A method for preparing a cyclic phosphine compound

Abstract

The application discloses a preparation method of a cyclic phosphine compound and belongs to the field of organic synthesis. The preparation method of the cyclic phosphine compound is characterized by the following steps: in an organic solvent, zero-valent iron and an amine additive are jointly used to react with R1PCl2 to prepare the cyclic phosphine compound. The application does not need to use a living metal, but the zero-valent iron and the amine additive are jointly used in the reaction process to make the cyclization reaction smoothly proceed under mild conditions; the zero-valent iron alone or the amine additive alone cannot initiate the reaction, and both are indispensable. The application can efficiently prepare the cyclic phosphine compound under conventional conditions, has high safety, low cost, and the zero-valent iron and the amine additive can be recycled to close the loop, and is suitable for industrial production.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis, and more specifically, to a method for preparing cyclic phosphine compounds. Background Technology

[0002] Cyclic phosphine compounds are important raw materials for the synthesis of phenylphosphine. Phenylphosphine can be used to synthesize photoinitiator 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide). Compared with conventional initiators, 819 has a broader and stronger absorption peak in the ultraviolet long-wave and visible light regions (extending up to 440 nm), and it can generate two free radicals upon photolysis, resulting in extremely high initiation efficiency. Cyclic phosphine compounds can also be used as flame retardants, replacing halogen-containing flame retardants, and added to styrene polymers. They can also be used as catalysts to catalyze the reaction of chlorobenzene and yellow phosphine to prepare diphenylphosphine chloride.

[0003] Currently, the main methods reported in the literature for synthesizing cyclic phosphine compounds are as follows: (1) A halogen-free flame-retardant polymer foam containing at least one oligophosphine compound was disclosed in Chinese patent application No. CN201080040589.8 dated September 10, 2010. The method for preparing cyclic phosphine is to generate it from phenyl dichlorophosphine as raw material under the conditions of tetrahydrofuran and magnesium shavings. The reaction is highly exothermic and needs to be strictly controlled.

[0004] (2) Adam N. Barrett, Callum R. Woof, Christopher A. Goult, et al., Inorganic Chemistry 2021 60 (21), 16826 reported a method for synthesizing cyclic phosphine compounds using deuterated benzene as a solvent. 0.5 equivalents of aryl dichlorophosphine were reacted with two equivalents of diisopropylphosphine hydrogen to obtain cyclic phosphine compounds. However, diisopropylphosphine hydrogen is particularly sensitive to air and moisture, making it inconvenient to use and store, and it is also expensive.

[0005] (3) A European invention patent, EP2003050873, filed on December 4, 2002, discloses a method for synthesizing cyclic organocyclic phosphine and bis(alkali metal / alkaline earth metal) oligocyclic phosphine binary compounds. Cyclic phosphine compounds were prepared by using zinc powder or sodium in a tetrahydrofuran or toluene system, respectively. Zinc powder and sodium are both easily explosive chemicals, and are expensive, with significant restrictions on their production and use, and their operation also carries considerable risks.

[0006] Current technology generally considers that cyclic phosphine formation depends on the rapid cleavage of the P-Cl bond by a strong reducing agent. Therefore, alkali metals (such as sodium and potassium), alkaline earth metals (such as magnesium), or zinc powder are typically chosen. The zinc powder route allows for direct reaction in ether solvents without the addition of amines, but the zinc powder must undergo ultrasonic or vacuum thermal activation, which is cumbersome. In the sodium route, sodium acts as a strong reducing agent, directly participating in the reaction. The product changes with the degree of sodium excess—when the amount of sodium exceeds 2.5 equivalents, the reaction shifts to the formation of bis(alkali metal) oligocyclic phosphine binary compounds, i.e., clusters. However, reducing the amount of sodium leads to insufficient reaction conversion and low product yield. Furthermore, this reaction must be carried out in the absence of air, and the sodium cannot be recycled after use, ultimately existing only as NaCl, which increases production costs for large-scale preparation.

