JP7499396B2 - Method for producing anthracene-9-carboxylic acid, and reaction mixture - Google Patents

Description

The present invention relates to a method for producing anthracene-9-carboxylic acid and a reaction mixture.

Anthracene-9-carboxylic acid is a very useful chemical product as a functional material that is widely used, for example, as a chemical component of various electrical products. Conventionally, techniques have been disclosed for producing anthracene-9-carboxylic acid by a heating reaction in a non-polar organic solvent in the presence of an alkali metal hydroxide (Patent Documents 1 and 2). Another method has been disclosed in which anthracene-9-carboxylic acid can be synthesized by oxidizing 9-anthracenealdehyde using a specific chromium (Cr) complex oxidizing agent (Non-Patent Document 2). Yet another method has been disclosed in which anthracene-9-carboxylic acid is produced by oxidizing anthracene using a compound of a heavy metal such as manganese (Mn) or chromium (Cr) (Non-Patent Document 3).

JP 2002-187867 A JP 2004-018391 A

Helv. Chim. Acta., vol. 2, p. 482 (1919) Synthetic Communications 10(12), pp. 951-956 (1980) Bull. Chem. Soc. Japan, Vol. 62, p. 545 (1989) Tetrahedron 69(42), 8929-8935, 2013 Russ. Phys. Chem. Soc. 1906, 38, 355, 482, 540, 547

However, the present inventors have confirmed that, even if any of the above-mentioned conventional techniques is adopted, at least one of the following problems (1) to (3) arises, making it difficult to put the technique into industrial practical use.
(1) A relatively large amount of the raw material, 9-anthracenealdehyde, remains unreacted.
(2) The undesirable 9,10-anthraquinone is produced as a by-product in relatively large amounts or quantitatively.
(3) In particular, according to the above-mentioned Non-Patent Documents 1 and 2, a burden is imposed on post-treatment of heavy metals or transition metals (e.g., chromium or manganese) that may be harmful to the human body and the environment, and application of the above-mentioned methods to various electrical products regulated by the RoHs/REACH regulations, etc., becomes extremely difficult.

As a result, the development of a technology for safely, easily, and industrially advantageously producing the target substance, anthracene-9-carboxylic acid, without using heavy metal or transition metal oxidation catalysts has not yet reached a stage that is suitable for practical use, and it can be said that the development is still in progress.

The inventors of the present invention thoroughly examined the above-mentioned patent and non-patent documents, and by conducting follow-up tests, recognized the above-mentioned technical problems, and embarked on research and development of a new method for producing anthracene-9-carboxylic acid that could overcome these problems. In order to solve the problems of anthracene-9-carboxylic acid, the target product of the present invention, being easily decarboxylated and converted to anthracene, and being relatively easily converted to 9,10-anthraquinone depending on the reaction process, the inventors analyzed various experimental results and conducted repeated trial and error.

As a result, the inventors discovered a method for producing anthracene-9-carboxylic acid that not only does not reliably produce the unwanted by-product 9,10-anthraquinone, but is also gentle on the human body and the environment without using metal oxidants or metal catalysts made of heavy metals or transition metals, and is also industrially excellent. A detailed analysis of the production method revealed that it is possible to react the raw material 9-anthracenealdehyde with high certainty. Furthermore, in addition to the above-mentioned production method, the inventors also focused on the peculiarities of the reaction mixture containing commercially valuable by-products that are produced by employing the production method, thereby completing the present invention.

One method for producing anthracene-9-carboxylic acid according to the present invention includes a first reaction step in which 9-anthraldehyde is reacted with at least one selected from the group consisting of sodium tert-butoxide and potassium tert-butoxide in an inert solvent at a temperature of -15°C or higher and 10°C or lower.

According to this manufacturing method, a first reaction step is adopted in which 9-anthraldehyde is reacted with at least one selected from the group consisting of sodium tert-butoxide and potassium tert-butoxide in an inert solvent maintained at a relatively low temperature. In this first reaction step, anthracene-9-carboxylic acid and/or a salt thereof can be produced by the reaction mechanism shown in the following chemical reaction formula (Chemical Formula 1) and (a) to (c).

Here, in the following chemical reaction formula (Chemical Formula 1), potassium tert-butoxide is described as a representative example from the group of sodium tert-butoxide and potassium tert-butoxide. Even if sodium tert-butoxide is used instead of potassium tert-butoxide, the same effect as that of this embodiment can be achieved.

