Dimethylformamide → 5-Chloro-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbaldehyde

Participants

Reaction Steps

To a solution of 137.5 g (929 mmol) of 3-(difluoromethyl)-1-methyl-1H-pyrazol-5-ol in 136 ml (1858 mmol) of dimethylformamide and 750 ml of toluene was added dropwise with cooling 571 g (3716 mmol) of phosphoryl chloride. The mixture was heated for 3 hours under reflux and allowed to cool, and the reaction mixture wash carefully poured into 41 of ice water. The product was extracted three times, each time with 1500 ml of ethyl acetate, and the combined organic phases were washed twice with saturated sodium bicarbonate solution and finally with saturated sodium chloride solution, dried over sodium sulphate and concentrated. 138 g (with a purity of >99% (GC)) of 5-chloro-3-(difluoromethyl)-1-methyl-1H-pyrazole-4-carbaldehyde (II-1) in the form of a yellow-brown solid was obtained, which was used without further purification in the next reaction step.

Provenance & Evidence