Water → 1-Phenyl-3-(trifluoromethyl)-1H-pyrazole-5-carboxylic acid

Temperature

95 °C

A sample of crude 1-phenyl-3-(trifluoromethyl)-5-methylpyrazole (˜89%, 50.0 g, 0.221 mole) was mixed with water (400 mL) and cetyltrimethylammonium chloride (4.00 g, 0.011 mole). The mixture was heated to 95° C. Potassium permanganate was added in 10 equal portions, spaced at ˜8 minute intervals. The reaction mass was maintained at 95-100° C. during this period. After the last portion was added, the mixture was held for ˜15 minutes at 95-100° C., whereupon the purple, permanganate color had been discharged. The reaction mass was filtered while hot (˜75° C.) through a 1 cm thick bed of Celite® on a 150 ml, coarse, glass frit. The filter cake was washed with warm (˜50° C.) water (3×100 mL). The combined filtrate and washings were extracted with ether (2×100 mL) to remove a small amount of yellow, water-insoluble material. The aqueous layer was purged with nitrogen to remove residual ether. The clear, colorless alkaline solution was acidified by adding concentrated hydrochloric acid dropwise until the pH reached ˜1.3 (28 g, 0.28 mole). Gas evolution was vigorous during the first two-thirds of the addition. The product was collected via filtration, washed with water (3×40 mL), then dried overnight at 55° C. in vacuo. The product consisted of 11.7 g of a white, crystalline powder, which was essentially pure based upon 1H NMR.

1. temperatureThe reaction mass was maintained at 95-100° C. during this period
2. additionAfter the last portion was added
3. waitthe mixture was held for ˜15 minutes at 95-100° C.
4. filtrationThe reaction mass was filtered while hot (˜75° C.) through a 1 cm thick bed of Celite® on a 150 ml
5. washThe filter cake was washed
6. temperaturewith warm (˜50° C.) water (3×100 mL)
7. extractionThe combined filtrate and washings were extracted with ether (2×100 mL)
8. customto remove a small amount of yellow, water-insoluble material
9. customThe aqueous layer was purged with nitrogen
10. customto remove residual ether
11. additionby adding concentrated hydrochloric acid dropwise until the pH
12. additionGas evolution was vigorous during the first two-thirds of the addition
13. filtrationThe product was collected via filtration
14. washwashed with water (3×40 mL)
15. customdried overnight at 55° C. in vacuo

ORD record

ord-0f6a0aa31de24a30828db719f4a7fe92

Source dataset

uspto-grants-2006_02

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US06995178B2