3-(Acetylsulfanyl)propanoyl chloride → (+/-)-1-[3-(Acetylthio)-1-oxopropyl]-3-(2-furanyl)-4,5-dihydro-1H-pyrazole-5-carboxylic acid

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Reaction Steps

(±)-3-(2-Furanyl)-4,5-dihydro-1H-pyrazole-5-carboxylic acid (4.5 g) is dissolved in 200 cc of water containing 1.38 g of sodium carbonate (pH 9.4) at 10° C. 3-(Acetylthio)propionyl chloride (4.15 g) and 20% sodium carbonate solution are added simultaneously maintaining the pH between 8.5 and 9.4 and the temperature at 10° C. The final reaction mixture (pH 9.7) is stirred at room temperature for 2 hours and extracted with ethyl acetate (discarded) and the aqueous layer made strongly acid with 20% HCl. A precipitate forms which is extracted into ethyl acetate immediately. The solvent is dried and removed to yield 4.5 g of crystalline material which cannot be recrystallized.

Provenance & Evidence