[Br:1][C:2]1[NH:6][N:5]=[C:4]([C:7]([F:10])([F:9])[F:8])[CH:3]=1.C([O-])([O-])=O.[Cs+].[Cs+].Br[CH2:18][C:19]([O:21][CH3:22])=[O:20].C(OCC)(=O)C>C(#N)C.O>[Br:1][C:2]1[N:6]([CH2:18][C:19]([O:21][CH3:22])=[O:20])[N:5]=[C:4]([C:7]([F:10])([F:9])[F:8])[CH:3]=1
To a solution of 5-bromo-3-(trifluoromethyl)-1H-pyrazole (1.0 g, 4.6 mmol) and Cs2CO3 (3.0 g, 9.3 mmol) in acetonitrile (10 mL) was added methyl 2-bromoacetate (865 mg, 5.6 mmol). The reaction was heated at 80° C. for 3 h. After the reaction was cooled to room temperature, the mixture was portioned between ethyl acetate and water. The organic layer was separated and washed with saturated aqueous NH4Cl and brine. The organic layer was then dried over Na2SO4, filtered and concentrated to afford crude product which was purified by silica gel chromatography eluting with dichloromethane/hexanes to afford methyl 2-(5-bromo-3-(trifluoromethyl)-1H-pyrazol-1-yl)acetate (420 mg, 32%) as a clear oil. MS (m/z): 287.1 [M+H]+; HPLC retention time 2.93 min (2-98% acetonitrile:water with 0.05% trifluoroacetic acid).
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