Preparation method of double-DOPO compound

Abstract

The invention relates to a preparation method of a double-DOPO (9, 10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide) compound, which comprises the following steps: (S1) reacting DOPO and acetophenone in the presence of an acid catalyst at 120-140 DEG C for 2-4 hours; (S2) cooling the system to 10-20 DEG C, adding CDOP, and reacting for 1-2 hours under the condition that metal chloride is used as a catalyst; and (S3) adding an Arbuzov catalyst and an amide compound, and carrying out a reaction at 100-120 DEG C for 4-6 h so as to prepare the product compound DiDOPO-A. According to the method, the Arbuzov catalyst is used as the catalyst, the amide compound is used as the cocatalyst, and the rearrangement reaction temperature can be reduced to 90-120 DEG C, so that an enamel reaction kettle can be used as reaction equipment, and the problem that the reaction equipment is easily corroded when CDOP is used as a raw material to improve the yield is solved.

Description

Technical Field

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

[0002] 9,10-Dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) is a new type of halogen-free flame retardant, which contains a PH bond and can react with olefinic groups, epoxy groups, and carbonyl groups to prepare a variety of DOPO-based derivatives. The prior art reports that two or more DOPOs are connected by bridging to prepare a double DOPO derivative with excellent flame retardant properties as a flame retardant.

[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 in the following formula (I): (I) This compound was first reported by Japanese patent JPH11-106619, and was prepared by DOPO and diols or dihalogenated hydrocarbons. For example, CN104086593A reported a method for preparing DiDOPO-A, which is to react acetophenone and DOPO in the presence of an acidic catalyst, and the pH 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, and the halogenated phosphate ester is eliminated to obtain an alkenyl phosphate ester, which is then reacted with another molecule of DOPO to obtain a bridged di-DOPO compound. Specifically, the content described in Example 1 is as follows: DOPO (86.40g, 0.40mol), acetophenone (24.05g, 0.20mol) and 10 ml of xylene are 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 mixed solution was heated to 154°C and phosphorus oxychloride was added dropwise. 3 (30.25g) was slowly added dropwise to the reaction solution within 25 hours, and the fractions were collected in a water separator, maintaining the reaction temperature at 154-160°C. After the phosphorus oxychloride was dripped, it was kept warm for half an hour. After cooling, 120g of isopropanol was added and stirred under reflux. After the crude product softened, most of it dissolved and the system became turbid. Stirring and cooling were stopped, and a large amount of product precipitated after standing for a period of time. After suction 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. After collection, it was dried at 110°C for 13h to obtain 89g of product with a yield of 83.2%. However, the inventor could not repeat the conditions recorded in the patent, and the yield was only about 60%. The inventor believes that the patent hides the key process steps, or the actual yield is not as high as claimed in the patent.

[0004] CN110885344A discloses a method for preparing a DOPO vinylidene bridged derivative, and the synthetic route is as follows: ; This patent uses cyclic carbonate as a raw material for the reaction, but the final yield is not high.

[0005] CN103408594A discloses a method for preparing a high-purity DOPO derivative, which also involves an Arbuzov rearrangement reaction, in which a certain amount of an acid-binding agent, such as triethylamine, is added. The patent states that the addition of an acid-binding agent can reduce the reaction temperature and complete the reaction at 120°C. However, an equimolar amount or excess of an acid-binding agent is required, which is costly, and the yield of the patent is calculated based on ethylene glycol. In fact, other products may be obtained by the participation of ethylene glycol in the reaction, and the actual yield of the di-DOPO used in the patent is lower.

[0006] The inventor's previous patent CN112125930A disclosed a method for preparing a bis-DOPO compound containing an aromatic group, using a compound of methyl benzenesulfonate and a heteropoly acid as a catalyst to reduce the reaction temperature to 140-160°C. However, the presence of heteropoly acids will also cause certain corrosion to the equipment. Moreover, due to miscalculation at the time and insufficient purification of the product, the yield of the patent could not actually reach the high level claimed in the patent.

