2-[5-(2,3-Dimethoxynaphthalen-1-yl)-4,5-dihydro-1H-pyrazol-3-yl]-3-methoxyphenol

In the title compound, the central pyrazoline ring subtends dihedral angles of 4.61 (1) and 87.31 (1)° with the pendant benzene ring and naphthalene ring system, respectively. In the crystal, inversion dimers formed by pairwise weak N—H⋯N hydrogen bonds are linked by pairwise C—H⋯O hydrogen bonds into [100] chains.


Structure description
Pyrazolines have been reported to show a broad spectrum of biological activities including anticancer (Haider, et al., 2022), antimicrobial (Bano et al., 2015), antiinflammatory (Viveka et al., 2015), antimalarial (Kumar et al., 2018) and anti-Parkinsonian effects (Singh et al., 2018).Pyrazoline is generally synthesized from chalcone, and various synthetic methods have been reported in the literature (Praceka et al., 2021).Chalcones are key precursors for the synthesis of a various flavonoids when they have a hydroxyl group at the �-position of the ketone group.The single-crystal structures of various flavonoids synthesized from chalcones have previously been reported by our group (Sung, 2020).In a continuation of our research interest in broadening the application range of �-hydroxyl chalcone, the title pyrazoline compound was synthesized and its crystal structure was determined.
The title molecule, C 22 H 22 N 2 O 2 , crystallizes in space group P2 1 /n with one molecule in the asymmetric unit (Fig. 1).The central pyrazoline ring contains two sp 3 carbon atoms (C9 and C10), but it has a nearly planar structure (r.m.s.deviation = 0.025 A ˚).The benzene ring and naphthalene ring system are attached at positions C8 and C10 of the pyrazoline ring, and they are tilted by 4.61 (1) and 87.31 (1) � , respectively, with respect to the mean plane of the pyrazoline ring.The dihedral angle between the planes of the benzene ring and naphthalene ring system is 89.76 (2) � .The methoxy groups at the 3-position of naphthalene ring and the ortho position of the benzene ring are almost coplanar with the rings to which they are bound [C-O-C-C = À 7.9 (5) and À 0.4 (4) � , respectively], whereas the methoxy group at the 2-position of the naphthalene ring system is twisted from the ring [C-O-C-C = 112.5 (3) � ].The hydroxyl group at the ortho position of the benzene ring makes an intramolecular O1-H10� � �N1 hydrogen bond, forming an S(6) ring motif.In the crystal, inversion dimers linked by pairwise N2-H2A� � �N2 hydrogen bonds generate R 2 2 (4) loops and these dimers are linked by pairwise C6-H6� � �O1 hydrogen bonds [which generate R 2 2 (8) loops] into [100] chains (Table 1, Fig. 2).

Synthesis and crystallization
The starting chalcone, (E)-3-(2,3-dimethoxynaphthalen-1-yl)-1-(2-hydroxy-6-methoxyphenyl)prop-2-en-1-one, was prepared by the previously reported method (Sung, 2019).Pyrazoline was synthesized by a cyclization reaction of the chalcone with NH 2 NH 2 (Fig. 3).To a solution of 6-methoxy-2hydroxyacetophenone (10 mmol, 1.66 g) in 50 ml of ethanol was added 2,3-dimethoxy-1-naphthaldehyde (10 mmol, 1.56 g) and the temperature was adjusted to around 276-277 K in an ice bath.To the reaction mixture were added 8 ml of 40% (w/v) aqueous KOH solution and reaction mixture was stirred at room temperature for 20 h.At the end of the reaction, ice water was added to the mixture and acidified with 6 N HCl (pH = 3-4).The resulting precipitate was filtered and washed with water and ethanol.The crude solid was purified by recrystallization from ethanol solution to give the pure chal-  Table 1).

Figure 1
The molecular structure of the title compound with displacement ellipsoids drawn at the 30% probability level.
cone.Excess hydrazine monohydrate (1 ml of 64-65% solution, 13 mmol) was added to a solution of the chalcone compound (5 mmol, 1.52 g) in 30 ml of anhydrous ethanol and the solution was refluxed at 360 K for 5 h.The reaction mixture was cooled to room temperature to yield a solid that was then filtered.The crude solids were purified by recrystallization from ethanol solution to afford the title compound.

Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2.

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.

data reports data-2
IUCrData (2023).8, x230668 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.

Figure 2 A
Figure 2 A partial view of the crystal structure of the title compound showing dimer chains of molecules formed along [010].Intermolecular C-H� � �•O hydrogen bonds are shown as dashed lines (see Table1).

Table 2
Experimental details.