JP5078490B2 - Method for producing carboxylic acid - Google Patents

Description

  The present invention relates to a method for producing a carboxylic acid.

  High-boiling aprotic polar solvents having boiling points of 100 ° C. or higher are highly miscible with water, have high polarity, can dissolve inorganic salts, and can react at higher temperatures, so organic synthesis It is widely used as a solvent. In particular, oxidation reactions in these solvents have been extensively studied.

  As a method for oxidizing alcohol in these high boiling point aprotic polar solvents, a method of oxidizing in an oxygen atmosphere using vanadium or a palladium compound as a catalyst (Patent Document 1, Non-Patent Document 1), and a nitrogen oxide as an oxidizing agent. And a method of oxidizing using chromic acid (Patent Document 2, Non-Patent Document 2) and a DMSO oxidation method using DMSO activator using dimethyl sulfoxide (DMSO) as a solvent (Non-Patent Document 2) are known. ing.

However, in these methods, the obtained oxidation product is an aldehyde, and carboxylic acid cannot be obtained.
JP 2005-506984 A JP 55-49368 A K. P. Peterson and R.M. C. Larock, J. et al. Org. Chem. 63 (1998) Noguchi Laboratory Time Report, 22 (1979)

In the oxidation methods such as the above-mentioned patent documents and non-patent documents, the reaction proceeds only to the aldehyde, and carboxylic acid cannot be obtained.
Accordingly, an object of the present invention is to provide a method for producing a carboxylic acid from an aromatic alcohol or an aromatic aldehyde in a high boiling aprotic polar solvent having a boiling point of 100 ° C. or higher.

  The manufacturing method of carboxylic acid which solves said subject is the following general formula (1) of a raw material.

(Wherein Ar ₁ represents an aromatic ring which may have a substituent) or the following general formula (2)

(In the formula, Ar ₂ represents an aromatic ring which may have a substituent.) The aromatic aldehyde represented by the formula is oxidized via a catalyst in the presence of an aprotic polar solvent having a boiling point of 100 ° C. or higher. And a step of adding 0.01 to 20 times by weight of water with respect to the raw material.

  Moreover, the manufacturing method of carboxylic acid which solves said subject is the following general formula (1) of a raw material.

(Wherein Ar ₁ represents an aromatic ring which may have a substituent) or the following general formula (2)

(In the formula, Ar ₂ represents an aromatic ring which may have a substituent.) 0.01 wt.% Of the aromatic aldehyde represented by an aprotic polar solvent having a boiling point of 100 ° C. or higher and the raw material It has the process of oxidizing through a catalyst in presence of water more than twice and below 20 weight times.

  According to the present invention, a carboxylic acid can be produced from an aromatic alcohol or an aromatic aldehyde in a high-boiling aprotic polar solvent having a boiling point of 100 ° C. or higher.

Hereinafter, the present invention will be described in detail.
The method for producing carboxylic acid according to the present invention comprises the following general formula (1)

(Wherein Ar ₁ represents an aromatic ring which may have a substituent) or the following general formula (2)

(In the formula, Ar ₂ represents an aromatic ring which may have a substituent.) The aromatic aldehyde represented by the formula is oxidized via a catalyst in the presence of an aprotic polar solvent having a boiling point of 100 ° C. or higher. And a step of adding 0.01 to 20 times by weight of water with respect to the raw material.

  In addition, the method for producing a carboxylic acid according to the present invention comprises a raw material having an aromatic alcohol represented by the above general formula (1) or an aromatic aldehyde represented by the above general formula (2) having a boiling point of 100 ° C. or higher. It has the process of oxidizing via a catalyst in presence of 0.01 weight times or more and 20 weight times or less of water with respect to the protic polar solvent and the said raw material.

The water is preferably added when the raw material aldehyde is present.
It is preferable that the catalyst in which the amount of water is 1 to 10 times by weight with respect to the raw material is a palladium compound.