(a) Potassium tert-butoxide, which is a base that can also function as a reactant (hereinafter simply referred to as "base"), reacts with the raw material 9-anthracenealdehyde, and the base attacks the aldehyde carbonyl to produce an intermediate species A.
(b) In intermediate species A, due to the presence of a tert-butyl group, which is a cationic stable species with a large leaving ability, the hydride in intermediate species A attacks the tertiary carbon of the tert-butyl group present closer to the molecule of intermediate species A than the carbonyl carbon of 9-anthraldehyde that may be present around intermediate species A, and as a result, intermediate species B can be preferentially produced. Note that the present inventors consider the reaction process of (b) to be a reaction in which intramolecular hydride transfer has a higher priority than attacking the carbonyl carbon of 9-anthraldehyde that may be present around intermediate species A.
(c) Anthracene-9-carboxylic acid (chemical substance X) can be prepared from intermediate species B under acidic solution.

By carrying out the above-mentioned first reaction step, the production of the undesirable by-product 9,10-anthraquinone is suppressed, and anthracene-9-carboxylic acid can be produced with a high degree of certainty. In addition, by employing the first reaction step, anthracene-9-carboxylic acid can be produced with a high degree of certainty without using heavy metals or transition metals such as palladium (Pd), platinum (Pt), manganese (Mn), chromium (Cr), silver (Ag), copper (Cu) or selenium (Se).

The present inventors have also confirmed that the above-mentioned first reaction step produces a salt of anthracene-9-carboxylic acid prior to the target substance anthracene-9-carboxylic acid, and that the reaction mechanisms shown in the following chemical reaction formulas (Chemical Formula 2) and (d) to (f) produce 9-anthracenemethanol and/or a salt of 9-anthracenemethanol prior to the by-product anthracene-9-carboxylic acid as a useful by-product.
(d) The base potassium tert-butoxide reacts with the raw material 9-anthracenealdehyde, and the base attacks the aldehyde carbonyl to produce intermediate species A (same as (a) above).
(e) A portion of the hydride in intermediate species A attacks the carbonyl carbon of 9-anthracene aldehyde that may be present around intermediate species A.
(f) Under acidic solution, 9-anthracenemethanol (chemical substance Y) can be produced.

It is therefore worth noting that not only anthracene-9-carboxylic acid but also 9-anthracenemethanol can be produced without using the above-mentioned heavy metals or transition metals.

The method for producing anthracene-9-carboxylic acid, which includes a second reaction step in which the reaction mixture containing the salt of anthracene-9-carboxylic acid and the salt of 9-anthracenemethanol after the above-mentioned first reaction step is held at a temperature higher than 10°C and lower than 30°C for 2 hours or more, is a preferred embodiment that can produce anthracene-9-carboxylic acid with a higher degree of certainty. The implementation of the second reaction step can contribute to a higher degree of certainty in increasing the yield of the reaction mixture produced by the first reaction step.

However, the present inventors conducted an analysis using HPLC (high performance liquid chromatography) after the above-mentioned second reaction step, and found that the area percentage based on the formation of the salt of the anthracene-9-carboxylic acid (hereinafter also referred to as the "first area percentage") in the above-mentioned reaction mixture after the second reaction step by HPLC analysis was greater than the area percentage based on the formation of the salt of the 9-anthracenemethanol (hereinafter also referred to as the "second area percentage"). This new finding can be said to represent another aspect of the production method of the present invention that focuses on the above-mentioned process (b).

In the present application, the "reaction mixture" includes a "solvent." A typical example of a "solvent" is an inert solvent. In the present embodiment, "after the first reaction step" means after all of the introduction of at least one selected from the group consisting of sodium tert-butoxide and potassium tert-butoxide and the raw material 9-anthracenealdehyde into the inert solvent has been completed.

Also, one reaction mixture of the present invention contains a salt of anthracene-9-carboxylic acid and the aforementioned salt of 9-anthracenemethanol. In addition, the reaction mixture has a first area percentage based on the formation of a salt of anthracene-9-carboxylic acid, which is greater than a second area percentage based on the formation of a salt of 9-anthracenemethanol, as determined by HPLC (high performance liquid chromatography).

