JP2007182426A - Method for producing tetrafluoroterephthalic acid difluoride - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an industrially advantageous method for producing tetrafluoroterephthalic acid difluoride and a tetrafluoroterephthalic acid diester compound. <P>SOLUTION: This method for producing tetrafluoroterephthalic acid difluoride is provided by reacting tetrachloroterephthalic acid dichloride with potassium fluoride in the presence of dimethylsulfone. The method for producing tetrafluoroterephthalic acid diester expressed by formula (2) [wherein, R is a 1-6C alkyl] is provided by reacting the tetrafluoroterephthalic acid difluoride with an alcoholic compound expressed by formula (1) [wherein, R is the same as the above]. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for producing tetrafluoroterephthalic acid difluoride.

  Tetrafluoroterephthalic acid difluoride is an important compound as a pharmaceutical and agrochemical intermediate. As a method for producing tetrafluoroterephthalic acid difluoride, for example, a method of reacting tetrachloroterephthalic acid dichloride and potassium fluoride without solvent in an autoclave (see, for example, Non-Patent Document 1), sulfolane, diglyme, diphenyl sulfone. , Nitrobenzene, N, N-dimethylacetamide, N-methyl-2-pyrrolidone or benzonitrile in which tetrachloroterephthalic acid dichloride is reacted with potassium fluoride (for example, see Patent Document 1), calixarene as a catalyst A method of reacting tetrachloroterephthalic acid dichloride with potassium fluoride in sulfolane using, for example, is known. However, these methods have problems in that high-temperature and high-pressure conditions are required or expensive catalysts are required, and development of further improved methods has been demanded.

Japanese Examined Patent Publication No. 4-66220 Chinese Patent Publication No. 1458137 Probl. Organ. Sinteza, Akad. Nauk SSSR, Otd. Obshch. I Tekhn. Khim. 1965, 105-108

  Under such circumstances, the present inventor diligently studied a method for producing tetrafluoroterephthalic acid difluoride using a reaction between tetrachloroterephthalic acid dichloride and potassium fluoride, and carried out the reaction in the presence of dimethylsulfone. Thus, it was found that the fluorination reaction proceeds efficiently even under normal pressure conditions without using an expensive catalyst, and the present invention was achieved.

  That is, the present invention provides a method for producing tetrafluoroterephthalic acid difluoride, in which tetrachloroterephthalic acid dichloride and potassium fluoride are reacted in the presence of dimethyl sulfone.

  According to the present invention, tetrafluoroterephthalic acid that can be used as a raw material for medicines and agricultural chemicals, etc. by carrying out a fluorination reaction using recoverable dimethylsulfone as a solvent without using a special reaction apparatus or an expensive catalyst. Since difluoride can be produced efficiently, it is industrially advantageous.

  Hereinafter, the present invention will be described in detail.

  Tetrachloroterephthalic acid dichloride can be produced, for example, by a known method described in Japanese Patent Publication No. 2-11571.

  A commercially available thing may be used for potassium fluoride, for example, what is obtained from potassium hydroxide and hydrogen fluoride may be used. A smaller particle size is preferred, and a smaller water content is preferred. Examples of such preferable potassium fluoride include potassium fluoride obtained by a spray dry method.

  If the amount of potassium fluoride used is usually 6 moles or more with respect to tetrachloroterephthalic acid dichloride, the object of the present invention can be achieved and there is no particular upper limit, but preferably 6 from the economical viewpoint. It is the range of 10 mol times.

  Commercially available dimethyl sulfone may be used, for example, synthesized by a known method such as oxidation of dimethyl sulfoxide with an oxidizing agent such as hydrogen peroxide (for example, see US Pat. No. 6,552,231). A thing may be used.

  Although the usage-amount of dimethyl sulfone is not restrict | limited, Practically, it is 0.1-20 weight times with respect to tetrachloro terephthalic-acid dichloride, Preferably it is the range of 2-10 weight times.

  The reaction temperature is usually in the range of 120 to 200 ° C.

