JPH11246480A - Malonic acid derivative, its production and production of fluorine-containing carboxylic acid by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To produce a new malonic acid compound capable of readily being produced at a low cost without the problem of waste material, and useful as a production raw material for a fluorine-containing carboxylic acid by introducing a specific fluoroalkyl to a specified position of malonic acid (ester). SOLUTION: This new malonic acid compound is the one of formula I [Rf is a 1-8C perfluoroalkyl; R and R' are each H or a 1-10C (un)saturated hydrocarbon], e.g. 3,3,4,4,4-pentafluorobutylmalonic acid or di(methyl or ethyl) 3,3,4,4,4- pentafluorobutylmalonate. The compound of formula I is obtained by reacting a compound of formula II with an alkali metal(halide) or an alkali metal alcoholate in a polar solvent to provide an alkali metal salt, and further reacting the obtained salt with a compound of formula III.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a novel malonic acid derivative, a method for producing the same, and a method for producing a fluorinated carboxylic acid by decomposing the compound. More specifically, the present invention relates to a novel fluorine-containing malonic acid derivative and a method for producing the same, and a method for producing a fluorine-containing carboxylic acid by decomposing the compound.

[0002]

_2. Description of the Related Art Conventionally, fluorine-containing compounds represented by the general formula (IV) RfCH ₂ CH ₂ CH ₂ CO ₂ H (IV) wherein Rf represents a perfluoroalkyl group having 1 to 8 carbon atoms. As a method for producing a carboxylic acid, a perfluoroalkyl iodide having a corresponding carbon number is reacted with a 3-butenoic acid ester to prepare a carboxylic acid.
A method of obtaining a perfluoroalkyl-3-iodobutanoate, deiodinating and reducing it with a metal, and then hydrolyzing the ester to obtain a free carboxylic acid has been reported (U. Larsson et al., Acta Chem. Scand. (1993) vol.47, N
o.4, pp380-390).

[0003] However, 3-butenoic acid ester is expensive and is not necessarily advantageous as an industrial raw material.
Further, in this reaction, since metal powder such as tin or zinc is used for deiodination reduction, there is a problem in the treatment or disposal of these metal salts after the reaction, and it is difficult to form an industrial method.

[0004]

As described above, the general formula (I
The conventional method for producing a fluorinated carboxylic acid represented by V) requires expensive raw materials, has a problem in treating and discarding a metal salt generated in the process, and is an industrial method for producing a fluorinated carboxylic acid. Is not always an excellent method.

An object of the present invention is to provide a method for producing a fluorine-containing carboxylic acid represented by the general formula (IV) using easily available and inexpensive raw materials and having no problem of waste. It is.

[0006]

Means for Solving the Problems In order to solve the above problems, the present inventors have intensively studied a method for producing a fluorinated carboxylic acid represented by the general formula (IV). As a result, a novel malonic acid derivative and a method for producing a fluorinated carboxylic acid via the malonic acid derivative have been completed.

That is, the present invention provides a compound represented by the general formula (I)

[0008]

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(Wherein, Rf represents a perfluoroalkyl group having 1 to 8 carbon atoms, R and R ′ represent H or a saturated or unsaturated hydrocarbon group having 1 to 10 carbon atoms, R's may be the same or different.)
And a malonic acid derivative represented by

[0010] The present invention also relates to a malonic acid derivative wherein Rf is a pentafluoroethyl group and R and R 'are H, methyl or ethyl in the above general formula (I).

Further, the present invention provides a compound represented by the general formula (II):

[0012]

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(Wherein, R and R ′ are the same as defined above.)
After converting the malonic acid dialkyl ester represented by the formula into an alkali metal salt, a polyfluoroalkyl iodide represented by the general formula (III) RfCH ₂ CH ₂ I (III) (wherein, Rf is the same as defined above) Reacting with a compound of the general formula (I)

[0014]

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(Wherein Rf, R and R ′ are the same as defined above).

The present invention also relates to a malonate wherein the malonic acid dialkyl ester of the formula (II) is converted to an alkali metal salt in a polar solvent in the presence of an alkali metal, an alkali metal halide or an alkali metal alcoholate. The present invention relates to a method for producing an acid derivative.

