On the Tautomerism of N-Substituted Pyrazolones: 1,2-Dihydro-3H-pyrazol-3-ones versus 1H-Pyrazol-3-ols

Eglė Arbačiauskienė; Sonata Krikštolaitytė; Aiva Mitrulevičienė; Aurimas Bieliauskas; Vytas Martynaitis; Matthias Bechmann; Alexander Roller; Algirdas Šačkus; Wolfgang Holzer

doi:10.3390/molecules23010129

On the Tautomerism of N-Substituted Pyrazolones: 1,2-Dihydro-3H-pyrazol-3-ones versus 1H-Pyrazol-3-ols

Molecules. 2018 Jan 9;23(1):129. doi: 10.3390/molecules23010129.

Authors

Eglė Arbačiauskienė¹, Sonata Krikštolaitytė², Aiva Mitrulevičienė³, Aurimas Bieliauskas⁴, Vytas Martynaitis⁵, Matthias Bechmann⁶, Alexander Roller⁷, Algirdas Šačkus^{8

9}, Wolfgang Holzer¹⁰

Affiliations

¹ Department of Organic Chemistry, Kaunas University of Technology, Radvilėnų pl. 19, LT-50254 Kaunas, Lithuania. egle.arbaciauskiene@ktu.lt.
² Department of Organic Chemistry, Kaunas University of Technology, Radvilėnų pl. 19, LT-50254 Kaunas, Lithuania. sonata.krikstolaityte@ktu.lt.
³ Department of Organic Chemistry, Kaunas University of Technology, Radvilėnų pl. 19, LT-50254 Kaunas, Lithuania. aiva.mitruleviciene@gmail.com.
⁴ Institute of Synthetic Chemistry, Kaunas University of Technology, K. Baršausko g. 59, LT-51423 Kaunas, Lithuania. aurimas.bieliauskas@ktu.lt.
⁵ Department of Organic Chemistry, Kaunas University of Technology, Radvilėnų pl. 19, LT-50254 Kaunas, Lithuania. vytas.martynaitis@ktu.lt.
⁶ Institute of Organic Chemistry, Johannes Kepler University Linz, Altenberger Straße 69, A-4040 Linz, Austria. matthias.bechmann@jku.at.
⁷ X-ray Structure Analysis Centre, Faculty of Chemistry, University of Vienna, Währinger Straße 42, A-1090 Vienna, Austria. alexander.roller@univie.ac.at.
⁸ Department of Organic Chemistry, Kaunas University of Technology, Radvilėnų pl. 19, LT-50254 Kaunas, Lithuania. algirdas.sackus@ktu.lt.
⁹ Institute of Synthetic Chemistry, Kaunas University of Technology, K. Baršausko g. 59, LT-51423 Kaunas, Lithuania. algirdas.sackus@ktu.lt.
¹⁰ Department of Pharmaceutical Chemistry, Faculty of Life Sciences, University of Vienna, Althanstrasse 14, A-1090 Vienna, Austria. wolfgang.holzer@univie.ac.at.

Abstract

The tautomerism of 1-phenyl-1,2-dihydro-3H-pyrazol-3-One was investigated. An X-ray crystal structure analysis exhibits dimers of 1-phenyl-1H-pyrazol-3-ol units. Comparison of NMR (nuclear magnetic resonance) spectra in liquid state (¹H, ¹³C, ¹⁵N) with those of "fixed" derivatives, as well as with the corresponding solid state NMR spectra reveal this compound to exist predominantly as 1H-pyrazol-3-ol molecule pairs in nonpolar solvents like CDCl₃ or C₆D₆, whereas in DMSO-d₆ the corresponding monomers are at hand. Moreover, the NMR data of different related 1H-pyrazol-3-ol derivatives are presented.

Keywords: 1,2-dihydro-3H-pyrazol-3-ones; 13C; 15N); 1H-pyrazol-3-ol; NMR (1H; X-ray structure analysis; prototropic tautomerism; solid state NMR.

MeSH terms

Crystallography, X-Ray / methods
Magnetic Resonance Spectroscopy / methods
Molecular Structure
Pyrazolones / chemistry*
Solvents / chemistry
Stereoisomerism
Structure-Activity Relationship

Substances

Pyrazolones
Solvents