  This reaction is preferably carried out in the presence of an organic solvent inert to the reaction. Examples of the organic solvent inert to the reaction include ether solvents such as dioxane and diethylene glycol dimethyl ether; N, N-dialkylamide solvents such as N, N-dimethylacetamide; aromatics such as toluene, xylene, chlorobenzene and benzonitrile. Hydrocarbon solvents; aliphatic hydrocarbon solvents such as octane and decane; and the like. These organic solvents inert to the reaction may be used alone or in combination of two or more.

  Among them, it is more preferable to use an organic solvent whose boiling point is lower than that of dimethylsulfone and whose melting point is lower than that of dimethylsulfone, which is inert to the reaction and has an organic boiling point of 100 to 200 ° C. A solvent is more preferable, and an organic solvent that is inert to the reaction, has a boiling point of 100 to 200 ° C., and a melting point of 50 ° C. or less is particularly preferable.

  The amount of the organic solvent inert to the reaction is usually 0.001 to 0.5 times by weight, preferably 0.001 to 0.2 times by weight with respect to dimethylsulfone.

  This reaction is carried out by mixing tetrachloroterephthalic acid dichloride, potassium fluoride, dimethylsulfone and, if necessary, an organic solvent inert to the reaction, heating to a predetermined temperature, and stirring. Although the mixing order is not particularly limited, it is preferable to carry out the reaction after dehydrating the reaction system in advance. As a dehydration method, for example, a method in which potassium fluoride and dimethylsulfone are mixed and heated; a mixture of potassium fluoride and dimethylsulfone is used by using an organic solvent azeotropic with water such as toluene and xylene. Azeotropic dehydration method; and the like. What is necessary is just to mix the mixture after performing this dehydration process, and the tetrachloro terephthalic-acid dichloride.

  This reaction is usually performed under normal pressure conditions, but may be performed under pressurized conditions. The progress of the reaction can be confirmed by ordinary analytical means such as gas chromatography or liquid chromatography.

  After completion of the reaction, tetrafluoroterephthalic acid difluoride can be isolated by a normal isolation operation such as vacuum distillation. The obtained tetrafluoroterephthalic acid difluoride may be further purified by an ordinary purification method such as rectification.

（式中、Ｒは炭素数１〜６のアルキル基を表す。）
で示されるアルコール化合物（以下、アルコール（１）と略記する。）とを反応させることにより、式（２）

（式中、Ｒは上記と同一の意味を表す。）
で示されるテトラフルオロテレフタル酸ジエステル化合物（以下、テトラフルオロテレフタル酸ジエステル（２）と略記する。）を製造することができる。以下、かかるエステル化反応について説明する。 Further, the obtained tetrafluoroterephthalic acid difluoride and the formula (1)

(In the formula, R represents an alkyl group having 1 to 6 carbon atoms.)
Is reacted with an alcohol compound represented by formula (2) (hereinafter abbreviated as alcohol (1)).

(In the formula, R represents the same meaning as described above.)
The tetrafluoroterephthalic acid diester compound (hereinafter abbreviated as tetrafluoroterephthalic acid diester (2)) can be produced. Hereinafter, such esterification reaction will be described.

  As the tetrafluoroterephthalic acid difluoride, the mixture obtained by the above reaction may be used as it is, or may be used after being isolated from the mixture. From the viewpoint of simple operation and the recovery and recycling of dimethyl sulfone described below, the mixture after the reaction is preferably used as it is.

  Examples of the alkyl group having 1 to 6 carbon atoms represented by R include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n- Examples include a linear, branched or cyclic alkyl group such as a pentyl group, a cyclopentyl group, and a cyclohexyl group.

  Examples of the alcohol (1) include methanol, ethanol, n-propanol, isopropanol, n-butanol, tert-butanol, and cyclohexanol. As the alcohol (1), commercially available products can be used.

  The amount of alcohol (1) used is usually 2 mol times or more with respect to tetrafluoroterephthalic acid difluoride, and the upper limit thereof is not particularly limited. , In a range of 2 to 50 moles with respect to tetrafluoroterephthalic acid difluoride.

  When the mixture after the above reaction is used as it is as tetrafluoroterephthalic acid difluoride, it can be carried out without newly using an organic solvent, but when an isolated one is used, it can be used in the presence of the organic solvent. It is preferable to implement. Examples of the organic solvent include aromatic hydrocarbon solvents such as toluene, xylene and chlorobenzene; aliphatic hydrocarbon solvents such as pentane, hexane and heptane; halogenated hydrocarbon solvents such as dichloromethane, dichloroethane and chloroform; diethyl ether, And ether solvents such as methyl tert-butyl ether; ester solvents such as ethyl acetate; The amount of the organic solvent used is not particularly limited.

