Process for the synthesis of benzodifuran diones and derivatives thereof

Abstract

The application discloses a synthesis method of benzodifuran dione and derivatives thereof, and belongs to the field of synthesis of conductive polymers. The method takes hydroquinone and derivatives thereof as basic raw materials, and is characterized in that: the hydroquinone and derivatives thereof are first reacted with 3-chloropropylene under alkaline conditions, and then subjected to a Claisen rearrangement to generate an intermediate, and then subjected to a Criegee rearrangement under the action of ozone to generate benzodifuran dione or derivatives thereof. The method establishes a stable, simple and efficient synthesis process of benzodifuran dione through rearrangement and oxidation reactions, provides guarantee for stable supply of polybenzodifuran dione materials and high conductivity and other performances, and lays an important foundation for a next-generation high-performance and sustainable organic electronic material system.

Description

Technical Field

[0001] This invention belongs to the field of conductive polymer synthesis, and particularly relates to a method for synthesizing benzodifurandione and its derivatives. Background Technology

[0002] Polybenzodifurandione (PBFDO) has attracted widespread attention as an emerging n-type organic conductive polymer. Its unique electronic structure endows the material with low LUMO energy level, high framework planarity, and excellent π–π stacking ability, making PBFDO superior to traditional n-type materials in terms of air stability, charge transfer efficiency, and environmental adaptability. It also shows great application potential in fields such as flexible electronics, energy storage, optoelectronic devices, and bioelectronics.

[0003] However, the superior performance of PBFDO is highly dependent on the synthetic purity of its monomer, benzodifurandione (BFDO). The monomer purity of BFDO determines the activity of the polymerization reaction, the size of the polymer chain segments, and the degree of defects in the skeletal structure, which in turn directly affects the energy level positions, crystallinity, and electrical conductivity of PBFDO. Therefore, a high-purity, controllable functionalization BFDO monomer synthesis process is a key prerequisite for promoting the high performance and industrial application of PBFDO.

[0004] Currently, the synthesis of BFDO monomers remains challenging. The traditional route uses ethyl cyanoacetate and p-benzoquinone as starting materials, and obtains them through three steps. J. Am. Chem. Soc. 2013, 135, 33, 12168–12171). However, this route has obvious problems: (1) The steps are complicated, the overall synthesis yield is low, and the use of toxic reagents such as toluene and acetic anhydride is not conducive to large-scale production; (2) This route is not compatible with functional groups. When different substituents such as halogen atoms or methoxy groups are introduced on the benzene ring to regulate molecular energy levels and solubility, side reactions or poor selectivity often occur; (3) The side reaction products have similar physical properties to BFDO and are not easy to separate and purify, which leads to the inability to guarantee the purity of monomers, thereby affecting the batch stability of products and subsequent polymerization reactions. Recently, CN 120230117 A proposed the synthesis of BFDO by metal catalysis of hydroquinone, paraformaldehyde and carbon monoxide. Although the reaction steps have been simplified, the use of flammable and explosive gas carbon monoxide and the selection of high-pressure containers have put forward strict requirements for industrial scale-up production, which is not conducive to green and industrial development. Therefore, research on novel and efficient synthetic methods, structural modification, and large-scale production of BFDO monomers is of great significance.

[0005] In summary, the synthesis of BFDO monomers is not only the basic link for the development of PBFDO materials, but also the core factor determining the performance, reliability and application value of PBFDO materials. Therefore, how to further develop new synthetic routes, optimize catalyst systems, and improve yield and purity will provide a solid guarantee for the wide application of PBFDO in the field of organic conductive polymers, and lay an important foundation for building the next generation of high-performance and sustainable organic electronic material systems. SUMMARY

[0006] In order to overcome the problems of complicated synthesis steps, low yield, poor functional group compatibility and difficult separation and purification of BFDO in the prior art, the purpose of the present application is to provide an efficient synthesis method of benzodifuran dione and its derivatives. The method takes hydroquinone and its derivatives as basic raw materials, and establishes a stable, simple and efficient BFDO synthesis process through rearrangement reaction and oxidation reaction, which provides guarantee for the stable supply of PBFDO materials, high conductivity and other performances, and lays an important foundation for the next generation of high-performance and sustainable organic electronic material systems.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

[0008] A synthesis method of benzodifuran dione and its derivatives, comprising the following steps:

[0009] (1) In a polar solvent, a compound of formula I is used as a raw material to react with 3-chloropropene under alkaline conditions to generate an intermediate of formula II through Claisen rearrangement;

[0010]

