DE19520103A1 - Process for the preparation of alkyl-substituted butenols - Google Patents

Abstract

Alkyl-substituted butenols of the general formula (I) R<1>-CH2-CH=CR<2>-CH2OH in which R<1> is a saturated or olefinically unsaturated alkyl or cycloalkyl group with 4 to 16 C atoms, which may be substituted by an alkyl, cycloalkyl, aryl or alkaryl radical, provided that this component has 12 C atoms at the most, and R<2> is hydrogen or an alkyl group with 1 to 6 C atoms, may be produced in large quantities and with great purity by the reaction of aldehydes of the formula (II) R<1>-CH2-CHO in which R<1> has the same meaning as in formula (I), with the corresponding low aldehydes and the subsequent reduction of the unsaturated aldehyde thus obtained, if: i) the aldol condensation is performed in an inert organic solvent, and ii) the unsaturated aldehyde is reduced in the presence of a possibly calcined copper-zinc contact.

Description

Field of the Invention

The invention relates to a process for the preparation of alkyl substitutes ten butenols by reducing the corresponding aldehyde precursor in counter waited for copper-zinc contacts.

State of the art

Many natural fragrances are completely unrelated to their needs sufficient amount available. Especially from a perfume point of view The sandalwood oil is valued and valuable. It is caused by water vapor Stillation made from the heartwood of the sandal tree, a tropical one Semi-parasite that occurs in India and Malaysia. Heartwood appears after about ten years and only begins to grow in twenty year old trees train faster. Fully grown trees grow to ages 30 to 60 years cleared because the roots are particularly rich in fragrant Heartwood are [cf. E.T. Morris, Dragoco Report 1983 (30), 40). It is therefore understandable that the fragrance research is constantly trying, ge to develop suitable substitutes for natural sandalwood oil.  

The main focus in the development of suitable substitutes for natural Sandalwood oil has R.E. Naipawer outlined in a review [in: B.M. Lawrence, B.D. Mookherjee, B.J. Willis (ed.): "Flavors and Fragrances: A World Per spective "; Elsevier Publishers, Amsterdam 1988). In this review, un ter shown that campholenylderiva since the mid-1970s an important role among synthetically produced fragrances represent with sandal scent. An essential role in this access to synthetic sandal scents played the fact that Cam pholenaldehyde, the synthesis on which the compounds discussed are based building block that is easily accessible from alpha-pinene.

2-alkyl-4- (2,2,3-trimethylcyclopent-3-enyl) -but-2-en-1-ole, henceforth as Called sandelole, are coveted fragrances with a distinctive sandal fragrance.

JP-A2-55 / 036423 (cited from Chem. Abstr. 93 / 094886p) describes a ver drive to manufacture such a sandelol. Accordingly, alpha campho lenaldehyde (B) in the presence of sodium hydroxide as a basic catalyst implemented with propionaldehyde (CH₃-CH₂-CHO).

The unsaturated alde formed during this mixed aldol condensation hyd (C) was isolated in a yield of 73.5%.

In a further step, this unsaturated aldehyde was finally (C) with Al [OCH (CH₃) ₂] ₃ reduced to the corresponding sandelol (A). The one there when the yield is achieved, 85% is given.

Description of the invention

The method for producing sandelol known from JP-A2-55 / 036423 (A) [with R CH₃] is capable of yield and economy not completely satisfied. There was therefore a need for an improved process for the preparation of the compounds (A) and analogous compounds in which the rest "Cy" are sown by another saturated or olefinically unsaturated, optionally substituted alkyl or cycloalkyl radical is replaced.

It has now surprisingly been found that alkyl-substituted butenols of the general formula (I),

R¹-CH₂-CH = CR²-CH₂OH (I)

wherein R¹ is a saturated or olefinically unsaturated alkyl or cyclo is alkyl group with 4 to 16 carbon atoms, which may be replaced by an Al alkyl, cycloalkyl, aryl or alkaryl radical can be substituted - with the Provided that this substituent has a maximum of 12 carbon atoms - and R² what mean hydrogen or an alkyl group with 1 to 6 carbon atoms, in high Yields can be produced if the aldol condensation of aldehydes of the formula (II)

R¹-CH₂-CHO (II)

wherein R¹ has the same meaning as in formula (I), and the corresponding low aldehyde in an inert organic solvent and the unsaturated aldehydes obtained in the presence of a counter if necessary, calcined copper-zinc contact reduced.