Further, the present invention provides a compound represented by the following general formula (I ′):

[0018]

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(Wherein, Rf represents a perfluoroalkyl group having 1 to 8 carbon atoms), characterized by decomposing a malonic acid derivative represented by the following general formula (IV): RfCH ₂ CH ₂ CH _{The present} invention relates to a method for producing a fluorinated carboxylic acid represented by ₂ CO ₂ H (IV) (wherein Rf is the same as defined above).

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The present invention relates to a compound of the formula (I)

[0022]

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(Wherein Rf, R and R ′ are as defined above).

In the present invention, Rf in the general formula (I) represents a perfluoroalkyl group having 1 to 8 carbon atoms, and R and R 'represent H or a hydrocarbon group having 1 to 10 carbon atoms. May be the same or different. As Rf, for example, a trifluoromethyl group, a pentafluoroethyl group, a heptafluoropropyl group, a heptafluoroisopropyl group, a nonafluorobutyl group,
A dodecafluoropentyl group, a tridecafluoropropyl group, a pentadecafluoroheptyl group, a nonadecafluorooctyl group and the like.

In the general formula (I), R and R 'represent H or a hydrocarbon group having 1 to 10 carbon atoms, which may be the same or different. Examples of R and R 'include hydrogen, methyl, ethyl, propyl, isopropyl, butyl, 1-methylpropyl, 2-methylpropyl, tert-butyl and the like.

In the general formula (I), examples of the novel malonic acid derivative satisfying the above-mentioned Rf, R and R ′ include 3,3,3-trifluoropropylmalonic acid,
Dimethyl 3,3-trifluoropropylmalonate, 3,
Diethyl 3,3-trifluoropropylmalonate, 3,
3,4,4,4-pentafluorobutylmalonic acid, 3,
Dimethyl 3,4,4,4-pentafluorobutylmalonate, diethyl 3,3,4,4,4-pentafluorobutylmalonate, 3,3,4,4,5,5,5-heptafluoropentylmalon Acid, 3,3,4,4,5,5,5-
Dimethyl heptafluoropentylmalonate, 3,3
Diethyl 4,4,5,5,5-heptafluoropentylmalonate, 3,3,4,4,5,5,6,6,6-nonafluorohexylmalonic acid, 3,3,4,4,5 , 5
Dimethyl 6,6,6-nonafluorohexylmalonate,
3,3,4,4,5,5,6,6,6-diethyl nonafluorohexylmalonate, 3,3,4,4,5,5
6,6,7,7,7-undecafluoroheptylmalonic acid, 3,3,4,4,5,5,6,6,7,7,7-undecafluoroheptylmalonate, 3,3 ,
Diethyl 4,4,5,5,6,6,7,7,7-undecafluoroheptylmalonate, 3,3,4,4,5
5,6,6,7,7,8,8,8-tridecafluorooctylmalonic acid, 3,3,4,4,5,5,6,6
Dimethyl 7,7,8,8,8-tridecafluorooctylmalonate, 3,3,4,4,5,5,6,6,7,
Diethyl 7,8,8,8-tridecafluorooctylmalonate, 3,3,4,4,5,5,6,6,7,7,
8,8,9,9,9-pentadecafluorononylmalonic acid, 3,3,4,4,5,5,6,6,7,7,8,
Dimethyl 8,9,9,9-pentadecafluorononylmalonate, 3,3,4,4,5,5,6,6,7,7,
Diethyl 8,8,9,9,9,9-pentadecafluorononylmalonate, 3,3,4,4,5,5,6,6,7,
7,8,8,9,9,10,10,10-heptadecafluorodecylmalonic acid, 3,3,4,4,5,5,6
6,7,7,8,8,9,9,10,10,10-Dimethylheptadecafluorodecylmalonate, 3,3,4
4,5,5,6,6,7,7,8,8,9,9,10,
And diethyl 10,10-heptadecafluorodecylmalonate.

Of these novel malonic acid derivatives, preferably 3,3,4,4,4-pentafluorobutylmalonic acid, dimethyl 3,3,4,4,4-pentafluorobutylmalonate, 3,3 , 4,4,4-pentafluorobutylmalonate.

The novel malonic acid derivative represented by the above-mentioned general formula (I) is prepared by mixing the alkali metal salt of a dialkyl malonate represented by the above-mentioned general formula (II) with the above-mentioned general formula (II)
It is obtained by reacting the polyfluoroalkyl iodide represented by I).

