JP3336657B2 - Coumarin production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing coumarins,
Particularly, the present invention relates to a method for producing high-purity coumarins from 3- (2-oxocyclohexyl) propionic esters.
Coumarins are important compounds in the perfumery industry and are also used as intermediates for dyes, agricultural chemicals or pharmaceuticals.

[0002]

2. Description of the Related Art Coumarins are obtained by subjecting 3- (2-oxocyclohexyl) propionic acid esters to a cyclodehydrogenation reaction in the presence of a solid metal catalyst or the like. The 3,4-dihydrocoumarins by-produced in this reaction can be separated into products by distillation or the like, or can be converted to coumarins and effectively used by further dehydrogenation.

Other main by-products formed in this reaction are ethylbenzenes, o-ethylphenols, and 3
Compounds having a lower boiling point than coumarins such as -phenylpropionic acid esters, octahydrocoumarins, and 3-phenylpropionic acids; -o-ethylphenyl 3-cyclohexylpropionate; -o-ethylphenyl 3-phenylpropionate And compounds having a higher boiling point than coumarins such as coumarins and tar-like substances.

Conventional methods for removing these by-products include, for example, alkali treatment, distillation, recrystallization and the like as described in Japanese Patent Application Laid-Open No. 50-10667.

[0005]

However, according to the conventional method, a large amount of o-ethylphenols and 3,4-dihydrocoumarins are mixed in the fraction of coumarins during rectification, and even if crystallization is carried out once, It could not be sufficiently removed and the purity of coumarins in the product was reduced. Since o-ethylphenols have a low boiling point and have a phenol-like odor, they deteriorate the scent of coumarins, which are fragrances. Therefore, it is desired that the content of o-ethylphenols in coumarins be about 0.002% by weight or less, preferably 0.001% by weight or less.

Since 3,4-dihydrocoumarins have a peculiar odor, the content of 3,4-dihydrocoumarins in coumarin is reduced to about 0.05% by weight or less, preferably 0.02% by weight or less. It is desired to do.

Therefore, in order to obtain coumarins with high purity, complicated steps such as repetition of rectification and crystallization are required, leading to loss of coumarins.

The present inventors have conducted intensive studies on a method for producing high-quality coumarins as a fragrance with high purity. As a result, o-ethylphenols are contaminated by 3-cyclohexylpropionic acid-o in rectification. Esters of o-ethylphenols, such as -ethylphenyls and 3-phenylpropionic acid-o-ethylphenyls, form o-ethylphenols and 3-cyclohexylpropionic acid or 3-phenylpropionate during the distillation of coumarins. It is considered that this is due to thermal decomposition to carboxylic acids such as on acids, and the o-ethylphenols are distilled together with coumarins.

[0009] Further, the reason that 3,4-dihydrocoumarins are contaminated is that 3- (2-hydroxyphenyl) propionic acid is produced in the rectification and 3,4,4-dihydrocoumarin is produced during the distillation of coumarins.
-Dihydrocoumarins, and it is considered that the 3,4-dihydrocoumarins are distilled together with the coumarins. The cyclized dehydrogenation reaction solution was distilled in advance to obtain a high boiling point compound and 3- (2 -Hydroxyphenyl) propionic acids were removed, rectification and crystallization were performed, and it was found that high-quality coumarins could be produced as high-purity fragrances, and the present invention was completed.

[0010]

Means for Solving the Problems That is, the present invention provides a compound represented by the following general formula (1):

Embedded image (In the formula, R ^{1 to} R ⁴ each represent a hydrogen atom, a methyl group or an ethyl group, and R ⁴ represents an alkyl group having 1 to ⁴ carbon atoms.)
Cyclodehydrogenation of 3- (2-oxocyclohexyl) propionic acid esters represented by the general formula (2) in the presence of a solid metal catalyst,

Embedded image (Wherein, R ^{1 to} R ⁴ are the same as the groups described above). In the method for producing coumarins, the reaction mixture is distilled in advance to remove high-boiling substances, and contains the general formula (3) ),

