2,3-Dibromo-3-(4-bromophenyl)-1-[3-(4-methoxyphenyl)sydnon-4-yl]propan-1-one

In the title compound {systematic name: 4-[2,3-dibromo-3-(4-bromophenyl)propanoyl]-3-(4-methoxyphenyl)-1,2,3-oxadiazol-3-ylium-5-olate}, C18H13Br3N2O4, the central oxadiazole ring, which is essentially planar with a maximum deviation of 0.016 (3) Å, makes dihedral angles of 29.98 (16) and 52.04 (16)°, respectively, with the terminal bromo-substituted and methoxy-substituted benzene rings. An intramolecular C—H⋯O hydrogen bond 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 antimicrobial 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), there is an intramolecular C8-H8A···O2 (Table 1) hydrogen bond, which generates an S(6) ring motif (Bernstein et al., 1995).
Experimental 1-(3 1 -Phenylsydnon-4 1 -yl)-3-(p-bromophenyl)-propen-1-one (0.01 mol) was dissolved in glacial acetic acid (25-30 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 colour 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 s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The 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 > 2σ(F 2 ) is used only for calculating Rfactors(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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq