A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutane tetra carboxylic dianhydride

Abstract

The application discloses a preparation method of 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutane tetra carboxylic dianhydride, which comprises the following steps: (1) uniformly stirring citraconic anhydride, ethyl acetate and a catalyst, and performing microwave continuous flow reaction; after the reaction is completed, filtration is performed to obtain 1,3-dmcbda crude product I; (2) adding acetic anhydride and stirring under heating, then reducing to room temperature, and performing filtration to obtain 1,3-dmcbda crude product II; then adding acetone, heating to reflux, then reducing to room temperature, and performing vacuum drying to obtain 1,3-dmcbda fine product. The preparation method can make the 1,3-dmcbda product have high yield and high purity, and is suitable for industrial production.

Description

TECHNICAL FIELD

[0001] The application relates to a preparation method of 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutane tetra carboxylic dianhydride, and belongs to the technical field of video playing. BACKGROUND

[0002] 1,3-dmcbda is an alicyclic dianhydride monomer for synthesizing polyimide; 1,3-dmcbda increases two methyl groups on a non-conjugated alicyclic structure, can further increase the molecular chain spacing of polyimide, improves the transparency, solubility and dielectric properties of polyimide, can meet the demand of photo-alignment film, and is widely applied in the field of photoelectric display.

[0003] The existing patents CN105916866B and CN109422762A report a method for producing 1,3-dmcbda from citraconic anhydride as raw material, but the yield of 1,3-dmcbda is low in the scheme calculated from the initial raw material, and the content of 1,2-dmcbda is still high, the economic benefit is low, and it is not conducive to industrial production; therefore, how to prepare 1,3-dmcbda with high yield and high purity is still a problem to be solved in the current industry. SUMMARY

[0004] At least in view of one problem existing in the prior art, the application provides a preparation method of 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutane tetra carboxylic dianhydride, which can make the 1,3-dmcbda product have high yield and high purity, and is suitable for industrial production.

[0005] In order to achieve the above-mentioned purpose, the application adopts the following technical scheme: a preparation method of 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutane tetra carboxylic dianhydride, comprising the following steps:

[0006] (1) citraconic anhydride, ethyl acetate and a catalyst are uniformly stirred, microwave continuous flow reaction is carried out in a mode of multiple cycles of first cooling and then microwave control of the reaction liquid, after the reaction is completed, filtration is carried out, and 1,3-dmcbda crude product I is obtained;

[0007] (2) acetic anhydride is added to the above-mentioned 1,3-dmcbda crude product I, stirring is carried out after heating, then the temperature is lowered to room temperature, filtration is carried out, and 1,3-dmcbda crude product II is obtained;

[0008] (3) acetone is added to the 1,3-dmcbda crude product II, heating reflux is carried out, then the temperature is lowered to room temperature, vacuum drying is carried out again, and 1,3-dmcbda fine product is obtained.

[0009] Preferably, in step (1), the specific conditions of the microwave continuous flow reaction are: the reaction solution is first cooled to -25 to -5°C, then the light wave frequency is controlled to 2350MHz±50Hz to 2550MHz±50Hz, the reaction temperature is 5 to 20°C, and the reaction is repeated for 15 to 48 hours.

[0010] Preferably, in step (1), the specific conditions of the microwave continuous flow reaction are: the reaction solution is first cooled to -20 to -10°C, then the light wave frequency is controlled to 2400MHz±50Hz to 2500MHz±50Hz, the reaction temperature is 10 to 15°C, and the reaction is cyclically reacted for 20 to 40 hours.

[0011] Preferably, in step (1), the catalyst is one of p-toluenesulfonic acid, benzenesulfonic acid, dimethylbenzenesulfonic acid, etc.

[0012] Preferably, in step (1), the catalyst is p-toluenesulfonic acid.

[0013] Preferably, in step (1), the amount of the catalyst added is 1 to 2.5% of the mass of citraconic anhydride.

[0014] Preferably, in step (2), the mass ratio of the added amount of acetic anhydride to the mass of citraconic anhydride is 0.5 to 5:1, preferably 2 to 4:1.

[0015] Preferably, in step (2), the conditions for heating and stirring are: temperature of 110-140° C. for 2-10 h; preferably, temperature of 115-130° C. for 3.5-6 h.

