Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
2000-09-08
2002-03-05
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S445000, C546S192000, C546S214000, C548S343500
Reexamination Certificate
active
06353136
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a novel process for preparing aromatic amines using palladaphosphacyclobutanes.
Aromatic amines, in particular substituted anilines, are of great industrial importance as precursors for dyes, fine chemicals, agrochemicals and intermediates for active compounds.
The preparation of substituted anilines is generally carried out industrially by nitration of a corresponding aromatic and subsequent hydrogenation. Since nitrations take place under drastic reaction conditions, many anilines having a complex substitution pattern can be prepared only with difficulty, if at all, by this route.
Palladium-catalyzed aminations of iodoaromatics, bromoaromatics and chloroaromatics leading to substituted anilines are described in A. S. Guram et al., Angew. Chem. 1995, 107, 1459. These reactions are carried out under comparatively mild reaction conditions and can therefore also be used for the synthesis of anilines having a complex substitution pattern. The iodoaromatics and bromoaromatics used as starting materials are significantly more expensive and less readily available than the chloroaromatics.
DE-A1-196 50 213 discloses a process for the amination of chloroaromatics using trans-di-&mgr;-acetatobis(o-(di-o-tolylphosphino)benzyl)dipalladium, if desired in the presence of halide cocatalysts. In general, 1 mol % of catalyst (corresponding to 2 mol % of Pd) is used.
Particularly in the case of chloroaromatics, large amounts of catalyst, in general from 1 to 5 mol %, are usually added in order to achieve industrially useful conversions. Owing to the complexity of the reaction mixture, simple recycling of the catalyst is not possible, so that the catalyst costs generally stand in the way of industrial implementation.
SUMMARY OF THE INVENTION
There is therefore a great need for a process for preparing aromatic amines which does not have the abovementioned disadvantages, is suitable for industrial implementation and gives aromatic amines in high yield and purity.
This object is surprisingly achieved by the use of particular palladaphosphacyclobutanes as catalysts.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides a process for preparing aromatic amines of the formula (I)
Ar—[NR
6
R
7
]
n
(I)
where
n is 1, 2 or 3,
Ar is unsubstituted or substituted phenyl, furanyl, pyrryl, pyridinyl, naphthyl or quinolinyl, where the substituents are 1, 2, 3, 4, 5 or 6, preferably 1, 2 or 3, in number and are selected from the group consisting of C
1
-C
8
-alkyl, C
3
-C
8
-cycloalkyl, C
1
-C
8
-alkoxy, C
1
-C
8
-acyloxy, C
6
-C
10
-aryloxy, C
6
-C
10
-aryl, benzyl, fluorine, chlorine, bromine, OH, NO
2
, OSO
2
CF
3
, CN, COOH, CHO, SO
3
H, SO
2
R, SOR, where R is C
1
-C
4
-alkyl, C
6
-C
10
-aryl or benzyl, NH
2
, NH—C
1
-C
8
-alkyl, N—(C
1
-C
8
-alkyl)
2
, CF
3
, NHCO—C
1
-C
4
-alkyl, N—C
1
-C
4
-alkyl-CO—C
1
-C
4
-alkyl, COO—C
1
-C
8
-alkyl, CONH
2
, CO—C
1
-C
8
-alkyl, NHCOH, NCOO—C
1
-C
4
-alkyl, CO-phenyl, COO-phenyl, CHCH—CO
2
—C
1
-C
8
alkyl, CHCHCO
2
H, PO-phenyl
2
, PO—(C
1
-C
4
-alkyl)
2
, 5-membered heteroaryl and 6-membered heteroaryl in each case containing O, S and/or N as heteroatoms; and
R
6
and R
7
are, independently of one another, hydrogen, C
1
-C
12
-alkyl, C
1
-C
12
-hydroxyalkyl, unsubstituted or substituted phenyl, or C
3
-C
8
-cycloalkyl, or R
6
and R
7
together with the N atom form a 5- or 6-membered aliphatic or aromatic ring which may contain 1 or 2 further atoms selected from the group consisting of N, O and S as heteroatoms,
by reacting haloaromatics of the formula (II)
Ar—Hal (II)
where Hal is Cl, Br or I,
with an amine of the formula (III)
R
6
R
7
NH (III)
wherein the reaction is carried out in the presence of a palladaphosphacyclobutane of the formula (IV)
where
R
1a
, R
2a
are, independently of one another, hydrogen, C
1
-C
4
-alkyl, C
3
-C
12
-cycloalkyl, C
1
-C
4
-alkoxy, fluorine, N—(C
1
-C
4
-alkyl)
2
, CO
2
—C
1
-C
4
-alkyl, OCO—C
1
-C
4
-alkyl or substituted or unsubstituted aryl,
R
3a
, R
4a
, R
5a
and R
6a
are, independently of one another C
1
-C
8
-alkyl, C
3
-C
12
cycloalkyl, substituted or unsubstituted aryl;
or R
1a
and R
2a
, or R
2a
and R
3a
, or R
3a
and R
4a
together form an aliphatic ring having from 4 to 10 carbon atoms,
or R
5a
and R
6a
together with the P atom form a saturated or unsaturated 4- to 9-membered ring, or R
4a
and R
5a
form a bridging 1,&ohgr;-alkanediyl chain having from 2 to 7 carbon atoms, and
Y is an anion of an inorganic or organic acid, an &agr;,&ggr;-diketo compound or a 5- to 6-membered nitrogen-containing heterocycle,
in the presence of a base and in the presence or absence of an ionic halide in a solvent at temperatures of from 20 to 200° C.
The synthesis of the palladaphosphacyclobutanes is described in DE-A1-196 47 584. Preference is given to compounds of the formula (IV) in which
R
1a
and R
2a
are, independently of one another, hydrogen, methyl, ethyl, cyclopentyl, cyclohexyl, methoxy, ethoxy, fluorine, phenyl, tolyl or naphthyl;
R
3a
and R
4a
are, independently of one another, C
1
-C
4
-alkyl, C
5
-C
6
-cycloalkyl, substituted or unsubstituted C
6
-C
10
-aryl or R
3a
and R
4a
together form an aliphatic ring having from 5 to 6 carbon atoms;
R
5a
and R
6a
are, independently of one another, C
1
-C
4
-alkyl, C
5
-C
6
-cycloalkyl, phenyl, naphthyl, anthracenyl, each of which may be unsubstituted or substituted by from 1 to 3 CF
3
—, C
1
-C
4
-alkyl or C
1
-C
4
-alkoxy groups;
and Y is acetate, propionate, benzoate, chloride, bromide, iodide, fluoride, sulfate, hydrogensulfate, nitrate, phosphate, trifluoromethanesulfonate, tetrafluoroborate, tosylate, mesylate, acetylacetonate, hexafluoracetylacetonate or pyrazolyl.
Particular preference is given to compounds of the formula (IV) in which
R
1a
and R
2a
are, independently of one another, hydrogen or methyl;
R
3a
and R
4a
are, independently of one another, methyl, ethyl or phenyl;
R
5a
and R
6a
are, independently of one another, phenyl, naphthyl, o-trifluoromethylphenyl, o-trifluoromethyl-p-tolyl, o-trifluoromethyl-p-methoxyphenyl, o-methoxyphenyl, o,p-dimethoxyphenyl, o,o,p-trimethoxyphenyl, anthracenyl, tert-butyl, n-butyl, isopropyl, isobutyl, cyclohexyl or 1-methylcyclohexyl.
Very particular preference is given to the following compounds of the formula (IV):
trans-di-&mgr;-acetatobis[2-[bis(1,1-dimethylethyl)phosphino]-2-methylpropyl-C,P]dipalladium(II),
trans-di-&mgr;-acetatobis[2-[1,1-dimethylethyl)phenylphosphino]-2-methylpropyl-C,P]dipalladium(II),
trans-di-&mgr;-chlorobis[2-[bis(1,1-dimethylethyl)phosphino]-2-methylpropyl-C,P]dipalladium(II),
trans-di-&mgr;-chlorobis[2-[(1,1-dimethylethyl)phenylphosphino]-2-methylpropyl-C,P]dipalladium(II),
trans-di-&mgr;-bromobis[2-[bis(1,1-dimethylethyl)phosphino]-2-methylpropyl-C,P]dipalladium(II) and
trans-di-&mgr;-bromobis[2-[(1,1-dimethylethyl)phenylphosphino]-2-methylpropyl-C,P]dipalladium(II).
The palladium catalysts are synthesized before the actual reaction, but can also be generated in situ, as described, for example, in EP-A1-0802173. However, in the case of a prolonged reaction time, the in-situ mixtures (molar ratio Pd:P=1:1) prove to have little stability and frequently lead to deposition of palladium. This disadvantage is surprisingly overcome by the use according to the invention of previously prepared palladaphosphacyclobutanes.
Palladaphosphacyclobutanes generally have a dimeric structure. However, in the case of particular compounds (e.g. Y=acetylacetone, hexafluoracetylacetone) monomeric, oligomeric or even polymeric structures may be present.
During the catalysis cycle, the dimeric structure is broken up by bridge cleavage reactions with inorganic and organic nucleophiles, so that the mononuclear complexes of the formulae (V) and (VI)
may be the actual catalytically active species. The complexes of the formulae (V) and (VI) are in equilibrium w
Geissler Holger
Haber Steffen
Meudt Andreas
Scherer Stefan
Vollmueller Frank
Barts Samuel
Clariant GmbH
Hanf Scott E.
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