DE1210780B - Process for the production of polyunsaturated aldehydes - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. Eq .:

C07c

German KL: 12 ο -7/03

Number: 1210 780

File number: B 74476IV b / 12 ο

Filing date: November 30, 1963

Opening day: February 17, 1966

There are a number of syntheses in the polyene and carotenoid series, which are based on Wittig Use the olefination reaction to link the fragments (see, for example, the summaries by H. P ο m m e r in Angew. Chem., 72 [1960], pp. 811 and 911). These syntheses have in common that after the linkage, the new end groups of the chains are only converted in a suitable manner must be before another chain extension with the help of the Wittig reaction ίο is possible.

It has now been found that a direct chain extension of Aldehydes can be achieved. The invention relates to a method for producing multiple unsaturated aldehydes and is characterized in that one phosphorus-containing ylenals of the general formula

Ar

Ar-P = O-C =

Ar

Ri R ₂ R ₃ H

-Irishman

in which Ar is an aryl radical optionally substituted by alkyl or alkoxy groups, Ri, R2 and R3 are hydrogen or alkyl radicals and η is an integer from 1 to 3, is reacted with aldehydes.

Process for the production of multiple
unsaturated aldehydes

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft, Ludwigshafen / Rhein

Named as inventor:

Dr. Herwig Freyschlag,

Dr. Werner Reif,

Dr. Axel Nürrenbach,

Dr. Horst Pommer, Ludwigshafen / Rhine

The Ylenale are phosphorane compounds that have a phosphor-ylene group in the same molecule and contain an aldehyde group conjugated thereto. They are expedient according to the »Procedure of patent application B 74473 IV b / 12 ο obtained by clicking on the corresponding phosphonium salts Can act proton acceptors.

The reaction in the process of this invention proceeds according to the scheme

R ₁ -C +1

R ₄ -CH = C- Ri

II

In formula II, R4 stands for a radical which does not contain any substituents which react undesirably with the ylenal and which can usually be present in aldehyde molecules. Accordingly, it can mean, for example, a saturated or unsaturated alkyl or cycloalkyl radical, aryl, aralkyl or a combination of these groups. The remainder of R ₄ can already be the group

Ri

R ₂ R ₃

contain, and it can substituents of the above R ₂ Rs

III

designated type. Dialdehydes are also suitable for the process of this invention if 2 molecules of Ylenal should be reacted with 1 molecule of dialdehyde.

As aldehydes R4 - CHO can therefore be practical all aldehydes are used, provided they do not contain any groups with which the Ylenale in undesirable React wisely or which have a destructive effect on the Ylenale, e.g. B. strong acids. There one the most important areas of application of the new process is the chain extension of aldehydes Polyene and carotenoid series are examples of suitable aldehydes: jS-Jonylidenacetaldehyd, / Ϊ-retins, α-retins, ß-apo-

609 508/278

14'-carotinal (C22), j8-Apo-12'-carotinal (C ₂₅ ), jS-Apo-10'-carotinal (C27), /? - Apo-8'-carotinal (C30), jS-Apo- o'-carotinal (C ₃₂ ), also the Cio, Cm and Ca) dialdehydes known from carotene chemistry.

Suitable Ylenals are, for example, triphenylphosphine-ß-formylcrotylene (IV), triphenylphosphine-formylcrotylene (V), triphenylphosphine-2-methylpentadiene (1,3) -al- (5) -methylene, triphenylphosphine-1 - methyl - pentadiene - (1,3) - al - (5) -methylene, triphenylphosphine - 2,6 - dimethyl - heptatriene - (1,3,5) -al - (7) - methylene (VI), triphenylphosphine -1,5 - dimethyl - heptatriene - (1,3,5) - al - (7) - methylene (VU) and triphenylphosphine - 1,6 - dimethyl - heptatriene- (1,3,5) -al- (7) -methylene. The Ylenals cause an aldehyde to be extended by several double bonds. For example, the Ylenale IV and V are suitable for the production of isoprenologous compounds,

Ar
Ar-P = CH-CH = C-CHO

/ I

Ar CH ₃

IV

Ar

Ar-P = CH-C = CH-CHO

Ar

CH ₃

which are of particular importance in the carotenoid series. It is essential that the introduction several isoprene residues one after the other in the same molecule is possible, since after each chain extension again a free aldehyde group is available for a new condensation reaction stands. The aldehydes can thus be lengthened repeatedly. One can therefore use the procedure this invention use an aldehyde, which is itself already by chain extension of an aldehyde with one. Ylenal has been received.