The reaction for converting the dialkyl malonate represented by the general formula (II) into an alkali metal salt is preferably carried out in a polar solvent in the presence of an alkali metal, an alkali metal halide or an alkali metal alcoholate.
For example, in a polar solvent, or disperse an alkali metal,
An alkali metal dispersion solution is prepared by reacting a part of the polar solvent with an alkali metal. The malonic acid dialkyl ester represented by the general formula (II) is dropped into this alkali metal dispersion solution to obtain a malonic acid dialkyl ester alkali metal salt. Next, a polyfluoroalkyl iodide represented by the general formula (III) is dropped and reacted on the metal salt of dialkyl malonate. Thus, the desired novel malonic acid derivative represented by the general formula (I) can be obtained.

The polar solvent used in the present invention includes alcohols, aldehydes, ketones, esters, sulfoxides, nitriles, ethers, amines, amides, and nitro compounds. Among these, preferred polar solvents are alcohols, ethers, and amides. If these polar solvents are taken as examples, as alcohols, methanol, ethanol, propanol, butanol, etc., as ethers, diglyme,
Examples include tetrahydrofuran and diethyl ether, and examples of amides include N-methylpyrrolidone and dimethylformamide. These polar solvents may be used as a mixture if necessary.

The alkali metal used in the present invention is:
Li, Na, K, etc., and the alkali metal halide is L
iH, NaH, KH and the like. Examples of the alkali metal alcoholate include lithium methoxide, lithium ethoxide, sodium methoxide, sodium ethoxide, potassium methoxide, potassium ethoxide and the like. As the alkali metal, those dispersed in commercially available liquid paraffin or the like can be used. Of these, NaH is most preferred in terms of reactivity, economy, and ease of handling.

The alkali metal dispersion is prepared by sequentially adding the alkali metal to the polar solvent with stirring. At this time, the temperature is not particularly limited, but is preferably kept at room temperature.
If the polar solvent is an alcohol, the alkali metal produces an alcoholate, which can be used as it is in the next reaction. Next, in the alkali metal dispersion solution thus adjusted,
The malonic acid dialkyl ester represented by the general formula (II) is added dropwise with stirring to react to obtain a malonic acid dialkyl ester alkali metal salt.

At this time, the reaction is preferably carried out at a temperature of -20 to 60 ° C. Preferably it is 0-30 degreeC. When the temperature is lower than −20 ° C., not only industrial difficulty is increased but also crystal precipitation may occur. On the other hand, when the temperature exceeds 60 ° C., side reactions are apt to occur, and the yield is undesirably reduced.

The dialkyl malonic acid ester to be dropped is:
1.02 to 2.0 times the molar amount of the alkali metal is appropriate. If it is less than 1.02 moles, the yield of the new malonic acid derivative will decrease, while if it exceeds 2.0 moles, unreacted dialkyl malonate will increase, which is economically disadvantageous.

The dropping time of the dialkyl malonate is preferably 1 to 5 hours. In less than one hour, it is difficult to control the reaction due to the heat generated. On the other hand, when the time exceeds 5 hours, the production efficiency of the novel malonic acid derivative deteriorates.
After completion of the dropwise addition of the dialkyl malonate, aging is preferably performed for 0.5 to 2 hours while maintaining the reaction temperature. If the time is less than 0.5 hours, the aging is insufficient, and if the time exceeds 2 hours, there is no change in the reaction result, which impairs economic efficiency.

Next, the alkali metal salt of dialkyl malonate prepared as described above is added to the above-mentioned general formula (III)
With stirring the polyfluoroalkyl iodide represented by
Drop and react.

The reaction temperature when dropping the polyfluoroalkyl iodide is from 0 to 120 ° C. More preferably, it is 20 to 100 ° C. When the reaction temperature is lower than 0 ° C., it takes a long time to complete the reaction, and when the reaction temperature is higher than 120 ° C., a side reaction occurs, which lowers the yield of the novel malonic acid derivative.

