RU2239627C2 - Method for preparing beta-(4-hydroxy-3,5-di-tertiary-butylphenyl)-propionic acid methyl ester - Google Patents

Abstract

FIELD: organic chemistry, chemical technology.

SUBSTANCE: invention relates to the improved method for preparing β-(4-hydroxy-3,5-di-tert.-butylphenyl)-propionic acid methyl ester that is an intermediate compound in synthesis of highly effective thermo- and light-stabilizing agents. Method involves interaction of 2,6-di-tert.-butylphenol with methacrylate in the mole ratio = 1.0:(1.0-1.1), at temperature 90-145^oC, in presence of catalytic complex comprising a mixture of sodium 2,6-di-tert.-phenolate and 2,6-di-tert.-butylphenol. Method involves using catalytic complex comprising additionally sodium methylate and a mixture of sodium 2,4-di-tert.-butylphenolate and sodium 2-tert.-butylphenolate in the following ratio of components, wt.-%: sodium 2,6-di-tert.-butylphenolate, 0.8-8.5; sodium methylate, 0.01-0.9; mixture of sodium 2,4-di-tert.-butylphenolate and sodium 2-tert.-butylphenolate, 0.005-0.5; 2,6-di-tert.-butylphenol, the balance, up to 100. Indicated alkaline components of catalytic complex are used in the amount 1.0-10.0 mole% of the amount of 2,6-di-tert.-butylphenol as measured for the sum of sodium 2,6-di-tert.-butylphenolate, sodium methylate and a mixture of sodium 2,4-di-tert.-butylphenolate and sodium 2-tert.-butylphenolate with acidifying the reaction medium and isolation of the end product. Method provides preparing the qualitative product with low amount of formed by-side products and retaining high yield of β-(4-hydroxy-3,5-di-tert.-butylphenyl)-propionic acid.

EFFECT: improved preparing method.

1 tbl, 9 ex

Description

The invention relates to organic synthesis, and in particular to a method for producing β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid methyl ester, which is an intermediate in the synthesis of highly effective thermal and light stabilizers.

Known methods for producing methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid by condensation of 2,6-di-tert-butylphenol (2,6-diTBP) with methyl acrylic acid ester (methyl acrylate) in the presence of alcoholates [US Patent 3,364,250, IPC C 07 C 69/732, 1965] and alkali metal hydroxides as catalysts [Japanese Patent 1611350, IPC C 07 C 69/732, 1966]. The yields of the target product reach 96%.

A known method of producing methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid, according to which in order to reduce the formation of by-products, methyl acrylate is added to phenol in the presence of an alkaline catalyst in or without aliphatic alcohol, or in a bipolar solvent medium [US Patent 4,228,297, IPC C 07 C 69/732, 1979]. The yield of ether is 84-87%.

A known method of producing methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid by alkylation of 2,6-diTBF with methyl acrylate (molar ratio 1: 1-1.15) at a temperature of 90-150 ° C in the presence of a basic catalyst consisting of 4- (β-methylcarboxyethyl) -2,6-di-tert-butylphenolate sodium, 2,6-di-tert-butylphenolate potassium and 2,6-diTBP [USSR AS 1685919, IPC C 07 C 69/732, 1989].

The yield of the target product reaches 99% with a selectivity of 99.8%.

The closest technical solution is a method for producing methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid by alkylation of 2,6-diTBP with methyl acrylate at a temperature of 90-150 °, molar ratio of 2,6-diTBP : methyl acrylate 1: 1-1.1 using the main catalyst, the following composition, wt.%:

Sodium 2,6-di-tert-butylphenolate 1.4-11.0

β- (4-Hydroxy-3,5-di-tert-

butylphenyl) sodium propionate 0.4-3.0

2,6-diTBP 86.0-98.2

Alkaline components are used in an amount of 1.5-13% (mol.) From 2,6-diTBP in terms of the amount of 2,6-di-tert-butylphenolate sodium and sodium salt β- (4-hydroxy-3,5-di tert-butylphenyl) propionic acid.

The disadvantages of the above methods include the formation of a by-product of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid, the difficulty of obtaining a multicomponent catalyst of a given composition, which involves the preliminary preparation of the components of the catalytic system and complex analytical control at the stage of preparation of the catalyst, as well as a yellow cream color of the target product obtained by the prototype, which ensures the presence in the target product of the sodium salt β- (4-hydroxy-3,5-di-tert- butylphenyl) -propionic acid, which is a by-product of the reaction.

The technical problem, the solution of which is proposed in the present invention, is to develop a method for producing methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid, characterized by a low number of by-products formed and an improved quality of the target product, while maintaining a high yield of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid methyl ester.

