JPS63295531A - Production of beta-(3,5-dialkyl-4-hydroxyphenyl)propionic acid alkyl ester - Google Patents

Abstract

PURPOSE:To suppress side reaction and obtain the titled compound in high purity and yield, by maintaining a acrylic alkyl ester in a reaction system to a specific concentration when 2,6-dialkylphenol is reacted with the acrylic acid ester in the presence of a basic catalyst. CONSTITUTION:When the titled compound useful as an antioxidant or intermediate thereof is produced by reacting 2,6-dialkylphenol with acrylic acid alkyl ester in the presence of a basic catalyst, (i) 1mol. 2,6-dialkylphenol is reacted with 0.5-0.8mol. acrylic acid alkyl ester and then (ii) additional acrylic acid alkyl ester is added to the reaction system so that total amount of the acrylic acid ester in the reaction system is 0.9-1.5mol. based on the 1mol. 2,6- dialkylphenol used to suppress formation of a by-product expressed by the formula (R1-R3 are alkyl) and advantageously provide the aimed compound.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an improved process for producing β-(3,5-dialkyl-4-hydroxyphenyl)propionic acid alkyl esters.

[Problems to be solved by conventional technology and invention] β-
(3,5-Dialkyl-4-hydroxyphenyl)propionic acid alkyl esters are not only useful as antioxidants themselves, but also can be reacted with polyhydric alcohols or polyhydric amines to form high molecular weight antioxidants. It is useful as an intermediate for production, and is known to be obtained by reacting 2,6-dialkylphenol with an acrylic acid alkyl ester.

For example, Japanese Patent Publication No. 39-28324, Japanese Patent Publication No. 46-
No. 7933, JP-A-48-62731, JP-A-56-161350, etc. disclose that the target compound is produced by the reaction of 2,6-dialkylphenol and an acrylic acid derivative in the presence of a basic catalyst. It is stated that it can be obtained. However, the methods described in these publications have drawbacks such as low yields and the need for a large amount of reaction solvent.
It has become clear that a particularly serious problem is that a relatively large amount of by-products having the following formula (1) are produced.

p.

The by-product represented by the above formula (1) is reacted with polyhydric alcohol or polyhydric amine to produce a polymer when producing a high molecular weight antioxidant, so its content is
0.2% by weight or less based on the (3,5-dialkyl-4-hydroxyphenyl)propionic acid alkyl ester,
Preferably, it is necessary to set it to 0.1% by weight or less.

However, the methods described in each of the above publications contain about 0.3% by weight or more of the by-product represented by the above formula (1) even after vacuum distillation, and it is necessary to obtain a product with the desired purity. Precision distillation, recrystallization, and other operations are required, which are complicated and reduce yield.

[Means for Solving the Problems] The present inventors investigated a method for producing β-(3,5-dialkyl-4-hydroxyphenyl)propionic acid alkyl ester that does not have the above-mentioned drawbacks, and as a result, the inventors found that By-products are likely to be produced when a large amount of acrylic acid alkyl ester is present in the early stage of the reaction and the concentration of acrylic ester in the system is high, and less likely to occur when the concentration of acrylic ester is low. It has been found that by appropriately controlling the concentration of acrylic ester in the system, the production of the by-product represented by the above formula can be suppressed.

Based on the above findings, the present inventors have developed highly pure β-(3,
As a result of extensive research into a method for producing 5-dialkyl-4-hydroxyphenyl) propionic acid alkyl ester in high yield, we discovered that 2,6-dialkylphenol and acrylic acid alkyl ester were combined in the presence of a basic catalyst. When reacting to produce β-(3,5-dialkyl-4-hydroxyphenyl)propionic acid alkyl ester, a) 0 per mole of 2,6-dialkylphenol.
．． 5 to 0.8 moles of acrylic acid alkyl ester are reacted, and then additional acrylic acid alkyl ester is added so that the total amount of acrylic acid alkyl ester in the reaction system is equal to the amount of acrylic acid alkyl ester used.
It has been discovered that a highly purified target product can be produced in high yield by reacting in an amount of 0.9 to 1.5 moles per mole of 6-dialkylphenol, and the present invention has been achieved based on this finding.

Hereinafter, the present invention having the above-mentioned summary will be explained in detail.

The 2,6-dialkylphenol used in the present invention includes 2,6-dimethylphenol, 2,6-diituprobylphenol, 2,6-di-tert-butylphenol,
2.6-di-tert-amylphenol, 2.6-di-tert-octylphenol, 2-tert-butyl-6-methylphenol, 2-tert-butyl-6-ethylphenol, 2-tert-butyl-6- Examples include ituprobilphenol, and 2,6-di-tert-butylphenol and 2-tert-butyl-6-methylphenol are particularly suitable.

