6,6'-disubstituted-3,3',4,4'-biphenyltetracarboxylic acid and its dianhydride and methods for their preparation

Abstract

The application discloses a kind of 6,6'-disubstituted-3,3',4,4'-biphenyl tetracarboxylic acid and its dianhydride and preparation method thereof, the structure of the 6,6'-disubstituted-3,3',4,4'-biphenyl tetracarboxylic acid and its dianhydride is as shown in formula (I) and formula (II) respectively, R is selected from hydrocarbyl, hydrocarbyloxy, substituted hydrocarbyl or substituted hydrocarbyloxy, two R in the same structural formula are same or different;The preparation method is prepared 4-halogenated-5-substituted phthalic acid using halogen halogenation in the presence of quaternary ammonium salt, then under visible light illumination condition, palladium catalysis coupling can be directly coupled to generate 6,6'-disubstituted-3,3',4,4'-biphenyl tetracarboxylic acid, and further dehydration can obtain corresponding dianhydride.The application avoids the method of using concentrated sulfuric acid as auxiliary reagent for bromination in the prior art, and the reaction condition is mild.

Description

Technical Field

[0001] This invention belongs to the field of organic aromatic anhydrides, and particularly relates to the synthesis of organic aromatic anhydrides. Specifically, it relates to a 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid and its dianhydride and their preparation method. Background Technology

[0002] With the increasing demand for 5G and transparent displays in recent years, the modification of polyimide materials to meet these development needs has become increasingly important. Polyimide (PI) is formed by the condensation polymerization of diamines and dianhydrides. Among them, polyimide materials based on 3,3′,4,4′-biphenyltetracarboxylic dianhydride (BPDA) exhibit excellent heat resistance, water resistance, mechanical properties, and dielectric properties, making it the ultra-heat-resistant resin with the highest heat resistance temperature to date. Therefore, modifying and altering the BPDA structure to develop BPDA with other substituent groups can further endow and improve the relevant properties of PI materials. For example, BPDA containing cyano side chains can improve the solubility of PI (CN102329290A, 2011); BPDA modified with trifluoromethyl groups can further reduce the dielectric properties and water absorption properties of PI (CN106699709A, 2016; KR2017076114A, 2017); BPDA modified with large side groups such as phenyl and its derivatives can reduce the birefringence of PI and the polarization loss during use (Macromolecu). Les, 2003, 36, 2327; J. Mater. Chem., 2011, 21, 1810; CN102086181A, 2011); while simple methyl-substituted BPDA, namely 6,6′-dialkyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride (DMPBDA), can reduce the expansion rate of PI and increase the transmittance of PI (EP1013650A, 2000; CN104513395A, 2015).

[0003] Referring to existing literature and patents regarding the preparation methods of 3,3′,4,4′-biphenyltetracarboxylic acid (JP55020705, 1980; JP06122650, 1994; CN1228366C, 2003; Insulating Materials, 2011, 44(5), 24; CN110563678A, 2019, etc.), phthalic anhydride is first chlorinated to produce chlorophthalic acid, followed by dehalogenation coupling in an aqueous phase using a palladium-based metal catalyst to obtain 3,3′,4,4′-biphenyltetracarboxylic acid. For methylphthalic anhydride, the steric hindrance of the methyl group makes the first halogenation reaction difficult to occur, and the subsequent dehalogenation coupling reaction is also difficult to occur due to the presence of the methyl group. Instead, the competing side reaction, dehalogenation reduction, mainly occurs, yielding only methylphthalic acid.

[0004] Therefore, to date, only one publicly disclosed method for synthesizing DMPBDA has been developed (EP1013650A, 2000). This method starts with 4-methylphthalic anhydride, first preparing 4-bromo-5-methylphthalic acid using potassium bromate under concentrated sulfuric acid conditions. Then, 4-bromo-5-methylphthalic acid is converted to dimethyl 4-bromo-5-methylphthalate using sulfoxide, methanol, and other reagents. Dimethyl 4-bromo-5-methylphthalate is then coupled in the presence of zinc powder, nickel dichloride, and a ligand to generate dimethyl 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylate. This methyl ester is then hydrolyzed and acidified to obtain 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid, which is subsequently dehydrated to obtain the anhydride DMPBDA. This method involves a 5-step conversion process, which is quite long and the overall yield is only about 25%, which severely restricts the widespread use of DMPBDA dianhydride in the preparation of PI materials. Summary of the Invention

