Kinetic analysis of the asymmetric amplification exhibited by B-chlorodiisopinocampheylborane
Kinetic analysis of the asymmetric amplification exhibited by B-chlorodiisopinocampheylborane
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B-氯二异蒎蒎硼烷不对称扩增的动力学分析
DOI：
10.1002/poc.730
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发表时间：
2004
影响因子：
1.8
通讯作者：
J. Sowa
中科院分区：
文献类型：
--
作者：
C. Moeder;J. Sowa
实验测定了具有不对称放大作用的B-氯二异苯基硼烷(Dip-Cl)的杂手性和同手性物种的相对反应速率。用水淹法将表观二级反应还原为准一级反应，得到均手性和杂手性物种的反应速率常数分别为3.8(±1.0) × 10−4和1.7(±0.8) × 10−5 m−1 S−1(−15°C)。由此产生的相对反应速率，即卡根和同事模型中的g值，为0.04 ± 0.03。为了确认这一值，还进行了其他实验。在整个反应转化过程中模拟了最终产物的手性纯度劣化过程，并与实际值进行了比较。通过极小化，得到相对反应速率(G)为0.08 ± 0.04。最后，利用8-羟基喹啉络合作用，测定了反应溶液中残留的二氯二磷的异构化比的变化。以观察到的速率消耗异构体所需的相对反应速率(G)为0.08 ± 0.01。因此，三种独立的方法被用来测定杂手性和同手性物种的相对反应速率(G)，得到的平均值为0.07 ± 0.03。版权所有©2004 John Wiley&Sons，Ltd.
A quantitative investigation was undertaken to determine experimentally the relative reaction rates of the heterochiral and homochiral species of B-chlorodiisopinocampheylborane (Dip-Cl), a reagent that exhibits asymmetric amplification. Using the method of flooding to reduce the apparent second-order reaction to pseudo-first-order conditions, rate constants of 3.8 (±1.0) × 10−4 and 1.7 (±0.8) × 10−5 m−1 s−1 (at −15°C) were found for the homochiral and heterochiral species, respectively. The resulting relative reaction rate, the value of g in Kagan and co-workers' model, was 0.04 ± 0.03. Additional experiments were conducted to confirm this value. The deterioration of the chiral purity of the final product was simulated throughout reaction conversion and compared with actual values. Through minimization, a relative reaction rate (g) of 0.08 ± 0.04 was determined. Finally, using 8-hydroxyquinoline complexation, the change in isomeric ratio of the Dip-Cl remaining in the reaction solution was measured. The relative reaction rate (g) required to consume the isomers at the observed rate was determined as 0.08 ± 0.01. Thus, three independent methods have been used to determine the relative reaction rate (g) of the heterochiral to homochiral species with good agreement to give an average value of 0.07 ± 0.03. Copyright © 2004 John Wiley & Sons, Ltd.