2,3-Dibromo-3-phenyl-1-(3-phenylsydnon-4-yl)propan-1-one

In the title compound [systematic name: 4-(2,3-dibromo-3-phenylpropanoyl)-3-phenyl-1,2,3-oxadiazol-3-ylium-5-olate], C17H12Br2N2O3, the oxadiazole ring is essentially planar, with a maximum deviation of 0.001 (3) Å. The central oxadiazole ring makes dihedral angles of 73.3 (2) and 29.0 (2)° with the adjacent and remote phenyl rings, respectively. In the crystal, adjacent molecules are connected by C—H⋯O hydrogen bonds, forming a supramolecular chain along the c axis. There is an intramolecular C—H⋯O hydrogen bond, which generates an S(6) ring motif.


Comment
Sydnones constitute a well-defined class of mesoionic compounds that contain the 1,2,3-oxadiazole ring system. The study of sydnones still remains a field of interest because of their electronic structure and also because of the varied types of biological activities (Rai et al., 2008). Recently, sydnone derivatives were found to exhibit promising anti-microbial properties (Jyothi et al., 2008). Chalcones were obtained by the base-catalyzed condensation of 4-acetyl-3-aryl sydnones with aromatic aldehydes in alcoholic medium employing sodium hydroxide as catalyst at 0-5 °C. Bromination of chalcones with bromine in glacial acetic acid afforded dibromo chalcones (Rai et al., 2007).
The molecular structure of the title compound is shown in Fig In the crystal, (Fig. 2), the adjacent molecules are connected by intra and intermolecular C10-H10A···O2 and C13-H13A···O2 (Table 1) hydrogen bonds forming supramolecular chains along the c-axis. There is an intramolecular C-H···O hydrogen bond, which generates an S(6) ring motif.
Experimental 1-(3 1 -Phenylsydnon-4 1 -yl)-3-(phenyl)-propen-1-one (0.01 mol) was dissolved in glacial acetic acid (2-30 ml) by gentle warming. A solution of bromine in glacial acetic acid (30% w/v) was added to it with constant stirring till the yellow color of the bromine persisted. The reaction mixture was stirred at room temperature for 1-2 hours. The solid which separated was filtered, washed with methanol and dried. It was then recrystallized from ethanol. Crystals suitable for X-ray analysis were obtained from 1:2 mixtures of DMF and ethanol by slow evaporation.

Special details
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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.