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0 °C

A −78° C. solution of 3-[4-(3-fluoro-5-methoxy-phenoxy)-2-methyl-phenyl]-propionic acid ethyl ester (0.715 g, 2.15 mmol) in dry CH2Cl2 (10 mL) is treated with a 1 M CH2Cl2 solution of boron tribromide (6.5 mL, 6.5 mmol). The mixture is warmed to 0° C. and stirred for 1 hour under N2. Upon completion, the mixture is poured into ice water and extracted with Et2O. The organic layer is dried (Na2SO4), and the solvent is removed in vacuo to afford crude product that is absorbed on silica gel and purified by flash chromatography using a gradient of 5/1 to 1/1 to hexanes/ethyl acetate to afford 0.558 g (81%) of the title compound. Rf=0.36 (2/1 hexanes/EtOAc). 1H NMR (400 MHz, CDCl3). MS (ES−) m/z mass calculated for C18H19O4F 318, found 317 (M−1, 100%).

1. extractionextracted with Et2O
2. dry with materialThe organic layer is dried (Na2SO4)
3. customthe solvent is removed in vacuo
4. customto afford crude product that
5. customis absorbed on silica gel
6. custompurified by flash chromatography