JP2015059117A - Method for producing 2,6-tetralin dicarboxylic acid dialkyl ester - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inexpensive method for producing a 2,6-tetralin dicarboxylic acid dialkyl ester which is a tetralin derivative conceivably used as a resin raw material, a crystal liquid composition, a polymer modifier, a pharmaceutical intermediate, and the like.SOLUTION: The 2,6-tetralin dicarboxylic acid dialkyl ester can be produced in an appropriate reaction time in high yield with a side reaction such as excessive proceeding of a hydrogenation reaction and the like by carrying out the hydrogenation reaction of a 2,6-naphthalene dicarboxylic acid dialkyl ester using a negligible amount of a noble metal catalyst under specific conditions of the reaction temperature and a hydrogen pressure.

Description

  The present invention relates to a method for producing 2,6-tetralin dicarboxylic acid dialkyl ester which is a tetralin derivative.

  2,6-tetralin dicarboxylic acid dialkyl ester is useful as a liquid crystal composition, a polymer modifier, a pharmaceutical intermediate, and the like as polyester, polycarbonate, polyimide, and polyamide.

  As a method of synthesizing 2,6-tetralin dicarboxylic acid dialkyl ester (hereinafter 2,6-TDCE) represented by the following formula (1), 2,6-naphthalenedicarboxylic acid dialkyl ester represented by the following formula (2) Patent Document 1 discloses a method of hydrogenating (hereinafter, 2,6-NDCE) under a noble metal catalyst.

（式（１）中、Ｒ及びＲ’は、炭素数１〜１０のアルキル基である。ＲとＲ’は、同じアルキル基でも良く、異なるアルキル基でも良い。）

(In Formula (1), R and R ′ are alkyl groups having 1 to 10 carbon atoms. R and R ′ may be the same alkyl group or different alkyl groups.)

（式（２）中、Ｒ及びＲ’は、炭素数１〜１０のアルキル基である。ＲとＲ’は、同じアルキル基でも良く、異なるアルキル基でも良い。）

(In Formula (2), R and R ′ are alkyl groups having 1 to 10 carbon atoms. R and R ′ may be the same alkyl group or different alkyl groups.)

Other methods for deriving a naphthalene ring into a tetralin ring by hydrogenation are shown in Patent Documents 2-6.
In the hydrogenation shown in these documents, a catalyst containing a noble metal such as palladium, ruthenium, rhodium, platinum or the like as a catalyst component is used as a catalyst. However, the amount used is extremely high in order to complete the reaction in a short time. Need a lot of quantity. For example, in the Example of Patent Document 1, a palladium catalyst of 0.33 to 1% by mass is used as a catalyst metal for dimethyl 2,6-naphthalenedicarboxylate as a raw material.

Japanese Patent Laid-Open No. 7-53467 JP 47-12320 A JP 51-125265 A JP-A-6-157406 JP-A-6-199705 JP-A-7-53458

  The production methods of tetralin compounds described in Patent Documents 1 to 6 are not industrially advantageous because they require a large amount of expensive noble metal catalyst. Moreover, the yield of the tetralin compound obtained was not necessarily enough under the influence of side reactions, such as excessive progress of hydrogenation.

  The object of the present invention is to reduce the amount of expensive noble metal catalyst used in the production of 2,6-TDCE by hydrogenation of 2,6-NDCE, and to produce 2,6-TDCE in a high yield with an appropriate reaction time. It is to provide an industrially advantageous method capable of obtaining the above.

  As a result of diligent research, the present inventors have conducted a hydrogenation reaction of 2,6-NDCE using a very small amount of a noble metal catalyst under conditions of a reaction temperature and a hydrogen pressure within a specific range, thereby achieving an appropriate reaction time. Thus, the inventors have found that 2,6-TDCE can be produced in a high yield while suppressing side reactions such as excessive hydrogenation.

