Dimethylformamide → 2-chloro-4-fluoro-5-[4-formyl-1-methyl-5-(trifluoromethyl)-1H-pyrazol-3-yl]benzoic acid

Participants

Reaction Conditions

Reaction Steps

To a mechanically stirred solution of 10 g of 5-[4-bromo-1-methyl-5-(trifluoromethyl)-1H-pyrazol-3-yl]-2-chloro-4-fluorobenzoic acid in 400 ml of anhydrous tetrahydrofuran under a nitrogen atmosphere was added 1.0 g of 95% sodium hydride. After the foaming subsided, the reaction was stirred and heated to 60° C. for one hour to ensure complete anion formation of the acid. The reaction was cooled to -110° C. with vigorous stirring and a 10.8 mL of 2.5M n-butyl lithium in hexanes was added maintaining the temperature below -100° C. As soon as the addition of n-butyl lithium was completed, 10 mL of dimethyl formamide was added and the solution was allowed to warm to -20° C. The reaction was then quenched with 3N HCl, and most of the volatiles were removed from the reaction mixture. The precipitate was filtered and recrystalized from carbon tetrachloride to give 3.0 g of 2-chloro-4-fluoro-5-[4-formyl-1-methyl-5-(trifluoromethyl)-1H-pyrazol-3-yl]benzoic acid: mp 163° C.; 1HNMR (CDCl3) ppm: 9.82 (s, 1H), 7.89 (d, 1H, J=7.6), 7.07 (d, 1H, J=9.2), 3.39 (s, 3H). 19FNMR (CDCl3) ppm: -57.78, -107.41.

Provenance & Evidence