Method for purifying and reusing phosphorus compounds

Abstract

[Problem] The present invention provides a phosphorus compound refining method that makes it possible to suppress generation of a by-product during distillation. [Solution] The phosphorous compound refining method of the present invention comprises: a step for obtaining a mixture that includes a specified phosphorous compound, a specified alkenyl phosphorous compound, and a transition metal complex; and a step for obtaining a first distillate part, which includes the specified phosphorous compound, by adding a Lewis acid to the abovementioned obtained mixture and thereafter performing distillation.

Description

[Technical Field]

[0001] The present invention relates to a method for purifying phosphorus compounds, more particularly to a method for purifying phosphorus compounds by distillation, and also to a method for reusing the purified phosphorus compounds as raw materials for synthesizing alkenyl phosphorus compounds. [Background technology]

[0002] Organophosphorus compounds are chemical substances that are widely used in various products, such as flame retardants, plasticizers, insecticides, pharmaceuticals and agricultural chemicals, ligands for metal complexes, etc. In recent years, organophosphorus compounds have attracted particular attention industrially as functional materials, such as metal surface treatment agents, constituent materials for flame-retardant resins, and in the field of electronic materials.

[0003] Among organic phosphorus compounds, phosphonic acid derivatives are useful precursors of the various chemical substances mentioned above, and therefore various methods for producing them have been investigated. For example, phosphonic acid derivatives have been produced by the addition reaction of the P(O)-H bond of phosphonic acid to alkynes using a catalyst (hereinafter referred to as hydrophosphorylation reaction). For example, Patent Document 1 proposes the production of phosphonic acid derivatives using a phosphonic acid diester compound that has been partially hydrolyzed in advance as a raw material. Furthermore, Non-Patent Document 1 proposes the production of phosphonic acid derivatives using various zero-valent nickel catalysts. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] International Publication No. 2017 / 043552 [Non-patent literature]

[0005] [Non-Patent Document 1] J. AM. CHEM. SOC. 2004, 126, 5080-5081 Summary of the Invention [Problem to be solved by the invention]

[0006] However, under the reaction conditions described in Patent Document 1, during distillation purification, a mixture containing the starting phosphorus compound and the product of the hydrophosphorylation reaction is distilled under reduced pressure to obtain the starting phosphorus compound and the alkenyl phosphorus compound. The resulting starting phosphorus compound can be reused as a raw material for synthesizing the alkenyl phosphorus compound, thereby reducing raw material costs. However, a new problem has been discovered: the starting phosphorus compound undergoes a side reaction during distillation purification, resulting in the production of by-products that act as catalyst poisons. If the phosphorus compound containing these by-products is reused as a raw material for synthesizing the alkenyl phosphorus compound, the yield of the alkenyl phosphorus compound will be significantly reduced, and therefore they must be removed by purification. As a result, an additional purification step is required, which increases production costs. [Means for solving the problem]

[0007] The present inventors have conducted extensive research to solve the above problems and have found that, when a mixture containing a specific phosphorus compound, a specific alkynyl compound, and a transition metal complex is distilled, the generation of by-products that act as catalyst poisons can be suppressed by adding a Lewis acid to the mixture, thereby completing the present invention.

[0008] That is, according to the present invention, the following inventions are provided. [1] The following general formula (1): [ka] (In general formula (1), R 1 and R 2 each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aryloxy group. 1 and R 2may be bonded to each other to form a cyclic structure. a phosphorus compound represented by The following general formula (2): [ka] (In general formula (2), R 1 and R 2 is R in general formula (1) 1 and R 2 is equivalent to and a transition metal complex; adding a Lewis acid to the mixture, and then distilling the mixture to obtain a first distillate containing the phosphorus compound represented by general formula (1); A method for purifying a phosphorus compound, comprising: [2] In the first distillate, The following general formula (3): [ka] (In general formula (3), R 3 and R 4 is R in general formula (1) 1 and R 2 is synonymous with R 5 represents a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted aryl group. The purification method according to [1], wherein the content of the compound represented by the formula (I) is 0.1 mass % or less relative to the total mass of the first distillate. [3] The purification method according to [1] or [2], wherein the Lewis acid is a metal compound and / or a boron compound. [4] The purification method according to [3], wherein the metal compound is at least one selected from the group consisting of zinc compounds, iron compounds, and aluminum compounds. [5] The purification method according to [4], wherein the zinc compound is zinc chloride. [6] In the general formulas (1) and (2), R 1 and R 2and each independently represent a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryl group having 1 to 10 carbon atoms. [7] In general formula (3), R 3 , R 4 and R 5 and each independently represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted allyl group having 1 to 10 carbon atoms. [8] The purification method according to any one of [1] to [7], wherein the compound represented by general formula (1) is dimethyl phosphite. [9] The purification method according to any one of [1] to [8], wherein the compound represented by general formula (2) is dimethyl vinylphosphonate.