（式（１）中、Ｒ及びＲ’は、炭素数１〜１０のアルキル基である。ＲとＲ’は、同じアルキル基でも良く、異なるアルキル基でも良い。）

（式（２）中、Ｒ及びＲ’は、炭素数１〜１０のアルキル基である。ＲとＲ’は、同じアルキル基でも良く、異なるアルキル基でも良い。）
〔２〕
前記貴金属触媒が、パラジウム触媒、及びルテニウム触媒からなる群より選ばれる少なくとも1種である、〔１〕に記載の２，６−テトラリンジカルボン酸ジアルキルエステルの製造方法。
〔３〕
前記貴金属触媒が、パラジウム触媒である、〔１〕に記載の２，６−テトラリンジカルボン酸ジアルキルエステルの製造方法。
〔４〕
水素圧力が３〜１２ＭＰａである、〔１〕〜〔３〕のいずれか一項に記載の２，６−テトラリンジカルボン酸ジアルキルエステルの製造方法。 That is, the present invention is as follows.
[1]
The 2,6-naphthalenedicarboxylic acid dialkyl ester represented by the following formula (2) is allowed to act on hydrogen in the presence of a noble metal catalyst, and the 2,6-tetralindicarboxylic acid dialkyl ester represented by the following formula (1) is obtained. A method for producing a 2,6-tetralindicarboxylic acid dialkyl ester, characterized in that the reaction is carried out under conditions satisfying all of the following (I) to (III).
(I) The amount of the noble metal catalyst used is 0.0005 to 0.03% by mass in terms of the amount of the catalyst noble metal in the noble metal catalyst relative to the 2,6-naphthalenedicarboxylic acid dialkyl ester.
(II) Reaction temperature is 151-230 degreeC
(III) Hydrogen pressure is 1.6 to 15 MPa

(In Formula (1), R and R ′ are alkyl groups having 1 to 10 carbon atoms. R and R ′ may be the same alkyl group or different alkyl groups.)

(In Formula (2), R and R ′ are alkyl groups having 1 to 10 carbon atoms. R and R ′ may be the same alkyl group or different alkyl groups.)
[2]
The method for producing a 2,6-tetralindicarboxylic acid dialkyl ester according to [1], wherein the noble metal catalyst is at least one selected from the group consisting of a palladium catalyst and a ruthenium catalyst.
[3]
The method for producing a 2,6-tetralindicarboxylic acid dialkyl ester according to [1], wherein the noble metal catalyst is a palladium catalyst.
[4]
The method for producing 2,6-tetralindicarboxylic acid dialkyl ester according to any one of [1] to [3], wherein the hydrogen pressure is 3 to 12 MPa.

According to the present invention, 2,6-TDCE, which is a tetralin derivative, can be industrially produced at low cost by hydrogenating 2,6-NDCE using a noble metal catalyst.
Since 2,6-TDCE can be used as a resin raw material such as polyester, polycarbonate, polyimide, and polyamide, a liquid crystal composition, a polymer modifier, a pharmaceutical intermediate, and the like, its industrial significance is great.

Hereinafter, a mode for carrying out the present invention (hereinafter simply referred to as “the present embodiment”) will be described in detail. The following embodiment is
It is the illustration for demonstrating this, and is not the meaning which limits this invention to the following content. The present invention can be implemented with appropriate modifications within the scope of the gist thereof.

[1. Reaction raw material]
2,6-NDCE used as a raw material of the present embodiment is represented by the above formula (2). In formula (2), the alkyl group having 1 to 10 carbon atoms represented by R and R ′ includes a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an n-pentyl group, n -Hexyl group, n-heptyl group, n-octyl group, n-nonyl group, n-decyl group, 2-ethylhexyl group and the like can be mentioned.
From the viewpoint of availability, 2,6-naphthalenedicarboxylic acid dimethyl ester in which R and R ′ are both methyl groups is more preferable as a raw material.
The raw material 2,6-NDCE may contain structural isomers such as 2,7-NDCE and 1,5-NDCE, and impurities such as naphthoic acid alkyl ester and terephthalic acid alkyl ester. , 6-NDCE has a purity of preferably 80% by mass or more, more preferably 90% by mass or more, and still more preferably 95% by mass or more.

[2. Catalyst used for reaction]
As the noble metal catalyst used in the present embodiment, palladium (hereinafter sometimes referred to as Pd), ruthenium (hereinafter sometimes referred to as Ru), rhodium (hereinafter sometimes referred to as Rh), and platinum are preferable. From the viewpoint of high selectivity in the hydrogenation reaction, palladium and ruthenium are more preferable, and palladium is more preferable.

