title: 1H, 13C and 15N NMR spectral analysis of substituted 1,2,3,4-tetrahydro-pyrido[1,2-a]pyrimidines.
abstract: The NMR spectroscopic data of a series of thirty-four 3-acylpyrido[1,2-a]pyrimidinium salts are analyzed, which were prepared as either perchlorates or chlorides. Methyl group substituted 3-aroyltetrahydropyrido[1,2-a]pyrimidines with the methyl substituent in positions 6, 8 and 9 as well as both in positions 6 and 8 were investigated bearing various aroyl substituents. Unequivocal assignment of all resonances was achieved via two-dimensional (1)H,(1)H-COSY measurements, (1)H,(13)C and (1)H,(15)N HSQC as well as HMBC experiments, and important diagnostic CH and NH couplings in the heteroaromatic ring system are evaluated. The influence of the methyl substituents was analyzed on the proton, carbon and nitrogen shifts. A significant effect of the counter ion on some chemical shifts of the nuclei under discussion of the pyridopyrimidines is found, allowing the indirect detection of the anion, which is confirmed by direct measurement of the (35)Cl nucleus of the perchlorates.
authors.affiliation: Pharmaceutical Institute, Department of Pharmaceutical Chemistry, Christian-Albrechts-University of Kiel, Gutenbergstraße 76, D-24118, Kiel, Germany.
authors.forename: Ulrich
authors.initials: U
authors.lastname: Girreser
authors.forename: Ullvi
authors.initials: U
authors.lastname: Bluhm
authors.forename: Bernd
authors.initials: B
authors.lastname: Clement
authors.forename: Dieter
authors.initials: D
authors.lastname: Heber
mesh_terms: D002244:Carbon / Q000737:chemistry*; D002247:Carbon Isotopes; D002712:Chlorides / Q000737:chemistry; D009682:Magnetic Resonance Spectroscopy; D009584:Nitrogen / Q000737:chemistry*; D009587:Nitrogen Isotopes; D010472:Perchlorates / Q000737:chemistry; D011522:Protons; D011743:Pyrimidines / Q000737:chemistry*
chemical_list: D002247:Carbon Isotopes; D002712:Chlorides; D009587:Nitrogen Isotopes; D010472:Perchlorates; D011522:Protons; D011743:Pyrimidines; D002244:Carbon; D009584:Nitrogen
keywords: 13C NMR; 15N NMR; 1H NMR; 35Cl NMR; NMR spectroscopy; counter ion effects; pyrido[1,2‐a]pyrimidines; structure analysis