Processes for producing tetrafluorophthalic anhydride

Abstract: A process for producing tetrafluorophthalic anhydride, which comprises chlorinating tetrachlorophthalic anhydride to obtain 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone, then fluorinating it to obtain 3,4,5,6-tetrafluorophthaloyldifluoride and/or 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone, and further reacting the tetrafluorophthalolyldifluoride and/or the hexafluoro-1-[3H]-isobenzofuranone with an inorganic base or an organic acid to obtain tetrafluorophthalic anhydride.

Description: The present invention relates to a novel process for producing tetrafluorophthalic anhydride which is useful as intermediate for medicines. Tetrafluorophthalic anhydride is an important compound as an intermediate for medicines, agricultural chemicals and liquid crystals. Methods for obtaining tetrafluorophthalic anhydride include (1) a method of dehydrating tetrafluorophthalic acid in the presence of an acid catalyst (Kogyo Kagaku Zasshi Vol. 73, 447, 1970), (2) a method of azeotropically dehydrating tetrafluorophthalic acid in xylene (Japanese Unexamined Patent Publication No. 306945/1990), and (3) a method of hydrolyzing tetrafluorophthalimide as the starting material in the presence of concentrated sulfuric acid, acetic acid and water, followed by removal of water (Japanese Examined Patent Publication No. 57255/1993). Methods (1) and (2) have a problem that it is difficult to prepare tetrafluorophthalic acid. Preparation of tetrafluorophthalic acid is disclosed in Japanese Unexamined Patent Publications No. 85349/1986, No. 61948/1987, No. 258442/1988 and US patent 5,047,553). However, in each method, a large amount of a polar solvent is required in the purification step, and it is necessary to extract the product from an aqueous layer. Further, to obtain the desired product in a high purity, a further step of e.g. recrystallization is required. Thus, these methods are not industrially advantageous. Method (3) has a problem of treating waste liquid and a problem that yield is low. It is an object of the present invention to provide a novel process for producing tetrafluorophthalic anhydride. Namely, the present invention provides a process for producing tetrafluorophthalic anhydride, which comprises chlorinating tetrachlorophthalic anhydride to obtain 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone, then fluorinating it to obtain 3,4,5,6-tetrafluorophthaloyldifluoride and/or 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone, and further reacting the tetrafluorophthaloyldifluoride and/or the hexafluoro-1-[3H]-isobenzofuranone with an inorganic base or an organic acid to obtain tetrafluorophthalic anhydride. The route to produce tetrafluorobenzoic anhydride from tetrachlorophthalic anhydride is not necessarily clear, but may be represented by the following formula: Tetrachlorophthalic anhydride is a compound which is readily available on an industrial scale. Conventional chlorination means and conditions can be used for the method of chlorinating the tetrachlorophthalic anhydride to obtain 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone. For example, the method can be carried out by means of a usual chlorination agent. As the chlorination agent, phosphorus pentachloride, phosphorus oxychloride or thionyl chloride is preferred, and phosphorus pentachloride is particularly preferred. The chlorination agent is used usually in an amount of from 0.01 to 10 mols, preferably from 0.5 to 2 mols, per mol of tetrachlorophthalic anhydride. The chlorination reaction can be carried out in the presence or absence of a solvent. The solvent is not particularly limited so long as it is capable of dissolving the reactants. However, an aprotic polar solvent or aprotic non-polar solvent is preferred. As the aprotic polar solvent, sulfolane, N,N-dimethyl formamide or 1,3-dimethylimidazolidinone may, for example, be mentioned. As the aprotic non-polar solvent, toluene, xylene, trichlorobenzene, dichlorobenzene or monochlorobenzene may preferably be employed. The solvent is used usually in an amount of from 0.01 to 100 parts by weight, preferably from 0.1 to 5 parts by weight, per part by weight of tetrachlorophthalic anhydride. The reaction temperature for the chlorination reaction may suitably be changed depending upon the type of the chlorination agent, the presence or absence of a solvent, the type of the solvent or the amounts of the reactants. In a usual case, it is from 20 to 300°C, preferably from 100 to 200°C. The 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone obtained by the above chlorination reaction, is subjected to a fluorination reaction to obtain 3,4,5,6-tetrafluorophthaloyldifluoride and/or 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone. The fluorination reaction can be carried out by reacting the isobenzofuranone with a fluorination agent. As the fluorination agent, an alkali metal fluoride is preferred. Particularly