CN114315896B - 2-(Diphenylphosphorothioate) succinate and its synthesis method and use - Google Patents

Abstract

The present invention relates to 2-(diphenylphosphorothioate) succinate and its synthesis method and application. Under the protection of nitrogen atmosphere, triethylamine is used as an acid-binding agent, diphenylphosphine chloride and 2-mercaptobutyl Diacid diester reaction to produce 2-((diphenylphosphono)thio)succinic acid diester intermediate, and then through iodine-catalyzed rearrangement reaction to produce 2-(diphenylphosphorothio)butane Diacid esters. The 2-(diphenylphosphoryl) succinate (ester) (DPS-MA) phosphorus-containing flame retardant of the present invention is more effective than the 2-(diphenylphosphoryl) succinate (DPO-MA) Phosphorus-containing flame retardants have faster char formation and better flame retardant efficiency.

Description

2-(Diphenylphosphorothioate) succinate and its synthesis method and use

technical field

The invention belongs to the chemical synthesis technology of organophosphorus flame retardants, in particular to a preparation method for industrially producing flame retardant 2-(diphenylphosphorylthio)succinate.

Background technique

2-(Diphenylphosphoryl)succinic acid and its derivatives are halogen-free and environmentally friendly phosphorus-containing flame retardants. As reactive flame retardants, they can be applied to polyester, polyamide or epoxy resin materials. The material has good flame retardant properties. For example, in 2013, Chinese patent CN 103289124 (2013) reported the application of 2-(diphenylphosphoryl)succinic acid (DPO-MA for short) in PET polyester materials; in 2017, China Patents CN 106633043 (2017) and CN 106633828 (2017) report the application of 2-(diphenylphosphoryl)succinic acid in polyamide nylon materials, document Polymers for Advanced Technologies, 2016, 27(7), 860- 871 and Chinese patent CN 110156959 (2019) reported the application of 2-(diphenylphosphoryl)succinic acid and its derivatives in epoxy resin materials. At the same time, there are mainly two types of synthetic methods for 2-(diphenylphosphoryl)succinic acid and its derivatives: 1. Using diphenylphosphine oxide as a raw material method, diphenylphosphine oxide and maleic acid (ester) 2-(diphenylphosphoryl)succinic acid and its derivatives can be obtained by direct reaction, and its representative documents include: RU 2405789, (2010); CN103289124 (2013); CN 105218789 (2016); Polymers for Advanced Technologies, 2016, 27(7), 860-871;; Tetrahedron Letters, 2007, 48(1), 51-54; EP 665237 (1995); Synlett, 2020, 31(13), 1295-1297, the reaction can use catalyst or The heating method promotes the reaction to be complete. This type of synthesis method has a high yield and is suitable for industrial production needs; 2. Using diphenylphosphine chloride as a raw material method, the synthesis method is: diphenylphosphine chloride is converted into a P-Si intermediate After solidification, react with maleic acid ester under the condition of Rh or Pd catalyst to obtain 2-(diphenylphosphoryl) succinic acid ester, and its representative documents include Organic Letters, 2009, 11(5), 1091-1094; Tetrahedron, 2009, 65(33), 6510-6518, this synthesis method has high synthesis cost and medium yield, and is not suitable for large-scale production. On the basis of the research on 2-(diphenylphosphoryl)succinic acid and its derivatives, in order to further improve the flame retardant activity of phosphorus-containing flame retardants, this patent uses 2-(diphenylphosphoryl)succinic acid The (ester) structure was optimized and improved to 2-(diphenylphosphorothio)succinic acid (ester) (DPS-MA for short). At the same time, due to the strong odor of mercaptodiphenylphosphine, easy oxidation, high price, and difficult transportation Therefore, it is meaningful to develop a new preparation process with the advantages of simple process, low experimental odor, good product purity, and low production equipment requirements.

Contents of the invention

The object of the present invention is to provide a flame retardant 2-(diphenylphosphorothioate) succinate, which has a simple process and is suitable for industrial production, and its synthesis method and application, which can improve the performance of 2-(diphenylphosphoryl) Phosphoryl)succinic acid and its derivatives have flame retardant activity.

