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Synthesis and Structures of New Enaminones

Two isomeric enaminones were obtained by reaction of ethyl 2- hydroxy-4- (4-hydroxy-6-methyl-2H-pyran-2-on-3-yl)-4-oxo-2-butenoat (1) and amines (aniline, benzylamine, butylamine and tyramine) in ethanol. The structures of all isomers were studied by ^13^C and ^1^H NMR spectra, but in the case of isomers 2b, 3a and 4b from X-ray diffraction data. All three structures display very short intramolecular O-H...O and N-H...O bonds, reinforced by delocalization, and they are in addition stabilized by C-H...O weak hydrogen bonds. In 2b and 3a structures the discrete dimers are formed by eight-membered ring containing hydrogen bonds, while in 4a the infinite chains along [1 0 1] direction is formed.

enaminones; 2H-pyran-2-ones; NMR spectra; crystal structures; hydrogen bond; tautomeric form

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