[10] The purification method according to [2], wherein the compound represented by general formula (3) is trimethyl phosphite.

[11] A method for recycling the phosphorus compound represented by the general formula (1) obtained by the purification method according to any one of [1] to

[10] , which is used as a raw material for synthesizing the alkenyl phosphorus compound represented by the general formula (2). [Effects of the Invention]

[0009] According to the present invention, a mixture containing a specific phosphorus compound, a specific alkenyl phosphorus compound, and a transition metal complex can be purified by distillation to recover a specific phosphorus compound that serves as a raw material for synthesizing a specific alkynyl compound while suppressing the generation of by-products that act as catalyst poisons. Furthermore, according to the present invention, the recovered specific phosphorus compound can be reused as a raw material for synthesizing a specific alkenyl phosphorus compound. DETAILED DESCRIPTION OF THE INVENTION

[0010] [Method for purifying phosphorus compounds] In the method for purifying a phosphorus compound of the present invention, first, a mixture containing a specific phosphorus compound, a specific alkenyl phosphorus compound, and a transition metal complex is obtained. The step of obtaining the mixture is preferably a step of synthesizing the specific alkenyl phosphorus compound by hydrophosphorylation of the specific phosphorus compound and acetylene in the presence of a transition metal complex as a catalyst to obtain the mixture.

[0011] Subsequently, a Lewis acid is added to the resulting mixture, followed by distillation to obtain a first distillate containing primarily phosphorus compounds. During distillation of the mixture, a second distillate containing primarily phosphorus compounds and alkenyl phosphorus compounds and a third distillate containing primarily alkenyl phosphorus compounds can be further obtained. Adding a Lewis acid to the mixture inhibits the dehydration condensation reaction of the phosphorus compounds during distillation, thereby suppressing the generation of by-products that poison the catalyst. The phosphorus compounds recovered from the first distillate can be reused as raw materials for synthesizing alkenyl phosphorus compounds.

[0012] The content of phosphorus compounds in the first distillate fraction is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on the total amount of the first distillate fraction. The content of by-products in the first distillate fraction is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and even more preferably substantially none. The mass ratio of the phosphorus compounds and alkenyl phosphorus compounds in the second distillate fraction is not particularly limited, but for example, based on the total amount of the raw material phosphorus compounds and alkenyl phosphorus compounds, preferably the raw material phosphorus compounds are less than 80% by mass and the alkenyl phosphorus compounds are 20% by mass or more, more preferably the raw material phosphorus compounds are less than 50% by mass and the alkenyl phosphorus compounds are 50% by mass or more, and even more preferably the raw material phosphorus compounds are less than 20% by mass and the alkenyl phosphorus compounds are 80% by mass or more. The content of the alkenyl phosphorus compound in the third distillate is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on the total amount of the third distillate.

