CS257381B1 - Production Methods of 3E, 5E and 3E, 5Z Isoters of 6,10-Dimethyl-3,5,9-undecatriene-2- - Google Patents

Abstract

The method of production of 3E,5E and 3E,5Z-isomers of 6,10-dimethyl-3,5,9-undecatrien-2-one from 3Z,5E and 3Z,5Z-isomers of 6,10-dimethyl-3,5,9-undecatrien-2-one is carried out by catalyzed isomerization at 20-40 °C in the presence of a catalyst and a lower aliphatic alcohol, eg methanol. The catalyst is an alkylbenzenesulfonic acid of the general formula R-C6H4-SO3H where R is an alkyl with a linear or branched structure and with 9-12 carbon atoms in the chain. After isomerization, the alcohol is distilled off from the reaction mixture. The method can be used mainly in the chemical and pharmaceutical industry.

Description

(54) Production method of 3E, 5E and 3E, 5Z isomers of 6,10-dimethyl-3,5,9-undecatrien-2-yne

Process for producing the 3E, 5E and 3E, 5Z-isomers of 6,10-dimethyl-3,5,9-undecatrien-2-one from the 3Z, 5E and 3Z, 5Z-isomers of 6,10-dimethyl-3,5,9- undecatrien-2-one is carried out by catalyzed isomerization at 20-40 ° C in the presence of a catalyst and a lower aliphatic alcohol e.g. methanol. The catalyst is an alkylbenzenesulfonic acid of general formula

RC ₆ H ₄ -SO ₃ H where

R is a linear or branched alkyl having 9-12 carbon atoms in the chain. After isomerization, the alcohol is distilled off from the reaction mixture. The process can be used mainly in the chemical and pharmaceutical industry.

The present invention provides a process for the production of the 3E, 5E and 3E, 5Z-isomers of 6,10-dimethyl-3,5,9-undecatrien-2-one from the 3Z, 5E and 3Z, 5Z-isomers of 6,10-dimethyl-3,5, 9-undecatrien-2-one by catalytic isomerization.

The 3E, 5E and 3E, 5Z-isomers of 6,10-dimethyl-3,5,9-undecatrien-2-one are an important intermediate in the synthesis of vitamins A and E. The synthesis of these vitamins consists of several reaction steps, where in the first step The 3E, 5E and 3E, 5Z-isomers of the aforementioned aliphatic ketone, commonly referred to as the trivial name pseudojonone, cyclize to O-ionone.

The 3Z, 5E and 3Z, 5Z-isomers present in the technical pseudojonone under the same conditions do not cyclize to the desired β-ionone and are therefore in the product ballast.

However, the formation of the 3Z, 5E and 3Z, 5Z-isomers cannot be avoided absolutely by the synthesis of pseudajonone by the Saucy-Marbet method from dehydrolinalool and methylisopropenyl ether. They are present in the crude pseudojonone in an amount of 10-60% depending on the synthesis conditions [Krajč B., Proksa B., Šausa I., Frimm R., Chemical Industry 33-58 (1983), 6

310].

For example, if the reaction is carried out at 100 ° C under the catalytic action of para-toluenesulfonic acid and for a reaction time of 17 hours, the 3Z, 5E and 3Z, 5Z-isomers of 6,10-dimethyl-3,5,9-undecatriene- 2-one in crude pseudojonone in an amount of 12 wt. By crude pseudojonone is meant a reaction mixture resulting from the alkaline isomerization of intermediate-6,10-dimethyl-4,5,9-undecatrien-2-one and distillation of the parallel reaction products and unreacted methylisopropenyl ether. By distillation, their proportion cannot be significantly reduced for the near boiling point of the 3E, 5E and 3E, 5Z-isomers.

Several ways of converting the 3Z, 5E and 3Z, 5Z isomers to the 3E, 5E and 3E, 5Z isomers by the action of catalysts, heat or ultraviolet radiation are known. Thus, for example, German Patent 2,404,913 describes isomerization by the action of iodine, p-toluenesulfonic acid, acetic acid, sodium hydroxide, silver nitrate, boron trifluoride etherate, heat and ultraviolet radiation. However, the residual content of the 3Z, 5E and 3Z, 5Z-isomers according to this process is so high that the use of the product for further synthesis to vitamin A and E is disadvantageous. In addition, contact of the 6,10-dimethyl-3,5,9-undecatrien-2-one isomers with drastic catalysts creates favorable conditions for the formation of undesirable bituminous substances. The products obtained from such mixtures are poorly stable, resulting in a deterioration in the physico-chemical properties of the distillates after only a few hours.