[0005] To overcome the problems existing in the prior art, this invention provides 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid and its dianhydride, along with their preparation method. The 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid and its dianhydride have the advantages of high purity and high whiteness. The method first prepares 4-halo-5-substituted phthalic acid by halogenation in the presence of a quaternary ammonium salt, followed by palladium-catalyzed coupling under visible light irradiation. This directly couples 4-halo-5-substituted phthalic acid to 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid, which is then further dehydrated to obtain the corresponding dianhydride. This method avoids the use of concentrated sulfuric acid as an auxiliary reagent for bromination in EP1013650A, and by employing palladium-catalyzed coupling technology to directly couple 4-halo-5-substituted phthalic acid, it avoids the cumbersome reaction steps of esterification and hydrolysis, and the resulting product is easily separable. This method has a short route, high yield, and greatly improves the preparation conditions, showing good prospects for industrialization.

[0006] One objective of this invention is to provide a 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid, the structure of which is shown in formula (I), wherein R is selected from hydrocarbon group, hydroxyl group, substituted hydrocarbon group or substituted hydroxyl group, and the two Rs may be the same or different (preferably the two Rs are the same):

[0007]

[0008] The purity of the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is greater than 95%, and its whiteness is greater than 70.

[0009] Among them, the whiteness of the monomer has a significant impact on the transparency of the subsequent polymer.

[0010] In this invention, the content of impurities such as 4-halo-5-substituted phthalic acid and 4-alkyl phthalic acid in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is less than 5%.

[0011] In a preferred embodiment, the purity of the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is greater than 98%, preferably greater than 98.5%.

[0012] In a preferred embodiment, the total cation content in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is less than 150 ppm, preferably less than 100 ppm, and more preferably less than 50 ppm.

[0013] In a preferred embodiment, the total content of anions in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is less than 150 ppm, preferably less than 100 ppm, and more preferably less than 50 ppm.

[0014] In a preferred embodiment, in formula (I), R is selected from alkyl, alkoxy, substituted alkyl (preferably halogen-substituted alkyl) or substituted alkoxy (preferably halogen-substituted alkoxy), and the two Rs may be the same or different.

[0015] In a further preferred embodiment, in formula (I), R is selected from C1 to C10 alkyl, C1 to C10 alkoxy, C1 to C10 substituted alkyl or C1 to C10 substituted alkoxy, and the two Rs may be the same or different.

[0016] In a further preferred embodiment, in formula (I), R is selected from C1-C4 alkyl, C1-C4 alkoxy, C1-C4 substituted alkyl, or C1-C4 substituted alkoxy, and the two Rs may be the same or different. For example, R is selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, trifluoromethyl, or trifluoromethoxy.

[0017] In a preferred embodiment, the alkali metal ion content in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is less than or equal to 20 ppm, the alkaline earth metal ion content is less than or equal to 20 ppm, and the transition metal ion content is less than or equal to 5 ppm. Preferably, the alkali metal ions include sodium ions and / or potassium ions, the alkaline earth metal ions include calcium ions and / or magnesium ions, and the transition metal ions include at least one of copper ions, iron ions, manganese ions, nickel ions, cobalt ions, lead ions, and zinc ions.

[0018] In a preferred embodiment, the content of each anion in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is independently less than or equal to 30 ppm, wherein the anion includes at least one of chloride ion, sulfate ion, phosphate ion, and silicate ion.

[0019] A second objective of this invention is to provide a method for preparing 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid, preferably used for preparing the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid described in one objective of this invention, wherein the preparation method includes:

[0020] (1) Mix 4-substituted phthalic acid and / or its anhydride, quaternary ammonium salt, and strong alkaline aqueous solution, then add halogen element and react. After the reaction is completed, add reducing agent solution and after post-treatment, obtain intermediate product I, namely 4-halo-5-substituted phthalic acid.

[0021] In step (1), the quaternary ammonium salt can form a complex with the halogen element, which promotes the smooth and successful occurrence of the halogenation reaction. Specifically, the quaternary ammonium salt is used to increase the halogenation reaction rate. In step (1), the purpose of adding the reducing agent solution is to neutralize the unreacted halogen element.