This reaction mixture can contain more anthracene-9-carboxylic acid or a salt thereof than 9-anthracenemethanol or a salt thereof. In addition, this reaction mixture can be produced without using heavy metals or transition metals such as palladium (Pd), platinum (Pt), manganese (Mn), chromium (Cr), silver (Ag), copper (Cu) or selenium (Se), so adverse effects on the human body and the environment can be avoided with a high degree of certainty.

According to one method for producing anthracene-9-carboxylic acid of the present invention, the production of the undesirable by-product 9,10-anthraquinone is suppressed, and anthracene-9-carboxylic acid can be produced by a production process that is gentle on the human body and the environment without using transition metals, etc. Also, in one reaction mixture of the present invention, a reaction mixture can be provided in which anthracene-9-carboxylic acid or a salt thereof is produced preferentially over 9-anthracenemethanol or a salt thereof by the above-mentioned reaction mechanism.

FIG. 2 is a high performance liquid chromatograph (HPLC) diagram showing the intermediate stage of the first reaction step in Example 1. FIG. 2 is a HPLC diagram immediately after the second reaction step in Example 1. FIG. 2 is an HPLC diagram of the crude solid material (light brown solid material) obtained after the second reaction step in Example 1. FIG. 2 is an HPLC diagram of the purified solid material (light yellow solid material) obtained after the second reaction step in Example 1. FIG. 2 is an IR spectrum (infrared absorption spectrum) of the purified solid material (light yellow solid material) obtained after the second reaction step in Example 1. 1 is a proton nuclear magnetic resonance ( ¹ H NMR) spectrum of the purified solid material (light yellow solid material) obtained after the second reaction step in Example 1. FIG. 1 is a diagram showing a C-13 nuclear magnetic resonance ( ¹³ C NMR) spectrum of the purified solid material (light yellow solid material) obtained after the second reaction step in Example 1. FIG. 2 is an HPLC diagram of the solid material obtained after the second reaction step (during the filtration step) in Example 1. FIG. 2 is an IR spectrum (infrared absorption spectrum) of a purified solid by-product (yellow solid) obtained after the second reaction step in Example 1. 1 is a diagram showing a proton nuclear magnetic resonance ( ¹ H NMR) spectrum of a purified solid by-product (yellow solid) obtained after the second reaction step in Example 1. FIG. FIG. 2 is a diagram showing a C-13 nuclear magnetic resonance ( ¹³ C NMR) spectrum of a purified solid by-product (yellow solid) obtained after the second reaction step in Example 1. FIG. 1 is a reference diagram of HPLC at an intermediate stage of the first reaction step in Comparative Example 2 when an inert solvent at −25° C. was used.

First Embodiment
The method for producing anthracene-9-carboxylic acid in this embodiment, and a reaction mixture containing the anthracene-9-carboxylic acid or a salt thereof and 9-anthracenemethanol or a salt thereof will be described below.

<Production process of anthracene-9-carboxylic acid and reaction mixture>
The anthracene-9-carboxylic acid and the reaction mixture of the present embodiment can be produced based on the reaction mechanisms shown in the above-described chemical reaction formulas (Chemical Formula 1) and (a) to (c), and an example of a specific process thereof is as follows.

First, a first reaction step is carried out in which 9-anthracene aldehyde is reacted with at least one selected from the group consisting of sodium tert-butoxide and potassium tert-butoxide in an inert solvent (typically an organic solvent). Preferably, toluene or xylene, which is an inert solvent that does not contribute to the reaction of this embodiment, can be used.

Specifically, in the first reaction step, a mixture of at least one base selected from the group consisting of sodium tert-butoxide and potassium tert-butoxide and the raw material 9-anthracenealdehyde, which is mixed substantially uniformly, is added in several batches to the inert solvent kept at a temperature between -15°C and 10°C. After the entire mixture has been added, stirring is continued while maintaining the above-mentioned temperature for a time appropriately selected according to the final desired yield (for example, several hours to half a day, more preferably 8 hours to 12 hours).

At this time, it is preferable to homogenize the mixture as much as possible by stirring it with a stirrer or the like, from the viewpoint of producing anthracene-9-carboxylic acid with a high degree of certainty. The suitable amount of the base is 1.0 to 2.0 equivalents relative to the raw material 9-anthraldehyde. By adjusting the mixture, a product containing the intermediate species A described above can be produced during the reaction. An example of the stirring conditions in this embodiment is simple stirring for about 10 to 15 minutes using a stirrer or a crusher to homogenize the mixture.