[0011] Formula I Formula II Formula III

[0012] wherein R1 and R2 can be the same or different substituents, which can be hydrogen atom, halogen, cyano, nitro, alkyl, alkoxy, halogen-substituted alkyl, alkenyl or silicon-protected ethynyl group, etc.; the halogen is selected from F, Cl, Br and I; the alkyl is preferably a straight-chain or branched C1-C6 alkyl, such as methyl, ethyl, propyl, isopropyl, butyl, etc.; the alkoxy is preferably a C1-C6 alkoxy, such as methoxy, ethoxy; the halogen-substituted alkyl is preferably a halogen-substituted C1-C6 straight-chain or branched alkyl, such as halogen-substituted methyl, ethyl, propyl, isopropyl, butyl, etc.; the alkenyl is preferably a C2-C6 alkenyl; the silicon-protected group in the silicon-protected ethynyl group is preferably one or more of trimethylsilyl (TMS), triethylsilyl (TES), tert-butyldimethylsilyl (TBS), triisopropylsilyl (TIPS), tert-butyldiphenylsilyl (TBDPS).

[0013] (2) the intermediate of formula II is subjected to a Claisen rearrangement under the action of ozone to generate a benzodifuran dione or a derivative thereof shown as formula III.

[0014] The reaction path has the characteristics of simple synthesis process, less by-products and high yield, and the obtained crude product only needs to be simply purified to obtain the final product BFDO or a derivative thereof. Compared with the existing production process, the BFDO synthesis method provided by the application can greatly shorten the reaction steps, the raw materials are simple and easy to obtain, the waste is greatly reduced, the post-treatment is simple, and the method is suitable for large-scale batch production and commercial application. And the synthesis method of the application has strong universality, and also has similar high product purity, stable quality and large-scale production characteristics for similar derivatives of BFDO.

[0015] In some embodiments of the application, step (1) is specifically: in an alcohol solvent, using a compound of formula I as a raw material, adding an alkaline metal compound, then adding a 3-chloropropene solution under stirring, then heating and reacting, stirring the obtained product in a high-boiling solvent at high temperature to cause a Claisen rearrangement, and obtaining an intermediate of formula II.

[0016] The alcohol solvent is, for example, one or more of methanol, ethanol, butanol, isopropanol, heptanol, etc.; and the alkaline metal compound is, for example, one or more of sodium methoxide, sodium ethoxide, potassium carbonate, sodium carbonate, cesium carbonate, sodium bicarbonate, potassium tert-butoxide, and sodium tert-butoxide.

[0017] Preferably, the molar ratio of the compound of formula I, the alkaline metal compound and 3-chloropropene is 1.0 : (0.1-4) : (0.1-5.5).

[0018] Further, sodium iodide is added to the reaction system in step (1) to activate 3-chloropropene by halogen exchange reaction with iodine ions to improve the reactivity. The sodium iodide as a halogen exchange activator can also be replaced by any one of potassium iodide, lithium iodide, lithium bromide, sodium bromide, potassium bromide and other alkali metal halides, and the amount thereof is usually 0.1-3 equivalents of the substrate, and more preferably 0.1-1.5 equivalents of the substrate.

[0019] Further, in step (1), when the sodium methoxide or other alkali metal compound and the compound of formula I are mixed in an alcohol solvent, the temperature of the system will gradually rise, and the frequency and amount of addition of the alkali metal compound need to be controlled to ensure that the temperature of the system is below 50°C. Then, the 3-chloropropene solution is added dropwise under mixing and stirring, ensuring that the addition is completed in 0.1-1.5 h, and then the temperature is raised to 65-85°C and the reaction is stirred for 4-8 h. After the reaction is completed, the temperature of the system is reduced to room temperature, a strong alkaline aqueous solution (such as an aqueous solution of sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, or barium hydroxide) is added to dissolve the precipitate, an organic solvent is added for extraction, the solvent is concentrated, the crude product is gradually precipitated from the system solvent, filtered, washed, and dried, and then the obtained solid is stirred in a high-boiling solvent such as o-dichlorobenzene, dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, or the like at 100-180°C to undergo Claisen rearrangement, to obtain the intermediate of formula II.

[0020] In some embodiments of the present application, step (2) is specifically: ozone is introduced into an inert solvent system containing the intermediate of formula II under low temperature conditions; after the reaction is completed, nitrogen is introduced to replace the ozone to inertize the system; then, a small amount of reducing agent is added to the reaction liquid or no reducing agent is added, the system is heated and stirred after it is detected that there is no residual ozone, to obtain the product of formula III, i.e. benzodifuran dione or a derivative thereof.

