JP3079677B2 - Coumarin production method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved method for producing coumarins from 3,4-dihydrocoumarins. Coumarin and its derivatives are important compounds, especially in the perfumery industry, and can also be intermediates for pesticides, drugs or dyes.

[0002]

2. Description of the Related Art As a conventional method for obtaining coumarins,
3- (2-) in the presence of a hydrogenation-dehydrogenation catalyst such as palladium
Cyclohexanoyl) propionates are produced by heating to cyclodehydrogenate (US Pat. No. 3,44
No. 2,910), and a method of producing the compound by subjecting it to cyclodehydrogenation in the coexistence of barium sulfate, nickel oxide or the like as a co-catalyst together with a noble metal catalyst such as palladium (JP-A-60-181082)
No.) etc. are known.

A method for producing coumarins by using 3,4-dihydrocoumarins as a raw material and dehydrogenating in the presence of a noble metal catalyst such as palladium (Ber., 70B, 73).
5-8 (1936)), a method for producing coumarins by dehydrogenation using chlorine, bromine, oxygen or sulfur (Mon)
atsh. , 34.1671-72 (1913), German Patent No. 276667), and the like.

[0004]

When 3- (2-cyclohexanoyl) propionic acid esters are heated and cyclodehydrogenated in the presence of a palladium catalyst, the yield of coumarins is not always required. Is not high, and a large amount of 3,4-dihydrocoumarins is by-produced. Further, in producing coumarins by performing a dehydrogenation reaction using 3,4-dihydrocoumarins as a raw material, it is difficult to remove chlorine or sulfur or the like by a method of dehydrogenating using chlorine or sulfur or the like. Becomes complicated.

On the other hand, in the presence of a palladium catalyst, 3,4-
The method of performing the dehydrogenation of dihydrocoumarins is relatively easy to purify, but has low selectivity due to side reactions. Also,
An expensive noble metal catalyst such as palladium is used, and the catalyst cost is high.

The present inventors have conducted intensive studies on a method for producing coumarins from 3,4-dihydrocoumarins with good selectivity and low catalyst cost.
When a palladium catalyst used for heating a 3- (2-cyclohexanoyl) propionic acid ester to cyclodehydrogenate in the presence of a palladium catalyst is used for a dehydrogenation reaction of 3,4-dihydrocoumarins. The selectivity from 3,4-dihydrocoumarins to coumarins is improved as compared with the case where a new catalyst is used, and a new catalyst is not required.
The inventors have found that the catalyst cost is low and it is very economical, and have completed the present invention.

[0007]

That is, the present invention provides a compound represented by the following general formula (1): (Wherein, R _{1 to} R ₄ each represent a hydrogen atom, a methyl group or an ethyl group, and at least two groups among R _{1 to} R ₄ are hydrogen atoms). Is dehydrogenated in the presence of a palladium catalyst to obtain a compound represented by the general formula (2): (Wherein, R _{1 to} R ₄ are the same as the above-mentioned groups.) In producing a coumarin represented by the general formula (3), (In the formula, R _{1 to} R ₄ are the same as those described above, and R ₅ represents an alkyl group having 1 to 4 carbon atoms.) From 3- (2-cyclohexanoyl) propionic esters, 3,4 -A method for producing coumarins, comprising dehydrogenating using a palladium catalyst used in a cyclodehydrogenation reaction in producing dihydrocoumarins.

