JP7510783B2 - Method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) - Google Patents

Description

The present invention relates to a method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane).

Patent Document 1 discloses a method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) by reacting trifluoropyruvic acid fluoride as a raw material with hexafluoropropylene oxide in the presence of cesium fluoride in a diethylene glycol dimethyl ether solvent.

On the other hand, Patent Document 2 discloses the production of trifluoropyruvic acid fluoride dimer by reacting hexafluoropropylene oxide with benzophenone (Patent Document 2).

U.S. Pat. No. 3,308,107 British Patent No. 1051647

Poly[perfluoro(2-methylene-4-methyl-1,3-dioxolane)] can be obtained by polymerizing perfluoro(2-methylene-4-methyl-1,3-dioxolane) derived from perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane). Poly[perfluoro(2-methylene-4-methyl-1,3-dioxolane)] is a promising polymer for use as a resin for gas separation membranes, transparent resin for optical fibers, etc. Therefore, it is industrially desirable to provide a new method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane), which is the raw material for such promising polymers.

The inventors therefore investigated the production of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) using trifluoropyruvic acid fluoride dimer or trifluoropyruvic acid fluoride as a synthetic raw material. As a result of the inventors' investigations, it became clear that in the production method using trifluoropyruvic acid fluoride dimer or trifluoropyruvic acid fluoride as a synthetic raw material, it is desirable to improve the yield of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane).

In view of the above, the present invention aims to provide a method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) in good yield using trifluoropyruvic acid fluoride dimer and/or trifluoropyruvic acid fluoride as raw materials.

As a result of extensive research, the present inventors have newly discovered that it is possible to produce perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) in good yield using trifluoropyruvic acid fluoride dimer and/or trifluoropyruvic acid fluoride as raw materials by the following production method.

That is, the present invention is as follows.
[1] A reaction step of reacting at least one synthetic raw material selected from the group consisting of trifluoropyruvic acid fluoride dimer and trifluoropyruvic acid fluoride with hexafluoropropylene oxide in an organic solvent in the presence of a fluoride;
a by-product decomposition step of decomposing the by-products in the reaction solution obtained by the reaction step;
an isomerization step after the by-product decomposition step;
The present invention relates to a method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane).
[2] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [1], wherein the by-product decomposition step comprises heating the reaction solution at a temperature of 60° C. to 90° C.
[3] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [1] or [2], wherein the by-product decomposition step is carried out in a closed vessel.
[4] A method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [3], which comprises releasing the pressure in the closed vessel.
[5] A method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [4], which comprises heating the reaction solution in the closed container at a temperature of 60°C to 90°C while reducing the pressure in the container.
[6] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [4] or [5], comprising controlling the pressure in the closed container to less than 1.0 MPa by depressurizing.
[7] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [4], comprising heating the reaction solution in the closed vessel at a temperature of 60° C. to 90° C., cooling the reaction solution, and then depressurizing the solution one or more times.
[8] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [7], wherein the pressure inside the closed container during the heating is less than 1.0 MPa.
[9] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [1] or [2], wherein the by-product decomposition step is carried out in an open vessel.
[10] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of [1] to [9], wherein the organic solvent is an ether-based solvent.
[11] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [10], wherein the ether solvent is diethylene glycol dimethyl ether.
[12] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of [1] to [11], wherein the fluoride is an alkali metal fluoride.
[13] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [12], wherein the alkali metal fluoride is cesium fluoride.
[14] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of [1] to [13], wherein the amount of fluoride used in the reaction step is 0.05 to 0.4 molar times the amount of the synthesis raw material used in terms of monomer.
[15] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of [1] to [14], further comprising adding a fluoride in one or both of the by-product decomposition step and the isomerization step.
[16] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [15], wherein the amount of fluoride used in the reaction step is 0.05 to 0.1 molar amounts relative to the amount of the synthesis raw material used in terms of monomer.
[17] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [15] or [16], wherein the total amount of fluoride added in the reaction step, the by-product isomerization step, and the isomerization reaction step is 0.1 to 0.4 molar amounts relative to the amount of trifluoropyruvic acid fluorides used in terms of monomer.
[18] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of [1] to [17], comprising reacting trifluoropyruvic acid fluoride dimer with hexafluoropropylene oxide in an organic solvent in the presence of a fluoride in the reaction step.
[19] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to [17], further comprising a dimer synthesis step of synthesizing a trifluoropyruvic acid fluoride dimer before the reaction step.
[20] The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of [1] to [17], comprising reacting trifluoropyruvic acid fluoride with hexafluoropropylene oxide in an organic solvent in the presence of a fluoride in the reaction step.