[0021] Further, the low temperature in step (2) is usually -78-20°C.

[0022] Further, the inert solvent in step (2) can be a halogenated hydrocarbon solvent such as dichloromethane, chloroform, carbon tetrachloride, 1,2-dichloroethane, or the like; an ester solvent such as ethyl acetate, butyl acetate, or the like; or a hydrocarbon solvent such as n-hexane, n-heptane, toluene, or the like. Preferably, the inert solvent is one or more of dichloromethane, toluene, dichloroethane, or the like.

[0023] Further, in step (2), the molar ratio of the intermediate of formula II, ozone, and reducing agent is 1.0 : (2.0-10) : (0-0.5).

[0024] Further, in step (2), a small amount of defoaming agent (commonly polysiloxane defoaming agent such as polydimethylsiloxane) is usually added to the inert solvent system containing the intermediate of formula II before ozone is introduced to complete defoaming. Then, ozone is introduced and the temperature is kept low for 2-6 h.

[0025] Further, the reducing agent used in step (2) can be zinc sulfate, sodium bisulfite, sodium sulfite, sulfur dioxide, sodium iodide, zinc powder, dimethyl sulfide, triphenylphosphine, tert-butyl mercaptan, methyl mercaptan, pyridine mercaptan, sodium borohydride, lithium aluminum hydride, or the like. Preferably, the reducing agent is selected from one or more of sodium iodide, zinc powder, and triphenylphosphine.

[0026] Further, the temperature is usually increased to 60-100 DEG C after adding the reducing agent in step (2), and the reaction is stirred for 6-18 hours. After the reaction is completed, the organic phase is collected, and the crude product powder is obtained after concentration. The pure product BFDO or its derivative is obtained after multiple washing with a hot solution of ethyl acetate and ethanol.

[0027] The synthesis method of the benzodifuran dione and its derivative provided by the application has the advantages of short reaction route, high yield, easy purification, etc., and the synthesis method does not require high-pressure equipment, reduces the cost of enterprises, and is convenient for process amplification synthesis. Compared with the prior art, the application has the following beneficial effects:

[0028] (1) The synthesis method of the novel benzodifuran dione and its derivative provided by the application has simple and easily obtained raw materials, greatly reduced waste, simple post-treatment, and is suitable for commercial application.

[0029] (2) The synthesis method provided by the application has strong universality, and has similar high product purity, stable quality, and the characteristics of being beneficial to large-scale production for the same derivative of BFDO. The method provides a possibility for further structural modification and application exploration of the polymer PBFDO. BRIEF DESCRIPTION OF DRAWINGS

[0030] Figure 1 The reaction formula of the synthesis method of the benzodifuran dione and its derivative of the application.

[0031] Figure 2 The nuclear magnetic resonance hydrogen spectrum of the benzodifuran dione synthesized in Example 2 of the application.

[0032] Figure 3 The high-performance liquid chromatography analysis result of the benzodifuran dione synthesized in Example 2 of the application. DETAILED DESCRIPTION

[0033] The application will be further described in detail below in combination with examples, but the implementation manner of the application is not limited to this.

[0034] Example 1

[0035]

[0036] To 10 g (0.09 mol) of p-hydroquinone dissolved in 100 mL of ethanol, 18.2 g (30%, 0.1 mol) of sodium methoxide in ethanol was added dropwise over 10 minutes. The temperature of the system gradually increased during the addition, and the temperature of the system was maintained below 50°C. After the addition was complete, the reaction system was heated to 75°C at the end of the addition. After stirring for 15 minutes, 1.59 g (0.01 mol) of sodium iodide was added, followed by the addition of 19.6 g (0.26 mol) of 3-chloropropene over 10 minutes. At this time, sodium chloride precipitated in the reaction system. After stirring at 75°C for 4 hours, the solvent was distilled off, cooled to room temperature, and 200 mL (10%, 0.5 mol) of NaOH solution was added, and the original precipitate was dissolved. After layering with the addition of methyl tert-butyl ether (MTBE), the aqueous phase was extracted twice with MTBE, and the organic phases were combined. The organic phase was washed with a weak acid solution, dried over anhydrous sodium sulfate, and filtered. After removing the solvent, 12.71 g of a crude product was obtained. The crude product was then added to a reaction device containing 130 mL of o-dichlorobenzene, and heated and stirred at 120°C for 12 hours. After cooling to room temperature, the solvent was removed by rotary evaporation, and washed several times with ethanol to obtain 12.3 g of pure 2,5-diallylhydroquinone (yield: 72%).

