A method for preparing 4-phenylacetylenyl phthalic anhydride

Abstract

The application provides a preparation method of 4-phenylacetylenyl phthalic anhydride, which comprises the following steps: (1) 4-halophthalic anhydride is reacted with phenylacetylene in the presence of a catalyst to obtain 4-phenylacetylenyl phthalic acid; (2) 4-phenylacetylenyl phthalic acid obtained in the step (1) is reacted with acetic anhydride to obtain the 4-phenylacetylenyl phthalic anhydride. The preparation method is not only low in cost (<350 yuan / 100g) and high in yield (>98%), but also simple, and is more suitable for large-scale industrial production, and the increased extraction operation is beneficial to the enrichment and recycling of the catalyst and the solvent.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology, specifically relating to a method for preparing 4-phenylethynyl phthalic anhydride. Background Technology

[0002] In recent years, the development of air defense and anti-missile systems, long-range precision strikes, and future intelligent missiles has placed increasingly higher demands on the impulse-mass ratio and thermal / mechanical stability of solid rocket motors. Existing resins such as phenolic and epoxy resins are insufficient to meet the temperature resistance requirements. There is an urgent need to develop high-performance composite material components that can integrate multiple functions such as lightweight, active thermal protection, etc., while meeting various indicators such as ultra-lightweight, ultra-high load-bearing capacity, extreme heat resistance, and high adaptability.

[0003] Polyimide (PI) has broad application prospects in aerospace due to its significant advantages (good glass transition temperature, good thermal oxidation stability, and excellent mechanical properties). Thermoplastic polyimide (TPI) was developed based on the modification of thermosetting PI, solving the problems of infusibility, insolubility, and poor processability of thermosetting PI. However, the high-temperature resistance and thermal / mechanical properties of existing TPI resins are inferior to those of thermosetting PI. Inspired by the reinforcement strategies of commercial polyimides, an end-capping strategy is proposed to improve the high-temperature resistance and thermal / mechanical properties of TPI. Commonly used end-capping groups include norbornene, ethynyl, maleimide, and phenylethynyl. Norbornene-capped PI suffers from poor thermal stability consistency due to its high crosslinking density; ethynyl-capped PI tends to become brittle after curing, narrowing the processing window; and maleamide-capped products also face the problem of becoming brittle after curing, posing a significant processing challenge. Phenylacetyl-terminated polyimides, represented by 4-phenylethynyl phthalic anhydride, possess superior processing performance, mechanical properties, and thermal oxidation stability, and have already been applied to a structural component of an aero-engine in a pre-research project. However, 4-phenylethynyl phthalic anhydride is expensive (market price 11,000 RMB / kg), and only a few domestic manufacturers supply it in custom-made, kilogram-level quantities. The raw material 4-bromo(chloro)phthalic acid in existing patents (CN103641806A, CN101550121A, CN101550122A) is 20 times more expensive than 4-bromophthalic anhydride, and its yield is lower. Moreover, the preparation process does not involve pre-enrichment and pretreatment processes for subsequent palladium catalyst and waste liquid recovery processes, which undoubtedly increases the manufacturing cost of the product. Related reports can be found in the literature ("Advanced Materials Research, 750-752, 1769-1772", "Asian Journal of Chemistry, 2015, 27, 5, 1644-1646", "Chinese Chemical Letters, 2011, 22, 159-162", "Journal of Chemical Research, 2012, 379-380").

[0004] Therefore, developing a low-cost, high-yield method for preparing 4-phenylethynyl phthalic anhydride is an urgent problem to be solved in this field. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a method for preparing 4-phenylethynyl phthalic anhydride. This method is simple, with mild reaction conditions and a straightforward process. After the reaction, the organic salt can be separated, and the catalyst and waste liquid can also be separated and recycled, making it suitable for large-scale industrial production and providing low-cost raw materials for the mass production of high-temperature resistant thermoplastic polyimides.