The above-mentioned reaction in this embodiment is carried out in the inert solvent. The type of the solvent is not limited as long as it can dissolve and stir the base and the raw materials to make them substantially homogenous, and does not inhibit the reaction in this embodiment. More specifically, toluene or xylene is a suitable example, but any solvent that is inert to the reaction in this embodiment and does not substantially mix with water can be used as the solvent in this embodiment.

Next, in this embodiment, after the first reaction step described above, i.e., after all of the mixture described above has been added to the inert solvent under stirring conditions, stirring is continued for an appropriately selected time (for example, several hours to half a day, more preferably 8 hours to 12 hours) while maintaining the temperature at -15°C or higher and 10°C or lower as described above, thereby making it possible to produce the target 9-anthracenecarboxylic acid in an industrially feasible yield. In order to ensure that the raw material 9-anthracenealdehyde can be reacted with a high degree of certainty, a second reaction step is then carried out in which stirring is continued for at least 2 hours or more.

Here, it is preferable that the second reaction step is continued for a period of time during which the raw material 9-anthraldehyde can be sufficiently consumed in the chemical reaction of this embodiment. From this perspective, the second reaction step is maintained with continued stirring for 12 hours or more (more preferably 24 hours or more, and even more preferably 24 to 48 hours). Most preferably, the second reaction step is continued until the area percentage based on the raw material 9-anthraldehyde is less than 5 area % (more preferably less than 3 area %) as determined by analysis using HPLC (high performance liquid chromatography) in the second reaction step.

In the first reaction step (more preferably, the second reaction step) of this embodiment, due to the presence of the tert-butyl group in the intermediate species A, which is a cationic stable species with a large elimination ability, the hydride in the intermediate species A preferentially attacks the tertiary carbon of the tert-butyl group present in the molecule of the intermediate species A, rather than the carbonyl carbon of the 9-anthraldehyde that may be present around the intermediate species A. This corresponds to the reaction mechanism described in (b) above. As a result, the intermediate species B described above is preferentially produced. Therefore, the reaction mixture of this embodiment may contain at least the salt of the anthracene-9-carboxylic acid by the first reaction step or the second reaction step.

Interestingly, when the inventors attempted a reaction step similar to the first reaction step described above for the above-mentioned process (b) under lower temperature conditions (lower than -20°C) than the above-mentioned temperature conditions (-15°C or higher and 10°C or lower), the results obtained could be interpreted as indicating that attack of the hydride preferentially occurs on the tertiary carbon of the tert-butyl group present in the molecule of intermediate species A, rather than on the carbonyl carbon of 9-anthraldehyde that may be present around intermediate species A. It is therefore noteworthy that it has become clear that the above-mentioned process (b) is further promoted by reacting the specific raw material described above with a base in a low-temperature environment. While continuing the preferential hydride transfer described above, from the viewpoint of preventing a decrease in the yield of anthracene-9-carboxylic acid due to a side reaction in which a portion of the anthracene methoxide produced reacts with the remaining raw material to produce a polymer compound as a by-product, it is preferable to carry out the reaction in an inert solvent at a temperature of -15°C or higher and 10°C or lower (more preferably, -5°C or higher and 5°C or lower, and more preferably, -2°C or higher and 2°C or lower).

In this embodiment, low-temperature water (about 0°C) was then added to the reaction system in the second reaction step, and stirring was continued for a predetermined time (e.g., about 1 to 2 hours), after which a filtration process was performed to filter out the solids. As a result, the filtrate obtained was separated into an organic layer and an aqueous layer (a layer containing chemical substances that dissolve in water). The inventors have confirmed that the ochre solid material collected by filtration at this time contains 9-anthracenemethanol, a by-product described below.

The aqueous layer obtained by the above-mentioned filtration process, from which the raw materials 9-anthraldehyde and/or 9-anthracenemethanol and other reaction by-products have been extracted, contains a salt of anthracene-9-carboxylic acid. Therefore, an acidic solution (e.g., concentrated hydrochloric acid) is dripped into the aqueous layer, which is kept at a low temperature (e.g., above 0°C and below 10°C), until the pH value becomes 2 or less (more preferably, 1 or less).