According to the present invention, a manufacturing method can be provided that can produce perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) in good yield using trifluoropyruvic acid fluoride dimer and/or trifluoropyruvic acid fluoride as raw materials.

The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) of the present invention (hereinafter also simply referred to as "production method") comprises a reaction step of reacting trifluoropyruvic acid fluoride dimer and/or trifluoropyruvic acid fluoride with hexafluoropropylene oxide in an organic solvent in the presence of a fluoride, a by-product decomposition step of decomposing by-products in the reaction liquid obtained by the reaction step, and an isomerization step subsequent to the by-product decomposition step.
The above-mentioned production method will now be described in more detail.

[Reaction step]
In the above-mentioned production method, trifluoropyruvic acid fluoride dimer (hereinafter also simply referred to as "dimer") and/or trifluoropyruvic acid fluoride (hereinafter also referred to as "monomer") are used as raw materials for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane). In the present invention and this specification, as at least one synthesis raw material selected from the group consisting of trifluoropyruvic acid fluoride dimer and trifluoropyruvic acid fluoride, only the dimer may be used, only the monomer may be used, or the dimer and the monomer may be mixed in any ratio and used.

An example of the dimer is 4-fluoro-5-oxo-2,4-bis(trifluoromethyl)-1,3-dioxolane-2-carbonyl fluoride. 4-fluoro-5-oxo-2,4-bis(trifluoromethyl)-1,3-dioxolane-2-carbonyl fluoride can be represented by the following formula 1.

The above-mentioned production method may have a dimer synthesis step of synthesizing trifluoropyruvic acid fluoride dimer before the reaction step. An example of the reaction carried out in the dimer synthesis step is a reaction between hexafluoropropylene oxide and benzophenone in a closed system. For such a dimer synthesis step, see, for example, British Patent No. 1051647 (Patent Document 2).

Another example of the reaction carried out in the dimer synthesis step is the reaction of hexafluoropropylene oxide with aldehydes. More specifically, hexafluoropropylene oxide is reacted with aldehydes to produce an aldehyde adduct to hexafluoropropylene oxide, and the reaction is allowed to proceed further to obtain trifluoropyruvic acid fluoride dimer. As the aldehyde adduct, a cyclized type or a linear type can be produced depending on the manner in which the aldehyde is added to hexafluoropropylene oxide. As the aldehyde adduct, the following aldehyde adduct 1, 2, or 3 can be mentioned.

(In the above, R represents a substituted or unsubstituted alkyl group or aryl group).

In the dimer synthesis reaction in which hexafluoropropylene oxide reacts with aldehydes, hexafluoropropylene oxide and aldehydes are charged into a pressure vessel at room temperature or lower, and first reacted at 0°C to 100°C, preferably 0°C to 99°C, more preferably 0°C to 90°C for 0.5 to 24 hours to generate an aldehyde adduct to hexafluoropropylene oxide, and then the temperature is raised to 100°C or higher, preferably 100°C to 200°C, more preferably 100°C to 150°C, and the reaction is preferably performed for 5 to 48 hours. Room temperature is, for example, a temperature in the range of 20°C to 25°C. When generating an aldehyde adduct, the aldehyde may be charged into a pressure vessel in advance, and hexafluoropropylene oxide may be continuously or intermittently supplied at a temperature of 0°C to 100°C for 0.5 to 24 hours to cause the reaction.

Specific examples of aldehydes include propionaldehyde, butyraldehyde, valeraldehyde, isovaleraldehyde, pivalaldehyde, 1-adamantanecarbaldehyde, benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, 2-ethylbenzaldehyde, 3-ethylbenzaldehyde, 4-ethylbenzaldehyde, 2-methoxybenzaldehyde, 3-methoxybenzaldehyde, 4-methoxybenzaldehyde, 2-ethoxybenzaldehyde, 3-ethoxybenzaldehyde, Examples of the aldehyde include 4-ethoxybenzaldehyde, 2-fluorobenzaldehyde, 3-fluorobenzaldehyde, 4-fluorobenzaldehyde, 2-chlorobenzaldehyde, 3-chlorobenzaldehyde, 4-chlorobenzaldehyde, 2-bromobenzaldehyde, 3-bromobenzaldehyde, 4-bromobenzaldehyde, 1-naphthaldehyde, 5-methoxy-1-naphthaldehyde, 5-chloro-1-naphthaldehyde, 2-naphthaldehyde, 5-methoxy-2-naphthaldehyde, and 5-chloro-2-naphthaldehyde. Preferred are benzaldehyde, 2-methylbenzaldehyde, 3-methylbenzaldehyde, 4-methylbenzaldehyde, 2-ethylbenzaldehyde, 3-ethylbenzaldehyde, 4-ethylbenzaldehyde, 2-methoxybenzaldehyde, 3-methoxybenzaldehyde, 4-methoxybenzaldehyde, 2-ethoxybenzaldehyde, 3-ethoxybenzaldehyde, 4-ethoxybenzaldehyde, and the like. From the viewpoint of the yield of trifluoropyruvic acid fluoride dimer, it is preferable to use an aromatic aldehyde, and it is more preferable to use an aromatic aldehyde substituted with an electron donating group. It is preferable to use 0.8 to 1.2 molar amounts of aldehydes relative to the hexafluoropropylene oxide to be subjected to the reaction.

