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

In the crystal, N—H⋯O hydrogen bonds link the molecules into dimers with an (16) ring motif. Further N—H⋯O and N—H⋯N hydrogen bonds connect the dimers into chains along the c-axis direction. C—Br⋯π and C=O⋯π interactions stabilize the molecular packing, resulting in a three-dimensional network.


Figure 2
A general view of the N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds in the structure of the title compound.

Hirshfeld surface analysis
To visualize the intermolecular interactions for both independent molecules A and B, CrystalExplorer17 (Turner et al., 2017)    The crystal packing of the title compound viewed down the b axis, showing chains running along the c axis formed through N-HÁ Á ÁO and N-HÁ Á ÁN hydrogen bonds.

Figure 5
The crystal packing of the title compound viewed down the c axis, with intermolecular N-HÁ Á ÁO, C-HÁ Á ÁN and N-HÁ Á ÁN hydrogen bonds.

Figure 6
The C-BrÁ Á Á and C OÁ Á Á interactions in the structure of the title compound viewed down the a axis.

Figure 9
The two-dimensional fingerprint plots [(a)  of H atoms, CÁ Á ÁH/HÁ Á ÁC, OÁ Á ÁH/HÁ Á ÁO, BrÁ Á ÁH/HÁ Á ÁBr and NÁ Á ÁH/HÁ Á ÁN contacts are also substantial. Table 3 gives the contributions of the other, less significant contacts. The fact that the same type of interactions provide different contributions to the Hirshfeld surface for molecules A and B can be attributed to the different environments of these molecules in the crystalline state.  (Suresh et al., 2007) and SETWOE (Suresh et al., 2007) closely resemble the title compound.

Database survey
In OZAKOS (space group: Pc), the molecular conformation of the title compound is stabilized by an intramolecular O-HÁ Á ÁO hydrogen bond, forming 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 both the related salts, JEBREQ (space group: P1) and JEBRAM (space group: P1), the N atom in the 1-position of the pyrimidine ring is protonated. In the hydrated salt JEBREQ, the presence of the water molecule prevents the formation of the familiar R 2 2 (8) ring motif. Instead, an expanded ring [i.e. R 3 2 (8)] is formed involving the sulfonate group, the pyrimidinium cation and the water molecule. Both salts form a supramolecular homosynthon [R 2 2 (8) ring motif] through N-HÁ Á ÁN hydrogen bonds. The molecular structures are further stabilized bystacking, and C=OÁ Á Á, C-HÁ Á ÁO and C-HÁ Á ÁCl interactions. It appears that the protonation state of the pyrimidine ring influences the intermolecular interactions within the crystal lattice to a substantial extent. In JEBRAM, the protonated N atom and the amino group of the pyrimidinium cation interact with the carboxylate group of the anion through N-HÁ Á ÁO hydrogen bonds, forming a heterosynthon with an R 2 2 (8) ring motif. The polysubstituted pyridines, SETWUK (space group: P2 1 /n) and SETWOE (space group: P2 1 /c), adopt nearly planar structures. The crystal structure of SETWUK is stabilized by intermolecular C-HÁ Á ÁF and C-HÁ Á Á interactions. The C-HÁ Á ÁF bond generates a linear chain with a C(14) motif. The crystal structure of SETWOE is stabilized by intermolecular C-HÁ Á ÁO and C-HÁ Á Á interactions. The C-HÁ Á ÁO hydrogen bonds generate rings with R 2 2 (14) and R 2 2 (20) motifs. In addition, in SETWOE and SETWUK, intramolecular O-HÁ Á ÁO interactions are found, which generate an S(6) graph-set motif. No significant aryl-aryl orinteractions exist in these structures. All this bears some resemblance to the title compound.

Synthesis and crystallization
To a solution of 2-(4-bromobenzylidene)malononitrile (1.19 g; 5.1 mmol) and acetoacetanilide (0.92 g; 5.2 mmol) in methanol (25 mL), piperidine (2-3 drops) was added and the mixture was stirred at room temperature for 48 h. Then 15 mL of methanol were removed by rotary evaporation from the reaction mixture, which was left overnight. The precipitated crystals were separated by filtration and recrystallized from ethanol/water (1:1)

Refinement details
Crystal data, data collection and structure refinement details are summarized in Table 4. All H atoms were positioned geometrically (N-H = 0.90 Å , C-H = 0.95-1.00 Å ) and refined as riding with U iso (H) = 1.2U eq (C, N) or 1.5U eq (Cmethyl).    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. Refinement. Refined as a two-component inversion twin.