DE2411530A1 - METHOD FOR MANUFACTURING ALDEHYDE - Google Patents

Description

Dr. Ing. Ä, van dsf shipyard Dr. Frenz Udersr PATENT ADVOCATE! J J

RAN 6OO3 / IO7

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

Process for the production of aldehydes

The present invention relates to a process for the preparation of aldehydes, in particular a process for the preparation of α, β-unsaturated aldehydes of the formula

C = CH - CH ₀ - CH ₀ - C = CH - CHO

^{2 2} I ₁

R ¹

1 2

where R is lower-alkyl, R is lower-alkyl and vP is hydrogen, lower-alkyl or a straight- or branched-chain aliphatic hydrocarbon radical having 2 to 8 carbon atoms and 1 or 2 double bonds.

409839/1030

The inventive method is characterized in that either

a) a compound of the formula

R.

C = CH - CH - O - CH = CH - C = CH

R.
or ι

H ₀ C = CH - C - CH - C = CH ₀

R ^ CHO R

12 3

wherein R, R and Vr are as defined above,

heated to a temperature of 100 to 230 °, or b) an acetal of the formula

C = CH - CH ₀ - 0 - CH - CH = C - 'CH,

Il ³

4 1 VII

OR R ^XX

CH - CH ₀ - 0 - CH - 0 - CH ₀ - CH = C

² I ²

CH

Il η

C-R ■

12 "5
wherein R, R or Yr are as defined above

and OR represents a hydrolyzable, split hydroxy group, pyrolyzed.

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The aldehydes of the formula I are obtained in yields of up to 70% by the process according to the invention.

In the present application, the term "lower alkyl" denotes both straight-chain and branched-chain alkyl groups with 1 to 7 carbon atoms, such as methyl, ethyl, propyl, isopropyl, η-butyl, isobutyl, n-hexyl and isohexyl, with methyl being preferred. The term "halogen" includes all 4 halogens, i.e. fluorine, chlorine, bromine and iodine, where Chlorine and bromine are preferred. The term "alkali metal" includes metals such as sodium, lithium and potassium.

The term "lower alkanoyl" refers to groups with 2 to 7 carbon atoms, such as acetyl, propionyl, Pivalyl, etc., with acetyl being preferred. The term "aryl" denotes mononuclear aromatic hydrocarbon groups such as phenyl and tolyl that are unsubstituted or may be substituted in one or more positions by lower-alkyl, halogen, nitro, lower-alkylenedioxy or Lower alkoxy, as well as polynuclear aromatic groups, such as naphthyl, anthryl, phenanthryl, azulyl, etc., which can also be substituted by one or more of the aforementioned groups. The preferred aryl group is phenyl. The term "aromatic acid" means one Acid of the formula

Aryl-C-OH O

wherein aryl is as defined above. The preferred aromatic acid is benzoic acid.

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Shown as hydrolyzable protected hydroxy groups by the substituents OR and OR, any hydrolyzable group that is suitable can be used to protect a free hydroxy group. Preferred groups

4 5
OR and OR ^ are lower alkoxy, benzyloxy and p-nitrobenzyloxy.

Preferred starting compounds for the invention

12 3

proper procedures are those in which R, R and R Lower alkyl, especially methyl, ethyl and isobutyl.

When R ^ is a straight or branched chain unsaturated Represents hydrocarbon radical with 2 to 8 carbon atoms, preferred groups are:

2-hexenyli 5-ethyl-4-hexenyl; 5-ethyl-2-hexenylj 2,4-hexadienyl; 3-methyl-j5-pentenylj 4-methyl-j5-pentenylj 3-methylen-4-pentenylj 5-methyl-2,4-pentadiejiyl; 3-ethyl-4-methyl-pentenyl; 2-octenyl; 5-heptenyl 2,3-dimethyl-3 »- pentenylj 2,3,4-trimethyl-2,4-pentadienylj 4-methyl-5-methylene-4-pentenylj 4-hexenyl; 4-methyl-2,4-pentadienyl; 5-methyl-4-hexenyl and 5-ethyl-3-hexenyl. Among these groups, 4-methyl-j5-pentenyl is particular preferred.

The compounds of the formula I are known compounds with valuable aroma and / or fragrance properties. They are therefore valuable ingredients in the manufacture of perfumes and perfumed products and / or Flavorings for food and beverages. Preferred compounds which can be prepared according to the invention are citral, Ethyl citral and isobutyl citral.

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-S-

The present invention also relates to the starting materials of the formulas II, V, VII and IX, as well as Process for their manufacture.

According to the invention, compounds of the formula I are prepared by heating a compound of the formula II to a temperature of 100 to 230.degree. The reaction does not require any solvent, but it can be carried out in an inert organic solvent. The usual inert organic solvents are suitable, solvents such as aliphatic or aromatic hydrocarbons, for example cyclohexane, octane, toluene and xylene, are preferred. The temperature of 100 to 230 ° must be maintained for at least J5 minutes. The reaction time is generally J> minutes to 20 hours, but can also be extended beyond this time. During the reaction, in addition to the compound I, the compound V, which is an intermediate, can also be detected in the reaction mixture. However, the compound V is also converted into compound I by prolonged heating of the reaction mixture to a temperature of 100 to 230 ^{° C.} Otherwise, the conversion of compound V into compound I takes place in the same way as the conversion of compound II into compound I.