As a result, the solid substance precipitated from the aqueous layer is filtered off, the filtered solid is sprinkled on the filter cake, the filter cake is washed until the pH value of the washing liquid is approximately neutral, and then the cake is dried to obtain a light brown solid substance containing anthracene-9-carboxylic acid (chemical substance X). After the light brown solid substance is dried, the light brown solid substance is subjected to reflux dispersion treatment using, for example, chloroform for about 1 hour, and then cooled to room temperature while stirring. The resultant product is collected by filtration and dried under reduced pressure to obtain a light yellow solid substance containing purified anthracene-9-carboxylic acid (chemical substance X). Therefore, it has become clear that the reaction mixture of this embodiment can be realized to contain at least the anthracene-9-carboxylic acid or a salt thereof and 9-anthracenemethanol or a salt thereof by carrying out the first reaction step or the second reaction step.

<Production process of 9-anthracenemethanol and reaction mixture>
The 9-anthracenemethanol and the reaction mixture of this embodiment can be produced based on the reaction mechanisms shown in the chemical reaction formula (Chemical formula 2) and (d) to (f) already explained, and an example of the specific treatment is as follows. Note that the description overlapping with the production method of anthracene-9-carboxylic acid may be omitted.

First, as in the above-mentioned method for producing anthracene-9-carboxylic acid, a reaction is carried out under the conditions described in the reaction mechanism (a), resulting in the production of intermediate species A.

Then, some of the hydrides in the intermediate species A can attack the carbonyl carbon of 9-anthraldehyde, which is a raw material that may be present around the intermediate species A. As already mentioned, in this embodiment, the attack on the tertiary carbon of the tert-butyl group present in the molecule of the intermediate species A can be preferentially performed over the attack on the carbonyl carbon of 9-anthraldehyde. However, when some of the hydrides in the intermediate species A attack 9-anthraldehyde that may be present around the intermediate species A, a so-called Tishchenko type reaction occurs, and the corresponding ester derivative is produced from the intermediate species A, and 9-anthracene methoxide can be produced from 9-anthracene aldehyde.

In this embodiment, a reaction similar to that in the second reaction step is then carried out in the same manner as in the above-mentioned method for producing anthracene-9-carboxylic acid. Low-temperature (about 0°C) water is added to the reaction mixture in the second reaction step, and stirring is continued for a predetermined time (e.g., about 1 to 2 hours), after which a filtration process is carried out. At this time, as described above, the ochre solid material collected by the filtration process contains the by-product 9-anthracenemethanol.

The ocher solid material collected by the filtration process is washed with an inert solvent (e.g., toluene) and warm water at about 50°C, and then dried under reduced pressure to obtain a pale orange solid material. This pale brown solid material is dissolved in, for example, toluene, heated to a reflux temperature, and then filtered while hot at about 90°C to obtain yellow needle crystals. By drying the yellow needle crystals under reduced pressure, a yellow solid material containing 9-anthracenemethanol (chemical substance Y), that is, a material containing purified 9-anthracenemethanol (chemical substance Y), is obtained. Therefore, in light of the manufacturing process of 9-anthracenemethanol in this embodiment, it has become clear that the reaction mixture of this embodiment can be realized to contain at least the anthracene-9-carboxylic acid or a salt thereof and 9-anthracenemethanol or a salt thereof by carrying out the first reaction step or the second reaction step.

<Example>
The above-mentioned embodiments will be described in detail through the following examples, but the scope of the present invention and the embodiments are not limited by the descriptions of the examples.

Example 1
[Regarding anthracene-9-carboxylic acid]
A mixture of 100.3 g (0.5 mol) of 9-anthraldehyde as a raw material and 78.8 g (0.7 mol) of potassium tert-butoxide as a base was gradually added to 1700 mL (milliliters) of toluene as an inert solvent at −2° C. with stirring to obtain a reaction mixture. Thereafter, the reaction mixture was kept at −1° C. or higher and 1° C. or lower for about 12 hours while continuing to stir the reaction mixture. This corresponds to the first reaction step in the first embodiment.

In this example, the mixture was then further held at room temperature (about 25°C) for a predetermined time (e.g., about 14 hours). This corresponds to the second reaction step in the first embodiment.

