Ethyl Acetate → 3-(difluoromethyl)-5-fluoro-1-methyl-1H-pyrazole-4-carboxylic acid

Participants

Reaction Steps

A suspension of 79.7 g (350 mmol) of periodic acid in 640 ml of absolute acetonitrile was stirred for 30 min. At 0° C., 56.6 g (318 mmol) of 5-fluoro-1-methyl-3-difluoromethyl-1H-pyrazole-4-carbaldehyde (IV-1) and 1.4 g (6 mmol) of PCC dissolved in 130 ml of dry acetonitrile were added. The reaction mixture was subsequently stirred at room temperature for 2.5 hours. After 1600 ml of ethyl acetate had been added, the reaction mixture was washed in succession with saturated sodium chloride solution/water (1:1), saturated sodium metabisulphite solution and saturated sodium chloride solution. The organic phase was dried over sodium sulphate and concentrated to obtain 51.4 g (83% of theory) of 3-(difluoromethyl)-5-fluoro-1-methyl-1H-pyrazole-4-carboxylic acid (V-1) as a yellow solid.

Provenance & Evidence