[0006] To achieve this objective, the present invention adopts the following technical solution:

[0007] This invention provides a method for preparing 4-phenylethynyl phthalic anhydride, the method comprising:

[0008] (1) 4-Hyrophthalic anhydride reacts with phenylacetylene in the presence of a catalyst to give 4-phenylacetylene-based phthalic acid.

[0009] (2) The 4-phenylethynyl phthalic acid obtained in step (1) is reacted with acetic anhydride to obtain the 4-phenylethynyl phthalic anhydride.

[0010] Preferably, the molar ratio of 4-halophthalic anhydride to phenylacetylene in step (1) is 1:(1-1.2), for example, it can be 1:1, 1:1.05, 1:1.1, 1:1.15, 1:1.2, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0011] Preferably, the 4-halophthalic anhydride comprises 4-bromophthalic anhydride.

[0012] Preferably, the catalyst in step (1) comprises a combination of bis(triphenylphosphine)palladium dichloride, cuprous iodide and triphenylphosphine.

[0013] This invention discloses a low-cost, high-yield method for preparing 4-phenylethynyl phthalic anhydride. The process mainly involves five optimization aspects: feed ratio, catalyst, acid-binding agent, solvent, and post-reaction green treatment. The resulting low-cost (<300 RMB / 100g), high-yield (>97%), and high-purity 4-phenylethynyl phthalic anhydride can meet the application requirements for low-cost, large-scale preparation of high-temperature (300–400℃) thermoplastic polyimide resins for aerospace propulsion. The synthesis method of this invention is simple, the reaction conditions are mild, and the process is straightforward. After the reaction, the organic salt can be separated, and the catalyst and waste liquid can also be separated and recycled, making it suitable for large-scale industrial production.

[0014] Preferably, the molar ratio of triphenylphosphine, bis(triphenylphosphine)palladium dichloride and cuprous iodide is 1:(1-1.1):1, for example, it can be 1:1:1, 1:1.05:1, 1:1:1, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0015] Preferably, the molar amount of the catalyst is 0.1-0.25% of the molar amount of 4-phenylethynyl phthalic anhydride, for example, it can be 0.1%, 0.15%, 0.2%, 0.25%, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0016] Preferably, the reaction in step (1) is carried out in the presence of an acid-binding agent and a first solvent.

[0017] Preferably, the acid-binding agent comprises any one or a combination of at least two of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, triethylamine, or pyridine.

[0018] Preferably, the molar ratio of the acid-binding agent to 4-halophthalic anhydride is (2-3):1, for example, it can be 2:1, 2.2:1, 2.5:1, 2.8:1, 3:1, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0019] Preferably, in step (1), the first solvent comprises any one or a combination of at least two of anhydrous dimethylformamide, dimethylacetamide, or dimethyl sulfoxide.

[0020] Preferably, based on the mass of 4-halophthalic anhydride as 1g, the volume of the first solvent in step (1) is 20-40mL, for example, it can be 20mL, 25mL, 30mL, 35mL, 40mL, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0021] Preferably, the reaction in step (1) is carried out under the protection of an inert gas.

[0022] Preferably, the inert gas includes nitrogen and / or argon.

[0023] Preferably, the reaction temperature in step (1) is 80-120°C, for example, it can be 80°C, 90°C, 100°C, 110°C, 120°C, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0024] Preferably, the reaction time in step (1) is 4-6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0025] Preferably, after the reaction in step (1), the process further includes cooling, first filtration, extraction, pH adjustment, second filtration, washing, and drying to obtain the 4-phenylethynyl phthalic acid.

[0026] Preferably, the first filtration includes adding water to precipitate the sediment before filtration.

[0027] Preferably, based on the mass of 1g of 4-halophthalic anhydride, the volume of water is 10-15mL, for example, 10mL, 11mL, 12mL, 13mL, 14mL, 15mL, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0028] Preferably, the extraction includes dissolving the substance in an extractant and then extracting it.