[0013] The second distillate fraction obtained above can be redistilled to obtain a fourth distillate fraction mainly containing phosphorus compounds, a fifth distillate fraction mainly containing phosphorus compounds and alkenyl phosphorus compounds, and a sixth distillate fraction mainly containing alkenyl phosphorus compounds. The phosphorus compounds recovered from the fourth distillate fraction can be reused as raw materials for synthesizing alkenyl phosphorus compounds. The content of phosphorus compounds in the fourth distillate fraction is preferably 80% by mass or more, more preferably 90% by mass or more, even more preferably 95% by mass or more, and even more preferably 98% by mass or more, based on the total amount of the fourth distillate fraction. The content of by-products in the fourth distillate fraction is preferably 0.1% by mass or less, more preferably 0.01% by mass or less, and even more preferably substantially absent. The mass ratio of the phosphorus compounds and alkenyl phosphorus compounds in the fifth distillate fraction is not particularly limited, but for example, the ratio is preferably less than 80 mass% of the raw phosphorus compounds and 20 mass% or more of the alkenyl phosphorus compounds, more preferably less than 50 mass% of the raw phosphorus compounds and 50 mass% or more of the alkenyl phosphorus compounds, and even more preferably less than 20 mass% of the raw phosphorus compounds and 80 mass% or more of the alkenyl phosphorus compounds, relative to the total amount of the raw phosphorus compounds and alkenyl phosphorus compounds. The content of the alkenyl phosphorus compounds in the sixth distillate fraction is preferably 90 mass% or more, more preferably 95 mass% or more, and even more preferably 98 mass% or more, relative to the total amount of the sixth distillate fraction. In the present invention, the term "mainly comprises" refers to a content of the compounds mainly contained being 80 mass% or more.

[0014] The fifth distillate fraction obtained above can be redistilled alone or after being mixed with the second distillate fraction obtained above to recover phosphorus compounds, which can be reused as raw materials for synthesizing alkenyl phosphorus compounds.

[0015] The conditions for the distillation and redistillation are not particularly limited as long as the target compound can be distilled. For example, the distillation temperature is preferably 40 to 150°C, more preferably 60 to 120°C. The distillation time is preferably 1 to 60 hours, more preferably 8 to 24 hours. Conventionally known commercially available distillation equipment can be used as the distillation apparatus. The phosphorus compound, alkenyl phosphorus compound, and Lewis acid are described in detail below.

[0016] (phosphorus compounds) The phosphorus compound contained in the mixture is represented by the following general formula (1). [ka] (In general formula (1), R 1 and R 2 each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aryloxy group. 1 and R 2 may be bonded to each other to form a cyclic structure.

[0017] In general formula (1), R 1 and R 2 The number of carbon atoms in the alkyl group, alkoxy group, cycloalkyl group, aralkyl group, aryl group, and aryloxy group is preferably 1 to 10. The number of carbon atoms does not include the number of carbon atoms in the substituent. For example, R 1 and R 2 Examples of the alkyl group include alkyl groups such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, sec-butyl, pentyl, and hexyl groups, alkoxy groups such as methoxy, ethoxy, and butoxy groups, cycloalkyl groups such as cyclohexyl groups, aralkyl groups such as benzyl and phenethyl groups, aryl groups such as phenyl, tolyl, xylyl, and naphthyl groups, and aryloxy groups such as phenoxy groups. 1 and R 2is preferably each independently a substituted or unsubstituted alkoxy group.

[0018] In general formula (1), R 1 and R 2 Examples of the substituent that may be included include an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkoxy group, a heterocyclic group, an alkylidene group, a silyl group, an acyl group, an acyloxy group, a carboxy group, a cyano group, a nitro group, a hydroxy group, a mercapto group, and an oxo group. The number of carbon atoms contained in the substituent is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 3.

[0019] (Alkenyl phosphorus compounds) The alkenyl phosphorus compound contained in the mixture is represented by the following general formula (2). [ka] (In general formula (2), R 1 and R 2 is R in general formula (1) 1 and R 2 is equivalent to Also, R 1 and R 2 The preferred embodiments are as described above.

[0020] (Hydrophosphorylation reaction) The alkenyl phosphorus compound represented by the general formula (2) can be obtained, for example, by a hydrophosphorylation reaction of the phosphorus compound represented by the general formula (1). Specifically, the alkenyl phosphorus compound can be synthesized by subjecting the raw materials, a phosphorus compound and acetylene, to a hydrophosphorylation reaction in the presence of a transition metal complex as a catalyst.

[0021] The molar ratio of the phosphorus compound represented by general formula (1) and the alkynyl compound represented by general formula (3), which are raw materials for the hydrophosphorylation reaction, is preferably 0.01 to 1000, more preferably 0.1 to 100, and even more preferably 1 to 15, when the molar amount of the raw material phosphorus compound is taken as 1.

