Process for preparing 1-alkyl-3-fluoroalkyl-1H-pyrazole-4-carboxylic acid chlorides

摘要

The present invention relates to a novel method for preparing 1-alkyl-3-fluoroalkyl-1H-pyrazole-4-carbonyl chlorides, a useful precursor for the preparation of fungicides, by means of reductive dehalogenation, starting from N-alkyl-3-haloalkyl-5-halopyrazolecarbaldehyde.

主权项

1. Method for preparing 1-alkyl-3-fluoroalkyl-1H-pyrazole-4-carbonyl chloride of formula (I) where R1 is C1-C6-alkyl and R2 is C1-C5-fluoroalkyl, comprising reacting a 5-halo-1-alkyl-3-fluoroalkyl-1H-pyrazole-4-carbaldehyde of formula (II) where R1 and R2 have the meanings stated above and Hal is Cl, Br or I, by catalytic hydrogenation and with addition of a base to give 1-alkyl-3-fluoroalkyl-1H-pyrazole-4-carbaldehyde of formula (III) where R1 and R2 have the meanings stated above, and then the compound of formula (III) is converted into the acyl chloride of formula (I) by reaction with a chlorinating agent with addition of a free-radical initiator.