Crystal structure and Hirshfeld surface analysis of N-[(2-hydroxynaphthalen-1-yl)(3-methylphenyl)methyl]acetamide

This compound crystallizes with two independent molecules (A and B) in the asymmetric unit. In the crystal, the A and B molecules stack head-to-tail in columns along the b-axis direction.

The title compound, C 20 H 19 NO 2 , is of interest as a precursor to biologically active substituted quinolines and related compounds. This compound crystallizes with two independent molecules (A and B) in the asymmetric unit. The dihedral angles between mean planes of the methylphenyl ring and the naphthalene ring system are 78.32 (6) and 84.70 (6) in molecules A and B, respectively. In the crystal, the antiferroelectric packing of molecules A and B is of an ABBAABB type along the b-axis direction. The crystal structure features N-HÁ Á ÁO, O-HÁ Á ÁO and weak C-HÁ Á ÁO hydrogen bonds, which link the molecules into infinite chains propagating along the b-axis direction.

Structural commentary
The molecular structure of the title compound is shown in Fig. 1. It crystallizes with two independent molecules (A and B) in the asymmetric unit, with Z = 8. The bond lengths in the methylphenyl rings and naphthalene ring systems of the two molecules are practically equal, while there are slight differences in bond angles, with for example N1-C7-C1 and N21-C27-C21 differing by 1.2 and the exocyclic angles C7-C11-C12 and C27-C211-C212 differing by 1.8 . The naphthalene ring systems are essentially planar with maximum deviations from the mean plane of 0.059 (1) Å (for C11) and À0.020 (1) and 0.020 (2) Å (for C211 and C213) in molecules A and B, respectively. The mean plane of the naphthalene ring system subtends a dihedral of angle of 78.32 (6) with the methylphenyl ring in molecule A and 84.70 (6) in B while the dihedral angles between the naphthalene ring system and the acetamide group is 55.98 (9) in molecule A and 65.30 (9) in B. This differences also exist between the mean plane of acetamide and phenyl rings which are about 80.63 (10) for molecule A and 84.51 (10) for molecule B. The methyl groups at C8 and C28 have a C-H bond eclipsed in the mean plane of the phenyl ring and they are oriented towards the acetamide group, as been observed in N-[(2-hydroxynaphthalen-1-yl)(4methylphenyl)methyl]acetamide (Khanapure et al., 2015). Intramolecular N-HÁ Á ÁO hydrogen bonds (Table 1) involving the hydroxyl O atoms result in the formation of pseudo six-membered rings in both molecules.

Supramolecular features
In the crystal, the anti-ferroelectric packing of molecules A and B is of an ABBAABB type (Fig. 2). Inversion-related molecules are lined by pairs of hydrogen bonds (Table 1), forming infinite chains along the b-axis direction. O-HÁ Á ÁC and C-OÁ Á ÁO short contacts are also present in the crystal (Table 2).

Analysis of the Hirshfeld surfaces
The Hirshfeld surface analysis (Spackman & Jayatilaka, 2009) and the associated two-dimensional fingerprint plots (McKinnon et al., 2007) were generated with CrystalExplorer 3.1 (Turner et al., 2017). The Hirshfeld surface of the compound mapped over d norm is illustrated in Fig. 3. The red spots in Fig. 4 correspond to close HÁ Á ÁH contacts resulting from the short O-HÁ Á ÁH contacts, and the white areas, representing distances between neighboring atoms close to the sum of the van der waals radii, indicate NÁ Á ÁH/HÁ Á ÁN interactions. Bluish areas illustrate areas where neighboring atoms are too far apart to interact with one another. Fig. 5a illustrates the two-dimensional fingerprint of all the contacts contributing to the Hirshfeld surface. The two-dimensional finger- Symmetry codes: (i) x; y þ 1; z; (ii) x; y À 1; z; (iii) Àx þ 2; Ày þ 1; Àz þ 1.

Figure 2
A view along the b axis of the crystal packing of the title compound.

Figure 1
The molecular structure of the title compound, with atom labelling and displacement ellipsoids drawn at the 50% probability level.  (Fig. 5b) associated with hydrogen atoms is characterized by an extremity pointed to the origin along the a diagonal, which corresponds to d i + d e = 2.2 Å and represents 59.7% of all the intermolecular contacts. Fig. 5c illustrates CÁ Á ÁH/HÁ Á ÁC contacts between carbon and hydrogen atoms from inside and outside the Hirshfeld surface and vice versa, resulting from HÁ Á ÁC short contacts. It accounts for 26.0% of the surface and is characterized by two symmetrical points with d i + d e = 2.6 Å . The plot of OÁ Á ÁH/HÁ Á ÁO contacts between hydrogen atoms located inside the Hirshfeld surface and oxygen from outside and vice versa is shown in Fig. 5d. These contacts account for 13.0% and are characterized by two symmetrical peaks with d i + d e = 1.8 Å ; this reveals the presence of strong OÁ Á ÁH contacts that are characteristic of C-HÁ Á ÁO and O-HÁ Á ÁO hydrogen bonds.

Synthesis and crystallization
A mixture of m-tolualdehyde (2.4 mmol), -naphthol (2 mmol), acetamide (2.4 mmol) in the presence of a catalytic amount of phenylboronic acid (1.5 mmol) was heated at 393 K without solvent for 7 h (the reaction was monitored by TLC). After completion of the reaction, the solid mixture was allowed to warm to room temperature, then 5 ml of 96% ethanol was added while maintaining stirring for 10 min. The Two views of the Hirshfeld surface mapped over d norm .

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.