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

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.

1. additionthe addition
2. temperatureThe mixture was cooled in a cold water bath
3. waitAfter 15 minutes
4. stirringwas stirred for 2 hours
5. customThe volatiles were removed under reduced pressure
6. customto yield an oil
7. extractionThe mixture was extracted with dichloromethane (3×50 mL)
8. washThe combined organic layers were washed with brine
9. dry with materialdried over sodium sulfate
10. filtrationfiltered
11. concentrationconcentrated under reduced pressure
12. customThe orange oil was purified by flash chromatography (silica gel, elution with 20% ethyl acetate in hexanes)

ORD record

ord-b8890a3add4c452783797298c8107d4a

Source dataset

uspto-grants-2011_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US07879849B2