Preparing 5-fluoro-1-alkyl-3-fluoroalkyl-1H-pyrazole-4-carbonyl chlorides
View Patent ↗The present invention relates to a novel process for preparing 5-fluoro-1-alkyl-3-fluoroalkyl-1H-pyrazole-4-carbonyl chlorides, a useful intermediate in the manufacture of fungicides.
1. A process for preparing a compound of formula (I)
where R 1 represents C 1 -C 6 -alkyl and R 2 represents C 1 -C 5 -fluoroalkyl that is optionally bromo- or chloro- substituted, wherein said process comprises reacting a compound of formula (II)
where R 1 and R 2 are as defined above,
with a fluorinating agent of formula (III)
M + F − (III)
where M + represents Li + , Na + , K + , Cs + , Alk 4 N + and Alk represents C 1 -C 4 -alkyl,
and optionally in the presence of a phase transfer catalyst to give a compound of formula (IV)
where R 1 and R 2 are as defined above, and further reacting a compound of formula (IV) with a chlorinating agent to give a compound of formula (I).
2. The process according to claim 1 , wherein R 1 represents methyl, ethyl, n-propyl, isopropyl, butyl, pentyl and R 2 represents CF 2 H, CF 3 , CF 2 Cl, CCl 2 F, C 2 F 5 , or C 3 F 7 .
3. The process according to claim 1 , wherein R 1 represents methyl and R 2 represents CF 2 H or CF 3 .
4. The process according to claim 1 , wherein the compound of formula II is 5-chloro-1-methyl-3-difluoromethyl-1H-pyrazole-4-carbaldehyde.
5. The process according to claim 1 , wherein the compound of formula (II) is reacted with the compound of formula (III) in the presence of a phase transfer catalyst.