Embedded image (Wherein, R ^{1 to} R ⁴ are the same as the above-mentioned groups), and -o-ethylphenyl 3-cyclohexylpropionate represented by the general formula (4):

Embedded image Wherein, in the formula, R ^{1 to} R ⁴ are the same as those described above, the total amount of the 3-phenylpropionate-o-ethylphenyls represented by the general formula (5) ),

Embedded image (Wherein, R ^{1 to} R ⁴ are the same as the above-mentioned groups.) The amount of 3- (2-hydroxyphenyl) propionic acids represented by the formula is reduced to 1% by weight or less of the coumarins, and then rectified. Containing general formula (6),

Embedded image (Wherein, R ^{1 to} R ⁴ are the same as the groups described above).

Embedded image (Wherein, R ^{1 to} R ⁴ are the same as the above groups.) 3,4-Dihydrocoumarin represented by the formula ( ¹ ) is obtained in an amount of 0.2% by weight or less, and the coumarin is further crystallized. A method for producing coumarins, characterized in that:

The 3- (2-oxocyclohexyl) propionate used in the present invention is represented by the general formula (1), for example, methyl 3- (2-oxocyclohexyl) propionate, 3- (2-oxocyclohexyl) propionate, Ethyl (2-oxocyclohexyl) propionate, propyl 3- (2-oxocyclohexyl) propionate, 3- (2
-Oxocyclohexyl) butyl propionate, 3-
(2-oxocyclohexyl) iso-propyl propionate and methyl- and / or ethyl-substituted products thereof.

Coumarins obtained by cyclodehydrogenation of these 3- (2-oxocyclohexyl) propionic esters are those represented by the general formula (2), for example, coumarin, 5-methylcoumarin 6-methylcoumarin, 7-methylcoumarin, 8-methylcoumarin,
5-ethylcoumarin, 6-ethylcoumarin, 8-ethylcoumarin, 5,6-dimethylcoumarin, 5,8-dimethylcoumarin, 5-methyl-6-ethylcoumarin, 8-ethyl-6-methylcoumarin and the like. .

The solid metal catalysts are group IIA and IIIA of the periodic table.
Group, IVA or VIA simple substance or compound, for example, a solid metal catalyst in which a metal such as palladium, platinum, rhodium, ruthenium is supported on a carrier such as carbon, alumina, silica gel, barium sulfate, etc. A metal catalyst, particularly a solid metal catalyst in which palladium is supported on activated carbon, is preferably used. A catalyst having a loading of a metal such as palladium on a carrier of about 0.5 to 10% by weight is preferably used. In addition, a chromium compound or the like may be supported together with a metal such as palladium in an amount of about 1 to 20% by weight based on the metal such as palladium.

[0014] The amount of the catalyst depends on the loading, but if the amount is small, the reaction activity is remarkably low. Conversely, if the amount is too large, the reaction activity is too high to generate many by-products and the cost of the catalyst is increased. The metal is used in an amount of about 0.001 to 1% by weight, preferably about 0.01 to 0.1% by weight, based on the weight of 3,-(2-oxocyclohexyl) propionic acid esters.

Further, in the cyclodehydrogenation reaction, metallic chromium, metallic tungsten, barium sulfate, magnesium trisilicate, zirconia, etc. may be added as a co-catalyst together with a solid metal catalyst such as palladium. The promoter is 3- (2
About 0.01 to 3% by weight, based on -oxocyclohexyl) propionic esters, is used.

The cyclodehydrogenation reaction is carried out at about 100-350 ° C., preferably at 230-300 ° C. Temperature is about 100
If the temperature is lower than 0 ° C., the reaction activity is low, and if it is higher than about 350 ° C., decomposition of the raw materials occurs, which is not preferable.

The cyclodehydrogenation reaction can be carried out using a solvent. As the solvent, phenyl ether, benzyl ether, methyl-α-naphthyl ether, ethylnaphthalene, dimethylbiphenyl, dodecane, tetradecane,
Examples include tetralin, acetophenone, phenylpropyl ketone, methyl benzoate, dimethyl glutamate and the like. However, it is not necessary to use a solvent.

