JPS648611B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method for producing secondary amines, and more particularly, the present invention relates to an improved method for producing secondary amines, and more particularly, aromatic amines are reduced to aldehydes or This is a method for producing a secondary amine by reductive alkylation with a ketone, which is characterized in that the raw aromatic amine is treated with an alkaline compound in advance.

It is known to reductively alkylate amine compounds by reacting them with aldehydes or ketones in the presence of hydrogen and a reducing catalyst to produce secondary amines. However, in conventional reductive alkylation, side reactions such as reduction of aldehydes or ketones to alcohols, hydrogenation of benzene nuclei, and hydrolysis occur, and under conditions that suppress such side reactions, unreacted amines are It was difficult to obtain a satisfactory yield under any conditions as a large amount remained.

For this reason, the present inventors have conducted intensive studies to suppress side reactions such as the production of alcohol and to produce the desired secondary amine in high yield. The inventors have discovered that by treating aromatic amines with an alkaline compound in advance, side reactions can be suppressed and the desired secondary amines can be obtained in high yield, leading to the present invention.

That is, the present invention provides a method for producing a secondary amine by reductively alkylating an aromatic amine with an aldehyde or ketone in the presence of a reduction catalyst consisting of hydrogen and a group metal of the periodic table. This is a method for producing a secondary amine, which is characterized by treating the amine with an alkaline compound in advance.

Aromatic amines applicable to the present invention include, for example, aniline, alkylaniline (e.g. toluidine), alkoxyaniline (e.g. anisidine, phenetidine), aryloxyaniline (e.g. phenoxyaniline), nitroaniline (e.g. p-nitroaniline). , o-nitroaniline), arylene diamines (e.g. p-
Phenylene diamine, o-phenylene diamine,
Examples include p-aminodiphenylamine), 4-isopropylaminoaniline, and 4-sec-butylaminoaniline. Examples of aldehydes or ketones include formaldehyde, acetaldehyde, alicyclic aldehydes (e.g. cyclohexylaldehyde), and aromatic aldehydes. (e.g. benzaldehyde), alkyl-alkyl ketones (e.g. acetone, methyl ethyl ketone, methyl isopropyl ketone, methyl isobutyl ketone, mesityl oxide), aryl-alkyl ketones (e.g. acetophenone), aryl-
Examples include aryl ketones (eg, benzophenone), alicyclic ketones (eg, cyclohexanone, methylcyclohexyl ketone, phenylcyclohexyl ketone), and the like.

The amount of aldehyde or ketone used is usually 1 to 10 times the mole of the aromatic amine, preferably 1.1 to 3 times the amount by mole. Even if it is used 10 times or more by mole, there is no adverse effect on the reaction itself, but it is economically disadvantageous because the productivity decreases.

In many cases, the excess amount of the above-mentioned aldehyde or ketone is used as the reaction solvent as it is, but other inert solvents can be used as necessary. Examples of such solvents include alcohols represented by methanol, ethanol, propanol, butanol, pentanol, and 4-methyl-pentanol (preferably those corresponding to aldehydes or ketones used in the reductive alkylation reaction); Aliphatic or aromatic hydrocarbons, their halogen derivatives, ethers, and anything else inert to the reductive alkylation reaction can be used.

Examples of the reduction catalyst include palladium or platinum supported on carbon, and the amount used is as follows:
The amount of metal relative to aromatic amine is usually 0.001~
0.2% by weight, preferably 0.003-0.05% by weight
It is.

The reaction temperature is 20 to 200°C, preferably 80 to 170°C, and the hydrogen pressure in the reaction system is not particularly limited, but from the viewpoint of reaction rate or reaction control, it is usually 50 to 170°C.
~40Kg// ^cm2・G.

Examples of the method of treating a raw aromatic amine with an alkaline compound, which is a feature of the present invention, include (1) a method of distilling an aromatic amine in the coexistence of an alkaline compound, and (2) a method of treating an aromatic amine with a solid or liquid alkaline compound. (2)
In the case of the above method, it may be distilled after the contact treatment, or it may be used as it is as a raw material for reductive alkylation without any distillation. Whichever method is used, the effect is greater than when no alkali treatment is performed.

Suitable alkaline compounds used in such treatment include alkali metal or alkaline earth metal oxides, hydroxides, or their salts with weak acids, such as caustic soda, bicarbonate of soda, soda carbonate, Examples include caustic potassium, potassium bicarbonate, potassium carbonate, quicklime, slaked lime, calcium carbonate, barium oxide, barium hydroxide, barium carbonate, and the like.

In the alkali treatment by the method (1) above, the amount of alkaline compound used is usually 0.01 to 5% by weight, preferably 0.1 to 2% by weight based on the aromatic amine.
Weight%. In method (2) above, room temperature
It is sufficient if the solid or liquid alkaline compound and the aromatic amine come into contact within a temperature range of 200°C.Specific methods include mixing and stirring the alkaline compound and the aromatic amine; There are methods such as passing an aromatic amine through a packed bed. In the case of the former method, the amount of alkaline compound used is the same as in the case of method (1) described above.

The present invention will be explained below with reference to Examples.

Example 1 2 g of sodium carbonate was added to 100 g of p-aminodiphenylamine and distilled at a reduced pressure of 1 mmHg to obtain 95 g of a fraction having a top temperature of 180 to 190°C.

