DE1026295B - Process for the preparation of 2, 7-dimethyloctatriene- (2, 4, 6) -dial- (1, 8) - Google Patents

Description

GERMAN

The polyenedialdehyde ^^ - dimethyl-octatriene- (2,4,6) -dial- (1,8) - _{hereinafter referred to as C 10} -dialdehyde - was previously made by condensation of acetylenedimagnesium bromide with 2 moles of methacrolein, rearrangement of the resulting 2.7 -Dimethyl-octadiene- (l, 7) -yne- (4) -diol- (3,6) to 2,7-dimethyl-octadiene- (2,6) -yne- (4) -diol- (l, 8), partial hydrogenation of the acetylene bond and subsequent oxidation, whereby the order of the last two stages can be exchanged (Annalen der Chemie, Vol. 580 [1953], p. 7, Vol. 583 [1953], p. 100, Journal of the Chemical Society [1953], p. 3294). The overall yield is unsatisfactory and the process is cumbersome.

It has now been found that the C ₁₀ -dialdehyde can be obtained by condensing a butenedial diacetal in the presence of an anhydrous acid with preferably twice the molar amount of a propenyl ether and the resulting 2,7-dimethyl-octene (4) diether _{- (3,6) -diacetal- (1,8) converted into the C 10} -dialdehyde by heating with acid, whereby hydrolysis and cleavage of alcohol from the positions 2,3 and 6,7 are effected. The process is technically simple and gives the C ₁₀ dialdehyde in good yield.

The implementation of unsaturated monoacetals with vinyl or propenyl ethers and the saponification of the resulting unsaturated alkoxyacetals to polyunsaturated aldehydes has already been described in the literature, e.g. B. USA patents 2,586,305 and 2,586,306. In order to avoid the undesired formation of a mixture of mono- and To counteract polycondensation products, one was forced to use the acetals compared to the Add vinyl or propenyl ether in excess. Nevertheless, it was necessary to use the reaction products obtained to be separated by molecular distillation. It has now surprisingly been found that butenedial diacetals can be reacted with molar amounts of propenyl ether without higher condensation products develop.

The C ₁₀ dialdehyde is a valuable intermediate for the synthesis of polyene dyes. Thus, the Reformatsky reaction with 2 mol of y-bromotiglic acid ester • - ■ in analogy to the synthesis of dehydrocrocetin (Annalen der Chemie, Vol. 580 [1953], p. 7) - and subsequent elimination of water leads directly to crocetin ester. Acetalization of the C ₁₀ dialdehyde, condensation of the acetals formed with 2 moles of vinyl ether and treatment of the condensation products with acid gives 4,9-dimethyl-dodecapentaen- (2,4,6,8,10) -dial- (l, 12) , an intermediate for the synthesis of crocetin, bixin and lycopene.

The starting materials for the process according to the invention can be prepared by known processes will; z. B. the maleindialdehyde diacetals by catalytic partial reduction of the acetylenedialdehyde process

for the production of 2,7-dimethyloctatriene- (2,4,6) -dial- (l ,8th)

Applicant:

F. Hoffmann-La Roctie & Co.
Aktiengesellschaft, Basel (Switzerland)

Representative: Dr. G. Schmitt, lawyer,
Loerrach (Bad.), Friedrichstr. 3

Claimed priority:
Switzerland from December 8, 1953

Dr. Otto Isler, Dr. Marc Montavon, Dr. Rudolf Rüegg,

Basel,

and Dr. Paul Zeller, Neuallschwil (Switzerland),
have been named as inventors

acetals obtained. A. Wohl and E. Bernreuther (Annalen der Chemie, Vol. 481 [1930], p. 10) produced maleindialdehyde tetramethyl diacetal with a boiling point of 97.5 ° C./11 mm and a refraction of n% 1.43447 in this way . Maleindialdehyde tetraethyl diacetal was developed by A. Wohl and B. MyIo (reports of the German Chemical Society, vol. 45 [1912], p. 339) and later by K. Henkel and F. Weygand (reports of the German Chemical Society, vol. 76 [1943 ], P. 814); the latter authors give the product a melting point of 18 to 19 ° C. The acetal can be distilled undecomposed in a vacuum (boiling point 128 to 130 ° C / 15 mm) and is then a colorless oil with the refraction nf 1.4315. The acetals of maleindialdehyde with higher alcohol, e.g. B. the tetrapropyl or tetrabutyl diacetals can be obtained in an analogous manner.

