Relative Substituent Effects on Alkaline Solvolysis of β-Lactams (2-Azetidinones) and Amides
作者:Richard J. Washkuhn、Joseph R. Robinson
DOI:10.1002/jps.2600600811
日期:1971.8
The effect of aliphatic and aromatic substituents, in the 1- and 3-positions of β-lactams, on the rate of solvolysis were examined and compared to analogous substituent effects in the model linear amides. It was found that substituent effects in the β-lactams could be quantitated using the Taft equation, and that a greater sensitivity to polar effects exists in the β-lactams as compared to the model
在β-内酰胺的1-位和3-位上,脂族和芳族取代基对溶剂分解速率的影响进行了研究,并将其与模型线性酰胺中的类似取代基效应进行了比较。发现可以使用Taft方程定量β-内酰胺中的取代基作用,并且与模型线性酰胺相比,β-内酰胺中对极性作用具有更大的敏感性。另外,对于内酰胺的1-位和3-位的单个取代基,与线性酰胺相比,对溶剂分解速率的空间影响较小。这些β-内酰胺的碱解机理似乎是氢氧根离子对酰胺基的羰基碳的限速攻击,而不是像对γ-内酰胺所提议的那样,电离的四面体中间体的分解。β-内酰胺在80°的水解研究产生了不同的降解途径,因为氨基酸的脱氨作用似乎是限速的。因此,应谨慎进行β-内酰胺的高温研究。最后,得出的结论是,β-内酰胺类对亲核试剂(如氢氧根和甲醇根离子)的反应性不是非常稳定,并且其不稳定性非常接近母体线性酰胺。