Consequently, any plan to prepare cyclopropadodecahedrane (3) cannot currently rely on 2 as a progenitor molecule. Although dichlorocarbene ad-dition to a cycloalkene followed by dechlorination has served well as a synthetic entry to small propellane mol-ecules containing a laterally fused cyclopropane ring, 6 this tactic is clearly not serviceable in the present context. Our interest in 3 was motivated by knowledge that fu-sion of a three-membered ring across a key CC bond of a bicyclic ring system universally results in the introduction of considerable structural distortion with concomitant enhancement of ground-strain. 7 8" 9