[0007] The DiDOPO-A compound has attracted the attention of researchers due to its excellent flame retardant properties. However, the yield of the current preparation method and the prospects for industrial production still need to be improved. It is necessary to develop a preparation method with simple process and high yield. Summary of the invention

[0008] In order to solve the defects of the complex preparation process and unsatisfactory yield of DiDOPO-A compounds, the present invention provides a preparation method of DiDOPO-A compounds, the first step is consistent with the literature, which is the reaction of DOPO and acetophenone, and then the synthesis route is changed, CDOP is used as the raw material for introducing the second molecule of DOPO, and then the product DiDOPO-A compound is prepared by Arbuzov-like rearrangement reaction. Specifically, the present invention provides the following technical solutions to solve the above technical problems: A method for preparing a di-DOPO compound, wherein the di-DOPO compound has a structural formula as shown below: DiDOPO-A, and its synthesis route is as follows: ; When compound B is rearranged to obtain product DiDOPO, the catalyst is Arbuzov catalyst, and a co-catalyst amide compound is added. The temperature during the rearrangement reaction is 90-120°C.

[0009] 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.

[0010] Furthermore, the amide compound is selected from at least one of trifluoroacetamide, caprolactam, N,N-dimethylformamide, and N,N-dimethylacetamide; preferably trifluoroacetamide.

[0011] Furthermore, the mass ratio of the Arbuzov catalyst to the amide compound is 1-2:1-2.

[0012] The inventor unexpectedly found that the combination of Arbuzov catalyst and amide hydrogen bond donor can effectively reduce the temperature of the rearrangement reaction, so that the reaction temperature can be reduced to below 120°C, avoiding the problem of easy corrosion of the reaction equipment caused by the chlorine introduced by the CDOP raw material. Corrosion-resistant enamel reactors are generally used below 150°C. There are also special enamel reactors with a reaction temperature of up to 200°C, but they are relatively expensive. Generally, when Arbuzov catalyst is used alone, the reaction temperature generally needs to be 200-230°C. If a stainless steel reactor that can withstand more than 200°C is used, the chlorine introduced by CDOP will cause severe corrosion at high temperatures, causing the product to deepen in green, indicating the presence of iron ions, and corrosion of the reactor wall can be observed for a long time. Due to an experimental operation error, the inventor accidentally found that in the conventional Arbuzov catalyst, the addition of amide hydrogen bond donors can significantly reduce the reaction temperature to 90-120°C, and the yield is not significantly adversely affected. However, when amide compounds are added alone, no catalytic activity is found, so amide compounds play the role of co-catalysts. The inventors also found that the use of polyol hydrogen bond donors and carboxylic acid hydrogen bond donors cannot achieve the same effect as amide hydrogen bond donor compounds.

[0013] The inventor disclosed the following synthesis route in the previous patent CN112125930A: ; The reason why we think that the product structure obtained by the first step reaction is , which is due to the structure of the subsequent reaction product. However, the inventor later re-studied the reaction mechanism and believed that the correct reaction route should be as described above. Possible reaction mechanism 1 is as follows: ; The possible reaction mechanism 2 is as follows: ; Possible mechanism 3 is as follows: ; Furthermore, the preparation method of the bis-DOPO compound comprises the following steps: (S1) DOPO and acetophenone are reacted in the presence of an acidic catalyst at 120-140 °C for 2-4 h; (S2) the system is cooled to 10-20° C., CDOP is added, and the reaction is carried out for 1-2 hours under the condition of metal chloride as a catalyst; (S3) adding Arbuzov catalyst and amide compound, reacting at 100-120° C. for 4-6 hours to prepare product compound DiDOPO-A.

[0014] 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 amount of the acidic catalyst is 1-5wt% of the mass of DOPO, the reaction solvent is selected from at least one of diethylene glycol dimethyl ether, diethylene glycol diethyl ether or diethylene glycol dibutyl ether, and the reaction conditions are heating to 110-120°C and reacting for 5-10h.

[0015] Furthermore, in step (S2), the amount 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, ferric chloride, and copper chloride, the amount of metal chloride is 0.5-2wt% of the mass of DOPO in step (1), and the reaction conditions are 10-20°C for 2-4h.

[0016] Further, in step (S3), the Arbuzov catalyst is at least one of a metal halide (such as sodium iodide, potassium iodide, potassium bromide, sodium bromide, lithium bromide, ferrous bromide, magnesium chloride, nickel chloride, titanium chloride), a halogenated hydrocarbon (such as ethyl bromide, ethyl iodide, 1,2-diiodoethane, 1,2-dichloroethane), and elemental iodine. The amount of the Arbuzov catalyst added is 1-2wt% of the mass of DOPO, and the amount of the amide compound added is 1-2wt% of the mass of DOPO.

