Synthesis, crystal structure and Hirshfeld surface analysis of 3-(4,4-dimethyl-2,3,4,5-tetrahydro-1H-1,5-benzodiazepin-2-ylidene)-6-methyl-3,4-dihydro-2H-pyran-2,4-dione

The title compound is built up from the benzodiazepine ring system linked to the pyridyl and pendant dihydropyran rings. In the crystal, N—H⋯O and C—H⋯O hydrogen bonds link the molecules into a three-dimensional network. A weak C—H ⋯ π interaction is also observed.


Figure 2
A partial packing diagram viewed along the a axis. N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds are shown as dashed lines. H atoms not involved in these interactions have been omitted for clarity.

Figure 1
The molecular structure of the title compound with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. N-H Diazp Á Á ÁO Dhydp and C-H Diazp Á Á ÁO Dhydp (Diazp = diazepine and Dhydp = dihydropyran) hydrogen bonds are shown as dashed lines.

Hirshfeld surface analysis
In order to visualize the intermolecular interactions in the crystal of the title compound, a Hirshfeld surface (HS) analysis (Hirshfeld, 1977;Spackman & Jayatilaka, 2009) was carried out by using CrystalExplorer17.5 (Turner et al., 2017). In the HS plotted over d norm (Fig. 3), the white surface indicates contacts with distances equal to the sum of van der Waals radii, and the red and blue colours indicate distances shorter (in close contact) or longer (distinct contact) than the van der Waals radii, respectively (Venkatesan et al., 2016). The brightred spots appearing near atoms O1 and O2 and hydrogen atoms H2, H12 and H16A indicate their roles as the respective donors and/or acceptors in the dominant N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds (Table 1); they also appear as blue and red regions corresponding to positive and negative potentials on the HS mapped over electrostatic potential (Spackman et al., 2008;Jayatilaka et al., 2005) shown in Fig. 4 where the blue regions indicate positive electrostatic potential (hydrogenbond donors) and the red regions indicate negative electrostatic potential (hydrogen-bond acceptors). The shape-index of the HS is a tool to visualize thestacking by the presence of adjacent red and blue triangles; if there are no adjacent red and/or blue triangles, then there are nointeractions. View of the three-dimensional Hirshfeld surface of the title compound plotted over electrostatic potential energy in the range À0.0500 to 0.0500 a.u. using the STO-3 G basis set at the Hartree-Fock level of theory. Hydrogen-bond donors and acceptors are shown as blue and red regions around the atoms, corresponding to positive and negative potentials, respectively.

Figure 5
Hirshfeld surface of the title compound plotted over shape-index. Table 2 Selected interatomic distances (Å ).

Figure 3
View of the three-dimensional Hirshfeld surface of the title compound plotted over d norm in the range À0.4583 to 1.6329 a.u.
crystal packing, which is reflected in Fig. 6b as widely scattered points of high density due to the large hydrogen content of the molecule. The spike with the tip at d e = d i = 1.14 Å in Fig. 6b is due to the short interatomic H Á Á Á H contacts (Table 2). In the presence of C-H Á Á Á interactions, the pair of wings in the fingerprint plot delineated into H Á Á Á C/C Á Á Á H contacts with 25.3% contribution to the HS show a nearly symmetrical distribution of points, Fig. 6c, with the thin edges at d e + d i $2.81 Å arising from the H Á Á Á C/C Á Á Á H contacts (Table 2). There is a pair of characteristic wings in the fingerprint plot delineated into HÁ Á ÁO/OÁ Á ÁH contacts, Fig. 6d: the 20.3% contribution to the HS arises from the N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds (Table 1) as well as from the HÁ Á ÁO/ OÁ Á ÁH contacts (Table 2) and is shown as a pair of spikes with the tips at d e + d i = 2.00 Å . Finally, the weak OÁ Á ÁO (Fig. 6e) and HÁ Á ÁN/NÁ Á ÁH (Fig. 6f) contacts in the structure contribute only 1.6 and 1.1%, respectively, to the HS. The Hirshfeld surface representations with the function d norm plotted onto the surface are shown for the HÁ Á ÁH, HÁ Á ÁC/CÁ Á ÁH and HÁ Á ÁO/OÁ Á ÁH interactions in Fig. 7a-c, respectively. The Hirshfeld surface analysis confirms the importance of H-atom contacts in establishing the packing. The large number of HÁ Á ÁH, HÁ Á ÁC/CÁ Á ÁH and HÁ Á ÁO/OÁ Á ÁH interactions suggest that van der Waals interactions and hydrogen bonding play the major roles in the crystal packing (Hathwar et al., 2015).

Synthesis and crystallization
A solution of dehydroacetic acid (0.168 g, 1 mmol) and ophenylenediamine (0.108 g, 1 mmol) in ethanol (40 ml) was refluxed for 1 h. After cooling to room temperature, the colourless intermediate solid compound, a mono-Schiff base, was obtained in 70% yield. The intermediate (0.5 g, 1 mmol) was refluxed in acetone (10 ml) for 1h. After cooling, the crystals formed were filtered and dried (yield: 65%).

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 3. N-and C-bound H atoms were positioned geometrically (N-H = 0.86 Å and C-H = 0.93, 0.97 and 0.96 Å for aromatic, methylene and methyl H atoms, respectively) and constrained to ride on their parent atoms, with U iso (H) = kU eq (N, C), where k = 1.5 for methyl H atoms and 1.2 for the other H atoms.

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.