The amount of the polyfluoroalkyl iodide to be dropped may be 0.9 to 1.1 times the mol of the alkali metal salt of the dialkyl malonate. If the molar ratio is less than 0.9 times, the yield based on the alkali metal salt of dialkyl malonate decreases. If the molar ratio exceeds 1.1 times, expensive polyfluoroalkyl iodide is used more than necessary, which is economically disadvantageous. Becomes

The polyfluoroalkyl iodide represented by the general formula (III) is preferably dripped for 0.5 to 3 hours. If the time is less than 0.5 hour, it is difficult to control the reaction due to the heat generated. On the other hand, if it exceeds 3 hours, the production efficiency of the novel malonic acid derivative deteriorates. After completion of the dropping of the polyfluoroalkyl iodide, it is preferable to carry out aging for 0.5 to 2 hours while maintaining the reaction temperature. If the time is less than 0.5 hours, the aging is insufficient, and if the time exceeds 2 hours, there is no change in the reaction result, which impairs economic efficiency.

The above-mentioned series of reactions is usually carried out under an atmosphere of an inert gas such as nitrogen, argon or helium at normal pressure. Depending on the nature of the desired novel malonic acid derivative, if necessary,
The reaction can be performed under pressure. The reaction is usually performed in a batch system, but a semi-continuous system or a continuous system may be appropriately selected depending on the reaction apparatus and the production amount.

The thus obtained reaction solution containing the malonic acid derivative represented by the general formula (I) is filtered and / or washed with water, and then separated and purified by a conventional method, for example, by a distillation method. Thus, the desired high purity of the general formula (I)
Is obtained.

According to the present invention, the malonic acid derivative of the general formula (I) obtained as described above is hydrolyzed and neutralized, whereby both R and R in the general formula (I) are hydrogen. A dicarboxylic acid type malonic acid derivative represented by the general formula (I ′) can be obtained.

For example, the dicarboxylic acid-type malonic acid derivative of the general formula (I ′) is hydrolyzed as it is or after adding a water-soluble organic solvent as needed, and then adding an alkali. Thereafter, the mixture is acidified by adding a mineral acid, and the mixture is extracted with a solvent to obtain a desired dicarboxylic acid type malonic acid derivative of the general formula (I ′).

Examples of the water-soluble organic solvent that can be used include alcohols, ketones, ethers, sulfoxides, amides and the like. Examples of the alkaline solution include an aqueous solution containing 5 to 50% by weight of sodium hydroxide, potassium hydroxide, calcium hydroxide, barium hydroxide and the like. The amount of the alkali solution to be added may be an amount containing 2 to 20 moles of alkali per 1 mole of the novel malonic acid derivative. When the amount of the alkali is less than 2 times, the hydrolysis of the novel malonic acid derivative does not completely proceed, and even when the amount exceeds 20 times, the reaction rate does not change, and the economy is impaired.

The hydrolysis temperature may be from 10 to 100 ° C., preferably from 25 to 75 ° C. If the temperature is lower than 10 ° C., the reaction rate is extremely slow, and it takes a long time to complete the reaction. On the other hand, if it exceeds 100 ° C., by-products increase and the yield decreases.

The mineral acid which can be used is an aqueous solution of 0.5 to 10 N hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid or the like. Mineral acid is added until the system is an acidic solution with a pH of 4 or less. Thereafter, a solvent, for example, ethers such as diethyl ether and diisopropyl ether is added to extract a desired carboxylic acid type novel malonic acid derivative. At this time, the amount of the solvent used in one extraction operation may be 0.3 to 2.0 times the volume of the carboxylic acid type novel malonic acid derivative contained in the solution, and the number of extractions is 1 to 4 times. I just want it. If the amount of the solvent is less than 0.3 times the volume of the novel carboxylic acid type malonic acid derivative contained in the solution, the extraction efficiency is poor. It just hurts.

In the present invention, the fluorine-containing carboxylic acid represented by the general formula (IV) is obtained by thermally decomposing the dicarboxylic acid type malonic acid derivative of the general formula (I ′).

Specific examples of the fluorine-containing carboxylic acid represented by the general formula (IV) include, for example, 5,5,5-
Trifluoropentanoic acid, 5,5,6,6,6-pentafluorohexanoic acid, 5,5,6,6,7,7,7-heptafluoroheptanoic acid and the like. Of these, 5,5,6,6,6-pentafluorohexanoic acid is preferred.

The pyrolysis is carried out at a temperature of 80 with moderate stirring.
Perform at ~ 200 ° C. If the temperature is lower than 80 ° C., the rate of thermal decomposition is slow and a long decomposition time is required. Further, when the temperature exceeds 200 ° C., a side reaction proceeds, and the yield of carboxylic acid decreases,
This is not preferable because the reaction occurs rapidly.