The claimed technical result is achieved by the fact that the process of obtaining methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid by alkylation of 2,6-diTBF with methyl acrylate at elevated temperatures (90-145 ° C), molar the ratio of phenol: methyl acrylate 1.0: 1.0-1.1 is carried out using a catalytic complex containing, in addition to 2,6-diTBP, 2,6-di-tert-butylphenolate sodium sodium methylate and a mixture of 2,4-di-tert sodium butyl phenolate and sodium 2-tert-butyl phenolate in the following ratio, wt.%:

Sodium 2,6-di-tert-butylphenolate 0.8-8.5

Sodium Methylate 0.01-0.9

A mixture of 2,4-di-tert-butylphenolate

sodium and

Sodium 2-tert-butylphenolate 0.005-0.5

2,6-di-tert-butylphenol The rest is up to 100

Alkaline components are used in an amount of 1.0-10.0% (mol.) From 2,6-diTBP, calculated on the amount of 2,6-di-tert-butylphenolate sodium, sodium methylate and a mixture of 2,4-di-tert- sodium butyl phenolate and sodium 2-tert-butyl phenolate.

The catalyst is prepared either by mixing individual sodium 2,6-di-tert-butylphenolate, sodium 2,4-di-tert-butylphenolate, sodium 2-tert-butylphenolate and sodium methylate with 2,6-diTBP, or obtained by heating methanol, hydroxide sodium, a mixture of 2,4-di-tert-butylphenol and 2-di-tert-butylphenol with 2,6-diTBP in an inert gas stream at a temperature of 100-120 ° C for 40-60 minutes with distillation of methanol and water.

Methanol reacts with sodium alkali to form sodium methylate in up to 45% yield. Next, sodium methylate and unreacted with methanol sodium alkali reacts with a mixture of 2,4-di-tert-butylphenol and 2-tert-butylphenol having a higher acidity than 2,6-diTBP to form the corresponding sodium phenolates. Lastly, the interaction of 2,6-diTBP with alkali occurs.

It turned out to be unexpected that during the preparation of the catalytic complex, sodium alkali interacts not only with 2,6-diTBP, but also with a solvent (methyl alcohol), which has a higher acidity compared with 2,6-diTBP, with the formation of sodium methylate. In turn, sodium methylate is a more basic catalyst than sodium 2,6-di-tert-butylphenolate.

The addition of a mixture of 2,4-di-tert-and 2-tert-butylphenol in the amount of 0.05-0.5 wt.% By weight of 2,6-diTBP during the preparation of the catalyst provides the formation of a catalytic complex having another main function, allowing go deeper into the alkylation process and accelerate it.

In addition, the exclusion from the composition of the catalyst of the sodium salt of β- (4-hydroxy-3,5-di-tert-butylphenyl) -propionic acid (see prototype) eliminates the formation of a by-product of β- (4-hydroxy-3,5- di-tert-butylphenyl) -propionic acid and improve the color of the target product.

The method of producing methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid is as follows.

To prepare the catalytic complex, a solvent (methanol) and sodium alkali are charged into a three-necked flask equipped with a reflux condenser, a nitrogen outlet and a dropping funnel. They include heating and stirring. After complete dissolution of the alkali, 2,6-diTBP is charged, a mixture of 2,4-di-tert-and 2-tert-butylphenol in an amount of 0.005-0.5% by weight of 2,6-diTBP. Next, the reaction mixture is stirred at a temperature of 90-120 ° C for 60-90 minutes, after which the solvent and the water liberated during the reaction are distilled off under vacuum.

A calculated amount of methyl acrylate is added to the catalyst thus prepared. The reaction is carried out for 40-70 minutes with stirring and a temperature of 90-145 ° C.

Then the reaction mixture is acidified with hydrochloric or phosphoric acid, the lower aqueous layer is drained. Β- (4-hydroxy-3,5-di-tert-butylphenyl) -propionic acid methyl ester is isolated from the upper organic layer by treating the reaction mixture with aqueous methyl alcohol, cooled to 10-12 ° C, filtered, dried, or carried out by distillation under vacuum at a temperature of 150 ° C.

To carry out the synthesis, the starting reagents must meet the following requirements:

methanol - GOST 6995-77,

2,6-diTBF - TU-38.103378-86,

sodium hydroxide - GOST 432877,

metal acrylate - TU-6-09-08-156-85.

In addition, for this synthesis, you can use 2,6-diTBP-rectified, containing impurities of 2,4-di-tert-butylphenol and 2-tert-butylphenol.

The essence of the method and industrial applicability is confirmed by the following examples.

Example 1

To prepare the catalytic complex, a three-necked flask equipped with a stirrer and reflux condenser was charged with 102 g (0.5 mol) of 2,6-diTBP containing 0.13 g of a mixture of 2,4-di-tert-and 2-tert-butylphenol and methanol solution of alkali (NaOH - 3.2 g, CH ₃ OH - 50 ml) with a supply of nitrogen. The mixture is heated to 100 ° C and continuously stirred for 60-65 minutes. Then methanol and the water liberated during the reaction are distilled off, and the residue is dried under vacuum for 30 minutes.

