3-X-2(1H)-吡啶酮互变异构体系的理论计算

２（１Ｈ）－吡啶酮类化合物常呈现出诱人的生物活性［１，２］．由于酮式和烯醇式结构具有互变异构化性质，因此确定其互变异构平衡体系中的优势结构及研究取代基对平衡体系的影响，对阐明该类化合物的生物活性及进行构效关系的研究有着重要的意义．当其３－位含有可与２－位羰基或２－位羟基形成分子内氢键的基团时，势必对互变异构平衡产生影响．基于该类化合物的互变异构平衡有着强烈的溶剂效应［３］，本文对３－Ｘ－２（１Ｈ）－吡啶酮（Ｘ＝ＮＯ２，ＮＨ２，ＣＯＯＨ）及其烯醇式互变异构体分别在气相和溶液中进行了理论计算，考察了…

Theoretical Calculations of the Tautomeric Equilibrium in 3-X-2(1H)-Pyridones

The geometries of 3-X-2(1H)-pyridones(X=NO₂, NH₂, COOH) and their tautomers in the gas phase and DMSO solution(SCRF) have been obtained at HF/6-31G^**and MP₂/6-31G^**levels. The influences of intramolecular hydrogen bond on the tautomeric equilibrium have also been investigated. In the gas phase, the calculated results show that the enol form is more stable than the keto form for 3-NO₂-2(1H)-pyridone, and the keto?enol equilibrium shift right due to the formation of intramolecular hydrogen bond between 3-nitro and 2-hydroxyl group, while for the amino and carboxyl-derivatives, the keto forms are favored over the enol forms because of the stronger intermolecular hydrogen bonds in keto-tautomers. However, owing to the polarization effects of solvent, it can be predicted that the keto-tautomers are dominant for all of the title compounds in DMSO solution, which are in good agreement with the experimental results.