DE1023027B - Process for the production of polyenedialdehydes - Google Patents

Description

GERMAN

The invention relates to a process for the preparation of previously unknown polyenedialdehydes, which is characterized is that you have an unsaturated 2,7-dimethyloctanedial, that has three conjugated multiple bonds between the aldehyde groups, acetalizes that obtained diacetal condensed in the presence of an acidic condensing agent with 2 mol of a vinyl ether and the obtained condensation product by treatment with acid, whereby hydrolysis and cleavage of Alcohol can be converted into the corresponding unsaturated 4,9-dimethyldodecanedial.

According to the previously known method for reacting acetals with vinyl ethers, it is necessary to use the acetal component to be used in large excess. This is necessary for the further reaction of the formed To be able to keep ether acetals within the narrowest possible limits with another mole of vinyl ether. The excess, acetal that has not reacted must after the condensation separated by fractional distillation. It is also necessary through fractional Distillation also to remove the polyether acetals formed by the further reaction of the ether acetals. The products are exposed to elevated temperatures for a long time and partially decompose in the process.

Surprisingly, it has now been found in the present process that α, ^ - unsaturated acetates, in particular the C ₁₀ -dialdehyde acetal, react quickly and uniformly to form the corresponding ether acetals. The reaction rate for the formation of the ether acetates is much greater than that of the further reaction with vinyl ether. The use of an excess of the acetal component and its separation after the reaction is thus superfluous.

The polyenedialdehydes obtained according to the invention, 4,9-dimethyldodecatetraen- (2,4,8,10) -in- (6) -dial- (1,12) and 4,9-dimethyldodecapentaen- (2,4,6, 8,10) -dial- (1,12) - _{hereinafter referred to as C 14} dialdehydes - are valuable intermediates for the synthesis of polyene dyes.

In the preferred embodiment of the invention, the 2,7-dimethyloctadiene- (2,6) -in- (4) -dial- (1,8) (C ₁₀ -dialdehyde) is acetalized, the 2,7-dimethyloctadiene- ( 2,6) -in- (4) -diacetal- (l, 8) (C ₁₀ -diacetal) condensed in the presence of an acidic condensing agent with a vinyl ether and the obtained 4,9-dimethyldodecadiene- (4,8) -in- (6) -diäther- (3,10) -diacetal- (1,12) (C ₁₄ -dietheracetal) by treatment with acid, whereby hydrolysis and cleavage of alcohol from the positions 2,3 and 10,11 are effected, in the 4,9-dimethyldodecatetraen- (2,4,8,10) -in- (6) -dial- (1,12) (C ₁₄ -dialdehyde) converted.

The first stage consists in the acetalization of the C ₁₀ dialdehyde. This takes place in a manner known per se. It is acetalized, for example, by means of an orthoester manufacturing process
of polyenedialdehydes

Applicant:

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

Representative: Dipl.-Ing. A. Bohr, Munich 5,
Dr.-Ing. H. Fincke, Berlin-Lichterfelde, Drakestr. 51,
and Dipl.-Ing. H. Bohr, Munich 5, patent attorneys

Claimed priority:
Switzerland from July 10, 1953

Dr. Otto Isler, Dr. Marc Montavon,

Dr. Rudolf Rüegg, Basel,

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

in the presence of an acidic condensing agent such as p-toluenesulfonic acid, phosphoric acid, BF _a etherate, ZnCl ₂ , NH ₄ Cl, NH ₄ NO ₃ , etc. The orthoesters of lower aliphatic acids with lower aliphatic alcohols, preferably methyl orthoformic acid, are particularly suitable for this purpose -, -ethyl- or -n-butyl ester. The acetates of C ₁₀ dialdehyde obtained are colorless oils which have two absorption maxima at 273 and 288 ταμ in the ultraviolet spectrum. For further processing, a special cleaning, e.g. B. by distillation, not required.

