JPS63156746A - Production of alkyl-substituted aromatic carboxylic acids - Google Patents

Abstract

PURPOSE:To carboxylate the 4-position of an alkyl-substituted phenol and obtain the titled compound in high yield in a short time, by reacting potassium salt of an o-alkyl substituted phenol with CO2 in a hydrocarbon solvent at a high temperature. CONSTITUTION:Potassium salt of an alkyl-substituted phenol, e.g. potassium salt of cresol, etc., is reacted with carbon dioxide in a hydrocarbon solvent, preferably >=8C aliphatic hydrocarbon, aromatic hydrocarbon, kerosene, light oil, etc., at >=100 deg.C, preferably 180-250 deg.C to carboxylate the 4-position thereof and afford the aimed alkyl-substituted-4-hydroxy-1-carboxylic acids, e.g. 3- methyl-4-oxybenzoic acid, etc., useful as a raw material for agriculatural chemicals, medicines and polymers.

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a method for producing alkyl-substituted aromatic carboxylic acids. The above compounds are used as agricultural medicines and polymer raw materials.

Conventionally, a method for introducing a carboxylic acid group into the p-position using alkyl-substituted phenol as a raw material is a method in which a tetrahalogenated hydrocarbon is reacted in an aqueous alkali metal solution in the presence of cyclodextrin (Japanese Unexamined Patent Publication No. 6 O- 169438) and 2
．． Method for reacting sodium salt of 6-dimethylphenol in toluene solvent (Kobunshi Paper Collection vo It 33
, 1). 693 (1976)), a method for reacting 2,6-dialkylphenol having a branched or cyclic alkyl group in a mixture with a dipolar neutral solution (Japanese Patent Application Laid-open No. 1976-
40745) is known.

However, among these techniques, the method using cyclodextrin consumes tetrahalogenated hydrocarbons, and the method of reacting sodium salt in toluene takes a long reaction time. However, the problem is that the yield is low.

In addition, when using a dipolar neutral solution such as DMF, it is important to neutralize the raw phenol with an alkali and then dehydrate it to create an anhydrous salt, but it is difficult to separate the water and the solvent. be.

The inventors of the present invention,
In order to solve the above-mentioned problems, we have conducted extensive research and have completed the present invention.

That is, in the present invention, a potassium salt of phenol substituted with an alkyl group at the ortho position is prepared in a carbon-hydrogen solvent for 1. The present invention relates to a method for producing alkyl-substituted 4-hydroxy-1-carboxylic acids, which comprises reacting with carbon dioxide at 100°C or higher.

In carrying out the 4-position carboxylation of alkyl-substituted phenols, the Kolbe-Schmidt reaction proceeds extremely smoothly by forming a potassium salt of the alkyl-substituted phenol and reacting it with carbon dioxide in a hydrocarbon solvent at high temperatures. It was found that the target compound could be obtained in good yield.

Here, as the alkylphenol, the alkyl group is methyl, ethyl, propyl, butyl, pentyl, hexyl,
Heptyl, octyl, nonyl, decyl, dodecyl, etc., and the alkyl group may have a branched or cyclic structure, and in the case of a 2.6-substituted product, it may be a mixture of any of these groups. .

The method for producing the potassium salt of an alkyl-substituted phenol includes dissolving or suspending the alkyl-substituted phenol in water, or dissolving or suspending the alkyl-substituted phenol in the hydrocarbon solvent and neutralizing it with potassium hydroxide or the like. Although there is a method of distilling it off, it may be produced by any method.

The hydrocarbon used as the reaction solvent preferably has a boiling point of 120°C or higher, particularly 180°C to 400°C.

The hydrocarbons are preferably linear or branched or cyclic aliphatic hydrocarbons of 08 or more, aromatic hydrocarbons,
Polycyclic hydrocarbons, alkyl-substituted aromatic hydrocarbons, alkyl-substituted polycyclic hydrocarbons, or mixtures thereof, such as kerosene, gas oil, can be used.