Examples of the acrylic acid alkyl ester used in the present invention include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl,
Examples include undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl ester and the like.

The ratio of 2.6-dialkylphenol to acrylic acid alkyl ester is 2,6-dialkylphenol and acrylic acid alkyl ester in the initial stage of the reaction.
It is necessary that the amount of alkyl acrylate is 0.5 to 0.8 mole per mole of 6-dialkylphenol, and if the alkyl acrylate is less than 0.5 mole, the reaction progresses significantly; Also, 0.8
If the amount is more than 2,6 moles, the amount of the by-product represented by the formula (I) will increase, which is undesirable. In addition, the total amount of acrylic alkyl ester including the added acrylic alkyl ester is 2,6-di The amount ranges from 0.9 to 1.5 mol per mol of alkylphenol, and 0.9
If the amount is less than 1 mol, the yield of the target product will decrease, and if it is 1.5 mol or more, the amount of the by-product represented by the formula (I) will increase, which is not preferable.

As the basic catalyst used in the present invention, conventionally known basic catalysts can be used.

Catalysts that can be used include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, alkali metal alkoxides such as sodium methoxide, sodium ethoxide, and potassium tert-butoxide, alkali metal amides such as lithium amide, and sodium hydride. , alkali metal hydrides such as lithium hydride, alkalis such as sodium phenoxide, potassium phenoxide, potassium-2,6-di-tert-butyl phenoxide, potassium-2-tert-butyl-6-methylphenoxide, etc. Examples include metal phenoxytes.

The amount of these catalysts used is about 0.1 mol% to about 20 mol%, preferably 3 to 15 mol%, based on the 2,6-dialkylphenol used, and the catalyst is used in the initial stage of the reaction. You can add the entire amount with or,
Although it can be added in portions at the initial stage of the reaction and when adding the acrylic acid alkyl ester, it is preferable to add in portions to prevent deactivation of the catalyst.

The reaction time varies depending on the types of raw materials and catalysts, their quantitative ratios, reaction temperature, etc., but the reaction in step 1) proceeds quickly, and generally the conversion rate of acrylic acid alkyl ester is 90% or more in about 30 minutes to 3 hours. Therefore, it is preferable to add additional acrylic acid alkyl ester at this stage and carry out the reaction in the step).The reaction in the step) generally takes about 3 to 10 hours to complete the reaction. It takes.

The reaction temperature is appropriately selected from the range of room temperature to about 200°C, but it is usually preferably carried out in the range of 70 to 150°C.Also, this reaction is carried out under normal pressure or naturally occurring pressure. , if desired, can also be carried out under reduced pressure or under increased pressure.

Since the reaction proceeds satisfactorily even without a solvent, it is not necessary to use a solvent, but the reaction can be carried out in the presence of a solvent if desired. As a solvent, ether type, aliphatic dialkylamide type, aromatic and aliphatic nitrile type, hydrocarbon type, dialkyl sulfoxide type, ester type, ketone type,
Those within the range of chlorine compound-based calculation methods may be used. The amount of solvent used can vary widely, from a small amount merely sufficient to dissolve the solute, to an amount sufficient to inhibit rapid reaction.

If the catalyst is removed and distilled after the reaction is completed, the target compound can be obtained in a substantially pure form without any further purification treatment such as recrystallization.

As mentioned above, the β-(3,5-dialkyl-4-hydroxyphenyl)propionic acid alkyl ester produced by the method of the present invention can be used for materials that are susceptible to deterioration, such as hydrocarbon oils, lubricating oils, other polypropylene, It is useful not only as an antioxidant for plastic materials such as polyethylene, natural rubber, and synthetic rubber, but also as an intermediate for various derivatives.

〔Example〕

EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited by these Examples.

Example-1 206g (1 mol) of 2,6-di-tert-butylphenol
and 4.1 g (0,075 mol) of sodium methoxide were taken and heated to 90 to 100°C. Add 51.6 g (0.6 mol) of methyl acrylate to this, and
Stirred at 100°C for 30 minutes.

Sodium methoxide 1.5g (0,028mol)
and 51.6 g (0.6 mol) of methyl acrylate were added thereto, and the mixture was further stirred at 90-100°C for 6 hours. After cooling,
Neutralization with acetic acid gave a crude product.

As a result of analyzing the crude product by gas chromatography, it was found that dimethyl 2-(3,5-di-tert-butyl-4-hydroxybenzyl)glutarate (Rr-To- 3-butyl, R-conimethyl)
The content of the target product (β-(3,5-di-tert-butyl-4
-hydroxyphenyl)propionate) was 0.3%.

