Process for preparing 1-alkyl-3-difluoromethyl-5-hydroxypyrazoles
View Patent ↗The present invention relates to a process for preparing 1-alkyl-3-difluoromethyl-5-hydroxypyrazoles, which are valuable intermediates for the production of fungicides.
1. A process for preparing a compound of formula (I)
in which R 1 is a linear or branched C 1 -C 6 -alkyl group, comprising reacting a compound of formula (II)
in which R 2 is a linear or branched C 1 -C 6 -alkyl group,
with a compound of formula (III)
NH 2 —NH—R 1 (III)
in the presence of an organic acid and a solvent.
2. A process according to claim 1 , wherein the organic acid is formic acid, acetic acid, p-toluenesulphonic acid or trifluoroacetic acid.
3. A process according to claim 1 , wherein the compound of formula (II) is methyl difluoroacetoacetate or ethyl difluoroacetoacetate.
4. A process according to claim 1 , wherein the compound of formula (III) is methylhydrazine or ethylhydrazine.
5. A process according to claim 1 , wherein between 0.8 and 1.8 mol of the compound of formula (III) and 0.1 to 1.2 mol of the organic acid are used per mole of the compound of formula (II).
6. A process according to claim 1 , wherein the solvent is selected from the group consisting of dialkyl ethers, tetrahydrofuran, dioxane, dichloromethane, dichloroethane or trichloroethane, acetonitrile, propionitrile, n- or i-butyronitrile, methyl tert-butyl ether, toluene and chlorobenzene.
7. A process according to claim 1 , wherein the solvent is methyl tert-butyl ether.
8. A process according to claim 2 , wherein compound of formula (II) is methyl difluoroacetoacetate or ethyl difluoroacetoacetate.
9. A process according to claim 2 , wherein the compound of formula (III) is methylhydrazine or ethylhydrazine.
10. A process according to claim 3 , wherein the compound of formula (III) is methylhydrazine or ethylhydrazine.
11. A process according to claim 2 , wherein between 0.8 and 1.8 mol of the compound of formula (III) and 0.1 to 1.2 mol of the organic acid are used per mole of the compound of formula (II).
12. A process according to claim 3 , wherein between 0.8 and 1.8 mol of the compound of formula (III) and 0.1 to 1.2 mol of the organic acid are used per mole of the compound of formula (II).
13. A process according to claim 4 , wherein between 0.8 and 1.8 mol of the compound of formula (III) and 0.1 to 1.2 mol of the organic acid are used per mole of the compound of formula (II).
14. A process according to claim 2 , wherein the solvent is selected from the group consisting of dialkyl ethers, tetrahydrofuran, dioxane, dichloromethane, dichloroethane or trichloroethane, acetonitrile, propionitrile, n- or i-butyronitrile, methyl tert-butyl ether, toluene and chlorobenzene.
15. A process according to claim 3 , wherein the solvent is selected from the group consisting of dialkyl ethers, tetrahydrofuran, dioxane, dichloromethane, dichloroethane or trichloroethane, acetonitrile, propionitrile, n- or i-butyronitrile, methyl tert-butyl ether, toluene and chlorobenzene.
16. A process according to claim 4 , wherein the solvent is selected from the group consisting of dialkyl ethers, tetrahydrofuran, dioxane, dichloromethane, dichloroethane or trichloroethane, acetonitrile, propionitrile, n- or i-butyronitrile, methyl tert-butyl ether, toluene and chlorobenzene.
17. A process according to claim 5 , wherein the solvent is selected from the group consisting of dialkyl ethers, tetrahydrofuran, dioxane, dichloromethane, dichloroethane or trichloroethane, acetonitrile, propionitrile, n- or i-butyronitrile, methyl tert-butyl ether, toluene and chlorobenzene.
18. A process according to claim 2 , wherein the solvent is methyl tert-butyl ether.
19. A process according to claim 3 , wherein the solvent is methyl tert-butyl ether.
20. A process according to claim 4 , wherein the solvent is methyl tert-butyl ether.
21. A process according to claim 5 , wherein the solvent is methyl tert-butyl ether.