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

Participants

Reaction Conditions

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