JPS6112896B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a fluorocarboxylic acid ester. Fluorocarboxylic acid esters, represented by perfluorocarboxylic acid esters, have a variety of applications because they have low surface energy properties in addition to thermal stability, as shown in US Pat. It is also an important compound as a synthetic intermediate. Conventionally, perfluorocarboxylic acid esters are perfluorocarboxylic acids obtained by reacting alcohol with perfluorocarboxylic acid fluoride obtained by electrolytic fluorination of carboxylic acids and their derivatives, or by oxidizing perfluoroolefins. was generally produced by reacting an alcohol in the presence of a concentrated mineral acid catalyst. The former production method had the disadvantage of generating hydrogen fluoride, which was highly toxic and difficult to handle, and the latter production method also had the disadvantage of requiring heating in the presence of a considerable amount of concentrated mineral acid. . Previously, the present inventors discovered that heptafluoroisobutyric acid ester could be easily produced in one step under mild conditions using a system in which a metal fluoride was added to hexafluoropropylene and a halogenated formate, and completed the production method. has already been provided. The present inventors conducted intensive research on the method for producing perfluorocarboxylic acid esters in more detail. As a result, the fluoroketo acid esters of the present invention were deketated by heating in an aprotic solvent in the presence of a metal fluoride. The inventors have discovered that perfluorocarboxylic acid esters can be produced in good yield by causing the reaction, and have completed and provided the present invention. The raw materials used in the present invention have the general formula

A compound represented by the formula can be used regardless of its manufacturing method. Rf in the above formula is a fluorine atom or a linear or branched perfluoroalkyl group having 1 to 7 carbon atoms, preferably 1 to 3 carbon atoms, such as a trifluoromethyl group, a pentafluoroethyl group, or a heptafluoroisopropyl group. is commonly used. Moreover, R in the above formula refers to a hydrocarbon residue. That is, R in the above general formula is not particularly limited as long as it is the above-mentioned hydrocarbon residue and can be selected as necessary, but generally it is a group having 1 to 20 carbon atoms, such as a methyl group, ethyl group, isoamyl group, octyl group, or nonyl group. Preferably, 1 to 12 linear or branched alkyl groups; alkenyl groups such as allyl groups; cycloalkyl groups such as cyclohexyl groups; aralkyl groups such as phenethyl groups; and phenyl groups are suitable.
Also, one of the hydrogen atoms in these hydrocarbon residues
Groups derived by substituting one or more atoms with other atoms or atomic groups can also be suitably used. The atom or atomic group that replaces the hydrogen atom is not particularly limited, but is preferably inert under the conditions that cause the decarbonylation reaction, such as fluorine,
Preferred are atoms or atomic groups such as halogens such as chlorine and silium; esters; sulfonic acid esters; ketones, thioketones, ethers; thioethers; aldehydes. The metal fluoride used in the present invention catalyzes the deketo reaction of the fluoroketo acid ester. As the metal fluoride, fluorides of alkali metals and alkaline earth metals are known, and these known metal fluorides can be used in the present invention. Particularly suitable are alkali metal fluorides such as cesium fluoride and potassium fluoride. It is also possible to use a mixture of these metal fluorides. The reaction of the present invention can be expressed as a chemical formula as follows. That is, the fluoroketo acid ester is subjected to a deketo reaction under heating using a metal fluoride catalyst to form the corresponding carboxylic acid ester. The reaction in the present invention, that is, the ketosis removal reaction, is generally carried out in the presence of a solvent. As the solvent, diglyme, triglyme, tetraglyme, sulfolane, dimethylformamide, hexamethylphosphotriamide, dimethylsulfoxide, acetonitrile, N-methylpyrrolidone, etc. are preferable, especially in that they yield the deketotic reaction product in a good yield. In this case, glyme-based solvents are suitable. The heating conditions in the present invention vary depending on various conditions, such as the type of raw material, the type of metal fluoride, etc., and cannot be absolutely limited. For example, when cesium fluoride is used as the metal fluoride, the ketosis-removal reaction proceeds at 60°C or higher, preferably 80°C or higher, but when potassium fluoride is used, it is preferably heated to 130°C or higher. Furthermore, if the heating temperature is too high, the raw materials or reaction products may decompose, so it may be preferable not to use a too high reaction temperature. Therefore, it is preferable to determine a suitable heating temperature in advance for the reaction temperature in the present invention depending on the type of raw material, the type of metal fluoride, the properties of the reaction product, etc. The reaction temperature can generally be selected from a wide range of 60°C to 200°C when cesium fluoride is used as the metal fluoride, but it is usually 80°C to 150°C.
It is preferable to do this between Further, when using another metal fluoride as the metal fluoride, the temperature is preferably 130°C or higher. Although the pressure may be increased, normal pressure, or reduced pressure, it is operationally convenient to carry out the reaction at normal pressure. The reaction time is not particularly limited and can be selected from several minutes to several days, but generally several hours is sufficient. The type of reaction vessel is not particularly limited, and those made of glass, metal, etc. are preferably used. The above general formula

The molar ratio of the fluoroketo acid ester represented by [Formula] and the metal fluoride used as a catalyst varies depending on the structure and reactivity of the former, so it may be selected as necessary. On the other hand, it is preferable to use the metal fluoride in an amount of 0.1 to 100 mol %. Furthermore, it is a preferred embodiment to stir the reaction mixture as a means to uniformly disperse the metal fluoride during the reaction. The following examples are shown to further specifically explain the present invention, but the present invention is not limited to these examples. In addition, the reaction yield in the examples was calculated by calculating the weight of the corresponding fluorocarboxylic acid ester isolated by distillation from the reaction mixture with respect to the weight of the fluoroketo acid ester used as a raw material. Example 1 1.1g of cesium fluoride in a 30ml eggplant flask,
Heptafluoroisopropylglyogyzalic acid β-
4.5 g of ethoxyethyl and 8 ml of tetraglyme were added, and the mixture was heated and stirred on an oil bath at 100 to 115°C for 3 hours. By distilling the reaction mixture under reduced pressure, the boiling point was 36.5.
2.92 g of β-ethoxyethyl heptafluoroisobutyrate was obtained at a temperature of 6.5 mmHg. The yield was 71.5%. Example 2 The same procedure as in Example 1 was carried out, except that the fluoroketo acid ester shown in Table 1 was used instead of β-ethoxyethyl heptafluoroisopropylglyoxalate in Example 1, and the reaction conditions shown in Table 1 were used.
A product, a fluorocarboxylic acid ester, was obtained. The yield and boiling point of the isolated product were as shown in Table 1.

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Claims (1)

[Claims] 1. A fluoroketo acid ester represented by the general formula [Formula] (where Rf is a linear or branched perfluoroalkyl group or a fluorine atom; R is a hydrocarbon residue) as a metal fluoride. A method for producing a fluorocarboxylic acid ester, which comprises heating in an aprotic solvent in the presence of a fluorocarboxylic acid ester. 2 Claim 1 in which Rf in the general formula is a heptafluoroisopropyl group [(CF ₃ ) ₂ CF], a pentafluoroethyl group (CF ₃ CF ₂ ), a trifluoromethyl group (CF ₃ ), or a fluorine atom Method described. 3. The method according to claim 1, wherein R in the general formula is a linear or branched alkyl group, alkenyl group, cycloalkyl group, or phenyl group. 4. The method according to claim 1, wherein the metal fluoride is cesium fluoride or potassium fluoride. 5. The method according to claim 1, wherein the aprotic solvent is a glyme-based solvent. 6. The method according to claim 1, wherein the heating temperature is selected from the range of 60 to 200°C.