Mechanisms of acid-base catalysis of β-elimination reactions in systems activated by a pyridine ring

被引：10

作者：

Alunni, S ^{[1
]}

Ottavi, L ^{[1
]}

机构：

[1] Univ Studi Perugia, Dipartimento Chim, I-06123 Perugia, Italy

来源：

JOURNAL OF ORGANIC CHEMISTRY | 2004年 / 69卷 / 07期

关键词：

D O I：

10.1021/jo030352z

中图分类号：

O62 [有机化学];

学科分类号：

070303 ; 081704 ;

摘要：

beta-Elimination reactions from 1 (in quinuclidine/quinuclidinium chloride, imidazole/imidazolium, and acetate/acetic acid buffers) and from 2 (in imidazole/imidazolium and acetate/acetic acid buffers) with formation of 4-vinylpyridine and 2-vinylpyridine, respectively, were studied. The results of a kinetic study of acid-base catalysis and H/D exchange are consistent with NH+, the protonated substrate, as the species that undergoes carbon deprotonation with an E1cb mechanism. The comparison with previously studied reactions in acetohydroxamate/acetohydroxamic acid buffer confirms this assignment. The high proton activating factor, PAF, value observed (PAF = 1.2 x 10 6 with isomer 1 in quinuclidine/quinuclidinium buffer) can be explained with the high stability by the resonance of the intermediate carbanion.

引用

页码：2272 / 2283

页数：12

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