3,5-Bis(4-fluoro­phen­yl)isoxazole

Abstract

In the crystal structure of the title compound, C₁₅H₉F₂NO, the complete mol­ecule is generated by a crystallographic twofold rotation axis and the O and N atoms of the central isoxazole ring are statistically disordered with equal site occupancies. The terminal benzene rings form a dihedral angle of 24.23 (3)° with the isoxazole ring. The dihedral angle between the benzene rings is 47.39 (2)°. No significant inter­molecular inter­actions are observed.

Related literature  

For the pharmacological activity of isoxazole derivatives, see; Pradeepkumar et al. (2011 ▶). For our work on the synthesis of different derivatives of 4,4′-difluoro chalcone, see: Fun et al. (2010a ▶,b ▶). For stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986 ▶).

Experimental  

Crystal data  

• C₁₅H₉F₂NO

• M _r = 257.23

• Monoclinic,

• a = 27.9097 (4) Å

• b = 5.7319 (1) Å

• c = 7.1437 (1) Å

• β = 102.473 (1)°

• V = 1115.84 (3) ų

• Z = 4

• Mo Kα radiation

• μ = 0.12 mm⁻¹

• T = 100 K

• 0.30 × 0.24 × 0.12 mm

Data collection  

• Bruker SMART APEXII CCD area-detector diffractometer

• Absorption correction: multi-scan (SADABS; Bruker, 2009 ▶) T _min = 0.965, T _max = 0.986

• 17407 measured reflections

• 2483 independent reflections

• 2175 reflections with I > 2σ(I)

• R _int = 0.024

Refinement  

• R[F ² > 2σ(F ²)] = 0.045

• wR(F ²) = 0.131

• S = 1.09

• 2483 reflections

• 87 parameters

• H-atom parameters constrained

• Δρ_max = 0.62 e Å⁻³

• Δρ_min = −0.31 e Å⁻³

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

Supplementary Material

Supplementary material file. DOI: 10.1107/S160053681202171X/is5139Isup3.cml

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

supplementary crystallographic information

Comment

The various pharmacological activities of isoxazole derivatives are well documented (Pradeepkumar et al., 2011). Hence, in view of the importance of isoxazoles and in continuation of our work on synthesis of various derivatives of of 4,4'-difluoro chalcone (Fun et al., 2010a,b), the title compound was prepared and its crystal structure is reported.

The asymmetric unit of the title molecule (Figs. 1 and 2), C₁₅H₉F₂NO, contains one half-molecule with the other half of the molecule being generated by a twofold rotation axis (-x + 1, y, -z + 1/2). The crystal structure is disordered with the O1 and the N1 atoms attached at the same position with half occupancies each, forming the central isoxazole ring. The fluoro-substituted benzene rings (C1–C6 & C1A–C6A) make a dihedral angle of 24.23 (3)° with the isoxazole ring (N1/O1A/C7/C7A/C8 or O1/N1A/C7/C7A/C8). The dihedral angle between the fluoro-substituted benzene rings is 47.39 (2)°. The bond lengths and angles are within normal ranges. The crystal packing is shown in Fig. 3. No significant intermolecular interactions were observed.

Experimental

A solution of 4,4'-difluoro chalcone (2.44 g, 0.01 mol) and hydroxylamine hydrochloride (0.695 g, 0.01 mol) in 25 ml ethanol containing 3 ml of 10% sodium hydroxide solution was refluxed for 12 h. The reaction mixture was cooled and poured into 50 ml ice-cold water. The precipitate formed was collected by filtration and purified by recrystallization from ethanol. The single crystals were grown from a DMF solution by slow evaporation method and yield of the compound was 59%. (M. p. 463 K).

Refinement

The crystal structure is disordered at atom N1 and O1 with refined site of occupancies closed to 0.5. In the final refinement, the ratio was fixed at 0.5: 0.5. All the H atoms were positioned geometrically (C—H = 0.95 Å) and refined using a riding model with U_iso(H) = 1.2U_eq(C). The same atomic coordinates and displacement parameters were used for atom pair O1/N1. Three outliers (2 0 0), (5 1 3) and (9 1 1) were omitted.