In this example, after it was confirmed that the area percentage based on the raw material 9-anthraldehyde was less than 3 area%, a so-called work-up process was performed in which 1000 mL of water at about 0°C was added and stirred for about 1 hour.

Then, a filtrate consisting of an organic layer (toluene layer) and an aqueous layer was obtained by filtering the solid substances in the reaction mixture. The filtrate was separated into an aqueous layer and an organic layer (toluene layer). An organic solvent for extraction (such as toluene) was then added to the aqueous layer and the separation process was carried out several times, after which the aqueous layer was cooled to 5°C or lower. Then, concentrated hydrochloric acid was added dropwise to the aqueous layer while stirring it until the pH value was 1 or lower.

As a result, the precipitated solid material was collected by filtration, and the filter cake was washed with water (water treated for drinking water) until the pH value of the filtrate was approximately neutral, and then dried to obtain 53.06 g of a light brown solid material as a crude solid material. The crude solid material was subjected to reflux dispersion treatment using chloroform for approximately 1 hour, and then allowed to cool to room temperature (approximately 25°C) while stirring, and then collected by filtration and dried under reduced pressure to obtain 43.83 g of a refined light yellow solid material.

In this example, the purity of the finally obtained anthracene-9-carboxylic acid was 95.02% by HPLC analysis, and the yield of anthracene-9-carboxylic acid was 39.4%.

[About 9-anthracenemethanol]
Next, 9-anthracenemethanol obtained as a by-product in the process for producing anthracene-9-carboxylic acid in this embodiment (Example 1) will be described.

In this example, the ochre solid material filtered out in the filtration step after the above-mentioned work-up treatment was collected, washed with toluene and warm water at about 50°C, and dried to obtain 25.6 g of a pale orange solid material as a crude solid material. The pale orange solid material was dissolved in toluene, heated to a reflux temperature, and dissolved. After hot filtration at about 90°C, recrystallization was performed to obtain yellow needle crystals. The yellow needle crystals were subjected to a reduced pressure drying treatment to obtain 18.0 g of a refined yellow solid material.

In this example, the purity of the final 9-anthracenemethanol obtained by HPLC analysis was 98.75%, and the yield of 9-anthracenemethanol was 17.3%.

As described above, in this example, anthracene-9-carboxylic acid and 9-anthracenemethanol were obtained. Based on the raw material 9-anthraldehyde, the total yield of anthracene-9-carboxylic acid and 9-anthracenemethanol as a crude solid material was 72.34%, and the yield of the purified solid material was 56.7%.

[About the results of various analyses]
The results of various analyses of the anthracene-9-carboxylic acid and the by-product 9-anthracenemethanol obtained in this example are described below.

Figure 1 is a high performance liquid chromatograph (HPLC) diagram of the intermediate stage of the first reaction step in Example 1. Also, Figure 2 is a diagram of the HPLC immediately after the second reaction step in Example 1. Also, Figure 3 is a diagram of the HPLC of the solid material before purification, i.e., the crude solid material (light brown solid material) obtained after the second reaction step in Example 1. Note that in Figure 1, "9AC" means anthracene-9-carboxylic acid, and "9AM" means 9-anthracenemethanol. Also, "Q" in Figure 1 means 9,10-anthraquinone.

Also, Fig. 4 is a diagram of HPLC of the purified solid material (pale yellow solid material) obtained after the second reaction step in Example 1. Also, Fig. 5 is a diagram of the IR spectrum (infrared absorption spectrum) of the purified solid material (pale yellow solid material) obtained after the second reaction step in Example 1. Also, Fig. 6 is a diagram of the proton nuclear magnetic resonance ( ¹ H NMR) spectrum of the purified solid material (pale yellow solid material) obtained after the second reaction step in Example 1. Also, Fig. 7 is a diagram of the ¹³ C nuclear magnetic resonance ( ¹³ C NMR) spectrum of the purified solid material (pale yellow solid material) obtained after the second reaction step in Example 1.

First, as shown in Figure 1, it can be seen that in the middle of the first reaction step, a salt of anthracene-9-carboxylic acid and a salt of 9-anthracenemethanol are produced in competition with each other. The raw material, 9-anthraldehyde, is also confirmed to be in an unreacted state. In addition, the presence of the undesirable by-product 9,10-anthraquinone is confirmed, but its production is sufficiently suppressed.

