Steric structure of 3-(5-phenyl-1H-pyrazol-3-yl)coumarins

Steric structure of two 3-(5-phenyl-1H-pyrazol-3-yl)coumarins have been studied by 1H and 13C NMR spectroscopy, X-ray powder diffraction and DFT calculations. According to the 1H NMR spectra, the studied 3-(5-phenyl-1H-pyrazol-3-yl)coumarins in DMSO‑d6 exist as an equilibrium mixture of enamine taut...

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Bibliographic Details
Published in:Journal of molecular structure 2020-05, Vol.1207, p.127765, Article 127765
Main Authors: Traven, V.F., Cheptsov, D.A., Solovjeva, N.P., Ivanov, I.V., Kalmykov, K.B., Chernyshev, V.V.
Format: Article
Language:English
Subjects:
DFT calculations
NMR spectroscopy
Pyrazoles
Tautomerism
X-ray powder diffraction
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Summary:Steric structure of two 3-(5-phenyl-1H-pyrazol-3-yl)coumarins have been studied by 1H and 13C NMR spectroscopy, X-ray powder diffraction and DFT calculations. According to the 1H NMR spectra, the studied 3-(5-phenyl-1H-pyrazol-3-yl)coumarins in DMSO‑d6 exist as an equilibrium mixture of enamine tautomeric forms. To identify the structural isomers, their two-dimensional HH spectra were recorded in the ROESY mode. The structure of the most stable tautomer is confirmed by the DFT calculations. This structure turned out to be the most advantageous in the solid state as well. Intramolecular hydrogen bond between NH of pyrazole ring and carbonyl group of coumarin moiety is suggested in the preferable enamine form. [Display omitted] •NMR spectra, X-ray powder diffraction, DFT calculations of 3-(5-phenyl-1H-pyrazol-3-yl)coumarins.•The predominant enamine tautomeric form both in solution and in solid state.•Intramolecular H-bond involving the proton of the NH (pyrazol) and CO (coumarin).
ISSN:0022-2860
1872-8014
DOI:10.1016/j.molstruc.2020.127765