2-(5-Cyclohexyl-3-isopropylsulfanyl-1-benzofuran-2-yl)acetic acid

In the title compound, C19H24O3S, the cylohexyl ring adopts a chair conformation. In the crystal, molecules are linked via pairs of O—H⋯O hydrogen bonds, forming inversion dimers. These dimers are further stabilized by weak intermolecular C—H⋯π interactions, and by slipped π–π interactions between the furan rings of adjacent molecules [centroid–centroid distance = 3.557 (2) Å, interplanar distance = 3.301 (2) Å and slippage = 1.325 (2) Å].

In the title molecule ( Fig. 1), the benzofuran unit is essentially planar, with a mean deviation of 0.032 (1) Å from the least-squares plane defined by the nine constituent atoms. The cyclohexyl ring has the chair conformation. In the crystal structure, the carboxyl groups are involved in intermolecular O-H···O hydrogen bonds (see,  Table 1; Cg1 is the centroid of the C2-C7 benzene ring). Additionally, the crystal packing (Fig. 2) shows a weak slipped between the furan rings of adjacent molecules, with a Cg2···Cg2 ii distance of 3.557 (2) Å and an interplanar distance of 3.301 (2) Å resulting in a slippage of 1.325 (2) Å (Cg2 is the centroid of the C1/C2/C7/O1/C8 furan ring).

Experimental
Ethyl 2-(5-cyclohexyl-3-isopropylsulfanyl-1-benzofuran-2-yl)acetate (396 mg, 1.1 mmol) was added to a solution of potassium hydroxide (336 mg, 6 mmol) in water (10 ml) and methanol (15 ml), and the mixture was refluxed for 5h, then cooled. Water was added, and the solution was extracted with dichloromethane. The aqueous layer was acidified to pH=1 with concentrated hydrochloric acid and then extracted with chloroform. The organic layer was separated, dried over magnesium sulfate, filtered and concentrated at reduced pressure. The residue was purified by column chromatography (ethyl acetate) to afford the title compound as a colorless solid [yield 84%, m.p. 423-424 K; R f = 0.55 (ethyl acetate)]. 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
H atom in the carboxy group is found in a different Fourier map and refined freely. The other H atoms of C atoms were positioned geometrically and refined using ariding model, with C-H = 0.95 Å for aryl, 1.00 Å for methine, 0.99 Å for methylene and 0.98Å 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 S1 0.77443 (