Crystal structure and Hirshfeld surface analysis of 2-[(1,3-benzoxazol-2-yl)sulfanyl]-N-(2-methoxyphenyl)acetamide

In the title compound, there are two intramolecular N—H⋯O and N—H⋯N hydrogen bonds, forming S(5) and S(7) ring motifs, respectively. In the crystal, pairs of C—H⋯O hydrogen bonds link molecules into inversion dimers with (14) ring motifs, stacked along the b-axis direction. The inversion dimers are linked by C—H⋯π and π–π-stacking interactions, forming a three-dimensional network.


Chemical context
As a part of our ongoing research on synthesis and screening of pharmacological activities of compounds with a benzoxazole ring, which is known to produce a wide range of biological activities (Aggarwal et al., 2017;Gautam et al., 2012), we have focused on the synthesis of 3-substituted benzoxazolone-2-thione and S-substituted benzoxazole-2-thiol derivatives. It is well known that alkylation of benzoxazolone-2-thione leads to the S-alkylated derivatives instead of N-alkylated ones (Xiang et al., 2012;Rakse et al., 2013;Yurttaş et al., 2015). In this manner, the title compound was synthesized as a member of the target S-substituted benzoxazole-2-thiol series. The title compound is listed in the literature with registry number CASRN 331966-95-1 but corresponding scientific reference data are not available.

Supramolecular features
In the crystal, pairs of C-HÁ Á ÁO hydrogen bonds link the molecules into inversion dimers with R 2 2 (14) ring motifs, stacking along the b-axis direction. These dimers are linked by C-HÁ Á Á (Table 1, (2) and 3.631 (2) Å between the centroids of the five-and opposite six-membered rings of the 1,3-benzoxazole ring system of adjacent molecules], forming a three-dimensional network (Fig. 3).

Hirshfeld surface analysis
In order to explore the role of weak intermolecular interactions in the crystal packing, Hirshfeld surfaces (d norm ) and the related two-dimensional fingerprint plots were generated using CrystalExplorer17.5 (Spackman & Jayatilaka, 2009;Wolff et al., 2012). The three-dimensional molecular Hirshfeld surfaces were generated using a high standard surface reso- The molecular structure of the title compound, showing the atom labelling and displacement ellipsoids drawn at the 30% probability level. Intramolecular hydrogen bonds are shown as dashed lines. Table 1 Hydrogen-bond geometry (Å , ).

Figure 3
Packing diagram of the title compound viewed down the b axis.
lution over a colour scale of À0.1599 to 1.2011 a.u. for d norm (Fig. 4). The red spots in the Hirshfeld surface represent short NÁ Á ÁH/HÁ Á ÁN and OÁ Á ÁH/HÁ Á ÁO contacts. On the shape-index surface ( Fig. 5), convex blue regions represent hydrogendonor groups and concave red regions represent hydrogenacceptor groups. In addition, concave red regions represent C-HÁ Á Á andinteractions. The bright-red spots indicate their roles as the respective donors and/or acceptors; they also appear as blue and red regions corresponding to positive and negative potentials on the Hirshfeld surface mapped over electrostatic potential (Spackman et al., 2008) shown in Fig. 6. The blue regions indicate the positive electrostatic potential (hydrogen-bond donors), while the red regions indicate the negative electrostatic potential (hydrogen-bond acceptors).

Figure 5
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 6
Hirshfeld surfaces for the title compound, mapped with shape-index. percentage contributions to the Hirshfeld surface of the various interatomic contacts are given in Table 3. In the crystals of JARPOK and JARPUQ, molecules are linked by pairs of N-HÁ Á ÁN hydrogen bonds, forming inversion dimers with R 2 2 (8) ring motifs. In the crystal of JARPOK, the dimers are linked by bifurcated N-HÁ Á Á(O,O) and C-HÁ Á ÁO hydrogen bonds, forming layers parallel to (100). In the crystal of JARPUQ, the dimers are linked by N-HÁ Á ÁO hydrogen bonds, also forming layers parallel to (100). The layers are linked by C-HÁ Á ÁF hydrogen bonds, forming a three-dimensional architecture.

Database survey
In the crystal of GOKWIO, molecules are linked via pairs of N-HÁ Á ÁN hydrogen bonds, forming inversion dimers with an R 2 2 (8) ring motif. The dimers are linked by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, forming sheets parallel to (100).
In the crystals of JAXFIA and JAXFOG, a pair of N-HÁ Á ÁN hydrogen bonds links the molecules, forming inversion dimers with R 2 2 (8) ring motifs. In JAXFIA, the dimers are linked by N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds, enclosing R 2 1 (14), R 2 1 (11) and R 2 1 (7) ring motifs, forming layers parallel to the (100) plane. There is also an N-HÁ Á Á interaction present within the layer. In JAXFOG, the inversion dimers are linked by N-HÁ Á ÁO hydrogen bonds enclosing an R 4 4 (18) ring motif. The presence of N-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds generate an R 2 1 (6) ring motif. The combination of these various hydrogen bonds results in the formation of layers parallel to the (111) plane.
In the crystal of PAXTEP, molecules are consolidated in the form of polymeric chains along [010] as a result of N-HÁ Á ÁO hydrogen bonds, which generate R 3 2 (18) and R 4 3 (22) loops. The polymeric chains are interlinked through C-HÁ Á ÁO interaction and complete R 2 2 (8) ring motifs.

Synthesis and crystallization
The starting materials, 2-mercaptobenzoxazole and -chloro-N-(o-methoxyphenyl)acetamide, were synthesized according to literature methods (Maske et al., 2012;Ren et al., 2015). For the synthesis of the title compound, 2-mercaptobenzoxazole (1 eq) and -chloro-N-(o-methoxyphenyl) acetamide (1 eq) were heated in acetone under reflux for 1.5 h in the presence of K 2 CO 3 (1 eq). The reaction mixture was then cooled to room temperature and cold water was added until precipitation was complete.  Table 2 Summary of selected short interatomic contacts (Å ) in the title compound.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 4. All H atoms were positioned with idealized geometry and refined as riding: N-H = 0.86 Å , C-H = 0.93-0.97 Å with U iso (H) = 1.5U eq (C) for methyl H atoms and U iso (H) = 1.2U eq (C, N) for all other H atoms. Thirty one outliers (13 1 3), (14 1 1) Data collection: APEX2 (Bruker, 2007); cell refinement: SAINT (Bruker, 2007); data reduction: SAINT (Bruker, 2007); program(s) used to solve structure: SHELXT2014/5 (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/1 (Sheldrick, 2015b); molecular graphics: ORTEP-3 for Windows (Farrugia, 2012); software used to prepare material for publication: PLATON (Spek, 2009) and WinGX (Farrugia, 2012). 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.