Figures

Fig. 1.

The first disorder component of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Atoms with suffix A are generated by symmetry code -x + 1, y, -z + 1/2.

Fig. 2.

The second disorder component of the title compound, showing 50% probability displacement ellipsoids and the atom-numbering scheme. Atoms with suffix A are generated by symmetry code -x + 1, y, -z + 1/2.

Fig. 3.

A crystal packing diagram of the title compound, viewed along the b axis.

Crystal data

C15H9F2NO	F(000) = 528
Mr = 257.23	Dx = 1.531 Mg m−3
Monoclinic, C2/c	Mo Kα radiation, λ = 0.71073 Å
Hall symbol: -C 2yc	Cell parameters from 7031 reflections
a = 27.9097 (4) Å	θ = 3.0–35.2°
b = 5.7319 (1) Å	µ = 0.12 mm−1
c = 7.1437 (1) Å	T = 100 K
β = 102.473 (1)°	Block, colourless
V = 1115.84 (3) Å3	0.30 × 0.24 × 0.12 mm
Z = 4

Data collection

Bruker SMART APEXII CCD area-detector diffractometer	2483 independent reflections
Radiation source: fine-focus sealed tube	2175 reflections with I > 2σ(I)
Graphite monochromator	Rint = 0.024
φ and ω scans	θmax = 35.2°, θmin = 3.0°
Absorption correction: multi-scan (SADABS; Bruker, 2009)	h = −44→44
Tmin = 0.965, Tmax = 0.986	k = −9→9
17407 measured reflections	l = −11→11

Refinement

Refinement on F2	Primary atom site location: structure-invariant direct methods
Least-squares matrix: full	Secondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.045	Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.131	H-atom parameters constrained
S = 1.09	w = 1/[σ2(Fo2) + (0.0728P)2 + 0.6036P] where P = (Fo2 + 2Fc2)/3
2483 reflections	(Δ/σ)max < 0.001
87 parameters	Δρmax = 0.62 e Å−3
0 restraints	Δρmin = −0.31 e Å−3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.

Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq	Occ. (<1)
F1	0.26779 (2)	0.15964 (11)	−0.19266 (9)	0.02342 (15)
O1	0.47501 (2)	0.57010 (12)	0.20224 (10)	0.01759 (15)	0.50
N1	0.47501 (2)	0.57010 (12)	0.20224 (10)	0.01759 (15)	0.50
C1	0.39839 (3)	0.08546 (14)	−0.01408 (11)	0.01434 (15)
H1A	0.4233	−0.0272	−0.0145	0.017*
C2	0.35018 (3)	0.03736 (14)	−0.10665 (11)	0.01517 (15)
H2A	0.3419	−0.1066	−0.1714	0.018*
C3	0.31471 (3)	0.20453 (15)	−0.10192 (11)	0.01495 (15)
C4	0.32494 (3)	0.41685 (14)	−0.00912 (12)	0.01460 (15)
H4A	0.2997	0.5274	−0.0076	0.018*
C5	0.37327 (3)	0.46326 (13)	0.08167 (11)	0.01285 (14)
H5A	0.3813	0.6079	0.1457	0.015*
C6	0.41029 (3)	0.29891 (13)	0.07965 (11)	0.01230 (14)
C7	0.46118 (3)	0.34794 (14)	0.17574 (12)	0.01458 (15)
C8	0.5000	0.1978 (2)	0.2500	0.01459 (19)
H8A	0.5000	0.0321	0.2500	0.018*

Atomic displacement parameters (Ų)

