Homoallyl−Cyclopropylcarbinyl Cation Manifold. Trimethylsilyl versus Aryl Stabilization
作者:Xavier Creary、Benjamin D. O'Donnel、Marie Vervaeke
DOI:10.1021/jo062668n
日期:2007.4.1
E-trifluoroacetate (p-CH3) along with the E-substitution product. This isomerization suggests that the cyclized β-silyl cation can isomerize and then reopen to a classical aryl-stabilized cation. By way of contrast, B3LYP/6-31G* computational studies show only cyclized β-silyl cations as energy minima. Open kC cations are higher-energy nonminimum energy structures.
在CD 3 CO 2 D中溶剂化一系列E-和Z -1-芳基-5-三甲基甲硅烷基-3-丁烯-1-基三氟乙酸酯,并确定反应速率以及由这些反应衍生的产物。哈米特地块表现出断裂,这是指示从一个机械变化的ķ Ç处理时最给电子取代基连接至该芳基,以一个ķ Δ涉及为吸电子基团形成环化的β -甲硅烷基碳阳离子中间体的过程。在p -CH 3 O取代的情况下(a k C极端),阳离子中间体会捕获溶剂(占95%)或失去质子(占5%)。在的情况下,米-CF 3取代(一ķ Δ极端),β型甲硅烷基阳离子中间desilylates,得到乙烯基环丙烷产物。具有中间电子性质的取代基可提供更复杂的产品混合物。纯的溶剂分解ž -trifluoroacetate(p -CH 3)给出少量ë -trifluoroacetate(p -CH 3)与沿È-替代产品。这种异构化表明,环化的β-甲硅烷基阳离子可以异构化,然后重新开放为经典