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

In the crystal structure of the title compound, C9H9NO3S, there is distorted tetrahedral geometry around the S atom. The sulfonyl group is almost normal to the benzene ring, while the carbonyl O atom and methyl C atom are on opposite sides of this ring. The heterocyclic ring adopts a half-boat conformation with the S atom out of the plane. The molecules are dimerized by hydrogen bonding involving the benzene ring and the sulfonyl group. These dimers are linked to each other in the same way. There is an intramolecular hydrogen bond between a methyl C—H group and a sulfonyl O atom, and a π–π interaction between the aromatic rings of two dimers at a centroid-to-centroid distance of 3.6373 (13) Å.

In the crystal structure of the title compound, C 9 H 9 NO 3 S, there is distorted tetrahedral geometry around the S atom. The sulfonyl group is almost normal to the benzene ring, while the carbonyl O atom and methyl C atom are on opposite sides of this ring. The heterocyclic ring adopts a half-boat conformation with the S atom out of the plane. The molecules are dimerized by hydrogen bonding involving the benzene ring and the sulfonyl group. These dimers are linked to each other in the same way. There is an intramolecular hydrogen bond between a methyl C-H group and a sulfonyl O atom, and ainteraction between the aromatic rings of two dimers at a centroid-to-centroid distance of 3.6373 (13) Å .

Comment
Benzothiazines belong to an important heterocyclic class of compounds which find a number of applications in medicinal chemistry. Derivatives of 2,1-benzothiazines were reported to possess potent biological activities such as lipoxygenase inhibition and are used as drugs for heart diseases (Misu, & Togo, 2003). These are used as intermediate precursors for the preparation of drugs used for curing Tuberculosis (Harmata et al., 2004). The importance of 2,1-benzothiazine derivatives in medicinal chemistry has brought enormous attention to their synthesis. Herein, we report the crystal structure of the title compound.
In the title compound the bond distances S1-N1 [1.6429 (13) Å] and S1-C8 [1.7514 (17)  All the atoms in heterocyclic thiazine as well as C-atoms of phenyl ring are nearly planer except that of S1. The S1 is displaced by 0.7834 (15) Å from the plane (a) defined by (C1 to C8, N1) and C-atom of methyl group is at a distance of 0.340 (3) Å from it. Thus the atoms of the two rings form a long half boat confirmation. The plane (b) defined by the atoms (O1,S1,O2) makes a dihedral angle of 89.81 (6)° to the plane (a) and hence these two planes are almost normal to each other. The O1-atom is at longest distance of −2.1912 (16) Å from plane (a). In the asymmetric unit there is an intramolecular H-bond as given in Table 2. The confirmation of the hetrocyclic ring in terms of the puckering parameters (Cremer & Pople, 1975) is described by; Q = 0.5767 (14) Å, θ = 54.98 (16)° and φ = 359.7 (2)°. The title compound is basically dimerized by H-bonding through C2-H2···O1 i (i = −x, −y + 2, −z + 1) as shown in Fig 2. It is interesting that the ring formed in dimer is of twelve bonds to which the methyl groups adopt cis, trans position. The dimers are linked to each other by symmetry code ii = x, y − 1, z + 1. The closest interaction [3.283 (2) Å] occurs between O1···O1 iii (symmetry code: iii = −x, −y + 2, −z), other than atoms involved in intermolecular H-bond. There is no X-H···Cg bond, however there exist a π-π interaction between the aromatic rings of two dimers at a distance of 3.6373 (13) Å by the symmetry operation 1 − x, 1 − y, 1 − z.

Experimental
The title compound (I) was synthesized using the reported procedure (Lombardino, 1972) and crystals were grown by slow evaporation from a solution of CH 3 OH at 298 K.
supplementary materials sup-2 Figures   Fig. 1. ORTEP drawing of the title compound, C 10 H 11 NO 3 S, with the atom numbering scheme. The thermal ellipsoids are drawn at the 50% probability level.  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.