The noble metal catalyst is preferably a catalyst in which a noble metal is supported on a carrier (supported catalyst). Examples of the carrier include carbon (activated carbon), alumina, silica, zeolite, and the like, and carbon is particularly preferable from the viewpoint of availability and cost.
The content of the noble metal in the supported catalyst is preferably 0.1 to 50% by mass, and more preferably 1 to 10% by mass.

  As the catalyst described above, a commercially available catalyst may be used, or a catalyst prepared according to a known method such as an impregnation support method may be used. Further, the catalyst may be dried or hydrated, and it is preferable to use a hydrated catalyst from the viewpoint of safety. Commercially available catalysts include “5% Pd carbon powder PE type (water-containing product)”, “5% Pd carbon powder STD type (water-containing product)” and “10% Pd carbon powder PE type (water-containing product) manufactured by N.E. Pd carbon powder such as “5% Ru carbon powder A type (hydrated product)”, “5% Ru carbon powder B type (hydrated product)”, and “5% Rh carbon powder” (Hydrogen-containing product) "and the like. As described above, it is of course possible to use a dried product.

  The amount of the noble metal catalyst used is preferably 0.0005 to 0.03% by mass, and 0.001 to 0.025% by mass in terms of the amount of noble metal in the catalyst relative to the raw material 2,6-NDCE. Is more preferable, and it is still more preferable that it is 0.002-0.02 mass%. By making the usage-amount of a catalyst into the said range, while being able to obtain 2, 6-TDCE with a high yield, the cost which a catalyst requires can be reduced. In particular, there is a remarkable effect of suppressing the formation of dialkyl 2,6-decalin dicarboxylate (hereinafter referred to as 2,6-DDCE) represented by the following formula (3), which is a byproduct due to an excessive hydrogenation reaction.

（式（３）中、Ｒ及びＲ’は、炭素数１〜１０のアルキル基である。ＲとＲ’は、同じアルキル基でも良く、異なるアルキル基でも良い。）

(In Formula (3), R and R ′ are alkyl groups having 1 to 10 carbon atoms. R and R ′ may be the same alkyl group or different alkyl groups.)

  For example, when a 5% Pd carbon catalyst is used as the catalyst, it is preferably 0.01 to 0.6% by mass in terms of the amount of catalyst used relative to the raw material 2,6-NDCE (the amount of catalyst used in the dry state), It is more preferable that it is 0.02-0.5 mass%, and it is further more preferable that it is 0.04-0.4 mass%.

[3. Solvent used for reaction]
The solvent used in the reaction in the present embodiment is not particularly limited as long as it does not inhibit the reaction. For example, aliphatic hydrocarbon solvents such as heptane, octane, decane, alcohol solvents such as ethanol, isopropanol, tertiary butanol, ethylene glycol, ether solvents such as diethyl ether, tetrahydrofuran, dioxane, ethyl acetate, butyl acetate, etc. And acid solvents such as acetic acid and propionic acid. In addition, the solvent used preferably has a boiling point of 60 ° C. or higher, more preferably 70 ° C. or higher, under atmospheric pressure so that the vapor pressure during the reaction does not become excessive.

  Although the usage-amount of a solvent is not specifically limited, It is preferable that it is the range of 0.5-8 by the mass ratio with respect to 2, 6-NDCE, and it is more preferable that it is the range of 0.8-5. If the mass ratio is in the above range, an excessive amount of solvent is not used, so that the reaction can be carried out with an appropriate reactor volume, and the solvent can be easily separated and recovered.

[4. Reaction conditions]
The hydrogenation reaction of this embodiment is preferably carried out in a pressurized container such as an autoclave. The hydrogen pressure in hydrogenation is preferably 1.6 MPa or more, more preferably 3 MPa or more, and further preferably 3.5 MPa or more. The upper limit of the hydrogen pressure is not particularly limited, but is preferably 15 MPa or less, and more preferably 12 MPa or less. By performing the reaction in the above hydrogen pressure range, the selectivity of the reaction is increased, and an appropriate reaction rate is obtained, and 2,6-TDCE can be produced efficiently.
Since hydrogenation is carried out under heating as shown below, the pressure (total pressure) of the reactor needs to be set in consideration of the vapor pressure of the solvent. That is, the reactor pressure must be maintained at a pressure obtained by adding the vapor pressure of the solvent to the hydrogen pressure shown above. Further, in order to keep the pressure constant, a method of supplying hydrogen to the reactor corresponding to the amount consumed in the reaction can be used.