After stirring, 74 g (0.4 mol) of p-aminodiphenylamine obtained above, 120 g (1.2 mol) of methyl isobutyl ketone, and 1.33 g of 1% platinum charcoal catalyst were placed in an autoclave equipped with a thermometer, gas inlet tube, and gas outlet tube. After the tank was replaced with nitrogen, the temperature was raised to 140°C and hydrogen gas was filled in until the internal pressure reached 30Kg/cm ² ·G. The reaction is carried out while maintaining the same temperature. Since the hydrogen pressure decreases as the reaction progresses,
During this time, if the hydrogen pressure becomes 5Kg/cm ²・G, 30Kg/
Fill with hydrogen gas until it reaches ^cm2・G and repeat this operation. Four hours after the start of the reaction, the rate of decrease in hydrogen pressure became slow (the rate of hydrogen absorption became slow), and the decrease was only 1 kg/cm ² ·G per hour, so heating was stopped.

After cooling the reactant, the pressure is reduced, the contents are taken out and the catalyst is separated. After making the reaction solution homogeneous by adding isopropyl alcohol to it, analysis results using high performance liquid chromatography internal standard method and gas chromatography internal standard method revealed that N-1,3-
The yield of dimethyl-N'-phenyl-p-phenylenediamine was 99.4%, the unreacted rate was 0.3%, and the rate of methyl isobutyl carbinol by-product was 1.0%.

Example 2 148 g (0.8 mol) of p-aminodiphenylamine obtained by alkali treatment in the same manner as in Example 1, 139 g (2.4 mol) of acetone, and 1.33 g of 1% platinum charcoal catalyst.
After putting it in an autoclave and replacing it with nitrogen,
Hydrogen gas is heated to 140℃ while internal pressure is 30Kg/
Enclose until cm ²・G. Thereafter, the reaction was carried out in the same manner as in Example 1, and heating was stopped 2 hours after the start of the reaction. After post-treatment and analysis in the same manner as in Example 1, N-isopropyl-N'-phenyl-
Yield of p-phenylenediamine 98.4%, unreacted rate
0.1% or less, isopropyl alcohol by-product rate 2.7%
It was hot.

Example 3 100 g of p-phenylenediamine was melted at 180°C under a nitrogen atmosphere, and 5 g of granulated caustic soda was added to it.
was added, stirred for 30 minutes, and then heated. 43g of p-phenylenediamine thus treated
(0.4 mol), methyl ethyl ketone 173g (2.4 mol)
and 0.86 g of 5% palladium charcoal were charged into an autoclave, and after nitrogen substitution, hydrogen gas was charged. The reaction was carried out in the same manner as in Example 1 under the conditions of a reaction temperature of 90° C. and a hydrogen pressure of 5 to 20 Kg/cm ² ·G, and heating was stopped 2.5 hours after the start of the reaction. When post-processing and analysis were performed in the same manner as in Example 1, N,
The yield of N'-di-sec-butyl-p-phenylenediamine was 97.8%, the unreacted rate was 0.8%, and the sec-butyl alcohol by-product rate was 1.9%.

Comparative Example 1 A reaction was carried out in the same manner as in Example 1 except that p-aminodiphenylamine which was not subjected to alkali treatment was used. However, the reaction time is 5 hours.

After post-processing and analysis in the same manner as in Example 1,
N-1,3-dimethylbutyl-N'-phenyl-
Yield of p-phenylenediamine 74.2%, unreacted rate
19.5%, methyl isobutyl carbinol byproduct rate
It was 4.0%.

Comparative Example 2 A reaction was carried out in the same manner as in Example 1, except that p-aminodiphenylamine which was not subjected to alkali treatment was used. However, the reaction temperature was 180°C and the reaction time was 5 hours.

After post-processing and analysis in the same manner as in Example 1,
N-1,3-dimethylbutyl-N'-phenyl-
Yield of p-phenylenediamine 72.4%, unreacted rate
0.6%, methyl isobutyl carbinol byproduct rate
It was 17.4%.

Comparative Example 3 A reaction was carried out in the same manner as in Example 2, except that p-aminodiphenylamine was used without alkali treatment. However, the reaction time is 5 hours.

After post-processing and analysis in the same manner as in Example 1,
The yield of N-isopropyl-N'-phenyl-p-phenylenediamine was 91.7%, the unreacted rate was 5.7%, and the isopropyl alcohol by-product rate was 7.5%.

Comparative Example 4 A reaction was carried out in the same manner as in Example 3, except that p-phenylenediamine which was not subjected to alkali treatment was used. However, the reaction time is 5 hours.

After post-processing and analysis in the same manner as in Example 1,
The yield of N,N'-sec-butyl-p-phenylenediamine was 86.8%, the unreacted rate was 13.0%, and the rate of sec-butyl alcohol by-product was 5.0%.

Claims (1)

[Scope of Claims] 1. A method for producing a secondary amine by reductively alkylating an aromatic amine with an aldehyde or ketone in the presence of a reduction catalyst consisting of hydrogen and a group metal of the periodic table. A method for producing a secondary amine, which comprises treating a group amine with an alkaline compound in advance. 2 Claim 1 in which an alkali metal or alkaline earth metal oxide, hydroxide, or a salt thereof with a weak acid is used as the alkaline compound.
The method described in section. 3. The method according to claim 1, in which the raw aromatic amine is distilled in the presence of an alkaline compound as the method for treating with an alkaline compound. 4. The method according to claim 1, in which the aromatic amine is brought into contact with a solid or liquid alkaline compound as the method of treatment with an alkaline compound.