3,3-Dibromo-1-ethyl-1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide

In the molecule of the title compound, C10H9Br2NO3S, the S atom is four-coordinated in distorted tetrahedral configuration. The heterocyclic thiazine ring adopts a twist conformation. An intramolecular C—H⋯O hydrogen bond results in the formation of a non-planar five-membered ring. In the crystal structure, intermolecular C—H⋯O hydrogen bonds link the molecules into infinite chains along the c axis.

In the molecule of the title compound, C 10 H 9 Br 2 NO 3 S, the S atom is four-coordinated in distorted tetrahedral configuration. The heterocyclic thiazine ring adopts a twist conformation. An intramolecular C-HÁ Á ÁO hydrogen bond results in the formation of a non-planar five-membered ring. In the crystal structure, intermolecular C-HÁ Á ÁO hydrogen bonds link the molecules into infinite chains along the c axis. Experimental Crystal data C 10 H 9 Br 2 NO 3 S M r = 383.06 Monoclinic, P2 1 =c a = 7.7979 (5) Å b = 11.9645 (7) Å c = 13.1231 (8) Table 1 Hydrogen-bond geometry (Å , ).

Comment
The synthesis of heterocyclic system is of continuing interest because a large number of biologically active molecules contain heterocyclic rings (Franzén, 2000). 2,1-Benzothiazine is a relatively unexplored ring system with respect to both its synthesis and biological activity, in which it belongs to an important heterocyclic class of compounds, although it finds a number of applications in medicinal chemistry. The derivatives of 2,1-benzothiazine are used as drugs for heart diseases and also show lipoxygenase inhibition activity (Misu & Togo, 2003). Recently we have reported the crystal structures of 1-ethyl-1H -2,1-benzothiazin-4(3H) one 2,2-dioxide, (II) (Shafiq et al., 2008) and 1-methyl-1H-2,1-benzothiazin-4(3H) one 2,2-dioxide, (III) (Tahir et al., 2008), in which they contain the same heterocyclic ring. We report herein the syntesis and crystal structure of the title compound, (I), which is obtained from the bromination of (II).
In the crystal structure, intermolecular C-H···O hydrogen bonds (Table 2) link the molecules into infinine chains along the c axis ( Fig. 2), in which they may be effective in the stabilization of the structure.

Refinement
The highest peak and deepest hole in the final difference electron density map are located 1.27 and 1.61 Å from Br1 and  Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. Hydrogen bond is shown as dashed line. 3,3-Dibromo-1-ethyl-1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide

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 > 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.