CA1180723A

CA1180723A - Process for preparing 4-aminomethylbenzoic acid from 4-hydroxyiminomethylbenzoic acid

Info

Publication number: CA1180723A
Application number: CA000385925A
Authority: CA
Inventors: Masaaki Takahashi; Takashi Yamauchi; Akira Iizuka
Original assignee: Kureha Corp
Current assignee: Kureha Corp
Priority date: 1980-09-17
Filing date: 1981-09-15
Publication date: 1985-01-08
Also published as: FR2490220B1; JPS6017780B2; FR2490220A1; GB2084146A; JPS5753441A; DE3137091C2; DE3137091A1; GB2084146B

Abstract

TITLE OF THE INVENTION

ABSTRACT OF THE DISCLOSURE

The present invention relates to a process for preparing 4-aminomethylbenzoic acid from 4-hydroxyiminomethyl-benzoic acid dispersed in an aqueous medium by a catalytic hydrogenation. The catalytic hydrogenation according to the present invention is carried out in a mild condition in an aqueous medium.

Description

~l8~.)7~3 BACKGROUND A~D DE~AI'LED'D'E~'CRI'PTION OF THE IN~ENTION
The present inYentiOn relates to a process for preparing 4-aminomethylbenzoic acid from 4-hydroxyiminomethyl-benzoic acid. More particularly, the present invention relates to a process in which 4-hydroxyiminomethylbenzoic acid is reduced to 4-aminomethylbenzoic acid by using a catalyst containing at least a palladium compound or a rhodium compound within an aqueous medium of pH of not higher than 7.
Concerning the process for preparing 4-aminomethyl~
benzoic acid(hereinafter referred to as A~), the following methods have been hitherto known:
(1) Amination of 4-chloromethylbenzoic acid by aqua ammoniae, 1,

(2) Reduction of 4-carboxybenzaldehyde in the presence of Raney Nickel in methanol containing aqua ammoniae(refer to Japanese Patent Publication No. 34-42L),

(3) Reduction of methyl 4-cyanobenzoate in the presence of ,' Raney Nlckel in an aqueous alkali solution(refer to Japanese Patent Application Laying Open No. 48-57951) and

(4) Reduction of 4-cyanobenzoic acid in the presence of a ruthenium catalyst in an aqueous alkali solution(refer to Japanese Patent Application Laying Open No. 51-32536).
However, although method (1) is carried out under an ordinary pressure, a large amount of by-products such as secondary amine and tertiary amine is formed and accordingly, the yield of AM if not favorable; in order to improve the yield of method (2), it is necessary to carry out the reaction under a high pressure;