The thermal decomposition proceeds without solvent, but a solvent may be added if necessary. As the solvent, for example, water, dimethylformamide, sulfolane and the like can be used. In this pyrolysis, if necessary, a mineral acid such as 0.1.
Hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, etc. of 1 to 10N may be added for the treatment.

The thermal decomposition time is preferably 1 to 5 hours.
If it is less than 1 hour, the reaction does not proceed sufficiently, and if it exceeds 5 hours, there is no change in the reaction result, which impairs economic efficiency.

The thermal decomposition is performed in an atmosphere of an inert gas such as nitrogen, carbon dioxide, argon, and helium. The pressure may be set at atmospheric pressure, or may be increased if necessary.

The pyrolysis solution thus obtained can be separated and purified by a conventional method, for example, by distillation to obtain a high-purity fluorinated carboxylic acid represented by the general formula (IV).

Hereinafter, the present invention will be described in more detail by way of examples, but these examples do not limit the scope of the present invention.

[0055]

Example 1 150 ml of commercially available dimethylformamide was placed in a 500 ml four-necked flask equipped with a dropping funnel, a thermometer and a stirrer. Under a nitrogen atmosphere in the system, 12.3 g of 60% sodium hydride (oil-based) was added to prepare an alkali metal dispersion. The prepared alkali metal dispersion solution was cooled to 6 ° C. using an ice bath while stirring, and 52.5 g (0.328 mol) of malonic acid diethyl ester was dropped from the dropping funnel.
Was added dropwise. The time used for the dropwise addition was 3 hours, during which the reactor was kept at 20 ° C. After the completion of dropping, the reaction temperature is set to 20 ° C.
For 1 hour to obtain diethyl malonate sodium salt. The solution is heated to 50 ° C., and 3,3,4,4,4-pentafluoro-1-
85.4 g (0.312 mol) of iodobutane was added dropwise. The time required for the dropping was 1 hour, and the temperature inside the reactor at the end of the dropping was 85 ° C. After completion of the dropwise addition, the mixture was further aged at 85 ° C. for 1 hour. Thereafter, dimethylformamide was distilled off from the reaction solution under reduced pressure, 2,000 ml of ice water was added, and the mixture was extracted twice with 200 ml of diisopropyl ether. After distilling off diisopropyl ether, vacuum distillation was performed to obtain 72.6 g.
3,3,4,4,4-pentafluoro-butylmalonic acid diethyl ester was obtained.

Mass spectrum (GC): m / z 306
(M ⁺ ) ¹ H-NMR (CDCl ₃ ): δ (ppm) 1.24-1.32 (6H, t), 2.00-2.30 (4H, m), 3.36-3.44 (1H, t),
4.17-4.29 (4H, q)

Example 2 155 ml of commercially available tetrahydrofuran was placed in a 500 ml four-necked flask equipped with a dropping funnel, a thermometer and a stirrer. Under a nitrogen atmosphere in the system, 7.5 g of 60% sodium hydride (oil-based) was added to prepare an alkali metal dispersion. While stirring the adjusted alkali metal dispersion solution,
The mixture was cooled to 6 ° C. using an ice bath, and 34.64 g (0.217 mol) of malonic acid diethyl ester was added dropwise from the dropping funnel. The time used for the dropwise addition was 3 hours, during which the reactor was kept at 20 ° C. After completion of the dropwise addition, the mixture was aged for 1 hour while maintaining the reaction temperature at 20 ° C. to obtain diethyl malonate sodium salt. This solution is heated to 50 ° C., and under stirring, 3,3,4,4,4-pentafluoro-1
-50.22 g (0.183 mol) of iodobutane was added dropwise. The time required for the dropwise addition was 1 hour, and the temperature inside the reactor at the end of the dropwise addition was 55 ° C. After completion of the dropwise addition, the mixture was further aged at 55 ° C. for 4 hours. Thereafter, dimethylformamide was distilled off from the reaction solution under reduced pressure, 800 ml of ice water was added, and the mixture was extracted twice with 80 ml of diethyl ether. After distilling off diethyl ether, vacuum distillation was performed to obtain 28.7 g of 3,3,4.
4,4-pentafluorobutylmalonic acid diethyl ester was obtained.

