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) δ 1.36 (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.

Provenance & Evidence