The 3,4-dihydrocoumarin used in the present invention includes, for example, 3,4-dihydrocoumarin,
5-methyl-3,4-dihydrocoumarin, 6-methyl-
3,4-dihydrocoumarin, 7-methyl-3,4-dihydrocoumarin, 8-methyl-3,4-dihydrocoumarin, 5-ethyl-3,4-dihydrocoumarin, 6-ethyl-3,4-dihydrocoumarin , 7-ethyl-3,4-
Dihydrocoumarin, 8-ethyl-3,4-dihydrocoumarin, 5,6-dimethyl-3,4-dihydrocoumarin,
5,7-dimethyl-3,4-dihydrocoumarin, 5,8
-Dimethyl-3,4-dihydrocoumarin, 6,7-dimethyl-3,4-dihydrocoumarin, 6,8-dimethyl-
3,4-dihydrocoumarin, 7,8-dimethyl-3,4
-Dihydrocoumarin, 5-methyl-6-ethyl-3,4
Dihydrocoumarin, 5-methyl-7-ethyl-3,4 dihydrocoumarin, 5-methyl-8-ethyl-3,4 dihydrocoumarin, 6-methyl-7-ethyl-3,4 dihydrocoumarin, 6-methyl-8 -Ethyl-3,4 dihydrocoumarin, 7-methyl-8-ethyl-3,4 dihydrocoumarin, 5-ethyl-6-methyl-3,4 dihydrocoumarin, 5-ethyl-7-methyl-3,4 dihydrocoumarin 5-ethyl-8-methyl-3,4 dihydrocoumarin, 6-ethyl-7-methyl-3,4 dihydrocoumarin, 6-ethyl-8-methyl-3,4 dihydrocoumarin, 7-ethyl-8-methyl -3,4 dihydrocoumarin and the like, but are not limited thereto.

In the present invention, 3,4-dihydrocoumarins are usually produced by subjecting 3- (2-cyclohexanoyl) propionic acid esters to cyclodehydrogenation reaction in the presence of a palladium catalyst. -Dihydrocoumarins and coumarins separated by distillation are used, but other materials may be used and are not particularly limited. Dehydrogenation from 3,4-dihydrocoumarins to coumarins hardly proceeds even if the reaction is continued without separating and separating the generated 3,4-dihydrocoumarins and coumarins by distillation. It is necessary to use 3,4-dihydrocoumarins excluding coumarins, but there is no problem even if some coumarins are contained in the separated 3,4-dihydrocoumarins.

The palladium catalyst used in the present invention is 3
The product used in the cyclodehydrogenation reaction of-(2-cyclohexanoyl) propionic acid ester is recovered and reused. The catalyst used in the dehydrogenation reaction can be further reused in the dehydrogenation reaction.

The catalyst used in the cyclodehydrogenation of 3- (2-cyclohexanoyl) propionate is a compound of the group IIA, IIIA, IVA or VIA of the periodic table, such as carbon Is a solid metal catalyst in which palladium is supported on at least one carrier selected from the group consisting of, alumina, silica gel, barium sulfate, and the like. Is obtained by a method of impregnating a carrier with a metal and subjecting it to hydrogen reduction at a high temperature, but a commercially available product may be used as it is.

When the amount of the catalyst used in the dehydrogenation of 3,4-dihydrocoumarins is small, the reaction activity is extremely low. On the contrary, when the amount is large, the reaction activity is too high and many by-products are formed. Usually about 0. 4-dihydrocoumarins.
It is used in an amount of 1 to 5% by weight, preferably about 0.5 to 2.5% by weight.

This dehydrogenation reaction is carried out at about 100-350 ° C., preferably at about 230-300 ° C. If the temperature is low, the reaction activity is low, and if it exceeds about 350 ° C., decomposition of the raw material occurs, which is not preferable.

This dehydrogenation reaction can also be carried out using a solvent. Examples of the solvent include phenyl ether, benzyl ether, methyl-α-naphthyl ether, ethylnaphthalene, dimethylbiphenyl, dodecane, tetradecane, tetralin, acetophenone, phenylpropyl ketone, methyl benzoate, dimethyl glutamate and the like.

The dehydrogenation reaction is carried out by heating at a predetermined temperature for several hours to several tens of hours. As a result of the reaction, about 40 coumarins
~ 60% yield.

[0016]

According to the present invention, a method of recovering the catalyst used in the cyclodehydrogenation of 3- (2-cyclohexanoyl) propionic acid esters of the present invention and using it for the dehydrogenation of 3,4-dihydrocoumarins. Has a high selectivity as compared with the method using a new catalyst and can be reused in a dehydrogenation reaction, and its industrial value is great.

[0017]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example 1 Methyl 3- (2-cyclohexanoyl) propionate 3
00g and 50% of 5% palladium supported on activated carbon
2.1 g of the water-containing catalyst was mixed in a 1-liter four-necked flask, and the temperature was 250 ° C. and the number of stirring was 240 rpm under a nitrogen atmosphere.
For 10 hours. Then, raise the temperature to 27 over 1 hour.
The temperature was raised to 0 ° C. Temperature 270 ° C, stirring speed 500rpm
and heated for an additional 15 hours.

