5-Ethyl-3-(4-Fluorophenylsulfonyl)-2-methyl-1-benzofuran

In the title molecule, C17H15FO3S, the 4-fluorophenyl ring makes a dihedral angle of 74.06 (4)° with the mean plane of the benzofuran fragment. In the crystal structure, molecules are linked by weak intermolecular C—H⋯O and C—H⋯π interactions. The crystal structure also exhibits aromatic π–π interactions between the benzene rings of adjacent molecules [centroid–centroid distance = 3.629 (2) Å].

In the title molecule ( Fig. 1) the benzofuran unit is essentially planar, with a mean deviation of 0.009 (1) Å from the least-squares plane defined by the nine constituent atoms. The 4-fluorophenyl ring makes a dihedral angle of 74.06 (4)°w ith the mean plane of the benzofuran fragment.
The crystal packing (Fig. 2) is stabilized by a weak intermolecular C-H···O hydrogen bond between the 4-fluorophenyl H atom and the oxygen of the O═ S═O unit[ C13-H13···O2 i ; see Table 1], and by an intermolecular C-H···π interaction between a methyl H-atom and the benzene ring of a neighbouring molecule [C11-H11C···Cg ii ; see Table 1]. The molecular packing ( Fig. 2) is further stabilized by an aromatic π···π interaction between the benzene rings of neighbouring molecules, with a Cg···Cg iii distance of 3.629 (2) Å (Cg is the centroid of the C2-C7 benzene ring; see Table 1).

Experimental
77% 3-chloroperoxybenzoic acid (381 mg, 1.7 mmol) was added in small portions to a stirred solution of 5-ethyl-3-(4fluorophenylsulfanyl)-2-methyl-1-benzofuran (229 mg, 0.8 mmol) in dichloromethane (40 mL) at 273 K. After being stirred at room temperature for 6h, the mixture was washed with saturated sodium bicarbonate 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, benzene) to afford the title compound as a colorless solid [yield 82%, m.p. 377-378 K; R f = 0.68 (benzene)]. Single crystals, suitable for X-ray diffraction, were prepared by slow evaporation of a solution of the title compound in diisopropyl ether at room temperature.

Refinement
All the H-atoms were positioned geometrically and refined using a riding model: C-H = 0.95 Å for aryl, 0.99 Å for methylene and 0.98 Å for methyl H atoms, with U iso (H) = k × U eq (C), where k = 1.2 for aryl and methylene H-atoms, and 1.5 for methyl H-atoms.
supplementary materials sup-2 Figures Fig. 1. The molecular structure of the title molecule 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.