On the other hand, the compound I can be obtained by pyrolysis of a compound of the formula VII

C = CH - CH _0-0 - CH - CH = C - CH R ² - " ²

_o _ ₀

R ¹ VII

or a compound of the formula

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C. = CH - CH ₀ - O - CH - O - CH ₀ - CH = C ² | ²

CH

Il l

C - R I

1 2 "5 4

wherein R, R, Br and OR are those given above

Have meanings
take place.

The pyrolysis of the compounds of the formulas VII and IX or of mixtures thereof to give compounds of the formula I can be carried out in be carried out in a known manner. The pyrolysis can be carried out in the liquid or gas phase on the compounds of the formulas VII and IX isolated from the reaction mixture, as well as their mixtures as well as in the same reaction medium :, used to make these compounds , in the latter case it is only possible to work in the liquid phase.

In a preferred embodiment of the pyrolysis, a compound of the formula VII or IX is heated to a temperature of 120 to 10 ° C. If desired, it is carried out in the presence of a strongly acidic catalyst. Strongly acidic catalysts are p-toluenesulphonic acid, o-nitrobenzoic acid, 2,4-dinitrophenol and sodium hydrogen sulphate. If desired, the reaction medium can contain an acidic condensation agent, the usual acidic condensation agents, such as mineral acids, for example sulfuric and phosphoric acid or organic acids, such as acetic, difluoroacetic, trifluoroacetic acid, 2,4-dinitrophenol and o-nitrobenzoic acid, as well as Salts of these acids with metals of groups IA, HA, IB, HB, VIB _; VIIB and VIIIB of the periodic table, such as magnesium, aluminum, calcium, chromium, manganese, silver, cadmium, mercury

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silver, iron, cobalt and palladium. Alkali metal or ammonium salts of can also be used as acidic condensing agents Mineral acids and strong organic acids such as sodium hydrogen phosphate, sodium hydrogen sulfate or monosodium oxalate be used. Preferred condensing agents are mercury acetate, phosphoric acid and ammonium dihydrogen phosphate etc. It is also possible to use mixtures of several of these condensing agents. Is the boiling point of the solvent or the reaction mixture is essential below the pyrolysis temperature, the pyrolysis can be carried out under pressure in a closed vessel.

If the pyrolysis is carried out in the gas phase, so the compound of formula VII or IX is heated to a temperature of 200-400 °. This can be done by that one brings the compound under an inert gas atmosphere in a column heated to 200-400 °. This pillar can be a Contain a high melting point absorbent material, such as pumice stone or a solid alkali metal salt of a strong Acid, e.g., sodium dihydrogen phosphate.

The starting material of the formula II can be prepared in that at least 1 mole of a butadienyl ether the formula

= C - CH = CH -

I ₁

ir

l 4
where R and OR are as defined above,

with one mole of an alcohol of the formula

C = CH - CH ₀ OH IV

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2 3
wherein R and R have the meanings given above,

is reacted in the presence of an acidic condensing agent at a temperature of 40 to 10O ^{0 C.}

In general, it is convenient to use 2 to 5 moles of the To use compound III per mole of compound IV. The excess of the compound III can be used at the same time Serve reaction medium. On the other hand, larger amounts than 5 mol, for example 15 mol or more, of compound III can be used, which will be seldom, however, since the use of these large amounts does not have any additional advantages brings with it. If desired, the reaction medium can contain an additional inert organic solvent as a diluent. The usual inert ones come in organic solvents in question; preferred are aliphatic and aromatic hydrocarbons, such as cyclohexane, Octane, toluene and xylene. The reaction is carried out in the presence of a condensing agent, wherein the usual acidic condensation agents come into question, as they are in connection with the pyrolysis of compounds of formula VII or IX have been listed above. Preferred condensing agents are mercury acetate, Phosphoric acid or ammonium dihydrogen phosphate.

In general, the reaction of compounds of the formula III with compounds of the formula IV is carried out in the presence a buffer, it being possible to use the usual buffers. Preferred buffers are alkali metal salts of organic monocarboxylic acids, e.g., of aromatic acids such as benzoic acid and alkali metal salts of lower ones Alkanecarboxylic acids, e.g. sodium benzoate, sodium acetate or Sodium propionate, with sodium acetate being preferred. In a preferred embodiment of the implementation is a

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Mixture of a "condensing agent, such as mercury acetate with a buffer, such as sodium acetate used. The condensation of the compound II with the compound IV is carried out at a temperature of 40 to 10O ⁰ C. Care must be taken that the temperature does not ^{100 0 C} Exceeds, since otherwise a number of by-products are formed which reduce the yield of the compound of the formula I.