[0029] Preferably, the extractant comprises any one or a combination of at least two of dichloromethane, ethyl acetate, or chloroform.

[0030] Preferably, the pH adjustment includes adding hydrochloric acid solution to adjust to 2-4, for example, 2, 2.5, 3, 3.5, 4, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0031] 4-Hyrophthalic anhydride, triphenylphosphine, palladium dichloride of bis(triphenylphosphine) chloride, and cuprous iodide were dissolved in a first solvent, followed by the addition of an acid-binding agent and phenylacetylene. After the addition was complete, the reaction system was subjected to three purging and three venting cycles to remove oxygen, and then protected with a nitrogen-filled balloon at the top of the condenser. The reaction system was then transferred to an oil bath for further reaction. Finally, the mixture after the reaction was completed was cooled, filtered, and the filtrate was retained. Water was added to the filtrate while stirring until a brick-red flocculent precipitate appeared. Then, an extractant was added for extraction, and the aqueous phase was retained. The pH of the aqueous phase was adjusted to 2-4 with dilute hydrochloric acid solution. Finally, the mixture was filtered, washed, and dried to obtain 4-phenylacetylene-based phthalic acid.

[0032] Preferably, based on the mass of 4-halophthalic anhydride as 1g, the volume of acetic anhydride in step (2) is 3-10mL, for example, it can be 3mL, 4mL, 5mL, 6mL, 8mL, 10mL, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0033] Preferably, the reaction temperature in step (2) is 90-140℃, for example, it can be 90℃, 100℃, 110℃, 120℃, 130℃, 140℃, and specific values ​​between the above points. Due to space limitations and for the sake of brevity, the present invention will not exhaustively list the specific values ​​included in the range.

[0034] Preferably, the reaction time in step (2) is 2-3 hours, for example, 2 hours, 2.2 hours, 2.5 hours, 2.8 hours, 3 hours, and specific values ​​between the above values. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific values ​​included in the range.

[0035] Preferably, the reaction in step (2) further includes concentration, recrystallization, filtration, and drying.

[0036] Preferably, the concentrated product is dissolved in a second solvent and recrystallized.

[0037] Preferably, the second solvent comprises any one or a combination of at least two of anhydrous toluene, n-hexane, or diethyl ether.

[0038] If the second solvent is a mixture of two solvents, then the volume ratio of the two solvents is 1:(1-2).

[0039] The product obtained in step (1) is added to the acetic anhydride solution, heated to reflux, cooled and then the reaction solution is removed by rotary evaporator. The reaction solution is collected, dehydrated and recycled. The concentrated phase yields crude 4-phenylethynyl phthalic anhydride. The crude product is then recrystallized with a second solvent, filtered and dried sequentially to obtain refined 4-phenylethynyl phthalic anhydride.

[0040] Preferably, the preparation method specifically includes:

[0041] (1) Mix 4-halophthalic anhydride, bis(triphenylphosphine) palladium dichloride, phenylacetylene triphenylphosphine, cuprous iodide, acid-binding agent and first solvent, and react at 80-120℃ for 4-6h. Cool, filter for the first time, extract, adjust pH, filter for the second time, wash and dry to obtain 4-phenylacetylene phthalic acid.

[0042] The molar ratio of 4-bromophthalic anhydride to phenylacetylene is 1:(1-1.2); the molar ratio of triphenylphosphine, bis(triphenylphosphine)palladium dichloride to cuprous iodide is 1:(1-1.1):1; the acid-binding agent includes any one or a combination of at least two of sodium carbonate, potassium carbonate, sodium hydroxide, potassium hydroxide, triethylamine, or pyridine; the molar ratio of the acid-binding agent to 4-bromophthalic anhydride is (2-3):1;

[0043] (2) The 4-phenylethynyl phthalic acid obtained in step (1) is mixed with acetic anhydride, reacted at 90-140℃ for 2-3 hours, concentrated, recrystallized, filtered and dried to obtain the 4-phenylethynyl phthalic anhydride.

