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