Of the alkyl propenyl ethers required for the condensation, the ethyl compound is described in the literature (A. Kirrmann, Bulletin de la Societe Chimique de France, Vol. 6 [1939], p. 841; MG Voronkov, Zhur. Obshchei Khim, Vol. 20 [ 1950], p. 2060). The easiest way to obtain the ethyl propenyl ether is by pyrolysis of the propionaldehyde diethyl acetal. The compound obtained in this way is a mixture of cis-trans isomers which is suitable for condensation; it boils at 68 to 72 ° C / 740mm and has the refraction nf 1.3960. In the same way, homologous Pro ¹

709 910 / 41C

penyl ether here, ζ. B. the Methylpropenyläther of boiling point 45 to 47 ° C / 740mm, and the refractive «f 1.3870 ° and the n-Butylpropenyläther, boiling point 120 ⁰ C, wf ° 1.4100.

In the first stage of the process according to the invention, the butenedial diacetal is condensed with a propenyl ether in the presence of an anhydrous acid. Suitable condensing agents are boron trifluoride, zinc chloride, titanium tetrachloride, aluminum chloride, tin tetrachloride, etc. The condensation is expediently carried out at as low a temperature as possible in order to avoid undesirable side reactions, such as polymerization and condensation, of the C ₁₀ dietheracetal formed with propenyl ether. The optimum reaction temperature, depending on the choice of condensing agent and the butenedial diacetal and propenyl ether selected for condensation, is below 50 ° C. In the preferred embodiment, the two-molar amount of propenyl ether is allowed to act on the diacetal at 0 to 50 ° C. In this way, largely pure C ₁₀ dietheracetals in the form of colorless oils are obtained in an almost quantitative yield. These oils are mixtures of stereoisomers from which an isomer can be separated off in crystalline form on cooling, which, after recrystallization from 0.5 parts by volume of petroleum, is added boron trifluoride etherate) and heated ^{to 30 ° C. with stirring.} 375 parts by volume of ethyl propenyl ether are then added dropwise while stirring continuously. The rate of addition is regulated so that the reaction temperature remains between 30.degree. And 35.degree. When everything has been added dropwise, stirring is continued for about half an hour, then the reaction mixture is diluted with ether and the catalyst is removed from the ether solution with dilute sodium hydroxide solution. After evaporation of the dried and filtered ether solution, 660 parts by weight of the crude C ₁₀ dietheriacetal are obtained.

The pure 2,7-dimethyl-3,6-diethoxy-octen- (4) -tetraäthyldiacetal- (1,8) be won. Bp. 143 ° C / 0.06 mm, »f ° 1.4395.

It is a mixture of isomers. Upon standing, the distilled product, a part of the product crystallizes and melts after recrystallization from petroleum ether at about 7O ⁰ C.

The crude C ₁₀ -Diätherdiacetal is 1300 parts by volume of dioxane, 130 parts of water and 53 parts by weight of 85% phosphoric acid was added and the mixture after addition of a trace of hydroquinone as an antioxidant for 8 hours in a nitrogen atmosphere to about 100 ⁰ C.

the 2,7-dimethyl-octatriene- (2,4,6) -dial- (1,8) precipitates in crystalline form. After cooling, the mixture is cooled to ^{0 ° C. for a few hours.} The crystals are filtered off with suction and dried in vacuo. About 200 parts by weight of product with a melting point of 158 to 160 ^° C. are obtained.

Example 2

melts ether at about 7O ⁰ C. Heated for further processing 25. About 1000 parts by volume are distilled off, a separation of the isomers or a distillation of the dioxane-water-alcohol mixture. Not necessary due to slow oily products. Adding a dioxane-water mixture (4: 1) is the

The second stage of the process according to the invention, when the volume of the reaction _{solution is approximately constant, is that the C 10} -dietheracetals are kept in themselves. The still warm solution is then hydrolyzed in a known manner in an acidic medium, with 30 1500 parts by volume of warm water being carefully diluted, with simultaneous elimination of alcohol from the
Positions 2.3 and 6.7 of the C ₁₀ dialdehyde is formed.
This reaction stage can expediently in the presence of water-soluble, non-volatile organic or
inorganic acids such as p-toluenesulfonic acid, oxalic acid, 35
Acetic acid, sulfuric acid, phosphoric acid, or acidic
reactive water-soluble salts such as zinc chloride and
Sodium bisulfate. In the reaction, 50 _{parts by weight of C 10} dietary diacetal (according to Example 1