The isolation or separation of the compound of the formula II from the reaction mixture can be carried out in a manner known per se Way, e.g. by filtration and distillation. The insoluble part of the catalyst system can be removed from the reaction mixture simply by filtration. Where no additional solvent was used, the reaction mixture contains the compound of the formula II im 'Mixture with the compound of the formula III. These two compounds can easily be separated by vacuum distillation can be proceeded in the usual way. In addition to these two components, there is also an inert one If organic solvent is present, the compound of the formula II can be fractionated from the reaction mixture Distillation can be isolated.

By first preparing and isolating the intermediate of Formula II., The butadienyl ether can Formula III can be converted into compound I in high yield. It has surprisingly been found that In contrast to other processes for the preparation of compounds of the formula I, the unreacted butadienyl ether of the formula III recovered after isolation of the compound of the formula II and again with the compound IV to give the compound I can be implemented. Since the ether of the formula III is a relatively expensive material, this means Process variant a significant 'economic improvement

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in the preparation of compounds of the formula I from butadienyl ethers of formula III.

According to the invention, the compound of the formula V can be prepared by oxidation of a corresponding alcohol of the formula

H ₀ C = CH C CH C- = • CH

2 1

R ^ CH ₂ OH R ^X. VI

12 "3

where R, R and J \ r are as defined above,

getting produced.

The usual methods known for the oxidation of an alcohol to the corresponding aldehyde can be used. Preferred oxidizing agents are manganese dioxide, chromic acid or Jones ¹ reagent. The temperature and pressure conditions for these reactions are not critical, ie the reaction can be carried out at room temperature under atmospheric pressure. In general, one of the inert organic solvents known per se is used, preferably diglyme or chlorinated hydrocarbons, such as methylene chloride and chloroform.

It has already been mentioned that the aldehyde of the formula V is used as an intermediate in the preparation of the compound I arises from the compound II under the reaction conditions given above.

The compound of the formula VII can be prepared by reacting a butadienyl ether of the formula

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-XL-

= C - CH = CH - OR

1
wherein R and OR are as defined above

with an alcohol of the formula

C = CH - CH OH IV

O -ζ,

wherein R and R ^ have the meanings given above,

be prepared in the presence of a complex palladium chloride or palladium acetate catalyst, wherein as a complexing agent an organic, nitrogen-containing compound, e.g. a nitrile, an organic amine or a Pyridine derivative, can be used. Preferred catalysts are dichloro-bis-benzonitrile-palladium and Dichloro-o-phenanthroline palladium. Implementation is at Temperatures from -55 ° to 50 ° carried out. The presence an additional solvent is not necessary. An excess of the compound III can be used as the reaction medium to serve. On the other hand, it is desirable that the reaction be carried out in the presence of an inert organic solvent the usual ones, such as aliphatic or aromatic hydrocarbons, e.g. Octane, toluene, xylene or benzene.

In another embodiment, compounds of the formula VII are prepared by reacting an alcohol of the formula

= CH - CH ₀ OH · IV

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2 "3
where R and R ^ are as defined above,

with an acetal of the formula

OR ⁴ IUC - C = CH - CH

X _0R 5 viii

1 H- where R 'and OR are as defined above

5
and OR represents a hydrolyzable protected hydroxy group,

at temperatures from 50 ° to 120 ⁰ C, in the presence of an acidic condensing agent. This reaction is carried out in the same way and under the same conditions as the reaction of compounds IV with compounds III, with the

Except that temperatures of 50 ° are applied up to 120 ⁰ C. In a preferred embodiment, mercury acetate is used as the condensing agent and sodium acetate is used as the buffer.

When a compound of the formula IV is reacted with a compound of the formula VIII, the compound of the formula VII in admixture with a small amount of a compound of the formula

X = CH - CH ₀ - 0 - CH - 0 - CH ₀ - CH - C 2 2

₀ 0 CH 0 CH ₀ 2 ι 2

" 1

C-R IX

] 2 "5
where R ", R and R ^ are as defined above,

obtain.

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The compound VII can be separated off from the compound IX in a manner known per se, for example by fractional distillation. Both compounds can be prepared in the same way by pyrolysis, as described above, be converted into the compound I, i.e. compound VII does not have to be isolated from the reaction mixture and removed from Compound IX can be separated.

On the other hand, the compound of formula IX can be prepared by converting at least 2 moles of one. Alcohol of formula

C = CH - CH OH IV

2 3

wherein R and R W. are as defined above,

with one mole of an aldehyde of the formula

- C = CH - CHO

wherein R is as defined above.

