Crystal structure of N-[3-(2-chlorobenzoyl)-5-ethylthiophen-2-yl]-2-[(E)-(2-hydroxybenzylidene)amino]acetamide

In the title compound, C22H19ClN2O3S, the dihedral angle between the mean planes of the thiophene ring and the chlorophenyl and hydroxyphenyl rings are 70.1 (1) and 40.2 (4)°, respectively. The benzene rings are twisted with respect to each other by 88.9 (3)°. The imine bond lies in an E conformation. Intramolecular O—H⋯N and N—H⋯O hydrogen bonds each generate S(6) ring motifs. In the crystal, weak C—H⋯O interactions link the molecules, forming chains along the c axis and zigzag chains along the b axis, generating sheets lying parallel to (100).


S1. Comment
Thiophene derivatives have been reported to exhibit a broad spectrum of biological properties such as anti-inflammatory, analgesic, anti-depressant, anti-microbial and anti-convulsant activities (Molvi et al., 2007;Rai et al., 2008). 2-Aminothiophene derivatives have been used in a number of applications in pesticides, dyes and pharmaceuticals. Reviews on the synthesis and properties of these compounds have been reported (Puterová et al., 2010). Substituted 2-aminothiophenes are active as allosteric enhancers at the human A1 adenosine receptor (Cannito et al.,1990;Nikolakopoulos et al., 2006).
Schiff base compounds are an important class of compounds both synthetically and biologically. These compounds show biological properties including anti-bacterial, anti-fungal, anti-cancer and herbicidal activities (Desai et al., 2001;Singh & Dash, 1988). Furthermore, Schiff bases are utilized as starting materials in the synthesis of compounds of industrial (Aydogan et al., 2001) and biological interest such as β-lactams (Taggi et al., 2002). The crystal and molecular structure of the reactant 2-aminothiophene has been previously reported by our group (Fun et al., 2012). In view of the importance of 2-aminothiphenes and Schiff bases, we report herein the crystal structure of the Schiff base of the previously reported 2-aminothiophene, the title compound, C 22 H 19 ClN 2 O 3 S, (I).
In (I), the dihedral angle between the mean planes of the thiophene ring and the chlorophenyl and hydroxyphenyl rings is 70.1 (1)° and 40.2 (4)°, respectively (Fig. 1). The two phenyl rings are twisted with respect to each other by 88.9 (3)°.

S2. Experimental
To a solution of 2-amino-N-[3-(2-chloro-benzoyl)-5-ethyl-thiophen-2-yl]-acetamide (200 mg, 0.62 mmol) in 10 ml of methanol an equimolar amount of salicylaldehyde (76 mg, 0.62 mmol) was added dropwise with constant stirring. The mixture was refluxed for 4 hours producing a pale yellow precipitate. The reaction completion was confirmed by thin layer chromatography. The precipitate was filtered and dried at room temperature overnight. The solid was recrystallized using dichloromethane and the crystals were used as such for X-ray diffraction studies.

S3. Refinement
All of the H atoms were placed in their calculated positions and then refined using the riding model with atom-H lengths of 0.93Å (CH); 0.97Å (CH 2 ); 0.96Å (CH 3 ); 0.82Å (OH) or 0.86Å (NH). Isotropic displacement parameters for these atoms were set to 1.2 (CH, CH 2 , NH) or 1.5 (CH 3 , OH) times U eq of the parent atom. Idealised Me and OH were   Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds involving l.s. planes.