~ '., - 1 - `

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and the starting material of (3) and (4)~ 4-cyanobenzoic acid, is not easily prepared in an industrial scale.
Accordingly, every one of the publicly known methods cannot be said to be the sufficiently satisfactory method for preparing 4-aminomethylbenzoic acid.
It is an object of the present invention to provide a process for preparing 4~aminomethylbenzoic acid, comprising catalytically hydrogenating 4-hydroxyiminomethylbenzoic acid dispersed in an aqueous acidic- or neutral medium in the presence of a catalyst containing at least one palladium compound or one rhodium compound. Other objects will appear hereinafter.
The present invention will be explalned more in detail as follows:
The starting substance of the present invention,i.e., 4-hydroxyiminomethylbenzoic acid is an oxime compound which may be obtained by the reaction of 4-carboxybenzaldehyde and hydroxylamine hydrochloride. 4-Carboxybenzaldehyde is obtained by oxidation of mono- or dichloromethylbenzoic acid as the object compound. However, industrially, the 4-carboxybenzaldehyde obtained as a by-product in the production of terephthalic acid which is the raw material for synthetic fibers, is utili ed.
The catalyst used in the process of the present invention (hereinafter referred to as the present process) is a catalyst containing at least one member selected from the group consisting of palladium compounds and rhodium compounds, and preferably, a metallic catalyst comprising palladium and/or ~
i 07~23 rhodium or a mixed catalyst comprising one or two members of palladium and rhodium and one or more members of other meta]s of platinum group, particularly, platinum and ruthenium. However, mixed catalysts containing palladium, rhodium and platinum are excluded in cases where the reduction is carried out in an aqueous acidic medium. Specifically preferable is an unitary catalyst comprising palladium or rhodium.
The form of the active metallic element contained in the catalyst of the present process is metal, compound of the metal, for instance, oxide, or alloy of the metals. These metals and metal compounds are used while being carried on a carrier such as activated carbon and diatomaceous earth, the preferable i1 ¦ carrier being activated carbon. The -specifically preferable catalyst is the catalyst comprising palladium metal carried on activated carbon. In the ordinarily used c-atalyst, the content of the metallic element carried on the carrier is about 2 to 10 %
by weight of the total weight of the catalyst. The amount of catalyst used is so that the total sum of the weight of palladium or rhodium becomes to about 0.25 to 10 % by weight, preferably, about 0.5 to 5 % by weight of 4-hydroxyiminomethylbenzoic acia.
~The reaction medium used in the present process is the medium of pII of lower than 7, that is, an acidic medium or a neutral medium.
In the reduction of an oxime compound, an organic sol-vent i5 generally used as the reaction medium, aqueous medium not being used because of the extremely small solubility and Il I,i ~ )7~3 the presumable hydrol~sis of the oxime compound in an aqueous medium.
However, in the present process, it is characteristic that the hydrogena-tion of the oxime compound dispersed in an aqueous medium is possibly carried out at a relatively low temperature and under a relatively low pressure. Namely, the starting substance, the oxime compound, is reduced in an emulsified state in an acidic medium containing a mineral acid, and the thus formed AM by reduction of the oxime becomes to the salt of the mineral acid. The reason why the mineral acid salt of AM is easily obtained in a high yield is considered to be the protection of tne aminomethyl group by the mineral acid resulting in the prevention of side reactions such as deamination and formation of secondary amine.
~ On the other hand, in the case where the reaction medium is an aqueous neutral medium, the reduction of the oxime compound proceeds in a nearly emulsified state of the oxime, and after the reaction is over, AM is obtained as crystallites.
Under the neutral condition, it is characteristic that the reaction proceeds in a heterogeneous state.
In the case where the reaction is carried out in an aqueous basic medium, although the reaction proceeds in a homogeneous system, it has been found that by-production of secondary amine is inevitable resulting in a poor yield of AM.
As an aqueous acidic medium, an aqueous solution of a mineral acid such as hydrochloric acid, sulfuric acid and llflO~3 ¦ nitric acid which forms a water-soluble salt with AM, is used at an ordinary concentration of 3 to 5 %. The amount of the mineral acid used in the reaction is at least more than the equivalent amount of 4 hydroxyiminomethylbenzoic acid, preferably, about 1 to 3 times of the equivalent amount. The amount of the reaction medium is 10 to 50 times by weight of 4-hydroxy-¦~iminomethylbenzoic acid, preferably, 10 to 20 times in bothcases of acidic- and neutral conditions.
I The reaction of the present process is ordinarily llcarried out at a temperature of about 10 to about 80C, and in the case of using a palladium catalyst, the reaction proceeds smoothly enough at about 10 to about 50C, however, in the case of using rhodium catalyst, a little higher temperature , l¦is necessary.
The reaction of the present process can be carried ¦out under a pressure of hydrogen of higher than 1 atm, and the reaction easily proceeds under a pressure of hydrogen of I 1 to 10 atm in usual cases.
~ The time period of the reaction of the present process depends on the reaction conditions such as the kind of the catalyst and the amount thereof, the temperature, the pressure of hydrogen, etc., however, the absorption of hydrogen completes usually within about 2 to 7 hours.
After the reaction is over, in the case of using an aqueous acidic medium, the catalyst is removed by filtering the real ion mixt~re and the crystals of ~ is sedimented by _ 5 _ 1~