In general, about 2 to 10 moles of the compound IV per mole of the compound X are used. If necessary More than 10 moles of compound IV per mole of compound X, for example 30 and more moles, can be used. The reaction can be carried out in the presence of a condensation and of a dehydrating agent. The condensing agents known per se come into question, such as Mineral acids, e.g. dry HCl, sulfuric acid. Or Phosphoric acid, organic acids such as p-toluenesulfonic acid, o-nitrobenzoic acid or 2, ^ j, 6-trinitrophenol and

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Ammonium, alkali metal and alkaline earth metal salts of strong acids such as calcium sulfate, sodium dihydrogen phosphate, Ammonium sulfate, ammonium nitrate or ammonium chloride. Compounds like calcium sulfate or calcium chloride can can be used both as a condensation agent and as a dehydrating agent. As a dehydrating agent those known per se are also suitable, such as molecular sieves, sodium sulfate, magnesium sulfate, calcium chloride, etc. The molecular sieves contain metal oxides which are acid anhydrides. In view of this fact, For example, the molecular sieves can be used both as dehydrating agents and as condensing agents. A solvent must be used in the preparation of compounds of Formula IX. An excess of one Compound of formula III can be used as the reaction medium. On the other hand, the implementation in the present one of the usual inert organic solvents, be carried out, for example in the above-mentioned aliphatic or aromatic hydrocarbons. The conditions for the reaction temperature and the pressure are not critical, so that the reaction can be carried out at room temperature and under atmospheric pressure, but also higher or lower temperatures can be applied. The preferred temperature for this reaction is usually between 0.degree. And 80.degree.

Without the need to isolate it from the reaction mixture, the compound of the formula IX be converted into the compound of formula I. On the other hand, the compound of the formula IX can be obtained from the reaction mixture isolated in a manner known per se, for example by fractional distillation under reduced pressure and on the The above-described methods can be converted into the compound I by pyrolysis.

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The following examples illustrate the invention.

example 1

3.0 g Added mercury acetate and 5.0 g sodium acetate. The resulting two-phase system was heated to 45 ° C. for 4 hours under an argon atmosphere. Then the residue, essentially pure sodium acetate, was removed by filtration. A low-boiling fraction of 24 g consisted of about 90% methyl- (3-methyl-1,3-butadienyl) -ether, mixed with a little 3-methyl-2-buten-1-ol. A second fraction contained 12.2 g of 3-methyl-2-butenyl (3-methyl-1,3-butadienyl) ether (purity 92-9W, bp _n = 60 °. The low-boiling fraction was Y g of methyl (3-methyl-1,3-butadienyl) ether, 12.0 g of prenol, 3% mercury acetate and 3.0 g of sodium acetate were added The mixture was heated as described above and yielded 12.1 g of 3 -Methyl-2-butenyl- (3-methyll, 3-t> ^u tadienyl.) - ether together with a low-boiling fraction of 23 g of methyl (3-methy1-1,3-butadienyl) ether (purity 90 $) and a little prenol, which in turn was mixed with 7 g of methyl (3-methyl-1,3-butadienyl) ether, 12.0 g of prenol, 3 * 0 g of Queekilver acetate and 3.0 g of sodium acetate, and yielded again 12.1 g of 3-methyl-2-butenyl- (3-methyl-1,3-butadienyl) -ether. The total yield of 3-methyl-2-butenyl- (3-methyl-1,3-butadienyl) -ether was 50 $ based on prenol and 92; 1> based on methyl (3-diethyl-1,3-butadienyl) ether.

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Example 2

A mixture of 30 gl, l-dimethoxy-3-rnethyl-2-butene _J 15 g of prenol, 1.3 S sodium acetate and 4.0 g of mercuric acetate was heated l6 hours under argon atmosphere to 120 °. After cooling and filtering, vacuum distillation yielded some low-boiling products and 15 * 8 g of l-methoxy-3-methyl-1- (3-methyl-2-butenyloxy) -2-butene and, in a later fraction, 1.2 g 1-bis (3-n-ethyl-2-butenyloxy) -3-methyl-2-butene.

Example 3

A mixture of 2.0 g of prenol and 5 * 0 g of methyl (3-methyl-1-1,3-butadienyl) ether, cooled to -78 ° under an argon atmosphere 100 ml dichlorobis (benzonitrile) palladium (II) added.

The reaction mixture was allowed to warm to -15 ° with stirring, a sudden change in color from yellow to brown occurring and, by gas chromatographic analysis, the formation of l-methoxy-3-methyl-l- (3-methyl-2-butenyloxy) -2 -but was detectable. The mixture was kept at -15 ° for 45 minutes and 300 mg of triphenylphosphine were added to convert the palladium complex into dichlorobis (triphenylphosphine) palladium- (II), which was then removed by filtration. Vacuum distillation of the filtrate afforded 1.4 g of l-methoxy-3-methyl-l- (3-methyl-2-butenyloxy) -2-butene, bp. _{Χ Q} = 80-85 °.

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Example 4

'A mixture of 30 g of 3-methyl-2-butenal, 70 g of prenol, 0.70 g of ammonium nitrate and 20 g of Linde 4A molecular sieve (a mixture of 1 part by weight of sodium oxide, 1 part by weight of aluminum oxide and two parts by weight of SiO * H 0) was stirred at 25 ° and gas chromatographic analysis showed the formation of 1,1-bis (3-methyl-2-butenyloxy) -3-methyl-2-butene established. After 72 hours, 20 g of sodium carbonate was added, the solution became 20 minutes stirred and then filtered. Vacuum distillation of the filtrate yielded 27 g of low-boiling products (a mixture of prenol and 3 ~ methyl-2-buten-1-al in a volume ratio of about 5? l) and 31 * 2 g of 1,1-BiS- (J-methyl-2-butenyloxy) -3-methyl -2-butene. The distillation residue was 3 g.