The cyclodehydrogenation reaction is carried out by charging a 3- (2-oxocyclohexyl) propionic acid ester, a solid metal catalyst and, if necessary, a cocatalyst and a solvent, and heating at a predetermined temperature for several hours to several tens of hours. Will be

As a result of the reaction, the coumarins usually contain about 5 to 3
5 mol%, 3,4-dihydrocoumarins are about 30-70
Obtained in mole% yield. In addition, o-ethylphenyl 3-cyclohexylpropionate and o-ethylphenyl 3-phenylpropionate together produce 2 to 20% by weight based on coumarins. 3-Phenylpropionic acid is formed in an amount of 1 to 20% by weight based on the coumarin. In addition, ethylbenzenes, o-ethylphenols, 3-phenylpropionates, octahydrocoumarins and tar-like substances are by-produced.

The 3,4-dihydrocoumarins can be separated into a product by distillation for removing high boiling compounds described below and rectification for obtaining coumarins.
Further, the separated 3,4-dihydrocoumarins can be converted into coumarins by performing a dehydrogenation reaction. The dehydrogenation reaction can be performed under the same conditions as in the cyclization dehydrogenation reaction. The mixture containing coumarins obtained by the dehydrogenation reaction is mixed with the mixture containing coumarins obtained by the cyclodehydrogenation reaction in the same manner as the mixture containing coumarins obtained by the cyclodehydrogenation reaction. Can be processed.

In the distillation for removing the high boiling compounds in the reaction mixture in advance, simple distillation is sufficient.
The reaction may be carried out at a reflux ratio of 10 or less by using a packed tower or a column having a number of stages or less. The number of actual plates is 10 to 10 for the purpose of separating coumarins and 3,4-dihydrocoumarins, for example.
Distillation may be performed at a reflux ratio of 10 to 50 using a zero-stage distillation column.

The distillation is usually performed at a pressure of about 0.1 to 100 torr. If the pressure is lower than about 0.1 torr, the pressure reducing device becomes large, and the distillation speed becomes low, so that the productivity decreases. If the pressure is higher than about 100 torr, it is necessary to raise the temperature of the distillation still, and it is not preferable because coumarins and 3,4-dihydrocoumarins are easily decomposed.

The distillation is carried out to remove high-boiling compounds. In the reaction mixture, the combined amount of o-ethylphenyl 3-cyclohexylpropionate and o-ethylphenyl 3-phenylpropionate is about 3% by weight or less of coumarins. Preferably it is less than about 1% by weight.

The compound which forms o-ethylphenols in the rectification is 3-cyclohexylpropionic acid-o
-Ethylphenyls and 3-phenylpropionic acid-o-
Not only ethylphenyls, but if the total amount of o-ethylphenyl 3-cyclohexylpropionate and o-ethylphenyl 3-phenylpropionate is about 3% by weight or less of coumarins, it is formed in rectification. O-
The amount of ethylphenols is sufficiently small, and coumarins having high purity and sufficient quality as a fragrance can be obtained by one crystallization.

The 3- (2-hydroxyphenyl) propionic acids almost disappear in the distillation. Although the destination of 3- (2-hydroxyphenyl) propionic acids is not clear, it is considered that 3- (2-hydroxyphenyl) propionic acids are converted to 3,4-dihydrocoumarins and distilled during distillation.

In order to remove acidic by-products such as 3-phenylpropionic acids, it may be washed with an alkali such as aqueous sodium bicarbonate before distillation for removing high boiling compounds. However, when washing with alkali after distillation to remove high-boiling compounds, some of the 3,4-dihydrocoumarins become 3
-(2-hydroxyphenyl) propionic acids,
The effect of distillation to remove high boiling compounds is reduced.

