2-(4-Fluorophenyl)-3-methylsulfinyl-5-phenyl-1-benzofuran

In the title molecule, C21H15FO2S, the O atom and the methyl group of the methylsulfinyl substituent are situated on the opposite sides of the plane through the benzofuran fragment. The benzofuran ring plane makes dihedral angles of 28.63 (6) and 31.55 (5)° with the 4-fluorophenyl and phenyl rings, respectively. Weak C—H⋯F and C—H⋯O hydrogen bonds and intermolecular C—H⋯π interactions are present in the crystal structure. The title crystal was refined as an inversion twin with a 0.39 (7):0.61 (7) domain ratio.

In the title molecule, C 21 H 15 FO 2 S, the O atom and the methyl group of the methylsulfinyl substituent are situated on the opposite sides of the plane through the benzofuran fragment. The benzofuran ring plane makes dihedral angles of 28.63 (6) and 31.55 (5) with the 4-fluorophenyl and phenyl rings, respectively. Weak C-HÁ Á ÁF and C-HÁ Á ÁO hydrogen bonds and intermolecular C-HÁ Á Á interactions are present in the crystal structure. The title crystal was refined as an inversion twin with a 0.39 (7):0.61 (7) domain ratio.

Comment
The compounds with the benzofuran skeleton show significant pharmacological activities such as fungicide (Aslam et al., 2006), antitumor and antiviral (Galal et al., 2009) andantimicrobial (Khan et al., 2005) properties. These compounds are common in Nature (Akgul & Anil, 2003;Soekamto et al., 2003). As a part of our ongoing studies of the effect of the side chain substituents on the solid state structures of 3-alkylsulfanyl-2-(4-fluorophenyl)-5-phenyl-1-benzofuran analogues (Choi et al., 2009(Choi et al., , 2010, we report the title crystal structure. The title molecule is depicted in Fig. 1. The benzofuran ring is essentially planar, with a mean deviation of 0.006 (2) Å from the least-squares plane defined by the nine constituent atoms. In the molecule, the benzofuran plane makes dihedral angles of 28.63 (6) and 31.55 (5)° with the 4-fluorophenyl ring and the phenyl ring, respectively. The molecular packing (Fig. 2) is stabilized by an intermolecular C-H···F hydrogen bond between the methyl H atom and the fluorine (Tab. 1). There are also C-H···O interactions (Tab. 1 and Fig. 2) with geometrical parameters that are on the limit of their acceptance as true weak C-H···O hydrogen bonds (Desiraju & Steiner, 1999). The molecular packing (Fig. 3) is further stabilized by two intermolecular C-H···π-electron ring interactions: The first one between the 4-fluorophenyl H atom and the 5-phenyl ring, and the second one between the 4-fluorophenyl H atom and 4-fluorophenyl ring (Tab. 1).

Experimental
77% 3-chloroperoxybenzoic acid (224 mg, 1.0 mmol) was added in small portions to a stirred solution of 2-(4-fluorophenyl)-3-methylsulfanyl-5-phenyl-1-benzofuran (301 mg, 0.9 mmol) in dichloromethane (30 ml) at 273 K. After having been stirred at room temperature for 4h, the mixture was washed with saturated sodium hydrogencarbonate solution and the organic layer was separated, dried over magnesium sulfate, filtered and concentrated at reduced pressure. The residue was purified by column chromatography (silica gel, hexane-ethyl acetate, 1:1 v/v) to afford the title compound as a colourless solid [yield 80%, m.p. 506-507 K; R f = 0.59 (hexane-ethyl acetate, 1:1 v/v)]. Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of the title compound in chloroform at room temperature. The average crystal size was approximately 1.0 × 1.0 × 0.5 mm. (The measured crystal was cut from the larger one.) The crystals are colourless and soluble in polar solvents.

Refinement
All the H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 Å for the aryl H atoms and 0.96 Å for the methyl H atoms, and with U iso (H) = 1.2U eq (C) for the aryl H atoms and 1.5U eq (C) for the methyl H atoms. 1308 Friedel pairs have been used in the refinement. Fig. 1. The title molecule with the atom numbering scheme. The displacement ellipsoids are drawn at the 50% probability level. The H atoms are depicted as small spheres of arbitrary radius.

Special details
Experimental. The measured sample has been cut from the larger crystal. The crystals, both the grown ones as well as the cut one, have not been examined under the polarization microscope.
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.
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 > 2sigma(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. The diffractions 1 0 0 and 0 0 1 as well as their equivalents have been excluded from the refinement because their respective intensities significantly differed from the calculated ones.