Example 5

IV g of (3-methyl-2-butenyl) - (3-methyl-1,3-butadienyl) ether were heated to 200 ° for 30 minutes in an evacuated, sealed tube. Vacuum distillation of the reaction mixture yielded 12 - ¹ I- g citral (purity 95 $, 88 $ yield), bp _{Q χ} = 60 °..

Through regular gas chromatographic analysis of samples that are heated to 180 ° at regular intervals 0.200 ml sample was taken during 5 minutes found that the (3-methyl-2-butenyl) - (3-methyll, 3-butadienyl) ether initially in 2-isopropenyl-3,3-dimethyl-4-pentenal was convicted.

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Example 6

A solution of 1,1-bis (3-methyl-2-butenyloxy) -3-methyl-2-butene (10.0g, 4L, 3mm oil) and 2,4-dinitrophenol (0.17 g * 1 * 01 mmol) in 300 ml of toluene was 45 hours heated under reflux. After cooling to room temperature the toluene solution was saturated four times with 50 ml NaHCO-r solution and twice with 100 ml. Saturated sodium chloride solution washed and dried with anhydrous sodium acetate. The toluene was made by distillation at a pressure of 20 mm Hg and an oil bath temperature of 55-60 °. The residue was with Diluted diethyl ether and washed three times with saturated aqueous sodium chloride solution. The etheric phase was then dried over anhydrous sodium acetate, concentrated under reduced pressure and run on a short Column distilled. Pure citri 'was obtained.

Example 7

A solution of 3j17 S pyridine in 50 ml of methylene chloride 2.0 g of chromium trioxide were added; the mixture was stirred for 15 minutes at 25 ° and then with 0.510 g 2-isopropenyl-3 * 3-dirnethyl> -4-penten-1-ol added. That The reaction mixture was stirred for 10 minutes, the methylene chloride decanted and the residue with ether washed. The combined organic phases were washed three times with 35 ml of 5% aqueous sodium hydroxide solution 35 ml 5 # aqueous HCl, 35 ml 5% sodium bicarbonate solution and 35 ml of saturated aqueous sodium chloride solution washed, dried over anhydrous magnesium sulfate and concentrated under reduced pressure. distillation of the residue under reduced pressure gave 0 * 375 g of 2-isopropenyl-3-dimethyl-4-penten-1-al, bp ..., - =

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80-85 °; V _co = 1720 cm " ¹ .

Example 8

1,1-bis (3-methyl ~ 2-butenyloxy) -3-methyl-2-butene was converted into citral by pyrolysis under reduced pressure.

The apparatus used in the pyrolysis consisted of a vertical cylindrical glass tube (diameter 25 now, Length IJO cm), surrounded by an asbestos-clad steel heating jacket and connected to a dropping funnel that is under pressure equalization, so that the connection is made drop by drop could be abandoned on the pillar. The pyrolysate was at the bottom of the column in a 1000 ml three-necked flask caught. The template was cooled in a dry ice-acetone bath and contained approximately 100 ml of frozen aqueous NaHCO - solution. The template was over two dry ice-acetone cold traps connected to a vacuum pump. The pyrolysis temperatures were between the steel · and glass jacket of the pyrolysis apparatus measured by thermocouples, so it is not necessarily the real column temperature corresponded.

Sodium dihydrogen phosphate grains dried under vacuum at 220 ° were mixed with an equal amount of pumice stone (4-8 mesh) and added to the column, the was heated to 325 ° overnight under vacuum.

Once the column is heated to 325 °, it can can be used repeatedly, with air having no adverse effect provided that it cannot cool. However, if the column cools down, the packing solidifies to a solid mass that can no longer be removed, but which can

409839 / 103U

is still catalytically active.

17 * 5 gl, l-bis (3-methyl-2-butenyloxy) -3-methyl-2-butene were added via the dropping funnel to the column heated to 350 ° and under a pressure of 2 mmHg for β hours. When the pyrolysis had ended, the pyrolysate (16.3 g) was heated to 25 ° and extracted twice with 200 ml of diethyl ether. The ethereal extract was washed with saturated aqueous sodium chloride solution, dried over sodium carbonate, filtered, concentrated on a steam bath and distilled over a Vigreaux column. 4.1 g of citral were obtained.

Example 9

A mixture of 2.0 g of l-methoxy-3-methyl-l- (3-methyl-2-butenyloxy) -2-buteil, 20 mg of NaHpFO ₂ , and 10 ml of heavy mineral oil with a boiling point above 350 ° was deaerated, by bubbling argon gas therethrough for 10 minutes, and then heating to 200 ° for 50 minutes. The yellow reaction mixture was then cooled to room temperature and 100 mg NaHCO- was added. Vacuum distillation yielded 1.2 g of low-boiling products and 0.70 g of citral.

