JPS6029374B2 - Method for producing 5-alkoxy-4-hydroxyisophthalaldehyde - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for producing 5-alkoxy-4-hydroxyisophthalaldehyde (hereinafter simply referred to as isophthalaldehyde). It is known that when guaiacol is reacted with glyoxylic acid in a basic aqueous medium and the reaction product is oxidized, isophthalaldehyde is formed together with vanillin. The method for isolating isophthalaldehyde from the oxidation reaction solution obtained by this method is as follows: ○} After distilling the oxidation reaction solution, removing water and then vanillin, 0.1 side Hg (absolute pressure) A method in which isophthalaldehyde is removed by vacuum distillation at a temperature of 135 to 140 oo in a high vacuum, '2} The oxidation reaction solution is distilled, water is removed, vanillin is removed, and the distillation residue is removed. The solution is dissolved in an organic solvent, an aqueous solution of sodium bisulfite is added to the solution, and then sulfuric acid is added to the aqueous layer separated from the organic solvent layer under heating.
There is a method in which isophthalaldehyde is precipitated by cooling the water layer until no sulfur dioxide gas is produced, and then cooling the water layer. The above method {1-- requires distillation under high vacuum and is extremely difficult to implement industrially. The ratio of the amount of softaldehyde (hereinafter referred to as isolation rate) is about 20% [see Comparative Example '2]]. the above

[Method No. 21 has a considerably higher isolation rate than the method No. 11, but it is still about 50% [see Comparative Example [3]], and the operation is complicated, making it difficult to use as an industrial method. cannot be adopted. The present invention provides a method for producing isophthalaldehyde in which isophthalaldehyde can be easily isolated from an oxidation reaction solution and has a high isolation rate of isophthalaldehyde. That is, this invention provides an alkoxyhydroxybenzaldehyde (hereinafter simply referred to as benzaldehyde) represented by the formula or formula (in both formulas, R is an alkyl group having 1 to 3 carbon atoms) in a basic aqueous medium. 0～
The first reacted with glyoxylic acid at a temperature in the range of 50°C.
step, by adding a mineral acid to the reaction product mixture obtained in the first step to bring the pH value to 5 to 7, the mixture is brought into contact with an organic solvent, and the formula [1] or formula [0] in the mixture is A second step in which the indicated benzaldehyde is extracted and removed, a third step in which a chlorinated compound is added to the aqueous layer of the extraction residue obtained in the second effective step to make the aqueous layer basic and then oxidized, and an oxidation reaction This is a method for producing isophthalaldehyde, which includes a fourth step of adding a mineral acid to the liquid to adjust the pH value to 6.5 or less and precipitating isophthalaldehyde. Next, each step of this invention will be explained. [First step] In the first step, benzaldehyde is reacted with glyoxylic acid. Specific examples of benzaldehyde represented by formula [1] or formula [b] include 4-hydroxy-3-methoxybenzaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, 4-hydroxy-3-n-propoxybenzaldehyde, and 2-hydroxy-3-n-propoxybenzaldehyde. -methoxybenzaldehyde, 3-ethoxy-2-hydroxybenzaldehyde, and the like. Glyoxylic acid may be used as it is or in the form of its alkali metal salts, such as sodium glyoxylate and potassium glyoxylate. There are no particular restrictions on the amount of glyoxylic acid used, but
0.5 to 1.3 mol per mol of benzaldihyde is preferred. The reaction is carried out using basic water as a medium in which basic compounds such as sodium hydroxide, potassium hydroxide, and sodium carbonate are dissolved. The reaction does not substantially proceed in a neutral or acidic aqueous medium. There are no particular restrictions on the amount of water used, but it is usually 500 ml per mole of benzaldehyde.
~1000 screams. The reaction temperature is 0-50°C, preferably 10-4020°C. If the reaction temperature is lower than 000, the reaction rate will be low, which is not preferable;
If it is higher than 0 qo, glyoxylic acid is converted into oxalic acid and glylic acid by Cannizzaro reaction, which is not preferable. There is no particular limit to the reaction time, but it is usually 20 to 10 feeding times. The reaction produces a compound represented by the following formula or formula (in both formulas, R is an alkyl group having 1 to 3 carbon atoms). [Second Step] In the second step, unreacted benzaldehyde is extracted and removed from the reaction product mixture obtained in the first step. A key acid, for example hydrochloric acid, sulfuric acid, is added to the reaction mixture until a pH value of 5-7 is reached. Thereafter, this mixture is brought into contact with an organic solvent to extract and remove benzaldehyde from the mixture. p of the above mixture
If the H value is higher than 7, the extraction of benzaldehyde will be insufficient, and if the pH value of the mixture is lower than 5, the compound represented by formula [m] or formula [W] will also be extracted together with benzaldehyde, and the final The yield of isophthalaldehyde obtained is reduced. Ether, benzene, toluene, xylene, etc. are used as organic solvents for extraction. There are no particular restrictions on the extraction method, and known methods such as batch extraction and continuous extraction can be used. After extraction, unreacted benzaldehyde can be recovered by distilling the organic solvent layer. [Third Step] In the third step, isophthalaldehyde is produced by oxidizing the compound represented by formula [m] or formula [N] in the aqueous layer of the extraction residue obtained in the second step. A basic compound such as sodium hydroxide, potassium hydroxide, sodium carbonate is added to the aqueous layer to make it basic. Under acidic or neutral conditions, the reaction rate is too low to be practical.