By vacuum distilling this crude product, the boiling point is 200~
As a fraction of 204℃/20 snug, 277g (
The desired product was obtained with a yield of 95%.

As a result of analyzing this purified product by gas chromatography, the content of the by-product was 0.08% based on the target product.

Example-2 206 g (1 mol) of 2,6-di-tert-butylphenol and 8.4 g (0,075 mol) of potassium tert-butoxide were taken and heated to 90-100°C. Add 51.6 g (0.6 mol) of methyl acrylate to this, and add 90 to 1
Stirred at 00°C for 30 minutes.

Potassium tert-butoxide 1.7g (0,015 mol)
and 51.6 g (0.6 mol) of methyl acrylate were added, and the mixture was further stirred at 90 to 100°C for 6 hours. After cooling, it was neutralized with acetic acid to obtain a crude product.

As a result of analyzing the crude product by gas chromatography, it was found that dimethyl 2-(3,5-di-tert-butyl-4-hydroxybenzyl)glutarate (R1-R1-dimethyl 3-butyl, US-methyl)
The content of the target product (β-(3,5-di-tert-butyl-4
-hydroxyphenyl)propionate) was 0.3%.

By vacuum distilling this crude product, the boiling point is 200~
280g as a fraction of 204℃/20ms+Hg
The desired product was obtained (yield 96%).

As a result of analyzing this purified product by gas chromatography, the content of the by-product of the above formula was 0.09% with respect to the target product.
Met.

Example-3 2-t-butyl-6-methylphenol 164g (1
Take 7.1 g (0,035 mol) of potassium-2-t-butyl-6-methylphenoxide and add 120
At ~140°C 51.6 g (0.6 mol) of methyl acrylate were added and stirred at 120-140°C for 30 minutes.

Add 3.0 g (0.015 mol) of potassium-2-t-butyl-6-methylphenoxide and 51.6 g (0.6 mol) of methyl acrylate, and heat at 120-140°C.
The mixture was further stirred for 3 hours. After cooling, it was neutralized with acetic acid to obtain a crude product.

As a result of analyzing the crude product by gas chromatography, it was found that dimethyl 2-(3-tert-butyl-4-hydroxy-5-methylbenzyl)glutarate (R8- Tertiary butyl, R atmosphere-R,-
The content of β-(3-tert-butyl-4
-hydroxy-5-methylphenyl)propionate) was 0.4%.

This crude product was vacuum distilled to obtain the target product with a boiling point of 164-b%).

As a result of analyzing this purified product by gas chromatography, the content of the by-product was 0.09% based on the target product.

Comparative Example 2.6 1-di-tert-butylphenol 206g (1 mol)
and 10.1 g (0.09 mol) of potassium tert-butoxide were taken and heated to 90-100°C. Add 103.2 g (1.2 mol) of methyl acrylate to this, and
The mixture was stirred at 100°C for 6 hours and 30 minutes. After cooling, it was neutralized with acetic acid to obtain a crude product.

As a result of analyzing the crude product by gas chromatography, it was found that dimethyl 2-(3,5-di-tert-butyl-4-hydroxybenzyl)glutarate (in the by-product represented by the above formula (1), Fh-Rt = 3-butyl, R5-methyl)
The content of the target product (β-(3,5-di-tert-butyl-4
-hydroxyphenyl)propionate).

By vacuum distilling this crude product, the boiling point is 200~
266 g (yield 91%) of the target product was obtained as a 204° C./20 μ-Hg fraction.

As a result of analyzing this purified product by gas chromatography, the content of the by-product of the above formula was 0.42% with respect to the target product.
Met.

(Effects of the Invention) According to the method of the present invention, the amount of the by-product represented by the above formula (1) is extremely small, and can be reduced to about 0.1%, which is sufficiently satisfactory only by vacuum distillation. - When using the conventional method, a large amount of the by-product represented by the above formula (I) was produced, and it was not possible to reduce the by-product to the required 0.2% or less.

Furthermore, the yield of the target product by the method of the present invention is superior to that by conventional methods, and it is clear that the method of the present invention is extremely superior to conventional methods.

Claims (1)

[Claims] β-(3,
When producing a 5-dialkyl-4-hydroxyphenyl) propionic acid alkyl ester, a) 0.5 to 0.8 per mole of 2,6-dialkylphenol.
mol of acrylic acid alkyl ester are reacted, and then b) additional acrylic acid alkyl ester is added so that the total amount of acrylic acid alkyl ester in the reaction system is equal to the amount of 2,
Production of β-(3,5-dialkyl-4-hydroxyphenyl)propionic acid alkyl ester, characterized in that the reaction is carried out in an amount of 0.9 to 1.5 mol per mol of 6-dialkylphenol. Method