Example 10

3 ml (3-methyl-2-butenyl) - (3-methyl-1,3-butadienyl) ~ ether were heated under an argon atmosphere for 3 minutes in an oil bath to 180 ° and then by placing in ice quickly cooled to 25 °. The pyrolysate was then subjected to preparative gas chromatography, whereby 2-isopropenyl-3,3-dimethyl-4-pentenal was obtained.

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Example 11

200 μl of 2-isopropenyl-3, j5-dimethyl-4-pentenal were heated in an oil bath for 10 minutes to 180 ° in an evacuated tube closed under vacuum and converted into citral with a purity of 85 $.

Example 12

60 g of powdered 5A molecular sieve (containing 0.2 parts by weight of sodium oxide, 0.8 parts by weight of calcium oxide, 1 part by weight of aluminum oxide and 2 parts by weight of SiO _p * HpO) were added. After about 40 minutes the original exothermic reaction had subsided, the water bath was removed and stirring was continued at room temperature. The reaction was followed by gas chromatographic analysis and when it was complete the reaction mixture was filtered. The residue was washed carefully, six times with 150 ml of hexane The combined filtrates were concentrated under reduced pressure (120 °, 20 mmHg) and yielded 135.75 g of a pale yellow liquid.Distillation at a pressure of 17 mmHg and an oil bath temperature of 60-75 ° yielded 28.95 g Prenol and Prenal (8.1 parts by volume). Further distillations at a pressure of 0.50 mmHg and a bath temperature of 45-55 ° yielded an additional 11.19 g of prenol. Short path distillation of the remainder (77.24 g) under a pressure of 0.015 mmHg mercury and at an oil bath temperature of 95-97 ° ' 15A yielded 1.1-bis (3-methyl-2-butenyloxy) -> methyl-2-butene as a clear liquid (purity according to gas chromatography 9 $ 5 or above). Yield: $ 97 based on prenol

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or iyß>, based on Prenal.

Example 13

57 g of powdered calcium sulfate were added to a mixture of 50 g of prenol and 13 g of prenal degassed with nitrogen. The mixture was. Stirred for 100 hours at room temperature. It was then filtered, and the residue was carefully washed four times with 100 ml of anhydrous diethyl ether. The combined filtrates were concentrated (pressure 20 mmHg, bath temperature 26 °) and distilled below 20 mmHg and a bath temperature of 65-70 °. 50.76 g of prenol and 2.9 g of prenal were obtained. Short-path distillation of the residue (25 * 54 g) at a pressure of 0.015 mmHg and a bath temperature of 95-97 ° yielded 25.0 g of 1,1-bis- (3-methyl-2-butenyloxy) -3-methyl-2-butene in In the form of a clear liquid of at least 95 ° ■ purity (gas chromatography). Yield: 9k% , based on prenol or $ 88, based on prenal.

Example 14

A mixture of ΙΟ, .Ο g l, l-bis (3-methyl-2-butenyloxy) -3-methyl-2-butene, 300 ml of toluene and 0.17 g of 2,4-dinitrophenol were heated to reflux for 45 hours, then cooled to room temperature and four times with 50 ml of saturated aqueous sodium bicarbonate solution and twice washed with 100 ml of saturated aqueous NaCl solution. The toluene solution was poured over anhydrous sodium acetate dried and the toluene by distillation under a pressure of 20 mmHg and at a bath temperature of 55-60 ° away. The residue was diluted with diethyl ether and three times with 50 ml of saturated aqueous NaCl solution washed. The ethereal solution was

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dried free sodium acetate, concentrated under reduced pressure and distilled through a short column. 3.9 g of pure (98 $) citral were obtained, bp _Q ^ = 51-54 ° (61 $).

Example 15

■ - A mixture of 30.0 g of 1,1-bis (3-methyl-2-butenyloxy) -3-methyl-2-butene, 500 ml of toluene and 0.5 g of 2,4-dinitrophenol were refluxed under a nitrogen atmosphere for 32 hours heated. The mixture was then cooled to room temperature and three times with 100 ml of 0.1 N aqueous NaOH and twice washed with 100 ml of saturated NaCl solution. The united aqueous solutions were extracted with 100 ml. diethyl ether. The ether extract was saturated aqueous with 50 ml NaCl solution and then combined with the toluene solution. The combined organic solutions were with Treated activated charcoal, dried over magnesium sulfate and concentrated. 25.4 g of a liquid were obtained which after short-path distillation at 0.3 mmHg yielded two fractions:

1. 3 * 9 g, bp 47-51 °, included! $ 88 citral and low-boiling component;

2. 10.6 g ,. Bp. 51-53 °, containing 96% citral and low-boiling components.

The distillation residue contained small amounts of citral and 1,1-bis (3-methyl-2-butenyloxy) -3-methyl-2-butene. The fractions obtained by the distillation were again distilled under a pressure of 0.30 mmHg and yielded 12.9 ε of pure ($ 96) citral, b.p. = 52-5 ° ($ 67).

