Hydrochloric Acid → ethyl 5-amino-3-methyl-1-[5-(trifluoromethyl)pyridin-2-yl]-1H-pyrazole-4-carboxylate

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Reaction Steps

5-(Trifluoromethyl)pyridin-2-ylhydrazine (10.0 g) described in Reference Example 8 and ethyl 2-cyano-3-ethoxy-3-methylacrylate (10.3 g) were added to a mixed solvent of ethanol (40 ml) and 1N hydrochloric acid aqueous solution (40 ml), and the mixture was stirred at reflux temperature for three hours. Water was added to the reaction solution to give ethyl 5-amino-3-methyl-1-[5-(trifluoromethyl)pyridin-2-yl]-1H-pyrazole-4-carboxylate (9.6 g). Next, the compound was added to tetrahydrofuran (50 ml), isoamyl nitrite (20 g) was added and the mixture was stirred at reflux temperature for five hours. The reaction solution was concentrated, a mixed solvent of ethanol (40 ml) and water (40 ml) and sodium hydroxide (5 g) were added and the mixture was stirred at reflux temperature for two hours. Ethanol was evaporated, diluted hydrochloric acid was added and the precipitated solid was recrystallized from aqueous methanol to give the titled compound.

Provenance & Evidence