As the oxidation method, a method of oxidizing the water layer by blowing oxygen gas or air into the water layer can be adopted. During oxidation, copper, manganese, cobalt, chromium, platinum,
Powders, oxides, hydroxides of iron, aluminum, silver, vanadium, nickel, etc. can also be used as catalysts. There are no particular restrictions on the oxidation temperature, but it is usually 80~
15,000°C, preferably 100-130°C. The oxidation reaction may be carried out under normal pressure or under increased pressure. There is no particular restriction on the oxidation reaction time, but it is usually 1 to 3 hours. When the above-mentioned catalyst is used in the oxidation reaction, the catalyst is removed from the reaction solution after the oxidation reaction and the resultant solution is subjected to the fourth step. [Fourth Step] In the fourth step, isophthalaldehyde is precipitated and isolated from the oxidation reaction solution obtained in the third factory. Mineral acid is added to the oxidation reaction solution until its pH value becomes 6.5 or less.
For example, add hydrochloric acid or sulfuric acid. If the oxidation reaction solution is left to stand after this, since softaldehyde is insoluble in water with a pH value of 6-5 or less, it will precipitate. The temperature of the oxidation reaction solution during standing is preferably 0 to 2500. The leaving time is usually 10 to 2 feeding hours. Highly purified isophthalaldehyde is obtained in powder form by separating the precipitate in a furnace and drying it under vacuum. Moreover, the isolation rate of isophthalaldehyde is 90% or more, as is clear from the results of the examples. According to the method of the present invention, a high isolation rate of isophthalaldehyde can be obtained by a simple operation compared to the method for producing isophthalaldehyde described in the above. Next, Examples and Comparative Examples will be shown. Isophthalaldehyde in the oxidation reaction solution was determined by gas chromatography. Example 1 7.60 hours of 2N sodium hydroxide aqueous solution, 7.60 hours of 2-hydroxy-3-methoxybenzaldehyde and 21.5 hours of 2% by weight aqueous solution of glyoxylic acid were added, and reaction was carried out at 40 degrees for 7 hours. I let it happen. Hydrochloric acid was added to the reaction mixture until its pH value was 6. Using a separating funnel, this aqueous solution and 50% of diethyl ether were vigorously immersed in a haze, and then the aqueous layer was discharged. The same operation as above was repeated twice for this aqueous layer. 1.02 kg of 2-hydroxy-3-methoxybenzaldehyde was recovered from the diethyl ether layer. Above water layer, 2N sodium hydroxide aqueous solution 65 and oxidized steel (b) 0.7
The mixture was charged into an autoclave, and while air was flowing through the reaction mixture at a pressure of 2 kg/flow (gauge pressure) and a flow rate of 0.1 kg/min, it was dumped onto a rock to react at 125 qo for 90 minutes, and then allowed to cool. did. Thereafter, oxidized steel (0) was separated from the oxidation reaction mixture in a furnace to obtain an oxidation reaction liquid. The oxidation reaction solution was divided into two equal parts, and la normal hydrochloric acid was added to each part until the multiplication value reached 6. It was confirmed by gas chromatography analysis that one of the oxidation reaction liquids contained 3.82 g of 4-hydroxy-5-methoxysophthalaldehyde. When the other oxidation reaction solution was left at 7° C. for 1 hour, a precipitate was deposited. This precipitate was separated in a furnace and then vacuum dried to produce a yellowish white powder 3.
．． I got 51 evenings. The melting point of this powder is 120.5-121
．． 000, and its infrared absorption spectrum matched that of 4-hydroxy-5-methoxysophthalaldehyde. The yield of 4-hydroxy-5-methoxyisophthaladehyde based on the charged 2-hydroxy-3-methoxybenzaldehyde was 78%, and the yield was 92%. Example 2 2-hydroxy-3-methoxybenzaldehyde 4-hydroxy-3-methoxybenzaldehyde7.
The same procedure as in Example 1 was carried out except that 60 days were used. After the second step, 2.35 g of 4-hydroxy-3-methoxybenzaldihyde was recovered from the jet ether layer. The oxidation reaction solution was divided into two equal parts, and la normal hydrochloric acid was added to each part until the pH value reached 6. It was confirmed by gas chromatography analysis that one of the oxidation reaction liquids contained 2.98 g of 4-hydroxy-5-methoxyisophthalaldehyde. The other oxidation reaction solution was treated in the same manner as in Example 1, and powdered 4-hydroxy-5-methoxysophthalaldehyde having a melting point of 120.5 to 121.0 °C was prepared with a powder of 2.6%.
