Metal Ion Catalysis in the β-Elimination Reactions of <i>N</i>-[2-(4-Pyridyl)ethyl]quinuclidinium and <i>N</i>-[2-(2-Pyridyl)ethyl]quinuclidinium in Aqueous Solution
作者:Sergio Alunni、Tiziana Del Giacco、Paolo De Maria、Giorgia Fifi、Antonella Fontana、Laura Ottavi、Ilaria Tesei
DOI:10.1021/jo030374l
日期:2004.5.1
Catalysis of the β-elimination reaction of N-[2-(4-pyridyl)ethyl]quinuclidinium (1) and N-[2-(2-pyridyl)ethyl]quinuclidinium (2) by Zn2+ and Cd2+ in OH-/H2O (pH = 5.20−6.35, 50 °C, and μ = 1 M KCl) has been studied. In the presence of Zn2+, the elimination reactions of both isomers occur from the Zn2+-complexed substrates (C). The equilibrium constants for the dissociation of the Zn2+-complexes are
所述的催化β的反应β-消除Ñ [2-(4-吡啶基)乙基]奎宁环鎓( - 1)和Ñ [2-(2-吡啶基)乙基]奎宁环鎓( - 2)由锌2+和Cd 2+在OH - / H 2 O(pH值= 5.20-6.35,50℃,和μ = 1 M KCl)中进行了研究。在Zn 2+的存在下,两种异构体的消除反应均从Zn 2+络合的底物(C)发生。Zn 2 +-络合物解离的平衡常数如下:K d = 0.012±0.003 M(异构体1),K d= 0.065±0.020M(异构体2)。的值为异构体1是4.81×10 - 6小号- 1。对于异构体2个两者的速率常数为“水”和OH -中的Zn的诱导反应2+ -complexed衬底可以测量,尽管OH的低浓度-在所研究的反应混合物[ = 1.97×10 - 6小号- 1和= 21.9中号- 1个小号- 1, 分别]。测得的金属活化因子(MetAF),即,之间的反应性比的复合和未复合衬底,是8