The present invention therefore relates to a process for the preparation position of alkyl-substituted butenols of the general formula (I),

R¹-CH₂-CH = CR²-CH₂OH (I)

wherein R¹ is a saturated or olefinically unsaturated alkyl or cyclo is alkyl group with 4 to 16 carbon atoms, which may be replaced by an Al alkyl, cycloalkyl, aryl or alkaryl radical can be substituted - with the Provided that this substituent has a maximum of 12 carbon atoms - and R² what mean hydrogen or an alkyl group having 1 to 6 carbon atoms, by Um setting of aldehydes of the formula (II)

R¹-CH₂-CHO (II)

wherein R¹ has the same meaning as in formula (I), with the corresponding low aldehydes and subsequent reduction of the resulting saturated aldehydes, the aldol condensation being carried out in an inert orga African solvent and the reduction of unsaturated alde hyde in the presence of an optionally calcined copper-zinc contact carries out.

The inventive method has compared to the conventional Technology the advantage that intermediate and valuable products in high purity and can be obtained in almost quantitative yield.

Suitable inert organic solvents are, in particular, nonpolar solvents form an azeotrope with water. Examples of suitable solvents are Toluene, xylene, benzene, cyclohexane and methylcyclohexane.

In a special embodiment of the invention, catalysis is used the aldol condensation ammonium salts of an organic acid.

Propionaldehyde is preferably in 2.5- to 10-molar excess - bezo gene on the aldehyde (II) - used. Propionalde is used in particular hyd in a 2.5 to 3.5 molar excess.

As already said, the Al Dol condensation preferably in the presence of an ammonium salt of an orga African acid performed. The type of acid is not critical in itself table. It does not matter whether the ammonium salt as such or whether it is used during the reaction - for example from an amine and an organic acid - is formed in situ. Examples of suitable ones Ammonium salts are: benzyltrimethylammonium hydroxide, piperidinyl acetate, Pyrrolidinium acetate, ammonium acetate, dimethylammonium pyridinyl acetate, Mor pholine acetate, Lewatit 11600 (activated with acetic acid), piperidinylfor  miat, N, N-tetraacetylethylenediamine, N, N-diacetylethylenediamine, dibutyl ammonium acetate and piperidinyl propionate. The concentration of the catalytic converter tors is preferably in the range of 0.001 to 20 mol%, in particular 0.5 to 10 mol% - based on the aldehyde (II) used.

In a further preferred embodiment of the present invention R 1 in general formula (I) represents 4- (2,2,3-trimethylcyclo pent-3-enyl) residue.

The inventive method can at temperatures of 20 to 150 ° C. be performed. It is particularly preferred to use a reaction temperature temperature in the range of 40 to 120 ° C.

The copper-zinc cone to be used in the context of the present invention clocks are known from the prior art. You will be according to DE-A-42 42 466 prepared by using aqueous solutions containing water-soluble copper (II) and zinc (II) salts with alkali carbonate ver bindings up to a pH of 6 to 10 added, the resulting low blow separates and dries, the dried catalyst at temperatures calcined from 400 to 600 ° C over a period of 1 to 60 minutes and then brings the calcined catalyst into pieces. In the way look at further details of the production of the copper-zinc contacts be expressly on page 3, lines 13 to 34 of said DE-A-42 42 466 referenced.

The following examples serve to illustrate the invention and are not to be understood as restrictive.

Examples 1. Substances used 1.1. for aldol condensation

Alpha-campholenaldehyde: 85% (Glidco)
Propionaldehyde: 98% (from Riedel-de Häen).

KF on Al₂O₃: 240 g of basic aluminum oxide were in a 50% strength in 320 g aqueous potassium fluoride solution suspended and then on rotation evaporator evaporated to dryness in a water jet vacuum. After that the The catalyst was dried for a further 4 hours at 130 ° C. and 50 mbar.

