Kinetic studies for amination of ketenimines: change of rate-determining step by electron-withdrawing N-substituents through electronic effects
作者:Kuangsen Sung、Pin-Mei Huang、Shu-Min Chiang
DOI:10.1016/j.tet.2006.03.022
日期:2006.5
to Kk2 for the amination of 1a–d and the Hammett plot was a convex curve with ρD=ρ1=7.08 and ρA=ρK+ρ2=0.98, indicating change of the rate-determining step. The electron-withdrawing para-substituents on the N-phenyl group of ketenimines significantly stabilize the first transition state of CN addition, resulting in change of the rate-determining step to the second step of tautomerization. The N-substituent
is changed from the first step (CN addition) to the second step (tautomerization) when N-substituent of the ketenimines is changed from i-propyl group to p-substituted-phenyl group. Amination reactions of ketenimines 5 and 10 in a solvent with ε=35.9 were designed to explore electronic effects of N-substituents on the amination reactions by means of ab initio calculations. Computation results at level
Vinylidenediamine化的中间产物在胺化反应中发现ñ -我丙基p取代-phenylketenimines 3A -图3e与Ñ -BuNH 2,但它在的胺化反应中发现ñ - p -取代-phenylphenylketenimines 1A - 1C与ñ -低温1 H NMR光谱仪检测BuNH 2,表明当烯酮亚胺的N取代基从i改变时,速率确定步骤从第一步(CN加成)改变到第二步(互变异构)。-丙基至对-取代苯基。设计了在ε = 35.9的溶剂中的酮亚胺5和10的胺化反应,以通过从头算来探索N-取代基对胺化反应的电子影响。在MP2 / 6-31 + G * // HF / 6-31 + G *的水平上的计算结果(Onsager模型)表明,涉及由N-苯基加成CN的第一过渡态的显着电子稳定是导致改变胺化反应的速率决定步骤。