Triethylamine → 3-Amino-5-fluorobenzotrifluoride

Beteiligte Stoffe

Reaktionsschritte

2-Bromo-5-fluoro-1-nitro-3-trifluoromethyl-benzene (XVIII) (55.5 g) is dissolved in 500 mL of ethanol. Triethylamine (19.63 g) and palladium on charcoal (6 g, Pd/C 10%, Engelhard 4505) are added and the mixture is subjected to hydrogenation at 20-25° C. After 20 hours reaction time, the consumption of hydrogen had ceased. The hydrogen pressure is released and the solution is separated from the catalyst by filtration on Cellflock. The filter residue comprising the catalyst is washed with ethanol (2×100 mL). The filtrate and wash fractions are combined and the solution thus obtained is concentrated at 45° C. under reduced pressure to a final volume of ca. 400 mL. Toluene (400 mL) is added and the resulting solution is concentrated to a final volume of ca. 250 mL to obtain a suspension. The precipitate is removed by filtration and the filter cake is washed with toluene (2×100 mL). The solution is concentrated again to a final volume of 200 mL and the formed precipitate is removed again by filtration. The filter cake is washed with toluene (3×50 mL). The process of dilution with toluene, concentration and filtration is repeated until no substantial precipitation occurred in the toluene solution. Finally, the solvent is evaporated at 45-50° C. under reduced pressure and the residue is dried in vacuo at 45° C. to obtain 3-fluoro-5-trifluoromethyl-phenylamine as a yellow oil. GC-MS: m/z: 179, 160, 151, 140, 132. The product is identical in GC and HPLC to a sample of 3-amino-5-fluoro-benzotrifluoride, purchased from ABCR (ABCR F01075). Also the NMR spectra are identical to the sample purchased from ABCR.

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