[0044] With 1 g of 4-halophthalic anhydride, the volume of the acetic anhydride is 3-10 mL.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] This invention provides a method for preparing 4-phenylethynyl phthalic anhydride. This method is not only low-cost (<350 RMB / 100g) and has a high yield (>98%), but the added extraction operation also facilitates the enrichment and recycling of catalyst and solvent. 90-95% of the catalyst is enriched in the organic phase. The organic phase is then subjected to rotary evaporation, and the distilled extractant can be recycled, yielding a concentrated catalyst phase that is easy to recover. Therefore, this preparation method is simple and incorporates a complete material monitoring system for the preparation of 4-phenylethynyl phthalic anhydride, making it more suitable for large-scale industrial production. Attached Figure Description

[0047] Figure 1 A schematic diagram of the synthetic route for 4-phenylethynyl phthalic anhydride provided by the present invention;

[0048] Figure 2 The purity diagrams are for 4-phenylethynyl phthalic acid prepared in Examples 1-5 of this invention.

[0049] Figure 3 The 1H NMR spectrum of 4-phenylethynyl phthalic anhydride prepared in Example 1 of this invention;

[0050] Figure 4 The purity diagrams are for the 4-phenylethynyl phthalic anhydride prepared in Examples 1-5 of this invention. Detailed Implementation

[0051] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0052] Example 1

[0053] This embodiment provides a 4-phenylacetylene phthalic anhydride and its preparation method, the preparation method comprising:

[0054] (1) 4-Bromophthalic anhydride (0.44 mol), triphenylphosphine, cuprous iodide, and palladium dichloride dichloride (1:1.02:1) were dissolved in anhydrous dimethylacetamide (300 mL). The amount of triphenylphosphine, cuprous iodide, and palladium dichloride dichloride added was 0.25% of the amount of 4-bromophthalic anhydride. Then, phenylacetylene (0.44 mol) and triethylamine (1.1 mol, 2.5 times the amount of 4-bromophthalic anhydride) were added. The reaction system was then subjected to three purging and three venting cycles to remove oxygen. The reaction system was then transferred to an oil bath, the reaction temperature was set to 80 °C, and the reaction time was 5 h. The mixture was then cooled to room temperature. The reaction solution was filtered, and water was added until a brick-red flocculent precipitate appeared. The mixture was then extracted three times with ethyl acetate, and the organic and aqueous phases were retained respectively. The organic phase was enriched with the catalyst. The ethyl acetate was then evaporated to recover the catalyst. The pH of the aqueous phase was adjusted to 2–4 with dilute hydrochloric acid solution, at which point a large amount of pale yellow precipitate was formed. The precipitate was filtered and dried completely in a vacuum oven at 80°C to obtain 4-phenylethynyl phthalic acid. The filtrate was then subjected to rotary evaporation to separate water, dimethylacetamide, and organic salts. The water and dimethylacetamide were recovered and recycled.

[0055] (2) Weigh a certain amount of the 4-phenylethynyl phthalic acid obtained above and place it in a flask containing acetic anhydride, with a concentration of 3 mL / g. Place the reaction system in a 90℃ water bath and react for 2 h. After the reaction is complete, evaporate the acetic anhydride using a rotary evaporator, add a mixture of toluene / n-hexane (V:V = 1:1), and recrystallize to obtain 4-phenylethynyl phthalic anhydride.

