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Acta Crystallogr Sect E Struct Rep Online. 2010 May 1; 66(Pt 5): o1009.
Published online 2010 April 2. doi:  10.1107/S1600536810011499
PMCID: PMC2979293

(2E,6E)-2,6-Bis(2,5-difluoro­benzyl­idene)cyclo­hexa­none

Abstract

In the title compound, C20H14F4O, a derivative of curcumin, the dihedral angle between the two aromatic rings is 27.19 (13)°. The C=C double bonds have an E configuration.

Related literature

For background and related structures, see: Liang et al. (2007a [triangle],b [triangle], 2009 [triangle]); Zhao et al. (2009 [triangle], 2010a [triangle],b [triangle]).

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Object name is e-66-o1009-scheme1.jpg

Experimental

Crystal data

  • C20H14F4O
  • M r = 346.31
  • Monoclinic, An external file that holds a picture, illustration, etc.
Object name is e-66-o1009-efi1.jpg
  • a = 15.824 (2) Å
  • b = 6.3128 (8) Å
  • c = 17.097 (2) Å
  • β = 111.756 (3)°
  • V = 1586.2 (3) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.12 mm−1
  • T = 293 K
  • 0.43 × 0.35 × 0.27 mm

Data collection

  • Bruker SMART CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2002 [triangle]) T min = 0.490, T max = 1.000
  • 8935 measured reflections
  • 3425 independent reflections
  • 2018 reflections with I > 2σ(I)
  • R int = 0.049

Refinement

  • R[F 2 > 2σ(F 2)] = 0.056
  • wR(F 2) = 0.156
  • S = 0.93
  • 3425 reflections
  • 227 parameters
  • H-atom parameters constrained
  • Δρmax = 0.23 e Å−3
  • Δρmin = −0.24 e Å−3

Data collection: SMART (Bruker, 2002 [triangle]); cell refinement: SAINT (Bruker, 2002 [triangle]); data reduction: SAINT; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 [triangle]); molecular graphics: SHELXTL (Sheldrick, 2008 [triangle]); software used to prepare material for publication: SHELXTL.

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810011499/ng2751sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810011499/ng2751Isup2.hkl

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

Acknowledgments

We acknowledge the X-ray crystallographic service at the Shanghai Institute of Organic Chemistry, Chinese Academy of Sciences for the data collection.

supplementary crystallographic information

Comment

The title compound, (2E,6E)-2,6-bis(2,5-difluorobenzylidene)cyclohexanone (I), is one of mono-carbonyl analogues of curcumin designed and synthesized by our group. The need for curcumin-like compounds with improved bioavailability characteristics has led to the chemical synthesis of a series of analogues, using curcumin as the primary structure. In our previous study, a series of fluorine-containing, mono-carbonyl analogues of curcumin were designed and synthesized by the deletion of β-diketone moiety, and their bioactivities were evaluated (Liang et al., 2009; Zhao et al., 2010a,b). Among those compounds, the cyclohexanone-containing analogues exhibited better anti-tumor properties and a wider anti-tumor spectrum than acetone- and cyclopentanone-containing analogues. Therefore, the structure of one of cyclohexanone-containing compounds (I), was further determined and analyzed using single-crystal X-ray diffraction. Accumulation of detailed structural and pharmacological data facilitated the explanation of the observed structure–activity relationships and modeling of new compounds with potential biological activity.

In this paper, we report the molecular and crystal structures of fluorine-containing, mono-carbonyl analogues of curcumin, (I). The molecule (I), consists of three ring systems, i.e., one cyclohexanone ring and two aryl rings. The central cyclohexanone ring has a distorted chair conformation, and molecular structures have an E-configuration towards the central olefinic bonds, exhibiting a butterfly-shaped geometry. The dihedral angle between the two terminal phenyl rings is 27.19 (13)°, and the two phenyl rings are twisted out of the plane of the central cyclohexanone on the two sides, respectively. Among these derivatives, some of them were reported of their crystal structures (Liang et al., 2007a,b; Zhao et al., 2009; Zhao et al., 2010a,b).

Experimental

Cyclohexanone (7.5 mmol) was dissolved in ethanol (5 ml) and crushed KOH (15 mmol) was added. The flask was immersed in a bath of crushed ice and a solution of 2,5-difluorobenzaldehyde (15 mmol) in ethanol (5 mmol) was added. The reaction mixture was stirred at 300 K and completion of the reaction was monitored by thin-layer chromatography. Ice-cold water was added to the reaction mixture after 48 h and the yellow solid that separated was filtered off, washed with water and cold ethanol, dried and purified by column chromatography on silica gel (yield: 45.3%). Single crystals of the title compound were grown in a CH2Cl2/CH3OH mixture (5:2 v/v) by slow evaporation (mp 132-135.4 K).

