Preparation method of a bis-DOPO compound

Abstract

The present invention relates to a preparation method of a bis-DOPO compound, comprising the following steps: (S1) DOPO and acetophenone react for 2-4 h in the presence of an acidic catalyst and at a temperature of 120-140 °C; (S2) the system is cooled to 10-20 °C, CDOP is added, and the reaction is carried out for 1-2 h under the condition of a metal chloride as a catalyst; (S3) an Arbuzov catalyst and an amide compound are added, and the reaction is carried out for 4-6 h at a temperature of 100-120 °C to obtain the product compound DiDOPO-A. By using an Arbuzov catalyst as a catalyst and an amide compound as a co-catalyst, the present invention can reduce the rearrangement reaction temperature to 90-120 °C, so that an enamel reaction kettle can be used as a reaction device, solving the problem that using CDOP as a raw material can improve the yield but is liable to corrode the reaction device.

Description

Technical Field

[0001] The present invention belongs to the technical field of the preparation of DOPO flame retardants, and particularly relates to a method for preparing a bis-DOPO compound. Background Art

[0002] 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is a novel halogen-free flame retardant. It contains a P-H bond and can react with alkenyl, epoxy, and carbonyl groups, and can be used to prepare a variety of DOPO-based derivatives. There are reports in the prior art that two or more DOPOs are connected by a bridging method to prepare bis-DOPO derivatives with excellent flame retardant properties as flame retardants.

[0003] Among them, DiDOPO-A is an important bis-DOPO compound, and there are many literature reports on its preparation method. The structural formula of DiDOPO-A is shown as the following formula (I):

[0004] (I)

[0005] This compound was first reported in Japanese Patent JPH11-106619 and was prepared from DOPO and dihydric alcohols or dihalohydrocarbons. For another example, CN104086593A reported a preparation method of DiDOPO-A. It reacts acetophenone with DOPO in the presence of an acidic catalyst. The P-H of the DOPO compound reacts with the carbonyl group of acetophenone to produce a phosphate ester, which is then nucleophilically substituted by HX (X = Br, Cl) to prepare a halogenated phosphate ester. The halogenated phosphate ester is obtained by an elimination reaction to obtain a vinyl group-containing phosphate ester, and the vinyl group-containing phosphate ester reacts with another molecule of DOPO to obtain a bridged bis-DOPO compound. Specifically, it is the content recorded in Example 1 thereof: DOPO (86.40 g, 0.40 mol), acetophenone (24.05 g, 0.20 mol) and 10 mL of xylene were added to a three-necked flask equipped with a thermometer, a water separator, a magnetic stirrer and a constant pressure funnel. Under nitrogen protection, the mixture was heated to 154 °C, and phosphorus oxychloride was started to be added dropwise. POCl3 (30.25 g) was slowly added dropwise to the reaction solution within 25 hours, and the distillate was collected in the water separator while maintaining the reaction temperature at 154-160 °C. After the addition of phosphorus oxychloride was completed, the temperature was kept for half an hour. After cooling, 120 g of isopropanol was added, and the mixture was stirred under reflux. Most of the crude product dissolved after softening, and the system became turbid. Stirring was stopped and the mixture was cooled. After standing for a period of time, a large amount of the product precipitated. After filtration, the solid product was first washed with a small amount of isopropanol, the filtrate was collected, and then washed three times with an appropriate amount of deionized water. The product was a white solid powder, which was collected and dried at 110 °C for 13 h to obtain 89 g of the product, and the yield was 83.2%. However, the inventors could not repeat it according to the conditions recorded in this patent, and the yield was only about 60%. The inventors believe that this patent hides the key process steps, or the actual yield is not as high as claimed in this patent.

[0006] CN110885344A discloses a preparation method of a DOPO vinylidene bridged derivative, and its synthetic route is as follows:

[0007] ;

[0008] This patent uses cyclic carbonate as a raw material for the reaction, but the final yield is not high.