The reaction of hexafluoropropylene oxide with aldehydes can be carried out without a solvent, but solvents such as toluene, ethylbenzene, xylene, mesitylene, isopropylbenzene, anisole, and chlorobenzene may be used alone or in any combination of two or more. The amount of the solvent used may be in the range of 0.1 to 5.0 times by mass relative to the amount of hexafluoropropylene oxide used in the reaction. After the reaction, the mixture is cooled to room temperature and depressurized, and a layer consisting of a mixture of aldehydes, difluoromethyl compounds by-produced by the reaction, and/or solvent is separated and removed to obtain trifluoropyruvic acid fluoride dimer. The reaction is preferably carried out in a pressure-resistant vessel under conditions of 3.5 MPa or less, more preferably 1.2 MPa or less.

On the other hand, trifluoropyruvic acid fluoride (monomer) is represented by the following formula 2. The above production method may have a monomer synthesis step of synthesizing trifluoropyruvic acid fluoride before the reaction step. An example of the reaction carried out in the monomer synthesis step is the reaction of hexafluoropropylene oxide with benzophenone in a normal pressure flow system. For the monomer synthesis step, see, for example, the specification of U.S. Patent No. 3,308,107 (Patent Document 1).

Trifluoropyruvic acid fluoride has a low boiling point of 9°C to 10°C and is a gas at room temperature. In contrast, trifluoropyruvic acid fluoride dimer has a boiling point of 72°C and is a liquid at room temperature. From the viewpoint of ease of industrial handling, trifluoropyruvic acid fluoride dimer is preferred as a synthetic raw material.

In the reaction step, the synthetic raw material is reacted with hexafluoropropylene oxide in an organic solvent in the presence of a fluoride. The organic solvent is not particularly limited as long as it is inert to the reaction. Examples of the organic solvent include aromatic solvents such as toluene, ethylbenzene, xylene, and mesitylene, and ether solvents such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, and tetraethylene glycol dimethyl ether. The organic solvent may be used alone or in a mixture of two or more in any ratio. From the viewpoint of the solubility of the fluoride, it is preferable to use an ether solvent such as ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, or tetraethylene glycol dimethyl ether alone or in a mixture of two or more in any ratio as the organic solvent. The amount of the organic solvent used in the reaction is not particularly limited, but it can usually be used in an amount of 0.3 to 5.0 times by mass relative to the synthetic raw material to be subjected to the reaction.

