selectivity. Thus, aryl- and silyl-substituted sulfonium ylides (1 equiv.) were (separately) reacted with Et(3)B (1.5 equiv.) followed by Ph(3)B (1.5 equiv.) The experiments were repeated changing the order of addition of the two boranes. It was found that the aryl-substituted sulfonium ylide only trapped the first borane that was added indicating that ate complex formation was non-reversible and so was the
已经研究了三甲基甲
硅烷基取代的化烷基化物与有机
硼烷(Ph(3)B,Et(3)B)的反应,尽管获得的同系产物收率很高(氧化为相应的醇后),但对映体过量较低我们的基于
樟脑的手性
硫化物(最高40%ee,请参见相应的苯基取代的
磺酸盐给出了> 95%ee)。进行交叉实验以确定选择性差异的性质。因此,芳基和甲
硅烷基取代的化(1当量)与Et(3)B(1.5当量)(然后)与Ph(3)B(1.5当量)反应(分别)。重复进行实验,改变顺序两个
硼烷的加法运算。发现芳基取代的叶立德仅捕获了所添加的第一
硼烷,表明产物络合物的形成是不可逆的,选择性确定步骤也是如此。相比之下,甲
硅烷基取代的lide叶立德仅捕获Ph(3)B(它比Et(3)B更具反应性),表明盐络合物的形成是可逆的,因此1,2-迁移现在是选择性的决定步骤。已对反应进行了计算研究,并复制了实验观察结果。他们进一步揭示,在甲
硅烷基取代的鎓盐的情况下,可逆性的