[0056] The obtained 4-phenylethynyl phthalic acid has a high yield and purity, such as Figure 2 As shown, the yield was 99.23%, and the purity was measured by HPLC using an Agilent 1260 HPLC system. A gradient concentration method was employed, with the detection wavelength set at 254 nm and the test time at 20 min. The purity of 4-phenylethynyl phthalic acid was 98.61%. Figure 2 The liquid nuclear magnetic resonance (NMR) spectrum of the 4-phenylethynyl phthalic anhydride product prepared by this invention is completely consistent with that of the 4-phenylethynyl phthalic acid standard. Figure 3 This indicates that the product prepared by this invention is the target product, with a yield of 97.24%. Purity was still tested by HPLC, and the purity was found to be 98.07%. Figure 4 ).

[0057] Example 2

[0058] This embodiment provides a 4-phenylacetylene phthalic anhydride and its preparation method, the preparation method comprising:

[0059] (1) 4-Chlorophthalic anhydride (0.44 mol), triphenylphosphine, cuprous iodide, and palladium dichloride of bis(triphenylphosphine) (1:1.04:1) were dissolved in anhydrous dimethylacetamide (350 mL). The amount of triphenylphosphine, cuprous iodide, and palladium dichloride added was 0.23% of the amount of 4-bromophthalic anhydride. Then, phenylacetylene (0.46 mol) and triethylamine (0.968 mol, 2.2 times the amount of 4-bromophthalic anhydride) were added. Oxygen was removed by a three-stage purging and venting process. The reaction system was then transferred to an oil bath, the reaction temperature was set to 90 °C, and the reaction time was 4 h. The mixture was then cooled to room temperature. The reaction solution was filtered, and water was added until a brick-red flocculent precipitate appeared. Ethyl acetate was added for extraction three times, retaining the organic and aqueous phases respectively. The organic phase was enriched with the catalyst, and the ethyl acetate could then be separated for catalyst recovery. The pH of the aqueous phase was adjusted to 2–4 with dilute hydrochloric acid solution, at which point a large amount of pale yellow precipitate formed. The precipitate was filtered and dried completely in a vacuum oven at 80°C to obtain 4-phenylethynyl phthalic acid. The filtrate was then subjected to rotary evaporation to separate water, dimethylacetamide, and organic salts. The water and dimethylacetamide were recovered and recycled.

[0060] (2) Weigh a certain amount of the 4-phenylethynyl phthalic acid obtained above and place it in a flask containing acetic anhydride, with a concentration of 5 mL / g. Place the reaction system in a water bath at 100 °C and react for 2.5 h. After the reaction is complete, separate the acetic anhydride using a rotary evaporator, then add diethyl ether and recrystallize to obtain 4-phenylethynyl phthalic anhydride.

[0061] The obtained 4-phenylethynyl phthalic acid has a high yield and purity, such as Figure 2 As shown, the yield was 99.53%, and the purity was measured by HPLC using an Agilent 1260 HPLC system. Mobile phase A was acetonitrile, and mobile phase B was deionized water containing 0.05% triacetic acid by volume. A gradient concentration method was used, with a test time of 20 min. The mobile phase flow rate was 1.2 mL / min, and the detection wavelength was set to 254 nm. The purity was found to be 99.58%. The liquid NMR spectrum of the 4-phenylethynyl phthalic anhydride product prepared in this invention was completely consistent with the spectrum of the 4-phenylethynyl phthalic anhydride standard, indicating that the product prepared in this invention is the target product, with a yield of 98.74%. Purity was again measured by HPLC, and the purity was found to be 99.08%.

[0062] Example 3

[0063] This embodiment provides a 4-phenylacetylene phthalic anhydride and its preparation method, the preparation method comprising:

[0064] (1) 4-Iodophthalic anhydride (0.44 mol), triphenylphosphine, cuprous iodide, and palladium dichloride dichloride (1:1.06:1) were dissolved in anhydrous dimethylacetamide (350 mL). The amount of triphenylphosphine, cuprous iodide, and palladium dichloride dichloride added was 0.23% of the amount of 4-bromophthalic anhydride. Then, phenylacetylene (0.48 mol) and triethylamine (1.012 mol, 2.3 times the amount of 4-bromophthalic anhydride) were added. Oxygen was removed by a three-stage purging and venting process. The reaction system was then transferred to an oil bath, and the reaction temperature was set to 80 °C for 4 h. The mixture was then cooled to room temperature. The reaction solution was filtered, and water was added until a brick-red flocculent precipitate appeared. Ethyl acetate was added for extraction three times, retaining the organic and aqueous phases respectively. The organic phase was enriched with the catalyst, which was then evaporated to recover the catalyst. The pH of the aqueous phase was adjusted to 2–4 with dilute hydrochloric acid solution, at which point a large amount of pale yellow precipitate formed. The precipitate was filtered and dried completely in a vacuum oven at 80°C to obtain 4-phenylethynyl phthalic acid product.

[0065] (2) Weigh a certain amount of the 4-phenylethynyl phthalic acid obtained above and place it in a flask containing acetic anhydride, with a concentration of 7 mL / g. Place the reaction system in a water bath at 110 °C and react for 3 h. After the reaction is complete, evaporate the acetic anhydride by rotary evaporation, add a mixture of toluene / n-hexane (V:V = 1:2), and recrystallize to obtain 4-phenylethynyl phthalic anhydride.

[0066] The obtained 4-phenylethynyl phthalic acid has a high yield and purity, such as Figure 2 As shown, the yield was 98.58%, and the purity was measured by HPLC using an Agilent 1260 HPLC system. A gradient concentration method was used, with a test time of 20 min and a detection wavelength of 254 nm. The purity was measured to be 98.58%. The liquid NMR spectrum of the 4-phenylethynyl phthalic anhydride product prepared in this invention was completely consistent with the spectrum of standard 4-phenylethynyl phthalic anhydride, indicating that the product prepared in this invention is the target product, with a yield of 98.24%. Purity was again measured by HPLC, with only mobile phase A and other conditions unchanged, yielding a purity of 98.37%.

[0067] Example 4

[0068] This embodiment provides a 4-phenylacetylene phthalic anhydride and its preparation method, the preparation method comprising:

[0069] (1) 4-Bromophthalic anhydride (0.44 mol), triphenylphosphine, cuprous iodide, and palladium dichloride dichloride (1:1.05:1) were dissolved in anhydrous dimethylacetamide (400 mL). The amount of triphenylphosphine, cuprous iodide, and palladium dichloride dichloride added was 0.13% of the amount of 4-bromophthalic anhydride. Then, phenylacetylene (0.50 mol) and triethylamine (1.32 mol, 2.2 times the amount of 4-bromophthalic anhydride) were added. Oxygen was removed by a three-stage purging and venting process. The reaction system was then transferred to an oil bath, and the reaction temperature was set to 100 °C for 5 h. The mixture was then cooled to room temperature. The reaction solution was filtered, and water was added until a brick-red flocculent precipitate appeared. Ethyl acetate was added for extraction three times, retaining the organic and aqueous phases respectively. The organic phase was enriched with the catalyst, and the ethyl acetate could then be separated for catalyst recovery. The pH of the aqueous phase was adjusted to 2–4 with dilute hydrochloric acid solution, at which point a large amount of pale yellow precipitate formed. The precipitate was filtered and dried completely in a vacuum oven at 80°C to obtain 4-phenylethynyl phthalic acid product.

[0070] (2) Weigh a certain amount of the 4-phenylethynyl phthalic acid obtained above and place it in a flask containing acetic anhydride, with a concentration of 8 mL / g. Place the reaction system in an oil bath at 120℃ and react for 2.2 h. After the reaction is complete, separate the acetic anhydride using a rotary evaporator, add a mixture of toluene / n-hexane (V:V = 1:1.5), and recrystallize to obtain 4-phenylethynyl phthalic anhydride.