The rectification is usually carried out using a packed tower, a column tower or the like. A distillation column having about 5 to 100 actual plates is used. When the actual number of stages is less than about 5 stages, the separation is poor.
Coumarins of sufficiently high purity cannot be obtained in the round. If the actual number of stages is about 100 or more, the equipment of the distillation column is undesirably large. The reflux ratio depends on the actual number of stages, but is about 1 to 5
0, preferably about 5-20. When the reflux ratio is about 1 or less, separation is poor, and coumarins of sufficiently high purity cannot be obtained even when crystallized. When the reflux ratio is about 50 or more, the energy for reflux is large, which is not preferable.

The pressure is set at about 0.1 to 100 torr. When the pressure is lower than about 0.1 torr, the pressure reducing device becomes large, the distillation speed becomes low, and the efficiency becomes poor.
When the pressure is higher than about 100 torr, it is necessary to raise the temperature of the rectifying vessel, and the temperature of the rectifying vessel increases, so that coumarins, 3,4-dihydrocoumarins, and 3-cyclohexylpropionic acid-o are used. -Ethylphenyls, 3
-Decomposition of -o-ethylphenyl phenylpropionate and the like is likely to occur.

The crystallization is carried out by a conventionally known method. As a solvent used for crystallization, organic solvents such as hydrocarbons, halogenated hydrocarbons, alcohols, ketones, and esters, and mixtures thereof can be used. Also, a mixture of these organic solvents and water can be used. In particular, alcohols and mixtures of alcohols and water are preferred, and methanol, ethanol, and mixtures thereof with water are particularly preferred.

The crystallization is carried out by dissolving the coumarins and then cooling. Alternatively, it can be obtained by adding a poor solvent such as water after dissolving the coumarins. After the crystallization, coumarins are obtained by filtration. Coumarins obtained by crystallization are further washed with a solvent if necessary,
dry.

[0031]

According to the method of the present invention, high-quality coumarins can be easily produced as high-purity fragrances.

[0032]

EXAMPLES The present invention will now be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 A four-necked flask having an inner volume of 1 liter was charged with 308 g of methyl 3- (2-oxocyclohexyl) propionate and 3.0 g of a catalyst having activated carbon loaded with 5% by weight of palladium. This mixture was heated at 240 ° C. for 10 hours while stirring at 300 rpm under a nitrogen atmosphere to perform a cyclodehydrogenation reaction. After that, while continuing stirring at 300 rpm, 255
Heated at 270 ° C for 1 hour and 270 ° C for 16 hours. After the completion of the cyclization dehydrogenation reaction, the catalyst and the like were filtered from the reaction mixture to give
Was obtained.

The same cyclodehydrogenation reaction is further performed twice,
It was mixed with the first cyclization dehydrogenation reaction solution to obtain 624 g of the cyclization dehydrogenation reaction solution. The concentration of coumarin in the reaction mixture was 3
3.7% by weight, the concentration of 3,4-dihydrocoumarin is 4
8.1% by weight, 3-cyclohexylpropionic acid-o-
The total concentration of ethylphenyl and 3-phenylpropionic acid-o-ethylphenyl was 5.3% by weight, and the concentration of 3-phenylpropionic acid was 0.6% by weight. Therefore, the total amount of o-ethylphenyl 3-cyclohexylpropionate and o-ethylphenyl 3-phenylpropionate is 15.7% by weight with respect to coumarin, and 3-phenylpropionic acid is 1.8 with respect to coumarin. % By weight.

585 of the obtained cyclodehydrogenation reaction solution
g was washed with 586 g of a 5% by weight aqueous sodium bicarbonate solution and then with 583 g of water to obtain 572 g of a washed oil phase. 3-Phenylpropionic acid in the obtained washed oil phase was below the detection limit of gas chromatography. The obtained washing oil phase was 10
Simple distillation at torr to remove high boiling compounds,
g fraction was obtained. The concentration of coumarin in the obtained fraction was 3
2.7% by weight, the concentration of 3,4-dihydrocoumarin is 5
4.8% by weight, 3-cyclohexylpropionic acid-o-
The total amount of the concentrations of ethylphenyl and 3-o-ethylphenyl 3-phenylpropionate was 0.16% by weight, and 3- (2
-Hydroxyphenyl) propionic acid was below the detection limit of gas chromatography. Therefore, 3-o-ethylphenyl 3-cyclohexylpropionate and 3-
The total amount of o-ethylphenyl phenylpropionate was 0.49% by weight with respect to coumarin, and 3- (2-hydroxyphenyl) propionic acid was 1% with respect to coumarin.
% By weight or less.

