3-(3-Fluorophenylsulfinyl)-2,4,6,7-tetramethyl-1-benzofuran

In the title compound, C18H17FO2S, the 3-fluorophenyl ring makes a dihedral angle of 78.30 (5)° with the mean plane of the benzofuran fragment. In the crystal, molecules are linked by weak intermolecular C—H⋯O hydrogen bonds and C—H⋯π interactions.

In the title compound, C 18 H 17 FO 2 S, the 3-fluorophenyl ring makes a dihedral angle of 78.30 (5) with the mean plane of the benzofuran fragment. In the crystal, molecules are linked by weak intermolecular C-HÁ Á ÁO hydrogen bonds and C-HÁ Á Á interactions.

D-HÁ
In the title compound ( Fig. 1), the benzofuran unit is essentially planar, with a mean deviation of 0.016 (1) Å from the least-squares plane defined by the nine constituent atoms. The 3-fluorophenyl ring makes a dihedral angle of 78.30 (5)°w ith the mean plane of the benzofuran fragment. The crystal packing (Fig. 2) is stabilized by weak intermolecular C-H···O hydrogen bonds between a methyl H atom and the O atom of the sulfinyl group (Table 1; C12-H12C···O2 i ). The crystal structure is further stabilized by intermolecular C-H···π interactions between a methyl H atom and the benzene ring (Table   1; C10-H10A···Cg ii , Cg being the centroid of the C2-C7 benzene ring).

Experimental
77% 3-chloroperoxybenzoic acid (269 mg, 1.2 mmol) was added in small portions to a stirred solution of 3-(3-fluorophenylsulfanyl)-2,4,6,7-tetramethyl-1-benzofuran (360 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 at reduced pressure. The residue was purified by column chromatography (hexane-ethyl acetate, 2:1 v/v) to afford the title compound as a colorless solid [yield 79%, m.p. 413-414 K; R f = 0.58 (hexane-ethyl acetate, 2:1 v/v)]. Single crystals suitable for X-ray diffraction were prepared by slow evaporation of a solution of the title compound in acetone at room temperature.

Refinement
All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.95 Å for aryl and 0.98 Å for methyl H atoms (with U iso (H) = 1.2U eq (C) for aryl and 1.5U eq (C) for methyl H atoms).

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.