Dichloromethane → 2-(2-chlorophenyl)-5-trifluoromethyl-2H-pyrazole-3-carboxylic acid ethyl ester

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Into a 500 mL flask was weighed 11.5 g (39.6 mmol) of 2-(2-chlorophenyl)-5-trifluoromethyl-2H-pyrazole-3-carboxylic acid, 8.95 g (46.7 mmol) of EDCI, 530 mg (4.34 mmol) of DMAP, and 200 mL of CH2Cl2. Ethanol (8.6 mL) was then added to the stirred solution which was maintained at room temperature for 3 h. The reaction was then concentrated in vacuo to remove CH2Cl2. The residue was washed into a separatory funnel with ethyl acetate and 1.0 M sodium carbonate. The ethyl acetate was separated, washed with brine, dried (Na2SO4), and concentrated in vacuo. The residue was purified by silica gel flash chromatography (Jones Flashmaster, 2×70 g Silica gel, gradient elution from 100% hexanes to 40% ethyl acetate over 30 minutes). Appropriate fractions were combined and concentrated in vacuo affording 2-(2-chlorophenyl)-5-trifluoromethyl-2H-pyrazole-3-carboxylic acid ethyl ester as a viscous yellow oil, yield: 10.0 g (79.3%); 1H NMR (400 MHz, CDCl3): δ 7.32-7.46 (m, 4H), 7.19 (d, J=6 Hz, 1H), 4.16 (q, J=7 Hz, 2H), 1.13 (t, J=7 Hz, 3H); MS (ES): 319 [M+H]+.

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