[0022] (Transition metal complex (catalyst)) The catalyst used in the hydrophosphorylation reaction may be a transition metal complex, such as a nickel complex, preferably a zero-valent nickel complex.

[0023] The nickel complex is preferably a nickel complex of nickel and a phosphine. The phosphines are preferably phosphines having an aliphatic or aromatic substituent. Examples of phosphines having an aliphatic substituent include trimethylphosphine, tributylphosphine, and trioctylphosphine. Examples of phosphines having an aromatic substituent include triphenylphosphine, 1,2-bis(diphenylphosphino)ethane, 1,3-bis(diphenylphosphino)propane, 1,4-bis(diphenylphosphino)butane, diphenylmethylphosphine, tris(2-methylphenyl)phosphine, tris(3-methylphenyl)phosphine, tris(4-methylphenyl)phosphine, and tris(4-methoxyphenyl)phosphine. Phosphines having an aliphatic substituent can significantly improve the reaction rate between the starting phosphorus compound and alkenyl compound. Phosphines having an aromatic substituent are inexpensive and easy to handle in air, thereby reducing production costs and improving production efficiency.

[0024] (Reaction conditions) The amount of the transition metal complex (catalyst) used in the hydrophosphorylation reaction is not particularly limited as long as the reaction proceeds sufficiently, but is preferably 0.01 to 10 mol, more preferably 0.1 to 5.0 mol, and even more preferably 0.5 to 2.0 mol per 1 mol of the phosphorus compound as the raw material.

[0025] The reaction temperature for the hydrophosphorylation reaction is not particularly limited, but in consideration of the reaction efficiency, reaction rate, and by-products, it is preferably −20 to 60° C., more preferably −15 to 40° C., and even more preferably −10 to 10° C. If the reaction temperature is within the above range, the reaction rate of the hydrophosphorylation reaction can be improved, and the conversion rate of the raw material phosphorus compound to the alkenyl phosphorus compound can be improved.

[0026] The reaction time for the hydrophosphorylation reaction is not particularly limited, but taking into consideration the reaction efficiency, reaction rate, and by-products, it is preferably 30 to 1,000 minutes, more preferably 60 to 900 minutes, and even more preferably 120 to 800 minutes. If the reaction time is within the above range, the hydrophosphorylation reaction can proceed sufficiently, and the conversion rate of the raw material phosphorus compound to the alkenyl phosphorus compound can be improved.

[0027] The hydrophosphorylation reaction may be carried out in either an organic solvent or without a solvent, but is preferably carried out without a solvent. The hydrophosphorylation reaction can be carried out by using a solvent-free method and gentle heating. By using a solvent-free method, the solvent removal step after completion of the reaction can be omitted, thereby reducing production costs. The organic solvent is not particularly limited, and examples thereof include aromatic hydrocarbons, other hydrocarbons, alcohols, ethers, ketones, esters, etc.

[0028] Taking into consideration the reaction efficiency, reaction rate, and by-products, the hydrophosphorylation reaction is preferably carried out under an inert gas atmosphere, preferably nitrogen, argon, or the like.

[0029] The conversion rate from phosphorus compounds to alkenyl phosphorus compounds in the hydrophosphorylation reaction is preferably 60% or more, more preferably 70% or more, even more preferably 75% or more, and even more preferably 80% or more. The "conversion rate (%)" in the present invention can be determined by calculating the rate of decrease in the amount of the raw material phosphorus compound at the end of the reaction based on the amount of the raw material phosphorus compound at the start of the reaction. The conversion rate of the reaction can be measured by identifying each component using GC-FID. If the conversion rate from phosphorus compounds to alkenyl phosphorus compounds is equal to or greater than the above-mentioned value, the raw materials can be used efficiently, production costs can be reduced, and production efficiency can be improved.

