Crystal structure and Hirshfeld surface analysis of 2-amino-4-(4-methoxyphenyl)-6-oxo-1-phenyl-1,4,5,6-tetrahydropyridine-3-carbonitrile

In the crystal, strong C—H⋯O and N—H⋯N hydrogen bonds form dimers with (14) and (12) ring motifs between adjacent molecules along the c-axis direction. Intermolecular N—H⋯O and C—H⋯O hydrogen bonds connect these dimers to form a three-dimensional network. In addition, C—H⋯π interactions and π–π stacking interactions help to stabilize the packing.


Chemical context
Carbon-carbon and carbon-nitrogen bond-forming reactions represent an important synthetic class in organic chemistry (Yadigarov et al., 2009;Abdelhamid et al., 2011;Yin et al., 2020;Khalilov et al., 2021). Notably, pyridine derivatives are widely applied in the discovery of biologically active molecules and multifunctional materials (Magerramov et al., 2018;Sherman & Murugan, 2015;Mamedov et al., 2020). On the other hand, the tetrahydropyridine moiety is an essential part of diverse biologically active compounds, food additives and natural products (Mateeva et al., 2005).

Figure 3
The crystal packing of the title compound, viewed along the b axis, showing the N-HÁ Á ÁN, N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds as dashed lines.

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level.

Figure 5
The crystal packing of the title compound, viewed along the b axis, showing the C-HÁ Á Á interactions andstacking interactions as dashed lines.
Compound (I) crystallizes in the monoclinic space group Pc with Z = 4, and with two molecules, A and B, in the asymmetric unit. These molecules are stereoisomers with an R,R absolute configuration at C3 and C4 in molecule A, whereas the corresponding atoms in B, C23 and C24, have an S configuration. In both molecules, the conformation of the central dihydropyridine ring is close to screw-boat. The molecular conformation is stabilized by N-HÁ Á ÁO hydrogen bonds, forming a dimer with an R 2 2 (16) ring motif. Both molecules of the dimers are connected by intermolecular N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds with an R 3 2 (14) ring motif into chains along the c-axis direction. Furthermore C-BrÁ Á Á and C OÁ Á Á stacking interactions between these ribbons contribute to the stabilization of the molecular packing.
Compound (II) crystallizes in the monoclinic space group P2 1 /c with Z = 4 and the asymmetric unit comprises one molecule. The central tetrahydropyridine ring is almost planar with a maximum deviation of 0.074 (3) Å for C4. The phenyl and dichlorophenyl rings are at an angle of 21.28 (15) . They form dihedral angles of 86.10 (15) and 87.17 (14) , respectively, with the central tetrahydropyridine ring. A strong intramolecular O2-H2Á Á ÁO1 hydrogen bond stabilizes the molecular conformation of the molecule, creating an S(6) ring motif. In the crystal, molecules are linked by intermolecular N-HÁ Á ÁN and C-HÁ Á ÁN hydrogen bonds, and N-HÁ Á Á and C-HÁ Á Á interactions, forming a three-dimensional network.
In molecule (III) (monoclinic space group P2 1 /c, Z = 4), the cis configuration of the pyridinyl-vinyl fragment is stabilized by a strong intramolecular N-HÁ Á ÁN hydrogen bond. The phenyl and pyridine rings are inclined to one another by 77.3 (1) . In the crystal, inversion dimers are present via pairs of C-HÁ Á ÁO hydrogen bonds and are further linked by C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions.   For compound (IV) (monoclinic space group C2/c, Z = 8), the molecules form dimers by means of a pair of N-HÁ Á ÁO hydrogen bonds. The 2(1H)-pyridone ring displays a screwboat conformation.

Synthesis and crystallization
To a solution of 2-(4-methoxybenzylidene)malononitrile (0.94 g; 5.1 mmol) and acetoacetanilide (0.92 g; 5.2 mmol) in methanol (25 mL), 3-4 drops of piperidine were added and the mixture was stirred at 328-333 K for 10 min and was kept at room temperature for 48 h. Then 15 mL of methanol were removed from the reaction mixture, which was left overnight. The precipitated crystals were separated by filtration and recrystallized from ethanol/water (1:1)

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.