CH632734A5 - Process for the preparation of bis-(3',5'-di-tert.-butyl-4'-hydroxy-phenyl)-alkylcarboxylic acid esters - Google Patents

Description

The present invention now relates to an improved process for the preparation of bis (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) alkyl carboxylic acid esters which does not have the disadvantages mentioned and in high yields to give uniform products leads and thus makes economic production of the compounds serving as antioxidants for plastics possible in the first place.

This process for the preparation of bis (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) alkyl carboxylic acid esters of the general formula I

20th

25th

(ch2)

n

- coor (i)

in which n is an integer from 1 to 4 and R is an alkyl group having 1 to 18 carbon atoms, is characterized in that bis- (3'-tert-butyl-4'-hydroxy-phenyl) alkylcarbon -acid esters of the formula II

h-3c

- coor (ii)

in which n and R have the meaning given above, in a liquid aromatic hydrocarbon as solvent and in the presence of p-toluenesulfonic acid as a catalyst with isobutene at 40 to 90 ° C.

The method of operation according to the invention has a number of essential advantages over that described in the prior art. Thus, in addition to the fact that o-tert-butylphenolcarboxylic acid esters can be prepared easily and purely, it should be noted that it is possible to introduce the two missing isobutyl groups per mole of ester using the equivalent amount of isobutene, while, according to the prior art, approximately 2 to 3 times the theoretically required amount of isobutene is used. In addition to the economic importance of low isobutene consumption, a reaction product is also obtained according to the invention which is hardly contaminated with polyisobutene, a circumstance which considerably simplifies and simplifies the cleaning of the crude process end product.

Further advantages are short reaction times of 5 to 8 hours, the insensitivity of the alkylation reaction to temperature fluctuations and the possibility of being able to remove and recover the alkylation catalyst from the reaction mixture in a simple manner.

The bis- (3'-tert.-butyl.-4'-hydroxy-phenyl) alkylcarboxylic acid esters of the formula (II) to be alkylated according to the invention are easily accessible, for example by condensation of ketocarboxylic acid esters with o-tert.-butylphenol according to the Information from DE-AS 1 953 332, or according to O.Mauz in Liebigs Ann. Chem. 1974 (3), pages 345-351.

Liquid aromatic hydrocarbons which are suitable as solvents and which are used in an amount which corresponds to 0.1 to 10, preferably 0.8 to 1.5 times the weight of the starting product of the formula (II) are chlorobenzene, nitrobenzene, Benzene, preferably alkyl benzenes such as xylene, mesitylene, toluene, cumene and in particular ethylbenzene.

The p-toluenesulfonic acid serving as catalyst is used in an amount of 0.01 to 0.2, preferably 0.05 to 0.15 and in particular 0.09 to 0.11 parts by weight, based on the weight of the starting material of the formula (II) used.

The alkylation can be carried out at temperatures between 40 and 90, preferably 45 and 80 ° C. The highest yields are obtained at about 55 to 70 ° C. The reaction times are generally in the range from about 5 to 8 hours.

Only the theoretically required amounts, i.e. per mole of starting compound (II) 2 moles, be-50 required; in practice, 2.01 to 2.1 mol is generally used.

The process is carried out in detail so that the isobutene is passed into the reaction mixture of ester to be alkylated, solvent 55 and catalyst, which is kept at the reaction temperature, with vigorous stirring, in accordance with the rate of absorption. If necessary, work can also be carried out under pressure. When the calculated amount has been used, extraction is carried out with water to remove the catalyst. After the solvent has been distilled off, the crude process product, which is optionally recrystallized, is obtained from the organic phase. The aqueous phase containing the catalyst can be worked up to recover it by - if necessary after purification by filtration over an adsorbing substance such as coal, silica gel or the like - evaporating it to dryness. The yield is 90% and more of the catalyst weight originally used.