[0037] In a 500 mL reaction kettle, 11.4 g (0.06 mol) of 2,5-diallylhydroquinone was dissolved in 250 mL of dichloromethane, cooled to 5°C, and 0.1 g of polydimethylsiloxane (PDMS) was added as a defoaming agent and stirred for 10 minutes. Then, 5.76 g (0.12 mol) of ozone was introduced for reaction. After the ozonation reaction was completed, the ozone was stopped, and nitrogen was introduced for 15 minutes to completely inert the system. Subsequently, the reaction mixture was transferred to a two-necked flask with a reflux condenser, heated to 60°C, and the progress of the reaction was monitored using thin layer chromatography (TLC). After the reaction was completed, the reaction liquid was concentrated to obtain 11.3 g of a crude product. Thereafter, the crude product was washed several times with a mixture of ethyl acetate and ethanol (volume ratio 1:3) to obtain 10.15 g of pure benzodifuran-dione (yield: 89%).

[0038] Example 2

[0039]

[0040] The synthesis of 2,5-diallylhydroquinone was the same as in Example 1. Subsequently, in a 500 mL reactor, 11.4 g (0.06 mol) of 2,5-diallylhydroquinone was dissolved in 250 mL of dichloromethane, cooled to 5°C, and 0.1 g of polydimethylsiloxane (PDMS) was added as an antifoaming agent and stirred for 10 minutes. Then, 5.76 g (0.12 mol) of ozone was introduced to initiate the reaction. After the ozonation reaction was complete, the ozone introduction was stopped, and nitrogen gas was bubbled in for 15 minutes to completely inertize the system. The reaction mixture was then transferred to a two-necked flask equipped with a reflux condenser, and 3.15 g (0.012 mol) of triphenylphosphine was added. The system temperature was then raised to 60°C, and the reaction progress was monitored using thin-layer chromatography (TLC). After the reaction was complete, the reaction solution was concentrated to obtain 12.7 g of crude product. After washing several times with a mixture of ethyl acetate and ethanol (volume ratio 1:3), 10.95 g of pure benzodifurandione was obtained (yield: 96%).

[0041] The proton NMR spectrum of the product benzodifurandione is shown below. Figure 2 As shown, using deuterated chloroform as solvent, two singlets appeared at 7.069 ppm and 3.783 ppm, with corresponding integrals of 2 and 4, corresponding to the number of hydrogen atoms in the benzene ring and methylene group of benzodifuran dione. Furthermore, the 1H NMR spectrum was clean with no obvious impurity peaks, consistent with the results of high-performance liquid chromatography (HPLC). Figure 3 The results indicate that the obtained product, benzodifurandione, has a purity of 99.78%, making it suitable for subsequent polymerization reactions.

[0042] Example 3

[0043]

[0044] To 10 g (0.09 mol) of p-hydroquinone dissolved in 100 mL of ethanol, 36.4 g (30%, 0.2 mol) of sodium methoxide in ethanol was added dropwise over a period of 10 minutes. The temperature of the system gradually increased during the addition, and the temperature of the system was maintained below 50°C. After the addition was complete, the reaction system was heated to 75°C at the end of the addition. After stirring for 15 minutes, 1.59 g (0.01 mol) of sodium iodide was added, followed by the addition of 19.6 g (0.26 mol) of 3-chloropropene over a period of 10 minutes. At this time, sodium chloride precipitated in the reaction system. After stirring at 75°C for 4 hours, the solvent was distilled off, cooled to room temperature, and 200 mL (10%, 0.5 mol) of NaOH solution was added, and the original precipitate was dissolved. After the addition of methyl tert-butyl ether (MTBE), the layers were separated, and the aqueous phase was extracted twice with MTBE, and the organic phases were combined. The organic phase was washed with a weak acid solution, dried over anhydrous sodium sulfate, and filtered. After removing the solvent, 14.71 g of a crude product was obtained. The crude product was then added to a reaction device containing 150 mL of o-dichlorobenzene, and heated and stirred at 120°C for 12 hours. After cooling to room temperature, the solvent was removed by rotary evaporation, and washed several times with ethanol to obtain 14.6 g of pure 2,5-diallylhydroquinone (yield: 85%).

