To a solution of tert-butyl 4-(5-chloro-2-(trifluoromethyl)phenyl)piperidine-1-carboxylate (0.302 g, 0.830 mmol) in dichloromethane (5 mL) was added HCl solution (2 M in ether, 5 mL). The mixture was stirred for 4 h and evaporated to afford a solid that was dissolved in DMF (8 mL). In a separate flask, to a solution of ethyl 6-bromo-[1,2,4]triazolo[4,3-a]pyridine-3-carboxylate (0.224 g, 0.830 mmol) in THF (5 mL) was added a solution of lithium hydroxide hydrate (0.035 g, 0.830 mmol) in water (2 mL). The mixture was stirred for 20 min, acidified with 2 N HCl to PH 6 and evaporated to dryness. To this residue were added benzotriazole-1-yl-oxytris(dimethylamino)phosphonium hexafluorophosphate (0.550 g, 1.25 mmol), N,N-diisopropylethylamine (0.646 g, 5.00 mmol), and the DMF solution obtained from the first reaction. The mixture was stirred at ambient temperature for 16 h and poured into water. The mixture was extracted with ethyl acetate and the organic layer was washed with brine for three times, dried over Na2SO4, filtered, and concentrated under reduced pressure. The resulting residue was chromatographed over silica gel (0-60% EtOAc in hexanes) to give (6-bromo-[1,2,4]triazolo[4,3-a]pyridin-3-yl)(4-(5-chloro-2-(trifluoromethyl)phenyl)piperidin-1-yl)methanone as a solid (0.205 g, 50%): 1H NMR (300 MHz, CDCl3) δ9.38 (m, 1H), 7.79 (dd, J=9.6, 0.9 Hz, 1H), 7.60 (d, J=8.5 Hz, 1H), 7.50 (dd, J=9.6, 1.7 Hz, 1H), 7.42 (d, J=1.4 Hz, 1H), 7.31 (dd, J=8.5, 1.3 Hz, 1H), 5.76-5.71 (m, 1H), 5.01-4.95 (m, 1H), 3.38-3.26 (m, 2H), 3.02-2.92 (m, 1H), 2.01-1.82 (m, 4H); MS (ESI+) m/z 489 [M+H]+.
