β-Enaminones have been widely studied because they can be found in biological systems such as proteins [1]. Additionally, they are applied as psychoactive drugs [2]. These compounds, theoretically, are capable of forming three different tautomers at equilibrium, i.e., iminoketone, aminoketone, and iminoenol forms. Existence of intramolecular hydrogen bond (IHB) is one of the important characteristics of them. This is an asymmetric hydrogen bond (i.e., N-H···O or O-H···N) which is significantly weaker than the corresponding homonuclear O-H···O bonds in β-diketones [3]. The aim of the present work is to investigate the stable conformations of methyl 3-aminocrotonate (MAC) using density functional theory (DFT). The results are compared with the corresponding ones for a simpler molecule, i.e., 4-amino-3-penten-2-one (APO).

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