JP2002088014A - Method for producing carbocyclic aromatic carboxylic acids - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a carbocyclic aromatic carboxylic acid by safely carrying out a reaction under an industrially advantageous and mild reaction condition in a high purity in a high yield. SOLUTION: A carbocyclic aromatic aldehyde is heated in a nonpolar organic solvent in the presence of an alkali metal hydroxide. Consequently, the reaction can be safely carried out under an industrially advantageous and mild condition without requiring an expensive oxidizing agent and using a specific reactor and a carbocyclic aromatic carboxylic acid can be obtained in a high purity in a high yield.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to pharmaceuticals, agricultural chemicals,
The present invention relates to a method for producing a carbocyclic aromatic carboxylic acid useful as a synthetic intermediate such as a liquid crystal compound.

[0002]

BACKGROUND OF THE INVENTION Carbocyclic aromatic carboxylic acids have hitherto been
The corresponding aromatic aldehydes were produced by permanganate oxidation, chromic acid oxidation, etc., but each produced not only a large amount of by-products, but also had problems such as environmental pollution by catalysts. A reaction has been proposed.

For example, a method of oxidizing cumin aldehyde with hydrogen peroxide under alkaline conditions using an inorganic alkali salt such as sodium hydroxide or potassium hydroxide to obtain cumic acid (JP-A-63-264551), Or oxidizing unsaturated alicyclic or aromatic aldehydes with an organic peracid such as peracetic acid or perbenzoic acid in a basic organic solvent such as dimethylformamide or γ-picoline,
A method for synthesizing a carboxylic acid derived into a corresponding carboxylic acid (JP-A-3-157345). When oxidizing a corresponding aromatic aldehyde with an organic peracid in a water-immiscible organic solvent, the oxidation is carried out with an organic compound. A method (JP-A-7-2729) has been proposed in which the reaction is carried out in the presence of an alkali metal salt of an acid.

[0004] Further, vanillin is added to potassium hydroxide and sodium hydroxide mixed and melted at 180 ° C,
Method for synthesizing vanillic acid (ORGANIC SYNT)
HESES COLLECTION VOLUME
4, P974) are also known.

[0005]

Problems to be Solved by the Invention
The method disclosed in Japanese Patent No. 4551 has a high risk of a reaction using hydrogen peroxide and an inorganic alkali salt, and cannot be said to be an industrial production method. Also, JP-A-3-157345,
In the method disclosed in JP-A-7-2729, organic peracids such as peracetic acid and perbenzoic acid used for the oxidation reaction are expensive, and are not always easy to handle from the viewpoint of safety. It is not an industrially superior method.

[0006] ORGANIC SYNTHESES C
The method of synthesizing a carboxylic acid in a molten state of an alkali metal disclosed in OLECTIVE VOLUME 4, P974 is advantageous in terms of raw material and auxiliary raw material costs, but the reaction temperature is as severe as 180 to 190 ° C, and cannot be used with a general-purpose device. Also, the control of the reaction is difficult, and it cannot be said to be an industrially superior method.

An object of the present invention is to solve the above-mentioned problems of the prior art, to carry out the reaction safely under mild reaction conditions which are industrially advantageous, and to obtain a carbocyclic aromatic compound with high purity and high yield. Disclosed is a method for producing a carbocyclic aromatic carboxylic acid from which an aromatic carboxylic acid can be obtained.

[0008]

The process for producing a carbocyclic aromatic carboxylic acid according to the present invention comprises a method for producing a corresponding carboxylic acid by oxidizing a carbocyclic aromatic aldehyde. Aldehydes in a non-polar organic solvent,
It is characterized by heating in the presence of an alkali metal hydroxide. Thus, by heating a carbocyclic aromatic aldehyde in a non-polar organic solvent in the presence of an alkali metal hydroxide, the reaction can be carried out safely under mild reaction conditions, and high purity, Carbocyclic aromatic carboxylic acids can be obtained in high yield.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The carbocyclic aromatic aldehyde used as a raw material in the present invention can be easily obtained on the market, or can be obtained by a conventional method such as the Sommelet reaction of benzyl chloride. It can be easily synthesized and has at least one aldehyde group in the molecule.

A substituent may be introduced into the carbocyclic aromatic aldehyde as a raw material used in the present invention.
As the substituent, an alkyl group, an alkoxy group, a hydroxyl group,
Halogen and the like. The alkyl group is a lower alkyl group having 1 to 5 carbon atoms, and is preferably a methyl group, an ethyl group, a propyl group, an isopropyl group, or the like. The alkoxy group is a lower alkoxy group having 1 to 5 carbon atoms, and is preferably a methoxy group, an ethoxy group, or a propoxy group. The hydroxyl group may be esterified with an acetyl group or the like. Two or more of the above substituents may be introduced into the carbocyclic aromatic aldehyde as the raw material used in the present invention.

In the present invention, examples of the carbocyclic aromatic aldehyde as a raw material include cuminaldehyde, benzaldehyde, tolualdehyde, chlorobenzaldehyde, naphthaldehyde, hydroxybenzaldehyde, saltyl aldehyde, anthracene aldehyde and the like.

The non-polar organic solvent used in the present invention includes, for example, aromatic hydrocarbons such as benzene, toluene, xylene, methylnaphthalene and methylbiphenyl;
Alicyclic hydrocarbons such as cyclohexane and cyclopentane,
Examples thereof include aliphatic hydrocarbons such as pentane and heptane, halogenated hydrocarbons such as chlorobenzene and dichlorobenzene, and ethers such as diisopropyl ether and methylphenyl ether.

