Process for producing aminodiphenylamines

Details Process for producing aminodiphenylamines Process for producing aminodiphenylamines

2001-02-02

2001-11-13

Barts, Samuel (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Amino nitrogen containing

C564S395000, C564S406000

Reexamination Certificate

active

06316673

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a process for producing aminodiphenyl-amines, particularly 4-aminodiphenylamine (4-ADPA), by reacting nitrohalobenzenes with aromatic amines in the presence of a palladium catalyst and a base and subsequently hydrogenating the intermediate product thus obtained.
BACKGROUND OF THE INVENTION
4-aminodiphenylamine (4-ADPA) is an important starting product for the synthesis of antioxidants and stabilizers in the rubber and polymer industry (Kirk-Othmer, Encyclopedia of Chemical Technology, 4
th
Edition, 1992, Vol. 3, page 424-456; Ullmann's Encyclopedia of Industrial Chemistry, 5
th
Edition, Vol. A3, 1985, pages 91-111).
4-ADPA may be produced by various methods. One possible method of producing 4-ADPA is the two-stage reaction of aniline or aniline derivatives with p-nitrochloro-benzene in the presence of an acid acceptor or a neutralizing agent, optionally in the presence of a catalyst. Production by this method is described, for example, in DE-A 3,246,151, DE-A 3,501,698, DE-A 185663, U.S. Pat. Nos. 4,670,595, 4,187,249 and 4,187,248. The first stage is generally performed using copper catalysts, and the second stage is performed with different metal components, e.g. nickel (see for example U.S. Pat. No. 5,840,982). Reactions also of, for example, halogenated nitrobenzenes with amines in the presence of palladium catalysts are described in U.S. Pat. No. 5,576,460 and EP-A 846,676.
The disadvantage of the processes described in the above literature is frequently inadequate selectivity, in particular, during formation of the intermediate product, whereby yield losses occur as a result of more or less complex purification steps, before the 4-aminodiphenylamines may be formed by hydrogenation.
SUMMARY OF THE INVENTION
It was, therefore, desirable to provide a process for producing aminodiphenylamines, which starts from aromatic amines and, through reaction with appropriate nitrohalobenzenes and subsequent hydrogenation of the intermediate product formed, results in the desired aminodiphenylamines having good yield and elevated purity.
Therefore, the present invention provides a process for producing aminodiphenylamines by reacting nitrohalobenzenes with aromatic amines in the presence of a base and palladium catalyst and subsequently hydrogenating the product obtained with hydrogen.
DETAILED DESCRIPTION OF THE INVENTION
The nitrohalobenzenes used are preferably those in which the nitro group is in para-position relative to the halogen residue. Possible halogen residues are: fluorine, chlorine, bromine and iodine, preferably chlorine and bromine. The nitrohalobenzenes may also be substituted by one or more other residues, such as for example C
1
-C
4
alkyl residues. Naturally, the position of the nitro group relative to the halogen residues may also be other than the para-position, e.g. it may be in position 2 or 3.
Nitrohalobenzenes used in the present invention are: 4-nitro-2-methylchlorobenzene, 4-nitro-3-methylchlorobenzene, 4-nitrochloro-benzene, 3-nitrochlorobenzene and 2 nitrochlorobenzene. 4-nitrochloro-benzene is preferred.
Aromatic amines which may be used in the process according to the present invention are those aromatic amines which are known in relation to such a reaction, for example aniline, o-toluidine, m-toluidine, p-toluidine, 4-ethylaniline, 4-butylaniline, 4-isopropylaniline, 3,5-dimethyl-aniline or 2,4-dimethylaniline. Aniline is preferred. Naturally, the aromatic amines may also be used in the form of mixtures, in particular isomer mixtures.
In the process according to the invention, 1 to 10 mol, preferably 1.5 to 6 mol, and most preferably 2 to 4 mol of the aromatic amine, are generally used per mol of nitrohalobenzene.
According to the present invention, palladium catalysts, e.g. palladium/phosphine complexes, or other known palladium compounds or complexes may be used.