	U11	U22	U33	U12	U13	U23
F1	0.0136 (2)	0.0260 (3)	0.0270 (3)	−0.00518 (19)	−0.0038 (2)	−0.0017 (2)
O1	0.0133 (3)	0.0143 (3)	0.0232 (3)	0.0005 (2)	−0.0006 (2)	−0.0005 (2)
N1	0.0133 (3)	0.0143 (3)	0.0232 (3)	0.0005 (2)	−0.0006 (2)	−0.0005 (2)
C1	0.0150 (3)	0.0134 (3)	0.0145 (3)	0.0011 (2)	0.0030 (2)	−0.0003 (2)
C2	0.0175 (3)	0.0129 (3)	0.0144 (3)	−0.0023 (2)	0.0019 (2)	−0.0012 (2)
C3	0.0123 (3)	0.0169 (3)	0.0144 (3)	−0.0033 (2)	0.0001 (2)	0.0006 (2)
C4	0.0121 (3)	0.0146 (3)	0.0163 (3)	0.0012 (2)	0.0014 (2)	0.0008 (2)
C5	0.0126 (3)	0.0119 (3)	0.0136 (3)	0.0002 (2)	0.0018 (2)	−0.0004 (2)
C6	0.0115 (3)	0.0129 (3)	0.0121 (3)	0.0002 (2)	0.0016 (2)	0.0005 (2)
C7	0.0121 (3)	0.0170 (3)	0.0141 (3)	−0.0007 (2)	0.0020 (2)	0.0000 (2)
C8	0.0128 (4)	0.0139 (4)	0.0164 (4)	0.000	0.0016 (3)	0.000

Geometric parameters (Å, º)

F1—C3	1.3546 (9)	C4—C5	1.3903 (10)
O1—C7	1.3322 (10)	C4—H4A	0.9500
O1—N1i	1.4145 (13)	C5—C6	1.4006 (11)
C1—C2	1.3926 (11)	C5—H5A	0.9500
C1—C6	1.3998 (11)	C6—C7	1.4650 (11)
C1—H1A	0.9500	C7—C8	1.3955 (10)
C2—C3	1.3833 (12)	C8—C7i	1.3955 (10)
C2—H2A	0.9500	C8—H8A	0.9500
C3—C4	1.3858 (12)
C7—O1—N1i	107.08 (4)	C5—C4—H4A	121.0
C7—O1—O1i	107.08 (4)	C4—C5—C6	120.66 (7)
C2—C1—C6	120.36 (7)	C4—C5—H5A	119.7
C2—C1—H1A	119.8	C6—C5—H5A	119.7
C6—C1—H1A	119.8	C1—C6—C5	119.56 (7)
C3—C2—C1	118.31 (7)	C1—C6—C7	119.85 (7)
C3—C2—H2A	120.8	C5—C6—C7	120.58 (7)
C1—C2—H2A	120.8	O1—C7—C8	110.98 (7)
F1—C3—C2	118.66 (7)	O1—C7—C6	118.14 (7)
F1—C3—C4	118.28 (7)	C8—C7—C6	130.87 (8)
C2—C3—C4	123.06 (7)	C7—C8—C7i	103.86 (10)
C3—C4—C5	118.04 (7)	C7—C8—H8A	128.1
C3—C4—H4A	121.0	C7i—C8—H8A	128.1
C6—C1—C2—C3	−0.49 (12)	N1i—O1—C7—C8	0.05 (10)
C1—C2—C3—F1	179.59 (7)	O1i—O1—C7—C8	0.05 (10)
C1—C2—C3—C4	−0.16 (12)	N1i—O1—C7—C6	179.64 (8)
F1—C3—C4—C5	−179.18 (7)	O1i—O1—C7—C6	179.64 (8)
C2—C3—C4—C5	0.57 (12)	C1—C6—C7—O1	156.29 (8)
C3—C4—C5—C6	−0.34 (12)	C5—C6—C7—O1	−24.13 (11)
C2—C1—C6—C5	0.71 (12)	C1—C6—C7—C8	−24.21 (12)
C2—C1—C6—C7	−179.70 (7)	C5—C6—C7—C8	155.37 (7)
C4—C5—C6—C1	−0.29 (12)	O1—C7—C8—C7i	−0.02 (4)
C4—C5—C6—C7	−179.87 (7)	C6—C7—C8—C7i	−179.55 (10)

Symmetry code: (i) −x+1, y, −z+1/2.