DIPEA (0.084 mL, 0.49 mmol) was added drop wise to 4-benzenesulfinyl-benzoic acid (48 mg, 0.19 mmol) in DMF (4 mL). EDCI (78 mg, 0.41 mmol) and HOBT 26 mg, 0.19 mmol) were added consecutively and 2-amino-1-[4-(2-trifluoromethyl-benzoyl)-piperazin-1-yl]-ethanone in its TFA salt form (70 mg, 0.16 mmol) was added after a further 10 mins. The resulting mixture was allowed to stir at room temperature overnight. Water was then added and the product was extracted with EtOAc and washed with brine. The organic phase was dried over Na2SO4 and concentrated under reduced pressure to afford a crude product. Purification by column chromatography (using silica gel with a mesh size of 60-120 and 100% EtOAc as eluent) afforded 45 mg (51% yield) of 4-benzenesulfinyl-N-{2-oxo-2-[4-(2-trifluoromethyl-benzoyl)-piperazin-1-yl]-ethyl}-benzamide. LC-MS purity: 91.93%. 1H NMR (DMSO-D6): δ 8.7 (t, 1H), 8 (m, 3H), 7.8 (m, 6H), 7.5 (m, 3H), 7.2 (m, 1H), 4.2 (d, 2H), 3.6 (m, 6H), 3.1 (m, 2H).