[0007] On the other hand, alkali metals and alkaline earth metals are highly chemically reactive, readily igniting in air and reacting violently with water, even exploding, posing a serious safety threat to production facilities and operators. Furthermore, alkali metal and alkaline earth metal raw materials are expensive, resulting in high production costs. These reactions are extremely sensitive to moisture and oxygen in the system, making the operation complex, requiring sophisticated equipment, and difficult to implement industrially. Of particular concern is the high hazard of mixtures of ethers and alkali metals with strong reducing properties: strong basic metal phosphonates decompose the ether used as a solvent, forming alcohols and volatile hydrocarbons (such as ethylene). If these come into contact with oxygen, they form highly explosive peroxides. Therefore, the entire reaction process requires extremely strict control over the contact between reactants and oxygen.

[0008] Therefore, there is still a need to develop a process that does not rely on highly reactive metals such as sodium and magnesium, can selectively prepare cyclic phosphine under relatively mild and easily scaled-up conditions, and whose metals and additives can be recycled and reused, resulting in lower reaction costs. Summary of the Invention

[0009] The purpose of this invention is to provide a method for preparing cyclic phosphine compounds, in which an activation system is constructed using iron and amine additives during the reaction process, enabling the cyclization reaction to proceed smoothly under mild conditions. The technical solution adopted in this invention is as follows.

[0010] A method for preparing cyclic phosphine compounds involves contacting and reacting zero-valent iron, amine additives, and phosphine dichloride (R1PCl2) in an organic solvent to obtain (R1P). n The cyclic phosphine compounds shown; wherein the zero-valent iron and amine additives together constitute a synergistic activation system that causes dechlorination coupling and cyclization of phosphine dichloride; R1 is selected from C3-C8 cycloalkyl groups and C7-C6 cycloalkyl groups. 10 Aryl groups, C6-C 10aryl groups or C groups substituted with halogens, C1-C4 alkyl groups, C1-C4 alkoxy groups, or trifluoromethyl groups 6- C 10 Aryl, where n is an integer from 4 to 6.

[0011] Those skilled in the art generally believe that the standard electrode potential of zero-valent iron is relatively high (Fe 2+ / Fe has a voltage of approximately -0.44V, and its reducing power is weaker than zinc, and much weaker than sodium and magnesium. Its chemical reactivity is also low, insufficient to achieve dechlorination coupling of the P-Cl bond to form cyclic phosphine. However, this invention has found that when zero-valent iron and amine additives coexist, the ferrous ions generated from the reaction of the raw material with iron form ligands with the amine additives that are relatively stable and have well-defined coordination structures. This allows the reaction to proceed smoothly and directly yields cyclic phosphine compounds with high selectivity—neither requiring the water quenching post-treatment necessary for alkali metal routes nor reverting to cluster compounds.

[0012] Furthermore, the specific preparation method is as follows: Organic solvent, zero-valent iron, amine additives, and R1PCl2 are added to a reactor, the mixture is heated and reacted, then cooled and filtered. The filtrate is desolvated to obtain the target cyclic phosphine compound; the general chemical reaction formula is shown below: ; R1 is selected from C3-C8 cycloalkyl, C7-C 10 Aryl groups, C6-C 10 aryl groups or C groups substituted with halogens, C1-C4 alkyl groups, C1-C4 alkoxy groups, or trifluoromethyl groups 6- C 10 Aryl, where n is an integer from 4 to 6.

[0013] Furthermore, the reactor is selected from one of a glass flask, a tetrafluoroethylene flask, and an autoclave; the solvent is selected from one or more mixtures of acetonitrile, benzene, thiol, dichloroethane, toluene, chlorobenzene, dimethyl sulfoxide, methyl tert-butyl ether, xylene, N,N-dimethylformamide, and N-methylpyrrolidone; and the zero-valent iron is selected from at least one of iron powder, iron filings, and iron foil.

[0014] Furthermore, the molar ratio of the zero-valent iron to R1PCl2 is 1-5:1.

