4-[3-(1-Naphthyloxymethyl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-6-yl]-3-p-tolylsydnone

In the title sydnone compound, C24H18N6O3S {systematic name: 4-[3-(1-naphthyloxymethyl)-7H-1,2,4-triazolo[3,4-b][1,3,4]thiadiazin-6-yl]-3-p-tolyl-4,5-dihydro-1,2,3-oxadiazol-3-ium-5-olate} an intramolecular C—H⋯O hydrogen bond generates an S(6) ring motif. The 3,6-dihydro-1,3,4-thiadiazine ring adopts a twist-boat conformation. The essentially planar 1,2,3-oxadiazole and 1,2,4-triazole rings [maximum deviations of 0.006 (1) and 0.008 (1) Å, respectively] are inclined to one another at interplanar angle of 44.11 (4)°. The naphthalene unit forms an interplanar angle of 66.40 (4)° with the 1,2,4-triazole ring. In the crystal packing, pairs of intermolecular C—H⋯O hydrogen bonds link adjacent molecules into dimers incorporating R 2 2(12) ring motifs. Further stabilization is provided by weak C—H⋯π interactions.


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 a fruitful development in heterocyclic chemistry (Baker et al., 1949). The study of sydnones still remains a field of interest because of their electronic structures 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).

Experimental
An equimolar mixture of 3-naphthyloxymethyl-4-amino-5-mercapto-1,2,4-triazoles (0.01 mol) and 4-bromoacetyl-3-tolylsydnones (0.01 mol) in absolute ethanol was heated under reflux for 10-12 h. The solution was concentrated, cooled to room temperature and neutralized with 10 % sodium bicarbonate solution. Solid product formed was collected by filtration supplementary materials sup-2 and recrystallized from ethanol. Single crystals for X-ray analysis were obtained from a 1:2 mixture of DMF and ethanol by slow evaporation.

Refinement
All hydrogen atoms were located from difference Fourier map [range of C-H = 0.945 (17)-1.028 (16) Å] and allowed to refine freely. Fig. 1. The molecular structure of the title compound, showing 30% probability displacement ellipsoids for non-H atoms and the atom-numbering scheme. An intramolecular hydrogen bond is shown as dashed line.   Glazer, 1986) operating at 100.0 (1)K.

Figures
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.