JPS6143130A - Production of 1,2,3,4-tetrafluorobenzene - Google Patents

Abstract

PURPOSE:To produce 1,2,3,4-tetrafluorobenzene useful as an intermediate of agricultural chemicals and pharmaceuticals, easily, in high yield, in an industrial scale, by decarbonating 3,4,5,6-tetrafluorophthalic acid in an aqueous medium at a specific temperature under autogeneous pressure. CONSTITUTION:The objective 1,2,3,4-tetrafluorobenzene can be prepared economically, by carrying out the decarbonation of 3,4,5,6-tetrafluorophthalic acid in an aqueous medium 210-300 deg.C, preferably 230-270 deg.C, further preferably in the presence of one or more catalysts selected from copper, zinc, cadmium, iron, cobalt, or nickel, the oxide, hydroxide or carbonate of said metals, expecially copper powder, cupric oxide or zinc oxide at 100-270 deg.C, especially 160-240 deg.C under autogeneous pressure. The amount of the catalyst is preferably about 0.1-10pts.wt., especially 0.3-2pts.wt. per 100pts.wt. of the above raw material.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention decarboxylates 3.4.5.6-tetrafluorophthalic acid in an aqueous medium to produce 1.2.3.4-tetrafluorobenzene. Regarding new manufacturing methods.

1,2.3.4-Tetrafluorobenzene is useful as an intermediate for pharmaceuticals and agricultural chemicals.

(Prior Art) Conventionally, many techniques for decarboxylating heptatalic acid derivatives in an aqueous medium have been disclosed [for example, Chemical Abst
41, p. 2083 (1947), U.S. Patent No. 1,939,212, etc.]. However, all of these methods yield benzoic acid, and only a few methods yield benzene derivatives by further decarboxylation. In particular, there is no known method to obtain halogenated benzene by decarboxylating halogenated phthalic acid. However, U.S. Patent No. 243
In No. 9237, 3.4.5.6-tetrachlorophthalic anhydride was heated in an alkaline aqueous solution at 220-280°C under pressure.
1.2.3.4-tetrachlorobenzene is obtained by heating in the temperature range of . However, there is no description regarding fluorinated substances.

The present inventors K investigated whether the method of the above-mentioned US Pat. No. 2,439,237 could be applied to 3,4,5,6-tetrafluorophthalic acid, which is the starting material in the present invention.

3,4.5 in alkaline aqueous solution according to the method described above.
．． A decarboxylation reaction was attempted by heating 6-tetrafluorophthalic acid. However, trifluorophenol in which a fluorine atom was substituted with a hydroxyl group was mainly produced, and 1,2,3,4-tetrafluorobenzene could not be selectively obtained. That is, the fluorine atom at the para position of the benzene nucleus with an electron-withdrawing group such as -COOH group is
It can be said that it is more susceptible to nucleophilic substitution reactions than the chlorine atom at the same position, and therefore it is thought that the alkaline substance used in the above-mentioned US Pat. No. 2,439,237 replaces the fluorine atom to produce phenols. That is, the method uses 3, 4.5.6, which are the starting materials in the present invention.
-Tetrafluorophthalic acid is not applicable because side reactions are likely to occur. Furthermore, the only method for obtaining 1,2,3,4-tetrafluorobenzene by decarboxylating 3.4.5.6-tetrafluorophthalic acid is described in British Patent No. 2122190. The details of this method are unknown, but there is a description of the reaction temperature, which is 200
Although the reaction is carried out at a temperature of 1.2.3.4-tetrafluorobenzene, the yield is only 0.5-, and this is not an industrial method.

(Problems to be Solved by the Invention) That is, the purpose of the present invention is to decarboxylate 3.4.5.6-tetrafluorophthalic acid to industrially produce 1.2.3.4-tetrafluorobenzene. It is an object of the present invention to provide a method for manufacturing with high yield.

(Means for Solving the Problems) When producing 1.2.3.4-tetrafluorobenzene, the above general decarboxylation method cannot be applied, and the present inventors have earnestly developed a new method. As a result of investigation, it was surprisingly found that 1.2.3.4 could be prepared by simply dissolving 3.4.5.6-tetrafluorophthalic acid in water and heating it in an autoclave at a temperature range of 210-300°C. - It has been discovered that tetrafluorobenzene can be easily produced.