[0015] Furthermore, the amine additive is selected from one of triethylamine, tripropylamine, tributylamine, pyridine, 3,5-dimethylpyridine, 2,6-dimethylpyridine and 1,8-diazabicyclo[5.4.0]undec-7-ene.

[0016] Furthermore, the molar ratio of the amine additive to R1PCl2 is 1-10:1.

[0017] Furthermore, it also includes the recovery steps of zero-valent iron and amine additives: after washing the filter cake obtained by filtration, zero-valent iron is recovered by filtration or magnetic separation, and then dried and reused; alkali is added to the filtrate to adjust the pH to precipitate ferrous ions, and after filtering to remove the solids, the filtrate is separated and distilled to recover the amine additives and reused.

[0018] Furthermore, the reaction temperature is 0-150℃; the reaction time is 3-36h; and the cooling temperature is 0-80℃. Preferably, the reaction temperature is 0-130℃; and the reaction time is preferably 5-24h.

[0019] Furthermore, R1 is selected from one of cyclohexyl, phenyl, p-methylphenyl, p-methoxyphenyl, p-chlorophenyl, p-fluorophenyl, p-trifluoromethylphenyl, benzyl, and naphthyl. More preferably, it is phenyl.

[0020] Furthermore, the solvent is one or more mixtures of benzene, toluene, chlorobenzene, trimethylbenzene, and xylene.

[0021] Compared with the prior art, the advantages of this invention are: I. The zero-valent iron of the present invention coexists with amine additives and forms a synergistic activation system required for the reaction, so that the zero-valent iron with relatively low direct reduction ability and easy passivation can be used for dechlorination coupling of phosphine dichloride. At the same time, it solves the problems of conversion rate, cyclization selectivity, post-processing convenience and recyclability while avoiding the use of highly active metals.

[0022] Second, the present invention can obtain the target cyclic phosphine by cooling, filtering and desolvation after reaction, without the need for the high-activity metal quenching and multiple extraction steps commonly used in the sodium route; the operation is simple, and no sodium-containing clusters were observed as the main product in the prepared product, indicating that the zero-valent iron and amine additives of the present invention have good selectivity.

[0023] Third, the iron raw material of this invention is stable and convenient to store and transport. Excess iron can be recovered by filtration or magnetic separation, and iron ions in the system can be separated by pH adjustment through precipitation. Amine additives can be recovered by distillation. This green closed-loop recycling process is impossible to achieve with alkali metal or alkaline earth metal systems. Attached Figure Description

[0024] Figure 1 The phosphorus nuclear magnetic resonance spectrum of Example 1 ( 31 P NMR (P-NMR) image. Detailed Implementation

[0025] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0026] Example 1:

[0027] To a 250 mL three-necked flask equipped with a condenser and stirrer, 100 mL of toluene was added. Under stirring, 8.4 g (150 mmol) of iron powder was added, followed by 20.2 g (200 mmol) of triethylamine. Then, 17.9 g (100 mmol) of phenylphosphine dichloride (PhPCl2) was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 110 °C and reacted for 20 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 95.3%. 31 p-NMR (such as p-NMR) Figure 1 As shown), (PhP) n (n=4 to 6), the ratio is: (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=88:11.

[0028] Example 2:

[0029] To a 250 mL three-necked flask equipped with a condenser and stirrer, add 18.5 g (100 mmol) of cyclohexylphosphine dichloride and 100 mL of toluene. Under stirring, add 8.4 g (150 mmol) of iron powder, followed by the slow dropwise addition of 30.3 g (300 mmol) of triethylamine, controlling the temperature to not exceed 40 °C during the addition. After the addition is complete, heat the system to 100 °C and react for 24 hours. After the reaction is complete, cool to 60 °C, filter to remove the solid, and evaporate the solvent from the filtrate under reduced pressure to obtain the target cyclophosphine compound as a white solid with a yield of 82.3%. 31 P-NMR, (cyclohexylphosphine)4 (s, -66.7ppm) = 98.

