HOBt (163 mg, 1.2 mmol) and DIEA (373 mg, 2.9 mmol) were added to a stirred solution of 5-fluoro-2-trifluoromethyl-benzoic acid (200 mg, 0.9 mmol) in DMF (1.0 mL) and the resulting mixture was cooled to 10° C. EDCI.HCl (231 mg, 1.2 mmol) followed by piperazine-1-carboxylic acid tert-butyl ester (197 mg, 1.0 mmol) were then added and the mixture was stirred at room temperature overnight. The reaction mixture was diluted with water and the product extracted with ethyl acetate. The ethyl acetate layer was washed with brine solution, dried over Na2SO4 and concentrated under reduced pressure to afford the crude residue, which was purified by column chromatography using silica gel 60-120 mesh (30% ethyl acetate in hexane) to afford 301 mg (83%) of 4-(5-fluoro-2-trifluoromethyl-benzoyl)-piperazine-1-carboxylic acid tert-butyl ester, LCMS purity: 99.5%.
