Isotope Effects Reveal an Alternative Mechanism for "Iminium-Ion" Catalysis.
Isotope Effects Reveal an Alternative Mechanism for "Iminium-Ion" Catalysis.
复制标题
同位素效应揭示了“亚胺离子”催化的替代机制。
DOI：
10.1021/jacs.8b04856
复制
发表时间：
2018
影响因子：
15
通讯作者：
Vetticatt,MathewJ
中科院分区：
文献类型：
--
作者：
Izzo,JosephA;Poulsen,PernilleH;Intrator,JeremyA;Jørgensen,KarlAnker;Vetticatt,MathewJ
基于13 C动力学同位素效应（KIEs）和密度泛函理论（DFT）计算，提出了二芳基脯氨醇硅醚催化烯醛与过氧化氢环氧化反应的新机理.在烯醛的羰基和β-碳原子上测量的正常13 C KIE表明两个碳原子都参与了速率决定步骤。计算表明，广泛接受的亚胺离子机制并不能解释这种实验观察。Asyn-SN 2 ′取代机制，避免了形成一个离散的亚胺离子中间体，成为最有可能的机制之间的协议的基础上，实验和预测的KIE。
A novel mechanism for the epoxidation of enals with hydrogen peroxide catalyzed by diarylprolinol silyl ether supported by experimental13C kinetic isotope effects (KIEs) and density functional theory calculations is presented. Normal13C KIEs, measured on both the carbonyl- and β-carbon atoms of the enal, suggest participation of both carbon atoms in the rate-determining step. Calculations show that the widely accepted iminium-ion mechanism does not account for this experimental observation. Asyn-SN2′ substitution mechanism, which avoids formation of a discrete iminium-ion intermediate, emerges as the most likely mechanism based on agreement between experimental and predicted KIEs.