  The reaction temperature of the hydrogenation reaction of this embodiment is preferably 151 to 230 ° C, more preferably 155 to 210 ° C, and still more preferably 160 to 200 ° C. By carrying out the reaction in the above temperature range, an appropriate reaction rate can be obtained even with a very small amount of catalyst, 2,6-TDCE can be produced efficiently, and the selectivity of the reaction also increases.

The reaction time in this embodiment may be set to an appropriate time according to the progress of the hydrogenation reaction. The progress of the hydrogenation reaction can be grasped, for example, by measuring the flow rate of hydrogen supplied to the reactor. One method to determine the end point of the hydrogenation reaction is to determine whether the total amount of hydrogen supplied from the start of the reaction has reached the theoretical hydrogen consumption, and the other method is to keep the reactor pressure constant. This is a method in which the end point of the reaction is the time when the flow rate of hydrogen supplied is significantly reduced (for example, when the hydrogen flow rate is reduced to less than 1/10 compared to when the reaction was actively progressing). . When the hydrogenation reaction is carried out by the method described in the present invention, since the amount of hydrogen consumed usually decreases rapidly as the reaction end point approaches, it is easy to determine the end point of the reaction. , 6-DDCE can be suppressed, and 2,6-TDCE can be preferably produced.
The reaction time is preferably 10 hours or less from the viewpoint of industrial production efficiency, more preferably within 6 hours, and further preferably within 4 hours.

[5. Reaction method]
The reaction method of the hydrogenation reaction of the present embodiment is not particularly limited, but a batch-type reaction method in which raw materials, a solvent, and a noble metal catalyst are charged in a reactor and the reaction is performed at a predetermined reaction temperature and hydrogen pressure, and A semi-batch type reaction method in which a solvent and a noble metal catalyst are charged and a raw material is supplied to a reactor maintained at a predetermined reaction temperature and hydrogen pressure is exemplified.

[6. Product recovery and purification]
Although 2,6-TDCE in the product obtained in this embodiment is usually dissolved in the solvent although it depends on the amount of the solvent used, for example, after filtering the catalyst from the reaction product, To remove crude 2,6-TDCE.
Further, purification may be performed by means such as recrystallization, distillation or column chromatography.

  The 2,6-TDCE of the present invention can be suitably used as a resin raw material such as polyester, polycarbonate, polyimide, and polyamide, a liquid crystal composition, a polymer modifier, and a pharmaceutical intermediate.

  The method of the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples. In the following examples and comparative examples, the composition indicates an area percentage value obtained by gas chromatography analysis.

<Example 1>
In a 200 mL autoclave with a stirrer (manufactured by SUS316L), 30 g of dimethyl 2,6-naphthalenedicarboxylate (hereinafter 2,6-NDCM), 5% Pd carbon powder (moisture content 50 wt%) PE type 90 mg manufactured by N.E. 50 g of isopropanol was charged. At room temperature, the inside of the autoclave was replaced twice with 1 MPa of nitrogen, and then replaced twice with 1 MPa of hydrogen. Then, after dropping to normal pressure, the temperature in the reactor is raised to 170 ° C., pressurized to 5 MPa with hydrogen, and the hydrogenation reaction is performed with stirring (rotation speed: 1500 rpm) while maintaining the same temperature and pressure. Carried out. Hydrogen was supplied in an amount commensurate with consumption so that the pressure was kept constant.
After 60 minutes, the hydrogen supply amount became very small (5 mL / min or less), so the reaction was judged to be complete, and the mixture was cooled to room temperature. After releasing hydrogen and substituting twice with 1 MPa of nitrogen, the catalyst was separated through the sintered metal, and the reaction solution was extracted. The solvent was removed from the resulting reaction solution to obtain crude dimethyl 2,6-tetralindicarboxylate (hereinafter 2,6-TDCM) (30.1 g). As a result of gas chromatography analysis, the composition of the product was 2,6-NDCM: 0.5%, 2,6-TDCM: 98.0%, dimethyl 2,6-decalin dicarboxylate (hereinafter 2,6). -DDCM): 0.3%. The yield of 2,6-TDCM was 96.7 mol%.

