On the Substituent Effects of the Thermal Ethenylcyclopropane-to-Cyclopentene Rearrangement: Gas-Phase Kinetics of Ethoxy-, Methylthio- and Trimethylsilyl-Substituted Ethenylcyclopropanes
作者:Gregory McGaffin、Bernd Grimm、Ute Heinecke、Holger Michaelsen、Armin de Meijere、Robin Walsh
DOI:10.1002/1099-0690(200109)2001:18<3559::aid-ejoc3559>3.0.co;2-v
日期:2001.9
high yields and subjected to gas-phase pyrolytic kinetic investigations. All ethenylcyclopropanes rearranged cleanly to the correspondingly substituted cyclopentenes, although in the case of the 2-substituted compounds, cis/trans isomerization was additionally observed (both stereoisomers were investigated in these cases). All rearrangements obeyed first-order kinetics independent of pressure and surface-to-volume
以高产率制备了一系列 1-和 2-取代的乙烯基环丙烷,并进行了气相热解动力学研究。所有乙烯基环丙烷都干净地重排为相应取代的环戊烯,尽管在 2-取代化合物的情况下,还观察到顺/反异构化(在这些情况下研究了两种立体异构体)。所有重排都服从与压力和表面体积比无关的一级动力学。为这些均相、单分子反应获得了合理的 Arrhenius 参数。1-三甲基甲硅烷基和 1-甲硫基取代基产生适度的速率加速,与双自由基机制一致。1-三甲基甲硅烷基取代导致的速率延迟的先前发现归因于空间位阻。2-乙氧基和 2-甲硫基取代基 [在 (E)-和 (Z)-配置中] 产生更大的速率加速,与双自由基机制不一致。(Z)-异构体重排动力学的空间效应似乎相对不重要。首次记录和分析了甲硫基取代基效应。