[0009] CN103408594A discloses a preparation method of a high-purity DOPO derivative, which also involves the Arbuzov rearrangement reaction. It adds a certain content of an acid-binding agent, such as triethylamine. This patent states that adding an acid-binding agent can lower the reaction temperature and complete the reaction at 120 °C. However, an equimolar amount or an excessive amount of the acid-binding agent is required, and the cost is relatively high. Moreover, the yield of this patent is calculated based on ethylene glycol. In fact, other products may also be obtained when ethylene glycol participates in the reaction, and the actual yield of the bis-DOPO used in this patent is even lower.

[0010] The previous patent CN112125930A of the inventor disclosed a preparation method of an aryl bis-DOPO compound, using the compounding of methyl benzenesulfonate and heteropolyacid as a catalyst to reduce the reaction temperature to 140-160°C. However, the presence of heteropolyacid will also cause certain corrosion to the equipment. Moreover, due to calculation errors at that time and insufficient product purification, the yield of this patent actually cannot reach as high as claimed in the patent.

[0011] Due to the excellent flame retardant properties of this DiDOPO-A compound, it has attracted the attention of researchers. However, the yield of the current preparation method and the prospect of industrial production still need to be improved, and a preparation method with simple process and high yield needs to be developed. Summary of the Invention

[0012] In order to solve the defects of the complex preparation process and unsatisfactory yield of the DiDOPO-A compound. The present invention provides a preparation method of the DiDOPO-A compound. The first step is consistent with the literature record, which is the reaction of DOPO and acetophenone. Since then, the synthesis route has been changed. CDOP is used as the raw material for introducing the second molecule of DOPO, and then the product DiDOPO-A compound is prepared through a rearrangement reaction similar to the Arbuzov rearrangement reaction. Specifically, the present invention provides the following technical solutions to solve the above technical problems:

[0013] A preparation method of a bis-DOPO compound, the structural formula of the bis-DOPO compound is as shown in DiDOPO-A below, and its synthesis route is as follows:

[0014] ;

[0015] When the compound B undergoes a rearrangement reaction to obtain the product DiDOPO, the catalyst is an Arbuzov catalyst, and an auxiliary catalyst amide compound is also added. The temperature for the rearrangement reaction is 90-120°C.

[0016] Further, the Arbuzov catalyst is selected from at least one of metal halides (such as sodium iodide, potassium iodide, potassium bromide, sodium bromide, lithium bromide, ferrous bromide, magnesium chloride, nickel chloride, titanium chloride), halogenated hydrocarbons (such as ethyl bromide, ethyl iodide, 1,2-diiodoethane, 1,2-dichloroethane), and elemental iodine. Preferably, it is an alkali metal iodide, such as sodium iodide and potassium iodide.

[0017] Further, the amide compound is selected from at least one of trifluoroacetamide, caprolactam, N,N-dimethylformamide, and N,N-dimethylacetamide; preferably trifluoroacetamide.

[0018] Further, the mass ratio of the Arbuzov catalyst to the amide compound is 1-2:1-2.

[0019] The inventor unexpectedly found that the combination of an Arbuzov catalyst and an amide-based hydrogen bond donor can effectively reduce the temperature of the rearrangement reaction, lowering the reaction temperature to below 120 °C, thus avoiding the problem of corrosion of the reaction equipment caused by the chlorine introduced by the CDOP raw material. Corrosion-resistant enamel reaction kettles are generally used below 150 °C. There are also special enamel reaction kettles with a reaction temperature that can reach 200 °C, but they are relatively expensive. When using only the Arbuzov catalyst alone, the reaction temperature generally needs to be 200 - 230 °C. If a stainless steel reaction kettle that can withstand temperatures above 200 °C is used, at high temperatures, the chlorine introduced by CDOP will cause severe corrosion, resulting in a darker green color of the product, indicating the presence of iron ions. After a long operation time, corrosion of the kettle wall can be observed. Due to a mistake in an experimental operation, the inventor accidentally found that adding an amide-based hydrogen bond donor to the conventional Arbuzov catalyst can significantly reduce the reaction temperature to 90 - 120 °C, and the yield is not significantly adversely affected. When adding only the amide compound alone, no catalytic activity was found. Therefore, the amide compound plays the role of a co-catalyst. The inventor also found that using polyol hydrogen bond donors and carboxylic acid hydrogen bond donors cannot achieve the same effect as the amide-based hydrogen bond donor compound.

