Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Patent
1998-05-22
2000-04-25
Geist, Gary
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
564415, C07C20932
Patent
active
060546174
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process for reducing nitro compounds to give the corresponding amines using a homogeneous palladium, ruthenium, nickel or rhodium catalyst.
The reduction of nitro compounds, especially of nitroaromatics, to give the corresponding amines or anilines has been carried out in industry for over a hundred years. While the reduction by means of iron was still employed industrially until a few years ago, the catalytic reduction using noble metal catalysts on various support materials has recently become established in industry. Although this method has many advantages compared to the reduction by means of iron, problems nevertheless frequently occur in practice. Thus, long filtration times are frequently necessary for separating off the catalyst. The catalysts are usually extremely sensitive to traces of catalyst poisons such as sulfur compounds in low oxidation states, which can lead to the reduction stopping completely. Owing to the nature of a heterogeneous catalyst, the search for the fault if the reaction is unsuccessful is often problematical and sometimes only possible with a considerable outlay in terms of apparatus.
If the nitroaromatic contains halogen substituents, dehalogenation frequently occurs as a secondary reaction. This can be suppressed by selective deactivation of the catalyst, but this makes reproducibility more difficult.
Reductions using homogeneous catalysts which are frequently more efficient compared to heterogeneous catalysts are described, for example, in J. Org. Chem. 1976, 41, 1200 and J. Indian Chem. Soc. 1986, 63, 901. Owing to the problems in separating the catalyst from the product, these reactions have hitherto been carried out only on a laboratory scale. Here too, dehalogenation occurs as a secondary reaction in the case of halogenated nitroaromatics.
It is therefore an object of the invention to provide a process which at least reduces the disadvantages mentioned and makes it possible to reduce nitro compounds to amines in a simple manner and in high yields.
It has now been found that the reduction of nitro compounds with hydrogen in an aqueous system using noble metal catalysis can be carried out under mild conditions and in high yields if the reaction is carried out in the presence of a water-soluble ligand.
EP-A-0 372 313 describes the use of noble metal catalysts having tris(m-sulfophenyl)phosphine as complexing ligand. These catalysts are used in hydrocarbonylations and hydroformylations, particularly in the water gas reaction.
It is therefore surprising that the catalysts mentioned are also suitable for the reduction of nitroaromatics to give the corresponding anilines, without, for example, dehalogenation or C'/C linkage with dehalogenation being observed.
Water-soluble catalysts have hitherto enabled nitroaromatics to be reduced to anilines only when using carbon monoxide or formic acid derivatives (Tetrahedron Letters 1995, 36, 9305). Drawbacks for the industrial implementation of these processes are the acute toxicity of carbon monoxide and the relatively high price of the formic acid derivatives.
The invention accordingly provides a process for reducing nitro groups to amino groups, which comprises reacting a nitro compound with hydrogen in the presence of a water-soluble metal catalyst of the formula (I), metal ion or an alkaline earth metal ion;
Nitro compounds are reduced in very high yield and selectivity by means of the process of the invention, and only little dehalogenation occurs in the case of halogenated nitro compounds. The aqueous catalyst solution can be separated off by simple phase separation.
M is preferably rhodium, ruthenium or palladium.
The reaction medium employed is preferably water and the water-soluble catalyst is preferably used in the form of an aqueous solution.
Water-soluble ligands suitable for the process of the invention contain, for example, sulfonate salt groups and/or sulfonic acid groups and/or carboxylate salt groups and/or carboxylic acid groups and/or phosphonate salt groups and/or phosphonic acid group
REFERENCES:
patent: 3504035 (1970-03-01), Polinski
patent: 3944615 (1976-03-01), Iqbal
patent: 4157455 (1979-06-01), Fitton
patent: 4535162 (1985-08-01), Mestroni
patent: 5057618 (1991-10-01), Herrmann et al.
patent: 5087755 (1992-02-01), Nomura
patent: 5155274 (1992-10-01), Herrmann et al.
patent: 5315040 (1994-05-01), Kotohiro
J.F. Knifton, Homogeneous Catalyzed Reduction of Nitro Coumpounds. IV, Selective and Sequential Hydrogenation of Nitroaromatics, J. Org. Chem., vol. 41, No. 7, 1976, pp. 1200-1205.
P. Khandual et al., Dihydrogen Reduction of Nitroaromatics in Presence of Nickel (II) , Palladium (II) , and Platinum (II) Acetylacetonates in Homogeneous Phase, J. Indian Chem, Soc., vol. LXIII, Oct. 1986, pp. 901-906.
A. M. Tafesh et al., First Selective Reduction of Aromatic Nitro Compounds Using Water Soluble Catalysts, Tetrahedron Letters, vol. 36, No. 51, pp. 9305-9308, 1995.
Bahrmann Helmut
Cornils Boy
Dierdorf Andreas
Haber Steffen
Clariant GmbH
Geist Gary
Hanf Scott E.
Vollano Jean F
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