  By esterification reaction, corrosive hydrogen fluoride is by-produced. Therefore, for example, do not allow hydrogen fluoride to stay in the reaction system by carrying out the reaction in the presence of a base, carrying out the reaction while blowing an inert gas, or carrying out the reaction under reduced pressure. Is industrially preferred. More preferably, the reaction is performed in the presence of a base, or the reaction is performed while blowing an inert gas.

  Examples of the base used in carrying out the reaction in the presence of a base include tertiary amine compounds such as triethylamine and diisopropylethylamine; nitrogen-containing aromatic compounds such as pyridine, collidine and quinoline; and alkali metal carboxylates such as sodium acetate. Salts; alkali metal alcoholates such as sodium methylate and sodium ethylate; alkali metal hydroxides such as sodium hydroxide and potassium hydroxide; alkaline earth metal hydroxides such as calcium hydroxide and magnesium hydroxide; sodium carbonate; Alkali metal carbonates such as potassium carbonate; Alkali metal hydrogen carbonates such as sodium hydrogen carbonate and potassium hydrogen carbonate; Alkaline earth metal carbonates such as calcium carbonate and magnesium carbonate; Alkaline earth metals such as calcium hydrogen carbonate and magnesium hydrogen carbonate Metal bicarbonate And the like. It is preferable to use at least one selected from the group consisting of nitrogen-containing aromatic compounds, alkali metal carbonates, alkali metal hydrogen carbonates, alkaline earth metal carbonates and alkaline earth metal hydrogen carbonates, and alkali metal carbonates More preferably, alkali metal hydrogen carbonate, alkaline earth metal carbonate or alkaline earth metal hydrogen carbonate is used.

  The amount of the base used is usually in the range of 2 to 5 mol times with respect to tetrafluoroterephthalic acid difluoride.

  Examples of the inert gas include nitrogen, carbon dioxide, air and the like. The inert gas blowing flow rate is usually 1% by volume / min or more with respect to the reaction mixture, and there is no particular upper limit, but 30% by volume / min or less is preferable in terms of operability.

  The pressure for carrying out the reaction under reduced pressure is usually in the range of 6 to 100 kPa.

  Although the mixing order of tetrafluoroterephthalic acid difluoride and alcohol (1) is not particularly limited, when the reaction is carried out in the absence of a base, it is preferable to add tetrafluoroterephthalic acid difluoride to alcohol (1). When the reaction is carried out in the presence of a base, alcohol (1) is added to a mixture of tetrafluoroterephthalic acid difluoride and base under reaction temperature conditions, or base and alcohol (1) are added to tetrafluoroterephthalic acid difluoride. It is preferred to add a mixture of

  The temperature of esterification reaction is not specifically limited, Usually, it is the range of 0-100 degreeC. When performing reaction in presence of a base, the range of 0-30 degreeC is preferable.

  The esterification reaction is usually performed under normal pressure conditions, but may be performed under pressurized conditions. The progress of the reaction can be confirmed by ordinary analytical means such as gas chromatography or liquid chromatography.

  After completion of the reaction, the tetrafluoroterephthalic acid diester (2) can be isolated by subjecting the reaction mixture to the isolation means exemplified below. In addition, since potassium chloride, the salt derived from the used base, etc. usually precipitate in the reaction mixture, filtration treatment or the like may be performed if necessary, and isolation may be performed after removing the salt. As will be described later, when dimethyl sulfone is recycled, it is preferable to remove the salt at this stage.

<Isolation means 1>
For example, the reaction mixture is subjected to a distillation treatment to distill off the alcohol (1) and the organic solvent, and the resulting distillation residue and water are mixed to precipitate the tetrafluoroterephthalic acid diester (2) as crystals. Can do. If such crystals are collected by filtration, tetrafluoroterephthalic acid diester (2) can be isolated.

