JPS63277645A - Esterification of aromatic compound - Google Patents

Abstract

PURPOSE:To obtain the titled compound useful as an intermediate of a raw material for polymers by simple operation and readily in esterifying an aromatic compound containing a phenolic hydroxyl group with an organic acid, by carrying out the reaction in the presence of an acid while removing formed water by reaction distillation. CONSTITUTION:An aromatic compound containing a phenolic hydroxyl group is esterified with an organic acid (e.g. acetic acid, propionic acid, methacrylic acid, benzoic acid or naphthalenedicarboxylic acid) in the presence of an acid catalyst at 120-300 deg.C preferably in an inert gas atmosphere such as nitrogen. The reaction is carried out while removing formed water by using a distillation column having 10 or more plates to give the aimed compound. Sulfuric acid, p-toluenesulfuric acid or strongly acidic ion exchange resin is used as the acid catalyst and the amount of the catalyst used is 1-30wt.%, preferably 5-15wt.% based on the aromatic compound of the raw material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for esterifying an aromatic compound having a phenolic hydroxyl group with an organic acid.

Esterified products of phenolic hydroxyl groups of aromatic compounds are
It has important industrial uses as an intermediate for medicines, agricultural chemicals, and polymer raw materials.

(Prior art) Esterification of alcohols with organic acids progresses easily, but esterification of phenolic hydroxyl groups is difficult, so the reaction is performed using acid anhydrides or acid chlorides instead of organic acids. Methods for reacting with organic acids using various catalysts are known.

For example, Japanese Patent Publication No. 44-55 describes a method for esterifying an aromatic compound having a phenolic hydroxyl group by reacting it with 1-cyanovinyl acetate in the presence of an acid or an alkali. Furthermore, Japanese Patent Publication No. 55-10575 describes a method of heating carboxylic acid in the presence of a nitrile compound;
Method of heating a mixture consisting of IJ compound in the presence of sulfuric acid or aromatic sulfonic acid, JP-A-48-48433
No. 1, No. 1, pp. 10-12, 1999 describes a method in which a mixture of a carboxylic acid and a nitrile compound is heated in the presence of a compound selected from the group consisting of copper, zinc, iron, cobalt, and nickel. Further, JP-A-51-54525 describes a method in which an organic acid is reacted in the presence of activated clay.

(Problems to be Solved by the Invention) In order to produce acid anhydrides or acid chlorides from organic acids, as is well known, the reaction must be carried out under harsh conditions or a highly corrosive chlorinating agent must be used. There is a need.

The method using 1-cyanovinyl acetate as an esterification agent has a good yield, but there are problems such as the expensive raw materials for 1-cyanovinyl acetate synthesis and the danger of using hydrocyanic acid. be.

Japanese Patent Publication No. 55-10575 using a nitrile compound,
JP-A-48-36131 and JP-A-48-4843
The yield of esters in No. 3 was 26 to 64%, which is unsatisfactory, and the purification operation is complicated because an amide compound is produced from a nitrile compound. The method of JP-A-51-54525 in which the reaction is carried out in the presence of activated clay also has a low yield of esters and requires a long reaction time.

As described above, problems with the conventional method include the use of an expensive esterifying agent and the addition of a third substance, which requires complicated steps such as separation operations, resulting in a low yield.

(Means for Solving the Problems) As a result of extensive research into methods for esterifying the phenolic hydroxyl groups of aromatic compounds that have the above-mentioned problems, the inventors have developed a method for esterifying the phenolic hydroxyl groups of aromatic compounds using an organic acid as an esterifying agent. The present inventors have discovered that surprisingly high yields can be achieved in a short period of time by allowing the reaction to occur in the presence of a catalyst while removing produced water by reactive distillation, leading to the present invention.

That is, the present invention provides an ester of an aromatic compound, which is characterized in that when an aromatic compound having a phenolic hydroxyl group is esterified with an organic acid, the reaction is carried out while removing produced water by reactive distillation in the presence of an acid catalyst. It is a method of conversion.

