JPS6223733B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing acyloin by condensing aldehydes in the presence of a thiazolium salt and a base.

It is already known in the literature to prepare acyloins by condensation of aldehydes in the presence of low molecular weight thiazolium salts as catalysts and bases as promoters. Corresponding reactions are described, for example, in J. Am. Chem. Soc. 80 (1958), 3719-3726, J.
Chem.Soc.Chem.Commun.1973, 891 and
Synthesis Commun.1976, 734.

A disadvantage of the known process is that the thiazolium salt used as catalyst can only be removed from the reaction mixture by very expensive methods. Since it is not possible to remove all the crude reaction products from the thiazolium salt, the subsequent distillation produces unpleasant-smelling decomposition products, which some of the decomposition products migrate with the distillate and yield It seriously harms the quality of Asilin. Another drawback is that it is very difficult to recover the low molecular weight thiazolium salts in pure form from the wash water after working up the reaction mixture.

The object of the present invention is therefore to find a method for producing asiloin which also does not have the above-mentioned disadvantages. In particular, catalysts must be found that can be easily and completely removed from the reaction mixture.

This task is a general expression (wherein R represents an alkyl group containing 1 to 7 carbon atoms) is condensed in the presence of a catalyst and a base to form a compound of the general formula (In the formula, R has the above-mentioned meaning) In the method for producing acyloin represented by the above formula, 5-(2'-hydroxyethyl)-4-methyl-1,3-thiazole and reticulated chloromethyl- The problem is solved by the above production method, which is characterized in that a reaction product consisting of polystyrene is used.

As examples of aldehydes which can be used as starting compounds in the process of the invention, the following may be mentioned: acetaldehyde, acetoxyacetaldehyde, propionaldehyde, n-butyraldehyde, isobutyraldehyde, bivalinaldehyde, valeraldehyde, isobutyraldehyde, Valeraldehyde, capronaldehyde, enantaldehyde, 2-ethyl-hexanal, caprylaldehyde.

It goes without saying that the hydrocarbon radicals of the aldehydes mentioned above may carry substituents, such as halogen atoms, ester groups or ether groups, as long as it is ensured that said substituents do not take part in the acyloin condensation in a detrimental way. You can also do it.

To produce the catalyst used in the present invention, 5-
(2'-hydroxyethyl)-4-methyl-1,3
- Reacting the thiazole with the reticulated chloromethyl polystyrene at elevated temperatures, in particular from 60 to 100°C.
Chloromethyl polystyrene is a known and somewhat commercially available material that can be prepared by chloromethylating polystyrene with formaldehyde and hydrogen chloride.

Thiazoles are generally applied to reticulated chloromethyl polystyrene in an inert solvent or in water. Neutral solvents such as dimethylformamide, acetonitrile, dioxane or tetrahydrofuran are particularly suitable. Excess thiazole can also be used as a solvent. It has been found that it is preferable in all cases to use a stoichiometric excess of thiazole in order to react virtually completely the chloromethyl groups of the polystyrene resin. After the reaction, the polymerization catalyst containing thiazolium groups is removed, extracted with an inert solvent such as ether or alcohol and finally dried.

Cocatalysts include inorganic and organic bases, such as sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, potassium carbonate, sodium acetate, potassium acetate, disodium hydrogen phosphate, triethylamine, triethanolamine,
N-methylpyrrolidine or basic ion exchangers come into consideration.

The amount of catalyst used is not critical. In general, the process according to the invention is carried out using an amount of catalyst resin containing from 1 to 50 mol %, in particular from 3 to 20 mol %, of quaternary thiazolium groups, calculated from the aldehyde to be reacted. However, amounts corresponding to less than 1 mol % are sufficient for carrying out the method.

The amount of base used is also not critical. Generally, equimolar amounts are used as the thiazolium salt groups contained in the catalyst. However, it is preferable to use 2 to 5 times the molar amount. When working with an aqueous or hydroalcoholic solution, the amount of base must be adjusted to maintain a pH value of about 7.3 to about 8.5.

When carrying out the process of the invention, the aldehyde to be reacted is optionally dissolved in a solvent and together with the catalyst suspended therein at room temperature or at elevated temperature.
Stir until desired degree of conversion is obtained. Considering the sensitivity of the catalyst, the reaction temperature should not be practically higher than 80°C.

When the method of the invention is carried out in the presence of a solvent,
polar solvents such as water, methanol, ethanol, isopropanol, dioxane, tetrahydrofuran, acetonitrile, dimethylformamide, dimethylsulfoxide, hexamethylphosphoric triamide and pyridine and mixtures of these solvents;
In particular water/ethanol mixtures come into consideration.

After the reaction has ended, the catalyst is separated from the reaction mixture by filtration. The liquid component of the reaction mixture, after distilling off any solvent present, is worked up by methods customary in organic chemistry, such as fractional distillation and recrystallization.

The separated catalyst can be reused after washing with an organic solvent and drying.

