JP3038100B2 - Method for producing aromatic carboxylic acids - Google Patents

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 aromatic carboxylic acids useful as intermediates for synthesizing pharmaceuticals, agricultural chemicals, liquid crystal compounds and the like.

[0002]

2. Description of the Related Art Alkyl-substituted aromatic carboxylic acids have been conventionally produced by oxidation of the corresponding aromatic aldehydes with permanganate or chromic acid. And several alternative reactions have been proposed.

[0003] For example, a method of obtaining aromatic carboxylic acids by oxidizing cumin aldehyde with hydrogen peroxide under alkaline conditions using an inorganic alkali salt such as sodium hydroxide or potassium hydroxide (JP-A-63-264551). A method for synthesizing carboxylic acids by treating a saturated or unsaturated alicyclic or aromatic aldehyde with an organic peracid in a basic organic solvent to obtain the corresponding carboxylic acid No. 157345)
Etc. have been proposed.

[0004]

However, the reaction using hydrogen peroxide and an inorganic alkali salt is dangerous and cannot be said to be an industrial production method. In addition, the oxidation reaction with peracetic acid in a basic organic solvent is not a problem in the reaction itself, but a method of adding a large amount of water to precipitate the product after the reaction is completed. It is difficult to recover the used water-miscible basic organic solvent, and there is a problem to be solved in terms of production cost.

[0005]

DISCLOSURE OF THE INVENTION The present inventors have intensively studied a method for producing an aromatic carboxylic acid which is industrially advantageous by improving the problems of the prior art as described above. As a result, when the corresponding aromatic aldehyde is oxidized with an organic peracid in a water-immiscible organic solvent, the oxidation is performed in the presence of an alkali metal salt of an organic acid, so that it can be safely performed under mild reaction conditions. It has been found that the reaction can be carried out and aromatic carboxylic acids can be obtained with high purity and high yield. Furthermore, it was found that the water-immiscible organic solvent used in the reaction can be recovered and reused, which is extremely advantageous in terms of cost.

[0006] The substituted aromatic aldehydes used as a raw material in the present invention can be easily obtained on the market, or can be easily synthesized by a conventional method such as a Sommelet reaction of benzyl chloride. .

The production method of the present invention is characterized in that the aromatic aldehyde is oxidized by acting an organic peracid in a water-immiscible organic solvent in the presence of an alkali metal salt of an organic acid. It is.

The water-immiscible organic solvent that can be used in the present invention includes, for example, benzene, toluene, xylene,
Pentane, hexane, methylene chloride and the like can be mentioned. The amount of the water-immiscible organic solvent to be used is not particularly limited and can be arbitrarily selected. Usually, about 0.5 to about 1 part by weight of the aromatic aldehyde of the formula (1) is used.
A range of about 20 parts by weight is often employed.

The organic peracid used in the method of the present invention includes, for example, aliphatic or aromatic organic peracids such as peracetic acid, perbenzoic acid, and metachloroperbenzoic acid. The use amount of these organic peracids is not strictly limited and can be varied in a wide range. In general, for example, about 0.5 to about 5 mol per mol of aromatic aldehyde, Preferably, the amount used is in the range of about 1 to about 2 mol.

Further, the alkali metal salts of organic acids used in the method of the present invention include, for example, lactic acid, acetic acid,
Examples thereof include sodium salts and potassium salts of organic acids such as propionic acid, citric acid, malic acid and tartaric acid. The use amount of these organic acid salts is not strictly limited, but generally, aromatic aldehyde 1
About 0.1 to about 5 moles, preferably about 0.5
It can be added in the range of up to about 1.5 moles.

Next, the method for synthesizing aromatic carboxylic acids according to the present invention will be described more specifically. First, a raw material aromatic aldehyde, a water-immiscible organic solvent, and an organic acid alkali metal salt are charged into a reaction vessel at a ratio within the above range, and while suppressing heat generation by stirring and cooling, about 0 to about 50 ° C., preferably About 1 to 3
About twice the molar amount of organic peracid is added dropwise over a period of about 30 minutes to about 10 hours, preferably about 1 to about 4 hours. After continuing the stirring reaction at the same temperature for about 1 to about 6 hours, water is added by about 0.5 to about 2 times the weight of the total amount of the reaction mixture to terminate the reaction.

Next, the solvent layer is separated and collected, washed with a warm water, a diluted acid, a diluted alkaline aqueous solution or the like by a conventional method, and the solvent is recovered to obtain a desired crude product. The resulting crude product can be dissolved in an appropriate solvent such as hexane, toluene, or hydroalcohol, if desired, and recrystallized to obtain a high-purity product.

Hereinafter, embodiments of the present invention will be described more specifically with reference to examples.

[0014]

EXAMPLE 1 A 2-liter reaction flask was charged with 600 g of toluene, 200 g (1.35 mol) of cuminaldehyde and 111 g (1.35 mol) of anhydrous sodium acetate, cooled, stirred, and kept at 25-35 ° C. % Peracetic acid 3
08 g (1.62 mol) in 1 . Added over 5 hours. Thereafter, stirring was continued at the same temperature for 4 hours, 500 ml of water was added, washing with water, washing with hot water, washing with a warm FeSO ₄ aqueous solution was performed three times, and washing with warm water was performed.
(98% yield). The obtained crude product is treated with hexane 2
000 ml, and allowed to stand overnight to precipitate crystals, which was filtered to obtain 195 g of purified cumic acid (88% yield). And allowed to stand still overnight and concentrated filtration solution was obtained secondary crystals 12.5g precipitate crystals (yield 6%).

