Dichloromethane → 2-chloro-5-[1,4-dimethyl-5-(trifluoromethyl)-1H-pyrazol-3-yl]-4-fluorobenzoic acid, 1-methylethyl ester

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Reaction Steps

To a solution of 18 g of 2-chloro-5-[1,4-dimethyl-5-(trifluoromethyl)-1H-pyrazol-3-yl]-4-fluorobenzoic acid (Ex. 2) in 400 mL of CH2Cl2 was added 10 g of oxalyl chloride and a few drops of DMF. After 20 minutes at room temperature, the reaction Was heated to reflux for 2 hr and subsequently concd in vacuo. The resultant solid was dissolved in excess 2-propanol and heated overnight at reflux. The reaction mixture was concd, dissolved in ether, washed with 10% aq. NaOH and saturated brine and concd to give a solid. Recrystallization from cold hexanes gave 14 g of 2-chloro-5-[1,4-dimethyl-5-(trifluoromethyl)-1H-pyrazol-3-yl]-4-fluorobenzoic acid, 1-methylethyl ester: mp 72° C.; 1HNMR CDCl3) δ1.36 (d, 6H, 6.4 Hz), 2.09 (quintet, 3H, 2.0 Hz), 5.25 (heptet, 1H, 6.0 Hz), 7.27 (d, 1H, 9.2 Hz), 7.94 (d, 1H, 7.6 Hz). Anal. Calcd for C16H15O2N2F4Cl: C, 50.74; H, 3.99; N, 7.40. Found: C, 50.85; H, 4.02; N, 7.41.

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