Regioselective production of 1-alkyl-5-pyrazolecarboxylate esters comprises reacting a 2,4-diketo ester with an alkylhydrazine in the presence of free alkylhydrazine, useful as intermediates for vasoactive and/or spasmolytic agents

摘要

Production of 1-alkyl-5-pyrazolecarboxylate esters (I) comprises reacting a 2,4-diketo ester (II) with an alkylhydrazine (III) or a corresponding alkylhydrazinium salt, optionally in the presence of a solvent and/or water, under conditions such that free (III) is present throughout at least 90% of the reaction. Production of 1-alkyl-5-pyrazolecarboxylate esters of formula (I) comprises reacting a 2,4-diketo ester of formula (II) with an alkylhydrazine of formula (III) or a corresponding alkylhydrazinium salt, optionally in the presence of a solvent and/or water, under conditions such that free (III) is present throughout at least 90% of the reaction: R1, R4 = optionally halogenated 1-6C alkyl, optionally halogenated 3-7C cycloalkyl or optionally substituted 7-12C aralkyl; R2, R3 = H, 1-6C alkyl, 3-7C cycloalkyl or optionally substituted 7-12C aralkyl.