To a solution of [4-(6-aminopyridin-3-yl)piperazin-1-yl]-(2-trifluoromethylphenyl)-methanone (0.035 g, 0.10 mmol) in pyridine (3 mL) was added hexanesulfonyl chloride (0.022 mL, 0.12 mmol). After heating at 60° C. for 20 h, the mixture was diluted with ethyl acetate (100 mL), washed with brine, dried over anhydrous MgSO4 and concentrated in vacuo. Purification by preparative thin layer chromatography afforded the title compound as a white solid (3.8 mg, 8% yield). 1H NMR (300 MHz, CDCl3) δ 7.66, 7.29, 4.08, 3.91, 3.38, 3.27, 3.08, 1.84, 1.35, 1.27, 0.87. MS (ES+) m/z 499.4 (M+1).
