2-(3,4-Dimethyl-5,5-dioxo-2H,4H-pyrazolo[4,3-c][1,2]benzothiazin-2-yl)-N′-(2-thienylmethylidene)acetohydrazide

In the title molecule, C18H17N5O3S2, the heterocyclic thiazine ring adopts a twist boat conformation, with the S and N atoms displaced by 0.480 (7) and 0.205 (8) Å, respectively, on opposite sides of the mean plane formed by the remaining ring atoms. The pyrazole and benzene rings are tilted at an angle of 10.9 (2)° with respect to one another. The crystal structure is stabilized by intermolecular N—H⋯O and C—H⋯N hydrogen bonds, resulting in dimers forming nine-membered rings of graph-set motif R 2 2(9). In addition, intermolecular C—H⋯O interactions result in chains of molecules along the c axis, further consolidating the crystal packing.

In the title molecule, C 18 H 17 N 5 O 3 S 2 , the heterocyclic thiazine ring adopts a twist boat conformation, with the S and N atoms displaced by 0.480 (7) and 0.205 (8) Å , respectively, on opposite sides of the mean plane formed by the remaining ring atoms. The pyrazole and benzene rings are tilted at an angle of 10.9 (2) with respect to one another. The crystal structure is stabilized by intermolecular N-HÁ Á ÁO and C-HÁ Á ÁN hydrogen bonds, resulting in dimers forming ninemembered rings of graph-set motif R 2 2 (9). In addition, intermolecular C-HÁ Á ÁO interactions result in chains of molecules along the c axis, further consolidating the crystal packing.

Comment
Benzothiazines represent a class of heterocyclic compounds which exhibit a diverse range of biological activities like antiinflammatory (Lombardino et al., 1973), antibacterial (Zia-ur-Rehman et al., 2006), etc. Continuing our research on the synthesis of potential biologically active derivatives of benzothiazines, we have fused a pyrazole ring with benzothiazine nucleus and the resulting compounds were found to be potent antioxidants (Ahmad et al., 2010). Herein we report the synthesis and crystal structure of the title compound.
In the title compound ( Fig. 1), the bond distances and angles agree with the cortresponding bond distances and angles reported in a closely related compound (Ahmad et al., 2010). The heterocyclic thiazine ring adopts a twist boat conformation with atoms S1 and N1 displaced by 0.480 (7)  The structure is stabilized by intermolecular hydrogen bonds N4-H4N···O3 and C12-H12A···N5, resulting in dimers forming nine membered rings in R 2 2 (9) graph set motif (Bernstein et al., 1994). In addition, intermolecular interactions C12-H12B···O1 leading to chains of molecules along the c-axis further consolidate the crystal packing; the details of hydrogen bonding geometry have been provided in Tab. 1 and Fig. 2.

Refinement
The absolute structure parameter indicated the presence of racemic twinning. Therefore, a TWIN instruction with the default matrix R = (-1 0 0 , 0 -1 0, 0 0 -1) and a BASF with one parameter was used in the final round of least-squares refinement  Fig. 1. The title molecule plotted with the displacement ellipsoids at 30% probability level (Farrugia, 1997

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 > σ(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.