4-Hydroxy-2-methyl-1,1-dioxo-N-phenyl-2H-1λ6,2-benzothiazine-3-carboxamide

In the title molecule, C16H14N2O4S, the thiazine ring adopts a twist chair conformation with the N and adjacent C atom displaced by 0.966 (3) and 0.386 (4) Å, respectively, on the same side of the mean plane formed by the remaining ring atoms. The dihedral angle between the mean planes of the benzene rings is 37.65 (10)°. The molecular structure features an intramolecular O—H⋯O hydrogen bond, which generates an S(6) ring. In the crystal, molecules are linked by N—H⋯O and C—H⋯O hydrogen bonds.


Parvez Comment
In continuation of our research on the synthesis of potentially biologically active 1,2-benzothiazine 1,1-dioxide derivatives (Siddiqui et al., 2007;Ahmad et al., 2010) herein, we report the synthesis and crystal structure of the title compound.
The bond distances and angles in the title compound ( Fig. 1) agree very well with the corresponding bond distances and angles reported in closely related compounds (Siddiqui et al., 2008;2009). The heterocyclic thiazine ring adopts a twist chair conformation with atoms S1 and C1 displaced by 0.966 (3) and 0.386 (4) Å, respectively, on the same side from the mean plane formed by the remaining ring atoms (r.m.s. deviation 0.004 for N1/C6-C8 atoms). The mean-plane of the benzene rings C1-C6 and C11-C16 are inclined at a dihedral angle 37.65 (10)° with respect to each other.

Refinement
All H atoms were positioned geometrically and refined using a riding model, with O-H = 0.84, N-H = 0.88 Å and C-H = 0.95 and 0.98 Å, for aryl and methyl H-atoms, respectively. The U iso (H) were allowed at 1.5U eq (O) or 1.2U eq (C/N).  The molecular structure of the title compound with displacement ellipsoids drawn at the 50% probability level. H atoms are presented as small spheres of arbitrary radius.

Figure 2
A part of the unit cell showing hydrogen bonding interactions (dotted lines) in the crystal structure of the title compound.
H atoms non-participating in hydrogen-bonding were omitted for clarity. 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 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.