[0045] In a 500 mL reaction kettle, 11.4 g (0.06 mol) of 2,5-diallylhydroquinone was dissolved in 250 mL of dichloromethane, cooled to 5°C, and 0.1 g of polydimethylsiloxane (PDMS) was added as a defoaming agent and stirred for 10 minutes. Then, 5.76 g (0.12 mol) of ozone was introduced for reaction. After the ozonation reaction was completed, the ozone was stopped, and nitrogen was introduced for 15 minutes to completely inert the system. Subsequently, the reaction mixture was transferred to a two-necked flask with a reflux condenser, 3.15 g (0.012 mol) of triphenylphosphine was added, and the temperature of the system was increased to 60°C, and the progress of the reaction was monitored using thin layer chromatography (TLC). After the reaction was completed, the reaction liquid was concentrated to obtain 12.7 g of a crude product. Subsequently, the crude product was washed several times with a mixture of ethyl acetate and ethanol (volume ratio 1:3) to obtain 10.95 g of pure benzodifuran dione (yield: 96%).

[0046] Example 4

[0047]

[0048] To 12.43 g (0.09 mol) of 2,5-dimethyl-1,4-benzene diol dissolved in 100 mL of ethanol, 36.4 g (30%, 0.2 mol) of sodium methoxide in ethanol was added dropwise over 10 minutes. The temperature of the system gradually increased during the addition, and the temperature of the system was maintained below 50°C. After the addition was complete, the reaction system was heated to 75°C at the end of the addition. After stirring for 15 minutes, 1.59 g (0.01 mol) of sodium iodide was added, followed by the addition of 19.6 g (0.26 mol) of 3-chloropropene over 10 minutes. At this time, sodium chloride precipitated in the reaction system. After stirring at 75°C for 4 hours, the solvent was evaporated, and the system was cooled to room temperature. Then, 200 mL (10%, 0.5 mol) of NaOH solution was added, and the original precipitate was dissolved. After the addition of methyl tert-butyl ether (MTBE), the layers were separated, and the aqueous phase was extracted twice with MTBE. The organic phases were combined, washed with a weak acid solution, dried over anhydrous sodium sulfate, and filtered. After the removal of the solvent, 10.71 g of a crude product was obtained. The crude product was then added to a reaction apparatus containing 110 mL of o-dichlorobenzene, and the system was heated at 120°C with stirring for 12 hours. After cooling to room temperature, the solvent was removed by rotary evaporation, and the product was washed with ethanol several times to obtain 9.6 g of pure 2,5-diallyl-3,6-dimethylbenzene-1,4-diol (yield: 49%).

[0049] In a 500 mL reaction vessel, 13 g (0.06 mol) of 2,5-diallyl-3,6-dimethylbenzene-1,4-diol was dissolved in 250 mL of dichloromethane, cooled to 5°C, and 0.1 g of polydimethylsiloxane (PDMS) was added as a defoaming agent and stirred for 10 minutes. Then, 5.76 g (0.12 mol) of ozone was introduced to perform the reaction. After the ozonolysis reaction was completed, the ozone introduction was stopped, and nitrogen was introduced for 15 minutes to completely inert the system. Subsequently, the reaction mixture was transferred to a two-necked flask equipped with a reflux condenser, 3.15 g (0.012 mol) of triphenylphosphine was added, and the temperature of the system was increased to 60°C. The progress of the reaction was monitored using thin layer chromatography (TLC). After the completion of the reaction, the reaction liquid was concentrated to obtain 12.1 g of a crude product. Subsequently, the crude product was washed with a mixture of ethyl acetate and ethanol (volume ratio 1:3) several times to obtain 11.64 g of pure dimethyl-substituted benzodifuran dione (yield: 89%).

[0050] Example 5

[0051]

[0052] To 16.02 g (0.09 mol) of 2,5-dichlorohydroquinone dissolved in 100 mL of ethanol, 36.4 g (30%, 0.2 mol) of sodium methoxide in ethanol was added dropwise over 10 minutes. The temperature of the system gradually increased during the addition, and the temperature was maintained below 50°C. After the addition was complete, the reaction system was heated to 75°C at the end of the addition. After stirring for 15 minutes, 1.59 g (0.01 mol) of sodium iodide was added, followed by the addition of 19.6 g (0.26 mol) of 3-chloropropene over 10 minutes. At this time, sodium chloride precipitated in the reaction system. After stirring at 75°C for 4 hours, the solvent was evaporated, and the temperature was cooled to room temperature. A 200 mL (10%, 0.5 mol) NaOH solution was added, and the original precipitate was dissolved. After the addition of methyl tert-butyl ether (MTBE), the layers were separated, and the aqueous phase was extracted twice with MTBE. The organic phases were combined, washed with a weak acid solution, dried over anhydrous sodium sulfate, and filtered. After removing the solvent, 9.65 g of a crude product was obtained. The crude product was then added to a reaction apparatus containing 100 mL of o-dichlorobenzene, and the mixture was heated and stirred at 120°C for 12 hours. After cooling to room temperature, the solvent was removed by rotary evaporation, and the product was washed several times with ethanol to obtain 8.59 g of pure 2,5-diallyl-3,6-dichlorobenzene-1,4-diol (yield: 37%).