Refinement

The H atoms were positioned geometrically (C—H = 0.93 and 0.96 Å) and refined as riding with Uiso(H) = 1.2Ueq(C) or 1.5Ueq(methyl C).

Figures

Fig. 1.
The molecular structure of the title compound, showing 30% displacement ellipsoids for the non-hydrogen atoms. Hydrogen atoms are drawn as spheres of arbitrary radius.

Crystal data

C20H14F4OF(000) = 712
Mr = 346.31Dx = 1.450 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71073 Å
a = 15.824 (2) ÅCell parameters from 1858 reflections
b = 6.3128 (8) Åθ = 2.4–22.3°
c = 17.097 (2) ŵ = 0.12 mm1
β = 111.756 (3)°T = 293 K
V = 1586.2 (3) Å3Prismatic, colorless
Z = 40.43 × 0.35 × 0.27 mm

Data collection

Bruker SMART CCD area-detector diffractometer3425 independent reflections
Radiation source: fine-focus sealed tube2018 reflections with I > 2σ(I)
graphiteRint = 0.049
phi and ω scansθmax = 27.0°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Bruker, 2002)h = −15→20
Tmin = 0.490, Tmax = 1.000k = −7→8
8935 measured reflectionsl = −21→18

Refinement

Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.056H-atom parameters constrained
wR(F2) = 0.156w = 1/[σ2(Fo2) + (0.082P)2] where P = (Fo2 + 2Fc2)/3
S = 0.93(Δ/σ)max < 0.001
3425 reflectionsΔρmax = 0.23 e Å3
227 parametersΔρmin = −0.24 e Å3
0 restraintsExtinction correction: SHELXL97 (Sheldrick, 2008), Fc*=kFc[1+0.001xFc2λ3/sin(2θ)]-1/4
Primary atom site location: structure-invariant direct methodsExtinction coefficient: 0.015 (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.
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 > 2sigma(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 (Å2)