The amount of the nonpolar organic solvent to be used can be arbitrarily selected and is not particularly limited, but is usually preferably in the range of about 2 to 20 parts by weight per 1 part by weight of the aromatic aldehyde.

As the alkali metal hydroxide used in the present invention, sodium hydroxide, potassium hydroxide, lithium hydroxide, cesium hydroxide, rubidium hydroxide and the like can be used alone or as a mixture. Sodium hydroxide and potassium hydroxide which are easily available are preferred. More preferably, potassium hydroxide can lower the reaction temperature.

The amount of the alkali metal hydroxide used is 2 to 10 moles, preferably 3 to 7 moles, per mole of the carbocyclic aromatic aldehyde as the raw material. The amount of the alkali metal hydroxide used is 2 per carbocyclic aromatic aldehyde.
If the molar ratio is less than twice, the reaction is not completed. If the molar ratio exceeds 10 times, the operation becomes inconvenient and it is not economical.

The form of the alkali metal hydroxide used is
Although not particularly limited, in order to maintain a good dispersion state, it may be used by pulverizing in advance or pulverizing with a disperser or the like in a solvent.

The reaction temperature is not particularly specified, but the temperature at which the alkali metal hydroxide melts is not required.
The reaction can be performed at 80 ° C, preferably 60 to 120 ° C.

In the method for charging the carbocyclic aromatic aldehydes as the raw materials, the reaction is not hindered at all even if they are initially charged all at once, but the reaction takes place quickly, so that the amount of heat generated per hour increases. The temperature of the reaction solution may rise rapidly. Therefore, in order to control the reaction temperature, it is necessary to charge a nonpolar organic solvent and an alkali metal hydroxide to a reaction vessel, heat the reaction vessel to a predetermined temperature, and then sequentially charge the raw material carbocyclic aromatic aldehydes. desirable. At this time, when the carbocyclic aromatic aldehydes are dissolved in the non-polar organic solvent, it is preferable to continuously drop a solution in which the carbocyclic aromatic aldehydes are dissolved in the non-polar organic solvent from the viewpoint of operability. preferable.

The reaction time is about 0.5 to 5 hours,
If the temperature is appropriate, the reaction is completed in 0.5 to 2 hours.
The carbocyclic aromatic carboxylic acids generated at the end of the reaction become alkali metal salts and are dispersed as a slurry in the solvent. Therefore, the generated carbocyclic aromatic carboxylic acids can be separated by any method, for example, after completion of the reaction, water is added, the alkali metal salt of the carbocyclic aromatic carboxylic acid is dissolved and separated, and then the aqueous layer is subjected to acid precipitation. Or recover, or dissolve the alkali metal salt of carbocyclic aromatic carboxylic acid by adding water,
It is also possible to carry out acid precipitation before liquid separation, to extract and separate the carbocyclic aromatic carboxylic acid in the solvent layer, and to collect and recover the solvent. The recovered carbocyclic aromatic carboxylic acid is purified, if necessary, by a known method.

[0020]

EXAMPLES Example 1 Xylene 150 was placed in a 500-ml flask equipped with a stirrer.
g, 30 g (0.509 mol) of 95% pure potassium hydroxide and 12.2 g (0.102 mol) of p-tolualdehyde were heated to 100 ° C. with stirring, and stirring was continued for 2 hours. Reacted. Then, 200 g of water was added to the reaction solution.
After dissolving the formed potassium p-toluate, the mixture was allowed to stand for 30 minutes and separated, and the pH of the lower aqueous layer was adjusted to 2.0 by adding hydrochloric acid. The precipitated crystals were filtered, washed with water, and dried. This gave 13.7 g of p-toluic acid. This p-toluic acid was analyzed using a liquid chromatograph, and the purity by area percentage was determined. As a result, the purity of p-toluic acid was 99.6%, and the yield was 99 mol%.

Examples 2 to 6 The same operation as in Example 1 was carried out under the same conditions as in Example 1 except that xylene as the reaction solvent in Example 1 was replaced with another reaction solvent shown in Table 1. The purity and yield of p-toluic acid were determined. Table 1 shows the results.

[0022]

[Table 1]

Examples 7 to 13 The same operation as in Example 1 was carried out under the same conditions as in Example 1 except that the raw materials shown in Table 2 were used in place of p-tolualdehyde as the raw material of Example 1. Similarly, the purity and yield of the obtained carbocyclic aromatic carboxylic acid were determined. Table 2 shows the results.

[0024]

[Table 2]

Comparative Example A similar operation was carried out under the same conditions as in Example 1 except that the reaction solvent in Example 1 was changed from xylene to DMF, triethylene glycol or sulfolane. In each case, p-toluic acid was used. Hardly produced.

[0026]

According to the method for producing carbocyclic aromatic carboxylic acids of the present invention, an expensive oxidizing agent is not required, and the reaction can be carried out safely under mild reaction conditions. It is an industrially extremely effective method because a carbocyclic aromatic carboxylic acid can be obtained with high purity and high yield.

Claims (1)

[Claims] 1. A method for producing a corresponding carboxylic acid by oxidizing a carbocyclic aromatic aldehyde, wherein the carbocyclic aromatic aldehyde is heated in a nonpolar organic solvent in the presence of an alkali metal hydroxide. A method for producing a carbocyclic aromatic carboxylic acid, which comprises the steps of: