[2-(Benzylideneamino)-4,5,6,7-tetrahydrobenzo[b]thiophen-3-yl](phenyl)methanone

In the title compound, C22H19NOS, the cyclohexene ring of the tetrahydrobenzothiophenyl ring system adopts a slightly distorted half-chair conformation and is twisted slightly [7.5 (8)° for the major disorder component] from the mean plane of the thiophene ring. The dihedral angles between the mean planes of the thiophene ring and the phenyl rings are 65.7 (3) and 8.3 (4)°. The phenyl rings are twisted with respect to each other by 73.8 (7)°. Disorder was modeled for four C atoms of the cyclohexene ring over two sets of sites with an occupancy ratio of 0.659 (2):0.341 (2). In the crystal, a single weak C—H⋯O interaction links the molecules into [001] chains.

In the title compound, C 22 H 19 NOS, the cyclohexene ring of the tetrahydrobenzothiophenyl ring system adopts a slightly distorted half-chair conformation and is twisted slightly [7.5 (8) for the major disorder component] from the mean plane of the thiophene ring. The dihedral angles between the mean planes of the thiophene ring and the phenyl rings are 65.7 (3) and 8.3 (4) . The phenyl rings are twisted with respect to each other by 73.8 (7) . Disorder was modeled for four C atoms of the cyclohexene ring over two sets of sites with an occupancy ratio of 0.659 (2):0.341 (2). In the crystal, a single weak C-HÁ Á ÁO interaction links the molecules into [001] chains.

Comment
Thiophene derivatives have been reported to exhibit a broad spectrum of biological properties such as anti-inflammatory, analgesic, antidepressant, antimicrobial and anticonvulsant activities (Molvi et al., 2007;Rai et al., 2008;Asthalatha et al. , 2007). 2-Aminothiophene derivatives have been used in a number of applications in pesticides, dyes and pharmaceuticals. A review on the synthesis and properties of these compounds was reported in 1999 by Sabnis et al. and more recently by 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;Lütjens et al., 2005). Schiff base compounds are an important class of compounds both synthetically and biologically. These compounds show biological properties including antibacterial, antifungal, anticancer and herbicidal activities (Desai et al., 2001;Karia & Parsania, 1999;Samadhiya & Halve, 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 b-lactams (Taggi et al., 2002).
The crystal structures and molecular structures of two 2-aminothiphenes have been previously reported by our group (Kubicki et al., 2012). In view of the importance of 2-aminothiphenes and Schiff bases, we report the crystal structure of the Schiff base of the previously reported 2-aminothiophene, C 22 H 19 NOS, (I).
The title compound (I) crystallizes with one independent molecule in the asymmetric unit ( Fig. 1). In the molecule, the cyclohexene moiety of tetrahydrobenzothiophenyl ring adopts a slightly distorted half-chair conformation and is slightly twisted from the mean plane of the thiophene ring by 7.5 (8)° for the major disorder component. The dihedral angle between the mean planes of the thiophene ring and the two phenyl rings is 65.7 (3)° (C10-C15) and 8.3 (4)° (C17-C22), respectively. The two phenyl rings are twisted with respect to each other by 73.8 (7)°. Disorder was modeled for the C4, C5, C6 and C7 carbon atoms of the cyclohexene ring over two sites with occupancy ratios of 0.659 (2):0.341 (2). Bond lengths are within normal ranges (Allen et al., 1987). A single weak intermolecular C18-H···O1 i hydrogen-bonding interaction (Table 1) links the molecules into dimers ( Fig. 2) but no classical hydrogen bonds are present.

Experimental
To a solution of (2-amino-4,5,6,7-tetrahydrobenzo[b]thiophen-3-yl)-phenylmethanone (200 mg, 0.79 mmol) in 10 ml of methanol, an equimolar amount of benzaldehyde (84 mg, 0.79 mmol) was added dropwise with constant stirring. The mixture was refluxed for 4 hours. A yellow precipitate was obtained. The reaction completion was confirmed by thin layer chromatography. The precipitate was filtered and dried at room temperature overnight. The solid was recrystallized from dichloromethane and the crystals were used as such for the X-ray diffraction studies.

Refinement
All of the H atoms were placed in their calculated positions and then refined using the riding model with C-H bond lengths of 0.95 Å (CH) or 0.99 Å (CH 2 ). Isotropic displacement parameters for these atoms were set to 1.2 (CH, CH 2 ) times U eq of the parent atom. Disorder was modeled for the C4, C5, C6 and C7 carbon atoms of the tetrahydrobenzothiophenyl ring over two sites with an occupancy ratio of 0.659 (2):0.341 (2).

Figure 1
An ORTEP drawing of (I) showing the labeling scheme of the molecule with 30% probability displacement ellipsoids.
Disorder is shown modeled for the C4, C5, C6 and C7 carbon atoms of the tetrahydrobenzothiophenyl ring over two sites with an occupancy ratio of 0.659 (2) Special details 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.