As can be seen from FIG. 2, immediately after the second reaction step, the salt of anthracene-9-carboxylic acid is produced in preference to the salt of 9-anthracenemethanol. Specifically, the area percentage based on the production of the salt of anthracene-9-carboxylic acid (first area percentage) was 40.35 area%, and the area percentage based on the production of the salt of 9-anthracenemethanol (second area percentage) was 38.62 area%, confirming that the first area percentage is significantly larger than the second area percentage. Furthermore, the raw material 9-anthraldehyde was hardly observed. The area percentage based on the raw material 9-anthraldehyde was less than 2 area%, more specifically, a low value of 1.72 area%. Furthermore, the production of the undesirable by-product 9,10-anthraquinone was such that it could be eliminated by purification.

In addition, since the first area percentage value (95.02 area%) of the pale yellow solid material shown in FIG. 4 is greater than the first area percentage value (85.87 area%) of the pale brown solid material shown in FIG. 3, it is confirmed that a higher purity salt of the anthracene-9-carboxylic acid can be obtained by the purification process.

Furthermore, Figures 5 to 7 show that the chemical produced by the second reaction step is anthracene-9-carboxylic acid.

Next, we will explain the results of various analyses focusing on 9-anthracenemethanol obtained as a by-product in this example (Example 1).

FIG 8 is a diagram of HPLC of the solid material (filtered solid material) obtained during the filtration step after the second reaction step in Example 1. FIG 9 is a diagram of the IR spectrum (infrared absorption spectrum) of the purified solid material (yellow solid material) which is a by-product obtained after the second reaction step in Example 1. FIG 10 is a diagram of the proton nuclear magnetic resonance ( ¹ H NMR) spectrum of the purified solid material (yellow solid material) which is a by-product obtained after the second reaction step in Example 1. FIG 11 is a diagram of the ¹³ C nuclear magnetic resonance ( ¹³ C NMR) spectrum of the purified solid material (yellow solid material) which is a by-product obtained after the second reaction step in Example 1.

First, as shown in the HPLC analysis in Figure 8, the yellow solid material obtained by purifying the solid material collected during the filtration process shows a very high purity value (98.75%) for 9-anthracenemethanol.

Furthermore, Figures 9 to 11 show that the yellow solid substance described above is 9-anthracenemethanol.

Example 2
In this example, each treatment was carried out under the same conditions as those in Example 1, except that xylene was used as the inert solvent instead of toluene in Example 1. Therefore, descriptions overlapping with those in Example 1 may be omitted.

In this example, 50.28 g of crude solid material (light brown solid material) was obtained after the second reaction step.

The crude solid material was then subjected to reflux dispersion treatment using chloroform for approximately 1 hour, and then allowed to cool to room temperature (approximately 25°C) while stirring. The mixture was then filtered and dried under reduced pressure to obtain 31.0 g of a purified pale yellow solid material.

In this example, the purity of the finally obtained anthracene-9-carboxylic acid was 96.09% by HPLC analysis, and the yield of anthracene-9-carboxylic acid was 27.9%.

In addition, for the by-product 9-anthracenemethanol, the yield of a light orange solid material as a crude solid material was 22.8%.

(Comparative Example 1)
Each treatment was carried out under the same conditions as in Example 1, except that 0.3 g (50 mmol) of 9-anthraldehyde as a raw material and 14 mL (70 mmol) of 5 mol/L sodium methoxide as a base were slowly added separately to 170 mL (milliliter) of toluene as an inert solvent at -1° C. to obtain a reaction mixture. Therefore, the description overlapping with that in Example 1 may be omitted.

After completing all of the above-mentioned addition processes, the reaction mixture was analyzed using HPLC. As a result, not only anthracene-9-carboxylic acid or its salt, but also 9-anthracenemethanol or its salt was not detected. On the other hand, the raw material 9-anthraldehyde and the product 9,10-anthraquinone were detected by the HPLC method. The reaction between 9-anthraldehyde and sodium methoxide stopped midway.

The above results suggest that in order to obtain anthracene-9-carboxylic acid and 9-anthracenemethanol with a high degree of certainty, it is preferable to use at least one base selected from the group consisting of sodium tert-butoxide and potassium tert-butoxide to promote attack of the tert-butyl group present in the molecule by the hydride contained in intermediate species A itself.