The aromatic compound having a phenolic hydroxyl group of the present invention is an aromatic compound whose nucleus is substituted with a hydroxyl group. These aromatic compounds include not only aromatic hydrocarbons and their substituted compounds such as benzene, naphthalene, anthracene, phenanthrene, and biphenyl, but also pyridine, thiophene, pyrrole, and furan, which have properties that are generally referred to as aromatic groups. It includes aromatic ring compounds in a broad sense and their substituted compounds. The substituents of this compound are:
These are substituents that do not react with organic acids, such as alkyl groups, halogen groups, nitro groups, and alkoxy groups, and there is no limit to the number of these substituents. Further, the number of phenolic hydroxyl groups is not particularly limited either.

Therefore, the aromatic compounds having a phenolic hydroxyl group targeted in the present invention include, for example, phenol,
Phenols such as catechol, hydroquinone, varamethoxyphenol, valacresol, varanitrophenol, parachlorophenol, α-naphthol, β-
naphthols such as naphthol and substituted derivatives thereof;
Examples include phenylphenols such as phenylphenol and substituted derivatives thereof, and nitrogen-containing heteronuclear substituted alcohols such as 4-hydroxypyridine and 8-hydroxyquinoline.

The organic acids used in the present invention are aliphatic, alicyclic, and aromatic carboxylic acids having 2 to 18 carbon atoms, such as acetic acid, propionic acid, butyric acid, caproic acid, acrylic acid, methacrylic acid, and adipine. acids, maleic acid, fumaric acid,
Examples include cyclohexanecarboxylic acid, benzoic acid, tolylic acid, and naphthalenedicarboxylic acid.

The amount of these organic acids used is 10 to 100 mol, preferably 20 to 50 mol, per mol of the aromatic compound having a phenolic hydroxyl group.

In the method of the present invention, the reaction does not proceed at all in the absence of an acid catalyst. Examples of acid catalysts include mineral acids such as sulfuric acid and hydrochloric acid, organic sulfonic acids such as p-toluenesulfonic acid and methanesulfonic acid, and strong acidic ion exchange resins such as Amberlyte 200C and Amberlye IR-120B (both products). (namely, made by organo side). Sulfuric acid is particularly effective.

The amount of acid catalyst used is 1 to 30%, preferably 5 to 1% by weight relative to the aromatic compound having a phenolic hydroxyl group.
It is 5%.

The reaction temperature depends on the type of aromatic compound having a phenolic hydroxyl group, but is generally 120 to 300°C. If the temperature is too low, the reaction rate is slow, and if the temperature is too high, side reactions are likely to occur. The reaction temperature is also limited by the corrosion resistance of the equipment.

The reaction time varies depending on the reaction temperature, but in the above temperature range, a reaction time of 1 to 10 hours is usually required. There is no particular restriction on the pressure, and the reaction is generally carried out under normal pressure or increased pressure.

The method for removing the produced water is preferably a reactive distillation method using a distillation column having 10 or more stages. There is a method of separating the produced water pure, but there is also a method of separating it as a mixture with an organic acid, or a method of distilling the azeotrope by adding a third substance that forms an azeotrope with water, such as benzene or toluene, as a solvent. It can also be separated in a column.

Since the ester of an aromatic compound having a phenolic hydroxyl group may be oxidized by oxygen in the air and turn yellowish brown, it is preferable to carry out the reaction under an inert gas atmosphere such as nitrogen.

After the reaction is completed, separation and purification of the ester from the mixture is carried out by common methods such as distillation, extraction, or recrystallization.

(Effects) In the ester reaction between an organic acid and an aromatic compound having a phenolic hydroxyl group, the equilibrium is extremely biased towards the starting system, so it has been considered impossible to carry out the reaction efficiently using general esterification methods.