The aprotic polar solvent is preferably one or more selected from dimethyl sulfoxide, N-methylpyrrolidone and dimethylformamide.
It is preferred that the aromatic alcohol is 5-hydroxymethyl-2-furfural.

The water preferably contains 0.5 to 4 equivalents of a strong base with respect to the total number of hydroxy groups or aldehyde groups in the raw material.
The method for producing a carboxylic acid according to the present invention comprises a step of oxidizing a raw material aromatic alcohol or aromatic aldehyde via a catalyst in a high boiling aprotic polar solvent having a boiling point of 100 ° C. or higher, And a step of adding 0.01 to 20 times by weight of water.

  By adding water to the reaction system, an aldehyde hydrate is formed, and oxidation can proceed to carboxylic acid. Moreover, when the oxidation rate from aldehyde to carboxylic acid is slow, the oxidation rate to carboxylic acid can be increased by adding a strong base aqueous solution by the Cannizzaro reaction.

  The aromatic alcohol has a hydroxymethyl group bonded to an aromatic ring and has the following general formula (1)

(Wherein, Ar ₁ represents an aromatic ring which may have a substituent).
Moreover, as an aromatic aldehyde, it has an aldehyde group couple | bonded with the aromatic ring, and following General formula (2)

(Wherein, Ar ₂ represents an aromatic ring which may have a substituent).
These aromatic alcohols or aromatic aldehydes may be polyfunctional or may have a hydroxymethyl group and an aldehyde group at the same time. Specific examples thereof include 5-hydroxymethyl-2-furfural, 2,5-bishydroxymethylfuran, 2,5-diformylfuran, 2-carboxy-5-formylfuran, 4-hydroxymethyl-2-furfural, 2,4-bishydroxymethylfuran, 2,4-diformylfuran, 2-carboxy-4-formylfuran, 2-hydroxymethyl-4-furfural, 4-carboxy-2-formylfuran, 4-hydroxymethyl-3 -Furfural, 3,4-bishydroxymethylfuran, 3,4-diformylfuran, 3-carboxy-4-formylfuran, benzyl alcohol, benzaldehyde and the like can be exemplified, but are not necessarily limited thereto.

As a catalyst for promoting the reaction, a noble metal such as palladium, platinum or rhodium can be used, and a palladium compound is preferable.
Specific examples thereof include palladium acetate, palladium chloride, palladium bromide, palladium sulfate, palladium nitrate, palladium oxide, and complex compounds thereof, but are not necessarily limited thereto. These palladium compounds may be used alone or in combination of two or more. Particularly preferred is palladium acetate. Moreover, it is preferable that palladium which is a metal component is bivalent.

  The method for producing carboxylic acid according to the present invention is as follows. In the present invention, at least one of an aromatic alcohol or an aromatic aldehyde and at least one of a divalent palladium compound are oxidized in an aprotic polar solvent in the presence of oxygen. The aprotic polar solvent is not particularly limited as long as it has a boiling point of 100 ° C. or higher, does not inhibit the oxidation reaction, and is stable under the reaction conditions, but preferably dimethyl sulfoxide, N-methyl Examples include pyrrolidone and dimethylformamide. These solvents may be used alone or in combination of two or more. If the amount of the solvent in the present invention is too large, it is difficult to remove the solvent in the carboxylic acid isolation step, and this is not economically preferable. Moreover, when there is too little, reaction will not fully advance. Therefore, it is preferably 5 to 50 times the raw material, more preferably 10 to 20 times the raw material.

  The catalyst is preferably added in an amount of 0.1 mol% or more and 20 mol% or less, more preferably 1 mol% or more and 5 mol% or less with respect to 1 mol of the raw material. If it is more than 20 mol, it is not economically preferable, and if it is less than 0.1 mol%, the reaction rate is lowered and a long reaction time is required, which is not preferable.