[0071] The obtained 4-phenylethynyl phthalic acid has a high yield and purity, such as Figure 2 As shown, the yield was 96.53%, and the purity was measured by HPLC using an Agilent 1260 HPLC system. A gradient concentration method was used, with a test time of 20 min and a detection wavelength of 254 nm. The purity was measured to be 98.72%. The liquid NMR spectrum of the 4-phenylethynyl phthalic anhydride product prepared in this invention was completely consistent with the spectrum of standard 4-phenylethynyl phthalic anhydride, indicating that the product prepared in this invention is the target product, with a yield of 97.84%. Purity was again tested by HPLC, and the purity was measured to be 98.45%.

[0072] Example 5

[0073] This embodiment provides a 4-phenylacetylene phthalic anhydride and its preparation method, the preparation method comprising:

[0074] (1) 4-Bromophthalic anhydride (0.44 mol), triphenylphosphine, cuprous iodide, and palladium dichloride dichloride (1:1.07:1) were dissolved in anhydrous dimethylacetamide (400 mL). The amount of triphenylphosphine, cuprous iodide, and palladium dichloride dichloride added was 0.2% of the amount of 4-bromophthalic anhydride. Then, phenylacetylene (0.53 mol) and triethylamine (1.32 mol, 2.2 times the amount of 4-bromophthalic anhydride) were added. Oxygen was removed by a three-stage purging and venting process. The reaction system was then transferred to an oil bath, and the reaction temperature was set to 120 °C for 4 h. The mixture was then cooled to room temperature. The reaction solution was filtered, and water was added until a brick-red flocculent precipitate appeared. Ethyl acetate was added for extraction three times, retaining the organic and aqueous phases respectively. The organic phase was enriched with the catalyst, and the ethyl acetate could then be separated for catalyst recovery. The pH of the aqueous phase was adjusted to 2–4 with dilute hydrochloric acid solution, at which point a large amount of pale yellow precipitate formed. The precipitate was filtered and dried completely in a vacuum oven at 80°C to obtain 4-phenylethynyl phthalic acid product.

[0075] (2) Weigh a certain amount of the 4-phenylethynyl phthalic acid obtained above and place it in a flask containing acetic anhydride, with a concentration of 8 mL / g. Place the reaction system in an oil bath at 140℃ and react for 2.8 h. After the reaction is complete, separate the acetic anhydride, add a mixture of toluene / n-hexane (V:V = 1:1.5), and recrystallize to obtain 4-phenylethynyl phthalic anhydride.

[0076] The obtained 4-phenylethynyl phthalic acid has a high yield and purity, such as Figure 2 As shown, the yield was 98.24%, and the purity was measured by HPLC using an Agilent 1260 HPLC system. The test employed a gradient concentration method, with a test time of 20 min and a detection wavelength of 254 nm. The purity was measured to be 98.57%. The liquid NMR spectrum of the 4-phenylethynyl phthalic anhydride product prepared in this invention was completely consistent with the spectrum of standard 4-phenylethynyl phthalic anhydride, indicating that the product prepared in this invention is the target product, with a yield of 97.43%. Purity was again tested by HPLC, and the purity was measured to be 98.36%.

[0077] Comparative Example 1

[0078] This comparative example provides a 4-phenylethynyl phthalic anhydride and its preparation method, the preparation method comprising:

[0079] A 500 ml flask equipped with a nitrogen inlet tube, a spherical condenser, a drying tube, a dropping funnel, and a magnetic stirrer was first evacuated, and the air was replaced with nitrogen three times. Under the nitrogen atmosphere, 27.24 g (0.12 mol) of 4-bromophthalic anhydride, 0.1 g (0.52 mmol) of cuprous iodide, 0.1 g (0.15 mmol) of dichlorobis(triphenylphosphine) with palladium, 0.24 g (0.92 mmol) of triphenylphosphine, and 380 ml of dry triethylamine were added to the three-necked flask. The mixture was stirred and heated. At 85 °C, 13.5 g (0.13 mol) of phenylacetylene dissolved in 10 mL of triethylamine was added dropwise over 1 hour. After the addition was complete, the mixture was heated and stirred for 20 hours to precipitate triethylamine. The precipitate was then filtered, and all solids were combined. The solids were mixed with 70 ml (0.74 mol) of acetic anhydride, stirred, and heated under reflux for 30 minutes to remove acetic acid and acetic anhydride. Then, 70 ml of toluene and an equal volume of n-hexane were added for recrystallization to obtain 4-phenylacetylene phthalic anhydride with a dry weight of 26.8 g, a yield of 90.1%, and a melting point of 151.8 °C.