[0053] In a 500 mL reaction kettle, 15.48 g (0.06 mol) of 2,5-diallyl-3,6-dichlorobenzene-1,4-diol was dissolved in 250 mL of dichloromethane, cooled to 5°C, and 0.1 g of polydimethylsiloxane (PDMS) was added as a defoaming agent and stirred for 10 minutes. Then, 5.76 g (0.12 mol) of ozone was introduced for the reaction. After the ozonation reaction was completed, the ozone introduction was stopped, and nitrogen was introduced for 15 minutes to completely inert the system. Subsequently, the reaction mixture was transferred to a two-necked flask with a reflux condenser, 3.15 g (0.012 mol) of triphenylphosphine was added, and the temperature of the system was increased to 60°C. The progress of the reaction was monitored using thin layer chromatography (TLC). After the reaction was completed, the reaction liquid was concentrated to obtain 12.9 g of a crude product. Subsequently, the crude product was washed several times with a mixture of ethyl acetate and ethanol (volume ratio 1:3) to obtain 11.45 g of pure dichloro-substituted benzodifuran dione (yield: 74%).

[0054] Example 6

[0055]

[0056] To 10 g (0.09 mol) of p-hydroquinone dissolved in 300 mL of ethanol, 27.6 g (0.2 mol) of anhydrous potassium carbonate and 19.6 g (0.26 mol) of 3-chloropropene were added, and the mixture was stirred at 75°C under reflux for 12 hours. After that, it was cooled to room temperature, layered after adding methyl tert-butyl ether (MTBE), the aqueous phase was extracted twice with MTBE, and the organic phases were combined. The organic phase was washed with a weakly acidic solution, dried over anhydrous sodium sulfate, and filtered. After removing the solvent, 16.91 g of a crude product was obtained. The crude product was then added to a reaction apparatus containing 150 mL of o-dichlorobenzene, and the mixture was stirred at 120°C for 12 hours. After that, it was cooled to room temperature, the solvent was distilled off, and the product was washed with ethanol several times to obtain 15.4 g of pure 2,5-diallylhydroquinone (yield: 90%).

[0057] In a 500 mL reaction vessel, 11.4 g (0.06 mol) of 2,5-diallylhydroquinone was dissolved in 250 mL of dichloromethane, cooled to 5°C, and 0.1 g of polydimethylsiloxane (PDMS) was added as an antifoaming agent and stirred for 10 minutes. Then, 5.76 g (0.12 mol) of ozone was introduced to perform the reaction. After the ozonolysis reaction was completed, the ozone introduction was stopped, and nitrogen was introduced for 15 minutes to completely inert the system. Subsequently, the reaction mixture was transferred to a two-necked flask equipped with a reflux condenser, 3.15 g (0.012 mol) of triphenylphosphine was added, and the temperature of the system was increased to 60°C. The progress of the reaction was monitored using thin layer chromatography (TLC). After the reaction was completed, the reaction liquid was concentrated to obtain 12.7 g of a crude product. After that, the crude product was washed with a mixture of ethyl acetate and ethanol (volume ratio 1:3) several times to obtain 10.95 g of pure benzodifuran-2,5-dione (yield: 96%).

[0058] Example 7

[0059]

[0060] To 15.3 g (0.09 mol) of p-hydroquinone dissolved in 300 mL of ethanol, 27.6 g (0.2 mol) of anhydrous potassium carbonate and 19.6 g (0.26 mol) of 3-chloropropene were added, and the mixture was stirred at 75°C under reflux for 12 hours. After that, it was cooled to room temperature, layered after adding methyl tert-butyl ether (MTBE), the aqueous phase was extracted twice with MTBE, and the organic phases were combined. The organic phase was washed with a weakly acidic solution, dried over anhydrous sodium sulfate, and filtered. After removing the solvent, 16.91 g of a crude product was obtained. The crude product was then added to a reaction apparatus containing 150 mL of o-dichlorobenzene, and the mixture was stirred at 75°C under reflux for 12 hours. After that, it was cooled to room temperature, the solvent was distilled off, and the product was washed with ethanol several times to obtain 15.4 g of pure 2,5-diallylhydroquinone (yield: 90%).

