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Acta Cryst. (2009). E65, o1294-o1295    [ doi:10.1107/S1600536809017334 ]

7,7',8,8'-Tetramethoxy-4,4'-dimethyl-3,3'-bicoumarin

H.-K. Fun, S. R. Jebas, M. Parveen, Z. Khanam and R. M. Ghalib

Abstract top

In the crystal structure, the title compound, C24H22O8, lies on a twofold rotation axis and the asymmetric unit comprises one half-molecule. The dihedral angle formed by the coumarin unit with the symmetry-related part is 74.78 (14)°. One of the methoxy groups attached to the coumarin unit is considerably twisted, making an angle of 87.17 (17)° with respect to the coumarin unit; the other is twisted by 0.66 (19)°. No classical hydrogen bonds are found in the sturcture; only a weak C-H...[pi] interaction and short intramolecular O...O contacts [2.683 (2)-2.701 (2) Å] are observed.

Comment top

Coumarins are a large group of naturally occurring oxygen heterocycles representing 2H-1-benzopyran-2-one derivative. Many natural coumarins are reputed for their wide range of biological activites such as antibacterial (El-Agrody et al., 2001; Pratibha & Shreeya, 1999), antifungal (Shaker, 1996; El-Farargy, 1991), antioxidant (Yang et al., 2005), analgesic (Ghate et al., 2005), anti-inflammatory (Emmanuel-Giota et al., 2001) and antitumor (Nofal et al., 2000) properties. Bi and tri-coumarins are comparatively new groups which are widely spread in nature and their biological properties are also well known (Laakso et al., 1994). One of the characteristic pharmacological properties of coumarin derivatives is the anticoagulant action (Kennedy & Thornes, 1997). A large number of natural and semisynthetic coumarin and bicoumarin derivatives have been reported to demonstrate chemopreventive (Carlton et al., 1996) and anti-HIV (Zhou et al., 2000) activities. Keeping in view of these biological importance of coumarins and their dimers, we have synthesized the title compound (I) and report here its structure.

The asymmetric unit of (I) (Fig. 1), contains half of the 7,7',8,8'-4,4'-dimethyl-3,3'-bicoumarin molecule. The other half is symmetry generated [symmetry code: -x, y, -z + 1/2]. The coumarin unit is planar with the maximum deviation from the mean plane of 0.0295 (15) Å for atom C2. One of the methyl group attached to the coumarin unit is twisted as evidenced by the torsion angle of C10—O3—C8—C9 = 87.17 (17)°. The dihedral angle formed by the coumarin unit (O1/C1—C9) with the symmetry related coumarin unit (O1A/C1A—C9A) is 74.78 (14)°, indicating that they are almost perpendicular to each other. The bond lengths (Allen et al., 1987) and bond angles are normal.

The crystal packing (Fig. 2) (Table 1) is stabilized by weak C—H···π interactions and intramolecular O···O = 2.683 (2) to 2.701 (2) Å short contacts.

Related literature top

For thebiological activity of coumarin, see: El-Agrody et al. (2001); El-Farargy (1991); Emmanuel-Giota et al. (2001); Ghate et al. (2005); Laakso et al. (1994); Nofal et al. (2000); Pratibha & Shreeya (1999); Shaker (1996); Yang et al. (2005). For the pharmaceutical properties of coumarin derivatives, see: Kennedy & Thornes (1997). For natural and synthetic coumarins, see: Carlton et al. (1996); Zhou et al. (2000). For related bond-length data, see: Allen et al. (1987). For stability of the temperature controller used in the data collection, see: Cosier & Glazer (1986). Cg1 is the centroid of the C4–C9 ring.

Experimental top

A mixture of 7,8-dimethoxy-4-methyl coumarin (2.20 g, 10 mmol) and manganese(III) acetate (0.774 g, 1 mmol) was stirred at room temperature, then 70% perchloric acid (0.8 g, 6 mmol) was added. The reaction mixture was heated under reflux at 114°C with stirring in the atmosphere of nitrogen for 3 h. The reaction mixture was cooled and diluted with 50 ml of benzene. The benzene solution was washed with water and aq. NaHCO3, dried over anhydrous Na2SO4 and left to evaporate. The residue showed two major compounds which were separated by column chromatography followed by preparative thin layer chromatography (Benzene: EtOAc, 9:1) into the title compound (I) (260 mg, 12%).

Refinement top

All the hydrogen atoms were located from the Fourier map and allowed to refine freely.