In addition, when at least one component selected from copper, zinc, cadmium, iron, cobalt, or nickel metal, oxide, hydroxide, or carbonate is present as a catalyst, the temperature range is 100 to 270°C. The present inventors have discovered that 1,2,3,4-tetrafluorobenzene can be easily produced by decarboxylating it at a much lower temperature by heating it in an autoclave, and have completed the present invention.

That is, the present invention is specified as follows.

(1,2,3,4-tetrafluorobenzene, characterized in that 113,4,s, 6-tetrafluorophthalic acid is decarboxylated in an aqueous medium at a temperature ranging from 210 to 300° C. under spontaneous pressure. manufacturing method.

(2) The method described in (1) above, wherein decarboxylation is carried out at a temperature in the range of 230 to 270°C.

(3) 3,4,5.6-5-Drafluorophthalic acid in an aqueous medium from each metal, oxide, hydroxide or carbonate of copper, zinc, cadmium, iron, copper or nickel. In the presence of at least one selected catalyst, 1
A process for producing 1,2.3.4-tetrafluorobenzene, which comprises decarboxylation under spontaneous pressure at a temperature in the range of 00 to 270°C.

(The method described in (3) above, wherein the decarboxylation is carried out at a temperature in the range of 41,160 to 240°C.

(5) The above (wherein the catalyst is at least one selected from steel powder, cupric oxide, and zinc oxide)
3) or the method described in (4).

Hereinafter, specific embodiments of the present invention will be explained.

Tetrafluorophthalic acid used in the present invention can be prepared, for example, by applying phthalonitrile to activated carbon with chlorine at 270 to 35
Tetrachlorophthalonitrile is synthesized by supplying it in a temperature range of 0°C, and the resulting tetrachlorophthalonitrile is fluorinated by the method described in Japanese Patent Application No. 58-202590 (Example 2) to obtain tetrafluorophthalonitrile. The resulting tetrafluorophthalonitrile can be synthesized by a method of carrying out a hydrolysis reaction by heating the resulting tetrafluorophthalonitrile in an aqueous sulfuric acid solution at 150-180'C.

In the present invention, when tetrafluorophthalic acid is dissolved in water without the presence of a catalyst and heated using an autoclave, the reaction temperature is preferably in the range of 210 to 300°C, particularly in the temperature range of 230 to 270°C. is preferred. When the reaction temperature is high, the reaction rapidly decreases and is an exothermic reaction, making temperature control difficult. In addition, when the reaction temperature is low, the rate of decarboxylation reaction decreases, intermediates having monocarboxyl groups are likely to be produced, and the competitive human stomach xylation reaction of tetrafluorophthalic acid is also likely to occur. 2゜3.4-? ) This is not preferred because the yield of lafluorobenzene decreases.

As for the reaction time, it is necessary to conduct the reaction at a temperature such that the decarboxylation reaction occurs preferentially and the hydroxylation reaction that occurs competitively is suppressed, so the temperature range is 210 to 320°C, preferably 230 to 270°C. It is preferable to complete the reaction within a short time, within about 10 hours.

The reaction temperature in the presence of a catalyst is 100 to 270
A temperature range of 160°C to 240°C is particularly preferred. If the reaction temperature is high, no catalyst is required. Furthermore, if the reaction temperature is low, the reaction rate decreases and productivity decreases, which is not preferable.

One advantage of the presence of a catalyst is that it increases the rate of decarboxylation, thereby controlling the hydroxylation reaction and improving yield. Furthermore, since the reaction can be carried out at a low reaction temperature, the naturally occurring pressure is low, and the pressure resistance of the autoclave can be lowered, so that the equipment cost of the autoclave can be reduced. The reaction time varies depending on the reaction temperature and is not particularly limited, but is generally preferably in the range of 1 to 30 hours.

As a catalyst for the deoxidation reaction in the present invention, each metal of copper, zinc, cadmium, iron, cobalt or nickel,
At least one selected from oxides, hydroxides, and carbonates is preferably present. In particular, it is preferable to include at least one selected from steel powder, cupric oxide, and zinc oxide.

The amount of catalyst is 100
It is preferable that it is present in an amount of about 0.1 to 10 parts by weight. In particular, it is preferably present in an amount of 0.3 to 2 parts by weight. The starting material, tetrafluorophthalic acid, is preferably added in an amount of about 3 to 30 parts per 100 parts by weight of water.

Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to these.

Example 1 3.4,5.6-tetrafluorophthalic acid 5. Of! (0,021 mol) and water soy were charged and heated and stirred at 250° C. for 3 hours to react. After the reaction was completed, the mixture was cooled to room temperature, and then separated into layers, and the lower layer (oil layer) was taken out. This oil layer was packed with column packing material y8B52 2m.

