4-Hydroxy-3-[(E)-3-phenylprop-2-enoyl]-2H-chromen-2-one

In the title molecule, C18H12O4, the phenyl ring is twisted by 23.2 (1)° from the mean plane of the chromene system. In the crystal, weak intermolecular C—H⋯O hydrogen bonds link molecules into zigzag chains extending in the [010] direction. An intramolecular O—H⋯O hydrogen bond is also present.

In the title molecule, C 18 H 12 O 4 , the phenyl ring is twisted by 23.2 (1) from the mean plane of the chromene system. In the crystal, weak intermolecular C-HÁ Á ÁO hydrogen bonds link molecules into zigzag chains extending in the [010] direction. An intramolecular O-HÁ Á ÁO hydrogen bond is also present. Mo K radiation = 0.10 mm À1 T = 296 K 0.3 Â 0.14 Â 0.06 mm

Comment
In continuation of our structural and biological studies of coumarin derivatives (Mechi et al., 2009;Hamdi et al., 2010), we present the crystal structure of the title compound (I) -a new chalcone of the coumarin.
Consequently, the C10-O2 = 1.289 (5) Å is elongated as compared with its mean value found in 3-acetyl-4hydroxycoumarin (1.253 Å) (Traven et al., 2000) owing to the localization of the hydroxyl hydrogen (H2) between the O2 ketonic oxygen and the hydroxyl oxygen O1. The O1-H2 distance (0.99 (7) Å) in (I) is shorter than that in related compounds -C 18 H 10 O 7 (1.22 (7)  bond length (1.198 (5) Å) is less than that (1.210 Å) observed in 3-acetyl-4hydroxycoumarin (Traven et al., 2000). It was concluded that it was a substantial difference for stabilizing the H atom of the hydroxyl group when we changed the nature of the substituted R group (from H to Cl and to OCH3).
In the crystal structure, weak intermolecular C-H···O hydrogen bonds (Table 1)

Experimental
The new chalcone (I) was synthesized using the Claisen Schmidt reaction (Claisen & Claparede, 1881), by the condensation of 3-acetyl-4hydroxycoumarin (1g, 4.9 mmol) and aromatic benzaldehyde (6.4 mmol, 0.5 ml) in chloroform (5 ml) in the presence of one drop of piperidine. The mixture was refluxed in a water bath for 2 h. After cooling at room temperature, a yellow solid was obtained in good yield, filtered, washed with ethanol, and dried in air. Yellow block-shaped single crystals of the title compound, suitable for X-ray structure determination, were recrystalized by slow evaporation of dichloromethane (CH 2 Cl 2 ) at room temperature after several days. Yield: 1.1 g (80%). mp= 499K.   as those based on F, and R-factors based on ALL data will be even larger.