7,7′-Dihy­droxy-4,4′-dimethyl-3,4-dihydro-2H,2′H-4,6′-bichromene-2,2′-dione

P S Pereira Silva; Mehtab Parveen; Akhtar Ali; Ali Mohammed Malla; M Ramos Silva

doi:10.1107/S160053681005244X

. 2010 Dec 18;67(Pt 1):o201. doi: 10.1107/S160053681005244X

7,7′-Dihydroxy-4,4′-dimethyl-3,4-dihydro-2H,2′H-4,6′-bichromene-2,2′-dione

P S Pereira Silva ^a, Mehtab Parveen ^b, Akhtar Ali ^b, Ali Mohammed Malla ^b, M Ramos Silva ^a,^*

PMCID: PMC3050332 PMID: 21522703

Abstract

The title compound, C₂₀H₁₆O₆, which contains one chiral centre, crystallizes as a racemate. The mean planes of the two coumarin units make a dihedral angle of 88.07 (2)°. The pyrone ring containing the chiral centre adopts a sofa conformation. In the crystal, four molecules are linked by O—H⋯O hydrogen bonds, forming a tetrameric ring with graph-set motif R ₄ ⁴(32). These tetramers are further linked by O—H⋯O hydrogen bonds into a three-dimensional network.

Related literature

For the chemical reactivity and bioactivity of coumarins and derivatives, see: Fylaktakidou et al. (2004 ▶). For a review on bicoumarins, see: Basa (1988 ▶). For the synthesis of bicoumarins, see: Ilyas & Parveen (1996 ▶); Sharma et al. (1977 ▶); Gašparová et al. (2009 ▶). For the synthesis of the title compound, see: Parveen et al. (1991 ▶). For hydrogen-bond motifs, see: Etter et al. (1990 ▶).

Experimental

Crystal data

C₂₀H₁₆O₆
M _r = 352.33
Monoclinic,
a = 9.0432 (2) Å
b = 11.5111 (2) Å
c = 17.2212 (4) Å
β = 110.870 (1)°
V = 1675.06 (6) Å³
Z = 4
Mo Kα radiation
μ = 0.10 mm⁻¹
T = 293 K
0.39 × 0.29 × 0.22 mm

Data collection

Bruker APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ▶) T _min = 0.863, T _max = 0.977
44743 measured reflections
4457 independent reflections
3459 reflections with I > 2σ(I)
R _int = 0.032

Refinement

R[F ² > 2σ(F ²)] = 0.040
wR(F ²) = 0.109
S = 1.06
4457 reflections
239 parameters
H-atom parameters constrained
Δρ_max = 0.24 e Å⁻³
Δρ_min = −0.19 e Å⁻³

Data collection: APEX2 (Bruker, 2003 ▶); cell refinement: SAINT (Bruker, 2003 ▶); 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: SHELXL97.

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S160053681005244X/bt5436sup1.cif

e-67-0o201-sup1.cif^{(20.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S160053681005244X/bt5436Isup2.hkl

e-67-0o201-Isup2.hkl^{(214KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O3—H3⋯O5ⁱ	0.82	2.13	2.9406 (13)	169
O6—H6⋯O2ⁱⁱ	0.82	1.91	2.7024 (15)	161

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

Acknowledgments

This work was supported by the Fundação para a Ciência e a Tecnologia (FCT) under the scholarship SFRH/BD/38387/2008.

supplementary crystallographic information

Comment

Studies of natural and synthetic coumarins and its derivatives have been present for a number of years. Coumarins and their derivatives are characterized by excellent chemical reactivity and bioactivity (Fylaktakidou et al., 2004). Bicoumarins are a comparatively new class of naturally occurring compounds (Basa, 1988) and are reputed for their biological activities such as anticoagulant, anticancer, antifungal agents. Only few bicoumarins have been synthesized (Ilyas & Parveen, 1996; Sharma & Seshadri, 1977; Gašparová et al., 2009). Considering the biological importance and scarcity of work on coumarin dimer a novel coumarin dimer 7,7'-dihydroxy-4,4'-dimethyl-3,4-dihydro-2H,2'H-4,6'- bichromene-2,2'-dione (I) was synthesized by the reinvestigation of synthesis of 7-hydroxy-4-methyl coumarin with the condensation of resorcinol and ethyl acetoacetate in different molar ratio using catalytic amount of polyphospharic acid (PPA) (Parveen et al., 1991). The increase in molar ratio of ethyl acetoacetate leads to a slight increase of coumarin dimer (I).

The title compound, (I), Fig. 1, has one chiral carbon atom (the C11 atom). Both enantiomers are present in the crystal structure, forming a racemate.

In the molecule of (I), the mean planes of the two coumarin units make a dihedral angle of 88.07 (2). In one of the coumarin units, the the dihedral angle between the least-squares planes of the pyrone and benzene rings is 3.36 (6)°. In the other coumarin unit the pyrone ring adopts an envelope conformation and the dihedral angle with the aromatic ring is 13.23 (6)°.

In the crystal, the molecules are linked by O—H···O hydrogen bonds (Fig. 2, Table 2) forming rings with four molecules, graph-set motif R₄⁴(32), according to the Etter's graph-set theory (Etter et al., 1990), centered about inversion centres. These rings are linked, with each molecule participating in two rings, forming a three-dimensional network. The structure is stabilized further by weak C—H···O hydrogen bonds.

Experimental

Polyphospharic acid was prepared by mixing orthophosphoric acid (15 mL) and phosphorus pentaoxide (23.5 g) followed by heating on a water bath for 1.5 hr. A catalytic amount of polyphosphoric acid (160 g) was added to resorcinol (11 g, 100 mmol) and ethyl acetoacetate (13 mL, 100 mmol) and was heated on a water bath (75–80 °C) for 20 min. with stirring. The viscous mixture was then poured into ice cold water and the resulting solid (18 g, m.p. 180 °C) was crystallized with EtOH as shinning crystal (7 g), it was characterized as 7-hydroxy-4-methyl coumarin by comparison with authentic sample. The mother liquor showed the presence of two bands I&II (TLC, silica-gel, benzene-ethylacetate 2:1) which was separated into individual compounds by preparative thin layer chromatography in the same solvent. The compound I was identified as 7-hydroxy-4-methyl coumarin while the compound II (m.p. 305 °C) was characterized as a novel coumarin dimer, (I), by IR, ¹H NMR, ¹³C NMR & MS spectra.