  Further, a base may be added to promote oxidation by the catalyst. Since the base to be added also affects side reactions, a weak base is preferable to a strong base. For example, alkali metal carbonates and bicarbonates such as sodium carbonate, potassium carbonate, sodium bicarbonate, potassium bicarbonate, sodium acetate, and potassium acetate, alkaline earth metals such as carbonate, magnesium carbonate and calcium carbonate, and weak acids And tertiary amines such as pyridine and triethylamine are preferred. The addition amount is preferably 0.1 mol or more and 4 mol or less, more preferably 0.5 mol or more and 2 mol or less, with respect to 1 mol of the raw material. Although it is possible to carry out the reaction without adding these weak bases, the reaction rate is slow and the reaction takes time if no addition or a small amount is added.

The oxidizing agent may be oxygen or a gas mixture containing oxygen, and can be introduced by bubbling, normal pressure, or pressure.
The reaction temperature for the oxidation is 30 ° C. or higher and 150 ° C. or lower, preferably 60 ° C. or higher and 120 ° C. or lower.

The reaction time varies depending on the type and concentration of the raw material, the reaction temperature, the presence or absence of a base, etc., but is usually about 5 to 72 hours.
Next, the water addition process will be described in detail. Water is necessary to form aldehyde hydrates and proceed oxidation to carboxylic acids. Water may be added in advance before the reaction or during the reaction, but it is preferably added in the presence of an aldehyde in order to carry out the reaction efficiently. If the amount added is too large, the oxidation reaction is inhibited, so the reaction rate is remarkably reduced. If the amount added is too small, hydrates cannot be formed and the carboxylic acid cannot be oxidized. Accordingly, the amount of water added is preferably 0.01 to 20 times the weight of the raw material. If the amount of water added is 0.01 weight times or more, it is possible to oxidize to carboxylic acid, but depending on the raw material, the oxidation rate may be very slow. In addition, as the amount of water added increases, the oxidation reaction is inhibited, and the reaction rate may become slower. Therefore, the amount of water added is more preferably 1 to 10 times the weight of the raw material. Moreover, although the water produced | generated in an oxidation process can also be utilized, since the production amount is small, it is preferable to add separately.

  When the oxidation rate of aldehyde to carboxylic acid is slow, the addition of a strong base aqueous solution can promote the formation of hydrates and further promote the production of carboxylic acid by the Cannizzaro reaction. Examples of the strong base include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide. If the amount added is large, it promotes the progress of side reactions and causes a decrease in yield. If the amount is small, the effect of producing carboxylic acid is low. More preferably, it is 1 mol or more and 2 mol or less.

  In the present invention, after completion of the reaction, the carboxylic acid can be isolated from the resulting mixed solution containing the carboxylic acid by distillation, sublimation, or reprecipitation with an acid after dilution with water. Moreover, if the produced carboxylic acid is insoluble in the aprotic polar solvent, it can be isolated by filtration. The filtrate at this time can be used repeatedly as a solvent for the oxidation reaction.

Hereinafter, the present invention will be described more specifically with reference to examples.
Example 1
A 25 mL flask equipped with a cooling tube and an oxygen balloon with a three-way cock was prepared. To this flask, raw materials 5-hydroxymethylfurfural (0.63 g; 5 mmol), palladium acetate (0.056 g; 0.25 mmol), sodium bicarbonate (0.84 g; 10 mmol), dimethyl sulfoxide 10 mL ( The water content was 0.08 times the weight of the raw material). While stirring, a pump was attached to the three-way cock, and after reducing the pressure, the cock was switched and oxygen was introduced from the oxygen balloon. This operation was repeated three times to replace the air in the flask with oxygen. It was immersed in an oil bath set at 80 ° C. and held for 20 hours.