[0030] Therefore, the method of the present invention is also applicable to aliphatic substituted substrates (R1 is cyclohexyl).

[0031] Example 3:

[0032] To a 250 mL autoclave equipped with a stirrer, 100 mL of toluene was added. Under stirring, 8.4 g (150 mmol) of iron powder was added, followed by 71.5 g (500 mmol) of tripropylamine. Then, 19.3 g (100 mmol) of benzylphosphine dichloride was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 130 °C and reacted for 20 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 94.1%. 31 P-NMR, (benzylphosphine) n (n=4 to 6), the ratio is: (benzylphosphine)5:(benzylphosphine)4=90:10.

[0033] Example 4:

[0034] 100 mL of chlorobenzene was added to a 250 mL three-necked flask equipped with a condenser and a stirrer. Under stirring, 8.4 g (150 mmol) of iron powder was added, followed by 27.6 g (350 mmol) of pyridine. Then, 22.9 g (100 mmol) of naphthylphosphine dichloride was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 120 °C and reacted for 18 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 91.2%. 31 P-NMR, (naphthylphosphine) n (n=4 to 6), the ratio is: (naphthylphosphine)5 (s, -27.4ppm): (naphthylphosphine)4 (s, -58.2ppm) = 80:20.

[0035] Example 5:

[0036] 100 mL of xylene was added to a 250 mL three-necked flask equipped with a condenser and a stirrer. Under stirring, 8.4 g (150 mmol) of iron powder was added, followed by 23.7 g (300 mmol) of pyridine and 24.7 g (100 mmol) of p-trifluoromethylphenyl dichloride. The temperature was controlled to not exceed 40 °C during the dropwise addition. After the addition was complete, the system was heated to 130 °C and reacted for 18 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 92.1%. 31 p-NMR (p-trifluoromethylphenylphosphine) n (n=4 to 6), the ratio is: (p-trifluoromethylphenylphosphine)5 (m, 18 to 4 ppm): (p-trifluoromethylphenylphosphine)4 (s, -49.7 ppm) = 95:5.

[0037] Example 6:

[0038] 100 mL of trimethylbenzene was added to a 250 mL three-necked flask equipped with a condenser and a stirrer. Under stirring, 8.4 g (150 mmol) of iron powder was added, followed by 40.4 g (400 mmol) of triethylamine and 19.3 g (100 mmol) of p-methylphenyl dichloride. The temperature was controlled to not exceed 40 °C during the dropwise addition. After the addition was complete, the system was heated to 125 °C and reacted for 24 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 93.7%. 31 p-NMR (p-methylphenylphosphine) n(n=4 to 6), the ratio is: (p-methylphenylphosphine)5 (m, -2 to -9 ppm): (p-methylphenylphosphine)4 (s, -46.8 ppm) = 92:8.

[0039] Example 7:

[0040] To a 250 mL three-necked flask equipped with a condenser and stirrer, 100 mL of toluene was added. Under stirring, 11.2 g (200 mmol) of iron powder was added, followed by 23.7 g (300 mmol) of pyridine. Then, 17.9 g (100 mmol) of phenylphosphine dichloride was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 110 °C and reacted for 20 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 92.8%. 31 p-NMR, (PhP) n (n=4 to 6), the ratio is: (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=89:10.

[0041] Iron powder and pyridine recovery: 40g of toluene-containing solid was obtained by filtration, dissolved in 100g of water, filtered, and the iron powder was recovered and dried to obtain 5g of iron powder with a recovery rate of 89%. Sodium hydroxide solid was added to the filtrate to adjust the pH to 13, and the solid was removed by filtration. The filtrate was then distilled separately to obtain 22g of pyridine with a content of 99%, a recovery rate of 92.5%, and a water content of 0.3%.

[0042] The results show that using pyridine instead of triethylamine as an amine additive can also efficiently prepare the target cyclic phosphine compounds, and both iron powder and pyridine can be recovered.