[0017] The present invention uses a composite of an Arbuzov catalyst and an amide compound as a catalyst and a co-catalyst for the rearrangement reaction, thereby reducing the rearrangement reaction temperature to 90-120° C., preferably 100-110° C., so that an enamel reactor can be used as a reaction device, thereby solving the problem that using CDOP as a raw material to increase the yield but easily corrode the reaction device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is the infrared spectrum of the product DiDOPO-A obtained in Example 1; Figure 2 is the hydrogen nuclear magnetic resonance spectrum of the product DiDOPO-A obtained in Example 1; Figure 3 This is the phosphorus nuclear magnetic resonance spectrum of the product DiDOPO-A obtained in Example 1. DETAILED DESCRIPTION

[0019] The technical solution of the present invention is further explained and illustrated by specific embodiments below.

[0020] Example 1 (S1DOPO and acetophenone were added into an enameled reactor at a molar ratio of 1:1.2, and in the presence of p-toluenesulfonic acid (2 wt% of DOPO mass), the temperature was raised to 130°C and kept for 4 hours; (S2) the system is cooled to 10-20° C., CDOP (1.05 times the molar amount of DOPO) and zinc chloride (0.5 wt% of the mass of DOPO) are added as catalysts and reacted for 2 h; (S3) Sodium iodide (1 wt% by weight of DOPO) was added as a catalyst, and trifluoroacetamide (1.5 wt% by weight of DOPO) was added as a co-catalyst, and the mixture was reacted at 110° C. for 4 h, cooled, and a precipitate was precipitated, and recrystallized from n-butanol to obtain a product compound DiDOPO-A. The product was tested by HPLC, and the purity of the product was 99.4% and the yield was 97.2%.

[0021] Figure 1 This is the infrared spectrum of DiDOPO-A obtained in Example 1. 3067 cm -1 、3030 cm -1 is the stretching vibration of CH on the aromatic ring, 1115 cm -1 、931 cm -1 The peak at 1430 cm is the stretching vibration absorption peak of POC (aromatic ring); -1 、1476 cm -1 is the stretching vibration absorption peak of PC bond; 1446 cm -1 The peak at 1234 cm is the stretching vibration absorption peak of methylene; -1It is the vibration absorption peak of P=O. It has characteristic absorption peaks of all functional groups of the target product.

[0022] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the product DiDOPO-A obtained in Example 1. The nuclear magnetic resonance data are: δ2.7 / δ3.0 is the chemical shift of hydrogen of the methylene group, and δ3.5 is the chemical shift of hydrogen of the methyne group. The number and chemical shift of hydrogen in the product are basically consistent with the theoretical position, indicating that its structure is consistent with the target chemical.

[0023] Figure 3 This is the phosphorus nuclear magnetic resonance spectrum of the product DiDOPO-A obtained in Example 1. The nuclear magnetic resonance data shows that δ35 is the chemical shift of phosphorus, and the chemical shift is basically consistent with the theoretical position, indicating that its structure is consistent with the target chemical.

[0024] Under the same conditions as in the above steps, the reaction temperature of step (S3) was adjusted, and the results are shown in Table 1 below: Table 1 Effect of reaction temperature .

[0025] At a reaction temperature of 90 to 120°C, as the reaction temperature increases, the yield gradually increases, but after 110°C, the yield increase is limited and the purity decreases, so a reaction temperature of 100-110°C is appropriate.

[0026] Example 2 The other conditions were the same as those in Example 1, except that in step (S3), the reaction temperature was 110°C, 1 wt% of the mass of DOPO potassium iodide was added as a catalyst, and 2 wt% of the mass of DOPO N,N-dimethylacetamide was added as a co-catalyst. The product purity was 99.3% and the yield was 94.9%.

[0027] Example 3 The other conditions were the same as those in Example 1, except that in step (S3), the reaction temperature was 110°C, and sodium iodide was replaced by an equal mass of sodium bromide as a catalyst. The product purity was 99.1%, and the yield was 92.6%.