Computing details top

Data collection: APEX2 (Bruker, 2005); cell refinement: SAINT (Bruker, 2005); data reduction: SAINT (Bruker, 2005); program(s) used to solve structure: SHELXTL (Sheldrick, 2008); program(s) used to refine structure: SHELXTL (Sheldrick, 2008); molecular graphics: SHELXTL (Sheldrick, 2008); software used to prepare material for publication: SHELXTL (Sheldrick, 2008) and PLATON (Spek, 2009).

Figures top
[Figure 1] Fig. 1. The molecular structure of (I), showing 50% probability displacement ellipsoids and the atom numbering scheme. [Symmetry code: -x, y, -z + 1/2 to generate equivalent atoms].
[Figure 2] Fig. 2. The crystal packing of (I). Molecules are stacked along the b axis.
(I) top
Crystal data top
C24H22O8F000 = 920
Mr = 438.42Dx = 1.425 Mg m−3
Monoclinic, C2/cMo Kα radiation
λ = 0.71073 Å
Hall symbol: -C 2ycCell parameters from 6562 reflections
a = 21.715 (9) Åθ = 2.7–31.8º
b = 7.138 (3) ŵ = 0.11 mm−1
c = 15.511 (6) ÅT = 100 K
β = 121.801 (5)ºPlate, colourless
V = 2043.3 (14) Å30.28 × 0.19 × 0.06 mm
Z = 4
Data collection top
Bruker SMART APEXII CCD area-detector
diffractometer		3527 independent reflections
Radiation source: fine-focus sealed tube2710 reflections with I > 2σ(I)
Monochromator: graphiteRint = 0.065
T = 100 Kθmax = 32.0º
φ and ω scansθmin = 2.2º
Absorption correction: multi-scan
(SADABS; Bruker, 2005)		h = −32→32
Tmin = 0.971, Tmax = 0.994k = −10→10
27961 measured reflectionsl = −23→23
Refinement top
Refinement on F2Secondary atom site location: difference Fourier map
Least-squares matrix: fullHydrogen site location: inferred from neighbouring sites
R[F2 > 2σ(F2)] = 0.059All H-atom parameters refined
wR(F2) = 0.155  w = 1/[σ2(Fo2) + (0.0752P)2 + 1.2567P]
where P = (Fo2 + 2Fc2)/3
S = 1.08(Δ/σ)max < 0.001
3527 reflectionsΔρmax = 0.50 e Å−3
189 parametersΔρmin = −0.21 e Å−3
Primary atom site location: structure-invariant direct methodsExtinction correction: none
Crystal data top
C24H22O8V = 2043.3 (14) Å3
Mr = 438.42Z = 4
Monoclinic, C2/cMo Kα
a = 21.715 (9) ŵ = 0.11 mm−1
b = 7.138 (3) ÅT = 100 K
c = 15.511 (6) Å0.28 × 0.19 × 0.06 mm
β = 121.801 (5)º
Data collection top
Bruker SMART APEXII CCD area-detector
diffractometer		3527 independent reflections
Absorption correction: multi-scan
(SADABS; Bruker, 2005)		2710 reflections with I > 2σ(I)
Tmin = 0.971, Tmax = 0.994Rint = 0.065
27961 measured reflections
Refinement top
R[F2 > 2σ(F2)] = 0.059189 parameters
wR(F2) = 0.155All H-atom parameters refined
S = 1.08Δρmax = 0.50 e Å−3
3527 reflectionsΔρmin = −0.21 e Å−3
Special details top

Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems 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 (Å2) top
xyzUiso*/Ueq
O10.15443 (5)0.04445 (13)0.38705 (7)0.0178 (2)
O20.05473 (6)−0.06775 (15)0.37300 (8)0.0242 (2)
O30.30066 (5)0.03278 (14)0.48961 (7)0.0212 (2)
O40.37511 (5)0.26053 (15)0.43926 (8)0.0221 (2)
C10.08045 (7)0.05014 (19)0.34517 (10)0.0175 (3)
C20.03949 (7)0.19639 (19)0.27048 (10)0.0163 (3)
C30.07228 (7)0.32194 (19)0.24158 (10)0.0168 (3)
C40.15015 (7)0.31354 (18)0.28870 (10)0.0161 (3)
C50.19034 (8)0.44106 (19)0.26927 (10)0.0185 (3)
C60.26498 (8)0.42852 (19)0.31768 (11)0.0194 (3)
C70.30199 (7)0.28719 (19)0.38881 (10)0.0174 (3)
C80.26401 (7)0.15966 (18)0.41265 (9)0.0164 (3)
C90.18892 (7)0.17416 (18)0.36139 (10)0.0154 (2)
C100.30773 (13)−0.1493 (2)0.45770 (15)0.0362 (4)
C110.41539 (8)0.3869 (2)0.41549 (13)0.0267 (3)
C120.02974 (8)0.4697 (2)0.16315 (12)0.0247 (3)
H50.1654 (10)0.540 (3)0.2226 (15)0.024 (5)*
H60.2908 (11)0.516 (3)0.3016 (16)0.033 (5)*
H10A0.3396 (14)−0.139 (4)0.429 (2)0.063 (8)*
H10B0.3324 (13)−0.224 (3)0.514 (2)0.046 (6)*
H10C0.2573 (16)−0.202 (4)0.410 (2)0.067 (8)*
H11A0.3985 (12)0.382 (3)0.3405 (19)0.044 (6)*
H11B0.4125 (11)0.519 (3)0.4338 (15)0.028 (5)*
H11C0.4642 (10)0.340 (3)0.4535 (14)0.022 (4)*
H12A0.0472 (11)0.483 (3)0.1149 (17)0.035 (5)*
H12B0.0359 (12)0.591 (3)0.1955 (18)0.041 (6)*
H12C−0.0217 (12)0.440 (3)0.1264 (17)0.036 (5)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
O10.0162 (5)0.0193 (5)0.0163 (4)0.0013 (3)0.0074 (4)0.0050 (4)
O20.0213 (5)0.0253 (5)0.0244 (5)−0.0003 (4)0.0111 (4)0.0083 (4)
O30.0217 (5)0.0219 (5)0.0134 (4)0.0047 (4)0.0048 (4)0.0029 (4)
O40.0144 (5)0.0250 (5)0.0230 (5)−0.0015 (4)0.0071 (4)−0.0020 (4)
C10.0167 (6)0.0199 (6)0.0149 (6)0.0003 (5)0.0076 (5)0.0008 (5)
C20.0155 (6)0.0179 (6)0.0140 (6)0.0004 (4)0.0067 (5)−0.0003 (4)
C30.0166 (6)0.0176 (6)0.0145 (6)0.0013 (4)0.0071 (5)0.0018 (4)
C40.0166 (6)0.0174 (6)0.0133 (5)0.0013 (4)0.0072 (5)0.0009 (4)
C50.0199 (6)0.0185 (6)0.0165 (6)0.0007 (5)0.0091 (5)0.0027 (5)
C60.0202 (6)0.0200 (6)0.0186 (6)−0.0016 (5)0.0106 (5)−0.0002 (5)
C70.0142 (6)0.0211 (6)0.0143 (6)−0.0007 (4)0.0058 (5)−0.0037 (5)
C80.0168 (6)0.0176 (6)0.0108 (5)0.0018 (4)0.0045 (5)−0.0003 (4)
C90.0175 (6)0.0155 (6)0.0125 (5)−0.0012 (4)0.0075 (5)−0.0006 (4)
C100.0564 (12)0.0239 (8)0.0302 (9)0.0173 (8)0.0241 (9)0.0093 (7)
C110.0188 (7)0.0267 (8)0.0339 (8)−0.0059 (6)0.0134 (6)−0.0047 (6)
C120.0183 (7)0.0265 (7)0.0254 (7)0.0030 (5)0.0089 (6)0.0112 (6)
Geometric parameters (Å, °) top
O1—C91.3750 (16)C5—H50.952 (19)
O1—C11.3801 (17)C6—C71.395 (2)
O2—C11.2085 (17)C6—H60.96 (2)
O3—C81.3701 (16)C7—C81.4025 (19)
O3—C101.428 (2)C8—C91.3912 (19)
O4—C71.3640 (17)C10—H10A1.01 (3)
O4—C111.4334 (19)C10—H10B0.92 (3)