[0016] Preferably, in step (3), the mass ratio of the added amount of acetone to the crude 1,3-dmcbda product II is 3 to 10:1, preferably 3 to 6:1.

[0017] Preferably, in step (3), the reflux time is 1 to 5 hours, preferably 2.5 to 4 hours.

[0018] Preferably, in step (3), the vacuum drying temperature is 50-60°C.

[0019] Beneficial effects of the present invention:

[0020] (1) The preparation method of the present invention can obtain the product 1,3-dmcbda in high yield, with a yield greater than 50%, and the product has high purity, 1,3-dmcbda:1,2-dmcbda≥99.85:0.15.

[0021] (2) The present invention adopts a microwave continuous flow reaction, which is carried out in a multiple-cycle manner in which the reaction liquid is first cooled and then microwave-controlled, thereby increasing the production of 1,3-dmcbda and greatly reducing the production of 1,2-dmcbda isomers. Acetone is used to remove a small amount of residual 1,2-dmcbda by reflux, thereby obtaining a high-purity 1,3-dmcbda product.

[0022] (3) The ethyl acetate, acetic anhydride and acetone used in the present invention are safe, energy-saving and conducive to recycling.

[0023] (4) The present invention uses acetone reflux purification, which uses a small amount and is conducive to industrial scale-up production.

[0024] (5) The preparation method of the present invention has controllable process operation, simple technology, high product yield and purity, and is suitable for industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the NMR spectrum of the reaction solution of Example 1;

[0026] Figure 2 This is the NMR spectrum of the finished product 1,3-dmcbda of Example 1;

[0027] Figure 3 This is the NMR spectrum of the reaction solution of Comparative Example 3;

[0028] Figure 4 This is the NMR spectrum of the finished product 1,3-dmcbda of Comparative Example 3. DETAILED DESCRIPTION

[0029] Below in conjunction with accompanying drawing, the technical scheme in the embodiment of the present invention is clearly and completely described, and described embodiment is only a part of embodiment of the present invention, rather than all embodiments. Based on the embodiment of the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise all fall within the scope of protection of the present invention. In the embodiment, those who do not indicate specific conditions, carry out according to the conditions of normal conditions or manufacturer's advice. Reagents used or instruments, components that do not indicate manufacturer are conventional products that can be purchased commercially.

[0030] Example 1

[0031] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0032] (1) Add 7.5 kg of citraconic anhydride to 30 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10 ° C, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10 ° C, and repeat the reaction for 24 hours. Stop the reaction, filter, and obtain a white solid, i.e., 4.5 kg of crude 1,3-dmcbda I, with a yield of 60%;

[0033] (2) Add 30 kg of acetic anhydride to the crude product I, heat to 120 ° C and stir for 4 h, then cool to room temperature and filter to obtain 4 kg of crude 1,3-dmcbda II with a yield of 53.33%;

[0034] (3) 16 kg of acetone was added to the crude 1,3-dmcbda II, and the mixture was heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum-dried at 60 °C to obtain 3.82 kg of 1,3-dmcbda, a yield of 50.93%. The NMR spectrum of the reaction solution was as follows: Figure 1 As shown, the NMR spectrum of the product 1,3-dmcbda is as follows Figure 2 As shown, the ratio of 1,3-dmcbda to 1,2-dmcbda is 99.89:0.11; the yield in this example is calculated relative to citraconic anhydride.

[0035] Example 2

[0036] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0037] (1) Add 8 kg of citraconic anhydride to 36 kg of ethyl acetate, add 0.16 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -15 ° C, turn on the microwave continuous flow reactor, control the microwave frequency to 2400 MHz ± 50 Hz, the reaction temperature to 12 ° C, and repeat the reaction for 28 hours. Stop the reaction, filter, and obtain a white solid, i.e., 4.92 kg of crude 1,3-dmcbda I, with a yield of 61.5%;

[0038] (2) Add 26 kg of acetic anhydride to the crude product I, heat to 115 ° C and stir for 5 h, then cool to room temperature and filter to obtain 4.42 kg of crude 1,3-dmcbda II with a yield of 55.25%;

[0039] (3) 20 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 3.5 h, then cooled to room temperature, filtered, and vacuum-dried at 55° C. to obtain 1,3-dmcbda fine product, i.e., 4.25 kg of product 1,3-dmcbda, with a yield of 53.13% and a 1,3-dmcbda:1,2-dmcbda ratio of 99.88:0.12; the yield in this example is calculated relative to citraconic anhydride.