<Isolation means 2>
For example, the tetrafluoroterephthalic acid diester (2) may be taken out as an organic layer by mixing the reaction mixture and water, if necessary, in the presence of an organic solvent having low compatibility with water and performing a liquid separation treatment. it can. If such an organic layer is distilled, tetrafluoroterephthalic acid diester (2) can be isolated. Here, examples of the organic solvent having low compatibility with water include aromatic hydrocarbon solvents such as toluene, xylene and chlorobenzene; aliphatic hydrocarbon solvents such as pentane, hexane and heptane; dichloromethane, dichloroethane and chloroform. Halogenated hydrocarbon solvents; ether solvents such as diethyl ether and methyl tert-butyl ether; ester solvents such as ethyl acetate; and the like.

  The tetrafluoroterephthalic acid diester (2) obtained by the isolation means may be further purified by ordinary purification means such as crystallization and column chromatography.

  Examples of the tetrafluoroterephthalic acid diester (2) include dimethyl 2,3,5,6-tetrafluoroterephthalate, diethyl 2,3,5,6-tetrafluoroterephthalate, 2,3,5,6-tetra Di (n-propyl) fluoroterephthalate, diisopropyl 2,3,5,6-tetrafluoroterephthalate, di (n-butyl) 2,3,5,6-tetrafluoroterephthalate, 2,3,5,6 -Tetrafluoroterephthalic acid di (tert-butyl) and the like.

  In the esterification reaction, when the mixture after fluorination reaction is used as it is as the raw material tetrafluoroterephthalic acid difluoride, dimethylsulfone used in the fluorination reaction can be easily recovered. For example, the dimethylsulfone aqueous solution can be recovered as a filtrate when the isolation means 1 is applied, and as an aqueous layer when the isolation means 2 is applied. The recovered aqueous dimethylsulfone solution can be recycled for the fluorination reaction if water is removed by distillation or the like. When the recovered aqueous dimethylsulfone solution contains an inorganic salt, the inorganic salt can be removed by desalting or filtration if necessary, and then recycled for the fluorination reaction.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited by these Examples.

Example 1
A 50 ml flask equipped with a reflux condenser was charged with 2.3 g of potassium fluoride (spray dry product), 8.5 g of dimethylsulfone and 20 g of toluene. The obtained mixture was heated to an internal temperature of 130 ° C., and water in the mixture was removed as an azeotrope with toluene. Thereafter, substantially all of toluene was distilled off at an internal temperature of 140 ° C., and the resulting mixture was cooled to an internal temperature of 100 ° C. The mixture was charged with 1.7 g of tetrachloroterephthalic acid dichloride and 600 mg of xylene, heated to 145 ° C., and incubated and stirred for 6 hours while stirring at the same temperature. During the reaction, no dimethylsulfone solid adhered to the top of the flask or the cooling tube. After the reaction, the mixture was cooled to room temperature, 10 g of methanol was added, and the precipitated crystals were finely crushed and then stirred at room temperature for 1 hour. After the precipitated crystals were filtered, the crystals were washed with 5 g of methanol, the filtrate and the washing solution were combined, and methanol was distilled off by a concentration operation. When 30 g of water was added to the concentrated residue, crystals were precipitated. Crystals obtained by filtration were washed with water and dried to obtain 1.3 g of dimethyl 2,3,5,6-tetrafluoroterephthalate as light yellow crystals. When analyzed by gas chromatography internal standard method, the content of dimethyl 2,3,5,6-tetrafluoroterephthalate was 90.0%. Yield: 87%

Example 2
A 50 ml flask equipped with a reflux condenser was charged with 480 mg of potassium fluoride, 3.0 g of dimethyl sulfone and 10 g of toluene as used in Example 1. The obtained mixture was heated to an internal temperature of 130 ° C., and water in the mixture was removed as an azeotrope with toluene. Thereafter, substantially all of toluene was distilled off at an internal temperature of 140 ° C., and the resulting mixture was cooled to an internal temperature of 100 ° C. The mixture was charged with 340 mg of tetrachloroterephthalic acid dichloride, heated to 150 ° C., and stirred for 4 hours while stirring at the same temperature. During the reaction, dimethyl sulfone solid adhered to the upper part of the flask, and stirring was not possible at the end of the reaction. After the reaction, the mixture was cooled to room temperature, 10 g of methanol was added, and the precipitated crystals were finely crushed and then stirred at room temperature for 1 hour. 10 g of ethyl acetate was added and analyzed by gas chromatography internal standard method to determine the yield.
Yield of dimethyl 2,3,5,6-tetrafluoroterephthalate: 50%
Yield of dimethyl 2,3,5-trifluoro-6-chloroterephthalate: 21%
Yield of difluoro and dimethyl dichloroterephthalate (total of three isomers): 23%