[0020] In the previous patent CN112125930A of the inventor, the following synthesis route was disclosed:

[0021] ;

[0022] Among them, the reason why the product structure obtained in the first step is considered to be is that the structure of the subsequent reaction product can correspond to it. However, the inventor later re-studied the reaction mechanism and believes that the correct reaction route should be as described above. The possible reaction mechanism 1 is as follows:

[0023] ;

[0024] The possible reaction mechanism 2 is as follows:

[0025] ;

[0026] The possible mechanism 3 is as follows:

[0027] ;

[0028] Furthermore, the preparation method of the bis-DOPO compound includes the following steps:

[0029] (S1) DOPO and acetophenone react for 2 - 4 h in the presence of an acidic catalyst and at 120 - 140 °C;

[0030] (S2) Cool the system to 10 - 20 °C, add CDOP, and react for 1 - 2 h under the condition of metal chloride as a catalyst;

[0031] (S3) Add Arbuzov catalyst and amide compound, and react for 4 - 6 h under the condition of 100 - 120 °C to prepare the product compound DiDOPO - A.

[0032] Furthermore, in step (S1), the molar ratio of DOPO to acetophenone is 1:1 - 1.5, preferably 1:1.1 - 1.2; the acidic catalyst is selected from at least one of concentrated sulfuric acid and p - toluenesulfonic acid, the dosage of the acidic catalyst is 1 - 5 wt% of the mass of DOPO, the reaction solvent is selected from at least one of diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether, and the reaction condition is to heat up to 110 - 120 °C and react for 5 - 10 h.

[0033] Furthermore, in step (S2), the dosage of CDOP is 1 - 1.05 times the molar amount of DOPO in step (S1), the metal chloride is selected from at least one of magnesium chloride, zinc chloride, iron chloride, and copper chloride, the dosage of the metal chloride is 0.5 - 2 wt% of the mass of DOPO in step (1), and the reaction condition is to react at 10 - 20 °C for 2 - 4 h.

[0034] Furthermore, in step (S3), the Arbuzov catalyst is at least one of metal halides (such as sodium iodide, potassium iodide, potassium bromide, sodium bromide, lithium bromide, iron(II) bromide, magnesium chloride, nickel chloride, titanium chloride), halogenated hydrocarbons (such as ethyl bromide, ethyl iodide, 1,2 - diiodoethane, 1,2 - dichloroethane), and elemental iodine. The addition amount of the Arbuzov catalyst is 1 - 2 wt% of the mass of DOPO, and the addition amount of the amide compound is 1 - 2 wt% of the mass of DOPO.

[0035] In the present invention, the combination of Arbuzov catalyst and amide compound as the catalyst and co - catalyst for the rearrangement reaction can reduce the rearrangement reaction temperature to 90 - 120 °C, preferably 100 - 110 °C, so that an enamel reaction kettle can be used as the reaction equipment, solving the problem that using CDOP as a raw material can improve the yield but is prone to corrode the reaction equipment. Description of the Drawings

[0036] Figure 1 is the infrared spectrum of the product DiDOPO - A obtained in Example 1;

[0037] Figure 2 is the hydrogen nuclear magnetic resonance spectrum of the product DiDOPO - A obtained in Example 1;

[0038] Figure 3It is the phosphorus nuclear magnetic resonance spectrum of the product DiDOPO-A obtained in Example 1. Detailed implementation manners

[0039] The technical solutions of the present invention will be further explained and illustrated by specific examples below.