[0061] In a 500 mL reaction flask, 15 g (0.06 mol) of 2,5-diallyl-3,6-dimethoxybenzene-1,4-diol was dissolved in 250 mL of dichloromethane, cooled to 5 °C, and 0.1 g of polydimethylsiloxane (PDMS) was added as an antifoaming agent and stirred for 10 min. Then 5.76 g (0.12 mol) of ozone was bubbled into the reaction. After the ozonolysis reaction was completed, the ozone was stopped, and nitrogen was bubbled into the system for 15 min to completely inert the system. Subsequently, the reaction mixture was transferred to a two-necked flask with a reflux condenser, 1.80 g (0.012 mol) of sodium iodide was added, and the temperature of the system was raised to 60 °C, and the reaction progress was monitored using thin layer chromatography (TLC). After the reaction was completed, the reaction liquid was concentrated to obtain 12.4 g of a crude product. Then, the crude product was washed several times with a mixture of ethyl acetate and ethanol (volume ratio 1:3) to obtain 11.85 g of a pure dimethoxy-substituted benzodifuran dione (yield: 79%).

[0062] Comparative Example 1

[0063]

[0064] Into a 250 mL three-necked flask equipped with a constant pressure dropping funnel, 5 g of 1,4-benzoquinone (46 mmol) was added, followed by the addition of 11.25 g of aqueous ammonia (12.5 mL, 320.62 mmol). At the same time, a solution of 8.17 g of ethyl cyanoacetate (7.67 mL, 71.9 mmol) in 100 mL of ethanol was added dropwise at a uniform rate through the constant pressure dropping funnel into the three-necked flask. When the addition was completed, the resulting solution was stirred at room temperature for 1 h, during which a large amount of solid was precipitated. Filtration, washing with ethanol three times, and drying yielded 3.6 g of a dark purple solid with a yield of 24%, which was directly subjected to the next step.

[0065] Into a 250 mL two-necked flask, 3.6 g of the above-mentioned dark purple solid (10.8 mmol) was added, followed by the addition of 18 mL of water and 21.6 mL of concentrated hydrochloric acid (249 mmol), and refluxing at 110 °C for 20 h. After cooling to room temperature, a large amount of solid was precipitated, which was filtered to obtain 1.5 g of a milky white solid with a yield of 61%.

[0066] Into a 250 mL two-necked flask, 1.5 g of the above-mentioned milky white solid (6.6 mmol) was added, followed by the addition of 75 mL of toluene and 15 mL of acetic anhydride. Under nitrogen protection, the temperature was raised to 100 °C, and the reaction was carried out overnight. After the reaction was completed, the temperature was restored to room temperature, the reaction liquid was concentrated, and the obtained solid was transferred to a 100 mL single-necked flask, 50 mL of toluene was added, and refluxing was carried out for 1 h. After cooling to room temperature, the solid was allowed to precipitate, which was filtered to obtain 1 g of an off-white solid with a yield of 80%.

[0067] Comparative Example 2

[0068]

[0069] Into a 250 mL three-necked flask equipped with a constant pressure dropping funnel, 8.14 g of 2,5-dichloro-p-benzoquinone (46 mmol) was added, followed by the addition of 11.25 g of ammonia water (12.5 mL, 320.62 mmol). At the same time, a solution of 8.17 g of ethyl cyanoacetate (7.67 mL, 71.9 mmol) in 100 mL of ethanol was dropped into the flask through the constant pressure dropping funnel at a uniform speed. After the addition was completed, the resulting solution was stirred at room temperature for 1 hour, during which a large amount of solid was precipitated. Filtration, ethanol washing three times, and drying gave 2.76 g of purple solid, a yield of 15%, which was directly subjected to the next step.

[0070] Into a 250 mL two-necked flask, 4.32 g of the above-mentioned purple solid (10.8 mmol) was added, followed by the addition of 18 mL of water and 21.6 mL of concentrated hydrochloric acid (249 mmol), and refluxed at 110°C for 20 h. After cooling to room temperature, a small amount of solid was precipitated, which was filtered, and the 2,2'-(2,5-dichloro-3,6-dihydroxy-1,4-phenylene) diacetic acid intermediate in the second step was not obtained.

