(3,4-Dimethoxyphenyl)[2-(thiophen-2-ylcarbonyl)phenyl]methanone

In the title compound, C20H16O4S, the thiophene ring makes dihedral angles of 72.9 (2) and 60.5 (2)°, respectively, with the dimethoxy benzene and phenyl rings. In the crystal, C—H⋯O hydrogen bonds link the molecules into a C(9) chain along the b axis. The S and C atoms of the thiophene ring are disordered over two sets of sites [site occupancies = 0.675 (3) and 0.325 (3)]. A short intermolecular S⋯O contact [3.084 (2) Å] is observed in the crystal structure, which also features C—H⋯π interactions.

In the title compound, C 20 H 16 O 4 S, the thiophene ring makes dihedral angles of 72.9 (2) and 60.5 (2) , respectively, with the dimethoxy benzene and phenyl rings. In the crystal, C-HÁ Á ÁO hydrogen bonds link the molecules into a C(9) chain along the b axis. The S and C atoms of the thiophene ring are disordered over two sets of sites [site occupancies = 0.675 (3) and 0.325 (3)]. A short intermolecular SÁ Á ÁO contact [3.084 (2) Å ] is observed in the crystal structure, which also features C-HÁ Á Á interactions.   Table 1 Hydrogen-bond geometry (Å , ).

Comment
Thiophene derivatives exhibit anti-HIVPR inhibition (Bonini et al., 2005) and antibreast cancer (Brault et al., 2005) activity. In addition, some of the benzo[b]thiophene derivatives show significant antimicrobial and anti-inflammatory activity (Isloora et al., 2010). Thiophene derivates have been viewed as significant compounds for applications in many fields (Xia et al., 2010). Schiff bases are well known ligands in coordination chemistry with a wide range of biological activities (Khan et al., 2009). Against this background, and in order to obtain detailed information on molecular the solid state, an X-ray study of the title compound was carried out.
The atom C3 acts as a donor to the atom O4 of the neighbour molecule at (-x,-1/2 + y, -z). This hydrogen bond is involved in a motif C(9) chain along b axis. Interestingly, a short non-hydrogen intermolecular contact between S1···O2 [3.084 (2) Å] at (1/2 -x,1 -y,-1/2 + z) was observed in the crystal structure. In addition to van der Waals interactions, the crystal packing is stabilized by C-H···π interaction between one of the methyl H atom (H1A) and the centroid (Cg2) of the thiophene ring (Table 1).

Experimental
To a stirred suspension of benzoic (1 g, 3.44 mmol) in dry THF (20 ml) lead tetra acetate (1.5 g, 3.42 mmol) was added and refluxed at 50 °C for half an hour. The reaction mixture was then poured into water (200 ml) and extracted with ethyl acetate (2x20 ml), washed with brine solution and dried (Na 2 SO 4 ). The removal of solvent in vacuo afforded the crude product upon crystallization from methanol furnished the title compound as a color less solid.

Refinement
The S and C atoms of the thiophene ring are disordered over two positions (C18/C18′ and S1/S1′) with refined occupancies of 0.675 (3) and 0.325 (3). Equivalent C-C and C-S distances involving the disordered atoms were restrained to be equal with an effective e.s.d. of 0.01Å. The disordered C atoms were only isotropically refined. All H atoms were fixed geometrically and allowed to ride on their parent C atoms, with C-H distances fixed in the range 0.93-0.97 Å with U iso (H) = 1.5U eq (C) for methyl H 1.2U eq (C) for other H atoms.   The molecular structure showing the major and minor occupied site of the disordered atoms.

Special details
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.