The Rearrangement of 1-para-Substituted Phenyl-1-cyclopropylethylenes
The Rearrangement of 1-para-Substituted Phenyl-1-cyclopropylethylenes
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DOI：
10.1021/jo01014a508
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发表时间：
1965-03
影响因子：
3.6
通讯作者：
A. Ketley;J. L. McClanahan
中科院分区：
文献类型：
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作者：
A. Ketley;J. L. McClanahan
目前还没有系统的研究报道取代基的乙烯基环丙烷重排率的影响。我们在这里描述的结果的一部分，这样的研究的一系列1-对位取代的苯基-1-环丙基乙烯的重排率。最初使用玻璃棉填充流动系统在400 ℃下进行热解。反应进行干净，在每种情况下都得到90%或更多的相应的1-对位取代的苯基环戊烯。由于除氟代衍生物外的所有化合物的反应速率在400 ℃时都高得无法测量，因此在350 ℃时，在抽真空的密封管中，在气相中进行动力学试验。通过vpc显示了产物与在400获得的产物的同一性。图1显示了每种化合物的一阶图。除了氟代衍生物之外，所有的都落在一条线上，因此，所有的都具有相同的重排速率（1.03±0.07 × 10-4秒-1）。1）。p-氟代衍生物以大约一半的速率重排（5.03±0.33 × 10-5秒）。1）。这些值非常接近从Frey和马歇尔的1-甲基-1-环丙基乙烯数据1外推的350 ℃下的速率常数（1.15 × 10-6秒-1）。1）。因此，乙烯基环丙烷重排似乎对极性效应相对不敏感，至少通过1-碳传递。这种不敏感性可以解释的机制，其中的速率决定步骤是开放的环丙基环的双自由基或“扩大环”4由施拉格和Rabinovitch假设。2氟苯基衍生物的生成率较低可能是由于该取代基在第二步中与环戊烯形成双键的共轭较小。这可能会降低五元环的闭合速率，低于环丙基环的裂变或膨胀速率。因此，第二步将成为决定利率的步骤。
There has been no systematic study reported of the effect of substituents on the rates of vinylcyclopropane rearrangements. We describe here results of part of such a study on the rates of rearrangement of a series of 1-para-substituted phenyl-l-cyclopropylethylenes. Pyrolyses were initially conducted using a glass wool packed flow system at 400. The reactions proceeded cleanly giving in each case 90% or more of the corre-sponding 1-para-substituted phenylcyclopentene. Since the reaction rates of all except the fluoro deriva-tive were immeasurably high at 400, kinetic runs were made, in the gas phase, in evacuatedsealed tubes at 350. The identity of the products to those ob-tained at 400 was shown by vpc Figure 1 shows first-order plots for each compound. All except the fluoro derivative fall onto one line and all, consequently, have the same rate of rearrangement (1.03±0.07 X 10-4 sec.-1). The p-fluoro derivative rearranges at approximately half this rate (5.03±0.33 X 10-5 sec.-1). These values are very close to the rate constant at 350 extrapolated from Frey’s and Marshall’s data1 for 1-methyl-1-cyclopropylethylene (1.15 X 10-6 sec.-1). The vinylcyclopropane rear-rangement appears, therefore, to be relatively insensi-tive to polar effects, at least as transmitted through the 1-carbon. This insensitivity can be explained by a mechanism in which the rate-determining step is the opening of the cyclopropyl ring either to thediradical or to the “expanded ring” 4 postulated by Schlag and Rabinovitch. 2 The lower rate of the fluorophenyl derivative may be due to the smallerconjugation of this substituent in the second step with the forming double bond of the cyclopentene. This could decrease the rate of closure of the five-membered ring below that of fission or expansion of thecyclopropyl ring. The second step would thus become rate-determining.