Report No xxxx - Instytut Fizyki JÄ drowej PAN

STRUCTURE OF 4-QUINOLINONES ANALYSED BY NMR STUDY
AND X-RAY DATA
Andrzej Zięba a , Andrzej Maślankiewicz a , Jerzy Sitkowski b , Bohdan Kamieński c ,
Kinga Suwińska d
a Department of Organic Chemistry, The Medical University of Silesia, Jagiellońska 4,
41-200 Sosnowiec; b Institute of Drugs, 30/34 Chełmska, 00-725 Warsaw; c Institute of
Organic Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw; d Institute
of Physical Chemistry, Polish Academy of Sciences, Kasprzaka 44/52, 01-224 Warsaw
The previous study on 1-ethyl-3-methylthio-4(1H)-quinolinethione 1 and 1-methyl-
4(1H)-pyridinethione 2 performed with the use of 14 N NMR spectroscopy (in CDCl 3 solution)
and with X-ray examination led us to the conclusion that the compounds 1 and 2 do not exist
in the form of azinethiones, but they exist as 1-alkylazinium-4-thiolates 4 or 5. 1,2
O
_
O
N
R
N
R
+
14 N NMR spectral data (in CDCl 3 solution) of 1-methyl-4(1H)-quinolinone 3 reveals nitrogen
atom signal (δ=-220 ppm) with half-height of linewidths ∆v 1/2 =286 Hz. It suggests for
pyridinium-type resonance form 4 as the major contributor to the real molecular structure of
3. X-ray examination of 3 shows the planarity of pyridine ring in 3 including the planarity
around the endocyclic-nitrogen indicating for sp 2 hybridization of nitrogen N 1 . Planar
tricoordinated nitrogen should bear a positive charge, and pyridinium-type resonance form 4
should be major contributor to the real molecular structure of 3. The same structural features
of pyridine unit (as concluded from CCDB) were observed also in the case of numerous
compounds with 4-quinolinone formula including potent antibacterial drugs. The 1 H, 13 C, 15 N
NMR study in the solid state and the solution of 3 in DMSO and those of ciprofloxacine
confirmed the mentioned above conclusion.
1. A.Maślankiewicz, A.Zięba, K.Suwińska, J.Chem.Crystallogr., 28, 701 (1998).
2. A.Zięba, A.Maślankiewicz, K.Suwińska, Acta Crystallogr., C58, 32 (2002).
3. A.Zięba, A.Maślankiewicz, V.Milata, J.Sitkowski, Magn. Reson. Chem., 41, 639, (2003)
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