4-Hy­droxy-2-methyl-1,1-dioxo-2H-1λ⁶,2- benzothia­zine-3-carb­oxy­lic acid hemihydrate

In the title compound, C₁₀H₉NO₅S·0.5H₂O, two geometrically different organic mol­ecules are present. The benzene rings and the carboxyl­ate groups are oriented at dihedral angles of 13.44 (4) and 21.15 (18)°. In both mol­ecules, an intra­molecular O—H...O hydrogen bond generates an S(6) ring. In the crystal, both moleucles form inversion dimers linked by pairs of O—H...O hydrogen bonds to generate R₂²(8) loops. The dimers are consolidated into chains extending along [100] by bridging O—H...O hydrogen bonds from the water mol­ecule. A weak C—H...O hydrogen bond also occurs.

2,3-Dihydro-1λ⁶,2-benzothia­zine-1,1,4-trione

In the title compound, C₈H₇NO₃S, the benzene ring is oriented at a dihedral angle of 69.25 (7)° to the S and O atoms of the sulfonyl group. The heterocyclic ring approximates to an envelope, with the N atom in the flap position. In the crystal, mol­ecules are linked by N—H...O_c (c = carbon­yl) hydrogen bonds, forming C(5) chains along [001]. Two R₂²(10) loops arise from pairs of C—H...O hydrogen bonds and a weak aromatic π–π stacking inter­action [centroid–centorid separation = 3.8404 (11) Å] also occurs.

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.

N-Benzyl-4-hy­droxy-2-methyl-1,1-dioxo-2H-1λ⁶,2-benzothia­zine-3-carboxamide

In the title mol­ecule, C₁₇H₁₆N₂O₄S, the heterocyclic thia­zine ring adopts a half-chair conformation, with the S and N atoms displaced by 0.546 (4) and 0.281 (4) Å, respectively, on opposite sides of the mean plane formed by the remaining ring atoms. The mol­ecular structure is stabilized by an intra­molecular O—H...O hydrogen bond. The two aromatic rings are inclined to one another by 42.32 (11)°. In the crystal, mol­ecules are linked by pairs of N—H...O hydrogen bonds, forming inversion dimers. The dimers are linked via a series of C—H...O inter­actions, leading to the formation of a three-dimensional network.