When analyzed using a gas chromatograph at a column tank temperature of 50°C, it was found that 1,
2,3.4-tetrafluorobenzene 82.4 mol%,
) Lifluorophenol 3.3 molti, 2.3.4.5
- 5.8 moles of tetrafluorobenzoic acid were found. This oil layer was purified using a precision fractionator to obtain the desired product 1.2.3.
4-tetrafluorobenzene 2.3 JF (normal pressure 94
The fraction at ~95°C) could be recovered.

Example 2 10.0.9 (0,042 mol) of tetrafluorophthalic acid, sag of water, and 0.15 If of steel powder as a catalyst were placed in an autoclave at 100 eC, and the mixture was heated and stirred at 180° C. for 5 hours to react. After the reaction was completed, the mixture was cooled to room temperature and the suspended catalyst was removed by filtration. The mother liquor separated into two layers was separated and analyzed in the same manner as in Example 1. 1.2.
3.4-Tetrafluorobenzene 86.1 mol.

Example 3 0.1 g of cupric oxide was charged as a catalyst, and 3
The mixture was charged and reacted in the same manner as in Example 2, except that it was heated and stirred for a period of time, and then separated and analyzed in the same manner to obtain 91.2 mol of 1.2.3.4-tetrafluorobenzene.

Example 4 0.05% zinc oxide and F were charged as a catalyst, and the temperature was 220°C.
Prepare, react, separate, and analyze in the same manner as in Example 2, except that the mixture was heated and stirred for 2 hours. , 2°3.4-tetrafluorobenzene 79.6 mol% 75f was observed. - Comparative Example 1 It was prepared in the same manner as in Example 1, and heated and stirred at 205° C. for 4 hours to react. After the reaction was completed, the reaction mixture was cooled to room temperature, and the suspended precipitate was filtered out to obtain 2.3.4.5-tetrafluorobenzoic acid 3.4.9'. This corresponded to a yield of 83.5 molti based on the starting 3.4.5.6-tetrafluorophthalic acid. It was confirmed by NMR, mass spectrum, and elemental analysis that it was 2.3.4.5-tetrafluorobenzoic acid.

On the other hand, when the mother liquor was separated and then analyzed by gas chromatography, it was found that 9.2 mol of 1.2.3.4-tetrafluorobenzene was found relative to the charged 3.4.5.6-tetrafluorophthalic acid. Ta.

Comparative Example 2 A mixture was prepared in the same manner as in Example 1, and the mixture was heated and stirred at 205° C. for 24 hours to react. After the reaction was completed, the oil layer was separated in the same manner as in Example 1. As in Example 1, analysis using a gas probe revealed that 61.2 moles of 1,2,3,4-tetrafluorobenzene and 61.2 moles of 1,2,3,4-tetrafluorobenzene and 24.9 mol of fluoropheol and 7.4 mol of 12,3,4,5-tetrafluorobenzoic acid were obtained.

Patent applicant: Nippon Shokubai Kagaku Kogyo Co., Ltd. Procedural amendment (spontaneous) Date: 10/1/1980 Manabu Shiga, Commissioner of the Patent Office 1, Indication of the case: 1982 Patent Application No. 164282 25 Name of the invention 1, 2. 394-Tetrafluorobenzene manufacturing method 3, person making the correction

Claims (5)

[Claims] (1) 1,2,3,4-tetrafluorophthalic acid, which is characterized by decarboxylating 3,4,5,6-tetrafluorophthalic acid in an aqueous medium at a temperature in the range of 210 to 300°C under spontaneous pressure. Manufacturing method of fluorobenzene. (2) The method according to claim (1), wherein the decarboxylation is carried out at a temperature in the range of 230 to 270°C. (3) 3,4,5,6-tetrafluorophthalic acid in an aqueous medium, containing at least one metal selected from copper, zinc, cadmium, iron, cobalt, or nickel, an oxide, a hydroxide, or a carbonate. In the presence of one type of catalyst, 100-2
1. A process for the preparation of 1,2,3,4-tetrafluorobenzene, characterized in that it is decarboxylated under autogenous pressure at a temperature in the range of 70°C. (4) The method according to claim (3), wherein the decarboxylation is carried out at a temperature in the range of 160 to 240°C. (5) The method according to claim (3) or (4), wherein the catalyst is at least one selected from steel powder, cupric oxide, and zinc oxide.