6-Bromo-1-methyl-1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide

In the crystal structure of the title compound, C9H8BrNO3S, the thiazine ring is in the twisted form. In the crystal, pairs of intermolecular C—H⋯O hydrogen bonds form inversion dimers with an R 2 2(8) ring motif. Weak intermolecular C—H⋯Br and C—H⋯π interactions are also present.

In the crystal structure of the title compound, C 9 H 8 BrNO 3 S, the thiazine ring is in the twisted form. In the crystal, pairs of intermolecular C-HÁ Á ÁO hydrogen bonds form inversion dimers with an R 2 2 (8) ring motif. Weak intermolecular C-HÁ Á ÁBr and C-HÁ Á Á interactions are also present.

Comment
We have reported crystal structures of the synthesized derivatives of the benzothiazine molecule (Shafiq et al., 2008a;Shafiq et al., 2008b;Tahir et al., 2008;Arshad et al., 2008). Here we report the title compound (I), (Fig. 1), that belongs to this series of the structures.

Experimental
The title compound was prepared in a three step scheme following the reported procedure (Lombardino, 1972). In the first step, methyl-2-amino-5-bromobenzoate (92 mg, 4 mmol) was put in dichloromethane (10 ml) and this mixture was introduced into a round bottom flask. A solution of methanesulfonyl chloride (550 mg, 4.8 mmol) in dichloromethane (10 ml) was slowly added (10-15 minutes) to this mixture. The mixture was stirred at 60-70 °C for 2-3 days keeping pH of the mixture alkaline by triethylamine. After the completion of the reaction, the solvent was evaporated under reduced pressure to get methyl-5-bromo-2-[(methylsulfonyl)amino] benzoate.
In the third step methyl-5-bromo-2-[methyl(methylsulfonyl)amino]benzoate was cyclized. Therefore methyl-5-bromo-2-[methyl(methylsulfonyl)amino]benzoate (418.83 mg, 1.3 mmol) was introduced in DMF (5 ml) and added to the suspension of NaH (59.99 mg, 2.5 mmol) in DMF (10 ml). The mixture was stirred at room temperature for 3-4 h. Then the reaction mixture was poured into ice and clear solution was obtained. The pH of this solution was adjusted between 5-6. The precipitated crude product was recrystallized from ethanol. Yellow needle-shaped crystals of the title compound of suitable size for structure analysis were grown in this way.
supplementary materials sup-2 Refinement Though all the hydrogens were discernible in the difference electron density map, the H-atoms were situated into idealized positions, with C-H = 0.93, 0.96 and 0.97 Å for aryl, methyl and methylene H, resepctively, and constrained to ride on their parent atoms, with U iso (H) = xU eq (C), where x = 1.5 for methyl and 1.2 for other carrier atoms. Fig. 1. The title compound, with the atom-numbering scheme. The displacement ellipsoids are drawn at the 50% probability level. The H-atoms are shown by small circles of arbitrary radius. The dotted lines show the intramolecular H-bonds.

Fig. 2. A section of the title structure showing the dimers bind by the hydrogen bonds.
6-Bromo-1-methyl-1H-2,1-benzothiazin-4(3H)-one 2,2-dioxide  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.