Synthesis and structure of ethyl 2-[(4-oxo-3-phenyl-3,4-dihydroquinazolin-2-yl)sulfanyl]acetate

In the title compound, C18H16N2O3S, the dihedral angle between the mean planes of the quinazoline and phenyl rings is 86.83 (5)°. In the crystal, C—H⋯O interactions link the molecules into infinite columns along the b-axis direction. Parallel columns interact by additional C—H⋯O hydrogen bonds.

As shown in Fig. 1, 2-mercapto-3-phenylquinazolin-4(3H)one (3) was obtained by the reaction of anthranilic acid (1) and phenyl isothiocyanate (2) (Nguyen et al., 2019). The IR spectrum of (3) shows the stretching vibrations of N-H (3217 and 3134 cm À1 ) and C O (1659 cm À1 ) bonds, indicating that (3) exists in the thione form (Al-Majidi & Al-Khuzaie, 2015). In the 1 H NMR spectrum, besides signals of nine protons in the aromatic area, there is a singlet signal with the intensity of 1H at 13.05 ppm attributed to the proton of the thiol group. In an alkaline medium, (3) exists in the thiolate form and reacts easily with ethyl chloroacetate to yield (4). In the IR spectrum of (4), the disappearance of the NH stretching and the presence of a strong C O absorption at 1732 cm À1 indicate the existence of an ester compound. In the 1 H NMR spectrum of (4), the signal at 13.05 ppm disappears and three new signals in the aliphatic area [singlet signal at 3.99 (2H), quartet signal at 4.15 (2H) and triplet signal at 1.23 ppm (3H)] are consistent with the presence of the -CH 2 COOCH 2 CH 3 moiety in (4).
As no X-ray crystallographic information is available for this ester, we have determined the crystal structure by singlecrystal X-ray diffraction and a Hirshfeld surface analysis has been performed to gain further insight into the intermolecular interactions.

Figure 2
The molecular structure of the title compound, showing the atomlabelling scheme and displacement ellipsoids at the 50% probability level. Methyl group C17B [occupancy 0.469 (13)] is shown in green.

Figure 1
Reaction scheme for the synthesis of the title compound (4).
In order to gain further insight into the intermolecular interactions, a Hirshfeld surface and two-dimensional fingerprint plots were calculated using CrystalExplorer (Turner et al., 2017). The Hirshfeld surface mapped over d norm (Fig. 6) shows the expected bright-red spots near atoms O14, O23, H7, H12B and H19 involved in the C-HÁ Á ÁO hydrogen-bonding interactions described above. In addition, the faint-red spots near atoms S11 and O14 indicate a short SÁ Á ÁO contact [3.2128 (16) Å ]. Small faint-red spots appear near atoms H8 and H17E are due to a short H8Á Á ÁH17E contact (2.352 Å ). The S11Á Á ÁH23 contact mentioned is only visible as a white spot, while a white region above the C18-C23 phenyl ring is present because of the proximity of atom H20. The distance between H20 and the centroid of this phenyl ring of 3.204 Å , however, is too long for a C-HÁ Á Á interaction. The fingerprint plots ( Fig. 7 Table 1 Hydrogen-bond geometry (Å , ). Symmetry codes: (i) Àx þ 3 2 ; y À 1 2 ; Àz þ 1 2 ; (ii) x; y þ 1; z.

Figure 4
View of the crystal packing of the title compound along the [010] direction. Only the major component of the disordered C17 methyl group is shown.

Figure 5
Partial crystal packing of the title compound showing two parallel columns running in the [010] direction. Intermolecular C-HÁ Á ÁO interactions are shown as red dashed lines (see Table 1 for details), C-HÁ Á ÁS interactions as yellow dashed lines. Only the major component of the disordered C17 methyl group is shown.

Synthesis and crystallization
Anthranilic acid, phenyl isothiocyanate and ethyl chloroacetate were purchased from Acros and used without purification. Melting points were measured in open capillary tubes on a Gallenkamp melting point apparatus. IR spectra (, cm À1 ) were recorded on FTIR-8400S-SHIMADZU spectrometer using KBr pellets. The NMR spectra were recorded on a Bruker Avance III spectrometer (500 MHz for 1 H NMR) using residual solvent DMSO-d 6 signals as internal reference.

Synthesis of 2-mercapto-3-phenylquinazolin-4-one (3):
Phenyl isothiocyanate (2) (0.1 mol) was added to the solution of anthranilic acid (1) (0.1 mol) and triethylamine (3.0 mL) in absolute ethanol (200 mL). The reaction mixture then was refluxed for 4 h. After cooling to room temperature, the reaction mixture was poured into cold water. The resulting solid was filtered and recrystallized from a mixture of DMF and water, then washed with cold ethanol to give the product

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The methyl group C17 is disordered over two positions with population parameters 0.531 (13) and 0.469 (13)]. The H atoms were placed in idealized positions and included as riding contributions with U iso (H) values of 1.2U eq or 1.5U eq of the parent atoms, with C-H distances of 0.93 (aromatic), 0.97 (CH 2 ) and 0.96 Å (CH 3 ). In the final cycles of refinement, two outliers were omitted.

Ethyl 2-[(4-oxo-3-phenyl-3,4-dihydroquinazolin-2-yl)sulfanyl]acetate
Crystal data where P = (F o 2 + 2F c 2 )/3 (Δ/σ) max < 0.001 Δρ max = 0.14 e Å −3 Δρ min = −0.22 e Å −3 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.