.409839 / 1030

Example l6

A mixture of 5 * 5 gl, l-dimethoxy-3-methyl-2-butene, 10.0 g prenol and 0.40 g 2,4-dinitrophenol was degassed with nitrogen and stirred at room temperature for J6 hours. The mixture was then diluted with 100 ml of hexane, washed three times with 100 ml of 1.0 N aqueous NaOH and twice with 100 ml of saturated aqueous NaCl solution. The washing solutions were extracted again with 50 ml of hexane. The combined hexane phases were dried over sodium sulfate, concentrated and gave 9 * 0 g of a crude product. 8.3 S of this yielded 1.48 g of prenol after distillation under a pressure of 20 mmHg and at a bath temperature of 55-60 °. Further distillations, initially under a pressure of 0.20 mmHg, yielded 2.43 g of 1-methoxy-3-methyl-1 - (3-methyl-2-butenyloxy) -2-butene, b.p. 40-45 ° , and

υ, d.

finally 3.29 g of l-bis (3-methyl-2-butenyloxy) -3-methyl-2-butene, b.p. _Λ = 70-75 °.

u up

Example 17

A mixture of 5.72 g (0.0132 mmol) of l-methoxy-3-methyl-l- (3-methyl-2-butenyloxy) -2-butene, 0.0138 moles 1,1-bis (3-methyl-2-butenyloxy) -3-methyl-2-butene, 40 ml Toluene and 0.030 g of 2,4-dinitrophenol were refluxed for 80 hours, cooled to room temperature and then washed three times with 20 ml of 2N aqueous NaOH and once with 20 ml of saturated aqueous NaCl solution. The toluene solution was treated with activated charcoal, dried over sodium sulfate, concentrated and the short path distillation with subjected to a pressure of 0.25 mmHg and a bath temperature of. 3 * ^ 9 g of a yellow liquid were obtained, which was distilled again under a pressure of 0.4 mmHg and yielded 2.48 g of citral, b.p. = 59 ~ 6l °

0.4-

409539/1030

Example l8

A mixture of 1.90 g of Prenal and 9 * 24 g of geraniol and nerol was degassed with nitrogen and mixed with 5 g of powdered molecular sieve-5A (as described in Example 12). The mixture was then stirred at room temperature for 15 hours and filtered. The residue was carefully washed three times with 15 ml of anhydrous diethyl ether. The combined filtrates were concentrated under a pressure of 20 inmHg at 26 ° and yielded 10.0 g of a colorless liquid. The unreacted geraniol / nerol was removed by distillation under a pressure of 0.10 mmHg and at an oil bath temperature of 70-75 °. There remained 5.8 gl, l ^ is- (3.7 _T dimethyl-2,6-octadienyloxy) -3-methyl-2-butene, which corresponds to a conversion of $ 68 and a yield of $ 79, based on the Alcohol, corresponds.

Example 19

A mixture of 17 * 05 g prenol and 5 * 5 g crotonaldehyde was degassed under nitrogen, with 11.8 g of powdered molecular sieve (as described in Example 12) added and stirred for 46 hours at room temperature. It was then filtered and the residue carefully washed with hexane washed. The combined filtrates were concentrated under reduced pressure (20 mmHg and ^ 0 °) and yielded 18.9 g a light yellow liquid, which after distillation under a pressure of 20 mmHg and a bath temperature of 65-70 ° 9.0 crotonaldehyde / prenol (1: 5) and 7.4 g pure l, l-Bis - (> - m.ethyl-2-butenyloxy) -2-butene gave what a Conversion of $ 68 and a yield of $ 97 * based on Prenol or $ 94, based on crotonaldehyde.

409839/1030

Example 20

A mixture of 2.0 g of 1,1-bis- (^ - oxy) -2-butene, 20 ml of toluene and 0.110 g of 2,4-dinitrophenol was refluxed for 88 hours, cooled to room temperature and with 15 ml of 2N three times NaOH and washed once with 15 ml of saturated aqueous NaCl solution. The toluene solution was dried over sodium sulfate and concentrated. The residue was subjected to short-path distillation at 0.4 mmHg and an oil bath temperature of 90 ° and yielded 0.4 l g of 7-methyl-2,6-octadienal, which was subjected to fractional distillation, bp "= 82-84 ° (Yield 0.32g).

409839/1030

Claims (1)

