JPH0530821B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for producing an acetyl compound, that is, an aromatic acetate, by acetylating a phenol compound using vinyl acetate as an acetylating agent. This method is simple, rapid, performs acetylation at low temperatures, and has the advantage of eliminating the need for corrosion-resistant reaction equipment over conventional methods that use acetic anhydride or acetyl chloride and produce acidic reaction products. Conventional technology Until now, the acetylation reaction using vinyl acetate has been reported in the literature on the acetylation reaction of starches (US Patent No.
No. 3022189, No. 3081296, No. 3318868, No. 4038482, No. 2731496), but there is no description of the acetyl reaction of phenolic compounds having this acidic hydroxyl group, and there is no description of this excellent effect. Application examples have not yet been published in the literature. Problems to be Solved by the Invention The difference between phenolic compounds and general aliphatic alcohol compounds is that both contain hydroxy groups in the same way, but the former are ionized and become acidic, so It is known that the acetylation reaction of hydroxy groups is more difficult than that of aliphatic alcohol compounds. They require higher reaction temperatures and stronger acidic catalysts, which require harsher reactor material requirements and result in more complex product compositions. The acetylating agents that are commonly used in industry are mainly acetic anhydride and acetyl chloride, both of which are sensitive to moisture, and the latter is extremely sensitive to moisture, so hydrolysis must be avoided. The former is 1 after the reaction
produces moles of acetic acid, the latter produces hydrogen chloride,
The former must be separated by distillation. Therefore, the equipment costs are high, and the latter must be very careful about the severe corrosion and pollution of the equipment due to moisture. Means for Solving the Problems As a result of studies to overcome the conventional drawbacks, the present inventors neutralized a phenol compound with an alkali to form a salt, and acetylated it using vinyl acetate at a temperature of 160°C or less. The present invention was completed by discovering a method for efficiently producing acetyl compounds through reaction. Due to the use of vinyl acetate in the present invention, the by-product after the reaction is non-corrosive and becomes volatile acetaldehyde. Acetaldehyde is easily separated from the main product and can be recovered and used in the synthesis of many organic compounds. During the reaction, in order to suppress the acidity of this phenolic compound, the phenolic compound is first neutralized with an alkali and converted into a hydroxy salt to increase its nucleophilicity, and further to increase the reaction ability of the neutral vinyl acetate ester. As a result, most of the phenolic compounds can be efficiently converted to the corresponding acetyl compounds. In the present invention, a phenol compound is first neutralized with an alkali in carrying out an acetylation reaction. As the phenol compound of the present invention, in addition to phenol, for example, phenol having a chloro group, a hydroxy group, or a carboxy group can be used. Alkali that can be used include:
Mention may be made of basic metal salts of group of the periodic table, ie, hydroxides or carbonates of lithium, sodium, potassium, rubidium, and organic amine compounds or ammonia. The molar ratio of alkali and phenolic compounds used for neutralization is
It is preferably 0.5 to 2.5. The amount of vinyl acetate used in the acetylation reaction is
The molar ratio to the phenolic compound can be selected in the range of 1:10, preferably 1:5. The acetylation reaction is preferably carried out in a solvent, and for example, water, dimethyl sulfoxide (DMSO), dimethylformamide, dimethylacetamide, etc. can be used. In carrying out the reaction, the weight ratio of the solvent to the phenolic compound is preferably 2 to 8. To carry out the acetylation reaction, the reaction temperature is as described above.
The temperature is 160°C or lower and 0°C or higher, and in order to carry out the reaction more efficiently, the temperature is 10°C to 110°C, more preferably,
The reaction temperature is 20°C to 70°C. The reaction is also desirably carried out under pressure, with a pressure of 1 to 10 atm, more preferably 1 to 3 atm being selected. The acetyl compound produced as above is
By evaporating the by-produced acetaldehyde, and separating it from solvents such as water by solid-liquid separation,
It can be purified and obtained by recrystallization. For example, by arranging a device as shown in Figure 1,
It is possible to carry out everything from reaction to acquisition. In this apparatus, the phenol compound and the alkali form a salt in the neutralization tank N1, and the salt is sent to the reaction tank R1, where it is mixed with vinyl acetate and subjected to an acetylation reaction. Acetaldehyde, which is produced as a by-product, is recovered via heat exchangers E1 and E2.
On the other hand, the obtained crude acetyl compound is sent to a neutralization tank (precipitation tank) N2, the alkali is removed with a sanator, and after solid-liquid separation is performed in a centrifuge S1, crystallization tank C1 is used for recrystallization. The crystals can be separated in a centrifuge S2 to obtain a purified acetyl compound. Examples Hereinafter, the present invention will be explained in more detail with reference to Examples. Incidentally, in Example 1, the reaction rate and selectivity of vinyl acetate and acetic anhydride as acetylating agents were compared. In addition, Examples 2, 3, 4, and 5 show the influence of the reaction on the amount of vinyl acetate used, the amount of alkali used, and the amount of water used, respectively. Furthermore, Example 6 shows the results when water and other solvents were used, and Example 7 shows the results when phenol and other phenolic compounds were used. Example 1 Vinyl acetate and acetic anhydride were used separately as acetylating agents, and the acetylation reaction of paraoxybenzoic acid was observed. The reaction conditions are as follows. Vinyl acetate: 100g paraoxybenzoic acid and 81g
of caustic potash is added to 400 ml of water with stirring,
After uniformly dissolving, 80 ml of vinyl acetate was added and reacted for 22 hours. Acetic anhydride: 120 ml of acetic acid and 120 ml of acetic anhydride were added to 100 g of paraoxybenzoic acid, and the mixture was reacted for 2 hours with stirring at 125-130°C. Table 1 shows the reaction results of these two types of acetylating agents.