)7Z3 neutralizing the filtrate, and after collecting the crystals by filtration, the filtrate is condensed to further obtain the crystals of AM. On the other hand, in the case of using ~an aqueous neutral medium, concentrated aqua ammoniae or l concentrated hydrochloric acid is added to the reaction ! mixture to dissolve the product, and after removing the I catalyst by filtration, the filtrate is neutralized to obtain ¦Ithe crystals of AM.
Il The present invention will be further explained l~more in detail while referring to the non-limitative examples Illas follow5:

! i In an autoclave of a capacity of 500 ml made of llpressure-resistant glass, 16.5 g (0.1 mol) of 4-hydroxyimino-I ~ methylbenzoic acid was dispersed into 200 ml of aqueous 3.5 %
hydrochloric acid solution, and 1.6 g of 5 ~ palladium on activated carbon (hereinafter abbreviated to as 5 ~ Pd-C~
was added to the dispersion. The catalytlc hydrogenation . of 4-hydroxyiminomethylbenzoic acid was carried out under the initial pressure of hydrogen of 5 kg/cm at a temperature of from ordinary temperature to 45C. The absorption of hydrogen came to an end after 3 hours. After removing the catalyst by filter-ing the reaction mixture, the filtrate was condensed and the thus sedimented crystals were collected by filtration, washed with a~ tone and dried to obtain 16.0 g of white powdery .
~ ll .

li~O~Z3 ll ~ ll crystals melting at 2~4 - 288C. The crystalline product thus obtained was identified as 4-aminomethylbenzoic acid hydrochloride by comparing its infrared absorption spectrum with that of the authentic specimen of 4-aminomethylbenzoic acid hydrochloride, the yield being 85.0 %.
A saturated aqueous solution of the product, 4-amino-methylbenzoic acid hydrochloride(hereinafter abbreviated to as AM-~CL) was neutralized with aqueous 20 % sodium hydroxide Il solution, and after collecting the thus sedimented crystals by ¦ filtration, the filtrate was condensed to obtain a further amount of the crystals. After drying the thus obtained crystalsj the combined crystals amounted to 12.5 g.

, '.
~XAMPLE 2 In the same manner as in Example 1 except for using distilled water as the reaction medium and at a temperature of from room temperature to 40C, the catalytic hydrogenation of 4-hydroxyiminomethylbenzoic acid was carried out. The absorption of hydrogen came to an end after 3 hours. After adding 20 g of concentrated hydrochloric acid into the reaction mixture to ! dissolve the product, the mixture was filtered to remove the catalyst and the filtrate was condensed under a reduced pressure.
The thus sedimented crystals were collected by filtration, washed with acetone and dried to obtain 14.5 g of white powdery crystals which were identified as 4-aminomethylbenzoic acid by comparing its in:~ared absorption with that of the authentic sFecimen of ~ 723 4-aminomethylbenzoic acid hydrochloride. The yield was 77.3 %.
By treating the thus obtained product with alkali in the same manner as in Example 1, to obtain 8.2 g of crystals in the first step and 2.6 g of crystals in the second step. These crystals were identified as ~M by comparing their infrared absorption spectrum with that of the authentic specimen of 4-aminomethylbenzoic acid.

In the same manner as in E~ample 1, except for using as the catalyst 5 % rhodium carried on activated carbon(herein-after abbreviated to as 5 % Rh-C), catalytic hydrogenation of 4-hydroxyiminomethylbenzoic acid was carried out at a temperature from room temperature to 60C. Absorption of hydrogen came to an end after 5 hours. By treating the reaction mixture as in Example 2, 14.0 g of white powdery product melting at 282 to 285C was obtai~red, and identified as AM~HCl by comparing its infrared absorption spectrum with that of the authentic specimen of AMHCl, the yield being 74.6 %.
By treating the thus obtained product with neutraliza-tion with alkali, 10.2 g of white powdery substance was prepared, which was identified as AM by infrared spectral analysis.

