JPS6153275A - Production of acylfuran compound - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as a raw material for producing an alpha-alkylfurfurylamine, etc. in high yield, by reacting a furan compound with an acid anhydride by the use of an organic sulfonic acid having function of both acylating catalyst and esterifying catalyst. CONSTITUTION:1mol furan compound shown by the formula I (R1 is H, CH3, or C2H5) is acylated with 1.0-1.8mol acid anhydride shown by the formula II (R2 is CH3, or C2H5) in the presence of 0.02-0.2mol organic sulfonic acid preferably p-toluenesulfonic acid, etc. optionally by the use of a solvent, an alcohol is added to the prepared reaction mixture, and a carboxylic acid prepared as a by- product is esterified and removed, to give the aimed compound shown by the formula III. EFFECT:A hydrogen halide is not evolved even if an organic sulfonic acid is decomposed, corrosion of metal is not so important problem, a specific material is not required as a material of reactor, a by-product carboxylic acid is recovered in the form of ester, can be used directly as an extracting solvent and the aimed compound is easily purified.

Description

[Detailed description of the invention] [Industrial application fields] The present invention relates to a method for producing 2-acylfuran compounds.

[Prior Art] Acylfuran compounds have traditionally been used as α-alkylfurfurylamine or α-
It is used as a raw material for producing alkylfurfuryl alcohol, etc.

Useful acylfuran compounds such as those mentioned above, such as 2
-Acetylfuran is produced by reacting furan, a furan compound, with acetic anhydride using orthophosphoric acid as a catalyst.

However, when 2-acetylfuran is produced by this method, it is not possible to obtain 2-acetylfuran in a satisfactory yield unless acetic anhydride is used at least twice the mole of furan.

Therefore, a large amount of unreacted acetic anhydride remains, which must be neutralized with a large amount of a basic substance to form a salt and then removed, making the manufacturing process complicated.

Furthermore, since the excess acetic anhydride cannot be reused, there are disadvantages such as an increase in the manufacturing cost of the target product.

In order to solve this problem, a method has been proposed in which 2-acetylfuran is obtained in a relatively high yield by using boron trifluoride acetate as a catalyst and reacting acetic anhydride in a small excess with respect to furan. However, this method also has problems, such as, for example, when a stainless steel reactor is used, the equipment is subject to severe corrosion, and furthermore, it is difficult to treat wastewater containing the above-mentioned catalysts.

[Problems to be Solved by the Invention] The present invention solves problems such as an increase in production costs due to the use of a large excess of acetic anhydride produced when producing 2-acetylfuran as described above, and a large amount of unreacted material remaining. Solve problems such as the complicated treatment of acetic anhydride, corrosion of equipment caused by boron trifluoride when improved methods are adopted, and problems such as difficulty in treating wastewater containing the catalyst. It was done in order to

[Means for Solving the Problems] The present invention provides general formula (I): (wherein R1 is a hydrogen atom, a methyl group, or an ethyl group)
A furan compound represented by the general formula (I): (R2Co)2G' (I[)(
General formula HID produced by reacting an acid anhydride represented by (wherein, R2 is a methyl group or an ethyl group) in the presence of an organic sulfonic acid: (wherein, R1 and R2 are the same as above)
2- characterized in that alcohol is added to a reaction solution containing a 2-acylfuran compound represented by and a by-product carboxylic acid to esterify and remove the by-product carboxylic acid.
This invention relates to a method for producing acylfuran compounds.

[Example] The furan compound used in the present invention is a compound represented by the general formula (I): (wherein R1 is a hydrogen atom, a methyl group, or an ethyl group), and specifically, furan, 2 -Methylfuran, 2-ethylfuran, etc.

The acid anhydride used in the present invention has the general formula (■)=(12CO
)20 (I) (in the formula, R2 is a methyl group or an ethyl group), and specific examples include acetic anhydride and propionic anhydride.

It is preferable to use acid anhydrides produced from the same carboxylic acid as described above because the acyl group introduced into the furan compound is determined, but it is preferable that the acyl group introduced into the furan compound may be different. Alternatively, mixed acid anhydrides may be used which give different carboxylic acids upon hydrolysis.

Examples of the organic sulfonic acid used in the present invention include p-
Examples include toluenesulfonic acid, methanesulfonic acid, and phenylsulfonic acid.

These organic sulfonic acids may be used alone or in combination of two or more kinds. Among these, p-toluenesulfonic acid and methanesulfonic acid have good catalytic activity,
Furthermore, it is preferable because it is relatively inexpensive and can be easily used as an industrial raw material.

Next, the ratio of raw materials used and the manufacturing method for synthesizing the 2-acylfuran compound represented by the general formula (2) will be explained.

