Crystal structure of 8-ethoxy-3-(4-nitrophenyl)-2H-chromen-2-one

In the title compound, C17H13NO5, the coumarin ring system is essentially planar (r.m.s. deviation = 0.008 Å). The nitrophenyl ring makes a dihedral angle of 25.27 (9)° with the coumarin ring plane. The nitro group is almost coplanar with the phenyl ring to which it is attached, making a dihedral angle of 4.3 (3)°. The ethoxy group is inclined to the coumarin ring plane by 4.1 (2)°. Electron delocalization was found at the short bridging C—C bond with a bond length of 1.354 (2) Å. In the crystal, molecules are linked via C—H⋯O hydrogen bonds, forming sheets in the bc plane. The sheets are linked via π–π stacking [centroid–centroid distances = 3.5688 (13) and 3.7514 (13) Å], forming a three-dimensional structure.


S1. Comment
Coumarin derivatives are found to be one of the major groups of compounds used as fluorescent brighteners (Tian et al., 2000) or fluorescent dyes and they have exhibited good bleed fastness and durability for coating plastics or in acrylic lacquers. Several natural or synthetic coumarins with various hydroxyl and other substituents were found to inhibit lipid peroxidation and to scavenge hydroxyl radicals and superoxide anions (Naveen et al., 2007). As a part of our ongoing research on coumarins (Naveen et al., 2006a,b), we report herein on the synthesis, characterization and crystal structure of the title compound. The compound is being assessed for biological activity.

S2. Synthesis and crystallization
A mixture of 0.512 g m (3.083 mmol) of 3-ethoxysalicylaldehyde and 0.50 g m (3.083 mmol) of 4-nitro phenylacetonitrile were dissolved in ethanol (25 ml), followed by the addition of 0.525 g m (6.16 mmol) of piperidine and then the reaction mixture was stirred at room temperature for 3 h. The completion of the reaction was monitored by thin layer chromatography [petroleum ether and ethyl acetate (8:2 v/v)]. After completion the reaction mixture was filtered and washed with diethylether giving a yellow precipitation. This product was refluxed with 10% acetic acid for 2 s and then the crude product was filtered and washed with water. It was further purified by recrystallization using acetone as solvent to give yellow crystals of the title compound in good yield (m.

S3. Refinement
Crystal data, data collection and structure refinement details are summarized in Table 2. The hydrogen atom were fixed geometrically (C-H= 0.93-0.96 Å) and allowed to ride on their parent atoms with U iso (H) =1.5U eq (C-methyl) and = 1.2U eq (C) for other H atoms.

Figure 1
A view of the molecular structure of the title compound, with atom labelling. Displacement ellipsoids are drawn at the 50% probability level.

Figure 2
A viewed along the b axis of the crystal packing of the title compound.

Special details
Experimental. Commercially available chemicals were used directly as received. 1 H NMR was recorded at 400 MHz in Dimethylsulfoxide (DMSO-d 6 ). 13 C NMR was recorded at 400 MHz in DMSO-d 6 . Mass spectra was recorded on a Jeol SX 102=DA-6000 (10 kV) fast atom bombardment (FAB) mass spectrometer and IR spectra was recorded on a Nicolet 5700 F T-IR instrument as KBr discs. Geometry. Bond distances, angles etc. have been calculated using the rounded fractional coordinates. All su's are estimated from the variances of the (full) variance-covariance matrix. The cell e.s.d.'s are taken into account in the estimation of distances, angles and torsion angles Refinement. Refinement on F 2 for ALL reflections except those flagged by the user for potential systematic errors. Weighted R-factors wR and all goodnesses 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 observed criterion of F 2 > σ(F 2 ) is used only for calculating -R-factor-obs 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.