JPH0399076A - Production of dihydrocoumarin - Google Patents

Abstract

PURPOSE:To enable obtaining of the subject compound which is a synthetic intermediate for coumarin in high yield for a short time by reacting a lower alkyl ester of (2-cyclohexanoyl)propionic acid in the presence of a specific catalyst and alumina under specified conditions. CONSTITUTION:A lower alkyl ester of 3-(2-cyclohexanoyl)propionic acid (CP) is heated in the presence of a Pd catalyst supported on alumina or a carrier other than the alumina and the alumina at 230-260 deg.C for a short time to provide dihydrocoumarin. The heating time is 2-5hr, preferably 2-3hr. The preferred amount of the catalyst used for the reaction is 0.05-1mol%, etc., based on methyl ether of the CP which is a raw material in the case of, e.g. the alumina supporting 3% Pd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Field of Application) The present invention relates to the production of dihydrocoumarin, which is an intermediate in coumarin synthesis.

(Prior Art) Coumarin is an important compound as a flavoring material for perfumes and foods, and as a treatment agent for metal surfaces in plating operations.

Coumarin is currently obtained mainly by extracting plants.

On the other hand, various studies are being conducted regarding its synthesis.

For example, esters of 3-(2-cyclohexanoyl)propionic acid (hereinafter abbreviated as CP) are heated at 295 to 350°C in the gas phase in the presence of a catalyst such as palladium, platinum, or rhodium.
or heating HP or its esters in a liquid phase to 200 to 250°C in the presence of a palladium catalyst to produce hydrocoumarin, and the produced hydrocoumarin to be heated to 200 to 250 °C in the presence of a palladium catalyst, and Attempts have been made to generate coumarin by heating above 400'C in the gas phase in the presence of a catalyst (US Pat. No. 3,442,910).

However, the total yield of hydrocoumarin and coumarin is only about 60 or less. In addition, hexahydrocoumarin obtained by ring-opening CAP with acetic anhydride was prepared in the liquid phase in the presence of a catalyst such as palladium, platinum, rhodium, etc.
It has also been attempted to generate coumarin together with dihydrocoumarin by heating to ~5γ5°C (Japanese Patent Laid-Open No. 49-62
No. 473).

The yields of dihydrocoumarin and coumarin are 34% and 39%, respectively, and the total yield is only about 73%.

Furthermore, attempts have been made to generate coumarin all at once by heating methyl ester of CP to 260° C. in the liquid phase in the presence of the above-mentioned catalyst and co-catalysts such as barium, alumina and other co-catalysts. (Unexamined Japanese Patent Publication No. 181082/1982). Analysis values of the reaction solution obtained by this method by gas chromatography were 30.7% dihydrocoumarin and 60.8% coumarin.
% yield is stated. However, when the present inventor conducted a follow-up test, the analytical value of the reaction liquid showed a high yield, but when distilling the target product from the reaction liquid, it seems that it is a polymer (which cannot be analyzed by gas chromatography) or a high-boiling ester. A large amount of distillation residue remains, making it impossible to obtain a good yield.

Furthermore, for the cyclization of CP to hexahydrocoumarin, phosphoric acid or sulfuric acid was added to the ethyl ester of CP, and 1
A method is known in which hexahydrocoumarin is heated to 155 to 175°C under a reduced pressure of 3 to 14 mmHg and reacted while separating and distilling it (West German Patent Publication No. 2).
No. 309536).

Although it is stated that the yield of hexahydrocoumarin is 94 to 95.5% based on the analysis of the crude distillate and the residue in the reaction vessel, the yield of the rectified product is not mentioned. Additionally, special equipment is required to carry out the reaction while distilling under reduced pressure.

(Problems to be Solved by the Invention) As mentioned above, since the main focus has conventionally been on the production of coumarin, there has been little research into methods for producing only dihydrocoumarin in high yield.

The present inventor conducted a detailed study on the conditions for producing dihydrocoumarin and coumarin by the above dehydrogenation reaction from hexahydrocoumarin produced by dealcoholization and intramolecular ring closure of CP-alkyl ester. As a result, when dehydrogenating hexahydrocoumarin according to the method of JP-A-49-62475, for example, when a palladium-carbon catalyst is used, intense hydrogen gas bubbling occurs at 230-240°C, which is relatively It was found that in a short time, the peak of hexahydrocoumarin in gas chromatography analysis almost disappeared, and the main peak of dihydrocoumarin appeared, and its collapsing ratio was 93%. In other words, it is clear that in this reaction, dehydrogenation of the cyclohexene ring to the aromatic ring proceeds preferentially, producing dihydrocoumarin first, and then the dehydrogenation reaction from dihydrocoumarin to coumarin requires a higher temperature and longer time. Became.