[0043] Example 8:

[0044] To a 250 mL three-necked flask equipped with a condenser and stirrer, 100 mL of toluene was added. Under stirring, 11.2 g (200 mmol) of iron powder was added, followed by 45.6 g (300 mmol) of 1,8-diazabicyclo[5.4.0]undec-7-ene and 17.9 g (100 mmol) of phenylphosphine dichloride. The temperature was controlled to not exceed 40 °C during the dropwise addition. After the addition was complete, the system was heated to 110 °C and reacted for 20 hours. After the reaction was completed, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid with a yield of 93.3%. 31 p-NMR, (PhP) n(n=4 to 6), the ratio is: (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=92:8.

[0045] Example 9:

[0046] To a 250 mL three-necked flask equipped with a condenser and stirrer, 100 mL of chlorobenzene was added. Under stirring, 8.4 g (150 mmol) of iron powder was added, followed by 40.4 g (400 mmol) of triethylamine. Then, 17.9 g (100 mmol) of phenylphosphine dichloride was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 110 °C and reacted for 20 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 95%. 31 p-NMR, (PhP) n (n=4 to 6), the ratio is (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=90:10.

[0047] The results show that cyclization can be successfully completed and high-content target products can be obtained by replacing toluene with chlorobenzene as the reaction solvent.

[0048] Example 10: 100 mL of DMF was added to a 250 mL three-necked flask equipped with a condenser and a stirrer. Under stirring, 11.2 g (200 mmol) of iron powder was added, followed by 31.6 g (400 mmol) of pyridine. Then, 17.9 g (100 mmol) of phenylphosphine dichloride was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 110 °C and reacted for 20 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 92.7%. 31 p-NMR, (PhP) n (n=4 to 6), the ratio is: (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=85:12.

[0049] Example 11: To a 250 mL three-necked flask equipped with a condenser and stirrer, add 20 mL of toluene and 80 mL of xylene. Under stirring, add 14 g (250 mmol) of iron powder, followed by 35.4 g (350 mmol) of triethylamine. Then, add 17.9 g (100 mmol) of phenylphosphine dichloride dropwise, controlling the temperature to not exceed 40 °C during the addition. After the addition is complete, heat the system to 110 °C and react for 20 hours. After the reaction is complete, cool to 60 °C, filter to remove the solid, and evaporate the solvent from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 90.4%. 31 p-NMR, (PhP) n (n=4 to 6), the ratio is (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=93:7.

[0050] Example 12: 100 mL of acetonitrile was added to a 250 mL autoclave with a stirrer. Then, 16.8 g (300 mmol) of iron powder, 31.6 g (400 mmol) of pyridine, and 17.9 g (100 mmol) of phenylphosphine dichloride were added under stirring. The temperature was controlled to not exceed 40 °C during the addition process. After the addition was complete, the system was heated to 110 °C and reacted for 20 hours. After the reaction was completed, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid with a yield of 90.6%. 31 p-NMR, (PhP) n (n=4 to 6), the ratio is: (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=91:9.

[0051] Example 13: To a 250 mL autoclave equipped with a stirrer, 100 mL of toluene was added. Under stirring, 8.4 g (150 mmol) of iron foil was added, followed by 40.4 g (400 mmol) of triethylamine. Then, 17.9 g (100 mmol) of phenylphosphine dichloride was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 130 °C and reacted for 24 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 90.3%. 31 p-NMR, (PhP) n (n=4 to 6), the ratio is: (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=93:7.

[0052] The results showed that the target cyclic phosphine compounds could also be prepared by using iron foil instead of iron powder as the reaction reagent. The specific surface area of ​​iron foil was smaller than that of iron powder, and the reaction rate was reduced. The reaction temperature (130℃) and reaction time (24 hours) could be appropriately increased to obtain a considerable amount of the target product.