The fluoride used in the reaction step is not particularly limited as long as it is a fluoride, but specifically, for example, alkali metal fluorides such as lithium fluoride, sodium fluoride, potassium fluoride, and cesium fluoride, alkaline earth metal fluorides such as beryllium fluoride, magnesium fluoride, calcium fluoride, strontium fluoride, and barium fluoride, and organic ammonium fluorides such as tetramethylammonium fluoride, tetraethylammonium fluoride, tetrapropylammonium fluoride, tetra-n-butylammonium fluoride, and phenyltrimethylammonium fluoride can be mentioned. From the viewpoint of solubility in an organic solvent and reaction activity, the fluoride is preferably one or more selected from the group consisting of sodium fluoride, potassium fluoride, cesium fluoride, tetramethylammonium fluoride, tetraethylammonium fluoride, tetrapropylammonium fluoride, and tetra-n-butylammonium fluoride. The fluoride can be used alone or in a mixture of two or more in any ratio. The amount of fluoride used in the reaction is preferably in the range of 0.025 to 0.50 molar times, more preferably 0.05 to 0.4 molar times, relative to the amount of the synthetic raw material (i.e., trifluoropyruvic acid fluoride dimer and/or trifluoropyruvic acid fluoride) converted into monomer. Here, the amount of the synthetic raw material converted into monomer is the amount used as is when trifluoropyruvic acid fluoride monomer is used, and is expressed by multiplying the amount used by 2 when trifluoropyruvic acid fluoride dimer is used, since it is a dimer. The amount of fluoride used in the reaction can be in the range of 0.025 to 0.50 molar times relative to trifluoropyruvic acid fluoride monomer when trifluoropyruvic acid fluoride monomer is used as the synthetic raw material. If too little is added, the reaction is slow, and if a large amount is used, it is not economical, so it is preferable to use 0.05 to 0.4 molar times. When trifluoropyruvic acid fluoride dimer is used as a synthetic raw material, the amount of fluoride can be in the range of 0.05 to 1.00 molar amounts relative to the trifluoropyruvic acid fluoride dimer, and is more preferably in the range of 0.1 to 0.8 molar amounts.
The fluoride may be added only in the reaction step, or may be further added in either one or both of the by-product decomposition step and the isomerization step, which are carried out after the reaction step. In the latter case, the amount of fluoride added in the reaction step is preferably in the range of 0.05 to 0.1 molar amounts relative to the amount of the synthesis raw material used in terms of monomer. In the case where trifluoropyruvic acid fluoride dimer is used as the synthesis raw material, the above range is synonymous with the range of 0.1 to 0.2 molar amounts of the fluoride used relative to trifluoropyruvic acid fluoride dimer. By adding the fluoride in portions in this manner, the yield of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) may be improved.
The total amount of fluoride added in the reaction step, by-product decomposition step and isomerization step is preferably 0.1 to 0.4 molar times the amount of the above-mentioned synthetic raw material used in terms of monomer. The total amount of fluoride added in the reaction step, by-product decomposition step and isomerization step means the total amount of fluoride added in these two steps when fluoride is added in the reaction step and by-product decomposition step, the total amount of fluoride added in these two steps when fluoride is added in the reaction step and isomerization step, and the total amount of fluoride added in these three steps when fluoride is added in the reaction step and by-product decomposition step.

Theoretically, the amount of hexafluoropropylene oxide used in the reaction step is preferably 1.00 molar or more relative to the trifluoropyruvic acid fluoride monomer used in the reaction, and from the viewpoint of improving the yield, it is preferably 1.03 to 1.25 molar amounts. When trifluoropyruvic acid fluoride dimer is used as the raw material, the amount of hexafluoropropylene oxide used is preferably 2.00 molar or more relative to the trifluoropyruvic acid fluoride dimer, and more preferably 2.05 to 2.50 molar amounts.

In the reaction step, the order of addition of the various components to be reacted is not particularly limited, but it is preferable to prepare a mixture of the synthesis raw materials, fluoride and organic solvent, and add hexafluoropropene oxide to this mixture. For example, a mixture of the synthesis raw materials, fluoride and organic solvent is prepared, and the mixture is adjusted to a temperature in the range of -20°C to 60°C, and hexafluoropropylene oxide is added over 0.5 to 48 hours. After the addition of hexafluoropropylene oxide, the temperature may be kept in the above range for 2 to 24 hours to complete the production of perfluoro(3,5-dimethyl-2-oxo-1,4-dioxane), which is the target product in the reaction step and an intermediate for the production of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane). The reaction step can be preferably carried out in a pressure-resistant vessel.

[By-product decomposition process]
In the above production method, after the reaction step, a by-product decomposition step is carried out in which the by-product of the reaction solution obtained by this step is decomposed. An example of the target product in the reaction step is perfluoro(3,5-dimethyl-2-oxo-1,4-dioxane) represented by the following formula 3, and the target product may be obtained as a mixture of diastereomers.

On the other hand, in the reaction process, in addition to the target product, by-products are usually also produced. For example, the compound represented by the following formula 4 can be given as an example of the by-product. In the above production method, the reaction liquid obtained in the reaction process is subjected to a by-product decomposition process before the isomerization process. This can contribute to increasing the yield of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) obtained after the isomerization process.

The by-products can be decomposed (thermolyzed) by heating. The reaction liquid obtained in the reaction step can be decomposed by heating the reaction liquid preferably to a temperature in the range of 60°C to 90°C. The heating temperature of the reaction liquid refers to the liquid temperature of the reaction liquid unless otherwise specified. The heating time is preferably 3 hours to 48 hours. In the by-product decomposition step of the present invention, the by-products can be partially or completely decomposed. In the by-product decomposition step, it is sufficient that at least a portion of the by-products is decomposed, and it is not essential that all of the by-products are decomposed.