You do not need the aldehyde obtained for the further reaction according to this invention isolate, but can use it again immediately in the reaction medium.

It sets the phosphorus-containing Ylenale with the aldehydes at temperatures of about 20 to 180 ° C, preferably 50 to 10O ⁰ to Cj. Examples of suitable solvents are alcohols such as methanol, ethanol, isopropanol, aromatic hydrocarbons such as benzene and toluene, aliphatic and alicyclic hydrocarbons such as octane or cyclohexane, chlorinated hydrocarbons such as methylene chloride, chloroform and chlorobenzene, ethers such as diethyl ether, diisopropyl ether or tetrahydrofuran , Nitriles such as acetonitrile or benzonitrile, and acid amides such as formamide, dimethylformamide or diethylformamide. In some cases, water can also be used or shared. If the aldehyde component is liquid under the reaction conditions, an excess of it may be sufficient as a solvent. The reaction times can _r be very different depending on the kind of compounds used. They can be ^x / ₂ to 24 hours, preferably 1 to 12 hours. However, shorter or longer times are also possible. The reaction mixtures can be worked up by the customary methods. The products of the process can be isolated, for example, by crystallization, distillation, molecular distillation or partitioning.
To carry out the process of this invention it is not necessary that the ylenals are isolated and, if necessary, purified before they are reacted with the aldehydes; they can also easily be used in the medium in which they were produced.

The ylenals required in the reaction according to the invention can also be used in a customary manner from their phosphonium salts in the presence of the aldehydes, so that the Ylenale in statu nascendi react with the aldehydes.

If the aldehyde is allowed to act on the ylenal in molar amounts, essentially uniform process products are formed. If Ylenal is used in excess, mixtures of compounds are often formed whose chains are lengthened by whole multiples of the chain length η + 2 of the Ylenal used.

The process of the invention offers a number of advantages over the usual Wittig reactions. The careful exclusion of moisture and oxygen, as is the case with many Wittig olefinations is required, can be omitted here. Another difficulty with the Wittig reaction This is often due to the fact that the aldehydes used for ylid formation under the influence of the alkaline reagent give side reactions (see. J. Org. Chem., 28, p. 372 [1963]), especially then, when it comes to sensitive aldehydes. Such side reactions can occur in reactions can also be avoided by very alkali-labile aldehydes with Ylenalen without any special effort, because the Ylenale can be easily and completely cleaned of alkali. These advantages have two of S.M. M a k i η (Bar. Akad. Wiss. USSR, 138, pp. 387 to 389 [1961], and J. f. General Chem. [Russ.], 32 [94],

Pp. 3159 to 3161 [1962]) phosphonium salts XI and XII described some time ago do not.

OC2H5

(C ₆ H ₅₎ P - CH ₂ - CH = C - CH
^ΒΓθ

XI

CH ₃ OC ₂ H ₅

OC ₂ H ₅

(C ₆ Hs) ₃ P - CH ₂ - C = CH - CH

CH ₃ OC ₂ H ₅

XII

The ylides produced from these salts cannot be isolated and are unstable and sensitive against moisture and oxygen. A purification of these ylides and a further conversion of their condensation products without changing the end groups beforehand is not possible.

From a publication by Tri ρ ρ e 11 and Walker (J. Chem. Soc, 1961, p. 1266) there are two compounds of the general formula I, but with η = O and Ri = H or methyl, and their reaction with benzaldehyde known. According to the reaction conditions specified there, for. B. 24 hours reflux in benzene, it was unlikely that the higher members of this series, if they were to be stable at all, could withstand reactions with aldehydes under similar conditions; rather, it was to be expected that the Ylenals would be destroyed beforehand by side reactions such as polymerizations or self-condensation. It is therefore all the more astonishing that very high yields are achieved in the reaction of ylenals with aldehydes according to the invention and side reactions of the ylenals practically do not occur under reaction conditions which the person skilled in the art applies to the knowledge of this invention.

