Crystal structure of 3-meth­oxy-2-[5-(naphthalen-1-yl)-4,5-di­hydro-1H-pyrazol-3-yl]phenol

Dongsoo Koh

doi:10.1107/S2056989015018472

. 2015 Oct 7;71(Pt 11):o828–o829. doi: 10.1107/S2056989015018472

Crystal structure of 3-methoxy-2-[5-(naphthalen-1-yl)-4,5-dihydro-1H-pyrazol-3-yl]phenol

Dongsoo Koh ^a,^*

PMCID: PMC4645021 PMID: 26594549

Abstract

In the title compound, C₂₀H₁₈N₂O₂, the central pyrazoline ring has an envelope conformation with the atom substituted by the naphthalene ring as the flap. It bridges a benzene ring and a naphthalene ring system which are almost normal to one another, making a dihedral angle of 82.03 (6) °. There is an intramolecular O—H⋯N hydrogen bond forming an S(6) ring motif. In the crystal, molecules are linked by pairs of N—H⋯π interactions, forming inversion dimers. There are also C—H⋯π interactions present and the dimers are linked via C—H⋯O hydrogen bonds, forming ribbons propagating along the a-axis direction.

Keywords: crystal structure, pyrazoline, hydrogen bonds, N—H⋯π interaction, C—H⋯π interaction

Related literature

For the biological properties and synthesis of pyrazoline derivatives, see: Viveka et al. (2015 ▸); Neudorfer et al. (2014 ▸); Hwang et al. (2013 ▸); Congiu et al. (2010 ▸). For the N—H⋯π interaction, see: Naveen et al. (2015 ▸). For related structures, see: Zhu et al. (2013 ▸); Patel et al. (2013 ▸). graphic file with name e-71-0o828-scheme1.jpg

Experimental

Crystal data

C₂₀H₁₈N₂O₂
M _r = 318.36
Triclinic,
a = 7.7280 (12) Å
b = 8.6933 (14) Å
c = 12.721 (2) Å
α = 78.507 (4)°
β = 73.781 (4)°
γ = 76.148 (4)°
V = 788.7 (2) Å³
Z = 2
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 147 K
0.23 × 0.14 × 0.10 mm

Data collection

Bruker Kappa APEX-DUO CCD diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2012 ▸) T _min = 0.980, T _max = 0.991
6731 measured reflections
3605 independent reflections
2963 reflections with I > 2σ(I)
R _int = 0.027

Refinement

R[F ² > 2σ(F ²)] = 0.042
wR(F ²) = 0.119
S = 1.06
3605 reflections
226 parameters
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.28 e Å⁻³
Δρ_min = −0.26 e Å⁻³

Data collection: APEX2 (Bruker, 2012 ▸); cell refinement: SAINT (Bruker, 2012 ▸); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▸); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▸); molecular graphics: PLATON (Spek, 2009 ▸); software used to prepare material for publication: SHELXTL (Sheldrick, 2008 ▸) and PLATON.

Supplementary Material

Crystal structure: contains datablock(s) I, New_Global_Publ_Block. DOI: 10.1107/S2056989015018472/su5207sup1.cif

e-71-0o828-sup1.cif^{(25.9KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S2056989015018472/su5207Isup2.hkl

e-71-0o828-Isup2.hkl^{(176.7KB, hkl)}

Click here for additional data file.^{(6.5KB, cml)}

Supporting information file. DOI: 10.1107/S2056989015018472/su5207Isup3.cml

Click here for additional data file.^{(1.4MB, tif)}

. DOI: 10.1107/S2056989015018472/su5207fig1.tif

The molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 30% probability level. The intramolecular O-H⋯N hydrogen bond is shown as a dashed line (see Table 1).

Click here for additional data file.^{(966.8KB, tif)}

. DOI: 10.1107/S2056989015018472/su5207fig2.tif

Part of the crystal structure of the title compound, showing the intramolecular O—H⋯N hydrogen bond and the intermolecular N—H⋯π interactions, as dashed lines (see Table 1). H atoms not involved in these interactions have been omitted for clarity.

CCDC reference: 1429221

Additional supporting information: crystallographic information; 3D view; checkCIF report

Table 1. Hydrogen-bond geometry (, ).

Cg2 and Cg3 are the centroids of rings C4C8/C13 and C8C13, respectively.

DHA	DH	HA	D A	DHA
O2H2ON1	0.87(2)	1.79(2)	2.5681(14)	148.0(19)
N2H2N Cg3ⁱ	0.88(2)	2.56(2)	3.1811(13)	128.1(14)
C3H3A Cg2ⁱ	1.00	2.80	3.5306(15)	130
C12H12AO2ⁱⁱ	0.95	2.54	3.4488(17)	161

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Symmetry codes: (i) Inline graphic ; (ii) .

supplementary crystallographic information

S1. Introduction

Pyrazolines have been reported to show a wide range of biological activities: They have been reported to be effective as Alzheimer drugs (Neudorfer et al., 2014), and as having anti-inflammatory (Viveka et al., 2015) and antitumor properties (Congiu et al., 2010). The title pyrazoline derivative was synthesized in continuation of our research program (Hwang et al. 2013), and we report herein on its crystal structure.

The molecular structure of the title compound is shown in Fig. 1. The central pyrazoline ring (N1/N2/C1—C3) has an envelope conformation with the atom C3 as the flap. The benzene ring (C14—C19) and the naphthalene ring system (C4—C13) are attached to the central pyrazoline ring (N1/N2/C1—C3) at positions C1 and C3, respectively. The benzene and naphthalene ring are almost normal to one another with a dihedral angle of is 82.03 (6) °. The methoxy group at the ortho position of the benzene ring is almost coplanar with the ring [C16—C15—O1—C20 = 2.2 (2) °]. The hydroxyl group at the ortho position of the benzene ring makes an intramolecular O—H···N hydrogen bond to form an S(6) ring motif.

In the crystal, molecules are linked by pairs of N—H···π interactions forming inversion dimers (Fig. 2 and Table 1). There are also C—H···π interactions present and the dimers are linked via C—H···O hydrogen bonds forming ribbons propagating along the a axis direction. (Table 1).

An example of intermolecular N—H···π interaction in pyrazoline system was reported in a recent publication (Naveen et al., 2015). Examples of pyrazoline structures have been also published (Zhu et al., 2013; Patel et al., 2013).

S2. Experimental

To a solution of 6-methoxy-2-hydroxyacetophenone (10 mmol, 1.66 g) in 40 ml of ethanol was added 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 was added 10 ml of 50% (w/v) aqueous KOH solution and the reaction mixture was stirred at room temperature for 24 h. At the end of the reaction, ice water was added to the mixture and it was acidified with 6N HCl (pH = 3-4). The resulting precipitate was filtered and washed with water and ethanol. The crude solid was purified by recrystallization from ethanol to give pure chalcone. 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 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 to afford the title compound as yellow needles (m.p.: 429-430 K; yield: 56%).

S2.1. Refinement

Crystal data, data collection and structure refinement details are summarized in Table 2. The NH and OH H atoms were located in a difference Fourier map and freely refined. The C-bound H atoms were fixed geometrically and allowed to ride on their parent atoms: C—H = 0.95 - 1.00 Å with U_iso(H) = 1.5U_eq(C) for methyl H atoms and 1.2U_eq(C) for other H atoms.