The by-product decomposition step can be carried out in a closed or open container. Since the by-product is usually gasified by pyrolysis, the pressure in the closed container may increase as the decomposition reaction proceeds. From the viewpoint of smoothly proceeding with the decomposition reaction of the by-product, when the decomposition reaction is carried out in a closed container, it is preferable to decompress the pressure in the closed container. In one embodiment, the reaction liquid can be heated in a closed container while decompressing the pressure in the container. Here, it is preferable to control the pressure in the closed container to less than 1.0 MPa by decompression, and it is more preferable to control it to a range of 0.5 MPa to 0.9 MPa. The term "closed container" means a container that is closed to an extent that the pressure in the container can be controlled, and does not need to be completely sealed, and ventilation from the inside of the container to the outside and ventilation from the outside of the container to the inside of the container are allowed. For example, the pressure in the closed container can be decompressed by discharging gas from the inside of the closed container to the outside. In one embodiment, the reaction liquid can be heated in a closed container at a temperature of 60° C. to 90° C., cooled, and then decompressed once or multiple times. In this way, the pressure inside the closed container can be controlled to a predetermined pressure or lower. The predetermined pressure is preferably less than 1.0 MPa, and more preferably in the range of 0.5 MPa to 0.9 MPa. In such an embodiment, for example, when the reaction liquid is heated to a temperature in the range of 60°C to 90°C, the pressure inside the closed container is not released, and the pressure is released after cooling, and the reaction liquid can be heated again at a temperature in the above range without releasing the pressure. By the cooling, for example, the reaction liquid can be cooled to room temperature.
Meanwhile, the term "open vessel" refers to a vessel having an opening open to the atmosphere. When the by-product decomposition process is carried out in an open vessel, the decomposition products of the by-products are gasified and discharged to the outside of the open vessel, so that the by-products can be decomposed while preventing or suppressing a pressure increase in the vessel due to the progress of the decomposition reaction.

[Isomerization step]
In the above production method, an isomerization step is carried out after the by-product decomposition step. The isomerization step is a step of isomerizing perfluoro(3,5-dimethyl-2-oxo-1,4-dioxane) to perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane). Perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) is represented by the following formula 5, and may be obtained as a mixture of diastereomers.

In the isomerization step, the reaction liquid after the by-product decomposition step is usually heated at 100°C to 150°C for 4 to 48 hours to allow the isomerization reaction to proceed and the isomerization to be completed. The isomerization step is preferably carried out in a pressure-resistant vessel. The pressure inside the vessel in which the isomerization step is carried out is preferably in the range of 0.1 MPa to 1.0 MPa. Decomposing and removing the by-products before the isomerization step can contribute to improving the yield of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane).

After the isomerization step, for example, the mixture can be cooled to room temperature, depressurized, and then filtered and the upper organic solvent layer separated and removed to obtain the desired perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane).

The perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) obtained by the above manufacturing method can be converted to perfluoro(2-methylene-4-methyl-1,3-dioxolane) by, for example, the method of thermal decomposition in the gas phase described in U.S. Patent No. 3,308,107, or the method of converting to a potassium carboxylate salt and then thermal decomposing, described in Macromolecules 2005, 38, 4237-4245.

The present invention will be further explained below with reference to examples. However, the present invention is not limited to the embodiments shown in the examples. The temperatures described below are the liquid temperatures of the reaction liquid unless otherwise specified.

In the following analyses, the following instruments were used:
^19F -NMR: AVANCE II 400 manufactured by Bruker

1. Synthesis Example of Trifluoropyruvic Acid Fluoride Dimer 4-Methoxybenzaldehyde (1.95 kg, 14.32 mol) was charged into a 10 L SUS316 autoclave equipped with a stirrer having a pressure resistance of 8 MPa, and after cooling to 0° C. on an ice bath, hexafluoropropylene oxide (2.51 kg, 15.12 mol) was added thereto.
Next, the autoclave was sealed, and then heated to 55° C. with stirring to carry out a reaction for 3 hours, and then carried out a reaction for 8 hours at 150° C. The maximum pressures in the autoclave at 55° C. and 150° C. were 0.8 MPa and 0.7 MPa, respectively.
After the reaction was completed, the mixture was cooled to room temperature, and the upper and lower layers were separated to obtain crude trifluoropyruvic acid fluoride dimer (light yellow transparent liquid, 1.92 kg). Quantitative analysis by ^19F -NMR using benzotrifluoride as an internal standard confirmed that 1.73 kg (6.01 mol) of trifluoropyruvic acid fluoride dimer was produced (yield 84%, based on 4-methoxybenzaldehyde).