(Comparative Example 2)
Each treatment was carried out under the same conditions as those in Example 1, except that 10% of each material in Example 1 was used and toluene adjusted to −25° C. was used as an inert solvent. Therefore, descriptions overlapping with those in Example 1 may be omitted.

Figure 12 is a reference diagram of an HPLC result at an intermediate stage of the first reaction step in Comparative Example 2, when an inert solvent at -25°C was used. From Figure 12, it can be seen more clearly than from the results shown in Figure 2 that at -25°C, the salt of anthracene-9-carboxylic acid is produced in preference to the salt of 9-anthracenemethanol. On the other hand, it was confirmed that a large amount of the raw material, 9-anthraldehyde, was left unreacted.

In this comparative example, the purity of the final anthracene-9-carboxylic acid as determined by HPLC analysis and the yield of anthracene-9-carboxylic acid were both less than 10%.

(Comparative Example 3)
According to Example 1 disclosed in the above-mentioned Patent Document 2 (JP 2004-018391 A), 5.15 g of 9-anthraldehyde, 40 g of xylene, and 2.7 g of finely ground potassium hydroxide were charged into a reaction vessel having an internal volume of 200 mL and equipped with a stirrer. Thereafter, the temperature inside the reaction vessel was set to 50° C. with stirring, and maintained for 5 hours.

As a result, it was confirmed that trace amounts of anthracene-9-carboxylic acid and 9-9-anthracenemethanol were produced in the initial stage, but the raw material, 9-anthraldehyde, did not substantially react.

In addition to this Comparative Example 3, an experiment similar to Comparative Example 3 was conducted by changing the temperature inside the reaction vessel described above, and the results were similar to those of Comparative Example 3.

[List of Examples and Comparative Examples]
Below is a table summarizing the results of each of the above-mentioned Examples and Comparative Examples. In order to make the table easier to read, the word "about" may be omitted from the numerical values in the table. In Table 1, "9AC" means anthracene-9-carboxylic acid, and "9AM" means 9-anthracenemethanol. In addition, the solvent "TL" means toluene, and "XL" means xylene. In addition, the base "tert-BuOK" means potassium tert-butoxide, and "CH ₃ O-Na" means sodium methoxide. In addition, in each yield, "ND" means that the corresponding chemical substance was not detected, or was present in an amount below the detection limit.

As described above, in Examples 1 and 2, it was confirmed that anthracene-9-carboxylic acid was produced in preference to 9-anthracenemethanol, and that each chemical substance could be produced in high yield, yield, and purity.

The above-mentioned embodiments and examples do not limit the present invention in any way. Modifications that fall within the scope of the present invention, including other combinations of the above-mentioned embodiments and examples, are also included in the scope of the claims.

The method for producing anthracene-9-carboxylic acid of the present invention and the reaction mixture of the present invention can be widely used as useful chemical substances or their production methods for materials for various applications (for example, functional materials or intermediates thereof used in various electrical products).

Claims (5)

The method includes a first reaction step of reacting 9-anthraldehyde with at least one selected from the group consisting of sodium tert-butoxide and potassium tert-butoxide in an inert solvent at a temperature of from -15°C to 10°C,
Method for the preparation of anthracene-9-carboxylic acid. A second reaction step is included in which the reaction mixture containing the salt of anthracene-9-carboxylic acid and the salt of 9-anthracenemethanol after the first reaction step is maintained at a temperature higher than 10° C. and not higher than 30° C. for 2 hours or more.
The method for producing anthracene-9-carboxylic acid according to claim 1. The content of palladium (Pd), platinum (Pt), manganese (Mn), chromium (Cr), silver (Ag), copper (Cu) or selenium (Se) in the reaction mixture after the first reaction step is less than 0.01 mass%.
The method for producing anthracene-9-carboxylic acid according to claim 1 or 2. After the second reaction step, the production of 9,10-anthraquinone in the reaction mixture as determined by HPLC (high performance liquid chromatography) is less than 5 area % in terms of area percentage.
The method for producing anthracene-9-carboxylic acid according to claim 2. a first area percentage based on the formation of a salt of the anthracene-9-carboxylic acid is greater than a second area percentage based on the formation of a salt of the 9-anthracenemethanol, the first area percentage being determined by HPLC (high performance liquid chromatography) analysis of the reaction mixture after the second reaction step;
The method for producing anthracene-9-carboxylic acid according to claim 2.