Crystal structure of (3,5-dichloro-2-hydroxyphenyl){1-[(naphthalen-1-yl)carbonyl]-1H-pyrazol-4-yl}methanone

The title compound is a 1,4-diaroyl pyrazole derivative and has three aromatic rings. In the crystal, molecules are linked through stacking interactions between the pyrazole rings and between the naphthalene and phenyl rings, and through intermolecular C—H⋯O hydrogen bonds to form inversion dimers.

The title compound, C 21 H 12 Cl 2 N 2 O 3 , is a 1,4-diaroyl pyrazole derivative and has three aromatic rings. The dihedral angles between the naphthalene ring system and the pyrazole ring, the pyrazole and phenyl rings and the naphthalene ring system and the phenyl ring are 49.44 (13), 49.87 (16) and 0.58 (11) , respectively. The phenolic proton forms an intramolecular O-HÁ Á ÁO hydrogen bond with an adjacent carbonyl O atom. In the crystal, the molecules are linked through stacking interactions between the pyrazole rings [centroid-centroid distances = 3.546 (3)] and between the naphthalene ring system and the phenyl ring [centroid-centroid distances = 3.609 (4) Å ] along the a-axis direction. The molecules are further connected through C-HÁ Á ÁO hydrogen bonds, forming inversion dimers.

Structural commentary
The reaction of 6,8-dichloro-3-formylchromone (Ishikawa & Motohashi, 2013) with 1-naphthoylhydrazide in benzene gave yellow solids, and orange crystals were obtained from an ethyl acetate/acetone solution of the yellow solids (Fig. 1). The ISSN 1600-5368 crystallographic analysis revealed that the structure of the orange crystals is a 1,4-diaroyl pyrazole, as shown in Fig. 2, which should be thermodynamically more stable than that of the yellow solids. The dihedral angles between the naphthalene ring system and the pyrazole ring, the pyrazole and phenyl rings and the naphthalene ring system and the phenyl ring are 49.44 (13), 49.87 (16) and 0.58 (11) , respectively. The phenolic proton forms an intramolecular O-HÁ Á ÁO hydrogen bond with the adjacent carbonyl O2 atom. The conformation of the title compound is almost identical to that of our previously reported 1,4-diaroyl pyrazole derivative (Ishikawa & Motohashi, 2014).
The driving force of the intramolecular cyclization ( Fig. 1) should be a resonance energy gain, resulting from the extension of the conjugated system across the entire molecule. The intramolecular cyclization is not observed for the chromone derivatives without electron-withdrawing substituents (Ishikawa & Watanabe, 2014a,b,c,d), and thus the activation energy for the chromone derivative with the electron-withdrawing substituents should be lower than that for ones without electron-withdrawing substituents.

Supramolecular features
The molecules are linked along the a-axis through stacking interactions between inversion-related pyrazole rings, and between the naphthalene ring system and the phenyl ring of an inversion-related molecule [centroid-centroid distances = 3.546 (3) and 3.609 (4) Å , respectively; symmetry code: -x + 1, -y + 1, -z]. The molecules are further connected through intermolecular C-HÁ Á ÁO hydrogen bonds (Table 1), forming inversion dimers, as shown in Fig. 3. Type I halogenÁ Á Áhalogen contacts between the chlorine atoms, which is seen in the crystal structure of the starting material, 6,8-dichloro-3formylchromone (Ishikawa & Motohashi, 2013), are not observed.

Figure 2
The molecular structure of the title compound, with displacement ellipsoids drawn at the 50% probability level. Hydrogen atoms are shown as small spheres of arbitrary radius.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq Cl1  (6)