The obtained fraction was rectified in a packed column having 33 actual plates at 20 torr and a reflux ratio of 10. as a result,
First, 172 g of pure 3,4-dihydrocoumarin was obtained. By continuing rectification, crude coumarin
9 g were obtained. Coumarin purity in crude coumarin is 9
The content of o-ethylphenol was below the detection limit of gas chromatography, the content of 3,4-dihydrocoumarin was 0.02% by weight, and the content of octahydrocoumarin was 1.43% by weight. there were. The yield based on coumarin in the cyclodehydrogenation reaction solution was 39.8% by weight.

To 71.9 g of the obtained crude coumarin, 143.3 g of methanol was added and dissolved at 40 ° C., followed by cooling to 3 ° C. for crystallization. After filtration, the crystals were washed with 73.4 g of methanol at 0 ° C and filtered. The obtained crystals were dried under reduced pressure to obtain 48.7 g of purified coumarin. The purity of the obtained purified coumarin is 99.99% or more, and o
The contents of -ethylphenol, 3,4-dihydrocoumarin and octahydrocoumarin were below the detection limit of gas chromatography. The purified coumarin obtained is of sufficient quality as a fragrance.

Example 2 A four-necked flask having an inner volume of 1 liter was charged with 300 g of methyl 3- (2-oxocyclohexyl) propionate and 2.1 g of a catalyst having activated carbon carrying 5% by weight of palladium. This mixture was heated at 250 ° C. for 10 hours while stirring at 240 rpm under a nitrogen atmosphere to perform a cyclodehydrogenation reaction. Then, while continuing stirring at 500 rpm, 2
Heated at 70 ° C. for 16 hours. After completion of the cyclodehydrogenation reaction, the catalyst and the like were filtered from the reaction mixture to obtain 195 g of a cyclodehydrogenation reaction solution.

The same cyclodehydrogenation reaction was further performed 11 times,
After mixing with the first cyclodehydrogenation reaction liquid, 2289 g of the cyclization dehydrogenation reaction liquid was washed with the same weight of 5% by weight aqueous sodium bicarbonate and the same weight of water to obtain 2194 g of a washed oil phase. . The concentration of coumarin in the washing oil phase is 37.9% by weight, the concentration of 3,4-dihydrocoumarin is 41.4% by weight, and o-ethylphenyl 3-cyclohexylpropionate and o-ethyl 3-phenylpropionate. The total amount of phenyl concentration was 7.3% by weight, and the concentration of 3- (2-hydroxyphenyl) propionic acid was 0.05% by weight. Therefore,
The total amount of o-ethylphenyl 3-cyclohexylpropionate and o-ethylphenyl 3-phenylpropionate is 19.3% by weight based on coumarin, and 3- (2-hydroxyphenyl) propionic acid is based on coumarin. 0.13% by weight.

The obtained washed oil phase was distilled at 10 torr and a reflux ratio of 10 using a packed column having 4 actual plates, and firstly 3,4 containing 86.1% by weight of 3,4-dihydrocoumarin was added.
817 g of a dihydrocoumarin fraction were obtained. By continuing distillation, high boiling compounds were removed, and 1029 g
Was obtained. The concentration of coumarin in the obtained fraction was 6
6.3% by weight, the concentration of 3,4-dihydrocoumarin is 2
0.1% by weight, 3-cyclohexylpropionic acid-o-
The total amount of the concentrations of ethylphenyl and 3-o-ethylphenyl 3-phenylpropionate was 0.78% by weight, and 3- (2
-Hydroxyphenyl) propionic acid was below the detection limit of gas chromatography. Therefore, 3-o-ethylphenyl 3-cyclohexylpropionate and 3-
The total amount of o-ethylphenyl phenylpropionate is 1.18% by weight based on coumarin, and 3- (2-hydroxyphenyl) propionic acid is 1% by weight based on coumarin.
% By weight or less.

