Hydrogen Peroxide → 5-Chloro-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxylic acid

Participants

Reaction Conditions

Reaction Steps

In a 500 mL flask, 6.0 g (31 mmol) of 5-chloro-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbaldehyde are added to 30 mL of toluene. A solution of 2.4 g (62 mmol) of sodium hydroxide in 6 ml of water is added to the reaction mixture, followed by 103 mL of a 30% solution of hydrogen peroxide in water, whilst keeping the temperature below 37° C. After the end of the addition, the reaction mixture is stirred at 50° C. for 7 hours. Once the reaction mixture is back to room temperature, the two phases are separated and the organic phase is extracted with 100 mL of water. The combined aqueous phases are acidified to pH 2 with aqueous hydrochloric acid. The resulting white precipitate is filtered, washed twice with 20 mL of water, and dried to yield 3.2 g of 5-chloro-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carboxylic acid as a white solid. 1H NMR (400 MHz, DMSO-d6) δ ppm: 3.78 (s, 3H); 7.12 (t, 1H, JHF=53.60 Hz); 13.19 (s, 1H); IR (KBr): 1688 cm−1 (C═O); 2200-3200 cm−1 broad (hydrogen bond).

Provenance & Evidence