2-(5-Methyl-3-methylsulfinyl-1-benzofuran-2-yl)acetic acid

In the title compound, C12H12O4S, the O atom and the methyl group of the methylsulfinyl substituent are located on opposite sides of the plane of the benzofuran fragment. In the crystal structure, intermolecular C—H⋯O and O—H⋯O hydrogen-bonding interactions are found. The structure also exhibits aromatic π–π interactions between the furan and benzene rings [centroid–centroid distance = 3.841 (5) Å].

In the title compound, C 12 H 12 O 4 S, the O atom and the methyl group of the methylsulfinyl substituent are located on opposite sides of the plane of the benzofuran fragment. In the crystal structure, intermolecular C-HÁ Á ÁO and O-HÁ Á ÁO hydrogen-bonding interactions are found. The structure also exhibits aromaticinteractions between the furan and benzene rings [centroid-centroid distance = 3.841 (5) Å ].
Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: NC2155). properties (Howlett et al., 1999;Twyman & Allsop, 1999) and often occurs as natural products (Akgul & Anil, 2003;von Reuss & König, 2004). As part of our ongoing studies on the synthesis and structure of such compounds the structure of the title compound is reported (Choi et al., 2008a,b).
The benzofuran unit is essentially planar, with a mean deviation of 0.013 (3) Å from the least-squares plane defined by the nine constituent atoms (Fig. 1). In the crystal structure intermolecualr C-H···O and O-H···O hydrogen bonding interactions are found ( Fig. 2 and Table 1). The crystal structure is further stabilized by aromatic π···π interactions between the furan and the benzene rings of adjacent molecules, with a Cg1···Cg2 iii distance of 3.841 (5) Å (Cg1 and Cg2 are the centroids of the C1/C2/C7/O1/C8 furan ring and the C2-C7 benzene ring, respectively (Fig. 2).

Experimental
Ethyl 2-(5-methyl-3-methylsulfinyl-1-benzofuran-2-yl)acetate (303 mg, 1.2 mmol) was added to a solution of potassium hydroxide (337 mg, 6 mmol) in water (15 ml) and methanol (15 ml), and the mixture was refluxed for 5h, then cooled down. 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, dried over magnesium sulfate, filtered and concentrated under vacuum. The residue was purified by column chromatography (ethanol) to afford the title compound as a colorless solid [yield 84%, m.p. 461-462 K; R f = 0.51 (ethanol)]. Single crystals suitable for X-ray diffraction were prepared by evaporation of a solution of the title compound in acetone at room temperature.

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.