Clarification of the Stereochemical Course of Nucleophilic Substitution of Arylsulfonate-Based Nucleophile Assisting Leaving Groups
作者:D. Christopher Braddock、Rebecca H. Pouwer、Jonathan W. Burton、Phillip Broadwith
DOI:10.1021/jo900991z
日期:2009.8.21
Secondary alcohols modified as tosylates, PEG-sulfonates, or quisylates undergo inversion of configuration at the reacting center when treated with lithium halide in acetone at reflux, where the PEG-sulfonates and quisylates are substantially more reactive. In sterically hindered cases, elimination is a competing process. In contrast, when treated with TiCl4, simple secondary sulfonates give chloride
当在丙酮中用卤化锂在回流下处理时,被修饰为对甲苯磺酸盐,PEG-磺酸盐或对甲苯磺酸盐的仲醇在反应中心发生构型转化,其中PEG-磺酸盐和对甲苯磺酸盐的反应性更高。在空间受限的情况下,淘汰是一个相互竞争的过程。相反,当用TiCl 4处理时,简单的仲磺酸盐使氯化物产物的构型部分反转。在这些条件下,在给定的烷基磺酸盐底物中观察到的任何构型保留都可能是由于相邻基团的参与或对碳正离子(或离子对)的非对映选择性攻击,而不是S N i机理。