5-Amino-3,4-dimethylisoxazole → N-(3,4-dimethyl-5-isoxazolyl)-2-(carbomethoxy)thiophene-3-sulfonamide

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Reaction Steps

2-Methoxycarbonylthiophene-3-sulfonyl chloride (2.50 g, 10.05 mmol) was added to a solution of 5-amino-3,4-dimethylisoxazole(0.98 g, 8.75 mmol) in dry pyridine (5.0 ml). The reaction mixture was stirred at room temperature for 16 h. Pyridine was removed under reduced pressure and the residue was partitioned between water and dichloromethane. The organic layer was washed with 1 N HCl (2×50 ml) and dried over anhydrous magnesium sulfate. Evaporation of the solvents left an oily residue, which, after purification by column chromatography over silica gel (1:1 hexanes/ethyl acetate as eluent), yielded 2.20 mg (65%) of a brown solid. Further purification was achieved by recrystallization from ethyl acetate/hexanes, giving the pure product as a white solid, m.p. 113-116° C.

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