Synthesis and Structure of Two Isomeric Enaminones

Brbot-Šaranović, Ana and Pavlović, Gordana and Vrdoljak, Višnja and Cindrić, Marina (2001) Synthesis and Structure of Two Isomeric Enaminones. Croatica Chemica Acta, 74 (2). pp. 441-454. ISSN 0011-1643

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The reaction of ethyl 2-hydroxy-4-(4-hydroxy-6-methyl-2H-pyran-2-on-3-yl)-4-oxo-2-butenoate (1) and 1-naphthylamine in ethanol affords two isomeric enaminones: ethyl 4-hydroxy-3-[3-(1-naphthyl-amino)-2-butenoyl]-2H-pyran-2-on-6-carboxylate (2) and ethyl 4-(4-hydroxy-6-methyl-2H-pyran-2-on-3-yl)-2-(1-naphthylamino)-4-oxo-2-butenoate (3). The structures of both compounds were determined by the single crystal X-ray diffraction. Tautomerism may be involved in two parts of a molecule, in the cyclic part (pyrone ring) and in the side chain, to give a variety of possible tautomeric forms. Attention has been turned to the endo-enol enamine and exo-enol enamine tautomeric equilibrium, since both tautomers were found in the crystals of compounds with similar structures. The NMR spectroscopic data and X-ray structural analysis confirmed that both compounds exist in the endo-enol enamine form in the solution and in the crystalline state. The molecules are characterized by strong, intramolecular hydrogen bonds of N–H O and O–H O type reinforced by π-delocalization. The molecules as a whole are not planar, exhibiting planarity only in the central heteroconjugated moiety, while naphthyl rings are almost perpendicular to the central part.

Item Type: Article
Keywords: enaminones;, 2H-pyran-2-ones; NMR spectra; crystal structures; resonance assisted hydrogen bonds; structure and tautomeric isomerism
Date: 2001
Subjects: NATURAL SCIENCES > Chemistry
Divisions: Faculty of Science > Department of Chemistry
Publisher: Hrvatsko kemijsko društvo
Related URLs:
Depositing User: mag. bibl. Ana Šafran
Date Deposited: 26 May 2014 08:11
Last Modified: 26 May 2014 08:11

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