Hydrazine → ethyl 5-(2-methylpropyl)-1H-pyrazole-3-carboxylate

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Reaction Steps

Anhydrous hydrazine (3.58 g, 112 mmol) was added dropwise over a period of 30 minutes to a solution of ethyl 6-methyl-2,4-dioxoheptanoate, sodium salt (24.8 g, 112 mmol) in acetic acid (160 mL). The reaction was stirred overnight at ambient temperature, and then the solvent was removed under reduced pressure. The residue was dissolved in a mixture of diethyl ether and water, and solid sodium bicarbonate and sodium carbonate were added to adjust the mixture to pH 8. The aqueous layer was extracted twice with diethyl ether; the combined organic fractions were washed with brine, dried over magnesium sulfate, filtered, and concentrated under reduced pressure. The residue was purified by chromatography on a HORIZON HPFC system (FLASH 65I cartridge, eluting with 50:50 ethyl acetate/hexanes) to provide 21.0 g of ethyl 5-(2-methylpropyl)-1H-pyrazole-3-carboxylate as a solid.

Provenance & Evidence