[0022] (2) The intermediate product I was added to an inorganic alkaline aqueous solution, and then a catalyst and a reducing agent were added. After reaction and post-treatment, 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid was obtained.

[0023] Among them, the inventors discovered through numerous experiments that visible light irradiation can promote the coupling of 4-halo-5-methylphthalic acid.

[0024] In a preferred embodiment, the substituents in the 4-substituted phthalic acid and / or its anhydride are selected from hydrocarbon groups, hydroxyl groups, substituted hydrocarbon groups, or substituted hydroxyl groups.

[0025] In a further preferred embodiment, the substituents in the 4-substituted phthalic acid and / or its anhydride are selected from alkyl, alkoxy, substituted alkyl, or substituted alkoxy groups.

[0026] In a further preferred embodiment, the substituents in the 4-substituted phthalic acid and / or its anhydride are selected from C1-C10 alkyl groups, C1-C10 alkoxy groups, C1-C10 substituted alkyl groups, or C1-C10 substituted alkoxy groups, preferably from C1-C4 alkyl groups, C1-C4 alkoxy groups, C1-C4 substituted alkyl groups, or C1-C4 substituted alkoxy groups.

[0027] Wherein, the structure of the 4-substituted phthalic acid and / or its anhydride is as follows: Figure 1As shown in the first structural formula on the left, R is its substituent.

[0028] In a preferred embodiment, the quaternary ammonium salt has the structural formula (R1R2R3R4)NY, wherein R1, R2, R3, and R4 are each independently selected from one of C1 to C20 alkyl groups, and Y is selected from one of halide anions and acid radical anions.

[0029] In a further preferred embodiment, the quaternary ammonium salt has the structural formula (R1R2R3R4)NY, wherein R1, R2, R3, and R4 are each independently selected from one of the alkyl groups from C1 to C10, and Y is selected from one of the halide anions, and preferably has the same elemental type as the halogen element.

[0030] For example, (R1R2R3R4)N- can be selected from tetraethylammonium, tetrapropylammonium or tetrabutylammonium, and the anion Y is selected from chloride ion, bromide ion or iodide ion, and is consistent with the subsequently added halogen element.

[0031] In a preferred embodiment, in step (1), the strong alkali is selected from at least one of sodium hydroxide, potassium hydroxide, and cesium hydroxide.

[0032] In a preferred embodiment, in step (1), the halogen is selected from at least one of chlorine, bromine, and iodine.

[0033] In a preferred embodiment, in step (1), the weight ratio of the halogen element to 4-substituted phthalic acid and / or its anhydride is (0.4 to 1):1.

[0034] For example, the weight ratio of the halogen element to 4-substituted phthalic acid and / or its anhydride is 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1 or 1:1.

[0035] In a preferred embodiment, in step (1), the weight ratio of the strong base to 4-substituted phthalic acid and / or its anhydride in the strong base aqueous solution is 1:(1-4), preferably 1:(1.8-3.2).

[0036] When the weight ratio of the strong base to 4-substituted phthalic acid and / or its anhydride is greater than 1:1, a side reaction will occur, namely, the generated 4-halo-5-substituted phthalic acid will be further hydrolyzed to 4-hydroxy-5-substituted phthalic acid.

[0037] For example, in step (1), the weight ratio of the strong base to 4-substituted phthalic acid and / or its anhydride in the strong base aqueous solution is 1:1, 1:1.5, 1:2, 1:2.5, 1:3, 1:3.5 or 1:4.

[0038] In a preferred embodiment, in step (1), the weight ratio of the strong alkaline aqueous solution to 4-substituted phthalic acid and / or its anhydride is (5-20):1.

[0039] For example, in step (1), the weight ratio of the strong base aqueous solution to 4-substituted phthalic acid and / or its anhydride is 5:1, 6:1, 8:1, 10:1, 12:1, 14:1, 16:1, 18:1 or 20:1.

[0040] In a preferred embodiment, in step (1), the weight ratio of the quaternary ammonium salt to 4-substituted phthalic acid and / or its anhydride is (0.1 to 0.5):1.

[0041] Quaternary ammonium salts promote halogenation reactions. When the weight ratio of quaternary ammonium salt to 4-substituted phthalic acid and / or its anhydride is higher than 0.5:1, it increases the difficulty of subsequent separation and purification, resulting in a decrease in yield.

