Intramolecular hydrogen bond in the push–pull CF3-aminoenones: DFT and FTIR study, NBO analysis

Postulated conformers of trifluoromethylated β-aminoenones stabilized by intramolecular NH⋯O and N⋯HO bonds were studied by IR and NMR spectroscopy and evaluated with quantum chemical calculations (B3LYP/6-311+G(d,p), MP2/6-311+G(d,p)//B3LYP/6-311+G(d,p) and MP2/6-31G(d,p)) and NBO analysis. The influence of the nature of EWG, substituents at the nitrogen atom and double bond, and of orbital interactions of heteroatoms and double bonds in these structures on the proton affinity of basic and acid centers, strength of hydrogen bonds, and the energy of tautomeric transfers is discussed. The theoretical results agree satisfactorily with the experimental observations.