(2Z,3Z)-3,4-Dihydro-2H-1,4-benzothiazine-2,3-dione dioxime dihydrate

In the molecule of the title compound, C8H11N3O4S, the thiazine ring adopts an envelope conformation. In the crystal structure, intermolecular N—H⋯O, O—H⋯O and O—H⋯N hydrogen bonds link the molecules.


Comment
We have been interested in the synthesis and chemical behavior of vic-dioximes, in the past decade. In our investigations, the reaction of amines with dichloroglyoxime or cyanogendi-N-oxide resulted in various symmetrically substituted diaminoglyoxime derivatives, in which some of them were quite suitable to act, as donor species, towards some transition metal ions (Kakanejadifard, Niknam et al., 2007;Kakanejadifard, Saniei et al., 2007;Kakanejadifard & Niknam, 2006;Kakanejadifard & Amani, 2008). Some oximes are widely used for various purposes in organic, inorganic, bioinorganic, pigment, analytical, dyes and medical chemistry (Jones et al., 1961;Schrauzer & Kohnle, 1964;Yari et al., 2006;Hashemi et al., 2006;Ghiasvand et al., 2004;Ghiasvand et al., 2005;Kakanejadifard, Niknam & Zabardasti, 2007). vic-Dioximes, containing mildly acidic hydroxyl groups and slightly basic nitrogen atoms, are amphoteric and their transition metal complexes have been widely investigated as analytical reagents (Gok & Kantekin, 1997), and models for biological systems such as vitamin B 12 (Hughes, 1981). We report herein the synthesis and crystal structure of the title compound.
In the molecule of the title compound ( Fig. 1), the bond lengths and angles are within normal ranges. Ring A (S1/N4/C2/ C3/C5/C6) adopts envelope conformation, with C2 atom displaced by 0.248 (3) Å from the plane of the other ring atoms.
In the crystal structure, intermolecular N-H···O, O-H···O and O-H···N hydrogen bonds (Table 1) link the molecules ( Fig. 2), in which they may be effective in the stabilization of the structure.

Experimental
For the preparation of the title compound, a solution of NaHCO 3 (0.05 g, 0.6 mmol) in aqueous EtOH (10 ml) was added to a magnetically stirred solution of dicholoroglyoxime (1.57 g, 10 mmol) in aqueous EtOH (15 ml) and a solution of 2-aminothiophenole (1.25 g, 10 mmol) in EtOH (15 ml) at room temperature. The solution was stirred for 4 h and then the mixture was filtered. The filtrate was placed at room temperature for 24 h. The gray precipitate was removed by filtration and precipitate was washed with cold THF. It was recrystallized from 2-propanol in one week (yield; 0.31 g, 74.2%, m.p. 492 K).  Fig. 1. The molecular structure of the title molecule, with the atom-numbering scheme. Displacement ellipsoids are drawn at the 50% probability level.
Orthorhombic, Pbca Mo Kα radiation λ = 0.71073 Å Hall symbol: -P 2ac 2ab Cell parameters from 910 reflections a = 9.1636 (18)  as large as those based on F, and R-factors based on ALL data will be even larger.