2. Examples and comparative examples of the synthesis of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane)

[Example 1]
<Reaction process>
In a 500 mL autoclave (closed vessel) made of SUS316 equipped with a stirrer with a pressure resistance of 8 MPa, the trifluoropyruvic acid fluoride dimer (140.8 g, pure content 126.9 g, 0.441 mol) prepared in 1. above, cesium fluoride (16.1 g, 0.106 mol) as a fluoride, and diethylene glycol dimethyl ether (99.3 g, 0.740 mol) were charged and cooled to 0 ° C. on an ice bath. Here, the amount of fluoride used is 0.120 molar times the amount of the synthetic raw material (trifluoropyruvic acid fluoride dimer) used in terms of monomer, and 0.240 molar times the amount of trifluoropyruvic acid fluoride dimer used. After the cooling, hexafluoropropylene oxide (158.1 g, 0.952 mol) was added over 6 hours. During this time, the temperature was kept at 0 to 10 ° C. After further aging for 4 hours at the same temperature range, a part of the reaction solution was sampled, and NMR analysis of the sampled solution confirmed that perfluoro(3,5-dimethyl-2-oxo-1,4-dioxane) was produced as two diastereomers.
^19F -NMR (neat, 376MHz)
(Isomer 1) δ -81.63, -81.78, -82.20, -82.95, -117.24, -126.28.
(Isomer 2) δ -81.63, -82.20, -82.95, -94.58, -113.72, -128.51.
In addition to the above, by-products showing at least the following signals in NMR were detected in the sampled solution.
^19F -NMR (neat, 376MHz)
δ 26.88, 26.75, 26.61, 26.52, -75.90, -76.19, -76.59, -77.04, -77.44, -79.32, -81.07, -81.32, -81.65, -83.64, -83.92, -84.32, -84.66, -85.09, -85.51, -120.43, -120.56, -120.69, -120.92, -129.75, -129.82, -129.87, -130.33.

<By-product decomposition process>
After the reaction step, the autoclave (closed vessel) was heated to 80° C. and heated for 5 hours. During this time, when the pressure reached 0.9 MPa, the gas in the vessel was partially discharged to depressurize the vessel while maintaining the pressure therein at 0.9 MPa or less. After that, the autoclave was cooled and depressurized, and a sample was taken and subjected to NMR analysis, whereby it was confirmed that the signals of the by-products had disappeared.

<Isomerization step>
After the by-product decomposition step, the autoclave was heated again to 120° C. and the isomerization reaction was carried out for 24 hours. The maximum pressure in the autoclave during this period was 0.8 MPa.
After the reaction was completed, the mixture was cooled to room temperature and separated to obtain crude perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) (light yellow liquid, 257.9 g). In the quantitative analysis by ¹⁹ F-NMR using benzotrifluoride as an internal standard, 205.4 g (0.663 mol) of the target perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was produced (yield 75%, based on trifluoropyruvic acid fluoride dimer). The target product obtained was a mixture of two diastereomers, with a molar ratio of 6/4.
^19F -NMR (neat, 376MHz) (isomer 1) δ 23.63, −77.76 (d, J=131.6Hz), −80.13, −81.57, −83.56 (d, J=135.4Hz), −124.91. (Isomer 2) δ 23.16, −78.45 (d, J = 131.6 Hz), −80.37, −81.56, −84.05 (d, J = 139.1 Hz), −123.72.

[Comparative Example 1]
The reaction step was carried out in the same manner as in Example 1, and then, without carrying out the by-product decomposition step, the isomerization step was carried out in the same manner as in Example 1. The maximum pressure during the reaction at 120° C. for 24 hours was 2.8 MPa.
After completion of the reaction, the reaction solution was analyzed in the same manner as in Example 1. It was found that 183.2 g (0.591 mol) of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was produced (yield 67%, based on trifluoromethylpyruvic acid fluoride dimer).

[Comparative Example 2]
The reaction step was carried out in the same manner as in Example 1, and then the isomerization step was carried out in the same manner as in Example 1 without carrying out the operation of the by-product decomposition step. However, in the isomerization step, when the pressure reached 0.9 MPa during the reaction at 120°C, the pressure was kept at 0.9 MPa or less while part of the pressure was released. After the reaction was completed, the reaction solution was analyzed by the same operation as in Example 1, and it was found that 77.7 g (0.251 mol) of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was produced. The yield based on trifluoropyruvic acid fluoride dimer was low at 28%.

[Example 2]
<Dimer Reaction Step>
The reaction step was carried out in the same manner as in Example 1 in a 500 mL autoclave (closed vessel) made of SUS316 and equipped with a stirrer having a pressure resistance of 8 MPa.