[0071] Table 1. Comparison of the yield of various reactions in the examples and comparative examples and the purity of the samples

[0072]

[0073] In summary, the reaction yield and product purity of the above examples and comparative examples are shown in Table 1, and by comparison, it can be seen that the synthesis route provided by the present application only needs two steps of synthesis, the yield of the product benzodifuran dione is as high as 86%, and the purity is 96.37% or even higher, while the yield of Comparative Example 1 is only 11.7% through three steps of experiment, and the purity is 83.52%, and the present application has a significant production advantage. At the same time, the raw materials provided by the present application are simple and easy to obtain, do not contain flammable, explosive and toxic hazardous chemicals such as toluene, acetic anhydride, concentrated hydrochloric acid, carbon monoxide, the amount of hazardous waste is greatly reduced, the post-treatment process is simple, and no high-pressure device container is needed, which is convenient for large-scale batch production. In addition, this reaction route also has good applicability to derivatives of benzodifuran dione, such as dimethyl, dimethoxy or chloro-substituted benzodifuran dione. The realization of the present application provides the possibility for further structural modification and application exploration of the polymer PBFDO.

Claims

1. A method for synthesizing benzodifurandione and its derivatives, comprising the following steps: Formula I Formula II Formula III 1) The compound of formula I reacts with 3-chloropropene under alkaline conditions, and the intermediate of formula II is generated by the Claisen rearrangement. The specific operation is as follows: In an alcohol solvent, the compound of formula I is used as a raw material, an alkaline metal compound is added, and 3-chloropropene solution is added while mixing and stirring. The reaction is then heated, and the resulting product is stirred in a high-boiling solvent at 100~180℃ to undergo the Claisen rearrangement and obtain the intermediate of formula II. The high-boiling solvent is selected from one or more of o-dichlorobenzene, dimethyl sulfoxide, N,N-dimethylformamide, and N-methylpyrrolidone. 2) The intermediate of Formula II undergoes Kriging rearrangement under the action of ozone to generate benzodifurandione or its derivatives as shown in Formula III. The specific operation is as follows: ozone is introduced into an inert solvent system containing the intermediate of Formula II at a low temperature of -78~20℃; after the reaction is completed, nitrogen is introduced to replace the system and inertize it; then, a small amount of reducing agent is added to the reaction solution or no reducing agent is added, and after detecting that there is no ozone residue, the temperature is raised and the reaction is stirred to obtain benzodifurandione or its derivatives as shown in Formula III. R1 and R2 are the same or different substituents, selected from hydrogen atoms, halogens, C1~C6 alkyl groups, and C1~C6 alkoxy groups.

2. The synthesis method according to claim 1, characterized in that, The alkaline metal compound mentioned in step 1) is selected from one or more of sodium methoxide, sodium ethoxide, potassium carbonate, sodium carbonate, cesium carbonate, sodium bicarbonate, potassium tert-butoxide, and sodium tert-butoxide; the molar ratio of the compound of formula I, the alkaline metal compound, and 3-chloropropene is 1.0 : (0.1~4) : (0.1~5.5).

3. The synthesis method as described in claim 1, characterized in that, In step 1), when the compound of formula I and the alkali metal compound are mixed in an alcohol solvent, the frequency and amount of addition of the alkali metal compound are controlled to ensure that the system temperature is below 50°C. Then, 3-chloropropene solution is added dropwise under stirring, ensuring that the addition is completed in 0.1~1.5 h. Then the temperature is raised to 65~85°C and stirred continuously for 4~8 h. The solvent is evaporated, and after cooling, the precipitate is dissolved in a strongly alkaline aqueous solution. An organic solvent is added for extraction, and the solvent is concentrated. The crude product gradually precipitates from the system solvent. It is filtered, washed, and dried. Then the obtained solid is stirred in a high-boiling-point solvent at 100~180°C to induce Claisen rearrangement, yielding intermediate of formula II.

4. The synthesis method according to claim 1, characterized in that, Step 1) Add a halogen exchange activator to the reaction system to activate 3-chloropropene.

5. The synthesis method according to claim 1, characterized in that, Step 2) The molar ratio of intermediate II, ozone and reducing agent is 1.0 : (2.0~10) : (0~0.5); the temperature of the heating and stirring reaction is 60~100℃ and the time is 6~18 h.

6. The synthesis method according to claim 1, characterized in that, Step 2) Before introducing ozone, add an antifoaming agent to the inert solvent system containing the intermediate of formula II to complete the defoaming, then introduce ozone and maintain it at low temperature for 2-6 hours.

7. The synthesis method according to claim 1, characterized in that, The inert solvent mentioned in step 2) is a halogenated hydrocarbon solvent, an ester solvent, or a hydrocarbon solvent; the reducing agent is selected from one or more of zinc sulfate, sodium bisulfite, sodium sulfite, sulfur dioxide, sodium iodide, zinc powder, dimethyl sulfide, triphenylphosphine, tert-butyl mercaptan, methanethiol, pyridine mercaptan, sodium borohydride, and lithium aluminum hydride.

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