Isopropyl (3,4-dimethyl-5,5-dioxo-4H-pyrazolo[4,3-c][1,2]benzothiazin-2-yl)acetate

In the title molecule, C16H19N3O4S, the heterocyclic thiazine ring adopts a half-chair conformation, with the S and N atoms displaced by 0.547 (2) and −0.254 (3) Å, respectively, from the plane formed by the remaining atoms. In the crystal, weak C—H⋯N and C—H⋯O hydrogen bonds link the molecules.

In the title molecule, C 16 H 19 N 3 O 4 S, the heterocyclic thiazine ring adopts a half-chair conformation, with the S and N atoms displaced by 0.547 (2) and À0.254 (3) Å , respectively, from the plane formed by the remaining atoms. In the crystal, weak C-HÁ Á ÁN and C-HÁ Á ÁO hydrogen bonds link the molecules.
In the title molecule ( Fig. 1), the heterocyclic thiazine ring adopts a half-chair conformation, with atoms S1 and N1 displaced from the plane C1\C6\C7\C8 by 0.547 (2)  water to obtain the title compound as a white crystalline product. Yellow prisms of (I) of approximate size 0.10-0.30 mm were grown from a solution of 0.5 g of the title compound dissolved in 15 ml mixture of methanol and chloroform (1:1); the methanol contained 0.5% of moisture. Yield of the recrystallised product : 80%

Refinement
All the hydrogen atoms were discernible in the difference electron density map. However, they were positioned into the idealized positions and refined by the riding-model approximation. Used constraints: C-H = 0.98, 0.99, 1.00 and 0.95 Å for methyl, methylene, methine and aryl H-atoms, respectively. U iso (H) = 1.5U eq (methyl C-atoms) and 1.2U eq (non-methyl C-atoms). The methyl groups were allowed to rotate about their axes during the refinement. 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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq S1 0.35224 (5