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The following examples are intended to illustrate the invention:

example 1

3,3-bis (3 ', 5'-di-tert-butyl-4'-hydroxy-phenyl) butanoic acid ethyl ester

OH

OH

In a mixture of 600 g of 3,3-bis- (3'-tert-butyl-4'-hydroxy-phenyl) butanoic acid ethyl ester, prepared according to the specifications of DE-AS 1 953 332, and 700 g of ethylbenzene is in the presence 60 g of p-toluenesulfonic acid at 65 to 70 ° C slowly introduced isobutene with vigorous stirring. After 5 hours, 165 g, i.e. 1% by weight more than the amount calculated for the per-butylation.

Now the reaction mixture is diluted with 1,500 ml of ethylbenzene and extracted 4 times with 100 ml of distilled water to remove the catalyst. The aqueous phases are collected in order to later recover the catalyst from them.

The organic phase is shaken with 50 ml of strongly dilute sodium hydroxide solution to remove the last catalyst residues (the washing water is discarded), whereupon the solvent is removed by distillation and the residue is recrystallized from heptane.

Yield: 564 g of a product melting at 113.2 ° C. (74.5% of theory)

C34H52O4 (MG 524)

calc .: C 78.0 H 9.9%

found: C 78.1 H 10.2%

To recover the majority of the p-toluenesulfonic acid, the combined washing water is boiled with a little activated carbon, filtered and evaporated to dryness. 53 g of p-toluenesulfonic acid monohydrate melting at about 102 ° C. are obtained, which can be reused in a further alkylation batch without further purification.

Example 2

3,3-bis- (3 ', 5'-di-tert-butyl-4 / -hydroxy-phenyl) -butanoic acid methyl ester The corresponding methyl ester was prepared in an analogous manner. It has a melting point of 177 to 181 ° C. C33H5O04 (MG510)

calc .: C 77.6 H 9.8%

found: C 77.3 H 10.0%

Example 3

3,3-bis- (3 ', 5'-di-tert-butyl-4'-hydroxy-phenyl) -butanoic acid 426 g of 3,3-bis- (3'-tert-butyl-4'-hydroxy) -phenyl) -butanoic acid isopropyl ester (mp. 176 ° C), prepared according to the specifications of DE-AS 1 953 332, Example 1, are in 500 ml of ethylbenzene in the presence of 40 g of p-toluenesulfonic acid with vigorous stirring at 67 ° C. Reacted for 5 hours with isobutene. During this time, the batch increased by 115 g in weight. The reaction mixture is diluted with 11 ethylbenzene and freed from the p-toluenesulfonic acid by repeated shaking with water until the wash water becomes neutral. After the solvent has been distilled off, the residue is recrystallized from toluene.

Yield: 502 g (93% of theory) one at 124 ° C

melting product.

C35H55O4 (MG 539)

calc .: C 77.9 H 10.2%

found: C 77.8 H 10.2%

Example 4

3,3-bis- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) -butanoic acid butyl ester In an analogous manner, the n-butyl derivative from the 3,3-bis- (3'-tert .-Butyl-4'-hydroxyphenyl) -butanoic acid butyl ester (mp. 147 ° C) accessible in 72% yield. Melting point 148 ° C.

C36HS704 (MG 553)

calc .: C 78.1 H 10.3%

found: C 77.8 H 10.3%

Example 5

3,3-bis- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) -butanoic acid n-octyl ester 99.2 g 3,3-bis- (3'-tert-butyl- 4'-hydroxyphenyl) butanoic acid octyl ester are treated with isobutene gas in 125 ml of toluene in the presence of 10 g of p-toluenesulfonic acid according to Example 1 and, after dilution with 250 ml of toluene, the p-toluenesulfonic acid is removed by shaking with water. After the solvent has been stripped off, the crude product is taken up in isopropanol and crystallized by adding heptane.

440 g (73% of theory) of the desired compound of mp 69 ° C. are obtained.

