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US 6,444,828 B1Granted
Method for preparing 1-alkyl-pyrazol-5-carboxylic acid esters III
AssigneeBayer Aktiengesellschaft
InventorsNikolaus Müller, Michael Matzke
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Abstract
1-Alkyl-pyrazole-5-carboxylic esters are obtained with surprisingly low proportions of 1-alkyl-pyrazole-3-carboxylic esters if a 2,4-diketo ester and/or an enolate thereof is reacted with an alkylhydrazine and/or a corresponding alkylhydrazinium salt, if appropriate, in the presence of a solvent and/or of water, in such a manner that during at least about 90% of the reaction free alkylhydrazine is present.
Claims10
A process for preparing 1-alkyl-pyrazole-5-carboxylic esters of the formula
- in which
- R1 and R4 independently of one another each represent straight-chain or branched, optionally halogen-substituted C1-C6-alkyl, optionally halogen-substituted C3-C7-cycloalkyl or optionally substituted C7-C12-aralkyl and
- R2 and R3 independently of one another each represent hydrogen, straight-chain or branched, optionally halogen-substituted C1-C6-alkyl, C3-C7-cycloalkyl or optionally substituted C7-C12-aralkyl,
- wherein a 2,4-diketo ester of the formula
- in which
- R2, R3 and R4 are each as defined in formula (I),
- and/or an enolate thereof is reacted with an alkylhydrazine of the formula
- R1—NH—NH2 (III),
- in which
- R1 is as defined in formula (I),
- and/or a corresponding alkylhydrazinium salt,
- if appropriate in the presence of a solvent and/or of water, in such a manner that during at least 90% of the reaction free alkylhydrazine of the formula (III) is present.
9 more elements
Dependencies are inferred from the claim text.