Sulfur Dioxide → 4-Ethoxycarbonyl-1-(2-pyridyl)pyrazole-5-sulfonamide

Beteiligte Stoffe

Reaktionsschritte

14 g of ethyl 5-amino-1-(2-pyridyl)pyrazole-4-carboxylate was dissolved in 50 ml of conc. hydrochloric acid, and the solution obtained was cooled to -5° C., to which 5.5 g of sodium nitrite dissolved in 10 ml of water was added cropwise, and thereafter, stirred for 10 minutes, followed by addition of 0.6 g of urea. The solution thus obtained was added dropwise at 5° C. to a solution obtained by adding 2 g of sulfur dioxide and 0.6 g of cuprous chloride to 50 ml of 1,2-dichloroethane. After stirring at room temperature for 1 hour, 200 ml of ice water was added thereto, followed by extraction with chloroform. Seperation of the layer of chloroform, washing with water, drying and concentration were then carried out to obtain 13.1 g of the title compound. m.p.: 38° to 42° C.

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