xyzUiso*/Ueq
F10.40753 (15)0.4774 (3)1.14644 (10)0.1192 (7)
F20.42662 (12)1.2350 (2)1.00801 (10)0.0934 (5)
F30.00929 (10)0.5237 (2)0.36811 (8)0.0809 (5)
F40.16575 (11)1.2677 (2)0.49902 (9)0.0839 (5)
O10.17234 (12)1.1232 (3)0.76698 (9)0.0796 (6)
C10.20606 (14)0.9520 (4)0.76181 (12)0.0520 (6)
C20.26784 (13)0.8418 (3)0.83949 (12)0.0466 (5)
C30.29758 (14)0.9609 (4)0.90938 (13)0.0556 (6)
H30.27661.09990.90330.067*
C40.35876 (14)0.9001 (4)0.99398 (12)0.0528 (6)
C50.35519 (16)0.7068 (4)1.03101 (14)0.0633 (6)
H50.31250.60531.00190.076*
C60.4149 (2)0.6673 (5)1.11059 (15)0.0760 (8)
C70.47922 (18)0.8090 (6)1.15698 (15)0.0836 (9)
H70.51960.77551.21080.100*
C80.48225 (18)1.0026 (5)1.12152 (16)0.0794 (8)
H80.52471.10391.15120.095*
C90.42230 (17)1.0439 (4)1.04241 (14)0.0654 (7)
C100.18662 (13)0.8503 (3)0.67808 (12)0.0466 (5)
C110.14905 (14)0.9764 (3)0.61179 (13)0.0517 (6)
H110.14031.11600.62440.062*
C120.11951 (13)0.9273 (3)0.52187 (12)0.0470 (5)
C130.07950 (14)0.7364 (3)0.48623 (12)0.0503 (5)
H130.07310.62750.52020.060*
C140.04988 (14)0.7102 (4)0.40128 (13)0.0556 (6)
C150.05733 (15)0.8634 (4)0.34722 (14)0.0614 (7)
H150.03670.83960.28950.074*
C160.09649 (17)1.0538 (4)0.38151 (14)0.0629 (7)
H160.10251.16240.34720.076*
C170.12608 (15)1.0796 (3)0.46646 (14)0.0562 (6)
C180.29633 (15)0.6182 (3)0.83255 (12)0.0528 (6)
H18A0.25250.52150.84050.063*
H18B0.35490.59160.87690.063*
C190.30317 (15)0.5754 (4)0.74764 (12)0.0541 (6)
H19A0.35140.66160.74210.065*
H19B0.31880.42790.74460.065*
C200.21500 (14)0.6242 (3)0.67610 (12)0.0523 (6)
H20A0.22200.59680.62300.063*
H20B0.16770.53130.67960.063*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
F10.193 (2)0.0997 (14)0.0587 (9)0.0260 (13)0.0392 (11)0.0185 (9)
F20.1281 (14)0.0767 (12)0.0776 (10)−0.0307 (10)0.0406 (10)−0.0231 (8)
F30.0950 (11)0.0712 (10)0.0577 (8)−0.0144 (8)0.0066 (7)−0.0117 (7)
F40.1145 (12)0.0498 (9)0.0738 (9)−0.0116 (8)0.0189 (9)0.0087 (7)
O10.1081 (14)0.0625 (12)0.0539 (10)0.0340 (10)0.0133 (9)−0.0087 (8)
C10.0591 (13)0.0470 (14)0.0464 (12)0.0073 (11)0.0155 (10)−0.0066 (10)
C20.0484 (12)0.0478 (13)0.0427 (11)−0.0004 (9)0.0159 (9)−0.0013 (9)
C30.0606 (14)0.0549 (14)0.0478 (12)0.0038 (11)0.0159 (11)−0.0042 (10)
C40.0539 (12)0.0624 (15)0.0421 (11)0.0039 (11)0.0179 (10)−0.0090 (10)
C50.0741 (16)0.0689 (17)0.0456 (12)−0.0015 (13)0.0206 (12)−0.0073 (11)
C60.104 (2)0.082 (2)0.0416 (13)0.0253 (16)0.0262 (14)0.0058 (13)
C70.0701 (17)0.126 (3)0.0422 (14)0.0292 (18)0.0062 (13)−0.0182 (16)
C80.0680 (17)0.109 (2)0.0561 (16)−0.0100 (16)0.0176 (14)−0.0303 (16)
C90.0707 (16)0.0769 (19)0.0497 (14)−0.0028 (14)0.0235 (13)−0.0184 (13)
C100.0472 (11)0.0444 (13)0.0433 (11)0.0023 (9)0.0113 (9)−0.0041 (9)
C110.0588 (13)0.0431 (13)0.0483 (12)0.0081 (10)0.0143 (10)−0.0010 (9)
C120.0463 (11)0.0458 (13)0.0454 (11)0.0090 (9)0.0128 (9)0.0046 (9)
C130.0536 (12)0.0474 (13)0.0445 (12)0.0013 (10)0.0118 (10)0.0054 (9)
C140.0550 (13)0.0537 (15)0.0494 (13)0.0027 (11)0.0092 (10)−0.0019 (11)
C150.0648 (15)0.0728 (18)0.0429 (12)0.0142 (13)0.0157 (11)0.0048 (12)
C160.0729 (15)0.0599 (16)0.0547 (14)0.0092 (13)0.0221 (12)0.0188 (12)
C170.0619 (14)0.0417 (14)0.0577 (14)0.0045 (11)0.0137 (11)0.0063 (11)
C180.0606 (13)0.0513 (14)0.0437 (11)0.0047 (11)0.0161 (10)0.0013 (10)
C190.0617 (13)0.0494 (14)0.0476 (12)0.0110 (11)0.0159 (10)−0.0016 (10)
C200.0626 (13)0.0462 (14)0.0432 (11)0.0059 (10)0.0140 (10)−0.0039 (9)

Geometric parameters (Å, °)

