1,3-Dimethyl-5-methylsulfonyl-1H-pyrazolo[4,3-e][1,2,4]triazine

In the title compound, C7H9N5O2S, the pyrazolo[4,3-e][1,2,4]triazine fused-ring system is essentially planar [maximum deviation = 0.0420 (3) Å]. In the crystal, molecules related by twofold axes are linked into a molecular net via intermolecular C—H⋯O and C—H⋯N hydrogen bonds. π–π interactions are observed between the triazine and pyrazole rings of molecules related by the the twofold axis and inversion symmetry with centroid–centroid distances of 3.778 (3) and 3.416 (3) Å, respectively.

Data collection: KM4B8 (Gałdecki et al., 1996); cell refinement: KM4B8; data reduction: DATAPROC (Gałdecki et al., 1995); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: SHELXL97 and WinGX (Farrugia, 1999 Sulfones have proven to be valuable synthons for the synthesis of a wide variety of biologically active heterocyclic systems (Ingall, 1984). As an extension of our efforts directed towards the development of convenient synthetic approaches for the construction of biologically active heterocycles (Karczmarzyk et al., 2007), we report herein the crystal and molecular structure of the title compound.
The geometry (bond lengths, angles and planarity) of the title molecule (I) is very similar to those observed in closely related structures (Hirata et al., 1996;Rykowski et al., 2000). In the title molecule, a substitution by methylsulfonyl group in the 1,2,4-triazine ring results in a significant deformation of the endocyclic angles N2-C3-N4 of 130.3 (4)° and C3-N4-C5 of 110.6 (4)°. This effect is caused probably by the strong electron-withdrawing property of SO 2 CH 3 substituent and has been reported in similar structures (Cherng-Chyi et al., 1994).

Experimental
To a solution of 2,3-dimethyl-5-methylsulfanyl-1H-pyrazolo[4,3-e][1,2,4]triazine (1 mmol) in benzene (20 ml), water (30 ml), potassium manganate (VII) (3 mmol), catalitic amounts of tetrabuthylammonium bromide (0.2 mmol) and acetic acid (1.5 ml) were added. The reaction mixture was stirred at room temperature for 1 h. A saturated solution of Na 2 S 2 O 5 in water was then added to the mixture until the purple colour disappeared. The organic layer was separated and the aqueos phase was extracted with benzene (3x10 ml). The combined organic extracts were dried over anhydrous MgSO 4 and concentrated in vacuo. The residue was purified by column chromatography on silica gel (eluent: chloroform) to afford the title compound as a yellow solid. Crystals suitable for X-ray diffraction analysis were grown by slow evaporation of an ethanol solution.

Refinement
The H atoms were positioned geometrically and treated as riding on their C atoms, with C-H distances of 0.96 Å and were included in the refinement with U iso (H) = 1.5U eq (C). Fig. 1. The molecular structure of (I), with atom labels and 50% probability displacement ellipsoids for non-H atoms.  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.

sup-2 Figures
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.