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

The title compound, C13H13BrO3S, was prepared by alkaline hydrolysis of ethyl 2-(5-bromo-3-isopropylsulfanyl-1-benzofuran-2-yl)acetate. In the crystal, the carboxyl groups are involved in intermolecular O—H⋯O hydrogen bonds, which link the molecules into dimers. These dimers are further packed into stacks along the c axis by intermolecular C—H⋯π interactions, and by slipped π–π interactions between the furan rings of adjacent molecules [centroid–centroid distance = 3.472 (2) Å, interplanar distance = 3.398 (2) Å and slippage = 0.713 (2) Å].

Cg2 is the centroid of the C2-C7 ring.
In the title molecule ( Fig. 1), the benzofuran unit is essentially planar, with a mean deviation of 0.007 (1) Å from the least-squares plane defined by the nine constituent atoms. In the crystal structure, the carboxyl groups are involved in intermolecular O-H···O hydrogen bonds (Table 1, first entry & Fig. 2), which link the molecules into centrosymmetric dimers. These dimers are further packed into stacks along the c axis by an intermolecular C-H···π interaction between a methylene H atom and the benzene ring (Table 1, second entry & Fig. 2), and by a weak slipped π-π interaction between the furan rings of adjacent molecules, with a Cg1···Cg1 ii distance of 3.742 (2) Å and an interplanar distance of 3.398 (2) Å resulting in a slippage of 0.713 (2) Å ( Fig. 2, Cg1 is the centroid of the C1-C2-C7-O1-C8 furan ring, (ii) -x+1, -y+1, -z.).

Experimental
Ethyl 2-(5-bromo-3-isopropylsulfanyl-1-benzofuran-2-yl)acetate (428 mg, 1.2 mmol) was added to a solution of potassium hydroxide (337 mg. 6 mmol) in water (10 ml) and methanol (10 ml), and the mixture was refluxed for 5 h, then cooled. Water (10 ml) 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 at reduced pressure. The residue was purified by column chromatography (ethyl acetate) to afford the title compound as a colorless solid [yield 86%, m.p. 432-433 K; R f = 0.51 (ethyl acetate)]. 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
H atoms in the hydroxy group were found in a different Fourier map and refined freely. The other H atoms were positioned geometrically and refined using a riding model, with C-H = 0.93 Å fo the aryl, 0.98 Å for the methine, 0.97 Å for the methylene, and 0.96 Å for the methyl H atoms. U iso (H) =1.2U eq (C) for the aryl, methine, and methylene H atoms, and 1.5U eq (C) for the 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. 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.