Organic compounds -- part of the class 532-570 series – Organic compounds – Nitriles
Patent
1997-10-01
1999-03-02
Burn, Brian M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Nitriles
564253, 564261, 564265, 564417, C07C20938
Patent
active
058773401
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a hydrogenation process for the preparation of aromatic amino compounds which contain, directly on the aryl ring or in a side chain, one or more functional groups which can likewise be hydrogenated or eliminated by hydrogenolysis, such as nitrile groups, imino groups, carbonyl groups or halogen. The preparation takes place by catalytic hydrogenation of the corresponding aromatic nitro compounds in the presence of a modified noble metal catalyst. The invention also relates to the use of modified noble metal catalysts for the hydrogenation of aromatic nitro compounds which are substituted by nitrile, imino or carbonyl groups or by halogen.
It is known that aromatic nitro compounds can be reduced in the presence of noble metal catalysts and hydrogen to give aromatic amines, with very good yields. When other hydrogenatable or hydrogenolytically eliminable functional groups are present at the same time, for example nitrile, imino or carbonyl groups or halogen, particular measures must be taken in order to avoid the formation of unwanted by-products, whose separation from the desired product is often highly complex or, in particularly unfavourable cases, totally impossible. A particular problem is posed by selective reduction when two or more hydrogenatable or hydrogenolytically eliminable functional groups are present in one compound.
The prior art includes a number of proposals for the selective reduction of aromatic nitro compounds substituted by functional groups which can be hydrogenated and/or hydrogenolytically eliminated. All of these proposals have the disadvantage that they are suitable only for particular classes of substituted aromatic nitro compounds, and cannot therefore be employed universally. Moreover, the reaction solutions usually comprise additional components which after the reaction must, in some cases with considerable effort, be separated off and disposed of.
For instance, JP-62 123 162 proposes carrying out hydrogenation with Raney-nickel in the presence of cyanamide or dicyandiamide.
Hungarian Patent Application HU 207 713B describes a process in which 2,3-dichloro-6-nitrobenzonitrile is hydrogenated to the corresponding aniline using a Pd/C catalyst in the presence of concentrated HCI.
In another process, which is described in DE-A-37 03 236, nitrobenzaldoxime O-ethers are reduced directly to the corresponding anilines using Raney nickel.
JO 2009-827-A of 29.3.89 describes the reduction of appropriately substituted nitrobenzyl derivatives to form the corresponding anilines, using Raney nickel in the presence of, for example, melamine derivatives.
Examples of other proposals are the Bechamp reduction of DE-A-2 065 869 or a sulfide reduction, J. Org. Chem. 50, (1985) 5782.
The aim of the present invention is to provide a process, which both economically and ecologically is simple to carry out on the industrial scale, for the hydrogenation of aromatic nitro compounds which are substituted by hydrogenatable or hydrogenolytically eliminable functional groups such as nitrile groups, imino groups, carbonyl groups or halogen.
It has been found that these hydrogenations can be accomplished advantageously if specially modified platinum catalysts are employed. Counter to expectations it has been found that, with these catalysts, aromatic nitro compounds can be reduced selectively to the corresponding amino compounds without at the same time hydrogenating the unsaturated --CN or --CO bonds of the substituents on the aromatic nitro compound.
A further advantage of the process is that it does not give rise to the formation of any Fe muds nor any acidic or sulfur-containing effluents requiring disposal. The product is obtained in high purity and the reaction can be carried out in conventional reactors without the need to use special materials.
The present invention relates to a process for the preparation of substituted aromatic amino compounds containing at least one --CN multiple bond or a carbonyl group on the aromatic radical or in a side chain, by catalytic hydro
REFERENCES:
patent: 3666813 (1972-05-01), Hindin et al.
J. P. Marino, et al., Synthetic Communications, vol. 24, No. 6, 1994, pp. 839-848.
Rylander, P.N., Hydrogenation Methods, Academic Press, London, 1985, pp. 326-329.
Freifelder, M., Practical Catalytic Hydrogenation, Wiley, New York, 1971, p. 256.
Rylander, P.N., Catalytic Hydrogenation in Organic Synthesis, Academic Press, London, 1979, p. 140.
Freifelder, M., Practical Catalytic Hydrogenation, Wiley, New York, 1971, pp. 305-306.
Rylander, P.N., Hydrogenation Methods, Academic Press, London, 1985, p. 77.
Baumeister Peter
Siegrist Urs
Burn Brian M.
Novartis Consumer Health S.A.
Wissing William K.
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