[0053] Example 14: Using Example 7 to recover iron powder and a mixture of new iron powder: To a 250 mL autoclave equipped with a stirrer, 100 mL of toluene was added. Under stirring, 5 g (89 mmol) of recovered iron powder from Example 7 and 0.7 g (12 mmol) of fresh iron powder were added, followed by 31.6 g (400 mmol) of pyridine. Then, 17.9 g (100 mmol) of phenylphosphine dichloride was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 130 °C and reacted for 24 hours. After the reaction was complete, the system was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 91.7%. 31 p-NMR, (PhP) n (n=4 to 6), the ratio is: (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=96:4.

[0054] As can be seen from Examples 7 and 14, recycled iron powder can achieve the same effect as new iron powder.

[0055] Example 15: Using pyridine recovered in Example 7 as an amine additive: To a 250 mL autoclave equipped with a stirrer, 100 mL of toluene was added. Under stirring, 8.4 g (150 mmol) of iron powder was added, followed by 22 g (275 mmol, 99% purity, 0.3% moisture) of pyridine recovered in Example 7. Then, 17.9 g (100 mmol) of phenylphosphine dichloride was added dropwise, with the temperature controlled to not exceed 40 °C during the addition. After the addition was complete, the system was heated to 130 °C and reacted for 24 hours. After the reaction was complete, the mixture was cooled to 60 °C, the solid was removed by filtration, and the solvent was removed from the filtrate under reduced pressure to obtain the target cyclic phosphine compound as a pale yellow solid, with a yield of 89.2%. 31 p-NMR, (PhP) n (n=4 to 6), the ratio is: (PhP)5(m, -2 to -5ppm):(PhP)4(s, -48ppm)=91:8.

[0056] As can be seen from Examples 7 and 15, recycled pyridine can achieve the same effect as new pyridine.

[0057] Comparative Example 1 without amine additives: To a 250 mL autoclave with stirring, 100 mL of toluene was added. Under stirring, 28 g (500 mmol) of iron powder was added, followed by 17.9 g (100 mmol) of phenylphosphine dichloride. After the reaction was completed, the system was heated to 130 °C and reacted for 24 hours. After the reaction was completed, the system was cooled to 60 °C and a sample was taken for testing. The phenylphosphine dichloride content of the raw material was 90%, and no cyclic phosphine compounds were formed.

[0058] Comparative Example 2 without using zero-valent iron: To a 250 mL autoclave equipped with a stirrer, add 100 mL of toluene. While stirring, add 50.5 g (500 mmol) of triethylamine, followed by dropwise addition of 17.9 g (100 mmol) of phenylphosphine dichloride, controlling the temperature to not exceed 40 °C during the addition. After the addition is complete, raise the temperature to 130 °C and react for 24 hours. After the reaction is complete, cool to 60 °C and take a sample for analysis. The phenylphosphine dichloride content of the raw material was 93%, and no cyclic phosphine compounds were formed.

[0059] Comparative Examples 1 and 2 show that iron alone cannot undergo cyclization, and amine additives alone also cannot react. Highly selective cyclization can only be achieved when iron and amine additives coexist. This indicates that the ligands formed by iron and amine additives during the reaction are relatively stable complexes with well-defined coordination structures. These complexes can significantly alter the electronic structure and reactivity of the metal center, promoting the continuous forward reaction and yielding cyclic phosphine compounds with high content and yield.

[0060] Comparative Example 3 using ferric chloride: To a 250 mL autoclave equipped with a stirrer, add 100 mL of toluene. Under stirring, add 24.3 g (150 mmol) of ferric chloride, followed by 40.4 g (400 mmol) of triethylamine. Then, add 17.9 g (100 mmol) of phenylphosphine dichloride dropwise, controlling the temperature to not exceed 40 °C during the addition. After the addition is complete, raise the temperature to 130 °C and react for 24 hours. After the reaction is complete, cool to 60 °C and take a sample for analysis. The phenylphosphine dichloride content of the raw material is 90%, and no cyclic phosphine compounds are formed.

