Method for producing 2,2-difluoroethylamine derivatives by imine hydrogenation

1. A process for preparing 2,2-difluoroethylamine derivatives, comprising hydrogenating 2,2-difluoroethylimine derivatives of formula (IV) to a corresponding 2,2-difluoroethylamine derivative of formula (III):

where the A radical in formulae (III) and (IV) is:

pyrid-2-yl or pyrid-4-yl, or pyrid-3-yl which is optionally 6-substituted by fluorine, chlorine, bromine, methyl, trifluoromethyl or trifluoromethoxy, or pyridazin-3-yl which is optionally 6-substituted by chlorine or methyl, or pyrazin-3-yl, or 2-chloropyrazin-5-yl, or 1,3-thiazol-5-yl which is optionally 2-substituted by chlorine or methyl, or is

pyrimidinyl, pyrazolyl, thiophenyl, oxazolyl, isoxazolyl, 1,2,4-oxadiazolyl, isothiazolyl, 1,2,4-triazolyl or 1,2,5-thiadiazolyl, which is optionally substituted by fluorine, chlorine, bromine, cyano, nitro, C 1 -C 4 -alkyl, which is optionally substituted by fluorine and/or chlorine, C 1 -C 3 -alkylthio, which is optionally substituted by fluorine and/or chlorine, or C 1 -C 3 -alkylsulphonyl, which is optionally substituted by fluorine and/or chlorine, or is

in which

X is halogen, alkyl or haloalkyl and

Y is halogen, alkyl, haloalkyl, haloalkoxy, azido or cyano,

and R 1 and R 2 are each independently H or C 1 -C 6 -alkyl.

2. The process according to claim 1 , wherein the hydrogenation is carried out with complex hydrides, non-complex metal or semimetal hydrides, Na/EtOH and/or by catalytic hydrogenation.

3. A process according to claim 1 , wherein the compound of formula (IV) is prepared by reacting

an amine of formula (VI)

with 2,2-difluoroacetaldehyde (VIIa) or a derivative thereof of formula (VIIb), (VIIe), (VIId), (VIIe) or (VIIf)

where R 3 and R 4 are each independently H or C 1 -C 6 -alkyl and n is 0, 1 or 2, with condensation to give a compound of formula (IV).