Methanol → 3,3,3-Trifluoro-2-oxopropanoic acid

To a solution of ethyl 3,3,3-trifluoro-2-oxopropanoate (5 g, 29.36 mmol) in ethanol (30 ml) was slowly added aqueous sodium hydroxide ((2.35 g, 58.72 mmol, dissolved in water (30 ml)), and stirred for 20 h at room temperature until the starting material was consumed. The reaction mixture was concentrated and the resulting white solid was dissolved in water (100 ml). The aqueous layer was extracted by ethyl acetate (50 ml×2), and then the aqueous layer was adjusted PH to 1˜2 with concentrated HCl, and concentrated to give a white solid. The solid was added to methanol (200 ml) and stirred for overnight, filtered, and the filtrate was concentrated and dried to give the crude product (4.13 g, 99%) as a white solid, used in next step without further purification.