4-Formyl-3-p-tolylsydnone

In the title compound, C10H8N2O3, the oxadiazole ring is essentially planar, with a maximum deviation of 0.006 (1) Å for the two-connected N atom. The mean planes through the aldehyde unit and the methyl-substituted phenyl ring make interplanar angles of 13.60 (9) and 59.69 (4)°, respectively, with the oxadiazole ring. In the crystal structure, adjacent molecules are interconnected into a two-dimensional array parallel to (100) by intermolecular C—H⋯O hydrogen bonds.


Comment
Sydnones constitute a well-defined class of mesoionic compounds consisting of 1,2,3-oxadiazole ring system. The introduction of the concept of mesoionic structure for certain heterocyclic compounds in the year 1949 has proved to be fruitful development in heterocyclic chemistry. The study of sydnones still remains a field of interest because of their electronic structure and also because of the various types of biological activities displayed by some of them. Interest in sydnone derivatives has also been encouraged by the discovery that they exhibit various pharmacological activities (Hedge et al., 2008;Rai et al., 2008).
These 4-formyl sydnone will be used for the preparation of a new series of α,β-unsaturated carbonyl compounds (namely chalcones) by condensation with appropriate ketones or aldehydes. These α,β-unsaturated carbonyl compounds will be utilized for the synthesis of a variety of novel heterocyclic compounds like pyrazolines, pyrazole etc carrying sydnone moiety.
Experimental N-Methylformanilide (0.01 mol) and phosphoryl chloride (0.01 mol) were mixed and added into 3-(p-tolyl)sydnone (0.01 mol) portion-wise. The reaction mixture was then stirred for about 1 h under cold condition. After standing overnight, it was poured into ice cold water with stirring. The solid obtained was filtered, dried and recrystallized from ethanol. Single crystals suitable for X-ray analysis were obtained from a 1:2 mixture of DMF and ethanol by slow evaporation.

Refinement
All hydrogen atoms were placed in their calculated positions, with C-H = 0.93 or 0.96 Å, and refined using a riding model with U iso = 1.2 or 1.5 U eq (C). A rotating group model was used for the C10 methyl group. Fig. 1. The molecular structure of the title compound, showing 50% probability displacement ellipsoids for non-H atoms and the atom-numbering scheme.

Special details
Experimental. The crystal was placed in the cold stream of an Oxford Cryosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1)K.
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.