Catalytic synthesis of N-alkylated anilines from olefins and...

Details Catalytic synthesis of N-alkylated anilines from olefins and... Catalytic synthesis of N-alkylated anilines from olefins and...

2000-07-03

2001-04-24

Barts, Samuel (Department: 1621)

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

Organic compounds

Amino nitrogen containing

C564S399000, C564S404000, C564S405000

Reexamination Certificate

active

06222073

ABSTRACT:

DESCRIPTION
The present invention relates to a novel process for the preparation of N-alkylated anilines.
Substituted anilines are of industrial importance as precursors for dyes, fine chemicals, pharmaceuticals and agrochemical products. In this context, N-alkylated anilines are also industrially important. The preparation of substituted N-alkylated anilines is carried out industrially essentially by nitration of a corresponding aromatic, subsequent hydrogenation and alkylation by means of alkyl halides (e.g. methyl iodide) or alkyl sulfates. In all known alkylations of anilines, stoichiometric amounts of salt byproducts are therefore obtained, which is ecologically disadvantageous. In addition, the alkylations with functionalized alkyl halides, such as, for example, arylethyl bromides, take place with insufficient selectivity, so that further byproducts are formed.
It is the object of the present invention to provide a process for the preparation of substituted, N-alkylated anilines from simple starting materials under mild reaction conditions, which can be carried out on an industrial scale and in which no salt byproducts are obtained.
This object is achieved by a process for the preparation of an N-arylethylaniline of the formula (I)
Ar—N(R
1
)
2-n
(CHR
2
CHR
3
Ar′)
n
  (I)
by reacting an aromatic olefin of the formula (II)
Ar′CR
3
═CHR
2
  (II)
with an aniline of the formula (III)
Ar—N(R
1
)
2-n
(H)
n
  (III)
in an inert solvent in the presence of at least one basic catalyst selected from the group consisting of alkali metal alcoholates and alkaline earth metal alcoholates or alkali metal amides and alkaline earth metal amides, where, in the formulae (I) to (III),
Ar and Ar′, independently of one another, are an aryl radical selected from the group consisting of the fused and nonfused C
6
-C
22
-aromatics and of the fused or nonfused C
5
-C
22
heteroaromatics which have at least one nitrogen, oxygen or sulfur atom in the ring;
R
1
, R
2
and R
3
, independently of one another, are a hydrogen atom, a C
1
-C
8
-alkyl radical or an aryl radical Ar; and
n is the number 1 or 2.
The process according to the invention is particularly suitable for reacting primary aromatic amines and secondary aliphatic and aromatic amines.
Furthermore, it is possible for the N-arylethylaniline of the formula (I), in an extension of the intermolecular coupling between the aromatic olefin of the formula (II) and the aniline of the formula (III), to be prepared by an intramolecular amination of a corresponding compound.
An important property of the process according to the invention is that the anilines for the first time react with styrenes under base catalysis, generally with good to very good yields of from 70 to 99%. Salt byproducts are not formed here.
Examples of the aryl radical Ar are phenyl, naphthyl, anthryl, phenanthryl and biphenyl, pyridyl, furfuryl or pyrazolyl radicals.
The inert solvent can be selected from the group consisting of aromatic hydrocarbons, such as toluene, xylenes, anisole and tetralin, and aliphatic ethers, such as tetrahydrofuran, dimethoxyethane, dioxane, tetrahydropyran and formaldehyde acetals.
According to a preferred embodiment of the invention, the basic catalyst is selected from the group consisting of the tert-butanolates, methanolates, propanolates and 2-ethylhexanolates of the alkali metals and alkaline earth metals, in particular from the corresponding potassium and sodium ompounds. Examples of these are potassium tert-butanolate, potassium methanolate, potassium ethanolate, potassium propanolate, potassium isopropanolate, potassium 2-ethylhexanolate, potassium phenolate and potassium 2-amino-1-methanolate.
Potassium tert-butanolate is particularly preferred here.
In a further, likewise preferred embodiment according to the invention, the basic catalyst is selected from the amides, dimethylamides, diisopropylamides and anilides of the alkali metals and alkaline earth metals, in particular their potassium and sodium compounds.
Examples of these are potassium amide, potassium dimethylamide, potassium diisopropylamide and potassium anilide.
It is also possible to use, as basic catalyst, a mixture of at least two of the basic catalysts described above.
The catalyst can be used directly in the form of one of said compounds or similar compounds. However, it is sometimes advantageous to prepare the active compound in situ from suitable precursors, owing to the stability of the basic catalyst.
The basic catalyst can be used in an amount of from 0.01 to 20 mol %, in particular from 0.1 to 5 mol %, based on the aniline of the formula (III).
The aryl radicals Ar or Ar′ in the formulae (I) to (III) can, independently of one another, have up to 8 substituents which are identical or different and are a hydrogen, fluorine, chlorine, bromine or iodine atom or a C
1
-C
8
-alkyl, C
1
-C
8
-alkoxy, C
1
-C
8
-acyloxy, HO, O
2
N, CN, HOC(O), HC(O), HOS(O
2
), R
4
S(O)
2
, R
4
S(O), H
2
N, R
4
N(H), R
4
2
N, R
4
C(O)N(H), R
4
C(O), (OCH)HN, Ar″C(O), ArC(O)O, CF
3
, H
2
NC(O), R
4
OC(O)C(H)═C(H), Ar″
2
P(O), R
4
2
P(O) or R
4
3
Si radical or a heteroaryl radical having 5 or 6 atoms in the aryl ring, R being a C
1
-C
12
-alkyl radical and Ar″ being selected from the group consisting of the fused or nonfused C
6
-C
22
-aromatics and of the fused or nonfused C
5
-C
22
-heteroaromatics which have at least one nitrogen, oxygen or sulfur atom in the ring.
The reaction takes place at temperatures of from 0 to 200° C., in particular at from 10 to 150° C. and preferably at from 20 to 120° C.
In the case of some aromatic olefins of the formula (II), it may be advantageous, owing to the tendency toward secondary oligomerization and polymerization reactions, to add a polymerization inhibitor. The conventional polymerization inhibitors may be used for this purpose, such as, for example, p-quinone.
The following examples serve merely to illustrate the process.


REFERENCES:
patent: 0598962 (1994-06-01), None
patent: 0814075 (1997-12-01), None
Arnauld, T., et al,Tetrahedron53:4137-4144, “The Chemistry of Pentavalent Organobismuth Reagents. Part 14. Recent Advances in the Copper-Catalyzed Phenylation of Amines”. (1997).

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