In order to solve the above problems, the technical solution provided by the present invention is: 2-(diphenylphosphorothioate) succinate, whose characteristic structure is as follows:

Wherein R is an alkyl group, preferably methyl or ethyl.

The present invention also provides a synthetic method for 2-(diphenylphosphorothioate) succinate, comprising the following steps: under the protection of a nitrogen atmosphere, triethylamine is used as an acid-binding agent, diphenylphosphine chloride and 2 -Mercaptosuccinic acid diester reaction makes 2-((diphenylphosphono) thio) succinic acid diester intermediate, and then makes the target product 2-(diphenylthio Phosphoryl) succinate (DPS-MA), the yield can reach 69%. The above reaction is described in detail below:

The reaction synthetic route of the present invention is as follows:

The target product of the present invention, 2-(diphenylphosphorothioate)succinate (DPS-MA), can be various alkyl esters, preferably methyl ester or ethyl ester.

The present invention uses diphenylphosphine chloride to react with 2-mercaptosuccinate diester to prepare 2-((diphenylphosphono)thio)succinate diester intermediate, in order to ensure 2-mercaptosuccinate The reaction of the diester raw material is complete, and an appropriate excess of diphenylphosphine chloride is required. The preferred molar ratio of diphenylphosphine chloride to 2-mercaptosuccinic acid diester is 1.05~1.10:1.

The present invention adopts the triethylamine acid-binding agent to absorb the hydrogen chloride gas produced by the reaction, and the molar amount used is the equivalent molar number of the raw material 2-mercaptosuccinic acid diester, and triethylamine and 2-mercaptosuccinic acid diester are preferably molar The ratio is 1:1.0~1.05.

The present invention uses diphenyl phosphine chloride to react with 2-mercaptosuccinate diester to prepare 2-((diphenylphosphono)thio)succinate diester intermediate, whose raw materials and intermediates are unstable , easy to oxidize and deteriorate, the reaction needs nitrogen protection, and it is not suitable to use conventional washing treatment methods for purification. After the reaction is completed, only simple filtration is required to remove the triethylamine hydrochloride produced by the reaction, and the filtrate is decompressed to remove the solvent to obtain a crude product. This crude product is It can be used in the next step reaction, and it is advisable to prepare and use now.

Among the present invention, diphenylphosphine chloride and 2-mercaptosuccinic acid diester react solvent used can be solvents such as dichloromethane, chloroform, carbon tetrachloride, ether or toluene, because diphenyl chloride in the reaction system The presence of phosphine, prolonging the reaction time or increasing the reaction temperature will increase the formation of side reaction products, so the reaction temperature is 0~40 °C, and the reaction time is 2~6 h. For the convenience of subsequent processing, dichloromethane is preferred as the solvent. The reaction temperature is 5~30°C, and the reaction time is 3~4 h.

The 2-((diphenylphosphono)thio)succinate diester intermediate of the present invention can obtain the target product 2-(diphenylphosphorothio)succinate through an iodine-catalyzed rearrangement reaction, The dosage of the iodine catalyst is 0.2-2% of the molar number of 2-((diphenylphosphono)thio)succinic acid diester, and the preferred molar ratio is 0.5-1.0%. Since the 2-((diphenylphosphono)thio)succinic acid diester intermediate is a viscous liquid, it is not suitable to be stirred. During the reaction, a small amount of solvent can not be added to dilute the raw material, and the increase in reaction temperature is conducive to the completion of the rearrangement reaction. , The diluent is preferably a solvent with a higher boiling point such as toluene, xylene, and chlorobenzene. The temperature of the external reaction bath is 100-180°C, and the preferred temperature of the external reaction bath is 140-160°C. The reaction process can be monitored and controlled by TLC. It is enough to react until dialkyl 2-((diphenylphosphono)thio)succinate almost completely disappears, and the reaction time is about 16~24 h.

The present invention also provides the use of the 2-(diphenylphosphorothioate) succinate as a flame retardant.