The present invention does not use expensive esterifying agents such as acid anhydrides, acid chlorides, or 1-cyanovinyl acetate, and does not require complicated separation operations due to the addition of third substances such as nitrile compounds. Not necessary.

The present invention has discovered a method that allows the ester reaction of an organic acid and an aromatic compound having many types of phenolic hydroxyl groups, which has been considered difficult in the past, to be easily obtained in high yield through simple operations. , and its industrial significance is great.

(Example) Next, the present invention will be explained in more detail with reference to Examples. Of course, the present invention is not limited to these examples.

Example 1 20 g (0,213 mol) of phenol and 500 g (0,213 mol) of phenol and 500 g (
8,333 mol) and 1 g of sulfuric acid were charged, and the temperature was raised. When the internal temperature reached 120°C, an acetic acid/water mixture began to be distilled out from the top of the Vigreux type fractionation column. The reaction rate was adjusted so that the amount of the acetic acid/water mixture distilled out was 30 g/hr, and the reaction was continued for 6 hours. After recovering acetic acid by distilling the reaction mixture under reduced pressure, 28.2 g of clear colorless phenylacetate was obtained as a fraction with a boiling point of 83° C. in 11 g of 13 mm, and the yield was 97%.

Example 2 24 g (0.2 mol) of p-cresol, 600 g of acetic acid
(10 moles) and 1.2 g of sulfuric acid were esterified in a reactive distillation vessel equipped with a column made of 5O3-316 whose inner volume was coated with Teflon. The reaction conditions were a pressure of 1.7 kg/cm 2 G and a temperature of 154° C., and water-containing acetic acid was extracted from the top of the distillation column at a rate of 60 to 70 g/hr, and the reaction was carried out for 2 hours. After recovering unreacted acetic acid from this reaction solution, 31.1 g of p-cresyl acetate was obtained by distillation under reduced pressure.
(0.192 mol) was obtained, and the yield was 96%.

Example 3 Using 33.6 g (0.2 mol) of β-naphthol as an aromatic compound having a phenolic hydroxyl group, a reaction was carried out under the same conditions as in Example 2 for 4 hours. After recovering unreacted acetic acid from the reaction solution, β-naphthyl acetate 3 was obtained by distillation under reduced pressure.
8.9 g (0.185 mol) was obtained, yield 92.
It was 6%.

Example 4 A reaction was carried out for 2 hours under the same conditions as in Example 2 except that 600 g (8.11 moles) of propionic acid was used as the organic acid and the reaction temperature was 173°C. After recovering unreacted propionic acid from the reaction solution, 33.1 g of P-talesylpropionate was obtained by vacuum distillation, with a yield of 94%.

Example 5 Using the same equipment as in Example 2, 18°8 g of phenol
(0.2 mol), 500 g of benzoic acid (4.1 mol),
200 g of benzene, 2.8 g of p-)luenesulfonic acid
At a pressure of 3 kg/cm2G and a reaction temperature of 140°C, a benzene/water azeotrope of 50 to 6
The reaction was carried out for 3 hours while withdrawing at a rate of 0 g/hr.

After recovering benzene from the reaction solution, 35.3 g (0,178 mol) of phenyl benzoate was obtained by distillation under reduced pressure. The yield was 89%.

Comparative Example 1 A reaction was carried out under exactly the same conditions as in Example 1, except that a flask without a Vigreux type fractionator was used and the acetic acid-water mixture was not extracted. As a result, the yield was 17%.

Comparative Example 2 A reaction was carried out under exactly the same conditions as in Example 2, except that sulfuric acid was not added. As a result, no p-cresyl acetate was produced.

Claims (1)

[Claims] A method for esterifying an aromatic compound, which is characterized in that when an aromatic compound having a phenolic hydroxyl group is esterified with an organic acid, the reaction is carried out while removing produced water by reactive distillation in the presence of an acid catalyst.