Stannous chloride dihydrate → [2,6-Dichloro-4-(trifluoromethyl)phenyl]hydrazine

Temperature

55 °C

A solution of 125 g (0.543 mole) of 2,6-dichloro-4-trifluoromethylaniline in 662 mL of glacial acetic acid was placed in a flask equipped with a stirrer. This solution was warmed to 55° C., and to it was added a suspension of 43.3 g (0.628 mole) of sodium nitrite in 318 mL of concentrated sulfuric acid. The temperature was maintained at 62°-64° C. during the first half of this addition and then the temperature was maintained at 55°-62° C. during the second half of the addition. The total addition required about 100 minutes. Upon completion of addition, the reaction mixture was allowed to cool to 40° C. and then was cooled rapidly with a bath of dry ice/isopropanol to 0° C. At this temperature a solution of 473 g (2.10 moles) of tin(II) chloride dihydrate in 323 mL of concentrated hydrochloric acid was added dropwise while the temperature was kept between -5° C. and 5° C. This addition required about 50 minutes. After the white slurry was warmed to room temperature, it was filtered, yielding a moist, white solid which was immediately placed in 1.1 L of 30% ammonium hydroxide. This mixture was stirred at room temperature for one hour and then was warmed to 40° C. with stirring. The mixture was cooled to 28° C. before being filtered. The filter cake was triturated seven times with 400 mL of diethyl ether, decanting the ether extract each time. The combined ether extracts were then washed once with water, dried over anhydrous magnesium sulfate, and filtered. The solvent was evaporated under reduced pressure, yielding 103.4 g of 2,6-dichloro-4-trifluoromethylphenylhydrazine as a crystalline product. The nmr spectrum was consistent with the proposed structure.

1. customequipped with a stirrer
2. additionto it was added
3. temperatureThe temperature was maintained at 62°-64° C. during the first half of this addition
4. temperaturethe temperature was maintained at 55°-62° C. during the second half of the addition
5. additionThe total addition required about 100 minutes
6. additionUpon completion of addition
7. temperatureto cool to 40° C.
8. customwas kept between -5° C. and 5° C
9. additionThis addition required about 50 minutes
10. temperatureAfter the white slurry was warmed to room temperature
11. filtrationit was filtered
12. customyielding a moist, white solid which
13. temperaturewas warmed to 40° C.
14. stirringwith stirring
15. temperatureThe mixture was cooled to 28° C.
16. filtrationbefore being filtered
17. customThe filter cake was triturated seven times with 400 mL of diethyl ether
18. customdecanting the ether
19. extractionextract each time
20. washThe combined ether extracts were then washed once with water
21. dry with materialdried over anhydrous magnesium sulfate
22. filtrationfiltered
23. customThe solvent was evaporated under reduced pressure

ORD record

ord-05202b9b4b544c279c00bc01655b8d68

Source dataset

uspto-grants-1993_10

DOI

10.6084/m9.figshare.5104873.v1

Patent number

US05250504