5-Fluoro-2-methyl-3-phenylsulfonyl-1-benzofuran

There are two symmetry-independent molecules, A and B, in the asymmetric unit of the title compound, C15H11FO3S. The crystal studied was an inversion twin with a 0.21 (12):0.79 (12) domain ratio. In the crystal structure, the two independent molecules are related by a pseudo-inversion center. The dihedral angles formed by the phenyl ring and the plane of the benzofuran fragment are 80.2 (1)° in molecule A and 80.7 (1)° in molecule B. In the crystal structure, the A and B molecules are linked by aromatic π–π interactions between the furan and benzene rings of neighbouring benzofuran systems; the centroid–centroid distances are 3.671 (7) and 3.715 (7) Å. In addition, the crystal structure also exhibits two weak non-classical intermolecular C—H⋯O hydrogen bonds.

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NG2699).  (Akgul & Anil, 2003;Soekamto et al., 2003) and their biological activity (Aslam et al., 2006;Galal et al., 2009). As a part of our continuing studies of the effect of side chain substituents on the solid state structures of 5-halo-2-methyl-3-phenylsulfonyl-1-benzofuran analogues (Choi et al., 2008a, b, c), we report the crystal structure of the title compound (Fig. 1).
The crystal studied was an inversion twin with a 0.21 (12):0.79 (12) domain ratio. It crystallized in the monoclinic space group P2 1 , with two symmetry-independent molecules, A and B, in the asymmetric unit.
The benzofuran unit is essentially planar, with a mean deviation of 0.011 (4) Å for A molecule and 0.007 (4) Å for B molecule, respectively, from the least-squares plane defined by the nine constituent atoms. In the title compound, the dihedral angles formed by the phenyl ring and the plane of the benzofuran fragment are 80.2 (1)° in molecule A and 80.7 (1)° in molecule B, respectively. In the crystal packing (Fig. 2), the A and B molecules are linked by two different aromatic π-π interactions; the first between the furan ring (Cg1) and an adjacent benzene ring (Cg4) [distance = 3.671 (7) Å], the second between the furan ring (Cg3) and an adjacent benzene ring (Cg2) [distance = 3.715 (7) Å], (Cg1, Cg2, Cg3, and Cg4 are the centroids of the C1/C2/C7/O1/C8 furan ring, the C2-C7 benzene ring, the C16/C17/C22/O4/C23 furan ring, and the C17-C22 benzene ring, respectively). The molecular packing (Fig. 2) is further stabilized by two non-classical intermolecular C-H···O hydrogen bonds; the first between the benzene H atom and the oxygen of the S═O unit, with a C3-H3···O6 i , the second between the phenyl H atom and the oxygen of the S═O unit, with a C26-H26···O2 ii , respectively (Table 1).

Experimental
77% 3-Chloroperoxybenzoic acid (560 mg, 2.5 mmol) was added in small portions to a stirred solution of 5-fluoro-2-methyl-3-phenylsulfanyl-1-benzofuran (310 mg, 1.2 mmol) in dichloromethane (40 mL) at 273 K. After being stirred at room temperature for 5h, the mixture was washed with saturated sodium bicarbonate solution and the organic layer was separated, dried over magnesium sulfate, filtered and concentrated in vacuum. The residue was purified by column chromatography (chloroform) to afford the title compound as a colorless solid [yield 75%, m.p. 397-398 K; R f = 0.55 (chloroform)]. Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of the title compound in benzene at room temperature.

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 Å for aromatic H atoms and 0.96 Å for methyl H atoms, and with U iso (H) = 1.2U eq (C) for aromatic H atoms and 1.5U eq (C) for methyl H atoms. The reported Flack parameter was obtained by TWIN/BASF procedure in SHELXL (Sheldrick, 2008 Fig. 1. The molecular structure of the title compound with the atom numbering scheme. Displacement ellipsoids are drawn at the 50% probability level. H atoms are presented as a small spheres of arbitrary radius.

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.
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.