Claims 1. Process for the preparation of aldehydes general formula C = CH - CH ₀ - CH ₀ - C = CH - CHO wherein R is lower-alkyl, R is lower-alkyl and R- ^ hydrogen, lower-alkyl or a straight or branched chain aliphatic hydrocarbon radical. with 2 to 8 carbon atoms and or represent 2 double bonds, characterized in that either a) a compound of the formula C = CH - CH ₀ - O - CH = CH - C = CH, i. ' . or ' _D 3 Xt H ft <"<TT ri riTT r \ / TLT ~ \ s = UJtI - L> ■ * · Oil "V = Kstl _n 2 1 R CHO R 12 "5 wherein R, R and R ^ are those given above Have meanings
heated to a temperature of 100-200 °, or 409839/1030 b) an acetal of the formula C = CH - CH ₀ - O - CH - CII = C · ² II I 4 1 VIT OR R ^{νΧΧ X} C = CH - CH - 0 - CH - 0 -CH - CH = C ^ ' I ti CH "1 IX C-R CH 12 3 wherein R, R and R are those given above 4th
Have meanings, and OR has a hydrolysing represents bare, protected hydroxyl group, pyrolyzed. 2. The method according to claim 1, characterized 12 3 4
draws that R, R, R and R are each methyl. j5. Process according to claim 1 or 2, characterized characterized in that a compound of formula II or V oneine Temperature of 100-230 ° is heated. 4. The method according to claim 1 or 2, characterized characterized in that the pyrolysis of the acetal of the formula VII or IX in the liquid phase at a temperature of 120 to 230 ° is carried out. 5. The method according to claim 1 or 2, characterized in that the pyrolysis of an acetal of the formula VII or IX is carried out in the gas phase at a temperature of 200 to 400 °. 409839/103 0 6. The method according to claim 4 or "5 * thereby characterized in that the pyrolysis is carried out in the presence of an acidic catalyst. 7. The method according to claim 5 *, characterized in that that the pyrolysis is carried out in the presence of a solid acidic alkali metal salt of a strong acid will. 8. The method according to claim 1, characterized in that the starting material of formula II by Implementation of at least one mole of a dutadienyl ether of the formula = C - CH = CH - OR 1 4
wherein R and OR are those given above Have meanings
with one mole of an alcohol of the formula = CH - CH ₀ OH IV 2 3 wherein R and R have the meanings given above, is prepared in the presence of an acidic condensing agent at a temperature of 40 to 100 °. Λ09839 / 1030 9. The method according to claim 8, characterized in that that the reaction mixture is 2 to 5 moles of the butadienyl ether contains per mole of alcohol. 10. The method according to claim 8 or 9, characterized in that the reaction is carried out in the presence of a buffer. 11. The method according to any one of claims 8 to 10, characterized in that the condensing agent is mercury acetate and the buffer is sodium acetate. 12. The method according to any one of claims 8 to 11, characterized in that one l-methoxy-3-methyl-butadiene with 3-methyl-2-buten-l-ol. 13. The method according to claim 1, characterized in that that the starting material of the formula V by oxidation of a corresponding alcohol of the formula TT f / -irr
H ₂ C - CH I.
- C
■ - CH - C = CH
■ YT CH ₂ Rl
OH wherein R, R ² and ¥? the above specified Meanings to have, manufactures. Ik. Method according to claim I3, characterized in that 12 "5
indicates that R, R and Tr each represent methyl. 409839/1030 15. The method according to claim 1, characterized in that that the starting material of the formula VII by reacting a butadienyl ether of the formula H ₂ C = C - CH = CH - OR ^ I ₁ III ι Κ wherein R and OR have the meanings given above,
with an alcohol of the formula C = CH - CH OH IV 2 3 where R and Br are as defined above, at a temperature of -35 to 50 ° in the presence of a complex palladium chloride or palladium acetate catalyst. l6. Method according to claim 15 *, characterized in that that the palladium catalyst is complexed with an organic, N-containing ligand. 17 · The method according to claim 15 or 16, characterized in that 12 3 4 indicates that R, R, R and R each represent methyl. 18. The method according to claim 1, characterized in that the starting material of the formula VII by reaction of an alcohol of the formula 409839 / 103U C = CH - CH ^ OH - IV 2 3
wherein R and R are as defined above, with an acetal of the formula H_, C - C = CH - CHC r - VIII 1 4
wherein R and OR are those given above 5
Have meanings, and OR has a hydrolysing represents bare protected hydroxy group, at a temperature of 50 to 120 ° in the presence of a acidic condensing agent. 19. The method according to claim 18, characterized in that that the reaction is carried out in the presence of a buffer. 20. The method according to claim 18 or 19 * thereby characterized in that the condensing agent is mercury acetate and the buffer is sodium acetate. 21. The method according to any one of claims 18 to 20, marked h
Represent methyl. 12 ^ 4 5 characterized in that R, R, R, R and R, respectively 22. The method according to claim 1, characterized in that the starting material of formula IX by Implementation of at least 2 moles of an alcohol of the formula 409839 / T03U C = CH - CH OH IV 2 "3 where R and R ^ are as defined above, with one mole of an aldehyde of the formula HC - C = CH - CHO where R has the meaning given above, in the presence of a condensation and a dehydration · is made by means of. 25 «The method according to claim 22, characterized in that that the condensing agent is an ammonium salt of a strong acid. 2h. Process according to claim 2J>, characterized in that the salt is ammonium nitrate. 25 · method according to one of claims 22 to 24, characterized in that the dehydrating agent is a molecular sieve. 26. The method according to claim 22, characterized in that calcium sulfate as both condensation is used as a dehydrating agent. 27. The method according to any one of claims 22 to 26, 12 "5 characterized in that R, R and R are each methyl represent. 409839 / 103U