However, in the above dehydrogenation reaction, a small amount of coumarin is always produced together with dihydrocoumarin.

Therefore, it is first necessary to establish a production method for obtaining dihydrocoumarin in high yield in a short period of time.

(Means for Solving the Problems) As a result of repeated research on a method for efficiently producing dihydrocoumarin using CP as a raw material, the present inventor has found that, for example, C
P methyl ester is 240-2 in the presence of palladium catalyst
A cyclization and dehydrogenation reaction occurs at 60° C., and within several hours most of the product is converted to dihydrocoumarin, with some coumarin also being produced.

It was found that this reaction was further accelerated by the presence of alumina.

The present invention is based on this knowledge, and it is possible to prepare 3-(2-cyclohexanoyl)propionic acid or its ester in the presence of a palladium catalyst supported on alumina or a palladium catalyst supported on a carrier other than alumina and alumina.
This method for producing dihydrocoumarin is characterized by heating to 230-260°C, preferably 240-250°C.

The CP ester is preferably a lower alkyl ester such as a 01-C4 alkyl ester.

Although the reaction in the present invention is carried out in the presence of both a palladium catalyst and an alumina catalyst, an alumina-supported palladium catalyst may be used as both catalysts, or a palladium catalyst supported on alumina may be used as both catalysts, or a palladium catalyst supported on alumina may be used as both catalysts. A palladium catalyst and alumina may be used together.

A palladium supported alumina catalyst can be prepared by a known method.

Supports other than alumina can be used as palladium catalysts, such as carbon, barium sulfate, calcium carbonate, diatomaceous earth,
Examples include palladium supported on activated clay and palladium black.

The preferable amount of the catalyst used in the reaction is, for example, in the case of alumina supporting 3% palladium, 0.05 to 0.1 mole or more is used based on the methyl ester of CP as the raw material, and 5% of the palladium catalyst is used. Pd- containing palladium
When C is used in combination with alumina, the former is 0. 5-1
．． 5 mol ax, the latter 5% palladium●0.0 on carbon.
5 to 1.0 times the amount is used.

The reaction is carried out at 230-260°C, preferably about 240°C.

If the reaction is carried out in the absence of alumina, the yield of dihydrocoumarin reaches about 60% after about 4 hours, but if it is carried out in the presence of alumina, a yield of about 75-80% is obtained after 3 hours. be able to.

In any case, if the reaction time is further extended, the yield of dihydrocoumarin decreases, so it is preferable to stop the reaction near the point at which the yield reaches its maximum.

The reaction may be carried out without a solvent or in diphenyl ether, dibenzyl ether or other high boiling point solvent.

Example 1 Four-tube 2 equipped with a stirring device, gas introduction tube, and reflux condenser tube
65 g (0.35 mol) of cyclohexanoylpropionic acid (CP) methyl ester, 124 g (0.1 mol) of 3% palladium-alumina in a 0.0 ml flask.
1 mol%) and passed air over the mantle heater (5 mol%).
The liquid temperature is gradually heated to 250'C (l/h), and the liquid temperature is maintained at 250-259°C by finely adjusting the air flow rate and mantle heater heating. Bubbling of hydrogen gas is observed from around 230°C, and the dehydrogenation reaction progresses. The reaction solution was sampled every hour and the inner part was analyzed by gas chromatography, and the area ratio of each component after 3 hours was as follows.

(The following margins are the same for each table below) Example 2 65.2 g of OF● methyl ester was placed in the same reaction apparatus as Example 1.
(0.35 mol) to 5% palladium-carbon 0. 7 5
9 (0.1 mol%) 0.5 g of alumina was added and a similar solventless reaction was carried out for 3 hours while maintaining the liquid crystal temperature at 245 to 255°C. * Ethylphenol, ** dihydrocoumarin, *** coumarin in gas chromatography. (The same applies to each table below) 48.8 g of reaction solution (quantitative value: DC = 0.2089 mol, C =
0.0364 mol, total 0.2853 mol, yield 81.5
%) (Internal standard for quantitative determination: dipropyl phthalate, reaction solution 5
0. 4 g (quantitative value: DC=0.182 mol, C=
0.0364 mol, total 0.02440 mol, yield 69.
7%) Example 3 In a reactor similar to Example 1, CP●methyl ester 65.2
．． 10.35 mol), 5% baradium-carbon 0.45 g
(0.06 mol %) 0.30 g of alumina was added, the liquid temperature was maintained at 245 to 255° C. without adding a solvent, and the mixture was heated and stirred for 4 hours while passing air in the same manner to cause a reaction. The results of gas chromatography analysis over time are shown below.

