5-Cyclopentyl-2-(4-fluorophenyl)-3-methylsulfinyl-1-benzofuran

In the title compound, C20H19FO2S, the cyclopentyl ring adopts an envelope conformation. The 4-fluorophenyl ring makes a dihedral angle of 27.10 (7)° 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 cyclopentyl ring, one C atom is disordered over two orientations with site-occupancy factors of 0.617 (7) and 0.383 (7).

In the title compound, C 20 H 19 FO 2 S, the cyclopentyl ring adopts an envelope conformation. The 4-fluorophenyl ring makes a dihedral angle of 27.10 (7) 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. In the cyclopentyl ring, one C atom is disordered over two orientations with site-occupancy factors of 0.617 (7) and 0.383 (7).

D-HÁ
of the title compound.
The title compound crystallizes ins the non-centrosymmetric space group Fdd2. The crystal studied was an inversion twin with a 0.85 (7) : 0.15 (7) domain ratio.
In the title molecule ( Fig. 1), the benzofuran unit is essentially planar, with a mean deviation of 0.024 (2) Å from the least-squares plane defined by the nine constituent atoms. The cyclopentyl ring is in the envelope form. In the cyclopentyl ring, the C10 atom is disordered over two positions with site-occupancy factors, from refinement of 0.617 (7) (part A) and 0.383 (7) (part B). The dihedral angle formed by the 4-fluorophenyl ring and the mean plane of the benzofuran fragment is 27.10 (7)°. 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; C20-H20B···O2 i ). The crystal packing (Fig. 2) is further stabilized by intermolecular C-H···π interactions between a 4-fluorophenyl H atom and the furan ring (Table 1; C16-H16···Cg i , Cg is the centroid of the C1/C2/C7/O1/C8 furan ring).

Experimental
77% 3-chloroperoxybenzoic acid (224 mg, 1.0 mmol) was added in small portions to a stirred solution of 5-cyclopentyl-2-(4-fluorophenyl)-3-methylsulfanyl-1-benzofuran (293 mg, 0.9 mmol) in dichloromethane (30 mL) at 273 K. After being stirred at room temperature for 4h, 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, 1:2 v/v) to afford the title compound as a colorless solid [yield 72%, m.p. 419-420 K; Rf = 0.67 (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 ethyl acetate at room temperature.

Refinement
The reported Flack parameter was obtained by TWIN/BASF procedure in SHELXL (Sheldrick, 2008). All H atoms were positioned geometrically and refined using a riding model, with C-H = 0.95 Å for aryl, 1.00 Å for methine, and 0.99 Å for methylene and methyl H atoms, respectively. U iso (H) = 1.2U eq (C) for aryl, methine, methylene, and 1.5U eq (C) for methyl H atoms. One of the C atoms of the cyclopentyl ring is disordered over two positions with site occupancy factors, supplementary materials sup-2 from refinement of 0.617 (7) (part A) and 0.383 (7) (part B). The distances of equivalent C9-C10A and C9-C10B, and C11-C10A and C11-C10B pairs were restrained to 1.525 (3) Å, 0.001 Å and 0.001 Å using command DFIX, SADI and DELU respectively, and displacement ellipsoids of C10 set were restrained to 0.01 using command ISOR.

Figures
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 small spheres of arbitrary radius. The C10 atom of the cyclopentyl ring is disordered over two positions with site occupancy factors, from refinement of 0.617 (7 ) (part A) and 0.383 (7) (part B).

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.