[0061] Comparative Example 4 using ferrous chloride: To a 250 mL autoclave equipped with a stirrer, add 100 mL of toluene. Then, under stirring, add 19 g (150 mmol) of ferrous chloride, followed by 50.5 g (500 mmol) of triethylamine. Next, add 17.9 g (100 mmol) of phenylphosphine dichloride dropwise, controlling the temperature to not exceed 40 °C during the addition. After the addition is complete, raise the temperature to 130 °C and react for 24 hours. After the reaction is complete, cool to 60 °C and take a sample for analysis. The phenylphosphine dichloride content of the raw material was 92%, and no cyclic phosphine compounds were formed.

[0062] As shown in Example 1 and Comparative Examples 1-4, the Fe / amine system yields a higher percentage of the target product; however, cyclic phosphine was not formed in the zero-valent iron alone, amine alone, FeCl2 / amine, FeCl3 / amine, and Cu / amine systems. These results indicate that this reaction cannot be directly deduced from the general knowledge that "iron has a certain reducing property" or "amines can activate metals."

[0063] Comparative Example 5 using copper powder: To a 250 mL autoclave equipped with a stirrer, add 100 mL of toluene. Then, while stirring, add 9.5 g (150 mmol) of copper powder, followed by 40.4 g (400 mmol) of triethylamine. Next, add 17.9 g (100 mmol) of phenylphosphine dichloride dropwise, controlling the temperature to not exceed 40 °C during the addition. After the addition is complete, raise the temperature to 130 °C and react for 24 hours. After the reaction is complete, cool to 60 °C and take a sample for analysis. The phenylphosphine dichloride content of the raw material was 91%, and no cyclic phosphine compounds were formed.

[0064] Comparative Example 6: To a 250 mL three-necked flask equipped with a condenser and a stirrer, 50 mL of tetrahydrofuran was added. Under stirring, 1.34 g (55 mmol) of magnesium powder was added, followed by the slow dropwise addition of 9.85 g (55 mmol) of phenylphosphine dichloride. The addition was exothermic and refluxed. After the addition was complete, the reaction was carried out at 30 °C for 4 hours. After the reaction was complete, 50 mL of dichloroethane was added to extract the product. The magnesium was then removed by filtration, followed by washing with a saturated sodium chloride aqueous solution. The mixture was separated, and the organic solvent was removed to obtain the target cyclic phosphine compound in 75.3% yield.

[0065] Comparative Example 7: 100 mL of toluene and 15 mL of TMEDA were added to a 500 mL Schlenk tube. After purging with nitrogen, 4 g of metallic sodium was added. The mixture was heated until the sodium melted, then cooled to 50 °C. 9.85 g of phenylphosphine dichloride (PhPCl2) was added. After purging with nitrogen, the mixture was stirred at 140 °C for 6 hours in the absence of air. After the reaction was completed, the mixture was dissolved in tetrahydrofuran. The residual metallic sodium and the generated sodium chloride were carefully filtered to remove them. Without water washing or quenching, the organic solvent was removed to obtain [Na(tmeda)3][Na5(P2Ph2)3(tmeda)3] acyclic phosphine compound with a yield of 60%.

[0066] To obtain the cyclic phosphine compound, tetrahydrofuran is added to the system after the reaction is complete. Residual metallic sodium and the generated sodium chloride are carefully filtered off. The reaction mixture is then concentrated to dryness under high vacuum conditions in the absence of oxygen. 50 mL of saturated ammonium chloride aqueous solution is added to the remaining solid, and the product is extracted with 100 mL of dichloromethane. The dichloromethane organic phase is concentrated and then dried under high vacuum to obtain a light brown to brown pentaphenylcyclopentaphosphine product in 80% yield.

[0067] As demonstrated in Example 1 and Comparative Example 7, when sodium is used as a reducing agent and the reaction is carried out under sodium excess conditions, the target cyclic phosphine compound cannot be directly obtained without water washing and quenching. To successfully obtain the cyclic phosphine compound, excess sodium must first be removed from the system, followed by post-processing steps such as water washing and quenching, extraction, and solvent removal. In contrast, the zero-valent railway line of this invention can directly obtain cyclic phosphine under mild conditions, without the need for water quenching, and does not convert to cluster compounds.

