| 摘要 |
In a process for the preparation of 3,5-difluoroaniline,
(1) 2,4,5-trichloronitrobenzene is reacted with an alkali metal fluoride in the presence or absence of a polar aprotic solvent at temperatures from approximately 100 DEG C to approximately 250 DEG C, the precipitated salts are filtered off, and the crude solution is subjected to fractional distillation,
(2) the resulting 5-chloro-2,4-difluoronitrobenzene is subjected to denitrating chlorination with anhydrous chlorine gas in the absence of a Lewis acid or of another chlorination catalyst at temperatures from approximately 80 to approximately 250 DEG C, to give 1,3-dichloro-4,6-difluorobenzene,
(3) this compound is nitrated in oleum using mixed acid (sulphuric acid/nitric acid) at temperatures from approximately 15 to approximately 80 DEG C to give 2,6-dichloro-3,5-difluoronitrobenzene, and
(4) this compound is reduced with hydrogen in the presence of palladium as catalyst and in the presence of an inorganic or organic base at temperatures from approximately 40 to approximately 250 DEG C.
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