C1—C21.4618 (19)C10—H10C1.02 (3)
C2—C31.3592 (19)C11—H11A1.02 (2)
C2—C2i1.482 (3)C11—H11B1.00 (2)
C3—C41.4472 (19)C11—H11C0.963 (19)
C3—C121.5036 (19)C12—H12A1.01 (2)
C4—C51.3993 (19)C12—H12B0.97 (2)
C4—C91.4034 (18)C12—H12C0.97 (2)
C5—C61.384 (2)
C9—O1—C1121.36 (10)O3—C8—C9121.00 (12)
C8—O3—C10114.77 (12)O3—C8—C7120.42 (12)
C7—O4—C11116.63 (12)C9—C8—C7118.42 (12)
O2—C1—O1116.99 (12)O1—C9—C8115.95 (11)
O2—C1—C2125.28 (13)O1—C9—C4121.49 (12)
O1—C1—C2117.72 (11)C8—C9—C4122.56 (12)
C3—C2—C1121.77 (12)O3—C10—H10A108.3 (16)
C3—C2—C2i123.20 (11)O3—C10—H10B108.3 (15)
C1—C2—C2i115.03 (10)H10A—C10—H10B106 (2)
C2—C3—C4118.80 (12)O3—C10—H10C108.6 (16)
C2—C3—C12121.60 (13)H10A—C10—H10C115 (2)
C4—C3—C12119.59 (12)H10B—C10—H10C110 (2)
C5—C4—C9117.13 (12)O4—C11—H11A111.7 (13)
C5—C4—C3124.03 (12)O4—C11—H11B112.6 (11)
C9—C4—C3118.80 (12)H11A—C11—H11B108.8 (17)
C6—C5—C4121.74 (13)O4—C11—H11C104.2 (11)
C6—C5—H5119.7 (11)H11A—C11—H11C107.7 (16)
C4—C5—H5118.6 (11)H11B—C11—H11C111.8 (16)
C5—C6—C7119.83 (13)C3—C12—H12A111.0 (12)
C5—C6—H6119.7 (13)C3—C12—H12B110.3 (14)
C7—C6—H6120.5 (13)H12A—C12—H12B107.2 (17)
O4—C7—C6124.46 (12)C3—C12—H12C110.3 (12)
O4—C7—C8115.26 (12)H12A—C12—H12C110.5 (18)
C6—C7—C8120.28 (13)H12B—C12—H12C107.4 (17)
C9—O1—C1—O2−179.03 (12)C5—C6—C7—O4178.75 (12)
C9—O1—C1—C21.45 (18)C5—C6—C7—C8−1.0 (2)
O2—C1—C2—C3−178.65 (14)C10—O3—C8—C987.17 (17)
O1—C1—C2—C30.83 (19)C10—O3—C8—C7−97.47 (17)
O2—C1—C2—C2i1.3 (2)O4—C7—C8—O36.82 (18)
O1—C1—C2—C2i−179.20 (11)C6—C7—C8—O3−173.39 (12)
C1—C2—C3—C4−2.0 (2)O4—C7—C8—C9−177.70 (11)
C2i—C2—C3—C4178.01 (13)C6—C7—C8—C92.09 (19)
C1—C2—C3—C12178.72 (13)C1—O1—C9—C8176.73 (11)
C2i—C2—C3—C12−1.3 (2)C1—O1—C9—C4−2.48 (18)
C2—C3—C4—C5−176.43 (13)O3—C8—C9—O1−5.18 (18)
C12—C3—C4—C52.8 (2)C7—C8—C9—O1179.37 (11)
C2—C3—C4—C91.01 (19)O3—C8—C9—C4174.02 (12)
C12—C3—C4—C9−179.71 (13)C7—C8—C9—C4−1.42 (19)
C9—C4—C5—C61.4 (2)C5—C4—C9—O1178.84 (11)
C3—C4—C5—C6178.94 (13)C3—C4—C9—O11.22 (19)
C4—C5—C6—C7−0.8 (2)C5—C4—C9—C8−0.32 (19)
C11—O4—C7—C6−0.66 (19)C3—C4—C9—C8−177.94 (12)
C11—O4—C7—C8179.12 (12)
Symmetry codes: (i) −x, y, −z+1/2.
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C6—H6···Cg1ii0.96 (2)2.86 (2)3.676 (2)143.5 (18)
Symmetry codes: (ii) x, −y, z−1/2.
Table 1
Hydrogen-bond geometry (Å, °) top
D—H···AD—HH···AD···AD—H···A
C6—H6···Cg1i0.96 (2)2.86 (2)3.676 (2)143.5 (18)
Symmetry codes: (i) x, −y, z−1/2.
Acknowledgements top

HKF and SRJ thank the Malaysian Government and Universiti Sains Malaysia for the Science Fund grant No. 305/PFIZIK/613312. SRJ thanks Universiti Sains Malaysia for a post–doctoral research fellowship. HKF also thanks Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012.

references
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