[0068] It should be noted that the specific embodiments described above are examples to more clearly illustrate the present invention. Besides the embodiments described above, the present invention may have other implementations. Any variations or modifications made based on the above description are considered equivalent technical solutions claimed in the claims of the present invention.

Claims

1. A method for preparing a cyclic phosphine compound, characterized in that: In an organic solvent, zero-valent iron, amine additives, and phosphine dichloride (R1PCl2) are contacted and reacted to obtain (R1P). n The cyclic phosphine compounds shown; wherein the zero-valent iron and amine additives together constitute a synergistic activation system that causes dechlorination coupling and cyclization of phosphine dichloride; R1 is selected from C3-C8 cycloalkyl groups and C7-C6 cycloalkyl groups. 10 Aryl groups, C6-C 10 aryl groups or C groups substituted with halogens, C1-C4 alkyl groups, C1-C4 alkoxy groups, or trifluoromethyl groups 6- C 10 Aryl, where n is an integer from 4 to 6.

2. The method for preparing a cyclic phosphine compound according to claim 1, characterized in that: The process includes the following steps: adding an organic solvent, zero-valent iron, an amine additive, and R1PCl2 to a reactor, heating and reacting, cooling, filtering, and desolvating the filtrate to obtain the target cyclic phosphine compound; the general chemical reaction formula is shown below: ； R1 is selected from C3-C8 cycloalkyl, C7-C 10 Aryl groups, C6-C 10 aryl groups or C groups substituted with halogens, C1-C4 alkyl groups, C1-C4 alkoxy groups, or trifluoromethyl groups 6- C 10 Aryl, where n is an integer from 4 to 6.

3. The method for preparing a cyclic phosphine compound according to claim 2, characterized in that: The solvent is selected from one or more mixtures of acetonitrile, benzene, thallium, dichloroethane, toluene, chlorobenzene, dimethyl sulfoxide, methyl tert-butyl ether, xylene, N,N-dimethylformamide, and N-methylpyrrolidone; the zero-valent iron is selected from at least one of iron powder, iron filings, and iron foil.

4. The method for preparing a cyclic phosphine compound according to claim 2, characterized in that: The molar ratio of zero-valent iron to R1PCl2 is 1-5:

1.

5. The method for preparing a cyclic phosphine compound according to claim 2, characterized in that: The amine additive is selected from one of triethylamine, tripropylamine, tributylamine, pyridine, 3,5-dimethylpyridine, 2,6-dimethylpyridine and 1,8-diazabicyclo[5.4.0]undec-7-ene.

6. The method for preparing a cyclic phosphine compound according to claim 2, characterized in that: The molar ratio of the amine additive to R1PCl2 is 1-10:

1.

7. The method for preparing a cyclic phosphine compound according to claim 2, characterized in that, It also includes a step for recovering zero-valent iron and amine additives: after washing the filter cake obtained by filtration, zero-valent iron is recovered by filtration or magnetic separation, dried and reused; alkali is added to the filtrate to adjust the pH to precipitate ferrous ions, the solid is removed by filtration, and the filtrate is separated and distilled to recover amine additives and reused.

8. The method for preparing a cyclic phosphine compound according to claim 2, characterized in that: The reaction temperature is 0-150℃; the reaction time is 3-36h; and the cooling temperature is 0-80℃.

9. The method for preparing a cyclic phosphine compound according to claim 2, characterized in that: R1 is selected from one of cyclohexyl, phenyl, p-methylphenyl, p-methoxyphenyl, p-chlorophenyl, p-fluorophenyl, p-trifluoromethylphenyl, benzyl, and naphthyl.

10. The method for preparing a cyclic phosphine compound according to claim 3, characterized in that: The solvent is one or a mixture of benzene, toluene, chlorobenzene, trimethylbenzene, and xylene.

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