[0030] (Lewis acid) The Lewis acid contained in the mixture can be a metal compound and / or a boron compound. Examples of metal compounds include zinc compounds, iron compounds, and aluminum compounds. Zinc chloride, zinc bromide, and iron(II) chloride are preferred, with zinc chloride being more preferred. Examples of boron compounds include borane, borane-tetrahydrofuran complex, borane-dimethyl sulfide complex, borane-diethyl ether complex, trifluoroborane, trifluoroborane-diethyl ether complex, trifluoroborane-tetrahydrofuran complex, and triphenylborane. Borane-tetrahydro complex, borane-diethyl ether complex, and trifluoroborane are preferred. These Lewis acids can be used alone or in combination. Adding a Lewis acid to the mixture followed by distillation can suppress decomposition of the phosphorus compound represented by general formula (1) and the generation of by-products.

[0031] (by-product) During distillation of the mixture, a compound represented by the following general formula (3) may be generated as a by-product. [ka] (In general formula (3), R 3 and R 4 is R in general formula (1)1 and R 2 is synonymous with R 5 represents a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted aryl group. Also, R 3 and R 4 For preferred embodiments of R 1 and R 2 This is the same as the preferred embodiment of the above.

[0032] In general formula (3), R 5 The number of carbon atoms in the alkoxy group or aryloxy group is preferably 1 to 10. The number of carbon atoms in the substituent is not included in the number of carbon atoms. For example, R 3 and R 4 Examples of the alkyl group include alkoxy groups such as methoxy, ethoxy, and butoxy groups, and aryloxy groups such as phenoxy groups. 1 and R 2 is preferably each independently a substituted or unsubstituted alkoxy group.

[0033] In general formula (1), R 5 Examples of the substituent that may be included include an alkyl group, a cycloalkyl group, an alkoxy group, a cycloalkoxy group, a heterocyclic group, an alkylidene group, a silyl group, an acyl group, an acyloxy group, a carboxy group, a cyano group, a nitro group, a hydroxy group, a mercapto group, and an oxo group. The number of carbon atoms contained in the substituent is preferably 1 to 6, more preferably 1 to 4, and even more preferably 1 to 3.

[0034] The mechanism by which by-products are generated during distillation is explained using the following chemical formula when dimethyl phosphite ((MeO)2P(O)H) is used as the phosphorus compound represented by the above general formula (1). During distillation, methanol is produced by decomposition of dimethyl phosphite. The produced methanol and the tautomer of dimethyl phosphite ((MeO)2POH) undergo a dehydration condensation reaction, producing trimethyl phosphite as a by-product. In the present invention, it is believed that the dehydration condensation reaction can be inhibited by performing distillation after adding a Lewis acid. However, the following mechanism is speculative, and the present invention is not limited by the following mechanism. [ka]

[0035] (How to reuse) According to the recycling method of the present invention, the phosphorus compound represented by the general formula (1) obtained by the above purification method can be used as a synthetic raw material for the hydrophosphorylation reaction of the alkenyl phosphorus compound represented by the general formula (2). Since the phosphorus compound represented by the general formula (1) obtained by the above purification method has an extremely low content of the by-products that act as catalyst poisons, the hydrophosphorylation reaction can proceed efficiently without being inhibited, thereby improving the yield of the alkenyl phosphorus compound. [Example]

[0036] The present invention will be specifically explained below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0037] [Example 1] 420 g of dimethyl phosphite was charged into a 1 L autoclave reactor, cooled to 0°C, and degassed under reduced pressure. Next, 7.25 mL of a THF solution of Ni(PMe3)4 (concentration: 0.25 mol / L) was added and stirred for 15 minutes. Acetylene was supplied to the reaction system at a supply pressure of 0.02 MPa, and the reaction was continued while maintaining the internal temperature and stirring conditions until acetylene absorption was no longer observed. After 9 hours of reaction, a reaction mixture containing dimethyl vinylphosphonate was obtained with a conversion of 71.3% and a selectivity of 91.2%.

