Sodium Hydroxide → 4-(4-Methyl-3-thienyl)-3-(trifluoromethyl)benzoic acid

Sodium hydroxide (5M: 6 mL; 30 mmol; 3 eq.) was added to a solution of methyl 4-(4-methyl-3-thienyl)-3-(trifluoromethyl)benzoate (3 g; 10 mmol; 1 eq.) in EtOH (90 mL) and the reaction mixture was stirred at 60° C. for 2 hours. After evaporation of the solvent, the residue was taken up in water (300 mL) and the aqueous phase was washed with ethyl acetate (2×100 mL) then acidified to pH 2 with conc. HCl. The solution was concentrated to ca. 100 mL and extracted with ethyl acetate. The organic layer was dried over magnesium sulphate and concentrated in vacuo to afford the title compound (2.6 g, 91%) as a brown oil.