[0042] For example, in step (1), the weight ratio of the quaternary ammonium salt to 4-substituted phthalic acid and / or its anhydride is 0.1:1, 0.2:1, 0.3:1, 0.4:1 or 0.5:1.

[0043] In a preferred embodiment, in step (1), the reaction temperature is 0 to 100°C and the time is 3 to 36 hours.

[0044] In a further preferred embodiment, in step (1), the reaction temperature is 25–80°C and the time is 6–24 hours.

[0045] For example, in step (1), the temperature of the reaction is 25°C, 30°C, 40°C, 50°C, 60°C, 70°C or 80°C, and the time is 6 hours, 8 hours, 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours or 24 hours.

[0046] In a preferred embodiment, in step (1), after the reaction is completed and the temperature is lowered to room temperature, a reducing agent solution is added.

[0047] The reducing agent solvent is preferably an aqueous reducing agent solution.

[0048] In a further preferred embodiment, in step (1), the reducing agent solution is selected from at least one of sodium sulfite solution, sodium bisulfite solution, sodium thiosulfate solution, sodium dithionite solution, hydrazine hydrate, and hydroxylamine solution. Preferably, the weight concentration of the reducing agent solution is 10-25 wt%. More preferably, the weight ratio of the reducing agent solution to 4-substituted phthalic acid and / or its anhydride is (0.1-0.4):1.

[0049] In a preferred embodiment, in step (1), the post-processing includes: (a) adjusting the pH of the reaction system to between 0 and 4, preferably between 1 and 2; (b) extracting the organic phase using an organic solvent; and (c) drying and optionally concentrating the organic phase to obtain the intermediate product I.

[0050] In a further preferred embodiment, in step (a), a strong acidic substance is used to adjust the pH value of the reaction system. Preferably, the strong acidic substance is selected from one or more of hydrochloric acid, sulfuric acid, and phosphoric acid.

[0051] In a further preferred embodiment, in step (b), the organic solvent is selected from one or more of ethyl acetate, diethyl ether, methyl tert-butyl ether, and tetrahydrofuran.

[0052] In a further preferred embodiment, in step (c), the drying is performed using a desiccant, preferably selected from one or more of anhydrous sodium sulfate, anhydrous magnesium sulfate, 3A molecular sieve, 4A molecular sieve, and silica gel desiccant.

[0053] In a preferred embodiment, in step (2), the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium carbonate, potassium carbonate, and cesium carbonate.

[0054] In a further preferred embodiment, in step (2), the weight ratio of the inorganic base to intermediate product I is (0.25-0.75):1; and / or, the weight ratio of the inorganic base aqueous solution to intermediate product I is (5.0-10.0):1.

[0055] For example, in step (2), the weight ratio of the inorganic base to intermediate product I (i.e., 4-halo-5-substituted phthalic acid) is 0.25:1, 0.3:1, 0.35:1, 0.4:1, 0.45:1, 0.5:1, 0.55:1, 0.6:1, 0.65:1, 0.7:1, or 0.75:1; and / or, the weight ratio of the inorganic base aqueous solution to intermediate product I (i.e., 4-halo-5-substituted phthalic acid) is 5.0:1, 6.0:1, 7.0:1, 8.0:1, 9.0:1, or 10.0:1.

[0056] In a preferred embodiment, in step (2), the catalyst is selected from palladium on carbon catalyst and / or nickel palladium on carbon catalyst.

[0057] Among them, the carbon support in palladium on carbon and / or nickel palladium on carbon catalysts can absorb visible light, which improves the catalytic efficiency of the catalyst and promotes the smooth progress of the reaction.

[0058] In a further preferred embodiment, in step (2), the palladium content in the palladium-on-carbon catalyst is 1 to 20% of the total mass of the palladium-on-carbon catalyst; and / or, the palladium content in the nickel-palladium-on-carbon catalyst is 0.1 to 8% of the total mass of the nickel-palladium-on-carbon catalyst, and the mass ratio of palladium to nickel is 1:0.1 to 1:10.

[0059] For example, the palladium content in the palladium-on-carbon catalyst is 1%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, or 20% of the total mass of the palladium-on-carbon catalyst; and / or, the palladium content in the nickel-palladium-on-carbon catalyst is 0.1%, 0.5%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, or 8% of the total mass of the nickel-palladium-on-carbon catalyst, and the mass ratio of palladium to nickel is 1:0.1, 1:0.2, 1:0.5, 1:0.8, 1:1, 1:2, 1:4, 1:6, 1:8, or 1:10.