Example 3
A 50 ml flask equipped with a reflux condenser was charged with 2.3 g of the same potassium fluoride used in Example 1, 8.5 g of dimethyl sulfone, and 20 g of toluene. The obtained mixture was heated to an internal temperature of 130 ° C., and water in the mixture was removed as an azeotrope with toluene. Thereafter, substantially all of toluene was distilled off at an internal temperature of 140 ° C., and the resulting mixture was cooled to an internal temperature of 100 ° C. The mixture was charged with 1.7 g of tetrachloroterephthalic acid dichloride and 590 mg of xylene, heated to 145 ° C., and incubated and stirred for 4 hours while stirring at the same temperature. During the reaction, no dimethylsulfone solid adhered to the top of the flask or the cooling tube. After the reaction, the mixture was cooled to 110 ° C., 20 g of xylene was added, a part of the organic layer was sampled, and 2,3,5,6-tetrafluoro as a main product was analyzed by gas chromatography / mass spectrometry. It was confirmed that difluoride terephthalate was obtained and the raw material had disappeared. The solution was cooled to 60 ° C., 5 g of methanol was added, and the mixture was stirred at 60 ° C. for 1 hour. Further, after cooling to room temperature, 30 g of water was added and stirred to form a two-layer solution. The organic layer is separated by a liquid separation operation, the aqueous layer is extracted once with 10 g of toluene, the obtained organic layer and the previous organic layer are combined, washed with water, the organic layer is concentrated, 1.5 g of dimethyl 3,5,6-tetrafluoroterephthalate was obtained as brown crystals. When analyzed by gas chromatography internal standard method, the content of dimethyl 2,3,5,6-tetrafluoroterephthalate was 77.3%. Yield: 84%

Example 4
A 50 ml flask equipped with a reflux condenser was charged with 2.3 g of the same potassium fluoride used in Example 1, 8.5 g of dimethyl sulfone, and 20 g of toluene. The obtained mixture was heated to an internal temperature of 130 ° C., and water in the mixture was removed as an azeotrope with toluene. Thereafter, substantially all of toluene was distilled off at an internal temperature of 140 ° C., and the resulting mixture was cooled to an internal temperature of 100 ° C. The mixture was charged with 1.7 g of tetrachloroterephthalic acid dichloride and 150 mg of xylene, heated to 145 ° C., and kept warm and stirred for 2 hours while stirring at the same temperature. During the reaction, no dimethylsulfone solid adhered to the top of the flask or the cooling tube. After the reaction, the reaction mixture was cooled to 110 ° C. In another 100 ml flask, 25 g of methanol was charged and cooled to 10 ° C. The reaction mixture was added to the flask, and then the resulting mixture was heated to 60 ° C. and stirred while keeping it warm for 1 hour. After the precipitated crystals were filtered, the crystals were washed with 5 g of methanol, the filtrate and the washing solution were combined, 17 g of water was added thereto, and methanol was distilled off by a concentration operation. The concentrated residue was extracted twice with 10 g of toluene, and the organic layers were combined, then concentrated and dried to obtain 1.38 g of dimethyl 2,3,5,6-tetrafluoroterephthalate as light yellow crystals. . When analyzed by a gas chromatography internal standard method, the content of dimethyl 2,3,5,6-tetrafluoroterephthalate was 92.5%. Yield: 96%
Moreover, dimethyl sulfone was collect | recovered as an aqueous layer after toluene extraction. The weight of the aqueous layer was 27 g.