In the second stage, the C ₁₀ diacetal described above is condensed with a vinyl ether in the presence of an acidic condensing _{agent to give the C 14} diether acetal. Suitable condensing _{agents are BF 3} ether, ZnCl ₂ , TiCl ₄ , AlCl ₃ , FeCl ₃ , SnCl ₄ , etc. It is expedient to use the vinyl ether of the same alcohol with which the C ^ dialdehyde was acetalized, e.g. B. methyl vinyl ether, ethyl vinyl ether or n-butyl vinyl ether. The condensation takes place at the lowest possible reaction temperature; as a result, undesired side reactions such as polymerization and condensation of the C ₁₄ dietheracetal formed with vinyl ether can be avoided. The optimum reaction temperature is between 25 and 60 ° C., depending on the choice of condensing _{agent and the C 10 diacetal and vinyl ether selected for condensation. In the case of the preferred}

709 850/424

Embodiment, the two-molar amount of vinyl ether is allowed to act on the diacetal at 25 to 50 ° C. in the presence of boron trifluoride etherate or zinc chloride. In this way, largely pure C ₁₄ diether acetals are obtained in almost quantitative yield. They are colorless oils that have two absorption maxima in the ultraviolet spectrum at 273 to 274 ΐημ and 288 to 290 πιμ. For further processing, a special cleaning, e.g. B. by distillation, not required.

The third stage consists in _{hydrolyzing the C 14} diether acetals in a manner known per se in an acidic medium, the C 14 dialdehyde being formed _{with simultaneous elimination of alcohol from positions 2, 3 and 10, 11.} This reaction stage can expediently be carried out in the presence of water-soluble, non-volatile organic or inorganic acids such as p-toluenesulionic acid, acetic acid, propionic acid, oxalic acid, sulfuric acid, phosphoric acid, or acidic, water-soluble salts such as ZnCl ₂ and NaHSO ₄ . During the reaction, it is advantageous to exclude oxygen and to work under conditions in which the alcohol formed is continuously distilled off from the reaction mixture. A water-miscible solvent, such as, for example, dioxane, tetrahydrofuran, ethylene glycol dimethyl ether, etc., can be added to the reaction mixture in order to obtain a homogeneous reaction mixture. Preferably, the C ₁₄ diether acetal is either heated with aqueous phosphoric acid in the presence of a water-miscible solvent to about 100 ° C, the alcohol formed is continuously removed from the reaction mixture, or boiled with acetic acid with the addition of alkali acetate and a little water, the the resulting alcohol is bound in the form of ethyl acetate. When the reaction mixture is diluted with water, the crystalline C ₁₄ dialdehyde precipitates out, which can be obtained by recrystallization, e.g. B. from ethyl alcohol or chloroform, or can be purified by sublimation. To avoid substance losses through polymerization and decomposition, it is advisable to avoid temperatures above 120 ° C. during the entire process and, in particular, to further process _{the intermediate products, namely C 10} -diacetal and C _{14 -dietheracetal, undistilled.} . The C ₁₄ dialdehyde [4,9-dimethyldodecatetraen- (2,4,8,10) -in- (6) -dial- (1,12)] obtained in this way melts at 165 ° C. and has two absorption maxima in the ultraviolet spectrum 371 πιμ, ε == 53 500, and at 391 ταμ, ε = 51700 (in fine spirit). Partial hydrogenation of the triple bond, which can be brought about by the action of 1 mol of hydrogen in the presence of a palladium-lead catalyst, results in 4,9-dimethyldodecapentaen- (2,4,6,8,10) -dial- (l, 12). The cis form primarily formed during catalytic hydrogenation can be converted into the "all-tr ans" form by the action of light, heat or iodine.

This »AH-transcc-form of 4,9-dimethyldodecapentaen- (2,4,6,8,10) -dial- (l, 12) also arises, as described above, according to the method according to the invention, if the starting material is 2,7-dimethyloctatriene- (2,4,6) -dial- (1,8) with a melting point of 161.5 to 162 ° C, which consists of 4,9-dimethyloctadiene- (2,6) -in- (4) -dial- (1,8) by the action of 1 mol of hydrogen in the presence of a palladium-lead catalyst and Heating the hydrogenation product can be obtained.