<Example 2>
A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the reaction temperature was 190 ° C.
After 45 minutes, the amount of hydrogen supplied became very small (5 mL / min or less), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (29 0.9 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 3>
A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the amount of 5% Pd carbon powder (water content 50% by weight) PE type was changed to 30 mg.
After 150 minutes, the supply amount of hydrogen became a very small amount (5 mL / min or less), so the reaction was judged to be completed, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (30 0.0 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 4>
A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the amount of 5% Pd carbon powder (water content 50 wt%) PE type was 30 mg and the reaction pressure was 10 MPa.
After 60 minutes, since the amount of hydrogen supplied became very small (5 mL / min or less), the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (29 0.9 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 5>
Hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the amount of 5% Pd carbon powder (water content 50% by weight) PE type was 100 mg and the reaction temperature was 160 ° C. .
After 100 minutes, the amount of hydrogen supplied became a very small amount (5 mL / min or less), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (30 0.1 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 6>
A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the amount of 5% Pd carbon powder (water content 50% by weight) PE type was changed to 150 mg.
After 45 minutes, the amount of hydrogen supplied became very small (5 mL / min or less), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (29 0.8 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 7>
A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the amount of 5% Pd carbon powder (water content 50 wt%) PE type was changed to 300 mg.
After 30 minutes, the amount of hydrogen supplied became a very small amount (5 mL / min or less), so the reaction was judged to be completed, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (30 .2 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 8>
A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the reaction pressure was 3 MPa.
After 300 minutes, the amount of hydrogen supplied became very small (3 mL / min or less), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product was treated in the same manner as in Example 1 with crude 2,6-TDCM (30 0.0 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 9>
The amount of 2,6-NDCM was 15 g, 5% Pd carbon powder (water content 50 wt%) PE type was 45 mg, and the amount of isopropanol was 75 g. , 6-NDCM hydrogenation reaction was carried out.
After 75 minutes, the amount of hydrogen supplied became a very small amount (5 mL / min or less), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (29 .4 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 10>
Example 1 except that 100 mg of 5% Pd carbon powder (water content 50% by weight) PE type and 100 mg of 5% Ru carbon powder (water content 50% by weight) A type manufactured by N.E. Similarly, a hydrogenation reaction of 2,6-NDCM was performed.
After 60 minutes, since the amount of hydrogen supplied became very small (5 mL / min or less), the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (29 0.6 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Example 11>
A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 5 except that 50 g of ethyl acetate was used instead of isopropanol as a solvent.
After 105 minutes, the amount of hydrogen supplied became very small (5 mL / min or less), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (29 0.5 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1.

<Comparative Example 1>
A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the reaction temperature was 130 ° C.
After 360 minutes, the amount of hydrogen supplied became very small (3 mL / min or less), so that the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (21 .3 g) was obtained. In addition, the crystal | crystallization considered to be an unreacted raw material was isolate | separated from the reaction liquid with the sintered metal with the catalyst. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1. Under conditions where the reaction temperature is low, the residual amount of raw material 2,6-NDCM is large and the progress of the reaction is insufficient.

<Comparative Example 2>
2,6-NDCM in the same manner as in Example 1 except that the amount of 5% Pd carbon powder (water content 50% by weight) PE type was 150 mg, the reaction temperature was 150 ° C., and the reaction pressure was 3.5 MPa. The hydrogenation reaction of was carried out.
After 360 minutes, the amount of hydrogen supplied became very small (less than 3 mL / min), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (22 0.6 g) was obtained. In addition, the crystal | crystallization considered to be an unreacted raw material was isolate | separated from the reaction liquid with the sintered metal with the catalyst. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1. Under conditions where the reaction temperature is low, the residual amount of raw material 2,6-NDCM is large and the progress of the reaction is insufficient.

