N-(2-Oxo-2H-chromen-3-yl)benzamide

The phenyl ring in title molecule, C16H11NO3, forms a dihedral angle of 7.69 (6)° with the fused ring system. The observed conformation is stabilized by intramolecular N—H⋯O and C—H⋯O interactions. In the crystal, supramolecular chains are formed along the b axis which are mediated by π–π interactions [centroid–centroid distance = 3.614 (2) Å].

The phenyl ring in title molecule, C 16 H 11 NO 3 , forms a dihedral angle of 7.69 (6) with the fused ring system. The observed conformation is stabilized by intramolecular N-HÁ Á ÁO and C-HÁ Á ÁO interactions. In the crystal, supramolecular chains are formed along the b axis which are mediated byinteractions [centroid-centroid distance = 3.614 (2) Å ].

Related literature
For the biological activity of imidazoles, see: Yohjiro et al. (1990). For the anti-inflammatory activity of the title compound, see: Maddi et al. (2007). Semi-empirical quantum chemical calculations were performed using MOPAC2009 Stewart (2009 Table 1 Hydrogen-bond geometry (Å , ).

Comment
Oxazoles are very useful synthetic intermediates used for the generation of imidazoles that possess a wide spectrum of biological activities such as herbicidal, anti-bacterial, anti-fungal, etc. (Yohjiro et al., 1990). During attempts designed to synthesize oxazoles containing various substituents at different positions in the benzene ring, the title compound, (I), was obtained unexpectedly by the formation of a chromen derivative instead of the anticipated oxazole. Compound (I) is a known species and has been shown to be pharmaceutically important as it possesses anti-inflammatory activity (Maddi et al., 2007).
There is a twist in the molecule of (I), Fig. 1, so that the pendent benzene ring is not co-planar with the rest of the molecule. This is seen in the value of the O3-C10-C11-C12 torsion angle of -166.43 (15) °, and in the dihedral formed between the fused ring system and benzene ring of 7.69 (6) °. The overall conformation of the molecule is stabilised by intramolecular N-H···O and C-H···O interactions, Table 1, which close S(5) and S(6) hydrogen bond ring motifs, respectively.
The most prominent feature of the crystal packing is the formation of supramolecular chains along the b axis mediated by π-π interactions between the ring centroids of the (O2,C1,C2,C7-C9) and (C2-C7) i rings of 3.614 (2) Å of translationally related molecules; symmetry operation i: x, 1+y, z.
Semi-empirical Quantum Chemical Calculations were performed on experimental structure using MOPAC2009 program (Stewart, 2009) to optimize the molecule with the Austin Model 1 (AM1) approximation, together with the restricted Hartree-Fock closed-shell wavefunction. Minimisations were terminated at an r.m.s. gradient of less than 1.0 kJ mol -1 Å -1 .
These calculations gave a heat of formation = -213.437 kJ for (I). The ionization potential, dipole moment and self consistency field (SCF) factor were calculated as 9.033 eV, 1.798 Debye and 73, respectively.

Experimental
A mixture of orthohydrothoxy benzaldehyde (0.25 mol), benzoyl amino acetic acid (0.25 mol), acetyl acetate (0.30 mol), and anhydrous sodium acetate (0.25 mol) were taken in a 500 ml round bottom flask and heated on an electric hot plate with constant stirring. After complete liquefaction, the flask was transferred to a sand bath and further heated for 2 h. Ethanol (100 ml) was added slowly to the flask and the mixture was allowed to stand overnight. The crystalline product obtained was filtered with ice-cold alcohol and then with boiling water. The crude product was crystallised from ethanol (95%) to obtain the final product (75 % yield, m.pt. 432 K). The colorless crystals were obtained by slow evaporation from an ethanol solution.

Refinement
The C-bound H atoms were geometrically placed (C-H = 0.93 Å) and refined as riding with U iso (H) = 1.2U eq (parent atom).