5-Cyclopentyl-3-methylsulfinyl-2-phenyl-1-benzofuran

In the title compound, C20H20O2S, the cyclopentyl ring adopts an envelope conformation with the flap atom connected to the benzofuran residue. The phenyl ring makes a dihedral angle of 32.36 (9)° with the mean plane of the benzofuran fragment. In the crystal, molecules are linked through weak C—H⋯O interactions. In the cyclopentyl ring, two adjacent C atoms are disordered over two sets of sites with site occupancy factors of 0.675 (8) and 0.325 (8).

In the title compound, C 20 H 20 O 2 S, the cyclopentyl ring adopts an envelope conformation with the flap atom connected to the benzofuran residue. The phenyl ring makes a dihedral angle of 32.36 (9) with the mean plane of the benzofuran fragment. In the crystal, molecules are linked through weak C-HÁ Á ÁO interactions. In the cyclopentyl ring, two adjacent C atoms are disordered over two sets of sites with site occupancy factors of 0.675 (8) and 0.325 (8).
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: TK2730).

Comment
Many compounds having a benzofuran skeleton have attracted much attention due to their pharmacological properties such as antifungal, antimicrobial, antitumor and antiviral activities (Aslam et al., 2006;Galal et al., 2009;Khan et al., 2005).
These compounds occur in a wide range of natural products (Akgul & Anil, 2003;Soekamto et al., 2003). As part of our ongoing program investigating the substituent effect on the solid state structures of 2-aryl-5-cyclohexyl-3-methylsulfinyl-1-benzofuran analogues (Choi et al., 2011a, b), we report herein on the crystal structure of the title compound.
In the title molecule ( Fig. 1), the benzofuran unit is essentially planar, with a mean deviation of 0.012 (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, two C atoms (C9 & C10) are disordered over two positions with site-occupancy factors, from refinement of 0.675 (8) (part A) and 0.325 (8) (part B). The phenyl ring makes a dihedral angle of 32.36 (9)° with the mean plane of the benzofuran ring. The crystal packing is stabilized by a weak intermolecular C-H···O hydrogen bond between a phenyl-H atom and the oxygen of the S═O unit (Table 1; C19-H19···O2 i ).

Experimental
77% 3-Chloroperoxybenzoic acid (269 mg, 1.2 mmol) was added in small portions to a stirred solution of 5-cyclopentyl-3-methylsulfanyl-2-phenyl-1-benzofuran (339 mg, 1.1 mmol) in dichloromethane (30 mL) at 273 K. After being stirred at room temperature for 3 h, 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 73%, M.pt. 415-416 K; R f = 0.61 (hexane-ethyl acetate, 2:1 v/v)]. Single crystals suitable for X-ray diffraction were prepared by slow evaporation of an acetone solution of the title compound held at room temperature.

Refinement
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, 0.99 Å for methylene and 0.98 Å for methyl H atoms, respectively. U iso (H) =1.2U eq (C) for aryl-, methine-and methylene-H, and 1.5U eq (C) for methyl-H atoms. Two C atoms of the cyclopentyl ring are disordered over two positions with site occupancy factors, from refinement, of 0.675 (8) (part A) and 0.325 (8) (part B). The distance of equivalent C-C pairs was restrained to 0.001 Å using command DFIX and SADI, and displacement ellipsoids of C9 and C10 set were restrained to 0.01 using commend ISOR.

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.