preferred is NaF, KF, RbF or CsF. Among them, KF is preferred, and particularly preferred is spray-dried potassium fluoride. The fluorination agent is used usually in amount of from 0.1 to 20 mols, preferably from 2 to 12 mols, per mol of 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone. The above fluorination reaction can be carried out in the presence or absence of a solvent. However, it is preferred to conduct the reaction in the presence of a solvent. The solvent is not particularly limited so long as it is capable of dissolving the reactants. However, an aprotic solvent or an aprotic non-polar solvent is preferred. As the aprotic solvent, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, dimethylsulfone, sulfolane, hexamethylphosphoric triamide, N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, acetonitrile, benzonitrile, dioxane, diglyme or tetraglyme is, for example, preferred, and sulfolane or N,N-dimethylformamide is particularly preferred. As the aprotic non-polar solvent, toluene, xylene, trichlorobenzene, dichlorobenzene or monochlorobenzene is, for example, preferred. The solvent is used usually in an amount of from 0.5 to 10 parts by weight, preferably from 1 to 5 parts by weight, per part by weight of the 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone. At the time of the fluorination reaction, a phase transfer catalyst may be incorporated as a reaction accelerator. As the phase transfer catalyst, a quaternary ammonium salt such as tetramethylammonium chloride or tetrabutylammonium bromide, a pyridinium salt such as N-neopentyl-4-(N',N'-dimethylamino-pyridinium chloride or N-(2-ethyl-hexyl)-4-(N',N'-dimethylamino)pyridinium chloride, or a quaternary phosphonium salt such as tetrabutylphosphonium bromide or tetraphenylphosphonium bromide, may, for example, be mentioned. Among them, tetrabutylphosphonium bromide or tetraphenylphosphonium bromide is preferred. The phase transfer catalyst is used usually in an amount of from 1 to 50 parts by weight, preferably from 5 to 20 parts by weight, per 100 parts by weight of the 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone. The reaction temperature for the above fluorination reaction is usually from 50 to 250°C, preferably from 100 to 230°C. 3,4,5,6-Tetrafluorophthaloyldifluoride and 3,3,4,5,6,7-hexafluro-1-[3H]-isobenzofuranone obtained by the above fluorination reaction, are usually obtained in the form of a mixture. However, they may be separated, as the case requires, to obtain them individually alone. The 3,4,5,6-tetrafluorophthaloyldifluoride and/or the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone obtained by the above method, is reacted with an inorganic base or an organic acid to form tetrafluorophthalic anhydride. The proportions of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone are not particularly limited. They may be used in any proportions, or they may be used individually alone. As the inorganic base, an alkali metal salt is preferred. As the alkali metal salt, sodium hydrogen carbonate, potassium hydrogen carbonate, sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide or calcium carbonate is, for example, preferred. Particularly preferred is sodium carbonate or potassium carbonate. The inorganic base is used usually in an amount of from 0.01 to 50 parts by weight, preferably from 0.3 to 1.5 parts by weight, per part by weight of the total amount of the 3,4,5,6-tetrafluorophthalolydifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone. As the organic acid, an organic carboxylic acid is preferred, which may be an aliphatic carboxylic acid or an aromatic carboxylic acid. As the aliphatic carboxylic acid, formic acid, acetic acid, propionic acid, butanoic acid or trifluoroacetic acid is, for example, preferred. As the aromatic carboxylic acid, benzoic acid, p-chlorobenzoic acid, 2,3-dichlorobenzoic acid or p-methyl benzoic acid is, for example, preferred. Among them, an aliphatic carboxylic acid is preferred, and acetic acid is particularly preferred. The organic carboxylic acid is used usually in an amount of from 0.01 to 1000 mols, preferably from 0.5 to 20 mols, per mol of the total amount of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone. The above mentioned reaction of the 3,4,5,6-tetrafluorophthaloyldifluoride and/or 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone with the inorganic base or the organic acid, can be carried out by heating in the presence or absence of a solvent. As the solvent, an aprotic solvent is preferred. As the aprotic solvent, an aprotic non-polar solvent or an aprotic polar solvent may be used. As the aprotic polar solvent, N,N-dimethylformamide, N,N-dimethylacetamide, dimethylsulfoxide, dimethylsulfone, sulfolane, hexamethylphosphoric triamide, N-methyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, acetonitrile, benzonitrile, dioxane, diglyme or tetraglyme is, for example, preferred. As the aprotic non-polar solvent, toluene, xylene, naphthalene, chlorobenzene