The amount of the acid anhydride represented by the general formula (1) is 1.0 to 1.0 to 1.0 mol per 1 mole of the furan compound represented by the general formula (I).
8 mol, preferably 1.1-1.5 mol, organic sulfonic acid 0.02-0.2 mol, preferably 0.05-0.
1 mole is used.゛When the amount of the acid anhydride represented by the general formula (I [l) used is less than 1.0 mol, the amount of unreacted furan compound represented by the general formula (1) increases, and the reaction yield decreases. On the other hand, the amount used is 1.8 mol.

Even if the amount exceeds 1, the yield will hardly change, and it will only act as a solvent, making it difficult to produce the desired product later.

From the viewpoint of reaction yield, the preferred amount of acid anhydride to be used is 1
．． In the range of 1 to 1.5 moles, for example about 1.2 to 1.3 moles when furan and acetic anhydride are used.

If the amount of the organic sulfonic acid used is less than 0.02 mol, the reaction yield will be significantly reduced, and even if it is used in excess of 0.2 mol, the yield will hardly change, and instead the furan will be turned into a resin. This may cause a decrease in the yield of the target product.

Usually, the furan compound represented by general formula (11) or the acid anhydride represented by general formula (1) acts as a solvent, so there is no need to use a solvent, but if necessary, 100 parts of a mixture of these A solvent such as ethyl ether, benzene, toluene, etc. may be used in an amount of about 10 to 200 parts by weight (the same applies hereinafter).

A furan compound represented by the general formula (1), a furan compound represented by the general formula (1)
Add a predetermined amount of the acid anhydride, hydrate, or organic sulfonic acid represented by 1 and a solvent if necessary, and heat the mixture to 0 to 120°C, preferably 10 to 120°C.
By reacting at 100° C. for 1 to 8 hours, preferably 2 to 4 hours, a 2-acylfuran compound represented by general formula 1 is synthesized, and a carboxylic acid is produced as a by-product.

If the reaction temperature is less than 0°C, the reaction rate will decrease, which is undesirable as the reaction time will be delayed or the reaction yield will decrease. This is not preferable because the compound may be scattered out of the reaction system or the furan-based compound may be converted into a resin.

Further, the pressure during the reaction is usually carried out under atmospheric pressure, but it can also be carried out under an increased pressure of several to 10 atmospheres in consideration of the boiling point of the reactants.

A reaction solution containing the synthesized 2-acylfuran compound is charged with 1 to 2 times the molar amount of ethanol, preferably 1.1 to 1.3 times the molar amount of the acid anhydride, and heated at air temperature to The reaction is carried out at about 50° C. for about 0.5 to 2 hours to esterify the by-produced carboxylic acid and residual acid anhydride.

The alcohol used for esterification must act as an extraction solvent for the target product, and the ester obtained from the alcohol and the by-product carboxylic acid or residual acid anhydride is transferred to the aqueous system during alkaline washing as described below. Examples of substances that satisfy these conditions include ethanol, propyl alcohol, butanol, and preferably ethanol.

In the esterification reaction, the organic sulfonic acid used as the acylation catalyst also acts effectively as a catalyst for the esterification reaction, and by simply reacting under the above reaction conditions, 70% of the carboxylic acid and residual acid anhydride produced as by-products are removed. ~90% can be esterified.

After the esterification reaction is completed, the catalyst organic sulfonic acid and residual carboxylic acid are neutralized using, for example, an aqueous solution of a basic substance such as soda carbonate, caustic soda, potassium carbonate, or caustic potassium. Thereafter, the desired product is extracted using an extraction solvent such as ethyl acetate, and the desired 2-acylfuran compound is isolated by a method such as distillation. Note that the ester produced by the reaction of a by-product carboxylic acid or the like with alcohol can be used as it is as an extraction solvent.

After synthesizing a 2-acylfuran compound, instead of esterifying it as in the production method of the present invention, for example, immediately after the reaction, it is neutralized with an aqueous sodium carbonate solution and the desired product is extracted with a solvent such as ethyl acetate. Therefore, compared to the case of purifying 2-acylfuran compounds, when esterified as in the production method of the present invention, the produced ester acts as an extraction solvent, and the world of carboxylic acids to be removed by neutralization is released. For example, when the target product 2-acetylfuran is produced in 1 part (heavy Q part, hereinafter the same) by a conventional method, the amount of 2-acetylfuran is 1.6.
3 parts or more of sodium acetate/water temperature is produced as a by-product, causing problems such as wastewater treatment. On the other hand, according to the production method of the present invention, the carboxylic acid salt is reduced to about 115 or less compared to the conventional technique, and the reaction vessel for neutralization is also small in capacity. Furthermore, although the desired product, the 2-acylfuran compound, is generally slightly soluble in water, the amount of the above-mentioned basic aqueous solution used can be reduced, and as a result, the amount of extraction solvent used can also be reduced.