[0040] Example 1

[0041] (S1) S1DOPO and acetophenone were fed into an enamel reaction kettle according to a molar ratio of 1:1.2. In the presence of p-toluenesulfonic acid at 2 wt% of the mass of DOPO, the temperature was raised to 130 °C and the reaction was carried out under insulation for 4 h;

[0042] (S2) The system was cooled to 10 - 20 °C, 1.05 times the molar amount of CDOP of DOPO was added, and the reaction was carried out for 2 h under the condition of zinc chloride at 0.5 wt% of the mass of DOPO as a catalyst;

[0043] (S3) Sodium iodide at 1 wt% of the mass of DOPO was added as a catalyst, and trifluoroacetamide at 1.5 wt% of the mass of DOPO was added as a co-catalyst. The reaction was carried out at 110 °C for 4 h, then the temperature was lowered, a precipitate was precipitated, and recrystallization was carried out with n-butanol to prepare the product compound DiDOPO-A. It was tested by HPLC, and the product purity was 99.4% and the yield was 97.2%.

[0044] Figure 1 It is the infrared spectrum of the product DiDOPO-A obtained in Example 1. 3067 cm -1 、3030 cm -1 are the stretching vibrations of C-H on the aromatic ring, 1115 cm -1 、931 cm -1 are the stretching vibration absorption peaks of P-O-C (aromatic ring); 1430 cm -1 、1476 cm -1 are the stretching vibration absorption peaks of P-C bonds; 1446 cm -1 is the stretching vibration absorption peak of methylene; 1234 cm -1 is the vibration absorption peak of P=O. It has the characteristic absorption peaks of all functional groups of the target product.

[0045] Figure 2 It is the hydrogen nuclear magnetic resonance spectrum of the product DiDOPO-A obtained in Example 1. The nuclear magnetic data shows that δ2.7 / δ3.0 is the chemical shift of the hydrogen of methylene, and δ3.5 is the chemical shift of the hydrogen of methine. The number and chemical shift of the product hydrogen are basically consistent with the theoretical positions, indicating that its structure is consistent with the target chemical compound.

[0046] Figure 3It is the phosphorus nuclear magnetic resonance spectrum of the product DiDOPO-A obtained in Example 1. The nuclear magnetic data shows that the chemical shift of phosphorus is δ35, which is basically consistent with the theoretical position, indicating that its structure is consistent with the target chemical substance.

[0047] Under the same conditions as above, the reaction temperature in step (S3) was adjusted, and the results are shown in Table 1 below:

[0048] Table 1 Influence of reaction temperature

[0049] 。

[0050] At the reaction temperature of 90 to 120 °C, as the reaction temperature increases, the yield gradually increases. However, after 110 °C, the increase in yield is limited and the purity decreases. Therefore, the reaction temperature of 100 - 110 °C is appropriate.

[0051] Example 2

[0052] Other conditions are the same as in Example 1. The difference is that in step (S3), the reaction temperature is 110 °C, potassium iodide with a mass of 1 wt% of DOPO is added as a catalyst, and N,N-dimethylacetamide with a mass of 2 wt% of DOPO is added as a co-catalyst. The product purity is 99.3% and the yield is 94.9%.

[0053] Example 3

[0054] Other conditions are the same as in Example 1. The difference is that in step (S3), the reaction temperature is 110 °C, and sodium iodide is replaced with sodium bromide of the same mass as a catalyst. The product purity is 99.1% and the yield is 92.6%.

[0055] Example 4

[0056] Other conditions are the same as in Example 1. The difference is that in step (S3), the reaction temperature is 110 °C, and the co-catalyst is replaced with caprolactam of the same mass as trifluoroacetamide. The product purity is 99.1% and the yield is 91.0%.

[0057] Comparative Example 1

[0058] Other conditions are the same as in Example 1. The difference is that in step (S3), the reaction temperature is 100 °C and trifluoroacetamide is not added. After reacting for 10 h, there is basically no product DiDOPO-A.

[0059] Comparative Example 2

[0060] Other conditions are the same as in Example 1. The difference is that in step (S3), the reaction temperature is 100 °C and trifluoroacetamide is replaced with ethylene glycol of the same mass. After reacting for 10 h, there is basically no product DiDOPO-A.