or dichlorobenzene is, for example, preferred. The amount of the solvent for the reaction with the inorganic base is usually from 0.01 to 10 parts by weight, preferably from 0.5 to 5 parts by weight, per part by weight of the total amount of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone. Further, the amount of the solvent for the reaction with the organic acid is usually from 0.01 to 100 parts by weight, preferably from 0.5 to 20 parts by weight, per part by weight of the total amount of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone. The reaction temperature is usually at a level of from 300 to 400°C in either case of the reaction with the inorganic base or the reaction with the organic acid. However, the temperature may suitably be changed depending upon the type or amount of the inorganic base or the organic acid, the presence or absence, or the type of the solvent, or the amount of the reactant. From the obtained tetrafluorophthalic anhydride, a 2,3,4,5-tetrafluorobenzoic acid ester, 2,3,4,5-tetrafluorobenzoic acid and a 3-substituted-2,4,5-trifluorobenzoic acid can be synthesized, which are useful as intermediates for medicines and agricultural chemicals. The present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted by such specific Examples. EXAMPLE 1 Into a 2 ℓ glass reactor equipped with a reflux condenser and a stirrer, 500 g (1.74 mols) of tetrachlorophthalic anhydride, 441 (2.10 mols) of phosphorus pentachloride and 100 g of phosphorus oxychloride were charged, and the mixture was heated to 135°C without stirring. Then, it was stirred for 18 hours while maintaining the temperature at 140±5°C. Then, phosphorus oxychloride was removed by distillation. Then, phosphorus oxychloride and phosphorus pentachloride were distilled off under reduced pressure. The temperature of the reactor was lowered to 120°C, and 200 g of toluene and 2 ℓ of hexane were gradually added thereto, and the mixture was left to stand overnight. Crystals were collected by filtration and dried under reduced pressure to obtain 430.0 g of 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone. The yield was 72.1 %. EXAMPLE 2 Into a 1ℓ glass reactor equipped with a reflux condenser and a stirrer, 80 g (0.235 mol) of the 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone prepared in Example 1, 109.0 g (1.88 mols) of spray dried potassium fluoride and 320 g of sulfolane were charged, and the mixture was reacted at 130°C for 5 hours with vigorous stirring. Then, the reaction solution was subjected to distillation to obtain 42.8 g of a mixture (1:1) of 3,4,5,6 3,4,5,6-tetrafluorophthaloyldifluoride and 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone. yield was 75.2%. From the mixture, 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone was separated by distillation, and the 19 F-NMR spectrum and the boiling point were measured. 19F-NMR(CD 3 COCD 3 ,CFC 13 )δ:-76.4(s,2F),-136.0(m,1F),-140.2(m,1F),-140.7(m,1F),-146.1(m,1F) bp. 47°C/7mmHg EXAMPLE 3 Into a 500 ml glass reactor equipped with a reflux condenser and a stirrer, 100 g (0.413 mol) of the mixture (1:1) of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone of Example 2, 43.8 g (0.413 mol) of sodium carbonate and 200 g of xylene were charged, and the mixture was reacted at 130°C for 3 hours with vigorous stirring. Then, the inorganic substance was removed by filtration, and the residue was subjected to distillation to obtain 83.1 g of tetrafluorophthalic anhydride. The yield was 91.5 %. EXAMPLE 4 Into a 500 ml glass reactor equipped with a reflux condenser and a stirrer, a 100 g (0.413 mol) of a mixture (1:1) of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone of Example 2, and 43.8 g (0.413 mol) of sodium carbonate were charged, and the mixture was reacted at 130°C for 5 hours with vigorous stirring. Then, the reaction mixture was subjected to distillation to obtain 75.6 g of tetrafluorophthalic anhydride. The yield was 83.2%. EXAMPLE 5 Into a 100 ml glass reactor equipped with a reflux condenser and a stirrer, 50 g (0.207 mol) of the mixture (1:1) of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone of Example 2, and 17.4 g (0.207 mol) of sodium hydrogen carbonate were charged, and the mixture was reacted at 130°C for 5 hours with vigorous stirring. Then the reaction mixture was separated by distillation to obtain 33.0 g of tetrafluorophthalic anhydride. The yield was 72.5%. EXAMPLE 6 Into a 500 ml glass reactor equipped with a reflux condenser and a stirrer, 100 g (0.413 mol) of the 3,4,5,6-tetrafluorophthaloyldifluoride separated by distillation from the mixture of Example 2, 43.8 g (0.413 mol) of sodium carbonate and 200 g of xylene were charged, and the mixture was reacted at 130°C for 1.5 hours with vigorous stirring. Then, the inorganic substance was removed by filtration, and the residue was separated by distillation to obtain 84.9 g of tetrafluorophthalic anhydride. The yield was 93.4%. EXAMPLE 7 Into a 500 ml glass reactor