[0060] In a further preferred embodiment, in step (2), the amount of catalyst used is 0.1 to 20 wt% of intermediate product I.

[0061] For example, in step (2), the amount of catalyst used is 0.1 wt%, 0.5 wt%, 0.8 wt%, 1 wt%, 2 wt%, 5 wt%, 8 wt%, 10 wt%, 15 wt%, or 20 wt% of intermediate product I (i.e., 4-halo-5-substituted phthalic acid).

[0062] In a preferred embodiment, in step (2), the reducing agent is added under visible light irradiation, and the reaction is carried out under visible light irradiation.

[0063] In a further preferred embodiment, the visible light irradiation light source is one or more of incandescent lamps, xenon lamps, halogen lamps, tungsten lamps, LED lamps, and sunlight.

[0064] In a preferred embodiment, in step (2), the reducing agent is selected from one or more of hydroxylamine hydrochloride, hydroxylamine sulfate, hydrazine hydrate, hydrazine hydrochloride, hydrazine sulfate, glycerol, glucose, sodium formate, potassium formate, ammonium formate, and isopropanol.

[0065] In a further preferred embodiment, in step (2), the weight ratio of the reducing agent to intermediate product I (i.e., 4-halo-5-substituted phthalic acid) is 1:(1-6).

[0066] For example, in step (2), the weight ratio of the reducing agent to intermediate product I (i.e., 4-halo-5-substituted phthalic acid) is 1:1, 1:2, 1:3, 1:4, 1:5 or 1:6.

[0067] In a further preferred embodiment, the reducing agent is added dropwise in the form of an aqueous solution for 4 to 24 hours, preferably 6 to 8 hours, and the heat preservation time is 0 to 6 hours, preferably 2 to 3 hours.

[0068] In a preferred embodiment, in step (2), the temperature of the reaction is 40–120°C.

[0069] For example, in step (2), the reaction temperature is 40°C, 60°C, 80°C, 100°C or 120°C.

[0070] In a preferred embodiment, in step (2), the post-processing includes: first centrifugation, then adding a strong acidic substance to the supernatant to generate a crude precipitate of 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid, and finally washing with water to obtain pure 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid.

[0071] In a further preferred embodiment, in the post-processing of step (2), the strong acidic substance is selected from one or more of hydrochloric acid, sulfuric acid, and phosphoric acid.

[0072] In a further preferred embodiment, in the post-treatment of step (2), a strong acidic substance is added to adjust the pH of the reaction system to 1-4.

[0073] For example, in the post-treatment of step (2), a strong acid is added to adjust the pH of the reaction system to 1, 2, 3 or 4.

[0074] A third objective of this invention is to provide a 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride with the structure shown in formula (II), in which R is selected from hydrocarbon groups, hydroxyl groups, substituted hydrocarbon groups, or substituted hydroxyl groups, and the two Rs may be the same or different (preferably the two Rs are the same):

[0075]

[0076] The purity of the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride is greater than 95%, and its whiteness is greater than 70.

[0077] In this invention, the content of impurities such as 4-halo-5-substituted phthalic acid and 4-alkyl phthalic acid in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride is less than 5%.

[0078] In a preferred embodiment, the purity of the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride is greater than 98%, preferably greater than 98.5%.

[0079] In a preferred embodiment, the total cation content in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride is less than 150 ppm, preferably less than 100 ppm, and more preferably less than 50 ppm.

[0080] In a preferred embodiment, the total content of anions in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride is less than 150 ppm, preferably less than 100 ppm, and more preferably less than 50 ppm.

[0081] In a preferred embodiment, in formula (II), R is selected from alkyl, alkoxy, substituted alkyl (preferably halogen-substituted alkyl) or substituted alkoxy (preferably halogen-substituted alkoxy), and the two Rs may be the same or different.

[0082] In a further preferred embodiment, in formula (II), R is selected from C1 to C10 alkyl, C1 to C10 alkoxy, C1 to C10 substituted alkyl or C1 to C10 substituted alkoxy, and the two Rs may be the same or different.