Compared with prior art, the beneficial effect that the present invention has is mainly manifested in the following two aspects:

First of all, the use of iodine to catalyze the rearrangement reaction of alkylmercaptophosphine has a remarkable effect. There are three types of rearrangement catalysts reported in the literature: 1. Alkyl iodides (such as methyl iodide and ethyl iodide) are catalysts. The representative literature includes Zhurnal ObshcheiKhimii, 1992, 62(5), 1183-4; Bulletin of the Chemical Society of Japan, 1993, 66(2), 506-9; Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1991 (12), 2856-8, Such catalysts The corresponding methyl or ethyl by-products will be produced, which are not suitable for separation and purification, and are not suitable for the rearrangement reaction of the present invention; 2. Oxygen is a catalyst, and its representative literature has Izvestiya Akademii Nauk, Seriya Khimicheskaya, 1993 (8), 1441-1443; Zhurnal Obshchei Khimii, 1989, 59(7), 1679-80, experiments show that this method is not feasible, the reaction will indeed produce a small amount of rearrangement products, and the yield is not more than 30%. Under oxygen conditions, it mainly produces alkyl diphenyl sulfide Phosphonate by-products. 3. Diphenyl or dialkylphosphine chloride is used as a catalyst, and its representative documents include Zhurnal Obshchei Khimii, 1985, 55(4), 939-40; Zhurnal Obshchei Khimii, 1987, 57(8), 1919-20; Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, 1982 (4), 951-2, the synthetic method of the present invention uses diphenylphosphine chloride as a raw material, and the reaction time is prolonged or the reaction temperature is raised to 50°C, and indeed a small amount of rearrangement products have been generated, but Increase the amount of diphenylphosphine chloride by 20% and increase the reaction temperature to 150°C for a reaction time of 72 h. TLC detection revealed that the 2-((diphenylphosphono)thio)succinic acid diester intermediate was still not converted Completely, when the present invention uses iodine with a molar ratio of 1.0% as a catalyst, the reaction external bath temperature is 140-160°C, the reaction time is about 16-24 h, and the reaction raw materials almost completely disappear. It can be seen that the effect of iodine as a catalyst is obviously better.

Secondly, the target product 2-(diphenylphosphorylphosphoryl)succinate (DPS-MA) has better flame retardant efficiency than 2-(diphenylphosphorylphosphoryl)succinate (DPO-MA). The present invention uses dicyandiamide and dimethylimidazole as the epoxy e51 resin prepared by the curing agent as a template, by adding different amounts of 2-(diphenylthiophosphoryl) diethyl succinate and 2-( Diphenylphosphoryl) diethyl succinate flame retardant to prepare standard specimens of epoxy materials, and then test and compare the flame retardant efficiency of the two phosphorus-containing flame retardants. The experimental results show that: 2-(diphenylphosphoryl ) When the addition of succinate flame retardant is 15%, the UL94 flame retardant grade of epoxy material is only V-1; when the addition amount is 20%, the UL94 flame retardant grade of epoxy material reaches V-0 However, when the 2-(diphenylphosphorothioate) diethyl succinate flame retardant is added at 15%, the UL94 flame retardant grade of the epoxy material is V-0, and the added amount is reduced to At 10%, the UL94 flame retardant rating of epoxy materials can still reach or approach V-0 level, which confirms that 2-(diphenylphosphorylthio)succinic acid (ester) (DPS-MA) phosphorus-containing retardant Compared with 2-(diphenylphosphoryl)succinate (DPO-MA) phosphorus-containing flame retardants, the flame retardant has faster char formation speed and better flame retardant efficiency.

Description of drawings

Figure 1 is the ¹ H NMR spectrum of the target product of the present invention, 2-(diphenylphosphorylthio)succinate diethyl.

Detailed ways

The technical solutions of the present invention are further specifically described below through specific examples, but the present invention is not limited to these examples, and the preparation process under other conditions can be realized with reference to the methods of the following examples.

Example 1: According to the synthesis method of the document Synthetic Communications, 1980, 10(3), 175-82, 2.00 g of mercaptosuccinic acid, 20.0 mL of absolute ethanol and 3% molar equivalent of p-toluenesulfonic acid were added to a round-bottomed reaction flask Stir in medium, and react overnight under reflux in an external bath at 85°C. After most of the solvent was removed by rotary evaporation, 30 mL of ethyl acetate was added to dissolve the crude product, and then saturated sodium bicarbonate (10 mL×1) and saturated sodium chloride ( 10 mL×2) Wash until the organic phase is neutral, dry over anhydrous magnesium sulfate, filter, and rotary evaporate to obtain 2.47 g of diethyl mercaptosuccinate with a yield of 90%, which can be directly used in the next reaction.