[0040] Example 3

[0041] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0042] (1) Add 6 kg of citraconic anhydride to 30 kg of ethyl acetate, add 0.06 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -5 ° C, turn on the microwave continuous flow reactor, control the microwave frequency to 2550 MHz ± 50 Hz, the reaction temperature to 20 ° C, and repeat the reaction for 15 hours. Stop the reaction, filter, and obtain a white solid, i.e., 3.59 kg of crude 1,3-dmcbda I, with a yield of 59.83%;

[0043] (2) Add 15 kg of acetic anhydride to the crude product I, raise the temperature to 125 ° C and stir for 6 h, then cool to room temperature and filter to obtain 3.18 kg of crude 1,3-dmcbda II with a yield of 53.0%;

[0044] (3) 18 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 3 h, then cooled to room temperature, filtered, and vacuum-dried at 55°C to obtain 1,3-dmcbda fine product, i.e., 3.01 kg of product 1,3-dmcbda, with a yield of 50.17% and a 1,3-dmcbda:1,2-dmcbda ratio of 99.85:0.15; the yield in this example is calculated relative to citraconic anhydride.

[0045] Example 4

[0046] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0047] (1) Add 7.5 kg of citraconic anhydride to 45 kg of ethyl acetate, add 0.225 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -25 ° C, turn on the microwave continuous flow reactor, control the microwave frequency to 2350 MHz ± 50 Hz, the reaction temperature to 5 ° C, and repeat the reaction for 48 hours. Stop the reaction, filter, and obtain a white solid, i.e., 4.35 kg of crude 1,3-dmcbda I, with a yield of 58%;

[0048] (2) Add 18 kg of acetic anhydride to the crude product I, raise the temperature to 130 ° C and stir for 5.5 h, then cool to room temperature and filter to obtain 3.94 kg of crude 1,3-dmcbda II with a yield of 52.53%;

[0049] (3) 12 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 3 minutes, then cooled to room temperature, filtered, and vacuum-dried at 60°C to obtain 1,3-dmcbda fine product, i.e., 3.75 kg of product 1,3-dmcbda, with a yield of 50.0% and a 1,3-dmcbda:1,2-dmcbda ratio of 99.86:0.14; the yield in this example is calculated relative to citraconic anhydride.

[0050] Example 5

[0051] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0052] (1) Add 7 kg of citraconic anhydride to 35 kg of ethyl acetate, add 0.105 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -20 ° C, turn on the microwave continuous flow reactor, control the microwave frequency to 2500 MHz ± 50 Hz, the reaction temperature to 15 ° C, and repeat the reaction for 36 hours. Stop the reaction, filter, and obtain a white solid, i.e., 4.38 kg of crude 1,3-dmcbda I, with a yield of 62.57%;

[0053] (2) Add 21 kg of acetic anhydride to the crude product I, heat to 120 ° C and stir for 5 h, then cool to room temperature and filter to obtain 4 kg of crude 1,3-dmcbda II with a yield of 57.14%;

[0054] (3) 20 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 2.5 h, then cooled to room temperature, filtered, and vacuum-dried at 55° C. to obtain 1,3-dmcbda fine product, i.e., 3.84 kg of product 1,3-dmcbda, with a yield of 54.86% and a 1,3-dmcbda:1,2-dmcbda ratio of 99.88:0.12; the yield in this example is calculated relative to citraconic anhydride.

[0055] Example 6

[0056] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0057] (1) Add 6.5 kg of citraconic anhydride to 26 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10 ° C, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10 ° C, and repeat the reaction for 24 hours. Stop the reaction, filter, and obtain a white solid, i.e., 3.8 kg of crude 1,3-dmcbda I, with a yield of 58.46%;

[0058] (2) Add 26 kg of acetic anhydride to the crude product I, heat to 120 ° C and stir for 4 h, then cool to room temperature and filter to obtain 3.44 kg of crude 1,3-dmcbda II with a yield of 52.92%;

[0059] (3) 13.5 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum-dried at 60°C to obtain 1,3-dmcbda fine product, i.e., 3.26 kg of product 1,3-dmcbda, with a yield of 50.15% and a 1,3-dmcbda:1,2-dmcbda ratio of 99.88:0.15; the yield in this example is calculated relative to citraconic anhydride.