As for the reaction conditions, the molar ratio of the potassium salt of the alkyl-substituted phenol to carbon dioxide is such that carbon dioxide is in excess of the theoretical reaction ratio. The reaction temperature is required to be 100°C to 400°C in order to proceed the reaction at a substantial rate, preferably 180°C to 250°C. The reaction time is closely related to the reaction temperature, ranging from 180°C to 250°C.
At ℃, the reaction is completed in about 10 minutes to 2 hours.

Stirring greatly affects the reaction. For this reason, the stirring blade must be capable of exerting sufficient stirring and shearing force, and equipment that promotes mixing and dispersion, such as a panfur, is effective.

This is thought to be because the potassium salt of the substituted phenol as a raw material can be finely dispersed, so that the reaction proceeds quickly.

During the reaction, it is better to have less water (eg, 1% or less, preferably 0.1% or less, by which side reactions can be reduced).

The ratio of the alkyl-substituted phenol potassium salt to the hydrocarbon solvent is preferably such that the potassium salt can be finely dispersed. Therefore, preferably 3 to 40%, particularly 5 to 20% is suitable.

castritis Hereinafter, it will be explained in more detail based on examples.

The reaction product was analyzed by high performance liquid chromatography (column 0DS-C+e, column length Loam, solvent acetonitrile/water = 20/80 to 80/20 gradient, -4 = detector UV 250 nm, 280 nm).

Example 1 700 g of diesel oil was placed in a 2 Il SUS 316 autoclave.
g of orthocresol was added under nitrogen purge.
Dissolve 2 g (1.5 mol). On the other hand, 797 g of 95% strength was dissolved in 200 g of water, thoroughly degassed, and then added to the orthocresol solution with stirring.

Orthocresol becomes a potassium salt and migrates to the aqueous layer. The reactor is heated and water is distilled off under normal pressure. 190
When the light oil distilled off at ℃ becomes clear, the water content is 0.0
A powder of potassium salt of cresol with a concentration of less than 5% and suitable for Kolbe-Schmidt reaction was obtained.

The reactor was cooled to 40°C and carbon dioxide was added at 5Kg/cn.
After 2 hours of absorption at 1G pressure, the reactor was heated to 230°C for 4 hours.
The temperature was raised for 0 minutes, stirred vigorously for 1 hour to carry out a rearrangement reaction, and then rapidly cooled to room temperature.

The reaction mass is obtained as a gray-brown slurry, so 2
! When dissolved in water, a water layer and a light oil layer were separated. When the water layer was neutralized with hydrochloric acid to pH 6.0, unreacted orthocresol was extracted into the light oil layer.

The aqueous layer was separated and acidified to pH 4.0 to precipitate and separate the produced oxycarboxylic acids, followed by drying to obtain a crude product. According to the above HLC analysis, 2-methyl-4-
Oxybenzoic acid, 14.8 minutes Orthocresol, 22
．． 3-methyl-2-oxybenzoic acid was detected at 6 minutes;
From the analytical values, the conversion rate of orthocresol was 57%, and the selectivity of 3-methyl-4-oxybenzoic acid was 81%.
Met.

The above crude product was extracted with hot water and the crystals obtained by cooling were as shown below.

Elemental analysis C(X) H(χ) analysis value
63.1 5.5 Calculated value 63.2 5.3 Melting point Analytical value 172-174.5"C literature value
174-175℃ Example 2 200m1 A autoclave (SLIS 304
1,2,4-trimethylbenzene 40g, 2.6
-Dissolve 12.2 g of xylenol. Potassium hydroxide (
When 5.9 g of 95% flakes) was dissolved in water Log and added to the above 2,6-xylenol layer and stirred, 2.6
-Xylenol migrates to the aqueous phase as a potassium salt.