The obtained fraction was rectified using a packed column having 33 actual plates at 30 torr and a reflux ratio of 10. as a result,
539 g of crude coumarin were obtained. The purity of coumarin in crude coumarin is 96.7% by weight, the content of o-ethylphenol is 0.014% by weight, the content of 3,4-dihydrocoumarin is 0.14% by weight, and the content of octahydrocoumarin is 3.03% by weight. The yield based on coumarin in the washing oil phase was 62.7% by weight.

80.4 g of methanol was added to 99.8 g of the obtained crude coumarin and dissolved at 40 ° C., followed by cooling to 15 ° C. for crystallization. After filtration, the crystals
Was washed with 40.6 g of methanol and filtered. The obtained crystals were dried under reduced pressure to obtain 74.8 g of purified coumarin. The purity of the obtained purified coumarin is 99.99%, the content of o-ethylphenol is below the detection limit of gas chromatography, and the content of 3,4-dihydrocoumarin is 0.00.
The content of octahydrocoumarin was 2% by weight and 0.011% by weight. The purified coumarin obtained is of sufficient quality as a fragrance.

Reference Example 1 Coumarin 94.1% by weight, 3,4-dihydrocoumarin 0.94% by weight, octahydrocoumarin 5.00% by weight
A crude coumarin containing was prepared. Crude coumarin 177.0
After adding 354 g of methanol and dissolving at 40 ° C.
Crystallization was achieved by cooling to 4 ° C. After filtration, the crystals were washed with 190 g of methanol at 4 ° C and filtered. The obtained crystals were dried under reduced pressure to obtain 113 g of purified coumarin. The purity of the obtained purified coumarin is 99.92%, and o-
The ethylphenol content is below the detection limit of gas chromatography, and the 3,4-dihydrocoumarin content is 0.0
8% by weight and octahydrocoumarin content was 0.02% by weight. The coumarin in the obtained purified coumarin was 67.8% by weight based on the coumarin charged. The obtained purified coumarin has a peculiar odor like 3,4-dihydrocoumarin and is not of sufficient quality as a fragrance.

Reference Example 2 A crude coumarin containing 96.1% by weight of coumarin, 0.12% by weight of 3,4-dihydrocoumarin, 3.04% by weight of octahydrocoumarin, and 0.30% by weight of o-ethylphenol was prepared. . 80.4 g of methanol was added to 99.8 g of crude coumarin and dissolved at 40 ° C., followed by cooling to 15 ° C. for crystallization. After filtration, the crystals were washed with 40.6 g of methanol at 15 ° C and filtered. The obtained crystals were dried under reduced pressure to obtain 65.0 g of purified coumarin. The purity of the obtained purified coumarin is 99.98%, the content of o-ethylphenol is 0.007% by weight, the content of 3,4-dihydrocoumarin is 0.009% by weight, and the content of octahydrocoumarin is 0%. 0.0006% by weight. The coumarin in the obtained purified coumarin was 69.4% by weight based on the coumarin charged. The resulting purified coumarin is o-
It has a phenolic smell presumably derived from ethylphenol, and is not of sufficient quality as a fragrance.

COMPARATIVE EXAMPLE 1 A four-necked flask having an inner volume of 1 liter was charged with 411 g of methyl 3- (2-oxocyclohexyl) propionate and 8.0 g of a catalyst having activated carbon loaded with 5% by weight of palladium. This mixture was heated at 240 ° C. for 8.5 hours while stirring at 300 rpm under a nitrogen atmosphere to perform a cyclodehydrogenation reaction. Thereafter, the stirring was continued at 300 rpm for 250 minutes.
Heated for 5.5 hours at 260C and 16 hours at 260C. After the completion of the cyclization dehydrogenation reaction, the reaction mixture was filtered to remove the catalyst and the like.
2 g of the cyclodehydrogenation reaction liquid was obtained.

