Crystal structure of (5Z)-5-(2-hydroxybenzylidene)-1,3-thiazolidine-2,4-dione

The title compound, C10H7NO3S, crystallizes with four independent molecules in the asymmetric unit with slightly different conformations; the dihedral angles between the six- and five-membered rings are 2.6 (1), 1.09 (9), 8.6 (1) and 6.2 (1)°. In the crystal, molecules are linked by O—H⋯O and N—H⋯O hydrogen bonds, forming sheets lying parallel to (101).


S1. Comment
Thiazolidinones are an important group of heterocyclic compounds. Diverse biological activities such as bactericidal, pesticidal, fungicidal, insecticidal, anticonvulsant, tuberculostatic, antiinflammatory, antithyroidal, potentiation of pentobarbital induced sleeping time, etc., have been found to be associated with thiazolidinone derivatives (Singh et al., 1981;Bondock et al., 2007;Vicini et al., 2008;Behbehani & Ibrahim, 2012). In this context we report here the synthesis and crystal structure determination of the title compound.

S2. Experimental
The title compound was obtained as a major product from a three component reaction of 2-hydroxy-benzaldehyde (1 mmol, 122 mg), thiazolidine-2,4-dione (1 mmol, 117 mg) and 1-aminopropan-2-ol (1 mmol, 75 mg) under reflux. The reaction was monitored by TLC till completion. On cooling the solid product was collected by filteration, dried under vacuum and recrystallized from ethanol to afford yellow crystals in a sufficient quality for X-ray diffraction. M.p. 558 K.

S3. Refinement
H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 Å) while those attached to nitrogen and oxygen were placed in locations derived from a difference map and their coordinates adjusted to give N-H = 0.91 Å and O-H = 0.84 Å. All were included as riding contributions with isotropic displacement parameters 1.2 times those of the attached atoms. Analysis of 852 reflections having I/σ(I) > 13 and chosen from the full data set with CELL_NOW showed the crystal to belong to the triclinic system and to consist of one major component (ca. 88%) and two minor components.
The raw data were processed using the multi-component version of SAINT under control of the two-component orientation file generated by CELL_NOW. Reflections from the major twin domain were used for the refinement.  The asymmetric unit showing labeling scheme and 50% probability ellipsoids.

Special details
Experimental. The diffraction data were obtained from 3 sets of 400 frames, each of width 0.5° in ω, colllected at φ = 0.00, 90.00 and 180.00° and 2 sets of 800 frames, each of width 0.45° in φ, collected at ω = -30.00 and 210.00°. The scan time was 20 sec/frame. Analysis of 852 reflections having I/σ(I) > 13 and chosen from the full data set with CELL_NOW (Sheldrick, 2008) showed the crystal to belong to the triclinic system and to consist of one major and two minor components. The second of the minor components was considered to be small enough compared to the others that it could be neglected in the integration. The raw data were processed using the multi-component version of SAINT under control of the two-component orientation file generated by CELL_NOW. Geometry. All e.s.d.'s (except the e.s.d. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell e.s.d.'s are taken into account individually in the estimation of e.s.d.'s in distances, angles and torsion angles; correlations between e.s.d.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell e.s.d.'s is used for estimating e.s.d.'s involving l.s. planes. 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 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. H-atoms attached to carbon were placed in calculated positions (C-H = 0.95 Å) while those attached to nitrogen and oxygen were placed in locations derived from a difference map and their coordinates adjusted to give N-H = 0.91%A and O-H = 0.84%A. All were included as riding contributions with isotropic displacement parameters 1.2 times those of the attached atoms. Trial refinements after all atoms were included indicated that the single component reflection file extracted from the twinned data set gave superior results.