Deoxymetalation reactions.the mechanisms of deoxysilylation of mono-trimethylsilyl-and bis-trimethylsilyl-substituted alcohols and a comparison to the mechanism of deoxystannylation and deoxyplumbylation
作者:Dennis D. Davis、Henry M. Jacocks
DOI:10.1016/s0022-328x(00)93462-4
日期:1981.2
trimethylsilyl group, and a mechanism involving a hyper- conjugatively-stabilized carbocation intermediate is proposed. In contrast, the deoxymetalation reactions of the triphenyltin-, triphenyllead-, and iodomercury-analogs exhibits very different structure-reactivity relationships and have been described as proceeding through concerted E2-like or bridge-ion mechanisms. These mechanistic regimes are
2-三甲基甲硅烷基-1-羟基乙烷,4、1-三甲基甲硅烷基-2-羟基丙烷,5、1,3-双(三甲基甲硅烷基)-2-羟基丙烷,6和1-三甲基甲硅烷基-2的酸催化脱氧甲硅烷基化的相对速率在40℃下在9体积%的甲醇水溶液中,发现7的-甲基-2-羟基丙烷分别为1:10 3.30:10 5.92:10 6.77。这些比率与携带核试剂的碳上的取代基的δ +常数的总和成正比(ϱ += − 11)。两个三甲基甲硅烷基的加合速率的加速作用要求每个三甲基甲硅烷基具有相同的共轭稳定作用,并提出了一种涉及超共轭稳定的碳正离子中间体的机理。相反,三苯基锡,三苯基铅和碘汞类似物的脱氧金属化反应显示出非常不同的结构反应性关系,并被描述为通过协同的E 2进行。类或桥离子机制。通过考虑桑顿反应键规则,考虑了有机金属离去基团的共轭相互作用,电逸性和亲核溶剂辅助,可以协调这些机制。该分析表明存在一系列的合并机制,酸催化的脱氧甲硅烷基化代表一个极端,E