[0083] In a further preferred embodiment, in formula (II), R is selected from C1-C4 alkyl, C1-C4 alkoxy, C1-C4 substituted alkyl, or C1-C4 substituted alkoxy, and the two Rs may be the same or different. For example, R is selected from methyl, ethyl, propyl, isopropyl, butyl, isobutyl, trifluoromethyl, or trifluoromethoxy.

[0084] In a preferred embodiment, the alkali metal ion content in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride is less than or equal to 20 ppm, the alkaline earth metal ion content is less than or equal to 20 ppm, and the transition metal ion content is less than or equal to 5 ppm. Preferably, the alkali metal ions include sodium ions and / or potassium ions, the alkaline earth metal ions include calcium ions and / or magnesium ions, and the transition metal ions include at least one of copper ions, iron ions, manganese ions, nickel ions, cobalt ions, lead ions, and zinc ions.

[0085] In a preferred embodiment, the content of each anion in the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride is independently less than or equal to 30 ppm, wherein the anion includes at least one of chloride ion, sulfate ion, phosphate ion, and silicate ion.

[0086] The 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride will be used in electronic-grade polyimide monomers. This polymer has strict requirements on ion content, so we need to control the ion content in the obtained 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride within a reasonable range.

[0087] The fourth objective of this invention is to provide a method for preparing 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride, preferably used for preparing the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride described in the third objective of this invention. The preparation method comprises: first obtaining 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid using the method described in the second objective of this invention; then dehydrating and washing the 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid to obtain 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic dianhydride.

[0088] In a preferred embodiment, the dehydration treatment is carried out using a dehydrating agent selected from one or more of acetyl chloride, propionyl chloride, acetic anhydride, propionic anhydride, oxaloyl chloride, thionyl chloride, and di-tert-butyl dicarbonate.

[0089] In a further preferred embodiment, the dehydration treatment is carried out using a dehydrating agent selected from one or more of acetic anhydride, propionic anhydride, and di-tert-butyl dicarbonate.

[0090] In a further preferred embodiment, the mass ratio of the dehydrating agent to 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is (4-15):1.

[0091] For example, the mass ratio of the dehydrating agent to 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid is 4:1, 6:1, 8:1, 10:1, 12:1, 14:1 or 15:1.

[0092] In a preferred embodiment, the dehydration process is carried out as follows: reflux for 2 to 8 hours in the presence of a dehydrating agent.

[0093] In a preferred embodiment, the washing is performed using an aprotic solvent, preferably selected from one or more of methyl tert-butyl ether, diethyl ether, 1,4-dioxane, acetone, methyl isopropyl ketone, ethylene glycol dimethyl ether, tetrahydrofuran, and methyl tetrahydrofuran.

[0094] The endpoints and any values ​​of the ranges disclosed in this invention are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0095] Compared with the prior art, the present invention has the following beneficial effects:

[0096] 1. This invention prepares 4-halo-5-alkylphthalic acid under alkaline conditions, avoiding the use of concentrated sulfuric acid as an auxiliary reagent for bromination in existing technologies (e.g., EP1013650A), and the reaction conditions are mild;

[0097] 2. The palladium-catalyzed coupling technology is used to directly couple halogenated alkylated phthalic acid, avoiding the cumbersome reaction steps of esterification and hydrolysis, thus simplifying the process route;

[0098] 3. The product obtained by this method is easy to separate, has a short route, and a high yield, which greatly improves the preparation conditions and has good prospects for industrialization. Attached Figure Description

[0099] Figure 1 A schematic diagram of the chemical reaction process of the method described in this invention is shown;

[0100] Figure 2 The 1H NMR spectrum of 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid prepared in Example 1 of the present invention is shown.

[0101] Figure 3 The mass spectrum of 6,6′-disubstituted-3,3′,4,4′-biphenyltetracarboxylic acid prepared in Example 1 of the present invention is shown. Detailed Implementation

[0102] The present invention will now be described in detail with reference to specific embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0103] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0104] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0105] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0106] The whiteness test is conducted as follows: the obtained product powder is compressed into tablets, and the whiteness value of the sample is directly measured using a whiteness meter.