Next, the manufacturing method of the present invention will be explained based on Examples.

Example 1 500 g of furan (
After charging 7,35 mol and 600 g (5,88 mol) of acetic anhydride, the reaction system was cooled and p-toluenesulfonic acid monohydrate 1409 (
A solution consisting of 0.13 mol) and acetic anhydride 3769 (3.68 mol) was added dropwise with stirring over a period of 30 minutes. After that, the temperature inside the system rose due to the heat of reaction and reached a maximum temperature of 90°C, but after keeping it at the same temperature for 30 minutes, stirring was continued for 2.5 hours while it was left to cool loosely. was synthesized.

After the acetylation reaction was completed, 542 g of ethanol was added to the reaction solution.
was added and reacted for 1 hour at 30° C. with stirring to esterify the remaining acetic anhydride and by-product acetic acid.

After that, a solution consisting of 166 g of soda carbonate and soo g of water was added to neutralize the remaining acetic acid and p-toluenesulfonic acid, and 500 g of ethyl acetate was added to the mixed solution to obtain 2-
After extracting acetylfuran, add 500d of water and 2%
Salt solution 50htf! Washed with. Thereafter, the solvent was removed to obtain 787 g of crude 2-acetylfuran.

The obtained crude 2-acetylfuran is purified by distillation.b
D72-75℃ (19mn+Hg)), GCIQ degree 9
9.7% of 2-acederfuran G38CJ (yield 85.
1%).

Example 2 Volume f! with stirrer, cooling tube, thermometer and dropping funnel. i Franc 34.09 for a 300d 4 flask
(0,5 mol), propionic anhydride 84,6 g (0
, 65 mol) and p-toluenesulfonic acid monohydrate (9.5 J (0.05 mol)), Example 1
2-propionylfuran was synthesized in the same manner as above.

After the propionylation reaction was completed, 36.97 ml of ethanol was added and esterification was carried out in the same manner as in Example 1.

After that, a solution consisting of 139 g of soda carbonate and 30 g of water was added to neutralize the mixture, and then 509 g of ethyl acetate was added to 2-
Propionylfuran was extracted.

After that, it was washed with 50 g of water, followed by 50 g of 2% saline solution, the solvent was removed, and crude 2-propionylfuran 80.1
I got g.

The obtained crude 2-propionylfuran was purified by distillation to obtain 52.4 g of 2-propionylfuran (yield: 84.5%) with a GC purity of 99.6%.

Example 3 2-acetyl-5-
Methylfuran was obtained (yield 85.7%).

Example 4 2-acetylfuran was obtained in the same manner as in Example 1 except that the p-toluenesulfonic acid monohydrate used in Example 1 was replaced with methanesulfonic acid equivalent mole, yield of 86.1. %)
.

[Effects of the Invention] The modified sulfonic acid used in the present invention does not generate hydrogen halide even when decomposed, has few problems of metal corrosion, and does not require the use of special materials for the reaction equipment.

In addition, acidic substances generally have the property of turning furan compounds into resins, but the organic sulfonic acids used in the present invention have high catalytic activity during the acylation reaction, and under the present reaction conditions unexpectedly, resin by-products are produced. Acylfuran compounds can be produced in high yields.

Furthermore, when a furan compound is subjected to an acylation reaction, the carboxylic acid produced as a by-product was conventionally disposed of as a carboxylate salt along with wastewater, but in the present invention, the organic sulfonic acid that is the acylation catalyst is esterified as is. By functioning as a catalyst, most of the by-product carboxylic acids are recovered in the form of esters, and the esters can be used as they are as extraction solvents, which are essential for isolating and purifying the desired product from the reaction mixture. Therefore, purification becomes easy.

Claims (1)

[Claims] 1. General formula (I): ▲There are mathematical formulas, chemical formulas, tables, etc.▼(I) (In the formula, R_1 is a hydrogen atom, a methyl group, or an ethyl group) A furan compound represented by , General formula (II): (R_2CO)_2O(II) (In the formula, R_2 is a methyl group or an ethyl group) A general formula produced by reacting an acid anhydride represented by the following in the presence of an organic sulfonic acid: (III): ▲There are mathematical formulas, chemical formulas, tables, etc.▼(III) (In the formula, R_1 and R_2 are the same as above) 2
- A method for producing a 2-acylfuran compound, which comprises adding alcohol to a reaction solution containing an acylfuran compound and a by-product carboxylic acid to esterify and remove the by-product carboxylic acid.