Thereafter, 2 mL of 5N aqueous sodium hydroxide solution (water added amount is 3.2 times by weight of raw material, strong base added amount is 2 mol per mol of raw material, sodium hydroxide 0.4 g: 10 mmol), Hold for 5 hours. The mixture was cooled to room temperature and diluted with 10 mL of water. Hydrochloric acid was added to this solution until the pH was 1 or less. The yield of precipitated crude 2,5-furandicarboxylic acid was 0.48 g, and the yield was 62 mol%. Moreover, the analysis result by ¹ H-NMR (DMSO-d6, 20 ° C.) is δ: 3.4 (s, 2H, —OH), δ: 7.2 (s, 2H, furan ring). Matched the thing.

Example 2
In a 100 mL three-necked flask equipped with a condenser, fructose (5.0 g; 28 mmol), Amberlyst 15 Dry (registered trademark, 2.0 g, Organo Corporation), dimethyl sulfoxide 50 mL (moisture content is 0% of the raw material) .08 weight times). It was immersed in an oil bath set at 120 ° C. with stirring and held for 5 hours. After cooling, the amberlist was filtered.

  The obtained filtrate was analyzed by high performance liquid chromatography, and the yield was calculated from the calibration curve of the standard substance. As a result, the yield of 5-hydroxymethylfurfural was 87 mol%.

  15 g of this filtrate (raw material, 5-hydroxymethylfurfural 0.77 g; 6 mmol) was weighed into a 25 mL flask equipped with a condenser and an oxygen balloon with a three-way cock. Further, palladium acetate (0.069 g; 0.3 mmol) and sodium hydrogen carbonate (1.03 g; 12 mmol) were weighed. While stirring, a pump was attached to the three-way cock, and after reducing the pressure, the cock was switched and oxygen was introduced from the oxygen balloon. This operation was repeated three times to replace the air in the flask with oxygen. It was immersed in an oil bath set at 80 ° C. and held for 30 hours.

  Thereafter, 2.4 mL of 5N sodium hydroxide aqueous solution (the amount of water added is 3.2 times the weight of the raw material, the amount of strong base added is 2 mol per mol of the raw material, and sodium hydroxide 0.48 g: 12 mmol) is added. For an additional 7 hours. The mixture was cooled to room temperature and diluted with 10 mL of water. Hydrochloric acid was added to this solution until the pH was 1 or less. The yield of precipitated crude 2,5-furandicarboxylic acid was 0.45 g, and the yield was 47 mol%. The yield from fructose was 41 mol%.

Example 3
A 25 mL flask equipped with a cooling tube and an oxygen balloon with a three-way cock was prepared. To this flask, raw materials 2-carboxy-5-formylfuran (0.7 g; 5 mmol), palladium acetate (0.056 g; 0.25 mmol), sodium hydrogen carbonate (0.84 g; 10 mmol), dimethyl 10 mL of a mixed solution of sulfoxide / water: 9/1 (the water content is 1.4 times the weight of the raw material) was weighed. While stirring, a pump was attached to the three-way cock, and after reducing the pressure, the cock was switched and oxygen was introduced from the oxygen balloon. This operation was repeated three times to replace the air in the flask with oxygen. It was immersed in an oil bath set at 80 ° C. and held for 34 hours.

  The obtained product was analyzed by liquid chromatography, and the yield was calculated from the calibration curve of the standard substance. As a result, the yield of 2,5-furandicarboxylic acid was 27 mol%.

Example 4
A 25 mL flask equipped with a cooling tube and an oxygen balloon with a three-way cock was prepared. Into this flask, raw benzyl alcohol (0.54 g; 5 mmol), palladium acetate (0.056 g; 0.25 mmol), sodium hydrogen carbonate (0.84 g; 10 mmol), dimethyl sulfoxide / water: 9 / 10 mL of the mixed solution of 1 (the water content was 1.9 times the weight of the raw material) was weighed. While stirring, a pump was attached to the three-way cock, and after reducing the pressure, the cock was switched and oxygen was introduced from the oxygen balloon. This operation was repeated three times to replace the air in the flask with oxygen. It was immersed in an oil bath set at 80 ° C. and held for 69 hours.