Under nitrogen protection, 2.00 g (9.6 mmol) of the above crude product diethyl mercaptosuccinate, 1.02 g (10.0 mmol) of triethylamine and 8.0 mL of dichloromethane were added to the reaction flask, stirred in an ice bath, and slowly Add 2.24 g (10.2 mmol) chlorinated diphenylphosphine and 4.0 mL of dichloromethane mixture dropwise, the dropwise addition is completed in about 20 minutes, warm up to room temperature, continue to stir for 1~2 h, and the detection of diethyl mercaptosuccinate is almost After the reaction was complete, the reaction solution was cooled in an ice bath, quenched by adding 15 mL of 1.0 mol/L hydrochloric acid, extracted with dichloromethane (30 mL×2), and the organic phase was washed with water (10 mL×1) and saturated sodium bicarbonate ( 10 mL×1), finally washed with saturated sodium chloride (15 mL×1), the organic phase was dried over anhydrous magnesium sulfate, filtered, and rotary evaporated to obtain a crude product, the intermediate product 1.96g separated by column chromatography, the yield 51.7%. This product has poor stability and should be prepared and used now.

Take 1.20 g of the above product and put it into a sealed tube, dilute the sample with 1.0 mL of xylene, then add 10 ‰ molar equivalent of iodine, and stir overnight in an external bath at 150 °C under nitrogen atmosphere (about 16 h), and TLC detects that the reaction reaches The raw material disappeared almost completely, the reaction solution was cooled, and 40 mL of ethyl acetate was added, washed with saturated sodium bisulfite solution (10 mL×2) and sodium chloride solution (15 mL×1), and the organic phase was washed with anhydrous sodium sulfate Drying, filtration, distillation, rotary evaporation to remove the solvent, and silica gel column chromatography to obtain 1.02 g of the product with a yield of 85%. Its ¹ H NMR spectrum is shown in FIG. 1 . ¹ H NMR (400 MHz, CDCl ₃ )δ :8.06-7.92 (m, 4H), 7.56-7.44 (m, 6H), 4.29 (ddd, J = 3.2,11.2 and 14.0 Hz,1H), 4.07 (m, 2H), 3.88 (m, 2H), 3.18 (ddd, J = 6.8, 11.2 and 17.6 Hz, 1H), 2.63 (ddd, J = 3.2, 10.0 and 17.6 Hz,1H), 1.19 (t, J = 7.2 Hz , 3H), 0.85 (t, J = 7.2 Hz, 3H); HRMS (ESI) [M+H] ⁺ : calculated for C ₂₀ H ₂₄ O ₄ PS, Exact Mass:391.1133, found 391.1056.

Example 2:

Add 1.78 g (10 mmol) of dimethyl mercaptosuccinate (content >98.5%), 1.05 g (10 mmol) of dry-treated triethylamine and 10 mL of dichloromethane to a 500 mL reaction under nitrogen protection In the flask, cooled in an ice bath, slowly add a mixture of 2.66 g (12.0 mmol) of diphenylphosphorus chloride and 5.0 mL of dichloromethane dropwise through a constant pressure dropping funnel, and the dropwise addition is completed within about 10 to 15 minutes, and then the temperature is raised Reaction was carried out at 60°C for 24 h, and TLC detected that the reaction of dimethyl mercaptosuccinate was complete. After the reaction was stopped, the reaction solution was quickly filtered, and the solvent was spin-dried under reduced pressure to obtain a crude product. Transfer the crude product to a 100 mL sealed tube, dilute the product with 1.0 mL of chlorobenzene, then add 20 mg of iodine element, stir and seal under nitrogen protection, and react overnight at 140°C in an external bath. After TLC detects that the intermediate raw material has almost completely disappeared, stop the reaction (about 30 h), the reaction solution was cooled to room temperature, and 40 mL of ethyl acetate was added to extract the product, followed by saturated sodium bisulfite (10 mL×1), saturated sodium bicarbonate (10 mL×1) and saturated Sodium chloride (10 mL×1) was washed separately, the organic phase was dried with anhydrous sodium sulfate, filtered, distilled, and the solvent was removed by rotary evaporation to obtain 2.25 g of product with a yield of 62%. This product can be directly used in the synthesis of flame retardant materials.