In a particular embodiment of the process of the invention, the catalytic resin containing thiazolium groups is used in basic form. This production method allows production without additional base as co-catalyst. The basic or OH ^- form of the catalyst is very easily obtained by treating the resin in its salt form (containing thiazolium groups) with a base, e.g. an aqueous solution of sodium bicarbonate, until the resin is free of chloride ions. I can do it.

The products obtained in the process of the invention are valuable perfumes and fragrances; they are also valuable intermediates for organic synthesis.

The process according to the invention has the advantage over known production processes that the catalyst used can be removed quantitatively from the reaction mixture in a very simple manner, ie by filtration. Any deterioration of the quality of the produced asiloin due to decomposition products occurring when distilling off the catalyst is thereby avoided.

The present invention will be described below with reference to examples, but the present invention is not limited thereto.

Example 1 40 g of reticulated chloromethyl polystyrene with a chlorine content of 5.78% by weight was suspended in 100 ml of dimethylformamide and 5-(2'-hydroxyethyl)-4
-72 with 21.6g of methyl-1,3-thiazole
Stirred at 80°C for an hour. The resin was then removed, extracted with ether, and dried in vacuo at 40° C./0.01 Torr. The chlorine content of the resin containing 5-(2'-hydroxyethyl)-4-methyl-1,3-thiazolium groups was 3.71% by weight.

Example 2 64.1 g (0.5 mol) of distilled capryaldehyde, 23.8 g of thiazolium salt catalyst from Example 1
(0.025 mol) and triethylamine 15.2 g (0.15
mol) was stirred at 90° C. for 7 hours under nitrogen flow. The mixture was then diluted with ether and the catalyst was removed.
The catalyst was extracted repeatedly with ether. Ether was distilled off from the combined ether solution at normal pressure in a nitrogen stream, and then unreacted capryaldehyde and excess triethylamine were distilled off under reduced pressure using a water jet pump. The residue thus obtained (63.3g) was
When examined by chromatography, it contained 94.9% by weight of capriloin. For further purification, capryloin was recrystallized from benzine (65-95°). 55g pure capriloin with a melting point of 38-39℃
(86% of theory) was obtained.

Example 3 110.0 g of freshly distilled acetaldehyde (2.5
mol), 23.8 g of thiazolium salt catalyst from Example 1
(0.025 mol) and triethylamine 15.2 g (0.15
mol) was stirred at 80° C. for 8 hours in an autoclave equipped with a magnetic stirrer to which nitrogen pressure of 5 atm gauge was added in advance. The maximum pressure obtained at 80°C was 7 atm gauge. After cooling and opening the autoclave, the reaction mixture was poured into ether to remove the catalyst in order to facilitate its separation. After the ether had been distilled off, the residue was fractionally distilled through a Pigreau column under carbon dioxide and a water pump vacuum. boiling point
68.1g of pure acetoin at 37-38℃/12 Torr
(61% of theory) was obtained.

Example 4 25.6 g of freshly distilled caprylic aldehyde
(0.2 mol) was dissolved with stirring and cooling in a mixture consisting of 50 ml of water and 50 ml of ethanol. Add the thiazolium salt catalyst from Example 1 to this solution at room temperature.
9.5 g (0.01 mol) were mixed. After adding 1 g of disodium hydrogen phosphate dissolved in 5 ml of water, the pH value of the solution was brought to 8.4 with 1N sodium hydroxide solution. The mixture was then heated to 60° C. with vigorous stirring under a stream of nitrogen and kept at this temperature for 71/4 hours. After cooling, the reaction mixture was worked up as in Example 2. The obtained crude reaction product was determined by gas chromatography to contain 73.2% by weight of capryloin and 73.2% by weight of aldol.
2.3% by weight and 23.5% by weight of caprylic aldehyde.

Example 5 5-(2'-hydroxyethyl)-4 from Example 1
30 g of a resin containing -methyl-1,3-thiazolium groups (in chloride form) were mixed into saturated sodium bicarbonate solution 1. This suspension was placed in an exchanger column. The resin was then washed with saturated sodium bicarbonate solution until the run-off was free of chloride ions. Subsequently, the catalyst, now present in the OH form, was washed with water and dried at 40°C.

Example 6 16.0 g (0.13 mol) of distilled capryaldehyde and 6 g (0.007 mol) of the thiazolium salt catalyst in the OH ^- form from Example 5 were heated to 60° C. with stirring in a stream of nitrogen and kept at this temperature for 4 hours. . After cooling, the reaction mixture was worked up as in Example 2. Gas chromatographic analysis showed that the crude reaction product contained 89.0% by weight capryloin and 11.0% by weight capryaldehyde.

Example 7 25.6 g (0.2 mol) of caprylic aldehyde in Example 4
Similarly, it was dissolved in 100 ml of water/ethanol mixture. 9.5 g (0.01 mol) of the C ^- form thiazolium salt catalyst according to Example 1 were mixed into this solution. After adding 1 g of disodium hydrogen phosphate dissolved in 5 ml of water, the pH value of the solution was adjusted to 7.4. The mixture was heated to 60°C under nitrogen and kept at this temperature for 71/4 hours. Work-up of the reaction mixture was carried out as described in Example 2. As determined by gas chromatography, the reaction product of the purification contained 75% by weight of capryloin, 19.2% by weight of capryaldehyde, 2.6% by weight of acetal and 3.2% by weight of aldol.

