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Updated: May 6, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
From 2-hydroxypyridine to 4(3H)-pyrimidinone: computational study on the control of the tautomeric equilibrium
Tiago L P Galvão1, Inês M Rocha, Maria D M C Ribeiro da Silva
1Centro de Investigação em Química, Department of Chemistry and Biochemistry, Faculty of Science, University of Porto , Rua do Campo Alegre, 687, P-4169-007, Porto, Portugal .
Abstract:
In this work is investigated why the entrance of a nitrogen atom in the ring of cis-2-hydroxypyridine and 2-pyridinone, resulting in cis-4-hydroxypyrimidine and 4(3H)-pyrimidinone, respectively, shifts the tautomeric equilibrium from the hydroxyl form, in the pyridine derivative, to the ketonic form, in the pyrimidine derivative. The conclusions obtained for these model systems allow us to understand how to control the gaseous-phase keto-enol tautomeric equilibrium in nitrogen heterocyclic rings and justify the tautomeric preference in pyrimidine nucleobases. The experimental and computational energetics of tautomeric equilibrium were interpreted in terms of the aromaticity, intramolecular hydrogen bonds, and electronic delocalization, evaluated using nucleus independent chemical shifts, quantum theory of atoms in molecules, natural bond orbital analysis, and the thermodynamic changes of appropriate reactions.
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