Diastereoselectivity in the McLafferty Rearrangement of Photoionized 3-Methyl Valeramide
作者:Jessica Loos、Detlef Schröder、Helmut Schwarz
DOI:10.1021/jo0482458
日期:2005.2.1
fragmentation patterns of other photoionized isotopomers permits the determination of primary and secondary kinetic isotope effects (KIEs), the branching ratios of competing McLafferty reactions, and the steric effect (SE) associated with transfer of the diastereotopic H(D) atoms at C(4). While the associated KIEs of the title reaction are negligible, the steric effect (SE = 2.9) is remarkably large for
光电离的3-甲基戊酰胺的McLafferty重排过程是准无障碍的,具有很高的区域选择性。的立体专一性标记的顺式的质谱-和反- [4-d 1]-非对映异构体显示出相对于C(3)上的甲基(作为空间标记)在反位激活γ-氢/氘的强烈偏好。定量分析其他光离子化的同位素异构体的碎裂模式,可以确定一级和二级动力学同位素效应(KIE),竞争性麦克拉菲反应的分支比以及与非对映异构体H(D)原子转移相关的空间效应(SE)在C(4)。尽管标题反应的相关KIE可以忽略不计,但对于其他方面灵活的单官能化合物而言,空间效应(SE = 2.9)则非常大。该发现可以通过用于初始γ-H原子转移的优选椅状过渡结构来解释。