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This reaction was conducted in accordance with the procedure described by H. B. Hass and M. L. Bender in J. Am. Chem. Soc., 71, 1767 (1949). Sodium (1.6 grams, 0.07 mole) was dissolved in 50 ml of absolute ethanol. Subsequently, 2-nitropropane (8.1 grams, 0.09 mole) and 5-(bromomethyl)-1-tert-butyl-1H-pyrazole-4-carboxylic acid, ethyl ester (20 grams, 0.07 mole) were added. The resulting reaction mixture was refluxed for two hours, then cooled and the solvent removed in vacuo. The residue was taken up in ether, washed with water, washed with 1N sodium hydroxide, washed with saturated brine, and dried using sodium sulfate and filter paper. The solvent was removed in vacuo and the residue was distilled at 110° C. at 1.6 mm mercury pressure, yielding 11 grams of the 5-formyl-1-tert-butyl-1H-pyrazole-4-carboxylic acid, ethyl ester.

1. customThe resulting reaction mixture
2. temperaturewas refluxed for two hours
3. temperaturecooled
4. customthe solvent removed in vacuo
5. washwashed with water
6. washwashed with 1N sodium hydroxide
7. washwashed with saturated brine
8. customdried
9. filtrationfilter paper
10. customThe solvent was removed in vacuo
11. distillationthe residue was distilled at 110° C. at 1.6 mm mercury pressure