Another alternative conversion 3Z, 5E and 3Z, 5Z-isomers of the 3 E, 5 E, and 3E, 5Z-isomer is described in Czechoslovak Author's Certificate 235,228th According to the present invention is used for converting the strong acid cation exchanger in the H ⁺ form, which is contacted with a 6.10 dimethyl-3,5,9-undecatrien-2-one isomeric methanol solution. The 3Z, 5E and 3Z, 5Z isomers present are isomerized to the 3E, 5E and 3E, 5Z isomers so that their residual content falls below 2%. A disadvantage of the process according to the invention is the treatment with a large amount of methanol, namely that the catalyst is used in the dried state and in the H ⁺ -cycle, which is not a common supply form of strong acid cation exchangers. Installing the regeneration and drying equipment complicates production considerably.

The above drawbacks are overcome by the invention which is based on catalytic isomerization by the action of dodecylbenzenesulfonic acid.

According to the process of the present invention, the process for producing the 3E, 5E and 3E, 5Z-isomers of 6,10-dimethyl-3,5,9-undecatrien-2-one is carried out in such a way that a methanolic solution of crude pseudojonone containing 5-90% 3Z, 5E and 3Z, 5Z-isomers were stirred with dodecylbenzenesulfonic acid for 0.5-1 hour at 20-40 ° C. After the isomerization is complete, the catalyst is neutralized with, for example, a suitable amine and methanol is distilled off. The steam product has a residual content of 3Z, 5E and 3Z, 5Z-isomers below 2 wt%.

An advantage of the process according to the invention is that a smaller amount of methanol, usually 25% by weight of the crude pseudojonone used, is used to dilute the reaction mixture compared to known processes. Another advantage is the low content of residual unreacted metal ^j 3Z, 5E and 3Z, 5Z-isomer, which allows the use of the product on the synthesis of vitamin A and E. The catalyst is commercially available in a dry state, so that can be used without any prior treatment.

The raw material subjected to the isomerization according to the invention may be a technical mixture of 6,10-dimethyl-3,5,9-undecatrien-2-one isomers intentionally synthesized to contain a predominant amount of 3Z, 5E and 3Z.5Z-isomers or a technical mixture of isomers, in which the 3E, 5E and 3E, 5Z-isomers predominate but also contain ballast 3Z, 5E and 3Z, 5Z-isomers. These are converted into the 3E, 5E and 3E, 5Z-isomers useful for the synthesis of vitamins A and E by the above process.

The isomerization catalysts of this process are alkylbenzenesulfonic acids of the general formula wherein

R is a linear or branched alkyl having 9-12 carbon atoms in the chain. Substances of this type are manufactured industrially in large quantities as intermediates in the synthesis of surfactants. The usual form of delivery is anhydrous.

Further data on embodiments of the process of the invention as well as other advantages are apparent from the examples.

Example 1

Crude pseudojonone contains 9.5 wt. % Of the 3Z, 5E and 3Z, 5Z-isomers and 64.6 wt. 3E, 5E and 3E, 5Z-isomers. To 100 g of the product is added 1 g of Dubacid SP dissolved in 25 ml of methanol. The mixture was maintained at 20 ° C for 45 minutes with stirring. After this time, the reaction mixture was neutralized with triethanolamine to pH 6.5. Methanol is distilled off and finally the residue is distilled at 9.3 Pa to remove the bituminous substances. The distillate obtained is a clear liquid with a slight yellowish tinge and is stable for a long time. The contents of the grub components before and after the isomerization in the mixtures are as follows:

component

Before isomerization

After isomerization

3Z, 5E + 3Z, 5Z-isomers 9.5 wt.

% 3E, 5E + 3E, 5Z-isomers 64.6 wt.

Resin substances 9.7% wt.

The thermal conversion of the 3Z-isomers is 85.8%. The mass selectivity for the 3E-isomers is 88.8%.

1.3 wt. 71.9 wt. 13.7 wt.

The composition data refer to crude pseudojonone prior to dilution respectively. after isomerization and distillation of the solvent.

Example 2

The procedure is as in Example 1, except that the reaction time is 00 minutes and the amount of catalyst is 0.5 g of dodecylbenzenesulfonic acid, supplied under the trade designation, instead of 20 ° C at 40 ° C.

Dubacid SP.

Under these conditions, the following results were obtained:

component

Content before isomerization

Content after isomerization

3Z, 5E + 3Z, 5Z-isomers 14.01 *% 0.96%

3E, 5E + 3E, 5Z-isomers 66.05% 78.40%

Bituminous substances 8,4% 10,9%

The mass conversion of the 3Z-isomers is 93.1%.

The mass selectivity for the 3E-isomers is 94.6%.

Claims (1)

OBJECT OF THE INVENTION Method for producing 3E, 5E and 3E, 5Z-isomers of 6,10-dimethyl-3,5,9 undecatrien-2-one by isomerization of 3Z, 5E and 3Z, 5Z-isomers of 6,10-dimethyl-3,5,9-undecatriene -2-on at 20-40 ° C, characterized in that the isomerization is carried out in the presence of a catalyst which is an alkylbenzenesulfonic acid of the general formula R where R is a linear or branched alkyl group 9-12 chain carbon atoms and a lower aliphatic alcohol, preferably methanol.