Sodium Hydroxide → 4-[1-(4-Bromo-phenoxyl)-heptyl]-benzoic acid

To a solution of 4-(1-hydroxy-heptyl)-benzoic acid methyl ester (1800 mg, 7.2 mmol) in toluene (72 mL) is added 1,1′-(azodicarbonyl)dipiperidine (ADDP, 2725 mg, 10.8 mmol) at 0° C., followed by the additions of tributylphosphine (2.69 mL, 10.8 mmol) and 4-bromo-phenol (1503 mg, 8.64 mmol). The reaction mixture is warmed up to room temperature and stirred overnight. The mixture is loaded on silica gel, eluted with hexanes with a gradient from 0% of ethyl acetate to 50% of ethyl acetate giving 4-[1-(4-bromo-phenoxyl)-heptyl]-benzoic acid methyl ester. 1900 mg of the ester product is taken into ethanol (5 mL), treated with sodium hydroxide (5N aqueous, 2 mL) for 3 h at room temperature. The mixture is concentrated, diluted with ethyl acetate, acidified with 5 N HCl (2 mL), and extracted with ethyl acetate. The organic layers are dried and concentrated giving 4-[1-(4-bromo-phenoxyl)-heptyl]-benzoic acid (1800 mg).