[Cl:1][C:2]1[C:3]([C:8]([F:11])([F:10])[F:9])=[N:4][NH:5][C:6]=1[CH3:7].Br[CH2:13][C:14]([O:16]CC)=[O:15].C(=O)([O-])[O-].[K+].[K+]>CN(C=O)C.O>[Cl:1][C:2]1[C:3]([C:8]([F:9])([F:11])[F:10])=[N:4][N:5]([CH2:13][C:14]([OH:16])=[O:15])[C:6]=1[CH3:7]
To a solution of 4-chloro-5-methyl-3-(trifluoromethyl)pyrazole (15 g, 81.3 mmol) in DMF (82 mL) was added ethyl 2-bromoacetate (13.6 g, 81.3 mmol) and potassium carbonate (12.4 g, 89.4 mmol). The mixture was heated at 55° C. for 10 hours with stirring. After cooling to room temperature, the reaction mixture was diluted with water (100 mL) and extracted with ethyl acetate (3×150 mL). The combined organic layers were washed with brine, dried (Na2SO4), filtered, and concentrated in vacuo. The crude residue was purified by flash chromatography (SiO2, 0-30% ethyl acetate in hexanes) to afford the desired product (18.5 g, 68.4 mmol, 84%).
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