Crystal structure and Hirshfeld surface analysis of 3-methyl-4-oxo-N-phenyl-3,4-dihydroquinazoline-2-carbothioamide

The crystal structure of the title compound comprises two independent molecules that mainly differ in the orientation of the phenyl ring to the rest of the molecule.

The asymmetric unit of the title compound, C 16 H 13 N 3 OS, comprises two molecules (A and B) with similar conformations that differ mainly in the orientation of the phenyl group relative to the rest of the molecule, as expressed by the C thioamide -N thioamide -C phenyl -C phenyl torsion angle of 49.3 (3) for molecule A and of 5.4 (3) for molecule B. In the crystal, two intermolecular N-HÁ Á ÁN hydrogen bonds lead to the formation of a dimer with R 2 2 (10) graph-set notation. A Hirshfeld surface analysis revealed that HÁ Á ÁH interactions are the most important intermolecular interactions, contributing 40.9% to the Hirshfeld surface.

Chemical context
Thioamides and their derivatives are important representatives of organic compounds containing a sulfur atom. The presence of bifunctional properties in thioamides, resulting from the presence of nitrogen and sulfur atoms, and their participation in reactions as electrophilic or nucleophilic reagents can lead to the formation of different heterocyclic compounds. Several review articles have been published on the syntheses, physico-chemical properties and applications of thioamides (Jagodziń ski, 2003;Belskaya et al., 2010;Koketsu & Ishihara, 2007;Krayushkin et al., 2004;Britsun et al., 2008).
One of the methods of choice for the synthesis of widely used thioamides is the Wilgerodt-Kindler reaction. As shown by previous studies, the Wilgerodt-Kindler reactions with 2-methylquinazoline-4-one went to the active methyl group in the position 2 and, accordingly, thioamides were synthesized in a series of quinazoline derivatives (Shakhidoyatov et al., 1997). Continuing our work in this direction, we have synthesized 2,3-dimethylquinazoline-4-one and studied the corresponding Wilgerodt-Kindler reactions.
During the reaction involving 2,3-dimethylquinazoline-4one, sulfur, aniline, the solvent dimethyl sulfoxide and the catalyst sodium sulfide, the reaction went to the active methyl group in position 2 and new thioamides of a number of derivatives of quinazoline-4-one were obtained. The synthesis and crystal structure of 3-methyl-4-oxo-N-phenyl-3,4-dihydroquinazoline-2-carbothioamide, C 16 H 13 N 3 OS, is reported here. Relevant intermolecular contacts were quantified by using Hirshfeld surface analysis.

Structural commentary
The title compound crystallizes with two molecules, A and B, in the asymmetric unit ( Fig. 1). In molecules A and B the orientations of the quinazoline ring system and the phenyl ring relative to the thioamide group differ, as shown by the values of the N3-C2-C10-S1 and C10-N11-C12-C13 torsion angles of 76.14 (19) and 49.3 (3) , respectively, in molecule A and 83.78 (19) and 5.4 (3) in molecule B. As a result, there are differences in the intramolecular distances between the sulfur and hydrogen atoms in molecules A and B. In molecule A, the contacts S1AÁ Á ÁH9AB and S1AÁ Á ÁH13A are 2.873 and 2.897 Å whereas the corresponding distances in molecule B are 3.054 and 2.578 Å . The phenyl and pyrimidine rings in both molecules are essentially coplanar, with r.m.s. deviations of 0.0225 and 0.0119 Å for molecule A and B, respectively. Fig. 2 shows that the pyrimidine moieties of the molecules are almost superimposable.

Figure 1
Asymmetric unit of the title compound with the atom-numbering scheme. Displacement ellipsoids for non-hydrogen atoms are drawn at the 30% probability level.

Figure 2
Overlay plot of the two independent molecules in the title compound.

Hirshfeld surface analysis
A Hirshfeld surface (HS) analysis (Spackman & Jayatilaka, 2009) was carried out using CrystalExplorer17.5 (Turner et al., 2017) to quantify and visualize intermolecular interactions in the crystal structure of the title compound. The HS mapped with d norm is represented in Fig. 6. 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 or longer, respectively, than the van der Waals radii. The twodimensional fingerprint plot for all contacts is depicted in Fig. 7a  A view of the crystal packing of the title compound along the a axis. Intermolecular hydrogen bonds and C-SÁ Á Á interactions are displayed by blue and green dotted lines, respectively.

Figure 5
View of the narrow channels formed along the b axis.

Figure 6
View of the three-dimensional Hirshfeld surface of the title compound plotted over d norm .  6. Synthesis and crystallization 0.435 g (0.0025 mol) of 2,3-dimethylquinazoline-4-one, 0.465 g (0.005 mol) of aniline, 0.24 g (0.0075 mol) of sulfur, 0.05 g of sodium sulfide (Na 2 SÁ9H 2 O) and 4 ml of dimethyl sulfoxide were injected into a round-bottomed flask with a volume of 100 ml. Then the reaction flask was heated to 403 K for 6 h. After the end of the reaction, the flask was cooled and 40 ml of an aqueous sodium hydroxide solution were added. The resulting mixture was filtered, then added to a dilute solution of sulfuric acid (pH 6). The formed precipitate was filtered off and recrystallized in methanol. In total, 0.5 g (64.0%) of the product were obtained, m.p. 481-483 K.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. C-bound H atoms were positioned geometrically, with C-H = 0.96 Å (for methylene H atoms) and C-H = 0.93 Å (for aromatic H atoms), and were refined with U iso (H) = 1.5U eq (C methyl ) and 1.2U eq (C), respectively. H atoms bonded to nitrogen were located in a difference-Fourier map, and their positional and isotropic displacement parameters were freely refined.
Acta Cryst. (2022). E78, 47-50 research communications  software used to prepare material for publication: publCIF (Westrip, 2010).  (Sheldrick, 2015a), Fc * =kFc[1+0.001xFc 2 λ 3 /sin(2θ)] -1/4 Extinction coefficient: 0.00124 (12) 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.