Carbon protonation of 2,4,6-triaminopyrimidines: synthesis, NMR studies, and theoretical calculations.
J Org Chem
; 71(13): 4910-8, 2006 Jun 23.
Article
em En
| MEDLINE
| ID: mdl-16776521
ABSTRACT
Several C5-substituted 2,4,6-triaminopyrimidine derivatives and their HBF4 salts were synthesized to study the carbon protonation of the pyrimidine ring. NMR investigations in DMSO-d6 prove experimentally that, in addition to the usual protonation at N1, the compounds can be protonated at C5 as well. We present several new stable cationic sigma-complexes in the pyrimidine series, where C5 protonation predominates over N1 protonation. Quantum chemical calculations using the B3LYP/cc-pVDZ method were utilized in the gas phase and also in DMSO solvent with the polarized continuum model (PCM) method to rationalize the observed protonation behavior. Results of the calculations accord with the experimental observations and prove that combined steric and electronic effects are responsible for the observed C5 protonation and for sigma-complex stability. We demonstrate that C5 protonation is a general feature of the 2,4,6-triaminopyrimidine system.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Pirimidinas
/
Teoria Quântica
/
Carbono
/
Espectroscopia de Ressonância Magnética
Tipo de estudo:
Diagnostic_studies
/
Prognostic_studies
Idioma:
En
Revista:
J Org Chem
Ano de publicação:
2006
Tipo de documento:
Article
País de afiliação:
Hungria