equipped with a reflux condenser and a stirrer, 100 g (0.413 mol) of the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone separated by distillation from the mixture of Example 2, and 43.8 g (0.413 mol) of sodium carbonate were charged, and the mixture was reacted at 130°C for 8 hours with vigorous stirring. Then, the reaction mixture was separated by distillation to obtain 79.5 g of tetrafluorophthalic anhydride. The yield was 87.5%. EXAMPLE 8 Into a 200 ml glass reactor equipped with a reflux condenser and a stirrer, 50 g (0.207 mol) of the mixture (1:1) of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone of Example 2, and 50 ml of acetic acid were charged, and the mixture was refluxed for 16 hours with vigorous stirring. Then, the reaction mixture was separated by distillation to obtain 29.3 g of tetrafluorophthalic anhydride. The yield was 64.3%. EXAMPLE 9 Into a 200 ml glass reactor equipped with a reflux condenser and a stirrer, 50 g (0.207 mol) of the mixture (1:1) of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone of Example 2, and 50 ml of trifluoroacetic acid were charged, and the mixture was refluxed for 72 hours with vigorous stirring. Then, the reaction mixture was separated by distillation to obtain 29.6 g of tetrafluorophthalic anhydride. The yield was 65%. EXAMPLE 10 Into a 200 ml glass reactor equipped with a reflux condenser and a stirrer, 50 g (0.207 mol) of the mixture (1:1) of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone of Example 2, and 79.0 g (0.414 mol) of 2,4-dichlorobenzoic acid were charged, and the mixture was reacted at 150°C for 6 hours with vigorous stirring. Then, the reaction mixture was separated by distillation to obtain 28.5 g of tetrafluorophthalic anhydride. The yield was 62.5%. EXAMPLE 11 Into a 300 ml glass reactor equipped with a reflux condenser and a stirrer, and 50 g (0.207 mol) of the mixture (1:1) of the 3,4,5,6-tetrafluorophthaloyldifluoride and the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone, 59.3 g (0.31 mol) of 2,4-dichlorobenzoic acid and 100 ml of xylene were charged, and the mixture was reacted at 150°C for 12 hours with vigorous stirring. Then, the reaction mixture was separated by distillation to obtain 32.8 g of tetrafluorophthalic anhydride. The yield was 72.05%. EXAMPLE 12 Into a 300 ml glass reactor equipped with a reflux condenser and a stirrer, 100 g (0.413 mol) of the 3,4,5,6-tetrafluorophthaloyldifluoride separated by distillation from the mixture of Example 2, and 100 ml of acetic acid were charged, and the mixture was reacted at 130°C for 1.5 hours with vigorous stirring. Then, the inorganic substance was removed by filtration, and the residue was separated by distillation to obtain 66.8 g of tetrafluorophthalic anhydride. The yield was 73.5%. EXAMPLE 13 Into a 300 ml glass reactor equipped with a reflux condenser and a stirrer, 100 g (0.413 mol) of the 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone obtained in Example 2, and 100 ml of acetic acid were charged, and the mixture was reacted for 48 hours under reflux. Then, the reaction mixture was separated by distillation to obtain 79.5 g of tetrafluorophthalic anhydride. The yield was 87.5%. According to the process of the present invention, tetrafluorophthalic anhydride can be obtained efficiently using a readily available compound as a starting material. Each reaction is easy and safe and provides good yield. Accordingly, the process is very advantageous from the industrial point of view.

Claims: A process for producing tetrafluorophthalic anhydride, which comprises chlorinating tetrachlorophthalic anhydride to obtain 3,3,4,5,6,7-hexachloro-1-[3H]-isobenzofuranone, then fluorinating it to obtain 3,4,5,6-tetrafluorophthaloyldifluoride and/or 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone, and further reacting the tetrafluorophthaloyldifluoride and/or the hexafluoro-1-[3H]-isobenzofuranone with an inorganic base or an organic acid to obtain tetrafluorophthalic anhydride. The process according to Claim 1, wherein the fluorination is conducted by means of an alkali metal fluoride. A process for producing tetrafluorophthalic anhydride, which comprises reacting 3,4,5,6-tetrafluorophthaloyldifluoride and/or 3,3,4,5,6,7-hexafluoro-1-[3H]-isobenzofuranone with an inorganic base or an organic acid to obtain tetrafluorophthalic anhydride. The process according to any one of Claims 1 to 3, wherein the inorganic base is sodium carbonate or potassium carbonate. The process according to any one of Claims 1 to 3, wherein the organic acid is an organic carboxylic acid. 3,3,4,5,6,7-Hexafluoro-1-[3H]-isobenzofuranone.

Inventors: KUMAI SEISAKU, SEKI RYUJI, SUGIMOTO KOJI, KUMAI, SEISAKU, SEKI, RYUJI, SUGIMOTO, KOJI, KUMAI, SEISAKU, ASAHI GLASS COMPANY LTD., SEKI, RYUJI, ASAHI GLASS COMPANY LTD., SUGIMOTO, KOJI, ASAHI GLASS COMPANY LTD.
Applicants: ASAHI GLASS CO LTD, ASAHI GLASS COMPANY LTD.
Application year: 1995
Main classification: C07C51
IPC codes: C07D307, C07C67, C07C51