Patent EA-005077-B1 (EA)
Title: Process for preparing 4-trifluoromethylsulphinylpyrazole derivative
Inventor: CLAVEL JEAN-LOUIS
IPC: G01G11/14
Filed: 1999-10-22
Abstract: 1. A process for the preparation of a compound of formula (I): wherein W represents nitrogen or -CR<3>; R<1> represents halogen, haloC1-6alkyl, haloC1-6alkoxy, R<4>S(O)n-, or -SF5; R<2> represents hydrogen or halogen; R<3> represents halogen; R<4> represents C1-6alkyl or haloC1-6alkyl; and n represents 0, 1 or 2; which process comprises oxidising a compound of formula (II): wherein R<1>, R<2> and W are as defined above, with trifluoroperacetic acid in the presence of a corrosion inhibiting compound. 2. A process according to claim 1 in which the trifluoroperacetic acid is generated in situ by the reaction of trifluoroacetic acid and hydrogen peroxide. 3. A process according to claim 1 or 2 in which the amount of corrosion inhibiting compound used is about 0.08-0.2 molar equivalents. 4. A process according to any one of the preceding claims in which the amount of trifluoroacetic acid employed is from 14-15 molar equivalents. 5. A process according to any one of the preceding claims in which the amount of hydrogen peroxide used in the reaction is from 1.3-1.5 equivalents. 6. A process according to any one of the preceding claims in which the reaction is performed at a temperature of from 10 to 15 degree C. 7. A process according to any one of the preceding claims which further comprises adding chlorobenzene to the reaction mixture on completion of the oxidation reaction, and recovering the trifluoroacetic acid by distillation. 8. A process according to claim 1 in which a compound of formula (II) is prepared by adding sulphur dioxide to a mixture comprising a disulphide of formula (III): wherein R<1>, R<2> and W are as defined in claim 1, a formate salt, trifluoromethyl bromide and a polar solvent. 9. A process according to claim 9 in which the solvent is N, N-dimethylformamide. 10. A process according to claim 8 or 9 in which the reaction temperature during the addition of the sulphur dioxide is from 35 to 55 degree C. 11. A process according to claim 8, 9 or 10 in which the sulphur dioxide is added over a 0.5-2 hour period. 12. A process according to any one of claims 8 to 11 in which the molar ratio of trifluoromethyl bromide: disulphide of formula (III) is from 3: 1 to 5: 1. 13. A process according to any one of claims 8 to 12 in which the amount of sulphur dioxide used is from 1.2-1.5 molar equivalents, relative to the disulphide of formula (III). 14. A process according to any one of claims 8 to 13 in which the amount of formate salt used relative to the disulphide of formula (III) is from 4-6 molar equivalents. 15. A process according to claim 8 in which disulphide of formula (III) wherein W represents nitrogen or -CR<3>; R<1> represents halogen, haloC1-6alkyl, haloC1-6alkoxy, R<4>S(O)n-, or -SF5; R<2> represents hydrogen or halogen; is prepared by adding sulphur monochloride (S2Cl2) to a solution, in an organic solvent, of a compound of formula (IV): wherein R<1>, R<2> and W are as defined in claim 1. 16. A process according to claim 15 in which the solvent is selected from toluene, dichloromethane or dichloroethane, or aliphatic or aromatic nitriles such as acetonitrile, propionitrile, methylglutaronitrile and benzonitrile; or mixtures thereof, optionally as a mixture with chlorobenzene. 17. A process according to claim 15 or 16 in which the solvent is acetonitrile. 18. A process according to claim 15, 16 or 17 in which the sulphur monochloride is from 99.4-99.9% w/w pure. 19. A process according to any one of claims 15 to 18 in which, when acetonitrile is employed as solvent, the content of water is < 1000 ppm, the content of ethanol is < 1500 ppm and the content of ammonia is < 100 ppm. 20. A process according to any one of claims 15 to 19 in which the time for the sulphur monochloride addition is 1-10 minutes. 21. A process according to any one of claims 15 to 20 in which the reaction temperature of the mixture at the start of the addition of the sulphur monochloride is from 5 to 25 degree C. 22. A process according to any one of claims 15 to 21 which further comprises purifying the disulphide of formula (III) by: a) heating the reaction mixture containing the disulphide under reduced pressure to remove hydrogen chloride; b) heating the resulting degassed reaction mixture at atmospheric pressure, followed by cooling to about 30 degree C; c) adjusting the pH of the reaction mixture to 6.5-7 by addition of a weak base; and d) cooling the mixture to a temperature of about 5 degree C and isolating the desired disulphide by filtration. 23. A process for the preparation of a compound of formula (I): wherein W represents nitrogen or -CR<3>; R<1> represents halogen, haloC1-6alkyl, haloC1-6alkoxy, R<4>S(O)n-, or -SF5; R<2> represents hydrogen or halogen; R<3> represents halogen; R<4> represents C1-6alkyl or haloC1-6alkyl; and n represents 0, 1 or 2; which process comprises: (a) adding sulphur monochloride(S2Cl2) to a solution, in an organic solvent, of a compound of formula (IV): wherein R<1>, R<2> and W are as defined above, to produce a disulphide of formula (III): wherein R<1>, R<2> and W are as defined above; (b) adding sulphur dioxide to a mixture comprising the said disulphide of formula (III), a formate salt, trifluoromethyl bromide and a polar solvent, to produce a compound of formula (II) wherein R<1>, R<2> and W are as defined above; and (c) oxidising the said compound of formula (II) with trifluoroperacetic acid in the presence of a corrosion inhibiting compound. 24. A process according to any one of claims 1 to 7 or 23 in which the compound of formula (I) is: 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylsulphinylpyrazole. 25. A process according to any one of claims 7 to 14 or 23 in which the compound of formula (II) is: 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-cyano-4-trifluoromethylthiopyrazole. 26. A process according to any one of claims 15 to 23 in which the compound of formula (III) is: 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-3-cyanopyrazol-4-yl disulphide. 27. A process according to any one of the preceding claims in which: R<1> represents trifluoromethyl, trifluoromethoxy or -SF5; W represents -CR<3>; and R<2> and R<3> represent chlorine.