Mechanism of Di-<i>tert</i>-Butylsilylene Transfer from a Silacyclopropane to an Alkene
作者:Tom G. Driver、K. A. Woerpel
DOI:10.1021/ja0301370
日期:2003.9.1
Kinetic and thermodynamic studies of the reactions of cyclohexene silacyclopropane 1 and monosubstituted alkenes suggested a possible mechanism for di-tert-butylsilylene transfer. The kinetic order in cyclohexene silacyclopropane 1 and cyclohexene were determined to be 1 and -1, respectively. Saturation kinetic behavior in monosubstituted alkene concentration was observed. Competition experiments between
环己烯硅杂环丙烷 1 和单取代烯烃反应的动力学和热力学研究表明了二叔丁基亚甲硅烷基转移的可能机制。环己烯硅杂环丙烷 1 和环己烯的动力学顺序分别确定为 1 和 -1。观察到单取代烯烃浓度下的饱和动力学行为。取代的苯乙烯和 1 的不足量的二叔丁基亚甲硅烷之间的竞争实验与哈米特方程很好地相关,并使用 sigma(p) 常数提供了 -0.666 +/- 0.008 的 rho 值。这些数据支持两步机制,包括从 1 中可逆地挤出二叔丁基亚甲硅烷,然后是亚甲硅烷对单取代烯烃的不可逆协同亲电攻击。发现 Eyring 激活参数为 DeltaH++ = 22.1 +/- 0.9 kcal.mol(-1) 和 DeltaS++ = -15 +/- 2 eu。环烯烃和烯丙苯之间的竞争实验确定环烯烃是更有效的亚甲硅烷陷阱 (k(rel) =1.3,DeltaDeltaG++ = 0.200 kcal.mol(-