[Table] Example 2 100 g of paraoxybenzoic acid and 81 g of caustic potassium were dissolved in 400 ml of water, vinyl acetate was added, and the mixture was reacted for 2 hours. Table 2 shows the amount of vinyl acetate used and the influence of the reaction.

[Table] Example 3 Add 100g of paraoxybenzoic acid and caustic potassium in the molar ratio shown in Table 3, dissolve in 400ml of water, and then add 200ml of
of vinyl acetate was added and reacted for 2 hours. Table 3 shows the amount of alkali used and the influence of the reaction.

[Table] Example 4 The same procedure as in Example 2 was conducted using paraoxybenzoic acid and various alkalis. Table 4 shows the type of alkali and its influence on the reaction.

[Table] Example 5 100 g of paraoxybenzoic acid and 81 g of caustic potassium were added to water in the amount shown in Table 5 and dissolved by stirring, and then 200 ml of vinyl acetate was added and reacted for 2 hours.
Table 5 shows the influence of water amount and reaction.

[Table] Example 6 Dissolve 100g of paraoxybenzoic acid and 120ml of triethanolamine in various solvents,
Reacted with 328ml vinyl acetate. Table 6 shows the influence of acetylation reactions on various solvents.

[Table] Example 7 Various phenol compounds (1 mol) and the amount of caustic potassium shown in Table 7 were added, 4 times the amount of water as the amount of caustic potash was added to dissolve it, 1.2 mol of vinyl acetate was added thereto, and the mixture was reacted at room temperature. . Table 7 shows the results of the acetylation reaction of each phenol compound.

[Table] Effects of the Invention The first effect of the present invention is that the acetylation reaction of phenolic compounds can proceed at low temperatures. A second advantage of the present invention is that the acetylation reaction is simple, the reaction products can be separated under the reaction conditions, and unnecessary acidic by-products are not produced as in conventional methods. The third advantage is that the equipment does not require expensive materials due to the low temperature reaction conditions and non-acidic reaction products. Such effects are very advantageous conditions for industrial implementation.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing an example of a manufacturing method for carrying out the method of the present invention. E1, E2... Heat exchanger, R1... Reaction tank, N1... Neutralization tank, S1, S2... Centrifugal separator, C... Crystal tank.

Claims (1)

[Scope of Claims] 1. A method for producing an acetyl compound, which comprises neutralizing a phenol compound with an alkali to form a salt, and subjecting it to an acetylation reaction using vinyl acetate at a temperature of 160° C. or lower. 2. The method according to claim 1, wherein the acetylation reaction is carried out at 10°C to 110°C. 3. The method according to claim 1, wherein the acetylation reaction is carried out at 20°C to 70°C. 4. The method according to claim 1, wherein the acetylation reaction is carried out under 1 to 10 atmospheres. 5. The method according to claim 1, wherein the acetylation reaction is carried out under 1 to 3 atmospheres. 6. The method according to claim 1, wherein the molar ratio of vinyl acetate to phenolic compound used is 1:10. 7. The method according to claim 1, wherein the molar ratio of vinyl acetate to phenolic compound used is 1:5. 8. The method according to claim 1, wherein the alkali used is a basic metal salt of group of the periodic table, an organic amine compound or ammonia. 9 The alkali used is lithium, sodium,
2. The method according to claim 1, wherein the hydroxide or carbonate of potassium, rubidium or ammonia is used. 10. The method according to claim 1, wherein the molar ratio of the alkali and phenolic compound used for neutralization is 0.5 to 2.5. 11. The method according to claim 1, wherein the neutralization and acetylation reactions are carried out in a solvent. 12. The method according to claim 1, wherein the solvent is water, dimethylsulfoxide, dimethylformamide, or dimethylacetamide. 13. The method according to claim 11, wherein the weight ratio of the phenolic compound to the solvent is from 2 to 8. 14. The method according to claim 1, wherein the phenolic compound is phenol or a phenol having a chloro group, a hydroxy group, or a carboxy group. 15 Neutralize the phenolic compound with an alkali to form a salt, perform an acetylation reaction using vinyl acetate at a temperature below 160°C, evaporate and separate the by-produced acetaldehyde, and separate the acetyl compound as a product by solid-liquid separation. A method for obtaining an acetyl compound, characterized by separation, recrystallization, and purification.