In the same manner, a total of 557
g was obtained. The concentration of coumarin in the reaction mixture was 39.9% by weight, the concentration of 3,4-dihydrocoumarin was 42.3% by weight, o-ethylphenyl 3-cyclohexylpropionate and o-ethyl 3-phenylpropionate. The total amount of phenyl concentration was 6.6% by weight, and the concentration of 3- (2-hydroxyphenyl) propionic acid was 0.67% by weight. Therefore, 3-cyclohexylpropionic acid-
o-ethylphenyl and 3-phenylpropionic acid-o-
The total amount of ethylphenyl was 16.5% by weight based on coumarin, and 3- (2-hydroxyphenyl) propionic acid was 1.68% by weight based on coumarin.

342 of the obtained cyclodehydrogenation reaction solution
g was rectified using a packed column having 33 actual plates at 20 torr and a reflux ratio of 10. As a result, crude coumarin was 31.9.
g were obtained. The coumarin purity in the crude coumarin was 93.
6% by weight, and the o-ethylphenol content was 0.2%.
1% by weight, 3,4-dihydrocoumarin content is 1.00
Wt%, octahydrocoumarin content is 5.10 wt%
Met. The yield based on coumarin in the cyclodehydrogenation reaction solution was 21.9% by weight. The resulting crude coumarin is o-
Since the contents of ethylphenol and 3,4-dihydrocoumarin are large, the coumarin obtained by one crystallization as shown in Reference Examples 1 and 2 has insufficient quality and cannot be used as a fragrance.

Example 3 A coumarin concentration of 41.3% by weight, a 3,4-dihydrocoumarin concentration of 40.7% by weight, and a cyclized dehydrogenation reaction of 41.3% by weight were obtained in the same manner as in Example 1. The total amount of the concentrations of -o-ethylphenyl cyclohexylpropionate and -o-ethylphenyl 3-phenylpropionate is 6.4% by weight;
549 g of the cyclodehydrogenation reaction solution having a concentration of 3-phenylpropionic acid of 0.4% by weight was rectified at a pressure of 10 torr and a reflux ratio of 5 using a packed column having 33 actual plates. 3,4-
238 g of a fraction containing 80.7% by weight of dihydrocoumarin was removed, the concentration of coumarin was 71.4% by weight, the concentration of 3,4-dihydrocoumarin was 8.9% by weight, and o-ethyl 3-cyclohexylpropionate. When the total concentration of phenyl and o-ethylphenyl 3-phenylpropionate is 1
303 g of a 2.4% by weight kettle residue were obtained.

A coumarin concentration of 69.6% by weight, a 3,4-dihydrocoumarin concentration of 12.0% by weight, and o-ethylphenyl 3-cyclohexylpropionate mixed with a bottom obtained in the same manner. The remaining 1536 g of the residue having a total concentration of 11.0% by weight and the concentration of 3-phenylpropionate-o-ethylphenyl were subjected to simple distillation at 10 torr to remove high boiling compounds, thereby obtaining 1235 g of a fraction. The concentration of coumarin in the obtained fraction was 74.9% by weight, the concentration of 3,4-dihydrocoumarin was 15.4% by weight, and 3-cyclohexylpropionic acid-o-ethylphenyl and 3-phenylpropionic acid-o were used. The total amount of the concentration of -ethylphenyl was 2.11% by weight, and that of 3-phenylpropionic acid was 1.2% by weight. Therefore, the total amount of o-ethylphenyl 3-cyclohexylpropionate and o-ethylphenyl 3-phenylpropionate was 2.8% by weight based on coumarin.

1235 g of the obtained fraction was rectified at a pressure of 30 torr and a reflux ratio of 10 using a packed column having 33 actual plates. As a result, 671 g of crude coumarin was obtained. The coumarin purity in the crude coumarin is 98.5% by weight,
The o-ethylphenol content was 0.08% by weight, 3,4
-The content of dihydrocoumarin was 0.009% by weight, the content of octahydrocoumarin was 1.3% by weight, and the content of 3-phenylpropionic acid was 0.04%. Therefore, by crystallizing this crude coumarin once, purified coumarin of sufficient quality as a fragrance can be obtained.