After completion of the reaction, the catalyst was filtered and recovered from the reaction mixture. As a result of analyzing the filtrate by gas chromatography, the conversion of methyl 3- (2-cyclohexanoyl) propionate was 99.9%, and coumarin and 3,4-
The yields of dihydrocoumarin were 31.0% and 39.2%, respectively, based on methyl 3- (2-cyclohexanoyl) propionate.

The total amount of the recovered catalyst and 200 g of 3,4-dihydrocoumarin (purity: 98.1%) were mixed in a 1-liter four-necked flask, and heated at 270 ° C. and 50 ° C. under a nitrogen atmosphere.
The reaction was performed at 0 rpm for 28 hours. After completion of the reaction, the catalyst was filtered from the reaction mixture, and the filtrate was subjected to gas chromatography.
As a result, the conversion of 3,4-dihydrocoumarin was 5
The selectivity from 1.5% and 3,4-dihydrocoumarin to coumarin was 86.7%.

Example 2 A total of two batches of the same cyclodehydrogenation reaction as in Example 1 were carried out.
The entire amount of the cyclized dehydrogenated spent catalyst was recovered. 200 g of 3,4-dihydrocoumarin (87.3% of 3,4-dihydrocoumarin, 3.1% of coumarin) obtained by distilling off 3,4-dihydrocoumarin from the entire amount of the recovered cyclized dehydrogenation catalyst and the cyclized dehydrogenation reaction solution was added to 1 liter of Mix in a four-necked flask and place in a nitrogen atmosphere at a temperature of 27
The reaction was performed at 0 ° C. and 500 rpm for 28 hours. After the reaction,
After filtering the catalyst from the reaction mixture, the filtrate was analyzed by gas chromatography. As a result, the conversion of 3,4-dihydrocoumarin was 56.0% and the selectivity from 3,4-dihydrocoumarin to coumarin was 90.3%. there were.

Comparative Example 1 200 g of 3,4-dihydrocoumarin (purity: 98.1%)
Then, 2.0 g of a 50% water-containing catalyst having 5% by weight of palladium supported on activated carbon was mixed in a 1-liter four-necked flask, and reacted at 270 ° C. and 500 rpm for 28 hours in a nitrogen atmosphere. After completion of the reaction, the catalyst was filtered from the reaction mixture, and the filtrate was analyzed by gas chromatography.
Conversion of 3,4-dihydrocoumarin 60.9%, 3,4
83.5% selectivity from dihydrocoumarin to coumarin
Met.

Comparative Example 2 200 g of 3,4-dihydrocoumarin (purity 98.1%)
50 g of palladium supported on 200 g and activated carbon at 5% by weight
% Hydrated catalyst in a 1 liter four-necked flask, and heated at 270 ° C. and 500 rpm under a nitrogen atmosphere.
The reaction was performed for 8 hours. After completion of the reaction, the catalyst was filtered from the reaction mixture, and the filtrate was analyzed by gas chromatography. As a result, the conversion of 3,4-dihydrocoumarin was 48.0%,
Selectivity from 3,4-dihydrocoumarin to coumarin 7
It was 8.4%.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-197478 (JP, A) JP-A-4-82884 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07D 311/08

Claims (1)

(57) [Claims] 1. The general formula (1), (Wherein, R _{1 to} R ₄ each represent a hydrogen atom, a methyl group or an ethyl group, and at least two groups among R _{1 to} R ₄ are hydrogen atoms). Is dehydrogenated in the presence of a palladium catalyst to obtain a compound represented by the general formula (2): (Wherein, R _{1 to} R ₄ are the same as the above-mentioned groups.) In producing a coumarin represented by the general formula (3), (Wherein, R _{1 to} R ₄ are the same as those described above, and R ₅ represents an alkyl group having 1 to 4 carbon atoms).
A process for producing coumarins, comprising dehydrogenating using a palladium catalyst used in a cyclodehydrogenation reaction in producing 3,4-dihydrocoumarins from (2-cyclohexanoyl) propionic esters. .