JPH05194308A - Production of p-hydroxybenzoic acids - Google Patents

Abstract

PURPOSE:To easily produce p-hydroxybenzoic acids useful as intermediates for synthetic resins and various organic fine chemicals from an inexpensive raw material in high yield without using a solvent. CONSTITUTION:p-Hydroxybenzoic acids are easily produced in high yield without using particular catalyst by oxidizing 1-(4-hydroxyphenyl)-2-hydroxy-1-ethanones of formula (A to D are H, OH, 1-4C alkyl or alkoxy) with molecular oxygen in the presence of 0.1-10.0mol, preferably 1.0-4.0mol (based on 1mol of the compound of formula) of a basic substance (preferably water-soluble strong base such as sodium hydroxide, potassium hydroxide and tetramethylammonium hydroxide) e.g. at 0-150 deg.C preferably 25-100 deg.C. The compound of formula used as a raw material is easily synthesizable by the reaction of phenols with glyoxal in the presence of a basic or acidic substance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing para-hydroxybenzoic acids (hereinafter abbreviated as PHBA) useful as intermediates for producing synthetic resins and various organic fine chemicals.

[0002]

As a method for producing PHBA, the Kolbe-Schmitt reaction in which potassium phenoxide is reacted with carbon dioxide gas in the presence of potassium carbonate is well known, but it is a solid phase reaction, and a high temperature of 200 ° C. or higher is used for the reaction. Since it is necessary, there were various problems in manufacturing engineering.

[0003]

DISCLOSURE OF THE INVENTION As a result of intensive investigations aimed at solving such problems, the present inventors have found that phenols and glyoxal can be easily condensed by condensing them in the presence of a basic or acidic substance. Can be synthesized 1- (4-
It was found that PHBA can be easily synthesized in high yield by oxidizing (hydroxyphenyl) -2-hydroxy-1-ethanones (hereinafter abbreviated as PHET).

PHET represented by the following formula, which is a raw material of the present invention, can be easily synthesized by condensing phenols and glyoxal in the presence of a basic or acidic substance.

[0005]

[Chemical 1]

PHET is a compound useful for organic synthesis having a hydroxymethylcarbonyl group capable of having a keto-enol tautomeric structure in its side chain. The reaction is not well known, probably because there was no simple synthetic method until the development of. Regarding the oxidation reaction, PHB was slightly oxidized by oxidizing oxygen with molecular oxygen using oxygenase of a specific microorganism.
It is only known that A can be synthesized. (D.
J. Hopper et. al. , Biochem.
J. , 218 , 269, (1984), ibid. , 2
39 , 469, (1986))

Usually, the oxidation reaction of the hydroxymethylcarbonyl group on the side chain of the benzene ring gives a plurality of products, the proportion of which depends on the type of oxidizing agent used. For example α-
Taking the oxidation of hydroxyacetophenone as an example, when chromic acid or potassium permanganate is used as an oxidant, benzaldehyde (BZH) and benzoic acid (BA) are produced, and nitric acid oxidation produces BA and phenylglyoxylic acid (P
GA) and oxidation with molecular oxygen using a copper sulfate catalyst in an aqueous solution of sodium hydroxide gives BZH, BA, PG
It is known to produce a mixture of A, mandelic acid (MA). In recent years, the use of calcium hypochlorite as an oxidant has resulted in 9
A report that BA can be synthesized with a yield of 0% or more (P.
M. Keehn et. al. , Tetrahedro
n Lett. , 23 , 3135, (1982)), but in this case, it is not practical in that a special oxidizing agent is used.

[0008]

The present inventors have found that PHET
As a result of various studies on the reaction of the above, surprisingly, by oxidizing with molecular oxygen in a basic aqueous solution, it was possible to obtain PH at a high yield in the absence of a catalyst without using a special oxidizing agent.
We have found that BA can be synthesized and completed the present invention.

That is, the gist of the present invention is that 1- (4-hydroxyphenyl) -2-hydroxy-1-ethanone is oxidized by molecular oxygen in the presence of a basic substance and water. It exists in a method for producing para-hydroxybenzoic acids. Hereinafter, the present invention will be described in detail. The basic substance that can be used in the present invention is not particularly limited, but a strong base soluble in water is preferable, and specifically, sodium hydroxide, potassium hydroxide, barium hydroxide, magnesium oxide, sodium carbonate, potassium carbonate, Examples thereof include inorganic and organic bases such as sodium hydrogen carbonate, potassium hydrogen carbonate, sodium phosphate, diethylamine, trimethylamine, pyridine, tetramethylammonium hydroxide and tetrabutylammonium hydroxide. The basic substance is used in a molar ratio of 0.1 to PHET.
1 to 10.0, preferably 1.0 to 4.0 times. The reaction is usually carried out in a water solvent, but an organic solvent compatible with water inert to the reaction may be used in combination.