Reaction solution + s. 85J (Quantitative value: DC! = 0.2450 mol, O = 0.0354 mol, total 0.2804 mol, yield 80.1%) Example 4 Same as Example 1 Stirring device, gas introduction tube, reflux condensing tube 500 m/l! In a flask were 65.0 g (0.35 mol) of CP-methyl ester, 65 g of diphenyl ether, and 1.36 g (0.35 mol) of 3% palladium-alumina.
11 mol%), and while passing air in the same manner, the liquid temperature was raised to 245 to 245 mol% while heating and stirring on a mantle heater.
It was maintained at 245°C and reacted for 5 hours. The area ratio of each component peak in gas chromatography obtained by sampling the reaction solution over time was as follows.

(Left below) Example 1 In a similar device, 65.2 g of CP-methyl ester1 0.82 g of homemade 4.9% baradium monoxide-alumina (
0.11 mol %) and 0.53 g of alumina (Reference JACS, 72.5651 (1950) The mixture was held and reacted for 4 hours. The results are shown below.

*Octahydrocoumarin (same in the table below) Reaction solution 10.9.6. ! i' (quantitative value: DC=0.20
55 mol, c=o. oe3 mol, total 0.2685 mol,
Yield 76.7%) Example 5 Reaction solution 49.79 (Quantitative value: DC = 0.2 3 5
4 mol, O=0.355 mol, total 0.2709 mol,
Example 6 65 g of CP-methyl ester, 3% palladium-alumina 1. 24 g (0.T mol %) was placed in a 200 ml four-wall flask similar to the above, and the liquid temperature was maintained at 250'C to 255°C for 4 hours while air was passed over a mantle heater to remove methanol and close the ring. At the same time, a dehydrogenation reaction was carried out. After the reaction, the reactor was cooled to remove the 3% palladium-alumina catalyst and washed with methanol.

Methanol was distilled off from the reaction liquid combined with the washing liquid under reduced pressure using an aspirator to obtain 48 g of a reaction liquid.

Immediately subjected to vacuum distillation to bp2mmHg 109-118
Obtained 42.5 g of colorless oil at . The analysis value by gas chromatography was 87.0g of dihydrocoumarin. 3 Oto Og (
0.250 monore), coumarin 12.9 伜. 5.5g (
0.038 mol). Yield 82.3% Reference Example CP-methyl ester 65.2,y(
o. Add only 0.75 g of 5% palladium-carbon and heat and stir on a mantle heater while keeping the liquid temperature at 245-251°C.
Time reacted. The results are shown below.

48.0 g of reaction solution (quantitative value: DC = 0.1738 mol.
C=0.0299 mol, total 0. 2 0 3 7 moles,
(Yield 58.2%) (Effects of the Invention) According to the present invention, dihydrocoumarin can be produced in a high yield in a short time using 3-(2-cyclohexanoyl)propionic acid lower alkyl ester as a raw material. .

(Voluntary) Procedural Amendment 1. Case Description 1999 Patent Application No. 236362 2. Title of the invention Method for producing dihydrocoumarin 3. Relationship with the case of the person making the amendment Patent applicant Address: 4-3-10 Koraibashi, Chuo-ku, Osaka-shi, Osaka Prefecture Name: Fuso Chemical Industry Co., Ltd. Representative: Shozo Akazawa 5, Date of amendment order: Voluntary statement of the contents of the amendment On the 2nd page, line 7, rHPJ is corrected to rcPJ.9 On the same page, on the 5th line from the bottom, ``ring opening'' is corrected to ``r ring closing''.

Same, page 3, line 3, "polymerized products that cannot be made" is corrected to "polymerized products that cannot be made."

"Akmina" in line 5 of page 14 is corrected to "alumina".

Claims (2)

[Claims] (1) 3-(2-cyclohexanoyl)propionic acid lower alkyl ester is heated to 230-260°C for a short time in the presence of a palladium catalyst supported on alumina or a palladium catalyst supported on a carrier other than alumina and alumina. A method for producing dihydrocoumarin, characterized by: (2) The method according to claim 1, wherein the heating time is 2 to 5 hours, preferably 2 to 3 hours.