[0028] Example 4 The other conditions were the same as those in Example 1, except that in step (S3), the reaction temperature was 110°C, and the co-catalyst was replaced by an equal mass of caprolactam instead of trifluoroacetamide. The product purity was 99.1%, and the yield was 91.0%.

[0029] Comparative Example 1 The other conditions were the same as those in Example 1, except that in step (S3), the reaction temperature was 100° C., and no trifluoroacetamide was added. After reacting for 10 h, there was substantially no product DiDOPO-A.

[0030] Comparative Example 2 The other conditions were the same as those in Example 1, except that in step (S3), the reaction temperature was 100° C., trifluoroacetamide was replaced by an equal mass of ethylene glycol, and the reaction was continued for 10 h, and substantially no product DiDOPO-A was obtained.

[0031] Comparative Example 3 The other conditions were the same as those in Example 1, except that in step (S3), the reaction temperature was 100° C., trifluoroacetamide was replaced by an equal mass of trifluoroacetic acid, the reaction was carried out for 10 h, and the product purity was 99.2% and the yield was 84.7%.

[0032] Comparative Example 4 The other conditions were the same as those in Example 1, except that trifluoroacetamide was not added in step (S3). The reaction equipment was replaced with a stainless steel reactor, the reaction temperature was increased to 200°C, the reaction was continued for 4 hours, the product was green, the iron content was greater than 300ppm, and the product purity was 97.5%. The yield was 90.4%. After the reactor had been running for 10 days, corrosion was observed on the reactor wall.

Claims

1. A method for preparing a di-DOPO compound, wherein the di-DOPO compound has the structural formula DiDOPO-A shown below, characterized in that: Its synthetic route is as follows: ； When compound B is rearranged to obtain product DiDOPO, the catalyst is Arbuzov catalyst, and a co-catalyst amide compound is added; the amide compound is selected from at least one of trifluoroacetamide, caprolactam, N,N-dimethylformamide, and N,N-dimethylacetamide; the temperature during the rearrangement reaction is 90-120°C.

2. The preparation method according to claim 1, characterized in that: The Arbuzov catalyst is selected from at least one of metal halides, halogenated hydrocarbons and elemental iodine.

3. The preparation method according to claim 2, characterized in that: The metal halide is selected from at least one of sodium iodide, potassium iodide, potassium bromide, sodium bromide, lithium bromide, ferrous bromide, magnesium chloride, nickel chloride, and titanium chloride; the halogenated hydrocarbon is selected from at least one of ethyl bromide, ethyl iodide, 1,2-diiodoethane, and 1,2-dichloroethane.

4. The preparation method according to claim 1, characterized in that: The amide compound is selected from at least one of trifluoroacetamide, caprolactam, N,N-dimethylformamide and N,N-dimethylacetamide.

5. The preparation method according to claim 1, characterized in that: The mass ratio of the Arbuzov catalyst to the amide compound is 1-2:1-2.

6. A method for preparing a bis-DOPO compound, characterized in that: The following steps are involved: (S1) DOPO and acetophenone are reacted in the presence of an acidic catalyst at 120-140 °C for 2-4 h; (S2) the system is cooled to 10-20° C., CDOP is added, and the reaction is carried out for 1-2 hours under the condition of metal chloride as a catalyst; (S3) adding Arbuzov catalyst and amide compound, reacting at 100-120° C. for 4-6 hours to prepare product compound DiDOPO-A; 。 7. The preparation method according to claim 6, characterized in that: 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 amount of the acidic catalyst is 1-5wt% of the mass of DOPO, the reaction solvent is selected from at least one of diethylene glycol dimethyl ether, diethylene glycol diethyl ether or diethylene glycol dibutyl ether, and the reaction conditions are heating to 110-120°C and reacting for 5-10h.

8. The preparation method according to claim 6, characterized in that: In step (S2), the amount 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, ferric chloride and copper chloride, the amount of metal chloride is 0.5-2wt% of the mass of DOPO in step (1), and the reaction conditions are 10-20°C for 2-4h.

9. The preparation method according to claim 6, characterized in that: In step (S3), the Arbuzov catalyst is at least one of metal halides, halogenated hydrocarbons, and elemental iodine; the amount of the Arbuzov catalyst added is 1-2wt% of the mass of DOPO, and the amount of the amide compound added is 1-2wt% of the mass of DOPO.

10. The preparation method according to claim 9, 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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