Nitrogen bridgehead compounds. Part 29. Tautomerism and Z-E isomerism of ethyl 9-aminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3- carboxylates and their homologues

Gábor Tóth, A. Szöllösy, Benjamin Podányi, I. Hermecz, Ágnes Horváth, Zoltán Mészáros, I. Bitter

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Abstract

1H and 13C n.m.r. studies have proved that ethyl 9-dimethylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidine-3-carboxylates (2)-(5) and the corresponding pyrrolo homologue (6) exist in the form of E-isomers whereas the azepino[1,2-a]pyrimidine derivative (7) appears as an equilibrium mixture of Z- and E-isomers. On the basis of 15N chemical shifts an analogous tautomeric structure has been established for the 9-dimethylaminomethylene derivatives (2)-(7) and the ethyl 9-arylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidine-3-carboxylates (8)-(12) as well. 15N Shifts were sensitively affected by the Z-E isomerism and structural changes in remote parts of the molecule, too. Protonation of compounds (2)-(12) takes place on the N(1) atom, forming a 1,6,7,8-tetrahydro structure.

Original languageEnglish
Pages (from-to)1409-1412
Number of pages4
JournalJournal of the Chemical Society, Perkin Transactions 2
Issue number9
DOIs
Publication statusPublished - 1983

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Nitrogen Compounds
Isomers
Derivatives
Protonation
Chemical shift
Atoms
Molecules
pyrimidine

ASJC Scopus subject areas

  • Chemistry(all)

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title = "Nitrogen bridgehead compounds. Part 29. Tautomerism and Z-E isomerism of ethyl 9-aminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3- carboxylates and their homologues",
abstract = "1H and 13C n.m.r. studies have proved that ethyl 9-dimethylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidine-3-carboxylates (2)-(5) and the corresponding pyrrolo homologue (6) exist in the form of E-isomers whereas the azepino[1,2-a]pyrimidine derivative (7) appears as an equilibrium mixture of Z- and E-isomers. On the basis of 15N chemical shifts an analogous tautomeric structure has been established for the 9-dimethylaminomethylene derivatives (2)-(7) and the ethyl 9-arylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidine-3-carboxylates (8)-(12) as well. 15N Shifts were sensitively affected by the Z-E isomerism and structural changes in remote parts of the molecule, too. Protonation of compounds (2)-(12) takes place on the N(1) atom, forming a 1,6,7,8-tetrahydro structure.",
author = "G{\'a}bor T{\'o}th and A. Sz{\"o}ll{\"o}sy and Benjamin Pod{\'a}nyi and I. Hermecz and {\'A}gnes Horv{\'a}th and Zolt{\'a}n M{\'e}sz{\'a}ros and I. Bitter",
year = "1983",
doi = "10.1039/P29830001409",
language = "English",
pages = "1409--1412",
journal = "Journal of the Chemical Society, Perkin Transactions 2",
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TY - JOUR

T1 - Nitrogen bridgehead compounds. Part 29. Tautomerism and Z-E isomerism of ethyl 9-aminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a]pyrimidine-3- carboxylates and their homologues

AU - Tóth, Gábor

AU - Szöllösy, A.

AU - Podányi, Benjamin

AU - Hermecz, I.

AU - Horváth, Ágnes

AU - Mészáros, Zoltán

AU - Bitter, I.

PY - 1983

Y1 - 1983

N2 - 1H and 13C n.m.r. studies have proved that ethyl 9-dimethylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidine-3-carboxylates (2)-(5) and the corresponding pyrrolo homologue (6) exist in the form of E-isomers whereas the azepino[1,2-a]pyrimidine derivative (7) appears as an equilibrium mixture of Z- and E-isomers. On the basis of 15N chemical shifts an analogous tautomeric structure has been established for the 9-dimethylaminomethylene derivatives (2)-(7) and the ethyl 9-arylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidine-3-carboxylates (8)-(12) as well. 15N Shifts were sensitively affected by the Z-E isomerism and structural changes in remote parts of the molecule, too. Protonation of compounds (2)-(12) takes place on the N(1) atom, forming a 1,6,7,8-tetrahydro structure.

AB - 1H and 13C n.m.r. studies have proved that ethyl 9-dimethylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidine-3-carboxylates (2)-(5) and the corresponding pyrrolo homologue (6) exist in the form of E-isomers whereas the azepino[1,2-a]pyrimidine derivative (7) appears as an equilibrium mixture of Z- and E-isomers. On the basis of 15N chemical shifts an analogous tautomeric structure has been established for the 9-dimethylaminomethylene derivatives (2)-(7) and the ethyl 9-arylaminomethylene-4-oxo-6,7,8,9-tetrahydro-4H-pyrido[1,2-a] pyrimidine-3-carboxylates (8)-(12) as well. 15N Shifts were sensitively affected by the Z-E isomerism and structural changes in remote parts of the molecule, too. Protonation of compounds (2)-(12) takes place on the N(1) atom, forming a 1,6,7,8-tetrahydro structure.

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