3-Bromo-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine (prepared by standard BOC deprotection of tert-Butyl 3-bromo-5,6-dihydro-1,2,4-triazolo[4,3-a]pyrazine-7(8H)-carboxylate, CAS [723286-80-4], commercially available e.g. from Allichem, Ark Pharm or Bepharm) (0.6 mmol) and diethylaminomethyl polystyrene (0.6 g, 1.92 mmol) were slurried in Dichloromethane (DCM) (7 mL) under argon. 2-Chloro-3-(trifluoromethyl)benzoyl chloride (0.16 g, 0.66 mmol, commercially available e.g. from Apollo Scientific or Shanghai FWD Chemicals) was added to the reaction. The mixture was stirred for 4 hours. The resin was filtered, washed with Dichloromethane (50 mL) and concentrated in vacuo to afford crude product. The crude product was purified by using mass-directed automated (preparative) HPLC (MDAP). The fractions containing the products were evaporated, diluted with diethyl ether and treated with 1 mL of HCl in diethyl ether; the solutions were stirred for 30 min. and solvent evaporated to give 3-bromo-7-{[2-chloro-3-(trifluoromethyl)phenyl]carbonyl}-5,6,7,8-tetrahydro[1,2,4]triazolo[4,3-a]pyrazine (0.268 g). LC/MS [M+H]+=410.9, retention time=2.07 minutes (5 minute method).
