(4-Hydroxy-1,1-dioxo-2H-1,2-benzothiazin-3-yl)(3-methoxyphenyl)methanone

In the title compoud, C16H13NO5S, the heterocyclic thiazine ring adopts a twist boat conformation with the S and N atoms displaced by 0.339 (5) and 0.322 (4) Å, respectively, on opposite sides of the mean plane formed by the remaining ring atoms. An intramolecular O—H⋯O interaction is present, forming a five-membered ring. The crystal structure is stabilized by intermolecular N—H⋯O hydrogen bonds, which result in chains along the b axis.

In the title compoud, C 16 H 13 NO 5 S, the heterocyclic thiazine ring adopts a twist boat conformation with the S and N atoms displaced by 0.339 (5) and 0.322 (4) Å , respectively, on opposite sides of the mean plane formed by the remaining ring atoms. An intramolecular O-HÁ Á ÁO interaction is present, forming a five-membered ring. The crystal structure is stabilized by intermolecular N-HÁ Á ÁO hydrogen bonds, which result in chains along the b axis.

Comment
Benzothiazine dioxide derivatives have been extensively explored in the past few decades since their very first derivatives were found to be potent anti-inflammatory and analgesic agents (Lombardino et al., 1971). Benzothiazines derivatives are now known to be anti-allergy (Ikeda et al., 1992), anti-inflammatory (Lombardino et al., 1973), bactericidal (Zia-ur-Rehman et al., 2006, etc. In continuation of our research on benzothiazine compounds (Ahmad et al., 2010, Siddiqui et al., 2007, we report the synthesis and crystal structure of the title compound (I) in this paper (Fig. 1).
Bond distances (Allen et al., 1987) and angles are as expected and agree with the corresponding bond distances and angles reported in closely related compounds (Siddiqui et al., 2008). The heterocyclic thiazine ring adopts a twist boat conformation with atoms S1 and N1 displaced by 0.339 (5) and 0.322 (4) Å , respectively, on the opposite sides from the mean plane formed by the remaining ring atoms.
The structure is stabilized by N-H···O type intermolecular hydrogen bonds which result in one dimensional chains of molecules extended along the b-axis; intramolecular interactions O3-H3O···O4 are also present resulting in five membered rings (Table 1 and Fig. 2).

Refinement
Though all the H atoms could be distinguished in the difference Fourier map the H-atoms bonded to C-atoms were included at geometrically idealized positions and refined in riding-model approximation with the following constraints: C-H distances were set to 0.93 and 0.96 Å, for aryl and methyl H-atoms, respectively; the H-atoms bonded to N and O were allowed to refine. The U iso (H) were allowed at 1.2U eq (parent atom). The final difference map was essentially featurless.  (4-Hydroxy-1,1-dioxo-2H-1,2-benzothiazin-3-yl)(3-methoxyphenyl)methanone

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.