  The obtained product was analyzed by liquid chromatography, and the yield was calculated from the calibration curve of the standard substance. As a result, the yield of benzoic acid was 66 mol%, and the yield of benzaldehyde was 10 mol%.

Example 5
Under the same conditions as in Example 1, 2 mL of water was added instead of the strong base aqueous solution (the amount of water added was 3.2 times the weight of the raw material). It was immersed in an oil bath set at 80 ° C. and held for 25 hours.

  The obtained product was analyzed by liquid chromatography, and the yield was calculated from the calibration curve of the standard substance. As a result, the yield of 2,5-furandicarboxylic acid was 18 mol%.

Example 6
The reaction was carried out under the same conditions as in Example 1 without adding an aqueous strong base solution (the water content was 0.08 times the weight of the raw material). It was immersed in an oil bath set at 80 ° C. and held for 25 hours. As a result of analyzing the obtained product by liquid chromatography and calculating from the weight of the reaction solution and the concentration of 2,5-furandicarboxylic acid, the yield was 7 mol%.

Example 7
Under the same conditions as in Example 3, the reaction was carried out using dimethyl sulfoxide (water content 0.07 times by weight of the raw material) instead of the mixed solution of dimethyl sulfoxide / water: 9/1 as a solvent. It was immersed in an oil bath set at 80 ° C. and held for 66 hours. The obtained product was analyzed by liquid chromatography, and the yield was calculated from the calibration curve of the standard substance. As a result, the yield of 2,5-furandicarboxylic acid was 1.2 mol%.

  INDUSTRIAL APPLICABILITY Since the present invention can produce a carboxylic acid from an aromatic alcohol or an aromatic aldehyde in a high-boiling aprotic polar solvent having a boiling point of 100 ° C. or higher, it can be used in a method for producing an aromatic carboxylic acid. Can do.

Claims (8)

A method for producing a carboxylic acid, which is a raw material represented by the following general formula (1)

(Wherein Ar ₁ represents an aromatic ring which may have a substituent) or the following general formula (2)

(In the formula, Ar ₂ represents an aromatic ring which may have a substituent.) The aromatic aldehyde represented by the formula is oxidized via a catalyst in the presence of an aprotic polar solvent having a boiling point of 100 ° C. or higher. A method for producing a carboxylic acid, comprising a step and a step of adding 0.01 to 20 times by weight of water to the raw material. A method for producing a carboxylic acid, which is a raw material represented by the following general formula (1)

(Wherein Ar ₁ represents an aromatic ring which may have a substituent) or the following general formula (2)

(In the formula, Ar ₂ represents an aromatic ring which may have a substituent.) 0.01 wt.% Of the aromatic aldehyde represented by an aprotic polar solvent having a boiling point of 100 ° C. or higher and the raw material A method for producing a carboxylic acid, which comprises a step of oxidizing via a catalyst in the presence of water of not less than twice and not more than 20 weight times.   The method for producing a carboxylic acid according to claim 1 or 2, wherein the water is added when the aldehyde as a raw material is present.   The method for producing a carboxylic acid according to any one of claims 1 to 3, wherein the amount of water is 1 to 10 times the weight of the raw material.   The method for producing a carboxylic acid according to any one of claims 1 to 4, wherein the catalyst is a palladium compound.   The method for producing a carboxylic acid according to any one of claims 1 to 5, wherein the aprotic polar solvent is one or more selected from dimethyl sulfoxide, N-methylpyrrolidone and dimethylformamide.   The method for producing a carboxylic acid according to any one of claims 1 to 6, wherein the aromatic alcohol is 5-hydroxymethyl-2-furfural.   The method for producing a carboxylic acid according to claim 1, wherein the water contains 0.5 to 4 mol of a strong base with respect to 1 mol of the raw material.