F1—C61.371 (3)C10—C201.500 (3)
F2—C91.355 (3)C11—C121.465 (3)
F3—C141.360 (2)C11—H110.9300
F4—C171.362 (2)C12—C171.381 (3)
O1—C11.223 (2)C12—C131.392 (3)
C1—C101.493 (3)C13—C141.361 (3)
C1—C21.497 (3)C13—H130.9300
C2—C31.341 (3)C14—C151.372 (3)
C2—C181.500 (3)C15—C161.380 (3)
C3—C41.462 (3)C15—H150.9300
C3—H30.9300C16—C171.361 (3)
C4—C91.380 (3)C16—H160.9300
C4—C51.386 (3)C18—C191.519 (3)
C5—C61.361 (3)C18—H18A0.9700
C5—H50.9300C18—H18B0.9700
C6—C71.366 (4)C19—C201.508 (3)
C7—C81.373 (4)C19—H19A0.9700
C7—H70.9300C19—H19B0.9700
C8—C91.359 (3)C20—H20A0.9700
C8—H80.9300C20—H20B0.9700
C10—C111.331 (3)
O1—C1—C10120.60 (18)C13—C12—C11124.00 (19)
O1—C1—C2120.36 (18)C14—C13—C12119.5 (2)
C10—C1—C2119.03 (19)C14—C13—H13120.2
C3—C2—C1115.35 (19)C12—C13—H13120.2
C3—C2—C18125.57 (18)F3—C14—C13118.2 (2)
C1—C2—C18118.93 (17)F3—C14—C15118.3 (2)
C2—C3—C4128.3 (2)C13—C14—C15123.5 (2)
C2—C3—H3115.9C14—C15—C16117.7 (2)
C4—C3—H3115.9C14—C15—H15121.2
C9—C4—C5116.7 (2)C16—C15—H15121.2
C9—C4—C3119.3 (2)C17—C16—C15118.7 (2)
C5—C4—C3124.0 (2)C17—C16—H16120.6
C6—C5—C4119.1 (2)C15—C16—H16120.6
C6—C5—H5120.4C16—C17—F4117.7 (2)
C4—C5—H5120.4C16—C17—C12124.4 (2)
C5—C6—C7123.5 (3)F4—C17—C12117.9 (2)
C5—C6—F1117.7 (3)C2—C18—C19111.88 (17)
C7—C6—F1118.8 (2)C2—C18—H18A109.2
C6—C7—C8117.8 (2)C19—C18—H18A109.2
C6—C7—H7121.1C2—C18—H18B109.2
C8—C7—H7121.1C19—C18—H18B109.2
C9—C8—C7119.0 (3)H18A—C18—H18B107.9
C9—C8—H8120.5C20—C19—C18111.50 (18)
C7—C8—H8120.5C20—C19—H19A109.3
F2—C9—C8118.3 (2)C18—C19—H19A109.3
F2—C9—C4117.9 (2)C20—C19—H19B109.3
C8—C9—C4123.8 (3)C18—C19—H19B109.3
C11—C10—C1115.29 (19)H19A—C19—H19B108.0
C11—C10—C20126.35 (18)C10—C20—C19111.77 (17)
C1—C10—C20118.28 (17)C10—C20—H20A109.3
C10—C11—C12129.4 (2)C19—C20—H20A109.3
C10—C11—H11115.3C10—C20—H20B109.3
C12—C11—H11115.3C19—C20—H20B109.3
C17—C12—C13116.12 (19)H20A—C20—H20B107.9
C17—C12—C11119.8 (2)
O1—C1—C2—C3−13.6 (3)C2—C1—C10—C2011.5 (3)
C10—C1—C2—C3166.2 (2)C1—C10—C11—C12−178.3 (2)
O1—C1—C2—C18170.6 (2)C20—C10—C11—C125.2 (4)
C10—C1—C2—C18−9.7 (3)C10—C11—C12—C17−146.9 (2)
C1—C2—C3—C4−179.3 (2)C10—C11—C12—C1336.8 (4)
C18—C2—C3—C4−3.8 (4)C17—C12—C13—C140.1 (3)
C2—C3—C4—C9141.8 (2)C11—C12—C13—C14176.5 (2)
C2—C3—C4—C5−40.8 (4)C12—C13—C14—F3−178.60 (18)
C9—C4—C5—C6−1.8 (3)C12—C13—C14—C150.2 (3)
C3—C4—C5—C6−179.3 (2)F3—C14—C15—C16178.34 (19)
C4—C5—C6—C70.1 (4)C13—C14—C15—C16−0.5 (4)
C4—C5—C6—F1177.8 (2)C14—C15—C16—C170.5 (4)
C5—C6—C7—C81.1 (4)C15—C16—C17—F4179.0 (2)
F1—C6—C7—C8−176.6 (2)C15—C16—C17—C12−0.2 (4)
C6—C7—C8—C9−0.5 (4)C13—C12—C17—C160.0 (3)
C7—C8—C9—F2−179.5 (2)C11—C12—C17—C16−176.6 (2)
C7—C8—C9—C4−1.4 (4)C13—C12—C17—F4−179.30 (18)
C5—C4—C9—F2−179.4 (2)C11—C12—C17—F44.1 (3)
C3—C4—C9—F2−1.7 (3)C3—C2—C18—C19−143.7 (2)
C5—C4—C9—C82.5 (4)C1—C2—C18—C1931.7 (3)
C3—C4—C9—C8−179.8 (2)C2—C18—C19—C20−56.2 (3)
O1—C1—C10—C1114.5 (3)C11—C10—C20—C19140.9 (2)
C2—C1—C10—C11−165.28 (19)C1—C10—C20—C19−35.6 (3)
O1—C1—C10—C20−168.7 (2)C18—C19—C20—C1058.3 (3)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
C16—H16···O1i0.932.463.343 (3)158

Symmetry codes: (i) x, −y+5/2, z−1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NG2751).

References

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  • Liang, G., Yang, S.-L., Wang, X.-H., Li, Y.-R. & Li, X.-K. (2007b). Acta Cryst. E63, o4118.
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  • Zhao, C. G., Yang, J., Wang, Y., Liang, D. L., Yang, X. Y., Wu, J. Z., Wu, X. P., Yang, S. L., Li, X. K. & Liang, G. (2010b). Bioorg. Med. Chem doi: 10.1016/j.bmc.2010.03.001.

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