<By-product decomposition process>
After the reaction process, the autoclave (closed container) was heated to 80°C. When the pressure in the container reached 0.9 MPa, it was cooled to room temperature. Thereafter, the gas in the container was discharged to depressurize it to atmospheric pressure, and the container was closed and heated again to 80°C. When the pressure in the container reached 0.9 MPa, it was cooled again to room temperature, depressurized, and then reheated. That is, the maximum pressure during the series of steps was 0.9 MPa. After the total heating time at 80°C reached 5 hours, the autoclave was cooled, depressurized, sampled, and subjected to NMR analysis, and it was confirmed that the by-product signal had disappeared.

<Isomerization step>
An isomerization reaction was carried out in the same manner as in Example 1. The maximum pressure in the autoclave during the reaction was 0.8 MPa. After completion of the reaction, the reaction solution was analyzed in the same manner as in Example 1, and it was found that 207.3 g (0.669 mol) of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was produced (yield 76%, based on trifluoropyruvic acid fluoride dimer).

[Example 3]
<Dimer Reaction Step>
The reaction step was carried out in the same manner as in Example 1 in a 500 mL autoclave (closed vessel) made of SUS316 and equipped with a stirrer having a pressure resistance of 8 MPa.

<By-product decomposition process>
The upper port of the autoclave was connected to a double-tube condenser, the outlet of the condenser was open to the atmosphere, and cooling water was passed through the outer tube of the double-tube. The autoclave (open vessel) was heated to 70° C. and continued to be heated under atmospheric pressure for 12 hours.

<Isomerization step>
After the by-product decomposition step, the condenser was removed and the autoclave was closed, and then an isomerization reaction was carried out in the same manner as in Example 1. The maximum pressure in the autoclave during the reaction was 0.8 MPa. After the reaction was completed, the reaction solution was analyzed in the same manner as in Example 1, and it was found that 191.7 g (0.618 mol) of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was produced (yield 70%, based on trifluoropyruvic acid fluoride dimer).

[Example 4]
The reaction step, by-product decomposition step and isomerization step were carried out in the same manner as in Example 1, except that trifluoropyruvic acid fluoride (133.2 g, pure content 127.0 g, 0.882 mol, synthesized according to the description of U.S. Patent No. 3,308,107) was used instead of trifluoropyruvic acid fluoride dimer (140.8 g, pure content 126.9 g, 0.441 mol). Here, the amount of fluoride used was 0.120 molar times the amount of the above-mentioned synthetic raw material used in terms of monomer, in other words, the amount of trifluoropyruvic acid fluoride used. The maximum pressure in the autoclave in the isomerization step was 0.7 MPa. After completion of the reaction, the reaction mixture was analyzed in the same manner as in Example 1. It was found that 196.6 g (0.634 mol) of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was produced (yield 72%, based on trifluoropyruvic acid fluoride).

[Examples 5 to 7]
The reaction step, by-product decomposition step and isomerization step were carried out in the same manner as in Example 1 using the same apparatus as in Example 1 under the conditions shown in Table 1.
The amount of fluoride used in each example relative to the amount of synthetic raw material used is as follows:
In Example 5, the amount of fluoride used/the amount of synthesis raw material (trifluoropyruvic acid fluoride dimer) used in terms of monomer=0.090 molar amount, and the amount of fluoride used/the amount of trifluoropyruvic acid fluoride dimer used=0.181 molar amount.
In Example 6, the amount of fluoride used/the amount of synthesis raw material (trifluoropyruvic acid fluoride dimer) used in terms of monomer=0.150 molar amount, and the amount of fluoride used/the amount of trifluoropyruvic acid fluoride dimer used=0.299 molar amount.
In Example 7, the amount of fluoride used/the amount of synthesis raw material (trifluoropyruvic acid fluoride dimer) used in terms of monomer=0.120 molar amounts, and the amount of fluoride used/the amount of trifluoropyruvic acid fluoride dimer used=0.240 molar amounts.
After completion of the reaction, the reaction mixture was analyzed in the same manner as in Example 1 to determine the yield of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) (based on trifluoropyruvic acid fluoride dimer).

The above results are shown in Table 1 (Table 1-1, Table 1-2). In Table 1, "HFPO" stands for hexafluoropropylene oxide, "TFPVAF-D" stands for trifluoropyruvic acid fluoride dimer, "TFPVAF" stands for trifluoropyruvic acid fluoride, and "DEGDME" stands for diethylene glycol dimethyl ether.

From the results in Table 1, it can be confirmed that perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was produced in good yield in the examples.
Moreover, from an industrial viewpoint, it is preferable to be able to suppress a pressure rise in the isomerization step, whereas in Comparative Example 1, in which the isomerization step was carried out without carrying out the operation of the by-product decomposition step, the pressure rose significantly in the isomerization step as compared to Examples. On the other hand, in Comparative Example 2, in which the isomerization step was carried out without carrying out the by-product decomposition step and depressurization was carried out in the isomerization step, the yield of perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was significantly reduced as compared to Examples.