Comparative Example 2 A coumarin concentration of 33.5% by weight, a 3,4-dihydrocoumarin concentration of 44.2% by weight, and a cycline dehydrogenation reaction of 34.2% by weight were obtained in the same manner as in Example 1. The total amount of the concentrations of o-ethylphenyl cyclohexylpropionate and o-ethylphenyl 3-phenylpropionate is 6.7% by weight,
Using a packed tower having 6 actual stages, 610 g of a cyclodehydrogenation reaction solution having a concentration of 3-phenylpropionic acid of 0.2% by weight,
High-boiling compounds were removed by rectification at a pressure of 10 torr and a reflux ratio of 2 to obtain 471 g of a fraction. The concentration of coumarin in the obtained fraction was 32.1% by weight, the concentration of 3,4-dihydrocoumarin was 56.0% by weight, and 3-cyclohexylpropionic acid-o-ethylphenyl and 3-phenylpropionic acid-o were used. The total amount of the concentration of -ethylphenyl was 0.14% by weight.

454 g of the obtained fraction was
g of a 5% by weight aqueous sodium bicarbonate solution and 454 g of water.
0 g of the washed oil phase was obtained. The content of 3-phenylpropionic acid in the obtained washing oil phase was 0.01% by weight.

441 g of the obtained washing oil phase was rectified at a pressure of 20 torr and a reflux ratio of 8 using a packed column having 33 actual plates. As a result, first, 153 g of purified 3,4-dihydrocoumarin was obtained. This purified 3,4-dihydrocoumarin is of sufficient quality as a fragrance. Next, 79 g of crude coumarin was obtained. The coumarin purity in the crude coumarin was 96.1% by weight, the o-ethylphenol content was 0.01% by weight, the 3,4-dihydrocoumarin content was 2.2% by weight, and the octahydrocoumarin content was 1%. 0.7% by weight. Since the obtained crude coumarin has a large content of 3,4-dihydrocoumarin, coumarin obtained by one crystallization cannot be used as a fragrance.

────────────────────────────────────────────────── (5) References JP-A-4-356478 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07D 311/10 B01J 23/44 C07B 61 / 00 300 CA (STN) CAOLD (STN) REGISTRY (STN)

Claims (1)

(57) [Claims] 1. A compound represented by the general formula (1): (In the formula, R ^{1 to} R ⁴ each represent a hydrogen atom, a methyl group or an ethyl group, and R ⁵ represents an alkyl group having 1 to 4 carbon atoms.)
Cyclodehydrogenation of 3- (2-oxocyclohexyl) propionic acid esters represented by the general formula (2) in the presence of a solid metal catalyst, (Wherein, R ^{1 to} R ⁴ are the same as the groups described above). In the method for producing coumarins, the reaction mixture is distilled in advance to remove high-boiling substances, and contains the general formula (3) ), Embedded image (Wherein R ^{1 to} R ⁴ are the same as the above-mentioned groups), and o-ethylphenyl 3-cyclohexylpropionate represented by the general formula (4): (Wherein R ^{1 to} R ⁴ are the same as the above-mentioned groups). The total amount of 3-phenylpropionic acid-o-ethylphenyls represented by the formula ), Embedded image (Wherein, R ^{1 to} R ⁴ are the same as the above-mentioned groups.) The amount of 3- (2-hydroxyphenyl) propionic acids represented by the formula is reduced to 1% by weight or less of the coumarins, and then rectified. Containing general formula (6): (Wherein, R ^{1 to} R ⁴ are the same as those described above) in an amount of 0.1% by weight or less of an o-ethylphenol represented by the following general formula (7): (Wherein, R ^{1 to} R ⁴ are the same as the above groups.) 3,4-Dihydrocoumarin represented by the formula ( ¹ ) is obtained in an amount of 0.2% by weight or less, and the coumarin is further crystallized. A method for producing coumarins, comprising: