5-Bromo-3-cyclopentylsulfinyl-2,7-dimethyl-1-benzofuran

In the title compound, C15H17BrO2S, the cyclopentyl ring adopts an envelope conformation. In the crystal, molecules are linked by weak C—H⋯O hydrogen bonds. A slipped π–π interaction occurs between the furan and benzene rings of adjacent molecules [centroid–centroid distance = 3.892 (3) Å and slippage = 1.786 (3) Å]. The crystal structure also exhibits a weak C—Br⋯π [2.919 (3) Å] interaction.


Comment
Benzofuran derivatives have drawn much interest in view of their valuable biological properties such as antibacterial and antifungal, antitumor and antiviral, and antimicrobial activities (Aslam et al., 2009, Galal et al., 2009, Khan et al., 2005. These benzofuran derivatives occur in a wide range of natural products (Akgul & Anil, 2003;Soekamto et al., 2003). As a part of our continuing study of 5-bromo-2,7-dimethyl-1-benzofuran derivatives containing either 3-cyclohexylsulfinyl (Choi et al., 2011a) or 3-cyclohexylsulfonyl (Choi et al., 2011b) substituents, we report herein the crystal structure of the title compound.
In the title molecule ( Fig. 1), the benzofuran unit is essentially planar, with a mean deviation of 0.020 (1) Å from the least-squares plane defined by the nine constituent atoms. The cyclopentyl ring is in the envelope form. The crystal packing ( Fig. 2) is stabilized by weak intermolecular C-H···O hydrogen bonds (see, Table 1). The crystal packing ( Fig. 3) is further stabilized by a weak intermolecular C-Br···π interaction between the bromine and the benzene ring of an adjacent molecule, with a C4-Br1···Cg2 ii [2.919 (3) Å] (Cg2 is the centroid of the C2-C7 benzene ring). The crystal packing (Fig. 3) also exhibits a weak slipped π···π interaction between the furan and benzene rings of adjacent molecules, with a Cg1···Cg2 i distance of 3.892 (4) Å and an interplanar distance of 3.458 (3) Å resulting in a slippage of 1.786 (3) Å (Cg1 is the centroid of the C1/C2/C7/O1/C8 furan ring).

Experimental
77% 3-chloroperoxybenzoic acid (202 mg, 0.9 mmol) was added in small portions to a stirred solution of 5-bromo-3-cyclopentylsulfanyl-2,7-dimethyl-1-benzofuran (260 mg, 0.8 mmol) in dichloromethane (30 mL) at 273 K. After being stirred at room temperature for 6 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, 1:1 v/v) to afford the title compound as a colorless solid [yield 67%, m.p. 415-416 K; R f = 0.51 (hexane-ethyl acetate, 1:1 v/v)]. 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 = 0.95 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, and 1.5U eq (C) for methyl H atoms.
supplementary materials sup-2 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.

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.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å 2 )
x y z U iso */U eq