[0080] The applicant declares that this invention illustrates a method for preparing 4-phenylethynyl phthalic anhydride through the above embodiments, but this invention is not limited to the above embodiments, that is, it does not mean that this invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to this invention, equivalent substitutions of the raw materials for the product of this invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of this invention.

Claims

1. A method for preparing 4-phenylethynyl phthalic anhydride, characterized in that, The preparation method includes: (1) 4-Halophthalic anhydride reacts with phenylacetylene in the presence of a catalyst at a temperature of 80-120℃ for 4-6 h. After cooling, first filtration, extraction, pH adjustment, second filtration, washing, and drying, 4-phenylacetylene-based phthalic acid is obtained. (2) The 4-phenylethynyl phthalic acid obtained in step (1) is reacted with acetic anhydride at a reaction temperature of 90-140℃ for 2-3 h. The mixture is then concentrated, recrystallized, filtered, and dried to obtain the 4-phenylethynyl phthalic anhydride. The catalyst in step (1) is a combination of palladium dichloride, cuprous iodide and triphenylphosphine in a molar ratio of 1:(1-1.1):1; The molar amount of the catalyst is 0.1-0.25% of the molar amount of 4-phenylethynyl phthalic anhydride; The reaction described in step (1) is carried out in the presence of the acid-binding agent triethylamine and the first solvent; The molar ratio of the acid-binding agent to 4-halophthalic anhydride is (2-3):1; Based on a mass of 1g of 4-halophthalic anhydride, the volume of the first solvent is 20-40 mL.

2. The preparation method according to claim 1, characterized in that, The molar ratio of 4-halophthalic anhydride to phenylacetylene in step (1) is 1:(1-1.2).

3. The preparation method according to claim 1, characterized in that, The 4-halogenated phthalic anhydride includes 4-bromophthalic anhydride.

4. The preparation method according to claim 1, characterized in that, Step (1) The first solvent is any one or a combination of at least two of anhydrous dimethylformamide, dimethylacetamide or dimethyl sulfoxide.

5. The preparation method according to claim 1, characterized in that, The reaction described in step (1) is carried out under the protection of an inert gas.

6. The preparation method according to claim 5, characterized in that, The inert gas is nitrogen and / or argon.

7. The preparation method according to claim 1, characterized in that, The first filtration is performed after adding water to precipitate the sediment.

8. The preparation method according to claim 7, characterized in that, The volume of water is 10-15 mL, based on a mass of 1 g of 4-halophthalic anhydride.

9. The preparation method according to claim 1, characterized in that, The extraction is performed by dissolving the substance in an extractant.

10. The preparation method according to claim 1, characterized in that, The extractant is any one or a combination of at least two of dichloromethane, ethyl acetate, or chloroform.

11. The preparation method according to claim 1, characterized in that, The pH was adjusted by adding hydrochloric acid solution to bring it to 2-4.

12. The preparation method according to claim 1, characterized in that, Based on a mass of 1g of 4-halophthalic anhydride, the volume of the acetic anhydride in step (2) is 3-10 mL.

13. The preparation method according to claim 1, characterized in that, The concentrated solution is dissolved in a second solvent and then recrystallized.

14. The preparation method according to claim 1, characterized in that, The second solvent is any one or a combination of at least two of anhydrous toluene, n-hexane, or diethyl ether.

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