In a solution of 5-(4-fluorophenyl)-4-(4-pyridinyl)-1H-pyrazole-3-carboxylic acid, monohydrate (0.9905 g, 3.5 mmol) from step 1 and 1-hydroxybenzotriazole hydrate (0.4824 g, 3.57 mmol) in dimethylformamide (20 mL) at 0° C. under N2, 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (0.6983 g, 3.57 mmol) was added. The solution was stirred at 0° C. under N2 for 1 hour, then was added 1-tert.-butoxycarbonylpiperazine (0.6585 g, 3.5 mmol) followed by N-methyl morpholine (0.40 mL, 3.6 mmol). The reaction was stirred from 0° C. to room temperature overnight. The reaction mixture was diluted with ethyl acetate and saturated NaHCO3 solution, extracted. The organic layer was washed with water and brine, and dried over MgSO4. After filtration, the solvent was removed under reduced pressure, and crude product was obtained (1.7595 g). The desired product 1,1-dimethylethyl 4-[[5-(4-fluorophenyl)-4-(4-pyridinyl)-1H-pyrazol-3-yl)carbonyl]-1-piperazinecarboxylate (1.2375 g, 78.4%) was isolated by chromatography (silica gel, 10:90 isopropyl alcohol/toluene). Anal. Calc'd for C24H26N5FO3: C, 63.85; H, 5.80; N, 15.51; Found: C, 63.75; H, 5.71; N, 15.16. MS (MH−): 452 (base peak).
