N-(2,3-Dimethyl-phen-yl)-4-hydr-oxy-2-methyl-2H-1,2-benzothia-zine-3-carboxamide 1,1-dioxide.

In the crystal structure of the title compound, C(18)H(18)N(2)O(4)S, the thia-zine ring adopts a distorted half-chair conformation. 1,2-Benzothia-zines of this kind have a wide range of biological activities and are mainly used as medicines in the treatment of inflammation and rheumatoid arthritis. The enolic H atom is involved in an intra-molecular O-H⋯O hydrogen bond, forming a six-membered ring. The mol-ecules arrange themselves into centrosymmetric dimers by means of inter-molecular N-H⋯O hydrogen bonds. A weak inter-molcular C-H⋯O inter-action is also present.

N-(3,4-Dimethyl-phen-yl)-4-hydr-oxy-2-methyl-2H-1,2-benzothia-zine-3-carboxamide 1,1-dioxide.

1,2-Benzothia-zines similar to the title compound, C(18)H(18)N(2)O(4)S, are well known in the literature for their biological activities and are used as medicines in the treatment of inflammation and rheumatoid arthritis. The thia-zine ring adopts a distorted half-chair conformation. The enolic H atom is involved in an intra-molecular O-H⋯O hydrogen bond, forming a six-membered ring. In the crystal, mol-ecules arrange themselves into centrosymmetric dimers by means of pairs of weak inter-molecular N-H⋯O hydrogen bonds.

Methyl 4-acet-oxy-2-methyl-2H-1,2-benzothia-zine-3-carboxyl-ate 1,1-dioxide.

In the title compound, C(13)H(13)NO(6)S, the thia-zine ring adopts a distorted half-chair conformation. Each mol-ecule is linked to its neighbour through inter-molecular C-H⋯O hydrogen bonds.

1-(4-Hydr-oxy-2-methyl-1,1-dioxo-2H-1,2-benzothia-zin-3-yl)ethanone.

In the title compound, C(11)H(11)NO(4)S, the thia-zine ring adopts a distorted half-chair conformation. The enolic H atom is involved in an intra-molecular O-H⋯O hydrogen bond, forming a six-membered ring. Mol-ecules are linked through weak inter-molecular C-H⋯O hydrogen bonds, resulting in chains lying along the b axis.

Methyl 2-acetonyl-4-hydr-oxy-2H-1,2-benzothia-zine-3-carboxyl-ate 1,1-dioxide.

In the mol-ecule of the title compound, C(13)H(13)NO(6)S, the thia-zine ring adopts a distorted sofa conformation. The enolic H atom is involved in intra-molecular O-H⋯O hydrogen bonding besides the weaker C-H⋯O=S and C-H⋯O=C inter-actions.