Chlorosulfonic acid → 1,5-Dimethyl-3-(trifluoromethyl)-1H-pyrazole-4-sulfonyl chloride

Participants

Reaction Steps

To 53 mls of chlorosulfonic acid at 10 C. was added dropwise over fifteen minutes 1,5-dimethyl-3-(trifluoromethyl)pyrazole (24.0 grams). No significant exotherm resulted and after 15 minutes the cooling bath was removed and the reaction was heated to 110 C. for three hours. After standing overnight, the reaction was heated to 110 C. for an additional four hours and allowed to cool to 50 C. Then 19.0 g of thionyl chloride was dropwise over fifteen minutes. The reaction was then heated to 80 C. for twenty minutes and 110 C. for one hour. After cooling, the reaction was cautiously added to 600 g of ice. The aqueous phase was extracted with two 250 ml portions of ether. The combined organic extracts were dried with MgSO4 and concentrated under reduced pressure to yield 7.8 g of the desired product as a tan oil.

Provenance & Evidence