Example 5
A 50 ml flask equipped with a reflux condenser was charged with 27 g of the water layer after toluene extraction obtained in Example 4 and 20 g of toluene, heated to an internal temperature of 130 ° C., and water in the water layer was azeotroped with toluene. Removed as a mixture. To this, 2.3 g of the same potassium fluoride used in Example 1 was charged. The obtained mixture was heated to an internal temperature of 130 ° C., and water in the mixture was removed as an azeotrope with toluene. Thereafter, substantially all of toluene was distilled off at an internal temperature of 140 ° C., and the resulting mixture was cooled to an internal temperature of 100 ° C. The mixture was charged with 1.7 g of tetrachloroterephthalic acid dichloride and 150 mg of xylene, heated to 145 ° C., and incubated and stirred for 3 hours while stirring at the same temperature. During the reaction, no dimethylsulfone solid adhered to the top of the flask or the cooling tube. After the reaction, the mixture was cooled to room temperature, 10 g of methanol was added, and the precipitated crystals were finely crushed and then stirred at room temperature for 1 hour. 10 g of ethyl acetate was added and analyzed by gas chromatography internal standard method to determine the yield.
Yield of dimethyl 2,3,5,6-tetrafluoroterephthalate: 73%
Yield of dimethyl 2,3,5-trifluoro-6-chloroterephthalate: 12%
Yield of difluoro and dimethyl dichloroterephthalate (total of three isomers): 11%

Example 6
A 500 ml flask equipped with a reflux condenser was charged with 23 g of the same potassium fluoride used in Example 1, 85 g of dimethyl sulfone, and 30 g of toluene. The obtained mixture was heated to an internal temperature of 130 ° C., and water in the mixture was removed as an azeotrope with toluene. Thereafter, the temperature was kept at 140 ° C. until no distillation of toluene was observed. Further, the pressure was reduced to 20 mmHg (corresponding to 2.67 kPa) at the same temperature, almost all of toluene was distilled off, the pressure was reduced to normal pressure with nitrogen, and the resulting mixture was cooled to an internal temperature of 100 ° C. The mixture was charged with 17 g of tetrachloroterephthalic acid dichloride and 1.5 g of toluene, heated to 145 ° C., and stirred for 3 hours while stirring at the same temperature. During the reaction, no dimethylsulfone solid adhered to the top of the flask or the cooling tube. After the reaction, the mixture was cooled to 110 ° C., 300 g of toluene was added, and the mixture was further cooled to 60 ° C. 100 g of methanol was added thereto, followed by stirring at room temperature for 10 hours while blowing nitrogen gas. After stirring, methanol was removed by concentration, 200 g of water and 6.9 g of potassium carbonate were added to the concentrated residue, and after stirring, the mixture was separated to obtain an organic layer. The organic layer was concentrated and dried to obtain 13.2 g of dimethyl 2,3,5,6-tetrafluoroterephthalate as light yellow crystals. When analyzed by gas chromatography internal standard method, the content of dimethyl 2,3,5,6-tetrafluoroterephthalate was 90.0%. Yield: 89%

Example 7
A 50 ml flask equipped with a reflux condenser was charged with 2.3 g of potassium fluoride (powder product), 8.5 g of dimethyl sulfone and 20 g of toluene. The obtained mixture was heated to an internal temperature of 130 ° C., and water in the mixture was removed as an azeotrope with toluene. Thereafter, substantially all of toluene was distilled off at an internal temperature of 140 ° C., and the resulting mixture was cooled to an internal temperature of 100 ° C. The mixture was charged with 1.7 g of tetrachloroterephthalic acid dichloride and 150 mg of xylene, heated to 145 ° C., and incubated and stirred for 3 hours while stirring at the same temperature. During the reaction, no dimethylsulfone solid adhered to the top of the flask or the cooling tube. After the reaction, the mixture was cooled to 110 ° C., 20 g of toluene was added, and further cooled to 10 ° C., 1.4 g of potassium carbonate was added, 2 g of methanol was added, and the mixture was stirred at the same temperature for 4 hours. The precipitated crystals were filtered, and the crystals were washed with 5 g of methanol, the filtrate and the washing solution were combined, and methanol and toluene were distilled off by a concentration operation. When 30 g of water was added to the concentrated residue, crystals were precipitated. Crystals obtained by filtration were washed with water and dried to obtain 1.1 g of dimethyl 2,3,5,6-tetrafluoroterephthalate as light yellow crystals. When analyzed by gas chromatography internal standard method, the content of dimethyl 2,3,5,6-tetrafluoroterephthalate was 85.0%. Yield: 72%
Yield of dimethyl 2,3,5-trifluoro-6-chloroterephthalate: 6%
Yield of difluoro and dimethyl dichloroterephthalate (3 isomers total): 6%