[Example 8]
<Reaction process>
Except for using cesium fluoride (12.0 g, 0.079 mol) and diethylene glycol dimethyl ether (74.5 g, 0.555 mol) as the fluoride, the reaction process was carried out in the same manner as in Example 1. Here, the amount of the fluoride used was 0.090 molar times the amount of the synthetic raw material (trifluoropyruvic acid fluoride dimer) used in terms of monomer, and 0.179 molar times the amount of the trifluoropyruvic acid fluoride dimer used.

<By-product decomposition process>
After the above reaction step, cesium fluoride (4.1 g, 0.027 mol) and diethylene glycol dimethyl ether (24.8 g, 0.185 mol) were further added, and the by-product decomposition step was carried out in the same manner as in Example 1. The amount of fluoride used here was 0.031 molar times the amount of the synthetic raw material (trifluoropyruvic acid fluoride dimer) used in terms of monomer, and 0.061 molar times the amount of trifluoropyruvic acid fluoride dimer used.

<Isomerization step>
After the by-product decomposition step, an isomerization reaction was carried out in the same manner as in Example 1. The maximum pressure in the autoclave during this reaction was 0.8 MPa.
After the reaction was completed, the mixture was cooled to room temperature and separated to obtain crude perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) (light yellow liquid, 263.6 g). Quantitative analysis by ^19F -NMR using benzotrifluoride as an internal standard revealed that 210.6 g (0.679 mol) of the target perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) was produced (yield 77%, based on trifluoropyruvic acid fluoride dimer).

The present invention is useful in the field of manufacturing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane), and further in the field of manufacturing perfluoro(2-methylene-4-methyl-1,3-dioxolane) obtained using perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) as a synthetic raw material.

Claims (16)

A reaction step of reacting at least one synthetic raw material selected from the group consisting of trifluoropyruvic acid fluoride dimer and trifluoropyruvic acid fluoride with hexafluoropropylene oxide in an organic solvent in the presence of a fluoride;
a by-product decomposition step of decomposing by-products in the reaction solution obtained by the reaction step;
an isomerization step after the by-product decomposition step;
having
The by-product decomposition step is carried out in a closed vessel, and includes releasing the pressure in the closed vessel, and the reaction solution is heated at a temperature of 60° C. to 90° C. in the closed vessel, cooled, and then released at least once . The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to claim 1, wherein the by-product decomposition step includes heating the reaction liquid at a temperature of 60°C to 90°C. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to claim 1 or 2 , comprising heating the reaction solution in the closed container at a temperature of 60°C to 90°C while releasing the pressure in the container. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of claims 1 to 3 , further comprising controlling the pressure in the closed container to less than 1.0 MPa by depressurizing.
Method. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of claims 1 to 4 , wherein the pressure in the closed container during the heating is less than 1.0 MPa. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of claims 1 to 5 , wherein the organic solvent is an ether-based solvent. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to claim 6 , wherein the ether solvent is diethylene glycol dimethyl ether. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of claims 1 to 7 , wherein the fluoride is an alkali metal fluoride. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to claim 8 , wherein the alkali metal fluoride is cesium fluoride. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of claims 1 to 9 , wherein the amount of fluoride used in the reaction step is 0.05 to 0.4 molar times the amount of the synthesis raw material used in terms of monomer. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of claims 1 to 10 , wherein a fluoride is further added in one or both of the by-product decomposition step and the isomerization step. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to claim 11 , wherein the amount of fluoride used in the reaction step is 0.05 to 0.1 molar amounts relative to the amount of the synthesis raw material used in terms of monomer. The total amount of fluoride added in the reaction step, the by - product decomposition step , and the isomerization step is 0.1 to 0.4 molar amounts relative to the amount of the synthesis raw material used in terms of monomers. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of claims 1 to 13 , comprising reacting trifluoropyruvic acid fluoride dimer with hexafluoropropylene oxide in an organic solvent in the presence of a fluoride in the reaction step. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to claim 13 , further comprising a dimer synthesis step of synthesizing trifluoromethylpyruvic acid fluoride dimer before the reaction step. The method for producing perfluoro(2,4-dimethyl-2-fluoroformyl-1,3-dioxolane) according to any one of claims 1 to 13, comprising reacting trifluoropyruvic acid fluoride with hexafluoropropylene oxide in an organic solvent in the presence of a fluoride in the reaction step.