Crystal structure and Hirshfeld surface analysis of N-(2,6-dimethylphenyl)-2-[3-hydroxy-2-oxo-3-(2-oxopropyl)indolin-1-yl]acetamide

The cup-shaped conformation of the title molecule is largely determined by an intramolecular N—H⋯O hydrogen bond. In the crystal, double layers of molecules are formed by O—H⋯O and C—H⋯O hydrogen bonds.


Structural commentary
The molecule adopts a cup-shaped conformation (Fig. 1), which is largely determined by the intramolecular N2-H2AÁ Á ÁO3 hydrogen bond ( Table 1). As this places O3 directly over the five-membered ring [O3Á Á Ácentroid = 2.7062 (8) Å , C10Á Á Ácentroid = 2.9956 (9) Å , C10 O3Á Á Á centroid = 99.56 (9) ], there is the possibility of an added C OÁ Á Á interaction reinforcing the observed conformation. The indole moiety is slightly non-planar as seen from the 1.89 (3) dihedral angle between the mean planes of its constituent rings. The dihedral angle between the mean plane of the C1/C6/C7/C8/N1 ring and that of the C12/C13/N2/O4 unit is 82.83 (5) while that between the latter plane and the mean plane of the C14-C19 ring is 72.24 (4) . All bond distances and bond angles appear as expected for the given formulation.

Supramolecular features
In the crystal, centrosymmetric dimers are formed by selfcomplementary O1-H1Á Á ÁO2 hydrogen bonds (Table 1) and these units are assembled into corrugated layers parallel to the bc plane by C3-H3Á Á ÁO4 hydrogen bonds (Table 1 and Fig. 2). Although these layers clearly contain large pores, they are combined in pairs across centers of symmetry by C9-H9AÁ Á ÁO4, C11-H11BÁ Á ÁO4 and C12-H12AÁ Á ÁO1 hydrogen bonds (Table 1) so that the pores in one layer are capped by molecules in the second and the resulting double layer has no significant pores (Fig. 3).

Figure 2
A plan view of a portion of one layer viewed along the a-axis direction. O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds are depicted, respectively, by red and black dashed lines while intramolecular interactions and noninteracting hydrogen atoms are omitted for clarity.

Figure 3
Packing viewed along the b-axis direction with O-HÁ Á ÁO and C-HÁ Á ÁO hydrogen bonds depicted, respectively, by red and black dashed lines. Intramolecular interactions and non-interacting hydrogen atoms are omitted for clarity.

Figure 1
The title molecule with labeling scheme and 50% probability ellipsoids. The intramolecular N-HÁ Á ÁO hydrogen bond and C OÁ Á Áring interaction are depicted, respectively by violet and light-blue dashed lines.
ODUWIV (Duan et al., 2013), PUZBAQ (Becerra et al., 2020), PUZBEU (Becerra et al., 2020), PUZBIY (Becerra et al., 2020) and PUZBOE (Becerra et al., 2020)] are most similar to the title molecule having a -carbonyl group in the substituent attached to the saturated carbon of the five-membered ring. As in the title compound, all of these form dimers through complementary O-HÁ Á ÁO hydrogen bonds between the hydroxy and keto groups and these units are also further assembled into chains and/or layers by hydrogen-bonding interactions.

Hirshfeld surface analysis
The analysis was performed with CrystalExplorer 21.5 (Spackman et al., 2021) with the details of the pictorial output described in a recent publication (Tan et al., 2019). Fig. 4 shows the d norm surface for the asymmetric unit plotted over the limits À0.6060 to 1.5193 a.u. together with three adjacent molecules that are hydrogen-bonded to it. The one on the lower left, adjacent to the pair of intense red spots, is the second half of one inversion dimer with these red spots indicating the strong O1-H1Á Á ÁO2 hydrogen bonds (cf. Fig. 2). The molecules above and below the surface are members of two adjacent layers of molecules (cf. Fig. 3), which are linked by the C9-H9AÁ Á ÁO4 hydrogen bonds (lighter red spots). Fig. 5a presents a fingerprint plot of all intermolecular interactions while Fig. 5b shows the 55.2% of these attributable to HÁ Á ÁH interactions. Fig. 5c and 5d delineate the OÁ Á ÁH/HÁ Á ÁO (24.1%) and CÁ Á ÁH/HÁ Á ÁC (17.8%) interactions, respectively.

Synthesis and crystallization
Indoline-2,3-dione (0.1g, 0.0679 mmol) was taken up in 10 mL of acetone under stirring. Solid potassium carbonate (0.11 g, 0.815 mmol) was added in one portion. Then, the dark-colored suspension was raised to room temperature and stirred for a further 1 h. The appropriate 2-chloro-N-(2,6-dimethylphenyl)acetamide (0.119 g, 0.0679 mmol) and potassium iodide (0.05 g, 0.301 mmol) were added. Then, the reaction mixture was stirred at 353.15-373 K for 2 h until the reaction was complete, which was confirmed using TLC (ethyl acetate:hexane, 40:60). The resulting solid was filtered and recrystallized from ethanol to give title compound as colorless crystals. Yield: 64%; m.p. 527.15-529.15 K. FT-IR (ATR, ,   The Hirshfeld surface for the title molecule with three close neighbors added.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. Hydrogen atoms attached to carbon were included as riding contributions in idealized positions (C-H = 0.95-0.99 Å ) with isotropic displacement parameters tied to those of the attached atoms [U iso (H) = 1.2-1.5U eq (C)]. Those attached to nitrogen and to oxygen were placed in locations derived from a difference map and refined with DFIX 0.91 0.01 and DFIX 0.84 0.01 instructions, respectively.  N-(2,6-dimethylphenyl) program(s) used to solve structure: SHELXT (Sheldrick, 2015a); program(s) used to refine structure: SHELXL2018/1 (Sheldrick, 2015b); molecular graphics: DIAMOND (Brandenburg & Putz, 2012); software used to prepare material for publication: SHELXTL (Sheldrick, 2008).

Special details
Experimental. The diffraction data were obtained from 9 sets of frames, each of width 0.5° in ω or φ, collected with scan parameters determined by the "strategy" routine in APEX3. The scan time was 5 sec/frame. 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. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2sigma(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger. H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 -0.99 Å) and were included as riding contributions with isotropic displacement parameters 1.2 -1.5 times those of the attached atoms. Those attached to nitrogen and to oxygen were placed in locations derived from a difference map and refined with DFIX 0.91 0.01 and DFIX 0.84 0.01 instructions, respectively.