Example 8 36.1 g of freshly distilled n-butyraldehyde
(0.5 mol) and 9.2 g (0.01 mol) of the resin containing 5-(2'-hydroxyethyl)-4-methyl-1,3-thiazolium groups in the OH form from Example 1 without stirring under a nitrogen stream. The mixture was heated to 70°C for 5 hours. After cooling, the reaction mixture was worked up as in Example 2. The crude reaction product obtained contained 84.5% by weight of butyroin and 15.5% by weight of butyraldehyde, as determined by gas chromatography.

The crude product was fractionally distilled through a Pigraw column under carbon dioxide and water pump vacuum. boiling point
86℃/13 tons of butyroin 24.7g (theoretical amount 69
%) obtained. This product was analyzed by gas chromatography and was found to be composed of 100% butyroin.

Example 9 A glass ion exchange column equipped with a glass jacket and glass beads was charged with 20 g of the thiazolium salt catalyst in the OH form according to Example 8. The column was filled with capryaldehyde under nitrogen. The contents of the column were heated to 80°C by passing hot glycerin through the liquid jacket. Cabryl aldehyde was added fresh from a ceramic funnel under nitrogen to the top of the column and at the same rate as the reaction product flowed out through the glass stopcock to the bottom of the column. The average residence time was 2 hours for the reaction products.

The reaction product flowing to the bottom of the exchange column consisted of up to 90% by weight capryloin according to chromatographic analysis, the remainder being unreacted capryaldehyde.

Example 10 20 g (0.093 mol) of reticulated polychloromethylstyrene with a chlorine content of 16.5% by weight is suspended in 40 ml of dimethylformamide and 30.8 g of 5-(2'-hydroxyethyl)-4-methyl-1,3-thiazole
(0.215 mol) and stirred at 80°C for 24 hours. The resin was then taken, extracted with ether, and vacuumed for 40 min.
Dry at °C/0.01 Torr.

5-(2'-hydroxyethyl)-4-methyl-
The resin containing 1,3-thiazolium groups contained 8.61% by weight of electrolyte chlorine; the total chlorine content amounted to 9.33% by weight.

Example 11 20 g (0.093 mol) of reticulated polychloromethylstyrene with a chlorine content of 16.5% by weight is suspended in 50 ml of distilled water, and 30.8 g of 5-(2'-hydroxyethyl)-4-methyl-1,3-thiazole is suspended in 50 ml of distilled water. (0.215 mol)
The mixture was stirred at 80°C for 24 hours. The resin was then removed, washed with water, and extracted with ethanol to remove excess 5-
(2'-hydroxyethyl-4-methyl-1,3-
Thiazole was excluded. The purified resin is heated to 40% under reduced pressure.
Dry at °C/0.01 Torr.

The resin catalyst thus obtained contained 7.17% by weight of electrolyte chlorine; the total chlorine content amounted to 7.68% by weight.

Example 12 5-(2'-hydroxyethyl-4-
30g of resin containing methyl-1,3-thiazolium group
(0.06 mol) was mixed in saturated sodium bicarbonate solution 1. This suspension was transferred to an exchanger column. The resin was washed therein with saturated sodium bicarbonate solution until the effluent was free of chloride ions. Subsequently, the catalyst, now present in the OH form, was washed with water and dried at 40° C./0.01 Torr.

Example 13 110.0 g of freshly distilled acetaldehyde (2.5
mol) and 9.7 g (0.021 mol) of the thiazolium salt catalyst in the OH form according to Example 12 were heated at 80° C. for 1 hour in an autoclave equipped with a magnetic stirrer and pre-charged with a nitrogen pressure of 2 atm gauge. At that time, the pressure rose to 7 atmospheres gauge. After cooling, the reaction mixture was diluted with ether to remove the catalyst in order to facilitate separation of the catalyst. The ether was distilled off from the liquid. The residue was fractionally distilled on a Vigreux column under a water pump vacuum under carbon dioxide as protective gas. Acetoin with a boiling point of 39-43℃/13 Torr is 93.5
g (85% of theory). Gas chromatography analysis showed 100% pure product.

Claims (1)

[Claims] 1. General formula (wherein R represents an alkyl group containing 1 to 7 carbon atoms) is condensed in the presence of a catalyst and a base to form a compound of the general formula (In the formula, R has the above-mentioned meaning) In the method for producing acyloin represented by the above formula, 5-(2'-hydroxyethyl)-4-methyl-1,3-thiazole and reticulated chloromethyl- The above-mentioned manufacturing method is characterized in that a reaction product consisting of polystyrene is used. 2. Process according to claim 1, characterized in that an amount of the catalyst resin is used which contains from 1 to 50 mol %, preferably from 3 to 20 mol %, of quaternary thiazolium groups, based on the aldehyde to be reacted. 3. The method according to claim 1 or 2, wherein the catalyst resin containing thiazolium groups is used in the base form.