Synthesis and structure of regioisomeric amino enones containing 2-pyridyl and CF substituents

Regioisomeric amino enones (Z)-4-amino-1,1,1-trifluoro-4-(2-pyridyl)but-3-en-2-one and (Z)-3-amino-4,4,4-trifluoro-1-(2-pyridyl)but-2-en-1-one were synthesized by the reaction of lithium (Z)-1,1,1-trifluoro-4-oxo-4-(2-pyridyl)but-2-en-2-olate with ammonium acetate in glacial AcOH. A comparative study of physicochemical properties and the crystal structures showed that the molecules of these new compounds are planar (except for two fluorine atoms) with an U-shaped configuration of the keto enamine moiety. A change in the position of the amino group with respect to the CF substituent leads to significant changes in the electron density distribution and the C-C bond lengths in the keto enamine moiety and also in the character of intermolecular hydrogen bonds responsible for the crystal packing mode of regioisomeric amino enones.