Tautomerism of 9-formyltetrahydro-4H-pyrido[1,2-a]pyrimidin-4-ones and their ring homologues: A 1H, 13C, and 15N nuclear magnetic resonance study

Gábor Tóth, A. Szöllösy, I. Hermecz, Agnes Horváth, Zoltán Mészáros

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Abstract

By 1H, 13C and 15N n.m.r. studies we have established that tautomeric equilibria of 9-formyltetrahydro-4H-pyrido[1,2-a] pyrimidines and their homologues are controlled mainly by the size of the ring containing a single nitrogen atom. Thus in the pyrrolo analogues the enol imine form is predominant, with the azepino homologues the enamine, and with the azocino analogues the imine. The enol imine-enamine interconversion is relatively fast, whereas the imine-enamine interconversion is slow on the n.m.r. time-scale. The relative stabilities of the individual tautomers are explained by stereo-chemical factors and hydrogen bonding.

Original languageEnglish
Pages (from-to)1881-1885
Number of pages5
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number12
Publication statusPublished - 1985

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Imines
Nuclear magnetic resonance
Pyrimidines
Hydrogen bonds
Nitrogen
Atoms

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

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abstract = "By 1H, 13C and 15N n.m.r. studies we have established that tautomeric equilibria of 9-formyltetrahydro-4H-pyrido[1,2-a] pyrimidines and their homologues are controlled mainly by the size of the ring containing a single nitrogen atom. Thus in the pyrrolo analogues the enol imine form is predominant, with the azepino homologues the enamine, and with the azocino analogues the imine. The enol imine-enamine interconversion is relatively fast, whereas the imine-enamine interconversion is slow on the n.m.r. time-scale. The relative stabilities of the individual tautomers are explained by stereo-chemical factors and hydrogen bonding.",
author = "G{\'a}bor T{\'o}th and A. Sz{\"o}ll{\"o}sy and I. Hermecz and Agnes Horv{\'a}th and Zolt{\'a}n M{\'e}sz{\'a}ros",
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T1 - Tautomerism of 9-formyltetrahydro-4H-pyrido[1,2-a]pyrimidin-4-ones and their ring homologues

T2 - A 1H, 13C, and 15N nuclear magnetic resonance study

AU - Tóth, Gábor

AU - Szöllösy, A.

AU - Hermecz, I.

AU - Horváth, Agnes

AU - Mészáros, Zoltán

PY - 1985

Y1 - 1985

N2 - By 1H, 13C and 15N n.m.r. studies we have established that tautomeric equilibria of 9-formyltetrahydro-4H-pyrido[1,2-a] pyrimidines and their homologues are controlled mainly by the size of the ring containing a single nitrogen atom. Thus in the pyrrolo analogues the enol imine form is predominant, with the azepino homologues the enamine, and with the azocino analogues the imine. The enol imine-enamine interconversion is relatively fast, whereas the imine-enamine interconversion is slow on the n.m.r. time-scale. The relative stabilities of the individual tautomers are explained by stereo-chemical factors and hydrogen bonding.

AB - By 1H, 13C and 15N n.m.r. studies we have established that tautomeric equilibria of 9-formyltetrahydro-4H-pyrido[1,2-a] pyrimidines and their homologues are controlled mainly by the size of the ring containing a single nitrogen atom. Thus in the pyrrolo analogues the enol imine form is predominant, with the azepino homologues the enamine, and with the azocino analogues the imine. The enol imine-enamine interconversion is relatively fast, whereas the imine-enamine interconversion is slow on the n.m.r. time-scale. The relative stabilities of the individual tautomers are explained by stereo-chemical factors and hydrogen bonding.

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