[0060] Example 7

[0061] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0062] (1) Add 7 kg of citraconic anhydride to 28 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10 ° C, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10 ° C, and repeat the reaction for 24 hours. Stop the reaction, filter, and obtain a white solid, i.e., 4.15 kg of crude 1,3-dmcbda I, with a yield of 59.29%;

[0063] (2) Add 28 kg of acetic anhydride to the crude product I, heat to 120 ° C and stir for 4 h, then cool to room temperature and filter to obtain 3.72 kg of crude 1,3-dmcbda II with a yield of 53.14%;

[0064] (3) 14.5 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum-dried at 60°C to obtain 1,3-dmcbda fine product, i.e., 3.52 kg of product 1,3-dmcbda, with a yield of 50.29% and a 1,3-dmcbda:1,2-dmcbda ratio of 99.88:0.15; the yield in this example is calculated relative to citraconic anhydride.

[0065] The yield of the product 1,3-dmcbda prepared in the above embodiment is high and greater than 50%. The purity of the product 1,3-dmcbda is high and the ratio of 1,3-dmcbda to 1,2-dmcbda is ≥99.85:0.15.

[0066] Comparative Example 1

[0067] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0068] (1) Add 7.5 kg of citraconic anhydride to 30 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the microwave continuous flow reactor, control the microwave frequency to 2450 MHz ± 50 Hz, the reaction temperature to 10 ° C, react for 24 h, stop the reaction, filter, and obtain a white solid, i.e., 4.12 kg of crude 1,3-dmcbda I, with a yield of 54.93%;

[0069] (2) Add 30 kg of acetic anhydride to the crude product I, heat to 120 ° C and stir for 4 h, then cool to room temperature and filter to obtain 3.55 kg of crude 1,3-dmcbda II with a yield of 47.33%;

[0070] (3) 14.2 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum-dried at 60°C to obtain 1,3-dmcbda fine product, i.e., 33.29 kg of product 1,3-dmcbda, with a yield of 43.87% and a 1,3-dmcbda:1,2-dmcbda ratio of 99.80:0.2; the yield in this comparative example was calculated relative to citraconic anhydride.

[0071] Comparative Example 2

[0072] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0073] (1) Add 7.5 kg of citraconic anhydride to 30 kg of ethyl acetate and stir evenly. Turn on the circulation pump and use an ice machine to cool the reaction solution to -10 ° C. Turn on the microwave continuous flow reactor and control the microwave frequency to 2450 MHz ± 50 Hz. The reaction temperature is 10 ° C. The reaction is repeated for 24 hours. The reaction is stopped and filtered to obtain a white solid, i.e., 3.31 kg of crude 1,3-dmcbda I, with a yield of 44.13%;

[0074] (2) Add 30 kg of acetic anhydride to the crude product I, heat to 120 ° C and stir for 4 h, then cool to room temperature and filter to obtain 2.82 kg of crude 1,3-dmcbda II with a yield of 37.6%;

[0075] (3) 11.2 kg of acetone was added to the crude 1,3-dmcbda product II, and the mixture was heated under reflux for 4 h, then cooled to room temperature, filtered, and vacuum-dried at 60°C to obtain 1,3-dmcbda fine product, i.e., 3.57 kg of product 1,3-dmcbda, with a yield of 34.27% and a 1,3-dmcbda:1,2-dmcbda ratio of 99.87:0.13; the yield in this comparative example was calculated relative to citraconic anhydride.

