Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1996-11-25
1999-01-05
Burn, Brian M.
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
560 23, 560 90, 558411, 558416, 564164, C07C20948
Patent
active
058565787
DESCRIPTION:
BRIEF SUMMARY
Process for the preparation of unsaturated amino compounds.
The present invention relates to a novel process for the preparation of aromatic amino compounds which are substituted by at least one group which comprises at least one unsaturated carbon-carbon bond, in the presence of a modified noble metal catalyst, and to novel noble metal catalysts for use in this process.
It is known that nitrated aromatic compounds can be reduced to aromatic amines in the presence of noble metal catalysts. In the case of nitrated aromatic compounds substituted by groups which comprise at least one unsaturated carbon-carbon bond, however, the inadequate selectivity of the catalyst leads to unwanted hydrogenation of the unsaturated carbon-carbon bonds. The separation of these unwanted by-products is either impossible or can only be carried out at considerable expense.
In order to counter this problem it has been proposed, for example in DE-A-2 362 780, to use cobalt sulfide as catalyst. This catalyst has the grave disadvantage that, in the course of hydrogenation, sulfur-containing by-products are formed which reduce the quality of the product and severely limit the reusability of the solvents. In addition, highly volatile sulfur compounds are formed during the reaction, one example being hydrogen sulfide, whose leakage from the reactor, particularly in the case of large-scale industrial syntheses, leads to considerable safety problems.
From JP 82,120,553 it is known to prepare aromatic amines, which may be substituted by groups comprising unsaturated carbon-carbon bonds, by hydrogenating the corresponding nitro compounds in the presence of a palladium catalyst and in the presence of a carboxylic acid, such as dinitrobenzoic acid. Using this process to prepare 2-(3,5-diaminobenzoyloxy)ethyl methacrylate, the yield is only 85.5%, providing little satisfaction especially in the case of large-scale industrial application.
From FR-A-2257332 it is known that a catalytical composition comprising (a) a porous support, (b) platin, (c) mangan, (d) iridium and (e) at least one of the metals of group IV of the periodical classification which is selected from the elements germanium, tin and lead can be used to convert hydrocarbonates and particularly to dehydrogenate and hydrogenate hydrocarbonates.
It has been found that this aim can be achieved advantageously by using specially modified platinum catalysts. Counter to expectations, it has been found that, with these catalysts, nitroaromatic compounds can be reduced selectively to the corresponding amino compounds without at the same time hydrogenating the unsaturated carbon-carbon bond-containing side-chains of the nitroaromatic compound.
In accordance with the present invention it is therefore proposed to prepare aromatic amino compounds which are substituted by at least one group comprising at least one unsaturated carbon-carbon bond, by means of catalytic hydrogenation of corresponding aromatic nitro compounds in the presence of a modified noble metal catalyst, by using as noble metal catalyst platinum which is modified with a metal selected from the group consisting of lead, mercury, bismuth, germanium, cadmium, arsenic, antimony, silver and gold.
Some of the catalysts used in the process according to the invention are novel and others are known. DE-A 2 042 368 and J. Mol. Catal. 71,(1992) 317 describe the preparation and use of platinum catalysts, modified with tin, lead, germanium, aluminium, zinc, bismuth and silver, for the preparation of halogen-substituted aromatic amines.
It has surprisingly been found that, if compounds of iron, ruthenium, cobalt, copper or manganese are used as additional promoters for the lead-, mercury-, bismuth-, germanium-, cadmium-, arsenic-, antimony-, silver- and gold-modified platinum catalysts, the yields in the process according to the invention can be raised further. These catalysts are novel and are a further subject of the present invention.
The promoters can be either added directly to the reaction mixture as salts or deposited as insoluble c
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Chem. Abstr. vol. 97, No. 23, 6 Dec. 1982, No. 197995k.
Coq et al., J. Mol. Catal., 71 (1992), 317-333.
Baumeister Peter
Siegrist Urs
Burn Brian M.
Lopez Gabriel
Norvartis Corporation
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