The reactor is heated, water is azeotroped with trimethylbenzene, and water is separated off. Boiling point of trimethylbenzene 1'7
At 0°C, the cloudiness due to water in the distillation solvent disappears, and further 1
Refluxing was continued for an hour to obtain anhydrous potassium salt of 2,6-xylenol. The reactor was cooled to room temperature, and carbon dioxide was added at a rate of 20 ml/min at a pressure of 5 kg/c of nitrogen while stirring.
Aerated for an hour and allowed to absorb. Rapidly heat the reactor to 180°C,
After rapidly heating and stirring vigorously to carry out the reaction, water was added for 30 minutes.
It was rapidly cooled to ℃. The reaction mass is a slurry, containing 250% water
g was added to melt the solid, and the mixture was separated into an aqueous layer and a trimethylbenzene layer. The aqueous layer and trimethylbenzene layer were analyzed by HLC.

Dimethyl-4-2,6-xylethoxybenzoic acid aqueous layer 5.3 g 1.1 g organic layer
0.1 g 4.4 g This result is 2,6
-The conversion rate of xylenol was 55%, and the selectivity of dimethyl-4-oxybenzoic acid was 80.0%.

Comparative Example 1 This was the same as Example 2 except that the alkali was replaced with sodium hydroxide.

As a result, the conversion rate of 2,6-xylenol was 69%, the selectivity was 33%, and many unknown components were obtained.

Examples 3 to 4 Comparative Example 2 Example 2 was carried out by changing the solvent and reaction temperature as follows. The results are shown in Table-1.

Table 1 = 8 - Water was added to the reaction mass obtained in Example 3 to dissolve the slurry, the aqueous layer was separated, and hydrochloric acid was added to adjust the pH to 4.0 to precipitate dimethyl-4-oxybenzoic acid. . The crystals were separated by filtration and purified by recrystallization from a water-methanol system. The IR spectrum of the purified product matched the Aldrich standard spectrum 73-G.

Melting point Measured value: 219-222°C Literature value: 221-224°C Example 5 2,6-jet was added to Ikg of water containing 56g of potassium hydroxide.
206 g of er t-butylphenol and 1 h of light oil were added, and while stirring at 70°C, the liquid temperature was heated to 100°C to 220°C under normal pressure, and water was azeotropically distilled together with the light oil for dehydration. Water was separated from the distilled light oil, and the light oil component was returned to the reaction system. The azeotropic operation was carried out for 4 hours, and the water content in the reaction solution was 0.1%.
It decreased to below. The potassium salt of 2,6-di-tert-butylphenol was dispersed in suspension in light oil. Cool to 50°C and add 5 kg/c of carbon dioxide while stirring.
After absorbing at a pressure of J for 2 hours, the temperature was raised to 200° C. while stirring vigorously, and the mixture was reacted for 1 hour. After rapidly cooling the reaction mass, water was added and treated in the same manner as in Example 1, and the water layer and light oil layer were analyzed by liquid chromatography. 2,6-sheet
The conversion of tert-butylphenol was 55%, and the selectivity per converted 2,6-sheet tert-butylphenol was 80%. The potassium salt in the aqueous layer was precipitated with sulfuric acid and recovered as crystals from the aqueous solution. The crystals were dissolved by heating by adding methanol, and after adding water, they were cooled and recrystallized. The crystals obtained are white and mp 2
The temperature was 12-214.5°C.

By reacting a potassium salt of phenol substituted with an alkyl group at the ortho-position with carbon dioxide in a hydrocarbon solvent at 100°C or higher, carboxylation at the 4-position can be carried out in high yield and in a short time. This process can be carried out in a short period of time, and the carboxylic acids can be supplied to the market at low cost.

Claims (1)

[Claims] (1) A potassium salt of phenol substituted with an alkyl group at the ortho position is mixed with carbon dioxide at 100°C in a carbon hydrogen solvent.
Alkyl-substituted-4- characterized by reacting with the above
Method for producing hydroxy-1-carboxylic acids.