4-Chlorophenyl 2-oxo-2H-chromene-3-carboxylate

In title compound, C16H9ClO4, the coumarin ring system is approximately planar [maximum deviation = 0.056 (1) Å] and is oriented with respect to the benzene ring at an angle of 22.60 (7)°. Intermolecular C—H⋯O hydrogen bonding is present in the crystal.


Comment
The coumarins and derivatives have demonstrated an ever-increasing variety of uses, including platelet anti-aggregating activity, anti-inflammatory activity (Kontogiorgis & Hadjipavlou-Litina, 2005), anti-tumor activity (Finn et al., 2002), anti-bacterials (Gursoy & Karali, 2003, and antiviral effect (Borges et al., 2005). So the title compound was synthesized according to the published method (Zhou et al., 2008). We report here the crystal structure of the title compound. In the title compound ( Fig. 1), the dihedral angle between the planes of coumarin and benzene ring is 22.60 (7)°. The packing view of the title compound is shown in Fig. 2, weak intermolecular C-H···O hydrogen bonding is present in the crystal (Table 1).
Experimental 2-Oxo-2H-chromene-3-carboxylic acid (0.02 mol) was added to 10 ml sulfurous oxychloride. The mixture was refluxed for 3 h, and then the resultant was removed with simple distillation to give 2-oxo-2H-chromene-3-carbonyl chloride (3.95 g). The compound can be used directly without purification. The solution of 4-chlorophenol (0.0165 mol) dissolved in dried methyl dichloride (15 ml) was added dropwise to a solution of 2-oxo-2H-chromene-3-acyl chloride (0.015 mol) dissolved in methyl dichloride (20 ml) and triethylamine (2.5 ml) at room temperature. The reaction mixture was refluxed for 6 h, (mornitored by TLC). The mixture was then neutralized with 5% HCl and washed with saturated NaHCO 3 and brine respectively. The organic phase was dried over Na 2 SO 4 and evaporated under the reduced pressure. The resulting residue was purified by column chromatography (ethyl acetate: petroleum ether) to give the pure compound. Single crystals suitable for X-ray analysis were obtained by slow evaporation of a mixed solvent (methyl dichloride: methanol) at room temperature.

Refinement
All H atoms were placed in calculated positions and refined in the riding model approximation, with C-H = 0.95 Å. The hydrogen atoms were refined in the riding model with U iso (H) = 1.2U eq (C).  The molecular structure of the title compound with the atom numbering, showing displacement ellipsoids at the 30% probability level.

Figure 2
A packing diagram of the title compound.

Special details
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 F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > σ(F 2 ) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.