Process for preparing 3,5-difluoroaniline

A process for preparing 3,5-difluoroaniline, comprising the following stages:

• (1) reacting 2,4,5-trichloronitrobenzene with an alkali metal fluoride in the presence or absence of a polar aprotic solvent at a temperature in the range of about 100.degree. to about 250.degree. C., and, after filtering off precipitated salt or salts and, if a solvent is present, fractional distillation of the resulting crude solution, or chlorinating 2,4-difluoronitrobenzene, to obtain 5-chloro-2,4-difluoronitrobenzene,
• (2) denitrating with chlorination the resulting 5-chloro-2,4-difluoronitrobenzene to give 1,3-dichloro-4,6-difluorobenzene, said stage 2 being carried out in the absence of a Lewis acid or of another chlorination catalyst, using anhydrous chlorine gas at a temperature in the range of about 80.degree. to 250.degree. C., and
• (3) nitrating the resulting 1,3-dichloro-4,6-difluorobenzene to give 2,6-dichloro-3,5-difluoronitrobenzene, said stage 3 being carried out in oleum with sulfuric acid/nitric acid at a temperature in the range of about 15.degree. to about 80.degree. C., and
• (4) reducing, with elimination of chlorine, the resulting 2,6-dichloro-3,5-difluoronitrobenzene with hydrogen or a hydrogen-supplying compound in the presence of palladium as catalyst and in the presence of an inorganic or organic base at a temperature in the range of about 40.degree. to about 250.degree. C.