Comparative Example 1
A 50 ml flask equipped with a reflux condenser was charged with 2.3 g of the same potassium fluoride used in Example 1, 8.5 g of sulfolane, and 20 g of toluene. The obtained mixture was heated to an internal temperature of 130 ° C., and water in the mixture was removed as an azeotrope with toluene. Thereafter, substantially all of toluene was distilled off at an internal temperature of 140 ° C., and the resulting mixture was cooled to an internal temperature of 100 ° C. The mixture was charged with 1.7 g of tetrachloroterephthalic acid dichloride, heated to 155 ° C., and incubated and stirred for 4 hours while stirring at the same temperature. After the reaction, the mixture was cooled to room temperature, 10 g of methanol was added, and the mixture was stirred at room temperature for 1 hour. 10 g of ethyl acetate was added and analyzed by gas chromatography internal standard method to determine the yield.
Yield of dimethyl 2,3,5,6-tetrafluoroterephthalate: 0%
Yield of dimethyl 2,3,5-trifluoro-6-chloroterephthalate: 0%
Yield of dimethyl difluoro-dichloroterephthalate (total of three isomers): 27%
Yield of dimethyl 2-fluoro-3,5,6-trichloroterephthalate: 35%
Yield of dimethyl 2,3,5,6-tetrachloroterephthalate: 38%

  Tetrafluoroterephthalic acid difluoride and tetrafluoroterephthalic acid diester compound can be obtained by, for example, 2,3,5,6-tetrafluorobenzenedimethanol or 2,3,5 by the method described in Chinese Patent Publication No. 1458137. , 6-tetrafluoroparamethylbenzyl alcohol. These compounds are known to be useful as intermediates for household insecticides (see, for example, Japanese Patent No. 2606892). Therefore, the tetrafluoroterephthalic acid difluoride and the tetrafluoroterephthalic acid diester compound can be used as raw materials for medicines and agricultural chemicals, and the present invention has industrial applicability in that such compounds can be produced industrially advantageously. .

Claims (10)

A process for producing tetrafluoroterephthalic acid difluoride, comprising reacting tetrachloroterephthalic acid dichloride with potassium fluoride in the presence of dimethylsulfone. The process according to claim 1, wherein the reaction is carried out in the presence of an organic solvent inert to the reaction. The organic solvent inert to the reaction is at least one organic solvent selected from the group consisting of ether solvents, N, N-dialkylamide solvents, aromatic hydrocarbon solvents and aliphatic hydrocarbon solvents. Production method. The production method according to claim 2 or 3, wherein the organic solvent inert to the reaction is an organic solvent having a boiling point lower than that of dimethyl sulfone and a melting point lower than that of dimethyl sulfone. The method according to any one of claims 2 to 4, wherein the organic solvent inert to the reaction has a boiling point in the range of 100 to 200 ° C. The production method according to any one of claims 2 to 5, wherein the amount of the organic solvent inert to the reaction is 0.001 to 0.5 times by weight with respect to dimethylsulfone. Tetrafluoroterephthalic acid difluoride obtained by the production method according to claim 1 and formula (1)

(In the formula, R represents an alkyl group having 1 to 6 carbon atoms.)
Formula (2) for reacting with an alcohol compound represented by formula (2)

(In the formula, R represents the same meaning as described above.)
The manufacturing method of the tetrafluoro terephthalic-acid diester compound shown by these. The production method according to claim 7, wherein the reaction between tetrafluoroterephthalic acid difluoride and the alcohol compound represented by the formula (1) is carried out in the presence of a base. 9. The base according to claim 8, wherein the base is at least one selected from the group consisting of nitrogen-containing aromatic compounds, alkali metal carbonates, alkali metal hydrogen carbonates, alkaline earth metal carbonates, and alkaline earth metal hydrogen carbonates. Manufacturing method. The production method according to claim 7, wherein the reaction between the tetrafluoroterephthalic acid difluoride and the alcohol compound represented by the formula (1) is carried out while blowing an inert gas.