<Comparative Example 3>
The amount of 2,6-NDCM charged is 20 g, the amount of 5% Pd carbon powder (water content 50% by weight) PE type is 1000 mg, the amount of isopropanol is 60 g, the reaction temperature is 140 ° C., and the reaction pressure is 1. A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the pressure was 0 MPa.
After 240 minutes, the amount of hydrogen supplied became very small (less than 3 mL / min), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (20 0.6 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1. Under conditions where the reaction temperature and reaction pressure are low, even if the catalyst concentration is greatly increased, the residual amount of raw material 2,6-NDCM is large, and the progress of the reaction is insufficient.

<Comparative Example 4>
5% Pd carbon powder (water content 50% by weight) Same as Example 1 except that the PE type charge was 1000 mg, the isopropanol charge was 30 g, the reaction temperature was 140 ° C., and the reaction pressure was 3.0 MPa. Then, a hydrogenation reaction of 2,6-NDCM was carried out.
After 60 minutes, the amount of hydrogen supplied became very small (5 mL / min or less), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (30 .2 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1. Under conditions where the amount of catalyst used is excessive, even if the reaction is carried out at a lower reaction temperature, the hydrogenation reaction proceeds excessively, the amount of by-produced 2,6-DDCM increases, and the yield of 2,6-TDCM decreases. ing.

<Comparative Example 5>
The amount of 2,6-NDCM charged is 20 g, the amount of 5% Pd carbon powder (water content 50% by weight) PE type is 400 mg, the amount of isopropanol is 60 g, the reaction temperature is 135 ° C., and the reaction pressure is 2. A hydrogenation reaction of 2,6-NDCM was carried out in the same manner as in Example 1 except that the pressure was 0 MPa.
After 75 minutes, the amount of hydrogen supplied became very small (5 mL / min or less), so the reaction was judged to be complete, and the reaction solution was cooled to room temperature. Thereafter, the product crude 2,6-TDCM (19 0.5 g) was obtained. The results of product analysis and the yield of 2,6-TDCM are shown in Table 1. Although the amount of catalyst used was less than that of Comparative Example 4, the hydrogenation reaction proceeded excessively under the conditions where the amount of catalyst used was excessive, and the yield of 2,6-TDCM decreased.

According to the present invention, hydrogenation of a 2,6-naphthalenedicarboxylic acid dialkyl ester is carried out in an appropriate reaction time by performing a hydrogenation reaction using a very small amount of noble metal catalyst at a specific reaction temperature and hydrogen pressure. 2,6-tetralin dicarboxylic acid dialkyl ester can be synthesized in a high yield while suppressing side reactions such as excessive progress of the reaction.
Since 2,6-tetralin dicarboxylic acid dialkyl ester can be used as a liquid crystal composition, a polymer modifier, a pharmaceutical intermediate or the like as a polyester, polycarbonate, polyimide, or polyamide, its industrial significance is great.

Claims (4)

The 2,6-naphthalenedicarboxylic acid dialkyl ester represented by the following formula (2) is allowed to act on hydrogen in the presence of a noble metal catalyst, and the 2,6-tetralindicarboxylic acid dialkyl ester represented by the following formula (1) is obtained. A method for producing a 2,6-tetralindicarboxylic acid dialkyl ester, characterized in that the reaction is carried out under conditions satisfying all of the following (I) to (III).
(I) The amount of the noble metal catalyst used is 0.0005 to 0.03% by mass in terms of the amount of the catalyst noble metal in the noble metal catalyst relative to the 2,6-naphthalenedicarboxylic acid dialkyl ester.
(II) Reaction temperature is 151-230 degreeC
(III) Hydrogen pressure is 1.6 to 15 MPa

(In Formula (1), R and R ′ are alkyl groups having 1 to 10 carbon atoms. R and R ′ may be the same alkyl group or different alkyl groups.)

(In Formula (2), R and R ′ are alkyl groups having 1 to 10 carbon atoms. R and R ′ may be the same alkyl group or different alkyl groups.) The method for producing a 2,6-tetralin dicarboxylic acid dialkyl ester according to claim 1, wherein the noble metal catalyst is at least one selected from the group consisting of a palladium catalyst and a ruthenium catalyst. The method for producing a 2,6-tetralin dicarboxylic acid dialkyl ester according to claim 1, wherein the noble metal catalyst is a palladium catalyst. The method for producing 2,6-tetralindicarboxylic acid dialkyl ester according to any one of claims 1 to 3, wherein the hydrogen pressure is 3 to 12 MPa.