The process products are z. B. as food colors or used provitamins. For example, from the compound IV and retins of the ^ -Apo-H'-carotinal (C25) and from this by further reaction with IV the ß-apo-8'-carotenal (C30), which can also be obtained directly by reacting retins and triphenylphosphine-2,6-dimethylheptatriene - (1,3,5) - al - 7 - methylene (VIII), both substances with provitamin A effect, which are suitable for food coloring. From / i-Jonyliden-acetaldehyde and the compound V the vitamin A aldehyde (= retins) is obtained. By reacting ylenalen with other aldehydes valuable new products can be obtained, which z. B. for the production of dyes, Medicines, pesticides and optical brighteners are suitable.

The parts given in the examples are parts by weight. They relate to parts of volume like Grams to cubic centimeters.

example 1

2.84 parts of vitamin A aldehyde and 3.44 parts of triphenylphosphine-2-formyl-propen-1 -yl-methylene are heated to boiling in 100 parts of dry benzene in a nitrogen atmosphere for 12 hours. The solvent is distilled off under reduced pressure, the residue is taken up in ether and extracted several times with methanol containing 60 parts by volume of water. After drying the ether solution over sodium sulfate and evaporation of the solvent 3.18 parts remain a yellow-orange oil return {X _m ax = 410 πΐμ; E} * "= 1440), from which the / f-apo-12'-carotenal (C25) can be obtained in crystalline form after prior isomerization by boiling in ligroin in a nitrogen atmosphere. F. = 87 to 88 ⁰ C (from petroleum ether). X _max = 415 ηΐµ; E} * _m = 2140 (measured in cyclohexane).

Example 2

3.5 parts of apo-12'-carotenal (C ₂₅ ) and 3.44 parts of triphenylphosphine-2-formyl-propen-1-yl-methylene are heated to boiling in 100 parts by volume of dry acetonitrile in a nitrogen atmosphere for 10 hours . The solvent is distilled off under reduced pressure, the residue is taken up in ether and extracted several times with methanol which contains 60 parts by volume of water. After the ethereal phase has been dried over sodium sulfate, the solvent is distilled off. 3.71 parts of a deep red oil remain, from which the / J-apo-S'-carotenal (Qo) formed can be obtained after previous isomerization by heating in ligroin in a nitrogen atmosphere by crystallization from benzene-methanol. Purple, shiny metallic leaves with a temperature of 137 ° C. Xmax = 458 πΐµ; E} * _m = 2590 (measured in cyclohexane).

Example 3

2.8 parts of vitamin A aldehyde and 3.7 parts of triphenylphosphine-2-methyl-pentadiene- (1,3) -al- (5) -methylene are in 100 parts of dry acetonitrile in a nitrogen atmosphere for 10 hours Boiling heated. The solvent is distilled off under reduced pressure, the residue is taken up in ether and extracted several times with methanol which contains 60 parts by volume of water. After the ethereal phase has been dried over sodium sulfate, the solvent is distilled off. 3.5 parts of a deep red oil remain, from which the β-apo-10'-carotenal which has formed can be obtained in pure form by chromatography on aluminum oxide. Red oil; Xmax = 436 πΐμ (in cyclohexane); E} * _m = 2030.

Claims (4)

Patent claims: 1. Process for the production of polyunsaturated aldehydes, characterized in that that one phosphorus-containing Ylenals of the general formula Ar Ar - P = C-fC = C-- Ar Ri R ₂ Rs in which Ar is an aryl radical optionally substituted by alkyl or alkoxy groups, Ri, R2 and R3 are hydrogen or alkyl radicals and η is an integer from 1 to 3, is reacted with aldehydes. 2. The method according to claim 1, characterized in that the reaction with a Aldehyde carries out the rest - C -4- C = CC Ri R ₂ R ₃ Contains, where Ri, R ₂ , R3 and η have the meaning given in claim 1. 3. The method according to claim 1, characterized in that the reaction with a do Aldehyde of the vitamin Α, polyene or carotene series performs. 4. Process according to claims 1 to 3, characterized in that the process in a solvent. Considered publications:
Tetrahedron letters, 1963, No. 15, pp. 979 to 984.