EXAMPLES 4 to 6 A series of catalytic hydrogenation experiments were carried out in the same manner as in Example 1, however, using O~Z3 each one of the mixed catalysts shown in Table at a temperature of from room temperature to 50C. In these experiments, the reactions of hydrogenation of the oxime moiety and of the benzene ring could be traced by observing the consumed amount of hydrogen corresponding to the reduced pr~ssure of hydrogen ~ in the autoclave.

i After the reaction was over, the catalyst was removed by filtering the reaction mixture, and after confirming that the 1~ filtrate contained solely AM-HC1 by the presenc-e of ultraviolet l~ absorption at 228 nm, the filtrate was condensed. The thus sedimented crystals were collected by filtration and dried.
,~ The product was identified by infrared analy-sis to be ~M HCl.
., i I Table '`
!l , EXAMPLE Composition of Period for Product --catalyst H absorption --No 2 (hours) wRight(g) Identification ., .

5 % Pd-C 1 6 2.5 13.7 AM-HCl 5 % Pt-C 1.6 5 0 13 1 the same 5 % Rh-C 1.6 as above 5 % Pd-C 1~6 the same

6 5 % Ru-C**1.6 2.5 13.5 as above Note: *5 % Pt-C means a catalyst containing 5 % by weight of platinum on activated carbon.
**5 % Ru C means a catalyst containing 5 % by weight of uthenium on activated car~on.

g _ 11.~07'~3 In the same manner as in Example 1, except for using distilled water as the reaction medium and using a mLxed catalyst consisting of 1.6 g of 5 % Pd-C, 1.6 g of 5 % Pt-C and 1.6 g of 5 % Rh-C, catalytic hydrogenation of 4-hydro~yiminomethylbenzoic acid was carried out at a temperature of from room temperature to 50C. The absorption of hydrogen came to an end after about Il 4 hours.
1~ Since some crystals appeared in *he reaction mixture, 1l 20 ml of concentrated hydrochloric acid was added to the mixture to dissolve the crystals, and the solution was filtered to remove , the catalyst by filtration. After condensing the filtrate and I adding acetone to the condensate to sediment the crystals, they were collected by filtration and dried to obtain white powdery 1~ crystals melting at 284 to 286C in amount of 14.5 g, which were ideneified as ~~ C1 by in rared analysis, the yield being 77 %.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A process for producing 4-aminomethylbenzoic acid, comprising catalytically reducing 4-hydroxyiminomethylbenzoic acid dispersed in a mineral acid or in water in the presence of a catalyst containing palladium and/or rhodium carried on activated carbon at a temperature of 10 to 80°C under an initial hydrogen pressure of 1 to 10 atmospheres for 2 to 7 hours.

2. A process according to claim 1, wherein the amount of said catalyst is 0.25 to 10% by weight of the amount of said 4-hydroxyiminomethylbenzoic acid to be subjected to reduction.

3. A process according to claim 1, wherein the amount of palladium and/or rhodium is 2 to 10% by weight of the total amount of said catalyst.

4. A process for producing 4-aminomethylbenzoic acid, comprising catalytically reducing 4-hydroxyiminomethylbenzoic acid dispersed in a mineral acid in the presence of a catalyst containing palladium and/or rhodium carried on activated carbon at a temperature of 10 to 80°C under an initial hydrogen pressure of 1 to 10 atmospheres for 2 to 7 hours while maintaining the pH of the dispersion at a value lower than 7, the amount of palladium and/or rhodium being 2 to 10% by weight of the total amount of said catalyst, and the amount of said catalyst being 0.25 to 10% by weight of the initial amount of 4-hydroxyiminobenzoic acid.