1.2. for the reduction of the unsaturated aldehyde

Sodium boranate: (from Janssen).

Copper-zinc catalyst: The copper-zinc catalyst used was ge according to example A) of DE-A-42 42 466 using copper (II) nitrate trihydrate, zinc (II) nitrate hexahydrate and sodium carbonate.

2. Implementation of the reactions 2.1. Aldol condensation example 1

Amounts used:
3.04 kg (20 mol) alpha-campholenaldehyde
4.64 kg (80 mol) propionaldehyde
400 g of basic aluminum oxide with 40% potassium fluoride
loaded.

Reaction:
1.5 kg of a mixture (molar ratio 1: 4) of campholenaldehyde and propionaldehyde were placed in a 10 liter glass reactor. Under nitrogen (5 l / h) ₁ vigorous stirring and cooling, 400 g of KF on Al₂O₃ were added in portions, the temperature of the reaction mixture being kept between 40 and 50 ° C. The remaining 6.2 kg of the aldehyde mixture were then metered in continuously with vigorous stirring and nitrogen at a metering rate of 2 liters per hour. The reaction was exothermic and was kept at 40 ° C by cooling. After the addition, the mixture was stirred at 50 ° C. overnight. The campholenaldehyde was then completely reacted.

Refurbishment:
The batch was pumped into a 2 l pressure filter to remove the catalyst and filtered under 5 bar of nitrogen. The filter cake was briefly washed with 0.5 l isopropanol. The crude product was transferred back into the reactor and about 270 g of organic phase and 22 g of water phase were distilled off at atmospheric pressure at bottom temperatures of up to 150.degree. The residue of 5.1 kg remaining in the reaction vessel was washed twice with 2 l of saturated sodium sulfate solution. The remaining 5 kg residue was further processed as a crude product (the content of 2-methyl- (2,2,3-trimethylcyclopent-3-enyl) -but-2-en-1-al was 43% gas chromatographic) certainly).

Example 2

Amounts used:
3.04 kg (20 mol) alpha-campholenaldehyde
2.9 kg (50 mol) propionaldehyde
170 + 85 g (3 mol) piperidine
120 + 60 g (3 mol) glacial acetic acid
2 kg of toluene.

Reaction:
3.04 kg of campholene aldehyde and 2 kg of toluene were placed in a 10 liter glass reactor and 2.9 kg of propionaldehyde, 170 g of piperidine and 120 g of glacial acetic acid were added with stirring at room temperature. The mixture was then refluxed for four hours on a water separator, 680 ml of water of reaction being removed. Gas chromatographic analysis of a sample of the reaction mixture showed a share of 15% of unreacted starting material. A further 85 g of piperidine and 60 g of glacial acetic acid were therefore added. After a further hour of reflux, a further 120 g of water had been removed and the starting material had been completely reacted.

Refurbishment:
After 1.9 kg of toluene had been distilled off, the mixture was washed twice with 2 l of water each time. The organic phase of 6.24 kg was distilled on a 30 cm packed column (boiling point 88-102 ° C./0.1 mbar), 3.27 kg of a yellowish product (purity determined by gas chromatography: 85%) were obtained ( 85% of theory).

2.2. reduction Example 3

Amounts used:
40.0 kg of crude aldol condensation product
40.0 kg ethanol (technical goods)
2.8 kg Cu-Zn catalyst.

The crude product of aldol condensation, ethanol and the Cu-Zn catalyst were placed in a 250 l steel autoclave with a gas stirrer and 5 times inerted with nitrogen. With vigorous stirring, hydrogen became initially pressed up to 10 bar. Then the internal temperature was raised 160 ° C increased and 6 hours at this temperature and a maximum of 40 bar  Hydrogen pressure hydrogenated. Water was used several times until the pressure was constant metered in, and the product contents were determined by gas chromatography certainly. After complete conversion was reached, the mixture was cooled and relaxed.

