Structure - Nucleophilicity relationships for enamines
Structure - Nucleophilicity relationships for enamines
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DOI：
10.1002/chem.200204666
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发表时间：
2003-05-23
影响因子：
4.3
通讯作者：
Mayr, H
中科院分区：
文献类型：
--
作者：
Kempf, B;Hampel, N;Mayr, H
在二氯甲烷中通过光度法研究了二苯甲基阳离子与 22 种烯胺、三种吡咯和三种吲哚的反应动力学。这些富电子at-系统的亲核性参数N和斜率参数s由方程log k (20°C) = s(E+N)导出，并与其他pi-系统（硅基烯醇醚、硅基乙烯酮缩醛）和碳负离子的亲核性进行比较。结果表明，烯胺的亲核反应活性覆盖十多个数量级，与低反应性端的烯醇醚和高反应性端的碳负离子相当。由于氮攻击的产物在热力学上不如反应物稳定，因此观察到的速率常数指的是碳-碳键的形成。在某些情况下，测量了亚胺离子形成的平衡常数，这使得人们能够确定这些反应的固有速率常数。
The kinetics of the reactions of benzhydryl cations with 22 enamines, three pyrroles, and three indoles were investigated photometrically in dichloromethane. The nucleophilicity parameters N and slope parameters s of these electron-rich at-systems were derived from equation log k (20degreesC) = s(E+N) and compared with the nucleophilicities of other pi-systems (silyl enol ethers, silyl ketene acetals) and carban-ions. It is shown that the nucleophilic reactivities of enamines cover more than ten orders of magnitude, comparable to enol ethers on the low reactivity end and to carbanions on the high reactivity end. Since the products of N-attack are thermodynamically less stable than the reactants, the observed rate constants refer to the formation of the carbon-carbon bonds. In some cases, equilibrium constants for the formation of iminium ions were measured, which allow one to determine the intrinsic rate constants of these reactions.