oxygen is advantageously excluded and prepared under and purified by distillation) conditions are used in which the resulting ₄₀ 140 parts by volume of glacial acetic acid, 20 parts by volume of ethyl acetate and alcohol are continuously mixed from the reaction mixture - 3 parts of water and, after a trace has been added, distilled. It can be a water-miscible solvents of hydroquinone for about 30 hours at 100 ⁰ C heated medium, such as dioxane, tetrahydrofuran, Then, the resultant ethyl acetate in vacuo, ethylene glycol dimethyl ether, etc., impose distilled off and the residue a HO on ice —Pour water to obtain a pleasant reaction mixture. Preferably the precipitate is filtered off and the C ₁₀ diether acetal is crystallized from methanol using aqueous phosphoric acid. The 2,7-dimethyl-r is obtained -------

heated to about 100 ° C. in the presence of a water-miscible solvent and the alcohol formed is continuously removed from the reaction mixture. When the reaction mixture is diluted with water, the crystalline C ₁₀ dialdehyde precipitates.

The hydrolysis can also be brought about _{by refluxing the C 10} diether acetals with aqueous acetic acid for a few hours and then boiling them with it

Diluted water, the acetic acid in anhydrous ₅₅ C ₁₀ dialdehyde from melting point 159 to 160 ⁰ C.
Form can be added beforehand to the condensation reaction.

_{The C 10} dialdehyde produced by the process according to the invention has the trans configuration on all double bonds.

In order to avoid substance losses due to polymerization and decomposition, it is advisable to avoid during the entire process temperatures above 120 ⁰ C and in particular the intermediates nämkristallisiert. You get that

(2,4,6) -dial- (l, 8) of melting point 158-160 ⁰ C.

Example 3

27 parts by weight of C ₁₀ -Diätherdiacetal (it was the crystalline isomers prepared according to Example 1 used a melting point of about 7O ⁰ C) with phosphoric acid and aqueous dioxane as indicated in Example 1, treated; the pure hmelzpunt is obtained immediately when working up

Example 4

A mixture of 90 parts by weight Maleindialdehydtetraäthyldiacetal and 7 parts by volume of a 10 ° / _o solution of zinc chloride in Essigester next to each 100 parts by volume Äthylpropenyläther and further 15 parts by volume of the zinc chloride solution are added within about 2 hours with stirring at 70 ° C at the same time. After standing overnight at room temperature, use

lent the Cjo-Diätheracetale, undistilled weiterzuverar- 65 90 parts by volume of 10 ° / _o strength alcoholic Natriumhydroxyd-

work. solution made alkaline, taken up in ether and with

Example 1 ^ η-sodium hydroxide solution and water washed. After leaving

By steaming the ether, 154 parts by weight of raw material are obtained

385 parts by weight of maleindialdehyde _{tetraethyl diacetal C 10} diether diacetal, which is now mixed with 1 part by weight of anhydrous zinc chloride (or 70 250 parts by volume of glacial acetic acid, 32 parts by volume of water, 43 parts by weight)

parts by weight of sodium acetate and 0.2 parts by weight of hydroquinone is heated to 95 to 100 ° C for 3 hours. After cooling, it is taken up in methylene chloride, washed neutral with sodium bicarbonate solution and water, dried and concentrated. Crystallization from alcohol gives 40 _{parts by weight of C 10} dialdehyde with a melting point of 158 to 160 ° C.

Claims (5)

Patent claims: 1. Process for the preparation of 2,7-dimethyloctatriene- (2,4,6) -dial- (1,8), characterized in that a butenedial diacetal in the presence of an anhydrous acid with twice the molar amount of one Propenyl ether condenses and the resulting 2,7-dimethyl-octen- (4) -diether- (3,6) -diacetal- (l, 8) by heating with acid, causing hydrolysis and elimination of alcohol from positions 2,3 and 6,7 be effected, converted into the 2,7-dimethyl-octatriene- (2,4,6) -dial- (1,8). 2. The method according to claim 1, characterized in that the two molar amount of propenyl S. Ether allowed to act on the butenedial diacetal below 50 ° C. 3. The method according to claim 1 and 2, characterized in that the condensation product obtained with aqueous phosphoric acid in the presence a water-miscible solvent is heated and the resulting alcohol is continuously removed from the Reaction mixture removed. 4. The method according to claim 1 and 2, characterized in that the condensation product obtained is heated with dilute acetic acid, wherein the alcohol formed is continuously bound with the formation of ethyl acetate. 5. The method according to claim 1 to 3, characterized in that one during the entire process Avoids temperatures above 120 ° C and the intermediate product is further processed undistilled. Considered publications:
U.S. Patent Nos. 2,586,305, 2,586,306;
German Patent No. 893,947;
Journal of the American Chemical Society, 72 (1950), 234, and 71 (1949), pp. 3468-3472. © 709 910/410 3.