Diethyl Oxalate → ethyl 1-butyl-5-[2-(propylthio)ethyl]-1H-pyrazole-3-carboxylate

Participants

Reaction Steps

A neat mixture of 4-(propylthio)butan-2-one (9.00 g, 61.5 mmol) and diethyl oxalate (9.00 g, 61.5 mmol) was added dropwise to a stirred solution of sodium tert-butoxide (5.90 g, 61.5 mmol) in ethanol (44 mL) at ambient temperature. Following the addition, the reaction was stirred for two hours. Acetic acid (35 mL) was added, followed by potassium acetate (7.24 g, 73.8 mmol). The mixture was cooled in a cold water bath. Butylhydrazine (11.0 g, 61.5 mmol) was added in portions. After 15 minutes, the mixture was allowed to warm to ambient temperature and was stirred for 2 hours. The volatiles were removed under reduced pressure to yield an oil. Saturated aqueous sodium carbonate was added to the oil until a pH of 10 was reached. The mixture was extracted with dichloromethane (3×50 mL). The combined organic layers were washed with brine, dried over sodium sulfate, filtered, and concentrated under reduced pressure. The orange oil was purified by flash chromatography (silica gel, elution with 20% ethyl acetate in hexanes) to provide 10.6 g of ethyl 1-butyl-5-[2-(propylthio)ethyl]-1H-pyrazole-3-carboxylate as an orange oil.

Provenance & Evidence