In the present invention, water usually exists as an aqueous solvent for basic substances. The amount of water present, i.e.
The concentration of the reaction solution is not particularly limited as long as it can maintain the dissolved state of the basic substance, but if it is too dilute, the reaction rate will be slow. Therefore, considering the reaction rate, it is desirable that the concentration be somewhat high. An oxidizing gas is usually used as the molecular oxygen used in the present invention.

As the oxidizing gas, pure oxygen, air, or a mixed gas of oxygen and an inert gas such as nitrogen can be used. Usually, the reaction proceeds at normal pressure, but it may be under pressure. The reaction temperature is, for example, 0 ° C to 150 ° C.
℃, preferably 25 ℃ ~ 100 ℃ is good. The reaction time varies depending on the reaction conditions or the basic substance used and can be arbitrarily selected, but is, for example, 0.5 to 10 hours. Since PHBA formed in the reaction solution is usually dissolved as a salt, PHBA can be recovered by means such as acid precipitation.

In the present invention, by using such raw materials and reaction conditions, PHBA can be easily obtained in high yield without using a special catalyst.

[0013]

EXAMPLES The present invention will be described in more detail with reference to examples, but the invention is not limited to the following examples as long as the gist of the present invention is not exceeded.

Example 1 In a 10 ml glass reactor, under nitrogen atmosphere, 3.042 g (NaOH; 2.10 mmol) of 2.64 wt% sodium hydroxide aqueous solution,
After PHET 0.076 g (0.500 mmol) was charged and the inside of the reactor was replaced with pure oxygen, the mixture was stirred in a pure oxygen atmosphere (normal pressure) at 30 ° C. for 3 hours. After the reaction is completed, the reaction solution is subjected to liquid chromatography (column; MCI Gel).
ODS-1MU, eluent; methanol / water / acetic acid / n-
Octylamine = 20/80 / 0.7 / 0.5, detector; UV (254 nm))
0.402 mmol, 4-hydroxyphenylglyoxylic acid (PHGA) 0.054 mmol, PHET
It contained 0.001 mmol. The conversion of PHET was 99.8% and the yield of PHBA was 80.5%.

Example 2 In a 50 ml three-necked flask equipped with a thermometer and a condenser, 6.05 g (NaOH; 2.1 mmo) of a 1.39 wt% sodium hydroxide aqueous solution.
l), and then PHET 0.152g (1.00m
(mol) was added, and the mixture was stirred at 50 ° C. for 4 hours in the atmosphere. When the reaction liquid was analyzed by liquid chromatography after the completion of the reaction, the conversion of PHET was 97.4% and the yield of PHBA was 53.8%. Concentrated hydrochloric acid was added to the reaction solution to obtain pH =
After adjusting to 1, extracted with diethyl ether, silica gel column chromatography (acetic acid / n-hexane = 4)
/ 6) to obtain 0.069 g of PHBA. The isolation yield was 49.6%.

(Example 3) The same reactor as in Example 2 was charged with 3.66 g (4.02 mmol) of a 10 wt% tetramethylammonium hydroxide aqueous solution, and 0.152 g (1.00 mmol) of PHET was added. The reaction was carried out in the atmosphere at 30 ° C. for 5 hours. After completion of the reaction, when analyzed by liquid chromatography, the conversion rate of PHET was 85.6% and the yield of PHBA was 58.5%.

(Example 4) 3.70 wt% potassium hydroxide aqueous solution 6.3 instead of sodium hydroxide aqueous solution 6.3
The same procedure as in Example 2 was performed, except that 1 g (4.15 mmol) was used and the reaction was performed at 30 ° C. for 6 hours. After the reaction, the reaction solution was analyzed by liquid chromatography to find that PHE
The conversion rate of T is 94.7%, and the yield of PHBA is 65.6%.
Met.

[0018]

INDUSTRIAL APPLICABILITY According to the present invention, PHBA can be easily produced in a high yield from a cheap raw material called PHET without a catalyst. Therefore, the method of the present invention provides great industrial benefits.

Claims (1)

[Claims] 1. 1- (4-hydroxyphenyl) -2-
A method for producing para-hydroxybenzoic acids, which comprises oxidizing hydroxy-1-ethanones with molecular oxygen in the presence of a basic substance and water.