Reactivities of Methylenetriangulanes and Spirocyclopropanated Bicyclopropylidenes toward Bromine. Relative Stabilities of Spirocyclopropanated versus Methyl-Substituted Bromonium Ions
作者:Sergei Kozhushkov、Thomas Späth、Torsten Fiebig、Bernard Galland、Marie-Francoise Ruasse、Prince Xavier、Yitzhak Apeloig、Armin de Meijere
DOI:10.1021/jo0162686
日期:2002.6.1
rings enhances the rate of bromination and stabilizes the intermediate cyclopropyl bromonium cations against ring opening in the course of bromine addition. Calculations at the B3LYP/6-311G(d,p) level show that unsymmetrical bromonium ions are the intermediates, and that they are stabilized by the spiroannelation with cyclopropane rings. The bromonium ion derived from 1 is less stable by 6.3 kcal mol-1
在25℃下在甲醇中向亚甲基环丙烷(1),双环亚丙基(2)和螺环丙烷化的亚甲基环丙烷和双环亚丙基3-6中的溴加成基本上以与相应的低聚甲基取代的乙烯相同的速率进行。越来越多的螺环氮化三元环提高了溴化速率,并稳定了中间体环丙基溴阳离子对溴的添加过程中的开环。在B3LYP / 6-311G(d,p)水平进行的计算表明,不对称的溴离子是中间体,并且它们通过与环丙烷环的螺线环化反应得以稳定。与异丁烯相比,衍生自1的溴离子的稳定性差6.3 kcal mol-1。3和4中的一个或两个螺环丙烷环分别以9.6和16.4 kcal mol-1稳定相应的溴离子,而乙烯基环丙烷(7)和1,1-二环丙基乙烯(8)中的一个或两个α-环丙基取代基稳定相应的溴离子分别为13和29 kcal mol-1。所有研究的烯烃的实验溴化速率与相应的溴离子的相对能量计算得很好相关(r2 = 0.93)。在亚甲基环丙烷1、3和4(r2 =