[0038] Next, zinc chloride was added as a Lewis acid to the resulting reaction mixture in an amount of 4.0% by mass relative to the total mass of the reaction mixture. Vacuum distillation was then performed at a reduced pressure of 1.0 kPa to obtain a first distillate containing primarily dimethyl phosphite, a second distillate containing primarily dimethyl phosphite and dimethyl vinylphosphonate, and a third distillate containing primarily dimethyl vinylphosphonate. The dimethyl phosphite content was 98.6% by mass relative to the total amount of the first distillate, and the trimethyl phosphite content was below the detection limit (0.1% by mass or less). Furthermore, the dimethyl phosphite content was 30% by mass relative to the total amount of dimethyl phosphite and dimethyl vinylphosphonate in the second distillate, and the dimethyl vinylphosphonate content was 70% by mass. The dimethyl phosphite content was measured by GC-FID.

[0039] Next, 4% zinc chloride was added to the resulting mixture of the second distillate fraction, and redistillation was carried out under reduced pressure of 1.0 kPa to obtain a fourth distillate fraction containing dimethyl phosphite, a fifth distillate fraction containing mainly dimethyl phosphite and dimethyl vinylphosphonate, and a sixth distillate fraction containing dimethyl vinylphosphonate. Through these distillation and redistillation procedures, dimethyl phosphite was recovered from the first and fourth distillates. The recovered dimethyl phosphite can be reused as a raw material for synthesizing dimethyl vinylphosphonate. Furthermore, redistillation of the fifth distillate fraction allows the recovery of dimethyl phosphite and dimethyl vinylphosphonate. The dimethyl phosphite recovered from the fifth distillate fraction can also be reused as a raw material for synthesizing dimethyl vinylphosphonate.

[0040] [Comparative Example 1] Except for not adding zinc chloride as a Lewis acid to the reaction mixture, distillation and redistillation were carried out in the same manner as in Example 1. Based on the total amount of the first distillate, the content of dimethyl phosphite was 95.3 mass% and the content of trimethyl phosphite was 3.3 mass%.

[0041] The results of Example 1 and Comparative Example 1 are listed in Table 1. [Table 1]

Claims

1. The following general formula (1): 【Chemistry 1】 （１） (In general formula (1), R １ and R ２ each independently represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted aryloxy group. １ and R ２ may be bonded to each other to form a cyclic structure.) a phosphorus compound represented by the formula: The following general formula (2): 【Chemistry 2】 （２） (In general formula (2), R １ and R ２ represents R in general formula (1). １ and R ２ is synonymous with and a transition metal complex; adding a Lewis acid to the mixture, and then distilling the mixture to obtain a first distillate containing the phosphorus compound represented by general formula (1); A method for purifying a phosphorus compound, comprising:

2. In the first distillate fraction: The following general formula (3): 【Transformation 3】 （３） (In general formula (3), R ３ and R ４ represents R in general formula (1). １ and R ２ is synonymous with R ５ represents a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted aryl group. The purification method according to claim 1, wherein the content of the compound represented by the formula (I) is 0.1 mass% or less based on the total mass of the first distillate.

3. 3. The purification method according to claim 1, wherein the Lewis acid is a metal compound.

4. 4. The purification method according to claim 3, wherein the metal compound is at least one selected from the group consisting of a zinc compound, an iron compound, and an aluminum compound.

5. 5. The purification method according to claim 4, wherein the zinc compound is zinc chloride.

6. 3. The purification method according to claim 1, wherein the Lewis acid is a boron compound.

7. In general formulas (1) and (2), R １ and R ２ and each independently represent a substituted or unsubstituted alkoxy group or a substituted or unsubstituted aryl group having 1 to 10 carbon atoms.

8. In general formula (3), R ３ , R ４ and R ５ and each independently represent a substituted or unsubstituted alkoxy group, a substituted or unsubstituted aryloxy group, or a substituted or unsubstituted allyl group having 1 to 10 carbon atoms.

9. The purification method according to any one of claims 1 to 8, wherein the compound represented by general formula (1) is dimethyl phosphite.

10. The purification method according to any one of claims 1 to 9, wherein the compound represented by general formula (2) is dimethyl vinylphosphonate.

11. 3. The purification method according to claim 2, wherein the compound represented by general formula (3) is trimethyl phosphite.

12. A recycling method comprising a step of obtaining a phosphorus compound represented by general formula (1) by the purification method according to any one of claims 1 to 11, and using the obtained phosphorus compound represented by general formula (1) as a raw material for synthesizing an alkenyl phosphorus compound represented by general formula (2).

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