Suitable palladium/phosphine complex compounds are those in which the palladium has the valency 0 or II and suitable phosphine ligands are compounds such as triphenylphosphine, tri-o-toluylphosphine, tricyclohexylphosphine, tri-t-butylphosphine, bisdiphenylphosphine ethane, bisdiphenylphosphine propane, bis(diphenylphosphino)butane, bis(dicyclohexylphosphino)ethane, bis(diphenylphosphino)ferrocene, 5,5′-dichloro-6,6′-dimethoxybiphenyl-2,2′-diyl-bisdiphenylphosphine, bis-4,4′-dibenzofuran-3,3′-yl-bisdiphenylphosphine, 1,1′-bis(diphenylphosphino)diphenyl ether or bis(diphenylphosphino)binaphthyl, wherein the stated phenyl residues may be substituted by sulfonic acid residues and/or by one or more C
1
-C
12
alkyl groups or C
3
-C
10
cycloalkyl groups. In addition, polymer-bound phosphines may serve as ligands, e.g. tPP polymer (commercially available). Triphenylphosphine is preferably used as a ligand.
However, other palladium/phosphine complex compounds may also be used for the process according to the present invention, such as for example, nitrogen- or oxygen-containing ligands, such as 1,10-phenanthroline, diphenylethane diamine, [1,1′]-binaphthenyl-2,2′-diol (BINOL) and 1,1′-binaphthenyl-2,2′-dithiol (BINAS), or indeed those with two or more different heteroatoms, such as O, N, S.
Palladium compounds which may serve as catalysts include the following classes of compound, for example: palladium halides, acetates, carbonates, ketonates, nitrates, acetonates or palladacyclene, for example Pd
2
dba
3
, Pd(acac)
2
, Pd(OAc)
2
, PdCl
2
, (CH
3
CN)
2
Pd(NO
2
)Cl. Pd
2
dba
3
, Pd(acac)
2
, Pd(OAc)
2
, PdCl
2
are preferred. In addition, heterogeneous or immobilized palladium catalysts may also be used in the process according to the present invention, i.e. those which are applied to suitable inert supports, for example.
In the case of the palladium/phosphine complexes to be used according to the present invention, the molar ratio of the corresponding ligands to palladium is approximately 40:1 to 1:1, preferably 10:1 to 2:1, most preferably 8:1 to 4:1.
According to the present invention, the palladium catalysts, such as palladium/phosphine complexes and/or the other complexes or compounds which may be used, are generally used in amounts of from 0.0001 mol % to 10 mol %, preferably 0.001 mol % to 5 mol %, relative to the nitrohalobenzenes used.
Bases which may be used in the process according to the present invention are alkali and/or alkaline earth metal carbonates, alkoxides and/or hydroxides, in particular, potassium and/or sodium carbonate, cesium carbonate, sodium methanolate and barium hydroxide. Potassium and/or sodium carbonate are preferably used. The bases may be used in a substoichiometric amount or in an excess of up to ten times the equivalent amount relative to the nitrohalobenzene. The bases are preferably used in a 0.3 to 2 times equivalent amount, relative to nitrohalobenzene.
It is advantageous for the process according to the present invention for the bases used to be pretreated by grinding and/or drying.
In the process according to the invention, grinding may be performed in commercially available mills. Grinding affects a drastic increase in specific surface area, which results in a clear increase in conversion. In many cases, grinding may increase the specific surface area by a factor of 10 to 20.
After grinding, the specific areas of the bases are approx. 0.1 to 10 m
2
/g, preferably 0.2 to 1 m
2
/g (BET).
As a result of the pronounced hygroscopic properties of the bases used in the process according to the present invention, the latter have a tendency towards the more or less marked absorption of atmospheric constituents, such as water or carbon dioxide. From a level of absorption of atmospheric constituents of approx. 30 weight percent, a marked influence on achievable conversion levels may be noted. Therefore, in addition to grinding, drying of the bases is also frequently indicated.
Drying of the bases proceeds, for example, in that they are heated under a reduced pressure of approx. 0.01 to 100 mbar for several hours to temperatures of approx. 50

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