Example 3

Under nitrogen protection conditions, 20.0 g (97 mmol) of diethyl mercaptosuccinate (content >98.5%), 9.8 g (97 mmol) of dry-treated triethylamine and 60 mL of dichloromethane were added to a 500 mL reaction In the flask, cooled in an ice bath, slowly add a mixture of 22.4 g (101 mmol) of diphenylphosphine chloride and 20 mL of dichloromethane dropwise through a constant pressure dropping funnel, and the dropwise addition is completed within about 10 to 15 minutes, and then naturally Warming up to room temperature, reacting for 3-4 h, TLC detection of diethyl mercaptosuccinate reaction is complete, stop the reaction, quickly filter the reaction solution, and spin dry the solvent under reduced pressure to obtain the crude product. Transfer the crude product to a 100 mL sealed tube, dilute the product with 15 mL of toluene, then add 0.2 g (0.9 mmol) iodine element, stir and seal under nitrogen protection, and react overnight in an external bath at 160 ° C. After TLC detects that the intermediate raw material completely disappears, Stop the reaction (about 16~24 h), cool the reaction solution to room temperature, add 100 mL of toluene to extract the product, and successively wash with saturated sodium bisulfite (20 mL×1), saturated sodium bicarbonate (20 mL×1) Wash with saturated sodium chloride (30 mL×1), dry the organic phase with anhydrous sodium sulfate, filter, distill, and rotary evaporate to remove the solvent to obtain 26.1 g of the product, with a yield of 69%. This product can be directly used in flame retardant materials Synthesizing.

Example 4: Example 4 is the preparation process of a blank sample of epoxy resin without adding a flame retardant. The preparation method is: take 16.0 g of epoxy resin e51 (81.6 mmol), 1.715 g of dicyandiamide (20.4 mmol) and 0.08 Add g dimethylimidazole (0.5% mass fraction) into a beaker, stir well until it is completely mixed, pour it into a standard mold, put it in an oven and slowly raise the temperature to 80°C, keep heating for 1 hour, and then heat at 100°C in sequence After 1 h, 120 °C heating for 1 h, 140 °C heating for 1 h, and 150 °C heating for 2 h, the required sample bar was demoulded, and the combustion test showed that it had no flame retardant grade, and the limiting oxygen index was 19.5%.

Embodiment 5: Embodiment 5 is the epoxy resin sample preparation process of adding 15% (w/w) flame retardant 2-(diphenylphosphoryl) diethyl succinate, and the preparation method is: take 16.0 g ring Oxygen resin e51 (81.6 mmol), 1.715 g of dicyandiamide (20.4 mmol) and 0.08 g of dimethylimidazole (0.5% by mass fraction) were added into a beaker, stirred well, and then 2.4 g (15% by mass Fraction) 2-(diphenylphosphoryl)diethyl succinate, continue to stir until it is completely mixed, pour it into a standard mold, put it in an oven and slowly raise the temperature to 80°C, keep heating for 1 hour, and then turn to 100°C Heating for 1 h, heating at 120°C for 1 h, heating at 140°C for 1 h, heating at 150°C for 2 h, demoulding to obtain the required sample strips, the flame retardant grade V-1 was measured by the combustion test, no melting drop phenomenon, limit oxygen Index 28.1%.

Embodiment 6: Embodiment 6 is the epoxy resin sample preparation process of adding 20% (w/w) flame retardant 2-(diphenylphosphoryl) diethyl succinate, and the preparation method is consistent with embodiment 4, The difference is that 2.4g (20% mass fraction) of 2-(diphenylphosphoryl)diethyl succinate was added, and the flame retardant grade of the prepared sample was V-0 in the combustion test, and there was no melting drop phenomenon. , The limiting oxygen index is 31.7%.