The result is a catalytic complex of the following composition, wt.%:

2,5-di-tert-butylphenolate sodium 2.5

Sodium Methylate 0.6

A mixture of 2,4-di-tert-butylphenolate

sodium and

Sodium 2-tert-butylphenolate 0.1

2,6-diTBF The rest is up to 100

45 ml (0.5 mol) of methyl acrylate are metered into the obtained catalytic complex for 10-15 minutes with constant stirring, without allowing the temperature of the reaction mixture to rise above 145 ° C. Exceeding the temperature of the mixture above 145 ° C leads to intense gum formation. 40-45 minutes after dosing (the residual content of 2,6-diTBP in the reaction mixture is 0.5% liquid chromatography DZ-205 with a UV detector (d = 254 nm), a column 15 cm long, eluent hexane: isopropanol (9: 1), elution rate 0.6 ml / min) distilled off excess methacrylate.

Next, the reaction mixture is acidified with hydrochloric or phosphoric acid, the aqueous layer is drained. 200 ml of aqueous methanol (1: 9 by volume) are added to the organic layer, chilled to 10-12 ° C, the precipitated crystals are filtered, or the reaction mass after draining the water layer is distilled off under vacuum at 150 ° C and a pressure of 133 Pa. 142.65 g of the expected product are obtained. 1.1 g of the expected product is additionally recovered from the mother liquor. The yield of the target product is 98.5%.

According to example 2, the preparation of the catalyst complex is carried out by mixing individual components.

Example 2

6.0 g of sodium 2,6-di-tert-butylphenolate, 0.45 g of a mixture of sodium 2,4-di-tert-butylphenolate and sodium 2-tert-butylphenolate, 1.0 g of sodium methylate and 92.55 g are charged into the autoclave 2,6-diTBP. The mixture is stirred and metered through a metering valve 38.5 g of methacrylate at a temperature of 120 ° C. Next, the temperature was raised to 140 ° C and the mixture was stirred for another 40-45 minutes until 2,6-diTBP was fully activated. Excess methacrylate is distilled off.

The reaction mixture is acidified with hydrochloric or phosphoric acid, the aqueous layer containing sodium salt is drained. 180 ml of aqueous methanol (1: 9 by volume) are poured to the reaction mixture, cooled, filtered. 129.5 g of the expected product are obtained. The yield is 99.0%.

The results of other syntheses and the compositions of the catalyst complexes are shown in the table, the syntheses were carried out analogously to examples 1, 2.

Thus, the above examples show that under the claimed conditions the process selectivity is 98.5-99.8%, the product yield reaches 94.5-99.5%, the optical density of the target product in toluene, determined on KFK-2-UHL 4.2 by a known method, is in the range from 0.05-0.06 units for each example, which corresponds to a white product.

At temperatures below the claimed process proceeds with a low yield. At temperatures higher than those declared, intense gum formation is observed, and the quality of the product is deteriorated in color.

At concentrations of sodium methylate and a mixture of sodium 2,4-di-tert-butylphenolate with sodium 2-tert-butylphenolate below the declared limits, the reaction rate and yield of the target product are reduced, and at concentrations above the declared limits, there is a decrease in selectivity and the presence of by-product alkyl phenols in the target product .

Claims (1)

The method of obtaining methyl ester of β- (4-hydroxy-3,5-di-tert-butylphenyl) propionic acid by the interaction of 2,6-di-tert-butylphenol with methacrylate in a molar ratio of 1.0: 1.0-1.1 , at a temperature of 90-145 ⁰ C in the presence of a catalytic complex containing a mixture of 2,6-di-tert-butylphenolate and 2,6-di-tert-butylphenol, characterized in that they use a catalytic complex, additionally containing sodium methylate and a mixture Sodium 2,4-di-tert-butylphenolate and sodium 2-tert-butylphenolate in the following ratio, wt.%: Sodium 2,6-di-tert-butylphenolate 0.8-8.5 Sodium Methylate 0.01-0.9 A mixture of sodium 2,4-di-tert-butylphenolate and sodium 2-tert-butylphenolate 0.005-0.5 2,6-di-tert-butylphenol Up to 100 while these alkaline components of the catalytic complex are used in an amount of 1.0-10.0 mol.% of 2,6-di-tert-butylphenol in terms of the amount of 2,6-di-tert-butylphenolate sodium, sodium methylate and mixture 2 , 4-di-tert-butylphenolate sodium and 2-tert-butylphenolate sodium with acidification of the reaction medium and the selection of the target product.