[0061] Comparative Example 3

[0062] Other conditions are the same as in Example 1, except for step (S3). The reaction temperature is 100 °C, trifluoroacetamide is replaced with the same mass of trifluoroacetic acid, the reaction is carried out for 10 h, the product purity is 99.2%, and the yield is 84.7%.

[0063] Comparative Example 4

[0064] Other conditions are the same as in Example 1, except for step (S3). Trifluoroacetamide is not added. The reaction equipment is changed to a stainless-steel reactor, the reaction temperature is increased to 200 °C, the reaction is carried out for 4 h, the product shows a green color, the iron content is > 300 ppm, the product purity is 97.5%, and the yield is 90.4%. After the reactor has been running for a cumulative of 10 days, corrosion can be observed on the reactor wall.

Claims

1. A preparation method of a bis-DOPO compound, the structural formula of the bis-DOPO compound is shown as DiDOPO-A below, and it is characterized in that, The synthetic route is as follows: ； When compound B undergoes a rearrangement reaction to obtain the product DiDOPO, the catalyst is an Arbuzov catalyst, and the Arbuzov catalyst is selected from at least one of sodium iodide, potassium iodide, potassium bromide, and sodium bromide; a cocatalyst amide compound is also added; the amide compound is selected from at least one of trifluoroacetamide, caprolactam, N,N-dimethylformamide, and N,N-dimethylacetamide; the temperature for the rearrangement reaction is 90 - 120 °C; the mass ratio of the Arbuzov catalyst to the amide compound is 1 - 2:1 - 2.

2. A preparation method of a bis-DOPO compound, characterized in that, It includes the following steps: (S1) DOPO and acetophenone react for 2 - 4 h in the presence of an acidic catalyst and at 120 - 140 °C; (S2) The system is cooled to 10 - 20 °C, CDOP is added, and the reaction occurs for 1 - 2 h under the condition of a metal chloride as a catalyst; (S3) The Arbuzov catalyst and the amide compound are added, and the reaction occurs for 4 - 6 h at 100 - 120 °C to prepare the product compound DiDOPO - A; ； The Arbuzov catalyst is selected from at least one of sodium iodide, potassium iodide, potassium bromide, and sodium bromide; the amide compound is selected from at least one of trifluoroacetamide, caprolactam, N,N-dimethylformamide, and N,N-dimethylacetamide; the mass ratio of the Arbuzov catalyst to the amide compound is 1 - 2:1 - 2.

3. The preparation method according to claim 2, wherein In step (S1), the molar ratio of DOPO to acetophenone is 1:1 - 1.5; the acidic catalyst is selected from at least one of concentrated sulfuric acid and p-toluenesulfonic acid, the dosage of the acidic catalyst is 1 - 5 wt% of the mass of DOPO, the reaction solvent is selected from at least one of diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether, and the reaction condition is to heat up to 110 - 120 °C and react for 5 - 10 h.

4. The preparation method according to claim 2, characterized in that, In step (S2), the dosage of CDOP is 1 - 1.05 times the molar amount of DOPO in step (S1), the metal chloride is selected from at least one of magnesium chloride, zinc chloride, iron chloride, and copper chloride, the dosage of the metal chloride is 0.5 - 2 wt% of the mass of DOPO in step (1), and the reaction condition is to react at 10 - 20 °C for 2 - 4 h.

5. The preparation method according to claim 2, characterized in that, In step (S3), the addition amount of the Arbuzov catalyst is 1 - 2 wt% of the mass of DOPO, and the addition amount of the amide compound is 1 - 2 wt% of the mass of DOPO.

6. The preparation method according to claim 5, characterized in that, The Arbuzov catalyst is selected from at least one of sodium iodide and potassium iodide, and the amide compound is selected from at least one of trifluoroacetamide, caprolactam, N,N-dimethylformamide, and N,N-dimethylacetamide.

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