Embodiment 7: Embodiment 7 is the epoxy resin sample preparation process of adding 15% (w/w) flame retardant 2-(diphenylthiophosphoryl) diethyl succinate, and the preparation method is the same as that of Example 4 Consistent, the difference is that 2.4g (15% mass fraction) 2-(diphenylphosphorylthio)diethyl succinate was added, and the flame retardant grade of the prepared sample strip was measured as V-0 in the combustion test. There is no droplet phenomenon, and the limiting oxygen index is 30.8%.

Embodiment 8: Embodiment 8 is the epoxy resin sample preparation process of adding 10% (w/w) flame retardant 2-(diphenylthiophosphoryl) diethyl succinate, and the preparation method is the same as that of Example 4 Consistent, the difference is that adding 1.6g (10% mass fraction) of 2-(diphenylphosphorylthio)diethyl succinate, the prepared sample bar burning test shows that its flame retardancy level reaches or approaches V- Level 0, no dripping phenomenon, limiting oxygen index 29.3%.

In order to verify the advantages of the present invention, the experimental results of comparative examples 4 to 8 show that the same addition is the flame retardancy of the flame retardant 2-(diphenylthiophosphoryl) diethyl succinate of the present invention under the condition of 15%. The effect is obviously better than that of 2-(diphenylthiophosphoryl)diethyl succinate flame retardant with similar structure, and the flame retardant 2-(diphenylthiophosphoryl)succinate diethyl Ester also shows good flame retardant efficiency when the usage amount is 10%, and the flame retardant grade of its material can still reach or approach V-0 grade.

Claims (8)

1. The synthesis method of the 2- (diphenyl thiophosphoryl) succinate comprises the following steps: under the protection of nitrogen, triethylamine is used as an acid binding agent, diphenyl phosphine chloride reacts with 2-mercaptosuccinic acid diester to prepare a 2- ((diphenyl phosphono) thio) succinic acid diester intermediate, and then the target product 2- (diphenyl thiophosphoryl) succinic acid ester is prepared through an iodine-catalyzed rearrangement reaction.
2. 2. The synthesis method according to claim 1, wherein: the molar ratio of the diphenyl phosphine chloride to the 2-mercaptosuccinic acid dialkyl ester is 1.05-1.10:1.
3. 3. The synthesis method according to claim 1 or 2, characterized in that: the molar ratio of the 2-mercaptosuccinic acid diester to the triethylamine is 1:1.00-1.05.
4. 4. The synthesis method according to claim 1 or 2, characterized in that: the solvent used for the reaction of the diphenyl phosphine chloride and the 2-mercaptosuccinic acid dialkyl ester is methylene dichloride, chloroform, carbon tetrachloride, diethyl ether or toluene, the reaction temperature is 0-40 ℃, and the reaction time is 2-6 hours.
5. 5. The method of synthesis according to claim 4, wherein: the solvent used for the reaction of the diphenyl phosphine chloride and the 2-mercaptosuccinic acid dialkyl ester is methylene dichloride, the reaction temperature is 30 ℃, and the reaction time is 3-4 hours.
6. 6. The synthesis method according to claim 1, wherein: in the reaction of preparing the target product 2- (diphenylthiophosphoryl) succinic acid ester from the intermediate of the dialkyl 2- ((diphenylphosphono) thio) succinic acid through an iodine-catalyzed rearrangement reaction, the dosage of an iodine catalyst is 0.2-1.5% of the mole number of the diester 2- ((diphenylphosphono) thio) succinic acid, and the reaction temperature is 100-180 ℃.
7. 7. The synthesis method according to claim 1, wherein: in the reaction of preparing the target product 2- (diphenylthiophosphoryl) succinic acid ester from the intermediate of the dialkyl 2- ((diphenylphosphono) thio) succinic acid through an iodine-catalyzed rearrangement reaction, the dosage of an iodine catalyst is 0.5-1.0% of the mole number of the diester 2- ((diphenylphosphono) thio) succinic acid, and the reaction temperature is 140-160 ℃.
8. 8. Use of the 2- (diphenylthiophosphoryl) succinate prepared by the synthesis method of claim 1 or 2 as a flame retardant.

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