C40H64O4 (MG 608)

calc .: C 79.6 H 10.5%

found: C 79.0 H 11.8%

Example 6

3,3-bis- (3 ', 5'-di-tert-butyl-4'-hydroxy-phenyl) -butanoic acid n-octadecyl ester According to the procedure given in Example 1, 123 g of 3,3-bis- ( 3'-tert-butyl-4'-hydroxy-phenyl) -butanoic acid octadecyl ester (mp. 109 ° C.) in the manner described in Example 1 with isobutene. After recrystallization from toluene / heptane, 104 g (69% of theory) of the desired compound melting at 42 ° C. are obtained.

CS0H84O4 (MG 748)

calc .: C 80.2 H 11.2%

found: C 80.2 H 11.5%

Example 7

5,5-bis- (3 ', 5, -di-tert-butyl-4 / -hydroxy-phenyl) -hexanoic acid methyl ester 85.2 g of 5,5-bis- (3'-tert-butyl-4') -hydroxy-phenyl) -hexanoic acid methyl ester (mp. 64.5 ° C), produced by condensation of 5-oxo-hexanoic acid methyl ester with 2 mol of o-tert-butylphenol, are in 125 ml of toluene in the presence of 8 g of p- Toluene sulfonic acid reacted for 5 hours at 70 ° C with vigorous stirring with the calculated amount of isobutene gas. The mixture is then diluted with 250 ml of toluene and washed with water several times until the reaction is neutral. The residue that remains after the solvent has been distilled off is crystallized from isopropanol.

Yield: 79 g (73% of theory) of a crystalline product with a melting point of 142 ° C.

C35H5404 (MG538)

calc .: C 78.1 H 10.0%

found: C 78.1 H 10.3%

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Claims (2)

632 734 2nd PATENT CLAIMS 1. Process for the preparation of bis (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) alkyl carboxylic acid esters of the general formula I OH 10th H3C - C - (CH2) n - C00R C1) H3C - C - (CH2) n - COOR (Ii) in which n is an integer from 1 to 4 and R is an alkyl group having 1 to 18 carbon atoms, characterized in that bis (3'-tert-butyl-4, -hydroxyphenyl) alkylcarbonate of formula II in which n and R have the meaning given above, in a liquid aromatic hydrocarbon as solvent and in the presence of p-toluenesulfonic acid as a catalyst with isobutene at 40 to 90 ° C. 2. The method according to claim 1, characterized in that the hydrocarbon serving as solvent is toluene or ethylbenzene. In JA-PS 7 789/67 a process for the preparation of 30 esters with phenol is bis- (4'-hydroxy-phenyl) -alkylcarbon- of bis- (3 ', 5'-di-tert-butyl-4'-hydroxy-phenyl) alkyl carbonate esters, whereupon they are described with isobutene in acid esters, which consists in the presence of sulfuric acid peralkylated. according to the reaction equation ketocarboxylic acid 1 / \ H -CO-A-COOR + 2 KO- / Q \ _ ■ HCl h H0C- = C, "Ch3 n2S0 ,, CH ■ 1 3-> r II20 - C - A-COO.R OK "A-COOR R = lower alkyl, R1 = H, alkyl, aryl, A = an optionally branched alkylene chain. As our own work has shown, this process does not produce any crystallizing products because obviously product mixtures are formed during the condensation reaction, which defy all attempts to persuade them to crystallize. The alkylation reaction makes these product mixtures even more inconsistent since, in the case of incomplete alkylation, mono-, di- and trialkylphenol carboxylic acid esters are formed in addition to the peralkylated compounds 3rd 632 734 will. It is therefore not surprising that the process products cannot be crystallized either. The difficulties mentioned are indicated in the cited JAPS, Examples 2 and 4, by stating that the crude product of the 1st process stage must occasionally be purified by column chromatography. Such cleaning is a laborious and time-consuming laboratory method that cannot be transferred to the technical scale. The lack of any information about the yields of end products obtained indicates the unsatisfactory course of the reaction in this procedure. The reason for the poor yields and the necessary, laborious cleaning measures is evidently that phenol reacts not only in the p-position but also in the o-position during the condensation with the ketocarboxylic acid esters. In addition, as is known from phenolic resin chemistry, it is capable of multiple condensation.