I got 9 nights. The yield of 4-hydroxy-5-methoxy-5-methoxysophthalaldehyde based on the charged 4-hydroxy-3-methoxybenzaldehyde was 60%.
The isolation rate was 90%. Comparative Example 3 To 90% of a normal aqueous sodium hydroxide solution, 42.7% of a 2% by weight aqueous solution of glyoxylic acid and 18.6% of 2-methoxyphenol were added, and the mixture was reacted at 2500 °C for 2 hours. After this, the reaction product mixture was added with l
aNormal hydrochloric acid was added. Then, 2-
Methoxyphenol was extracted and recovered. 6.30 tons of 2-methoxyphenol were recovered. Aqueous layer of citron residue, 210 parts of 2N aqueous sodium hydroxide solution, and 2.8 parts of copper oxide (2) were charged into an autoclave, and the flow rate was 0.1 parts per minute at a pressure of 2 kg/minute (gauge pressure). While air was flowing through the reaction mixture at
After reacting at 5 qo for 90 minutes, the mixture was cooled. Oxidized steel (0) was separated from the oxidation reaction mixture to obtain an oxidation reaction liquid. The oxidation reaction solution was divided into four equal parts, and la standard hydrochloric acid was added to each part until the pH value reached 6. Each oxidation reaction solution was subjected to the following treatment. '11
Gas chromatography analysis: The oxidation reaction solution was extracted three times with 100 units each of diethyl ether, and the diethyl ether layer separated from the aqueous layer was quantified using gas chromatography. , 4-hydroxy-3-methoxybenzaldehyde 3.09 and 2
-Hydroxy-3-methoxybenaldehyde 0.11
It was confirmed that the twilight was included. ■ Vacuum distillation: Distill the oxidation reaction solution at normal pressure to first remove water, then 1
Reduce the pressure to side Hg (absolute pressure) and reduce the tank liquid temperature to 95-1000.
0 and 2-hydroxy-3-methoxybenaldehyde 0
．． 3.06 ml of 4-hydroxy-3-methoxybenaldehyde was distilled off at a temperature of 119 to 12,400 yen. After this, the pressure was reduced to 0.1 Yanagi Hg (absolute pressure), and the tank liquid temperature was 1
35 to 4000, 0.11 ml of 4-hydroxyisophthalaldehyde was distilled off. After this, the temperature of the can liquid was raised, but no crab material was observed. The isolation rate of 4-hydroxy-5-methoxysophthalaldehyde was 19%. '3} Isolation method using sodium bisulfite; distilling the oxidation reaction solution to obtain water and 2-hydride. The xy-3-methoxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde were distilled off in the bottle.
Thereafter, the distillation residue was dissolved in 50 g of toluene, and to this solution was added 1 wt. The toluene layer and the aqueous layer were then separated, and 3 ml of sulfuric acid was added while heating the aqueous layer to 9,000 ℃. Sulfur dioxide gas was generated by the addition of sulfuric acid. After continuing to pray until the generation of sulfur dioxide gas ceased, the temperature was 4-
Hydroxy-5-methoxysophthalaldehyde was precipitated. Thereafter, 4-hydroxy-5-methoxyphthalaldehyde was separated in a furnace, and then vacuum dried to give a yellow powder of 0.2
I got 6 nights. The isolation rate of 4-hydroxy-5-methoxysophthalaldehyde was 46%. '4} Isolation method similar to the method of the present invention: The oxidation reaction solution was distilled to sequentially remove water, 2-hydroxy-3-methoxybenzaldehyde and 4-hydroxy-3-methoxybenzaldehyde. After this, add 3 parts of 2N aqueous sodium hydroxide solution to the distillation residue.
0' was added and heated to 900C to dissolve the distillation residual solution. Next, LAN hydrochloric acid was added to this solution until the pH value reached 5, and it was left at 7°C for 1 hour, but only a dark red oily substance remained at the bottom of the container, and no precipitation was observed. Ta.

Claims (1)

[Claims] 1 Represented by the formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or the formula ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In both formulas, R is an alkyl group having 1 to 3 carbon atoms) A first step in which alkoxyhydroxybenzaldehyde is reacted with glyoxylic acid in a chlorinated aqueous medium at a temperature ranging from 0 to 50°C, and a mineral acid is added to the reaction product mixture obtained in the first step to adjust the pH value. a second step of bringing the mixture of 5 to 7 into contact with an organic solvent to extract and remove the alkoxyhydroxybenzaldehyde represented by formula [I] or formula [II] in the mixture; and A third step of adding a basic compound to the aqueous layer of the extracted residue to make the aqueous layer basic and then oxidizing it, and adding a mineral acid to the oxidation reaction solution to make the pH value 6.5 or less, A method for producing 5-alkoxy-4-hydroxyisophthalaldehyde, which comprises a fourth step of precipitating alkoxy-4-hydroxyisophthalaldehyde.