Example 2 A 0.5 liter reaction flask was charged with 100 g of toluene, 50 g (0.34 mol) of cuminaldehyde and 33.4 g (0.34 mol) of potassium acetate, and cooled.
While stirring and maintaining at 30 to 40 ° C, 40% peracetic acid.
6 g (0.34 mol) were added over 1 hour. Thereafter, stirring was continued for 5 hours at the same temperature, 300 ml of water was added, and the mixture was washed with water.
After washing with hot water, washing with a warm FeSO ₄ solution three times, and washing with warm water, the solvent was recovered to obtain 57.5 g of crude cumic acid (yield 95%). This crude product was recrystallized from hexane in the same manner as in Example 1 to obtain 55 g of purified cumic acid (yield: 91%).
%).

Example 3 400 g of toluene, 200 g (1.67 mol) of p-tolylaldehyde and 160.3 g (1.67 mol) of anhydrous sodium propionate were placed in a 2 liter reaction flask.
l), 552 g (2.0%) of a 50% solution of perbenzoic acid in toluene while cooling, stirring and maintaining at 25 to 35 ° C.
The mole) 1. Added over 5 hours. Thereafter, stirring was continued at the same temperature for 5 hours, 500 ml of water was added, and washing with hot water, washing with hot water, washing with a warm FeSO ₄ aqueous solution were further performed three times with warm water,
The solvent was recovered and 223 g of crude p-methylbenzoic acid (yield 9
8%). The obtained crude product is hexane 2000m
, and allowed to stand overnight to precipitate crystals, which were filtered to obtain 200 g of purified p-methylbenzoic acid (88% yield). The filtrate was concentrated and allowed to stand still overnight to precipitate crystals to obtain 15 g of secondary crystals (yield 6.6%).

Example 4 100 g of toluene and p were placed in a 0.5 liter reaction flask.
-50 g of isobutylbenzaldehyde (0.308 mol
l) and 23.3 g of sodium acetate (0.308 mol
l), cooling, stirring, and maintaining the temperature at 30 to 40 ° C., adding 67 g (0.355 mol) of 40% peracetic acid to 0.5%.
Added over time. Thereafter, stirring was continued at the same temperature for 5 hours, 100 ml of water was added, and the mixture was washed with water, washed three times with an aqueous solution of FeSO ₄ ,
After washing with water, the solvent was recovered to obtain 52 g of a crude product.
(95% yield). This crude product was recrystallized from toluene to obtain 49.5 g of purified p-isobutylbenzoic acid (yield 90%).

The analytical values of this compound were as follows.

¹ H-NMR (CDCl ₃ , TMS, δ) 0.90 (6H, d, J = 6.5 Hz), 1.90 (1H, m), 2.54 (2H, d, J = 6.5 H)
z), 7.23 (2H, d, J = 7.9Hz), 8.02 (2H, d, J = 7.9Hz), 12.0
0 (1H, br) ¹³ C-NMR (CDCl ₃ , TMS, δ) 22.4, 30.1, 45.6, 127.1, 129.3, 130.2, 148.
4, 172.6

[0020]

According to the present invention, when an aromatic aldehyde is oxidized with an organic peracid, an alkali metal salt of an organic acid is allowed to coexist in an amount of 0.25 equivalent or more with respect to the raw material aldehyde, thereby achieving extremely mild conditions. The reaction proceeds, and even when hydrogen peroxide is generated in the reaction system, there is no danger at all because it is trapped by organic acid ions, and the desired aromatic carboxylic acids can be produced inexpensively with high purity and high yield. Thus, it is possible to provide a process for producing the compound which is very industrially advantageous.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Warita Kanagawa Prefecture, Kawasaki City, Kawasaki City, 335 Karijuku Hasegawa Kaori Co., Ltd. In Kawasaki Research Institute (72) Inventor Maki Matsumoto Kanagawa Prefecture Kawasaki City, Nakahara-ku Karajuku 335 Hasegawa Kaori Co., Ltd. Kawasaki Research Institute Co., Ltd. (56) References JP-A-3-157345 (JP, A) JP-A-63-264551 (JP) JP-A-59-227840 (JP, A) JP-A-64-19035 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C07C 51/285 C07C 63/04 C07C 63/06

Claims (2)

(57) [Claims] [Claim 1] The following formula (1) In the formula, R represents a C ₁ -C ₅ lower alkyl group. An aromatic aldehyde represented by the following formula is oxidized with an organic peracid to give the following formula (2): In the formula, R represents a C ₁ -C ₅ lower alkyl group, and the oxidation is carried out using an organic peracid in the presence of an organic acid alkali metal salt. A process for producing an aromatic carboxylic acid of the above formula (2), which is characterized in that: 2. The method according to claim 1, wherein R is an isopropyl group.