JPS6229571A - Production of quinolinic acid - Google Patents

Abstract

PURPOSE:To obtain in high yield the titled compound useful as an intermediate for synthesis of drugs, agricultural chemicals, dye, etc., by a simple oxidation method, by using 5,6,7,8-tetrahydroquinone as a starting raw material and oxidizing it by the use of an oxidizing agent in a liquid phase in a specific temperature range. CONSTITUTION:5,6,7,8-Tetrahydroquinone is used as a starting raw material and oxidized by the use of an oxidizing agent in a liquid phase at 20-250 deg.C in the presence or absence of a solvent, to give the aimed compound. Potassium permanganate, nitric acid, potassium dichromate, chlorine, etc., air or oxygen can be used as the oxidizing agent. Further, oxygen in a nascent state can be used. The amount of the oxidizing agent used is preferably 5-50 equivalents based on 1mol starting raw material. When the solvent is used, water, a hydrocarbon compound, etc., can be used. In the reaction method, when potassium permanganate is used, 1pt.wt. starting raw material is incorporated with 5-30pts.wt. water and 1-10pts.wt. oxidizing agent under reflux.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to a method for producing quinolinic acid.

(Prior Art) Quinolinic acid is an important substance as a synthetic intermediate for medicines, agricultural chemicals, dyes, and the like.

Various oxidation reactions have been proposed for synthesizing quinolinic acid using quinoline as a starting material.

For example, the oxidation of quinoline with potassium permanganate in an alkaline medium (Ber, dtsch, Ch
Em, Ger., 12°747 (1879)) has a very low yield and is accompanied by a large amount of by-products. Furthermore, the method of air oxidation of quinoline using a cobalt salt as a catalyst (Japanese Patent Application Laid-open No. 55673/1983) has the drawbacks of poor reaction efficiency and complicated control of catalyst concentration.

Another method has been proposed in which quinoline is oxidized with hydrogen peroxide in the presence of a copper salt (Japanese Unexamined Patent Publication No. 105964/1982), but the reaction operation is difficult and it is obtained as a copper salt of quinolinic acid. , which requires an extra reaction step to decompose it into quinolinic acid. Furthermore, it is difficult to completely remove copper ions, and the quinolinic acid thus obtained will always contain trace amounts of copper.

As described above, when quinoline is used as a starting material, there are disadvantages in industrial production such as complicated reaction operations, severe reaction conditions, and poor yield.

Another method for obtaining quinolinic acid is the nitric acid oxidation method of 8-oxyquinoline (Chem, Ber., 1 Sat., 505
(1947)), but unlike what is described in the literature, this method has a low yield and produces a large amount of by-products. Furthermore, a method has been proposed in which quinolines having a substituent on the benzene ring of quinoline are oxidized with chlorine ions in the presence of vanadyl (V) cations (Japanese Patent Application Laid-open No. 105964/1983). However, these methods require the introduction of substituents into quinoline, and are not suitable as raw materials.

(Problems to be Solved by the Invention) The present invention is a method for producing highly purified quinolinic acid in a high yield through simple reaction steps.

(Means for solving the problem) That is, the present invention provides a method for producing quinolinic acid, which comprises oxidizing 5,6,7,8-tetrahydroquinoline in a liquid phase at 20 to 250°C using an oxidizing agent. be.

The raw material of the present invention is 5,6,7,8-tetrahydroquinoline. Good yields cannot be obtained if other compounds such as quinoline, 1,2,3,4-tetrahydroquinoline, and decahydroquinoline are used as raw materials.

As the oxidation method, liquid phase oxidation is adopted, and the reaction may be carried out in the presence of a solvent, but it is not necessary. When a solvent is used, water, a hydrocarbon compound, an oxygen-containing hydrocarbon compound, etc. are used. can.

As the oxidizing agent, potassium permanganate, nitric acid, potassium dichromate, hydrogen peroxide, sodium hypochlorite, chlorine, etc., as well as air or oxygen can be used. Furthermore, oxygen from a generator can also be used. The amount of oxidizing agent used is 5, 6, 7
・5 to 50 per mole of 8-tetrahydroquinoline
Good equivalent weight.

The reaction temperature is 20 to 250°C, and 20°C
If the temperature is lower, the reaction will be difficult to proceed, and if it exceeds 250°C, the yield will decrease.

For the reaction method, a known method can be adopted, but for example, when using potassium permanganate, 5 to 30 parts of water and 1 to 10 parts of potassium permanganate are added to 1 part of 5,6,7,8-tetrahydroquinoline. 1 part and reflux.

In the case of oxygen oxidation, pure oxygen or oxygen diluted with air may be used, but air is preferably used. As the solvent, an aliphatic carboxylic acid such as acetic acid is preferably used, and the reaction is more preferably carried out under the catalyst of a transition metal salt such as cobalt or manganese. The reaction temperature is 30 to 250°C, and the reaction is carried out under normal pressure or increased pressure, preferably 2 to 30 atmospheres.

In the case of electrolytic oxidation, 10 to 50 parts of water is added to 1 part of 5,6,7,8-tetrahydroquinoline, and an amount of electricity of 4,000 to 40,000 coulombs is passed using carbon, platinum, etc. as an electrode. It will be done. The temperature is preferably in the range of 20 to 90°C. In addition, in some cases, vanadium pentoxide,
Metal oxides and metal salts such as chromium dioxide, selenium dioxide, ammonium molybdate, and cobalt acetate may be added as catalysts.

After the reaction is completed, solid matter is removed, and quinolinic acid is separated by acid precipitation. Further purification is performed by recrystallization if necessary.

(Example) An example of the present invention will be shown below, but this is merely shown for the purpose of explanation and is not intended to limit the scope of the present invention.

Example 1 5,6,7,8-tetrahydroquinoline 10g 1 water 500mj in 11 30 flasks! While stirring, add 22 g of potassium permanganate and heat. When the purple color of potassium permanganate disappears, 22 g of potassium permanganate and 500 m 12 of water are added.

After refluxing for about 3 hours, cool to 60°C, remove manganese dioxide by filtration, and wash with 200 ml of warm water.
The pH of the filtrate is adjusted to 1 to 1.5 with hydrochloric acid, and after cooling to 20°C, the precipitated quinolinic acid is obtained by suction filtration. 100ml of warm water (PH=1.5)! After washing with
Dry at °C.

The weight after drying was 9 g.

Example 2 5, 6, 7, to the anode side of an electrolytic cell partitioned by a porous wall
8-tetrahydroquinoline 5g 175%-sulfuric acid 75ml
, 50mA of vanadium pentoxide is charged, 20% to the cathode side.
80ml of sulfuric acid was charged. As electrodes, platinum black electrodes were used for both the anode and the cathode, and electrolysis was performed at 4 to 4.5 A for 8 hours.

During electrolysis, hydrogen was generated from the cathode side, so 5% sulfuric acid was replenished into the cathode cell at appropriate times during electrolysis.

After the reaction was completed, a portion of the reaction solution was extracted and subjected to gas chromatography analysis, and it was found that quinolinic acid had been produced in a yield of 85%.

(Effects of the Invention) According to the present invention, quinolinic acid can be obtained in good yield by a simple oxidation method.

Claims (1)

[Scope of Claims] A method for producing quinolinic acid, which comprises oxidizing 5,6,7,8-tetrahydroquinoline in a liquid phase using an oxidizing agent at 20 to 250°C.