[0076] Comparative Example 3

[0077] A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, comprising the following steps:

[0078] (1) Add 7.5 kg of citraconic anhydride to 30 kg of ethyl acetate, add 0.1 kg of p-toluenesulfonic acid as a catalyst, stir evenly, turn on the circulation pump, use an ice machine to cool the reaction solution to -10 ° C, turn on the light wave reactor, control the wavelength to 365 nm, the reaction temperature to 10 ° C, and repeat the reaction for 24 hours. Stop the reaction and filter to obtain a white solid, i.e., 2 kg of crude 1,3-dmcbda, with a yield of 26.67%;

[0079] (2) Add 15 kg of acetic anhydride to the crude product I, heat to 120 ° C and stir for 4 h, then cool to room temperature and filter to obtain 1.7 kg of crude 1,3-dmcbda II with a yield of 22.67%;

[0080] (3) Add 6.8 kg of acetone to the crude 1,3-dmcbda II, heat under reflux for 4 h, then cool to room temperature, filter, and vacuum dry at 60 °C to obtain 1,3-dmcbda fine product, i.e., 1.5 kg of product 1,3-dmcbda, with a yield of 20%. The NMR spectrum of the reaction solution is shown as follows: Figure 3 As shown, the NMR spectrum of the product 1,3-dmcbda is as follows Figure 4 As shown, the ratio of 1,3-dmcbda to 1,2-dmcbda is 99.68:0.32; the yield in this comparative example is calculated relative to citraconic anhydride.

[0081] Compared with Comparative Example 1, in Example 1, the reaction solution is first cooled and then subjected to multiple cycles of microwave-controlled reaction. The yield of the prepared product 1,3-dmcbda is higher, the yield is increased by more than 16%, and the purity is also relatively improved.

[0082] Compared with Comparative Example 1, Example 1 has a higher yield of the product 1,3-dmcbda by adding a catalyst and maintaining the same reaction time, which is increased by more than 48%.

[0083] In Example 1 and Comparative Example 3, the use of microwave continuous flow reaction can promote the formation of the product 1,3-dmcbda and reduce the generation of by-products, and the yield is increased by more than 30%.

[0084] In summary, the product 1,3-dmcbda prepared by the present invention has better quality, reduces the cost of raw materials, and enhances market competitiveness.

[0085] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above and that the present invention can be embodied in other specific forms without departing from the spirit and essential characteristics of the invention. Therefore, the embodiments should be considered in all respects as illustrative and non-restrictive, and the scope of the invention is defined by the appended claims rather than the foregoing description, and it is intended that all variations that come within the meaning and range of equivalents of the claims be embraced therein.

[0086] In addition, it should be understood that although this specification is described in terms of implementation methods, not every implementation method contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment can also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

Claims

1. A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride, characterized in that: The following steps are involved: (1) Citraconic anhydride, ethyl acetate, and a catalyst were stirred uniformly, and a microwave continuous flow reaction was performed in a manner of cooling the reaction solution first and then controlling the microwave for multiple cycles. After the reaction was completed, the reaction was filtered to obtain a crude 1,3-dmcbda product I; (2) Add acetic anhydride to the above crude 1,3-dmcbda product I, heat and stir, then cool to room temperature, filter and obtain crude 1,3-dmcbda product II; (3) Add acetone to the crude 1,3-dmcbda product II, heat to reflux, then cool to room temperature, and then vacuum dry to obtain the refined 1,3-dmcbda product; Step (1), the specific conditions of the microwave continuous flow reaction are: the reaction solution is first cooled to -25 to -5°C, then the light wave frequency is controlled to 2350MHz±50Hz to 2550MHz±50Hz, the reaction temperature is 5 to 20°C, and the reaction is repeated for 15 to 48 hours; In step (1), the catalyst is one of p-toluenesulfonic acid, benzenesulfonic acid or dimethylbenzenesulfonic acid.

2. The method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, wherein: In step (1), the added amount of the catalyst is 1 to 2.5% of the mass of citraconic anhydride.

3. A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that: In step (2), the mass ratio of the added amount of acetic anhydride to the mass of citraconic anhydride is 0.5 to 5:

1.

4. The preparation method of a 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that, Step (2), heating and stirring conditions: temperature is 110-140° C., and time is 2-10 h.

5. A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that, In step (3), the mass ratio of the added amount of acetone to the crude 1,3-dmcbda product II is 3 to 10:

1.

6. The preparation method of a 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that, In step (3), the reflux time is 1 to 5 hours.

7. A method for preparing 1,3-disubstituted cyclobutane-1,2,3,4-cyclobutanetetracarboxylic dianhydride according to claim 1, characterized in that, In step (3), the vacuum drying temperature is 50-60°C.

Images