Example 3 A 300 ml three-necked flask equipped with a thermometer and a stirrer was charged with 2
330 g of a 0% aqueous sodium hydroxide solution was taken, and 100 g (0.327 mol) of 3,3,4,4,4-pentafluoro-butylmalonic acid diethyl ester was added with stirring. Thereafter, the mixture was heated under reflux for 2 hours. After adding 180 ml of 36% hydrochloric acid to the reaction solution, the mixture was extracted twice with 100 ml of diethyl ether. The diethyl ether layer was dried over magnesium sulfate and concentrated under reduced pressure to give a melting point of 116 to 117 ° C.
81.5 g of 3,3,4,4,4-pentafluorobutylmalonic acid was obtained.

¹ H-NMR (CDCl ₃ ): δ (ppm) 1.89-2.40 (4H, m), 3.41-3.48 (1H, t)

Example 4 In a 300 ml three-necked flask equipped with a thermometer and a stirrer,
33 g of an 8% aqueous sodium hydroxide solution and 100 ml of ethanol were taken, and 2,3,4,4,4-pentafluoro-butylmalonic acid diethyl ester 24.4 g (0.
08 mol), and the mixture was stirred at room temperature for 15 hours. Thereafter, 45 ml of 36% hydrochloric acid was added to the reaction solution, and the mixture was extracted twice with 20 ml of diethyl ether. The diethyl ether layer was dried over magnesium sulfate and concentrated under reduced pressure to obtain 10.3 g of 3,3,4,4,4-pentafluorobutylmalonic acid having a melting point of 116 to 117 ° C.

Example 5 100 g (0.40 mol) of 3,3,4,4,4-pentafluoro-butylmalonic acid was charged into a 200 ml four-necked flask equipped with a thermometer, a stirrer, and a condenser. This was heated and dissolved in an oil bath. Thereafter, the mixture is heated to 160 ° C. and stirred for 2 hours while maintaining the temperature.
78 g of pentafluorohexanoic acid were obtained.

Mass spectrum (GC): m / z 206
(M ⁺ ) ¹ H-NMR (CDCl ₃ ): δ (ppm) 1.87-2.27 (4H, m), 2.46-2.54 (2H, t)

Example 6 100 g (0.40 mol) of 3,3,4,4,4-pentafluoro-butylmalonic acid was charged into a 200 ml four-necked flask equipped with a thermometer, a stirrer, and a condenser. This was heated and dissolved in an oil bath. Thereafter, the mixture was heated to 140 ° C. and stirred for 3 hours while maintaining the temperature.
77 g of pentafluorohexanoic acid were obtained.

[0064]

According to the present invention, a novel and useful malonic acid derivative and a method for producing the same are provided. Further, according to the method of the present invention, a fluorinated carboxylic acid can be easily produced from a raw material that is industrially easily available.

Claims (5)

[Claims] 1. A compound of the general formula (I) (Wherein, Rf represents a perfluoroalkyl group having 1 to 8 carbon atoms, and R and R ′ represent H or 1 to 10 carbon atoms.)
Wherein R and R 'may be the same or different from each other. A malonic acid derivative represented by). 2. The malonic acid derivative according to claim 1, wherein in the general formula (I), Rf is a pentafluoroethyl group, and R and R ′ are H, a methyl group or an ethyl group. 3. A compound of the general formula (II) (Wherein R and R ′ represent H or a hydrocarbon group having 1 to 10 carbon atoms, and R and R ′ may be the same or different from each other). After forming a salt, a polyfluoroalkyl iodide represented by the general formula (III) RfCH ₂ CH ₂ I (III) (wherein Rf represents a perfluoroalkyl group having 1 to 8 carbon atoms) is reacted. General formula (I) characterized by the following: (Wherein, Rf, R and R ′ are the same as defined above). 4. The method according to claim 3, wherein the dialkyl malonate of the formula (II) is converted into an alkali metal salt in the presence of an alkali metal, an alkali metal halide or an alkali metal alcoholate in a polar solvent. A method for producing a malonic acid derivative. 5. A compound of the general formula (I ′) (Wherein, Rf represents a perfluoroalkyl group having 1 to 8 carbon atoms), characterized by decomposing a malonic acid derivative represented by the following general formula (IV): RfCH ₂ CH ₂ CH ₂ CO ₂ H (IV) (wherein Rf represents a perfluoroalkyl group having 1 to 8 carbon atoms).