Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2000-03-28
2001-10-23
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C560S172000, C562S574000
Reexamination Certificate
active
06307103
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an improved process for the preparation of 1,1,1-trifluoro-2-aminoalkanes which comprises hydrogenating the corresponding oximes.
1,1,1-trifluoro-2-aminoalkanes are useful as intermediates for the preparation of a variety of compounds which are useful as agrochemicals, pharmaceuticals or dyes. In particular, they are key intermediates in the preparation of insecticidal benzamides as disclosed for example by DE 36 11 193 and of fungicidal 7-(1,1,1-trifluoroalk-2-ylamino)-6-(halophenyl)-triazolopyrimidines which are described for example in PCT/US98/05615.
J. B. Dickey et al., Ind. Eng. Chem. 98, 1956, 209-213 disclose a method for the preparation of 1,1,1 -trifluoro-2-aminopropane by the hydrogenation of the corresponding oxime in a rocking autoclave at a pressure of 150 bar (2.000 p.s.i.) in the presence of Raney Nickel using ether as diluent. However, only 30% of the desired product are obtainable according to this method.
Therefore, the method known from the art is not applicable for large scale production, due to its low yields.
SUMMARY OF THE INVENTION
Surprisingly, the 1,1,1-trifluoro-2-aminoalkanes of formula I
wherein
R
1
represents an optionally substituted alkyl group;
can be obtained in high yields by hydrogenation of corresponding oximes of formula II
wherein R
1
has the meaning given above and the winding line indicates that the hydroxy group may be in the (E)- or (Z)-position with respect to the trifluoromethyl group, in the presence of Raney nickel and a diluent;
when the reaction is carried out in a diluent selected from an alkanol, a cyclic ether or an aromatic hydrocarbon.
It is, therefore, an object of the present invention to provide an efficient improved process for the preparation of 1,1,1-trifluoro-2-aminoalkanes of formula I.
Other objects and advantages of the present invention will be apparent to those skilled in the art from the following description and the appended claims.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The invention relates to an improved process for the preparation of the compounds of formula I by the hydrogenation of the oximes of formula II the improvement wherein is that the hyrogenation is carried out in a diluent selected from an alkanol, a cyclic ether or an aromatic hydrocarbon.
In general terms, unless otherwise stated herein, the term alkyl as used herein with respect to a radical or moiety refer to a straight or branched chain radical or moiety. As a rule, such radicals have up to 10, in particular up to 6 carbon atoms. Suitably an alkyl moiety has from 1 to 6 carbon atoms, preferably from 1 to 3 carbon atoms. A particularly preferred alkyl moiety is the methyl group.
Suitable alkanols are straight chained or branched alkanols with up to 6 carbon atoms, preferably 1 to 4 carbon atoms. Most preferred are methanol, ethanol and isopropanol, in particular methanol.
Suitable cyclic ethers are cyclic ethers having 4 to 6 carbon atoms and 1 or 2 non-adjacent oxygen atoms, in particular tetrahydrofuran and dioxane.
Suitable aromatic hydrocarbons are aromatic hydrocarbons having 6 to 9 carbon atoms, in particular benzene, toluene or xylene.
A preferred embodiment of the present invention is a process wherein:
1 part of the oxime of formula II is diluted with 5 to 15 parts, preferably 7.5 to 12.5 parts, in particular 8 to 10 parts of methanol, tetrahydrofuran or toluene;
Raney nickel is used in moist form, in particular moisturized with methanol,
the mixture consisting of the oxime of formula II, the diluent and Raney nickel is kept under a hydrogen atmosphere at temperatures between 50° C. and 150° C., preferably between 75° C. and 120° C., in particular between 80° C. and 110° C.; most preferred at about 90° C.
the mixture consisting of the oxime of formula II, the diluent and Raney nickel is kept under a hydrogen atmosphere for 1 to 5 hours, preferably 2 to 4 hours, in particular about 3 hours;
the hydrogenation is carried out at a pressure of 25 to 100 bar, preferably 30 to 80 bar, in particular 35 to 70 bar most preferred at a pressure of about 50 bar;
the reaction mixture obtained form the hydrogenation is filtered and the resulting filtrate is acidified with a mineral acid, preferably hydrochloric acid, to obtain the corresponding 1,1,1-trifluoro-alk-2-yl ammonium salt;
the 1,1,1-trifluoro-alk-2-yl ammonium salt is separated and treated with a base, preferably with an alkali hydroxide, in particular sodium hydroxide to obtain the compound of formula I;
R
1
represents a C
1-4
alkyl group being optionally substituted by one or more halogen atoms or an alkoxycarbonyl or hydroxycarbonyl group, in particular wherein R
1
represents a methyl group.
The compound of formula II is preferably 1,1,1-trifluoropropanone oxime or ethyl 1,1,1-trifluoroacetylacetate oxime, which can be prepared by a condensation reaction between commercially available 1,1,1-trifluoropropanone or ethyl 1,1,1-trifluoroacetylacetate and hydroxylamine. This reaction is preferably carried out in the presence of a dehydration agent such as molecular sieves, TiCl
4
or sodium acetate as disclosed for example by J. B. Dickey et al., loc. cit.
The crude product obtained can be purified according to standard methods for example by distillation or chromatographic methods.
However, the crude product obtained according to the process of this invention is as a rule pure enough to be used as intermediate without further purification.
In a particularly preferred embodiment of the process according to this invention a mixture of the oxime of formula I (3 parts), the diluent, preferably methanol (25 to 35 parts) and Raney nickel (preferably moisturized with methanol; 1 to 1.5 parts) is hydrogenated in an autoclave at a pressure of about 50 bar and a temperature of about 90° C. until the hydrogen uptake ceases. The reaction mixture is cooled, filtered and treated with a mineral acid, in particular hydrochloric acid, and evaporated. The residue is treated with sodium hydroxide and the obtained amine of formula I is distilled.
REFERENCES:
patent: 3737462 (1973-06-01), Cheema et al.
patent: 3959379 (1976-05-01), Ottiger
patent: 4840969 (1989-06-01), Tarnow et al.
patent: 5082862 (1992-01-01), Tarnow et al.
patent: 5593996 (1997-01-01), Pees et al.
patent: 3611193 (1987-10-01), None
patent: WO 98/46608 (1998-10-01), None
J.B. Dickey et al., “Fluorinated Aminoanthraquinone Dyes”, Ind. Eng. Chem. 48, 1956, 209-213.
Gutheil Dieter
Niedermann Hans-Peter
American Cyanamid Company
Costello Charles F.
Davis Brian J.
Richter Johann
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