反应详情

Next, 5-bromopyridin-2-ylhydrazine (25.3 g) and ethyl 2-ethoxymethyleneacetoacetate (25.1 g) prepared according to a method described in J. Chem. Soc. Perkin trans. I, 1875 (1988), were added to a mixed solvent of 1N hydrochloric acid aqueous solution (320 ml) and ethanol (370 ml), stirred at reflux temperature for 4.5 hours and the solvent was evaporated in vacuo. Water was added to the residue, the precipitated solid was washed with water and recrystallized from a mixed solvent of ethyl acetate and n-hexane to give 1-(5-bromopyridin-2-yl)-5-methyl-1H-pyrazole-4-carboxylic acid ethyl ester (30.6 g) as a pale yellow solid.

1. temperatureat reflux temperature for 4.5 hours
2. customthe solvent was evaporated in vacuo
3. additionWater was added to the residue
4. washthe precipitated solid was washed with water
5. customrecrystallized from a mixed solvent of ethyl acetate and n-hexane