Refurbishment:
After a further analytical check, the product was filtered under nitrogen in the Seitz module filter. The catalyst (filter cake) was rinsed with ethanol and the washing liquor was combined with the filtrate. After flushing with ethanol, the catalyst was moistened with water for safety reasons and kept for recycling purposes. The crude product was freed from ethanol by distillation at normal pressure in a suitable kettle, after which it was only possible to remove further ethanol at 50 mbar without foaming. The product was then drawn off overhead in a lamp vacuum. Several fractions were collected separately, which were then examined olfactively. 32.5 kg of odorless product (approx. 81% of theory) were obtained.

Example 4 (for comparison)

Amounts used:
5 kg (11 mol) crude aldol condensation product
378 g (10 mol) sodium boranate
3 l isopropanol.

Reaction:
3 l of isopropanol were filled in a 10 l reactor and the sodium boranate was metered in with stirring. 5 kg of crude aldol condensation product were then metered continuously into the vigorously stirred mixture. Because of the rise in temperature (exothermic reaction), dosing was slow at the beginning and faster towards the end of the addition. The internal temperature was kept below 60 ° C. by external cooling. After adding the sodium boranate, the mixture was stirred for 3 hours while refluxing (heating temperature 150 ° C.).

Refurbishment:
The isopropanol was distilled off at 20 mbar and 2 l of saturated, ice-cold sodium sulfate solution were added to the residue cooled to room temperature. After mixing and settling, the water phase was drained and the washing out repeated. It was washed once with 3 l of 10% sodium hydroxide solution and twice with water. The pH of the wash water was 7-9. The final product (4780 g) was pre-cleaned after distilling off 800 g of low-boiling substances by short path distillation (KDL 1 from Leybold-Heraeus) in a high vacuum at an oil temperature of approx. 165 ° C./1 mbar. The distillate fractions of 760 g and 2200 g were fractionated on a rotating band column (Normag) (boiling point: 90-93 ° C / 0.05 mbar). 1125 g of an odor-acceptable product (34% of theory) were obtained.

Claims (9)

1. A process for the preparation of alkyl-substituted butenols of the general formula (I) R¹-CH₂-CH = CR²-CH₂OH (I) wherein R¹ is a saturated or olefinically unsaturated alkyl or cycloalkyl group with 4 to 16 carbon atoms, which may optionally be substituted by an alkyl, cycloalkyl, aryl or alkaryl radical - with the proviso that this substituent has a maximum of 12 C atoms - and R² is hydrogen or an alkyl group having 1 to 6 C atoms, by reaction of aldehydes of the formula (II) R¹-CH₂-CHO (II) in which R¹ has the same meaning as in formula (I), with the corresponding low aldehydes and subsequent reduction of the unsaturated aldehydes it contains, characterized in that

• i) the aldol condensation is carried out in an inert organic solvent and
• ii) the reduction of the unsaturated aldehydes is carried out in the presence of an optionally calcined copper-zinc contact.

2. The method according to claim 1, wherein the aldol condensation in one non-polar organic solvent that performs with water Forms azeotropically.   3. The method according to claim 1 or 2, wherein the aldol condensation in Presence of an ammonium salt of an organic acid as a catalyst carries out. 4. The method according to any one of claims 1 to 3, wherein R² in the formula (I) means a methyl group. 5. The method according to claim 4, wherein in step i) propionaldehyde in 2.5 to 10 molar excess - based on the aldehyde (II) - a puts. 6. The method according to any one of claims 1 to 5, wherein R¹ is a 4- (2,2,3- Trimethylcyclopent-3-enyl) residue means. 7. The method according to any one of claims 1 to 6, wherein in step i) an organic solvent selected from the Group toluene, xylene, benzene, cyclohexane and methylcyclohexane. 8. Use of the method according to one of claims 1 to 7 prepared alkyl-substituted butenols of formula (I), wherein R¹ a saturated or olefinically unsaturated alkyl or cycloalkyl group with 4 to 16 carbon atoms, which may be replaced by an Al alkyl, cycloalkyl, aryl or alkaryl radical can be substituted - with provided that this substituent has a maximum of 12 carbon atoms - and R² denotes hydrogen or an alkyl group with 1 to 6 C atoms, as fragrances. 9. Use according to claim 8 in cosmetic preparations, technical Products or alcoholic perfumery.