Examples
C ₁₀ diacetal

A warm solution of 40 parts by weight of 2,7-dimethyloctadiene - (2.6) - in - (4) - dial - (1.8) in 120 parts by weight of ethyl orthoformate is mixed with a warm solution of 4 parts by weight of ammonium nitrate in 50 parts by volume of absolute alcohol and left to stand for 48 hours, the mixture gradually assuming room temperature. The reaction mixture is then taken up in ether, washed with sodium bicarbonate solution and dried over potash. After the ether solution has been concentrated, the excess ethyl orthoformate and the ethyl formate formed are separated from the condensation product in vacuo. The pure 2,7-dimethyloctadiene- (2,6) -in- (4) -tetraäthyldiacetal- (1,8) with a boiling point of 122 to 127 ° C./0.03 mm is obtained by distillation in a high vacuum; «« ° 1.4892; UV maxima: 273 πιμ, ε = 27200, and 288 πιμ, ε = 22600 (in fine spirit).

C ₁₄ diether acetal

. 102 parts by weight of 2,7-dimethyloctadiene- (2,6) -in- (4) -tetraäthyldiacetal- (1,8) and 0.5 parts by _{volume of BF 3} etherate are gradually mixed with 47 parts by weight of ethyl vinyl ether. The rate of addition is regulated so that the reaction temperature remains between 30.degree. And 35.degree. The mixture is stirred for a further 3 hours at 35 ° C., then taken up in ether, washed with dilute sodium hydroxide solution and dried over potash. After concentrating the ethereal solution, 137 parts by weight of crude 4,9-dimethyldodecadiene- (4,8) -in- (6) -diäthoxy- (3,10) -tetraäthyldiacetal- (l, 12) are obtained. The compound, purified by distillation in a high vacuum, boils at 160 to 61 ° C / 0.03 mm; »F ° 1.4778; UV maxima: 274πιμ, ε = 26200, and 290 ηιμ, ε = 23400 (in fine spirit).

C ₁₄ dialdehyde

. For saponification, the crude 4,9-dimethyldodeeadiene (4.8) is dissolved -in- (6) -diäthoxy- (3,10) -tetraäthyldiacetal- (1.12) in a mixture of 800 parts by volume of dioxane, 200 parts by volume of water and 35 parts by volume of phosphoric acid (87%) and adds a trace of hydroquinone. That The mixture is boiled under nitrogen for 7 hours, slowly using a Raschig ring column Dioxane-alcohol-water mixture is distilled off. This is maintained by adding dioxane - water dropwise Reaction volume constant. The warm reaction mixture is then poured into about 2000 parts by volume with stirring Ice water, the 4,9-dimethyldodecatetraen- (2,4,8,10) -in- (6) -dial- (l, 12) immediately precipitates in crystalline form. The precipitate is filtered off with suction and washed well with water. After recrystallization from ethyl alcohol and drying in vacuo, about 45 parts by weight of the pure are obtained Compound with a melting point of 165 ° C.

Claims (6)

PATENT CLAIMS: 1. Process for the preparation of polyenedialdehydes, characterized in that one is an unsaturated 2,7-Dimethyloctanedial, the three conjugated multiple bonds between the aldehyde groups possesses, acetalized, the diacetal obtained in the presence of an acidic condensing agent with 2 mol of a vinyl ether condensed and the condensation product obtained by treatment with acid, thereby causing hydrolysis and cleavage of alcohol into the corresponding unsaturated 4,9-Dimethyldodecandial transferred. 2. The method according to claim 1, characterized in that one with a lower alcohol acetalized unsaturated 2,7-dimethyloctanedial- (1,8) condensed with the vinyl ether of the same lower alcohol. 3. The method according to claim 1 and 2, characterized in that the two molar amount of vinyl ether at 25 to SO ⁰ C is allowed to act on the diacetal. 4. The method according to claim 1 to 3, 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. 5. The method according to claim 1 to 4, characterized in that the condensation product obtained with acetic acid with the addition of alkali acetate and heated some water to the boil. 6. The method according to claim 1 to S, characterized in that temperatures above 120 ⁰ C are avoided during the entire process and the intermediate products are further processed undistilled. Considered publications:
Houben-Weyl, Methods of Organic Chemistry, Vol. VII, Teül, pp. 116 and 117; U.S. Patent Nos. 2165,962, 2,487,525,
ίο 2 586 305, 2 586 306, 2 615 922; Journal of the American Chemical Society, 71 (1949), p. 3468;
Bulletin Soc. Chimique France, 5, 18 (1951) p. 844.