[0107]

Example 1

[0108] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid:

[0109] (1) 2000g of distilled water containing 90g sodium hydroxide, 162g of 4-methylphthalic anhydride, and 16.2g of tetraethylammonium chloride were added sequentially to the reaction vessel. 82g of chlorine gas was introduced while stirring at room temperature. The mixture was then stirred at 80°C for 6 hours. After cooling to room temperature, 30g of 25wt% sodium bisulfite aqueous solution was added. The mixture was then neutralized with concentrated hydrochloric acid to pH=1. The aqueous phase was extracted three times with ethyl acetate. The organic phase was dried with anhydrous sodium sulfate and concentrated to obtain 204g of white powdery crude product 4-chloro-5-methylphthalic acid. The obtained crude product can be used directly in the next step.

[0110] (2) 1020g of an aqueous solution containing 132g sodium hydroxide, 204g of the above-mentioned 4-chloro-5-methylphthalic acid, and 2.04g of 20% palladium on carbon catalyst were added sequentially to the reaction vessel. The temperature was raised to 100℃, and 312g of an aqueous solution containing 78g of hydroxylamine sulfate was added dropwise under sunlight. The temperature was maintained for 8 hours, followed by another 2 hours of temperature maintenance. After centrifugation, 50% sulfuric acid was added to the supernatant to adjust the pH to 2, resulting in white crystals. After filtration, 160g of crude 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid was obtained. This crude product was washed several times with deionized water and then dried to obtain pure 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid with a purity of 98.8% and a whiteness of 76.8. Sodium ions were 16.6 ppm, while potassium, calcium, magnesium and other transition metal ions were not detected, and anions such as chloride and sulfate were not detected.

[0111] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride:

[0112] (3) 132 g of the 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid obtained above was refluxed in 1500 g of acetic anhydride for 3 hours and filtered to obtain 120 g of crude product. This crude product was pulped with methyl tert-butyl ether, then filtered, and the filter cake was washed twice with methyl tert-butyl ether and dried to obtain 113 g of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, with a yield of 95%, a purity of 99.0%, a whiteness of 73.6, a sodium ion content of 15.1 ppm, and no potassium, calcium, magnesium and other transition metal ions were detected. Chloride, sulfate and other anions were not detected.

[0113]

Example 2

[0114] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid:

[0115] (1) 2000g of distilled water containing 65g sodium hydroxide, 208g of 4-isopropylphthalic acid, and 50g of tetrabutylammonium bromide were added sequentially to the reaction vessel. 180g of liquid bromine was introduced under stirring at room temperature. The mixture was then heated to 80°C and stirred for 12 hours. After cooling to room temperature, 36g of 20wt% sodium sulfite aqueous solution was added. The mixture was then neutralized with concentrated sulfuric acid to pH=2. The aqueous phase was extracted three times with ethyl acetate. The organic phase was dried with anhydrous magnesium sulfate and concentrated to obtain 240g of white powdery crude product 4-bromo-5-isopropylphthalic acid. The obtained crude product can be used directly in the next step.

[0116] (2) Add 2000g of an aqueous solution containing 127g of potassium hydroxide, 240g of the above-mentioned 4-bromo-5-isopropylphthalic acid, and 2.5g of 10% palladium on carbon to the reaction vessel in sequence. Heat to 120℃ and add 210g of an aqueous solution containing 70g of hydroxylamine sulfate dropwise under xenon lamp irradiation. Maintain the temperature for 8 hours and then keep warm for another 2 hours. After centrifugation, add concentrated hydrochloric acid to the supernatant to adjust the pH to 3 to obtain white crystals. Filter to obtain 163g of crude 6,6′-diisopropyl-3,3′,4,4′-biphenyltetracarboxylic acid. Wash the crude product several times with deionized water and dry to obtain pure 6,6′-diisopropyl-3,3′,4,4′-biphenyltetracarboxylic acid with a purity of 98.5% and a whiteness of 75.8. The concentrations of potassium ions were 17.2 ppm, sodium ions were 20.1 ppm, calcium ions, magnesium ions and other transition metal ions were not detected, chloride ions were 30.0 ppm, sulfate ions were 23.0 ppm, and other anions were not detected.

[0117] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride:

[0118] (3) 135 g of the obtained 6,6′-diisopropyl-3,3′,4,4′-biphenyltetracarboxylic acid was refluxed in 1700 g of propionyl chloride for 2 hours and filtered to obtain 121 g of crude product. This crude product was pulped with diethyl ether, then filtered, and the filter cake was washed twice with diethyl ether and dried to obtain 115 g of 6,6′-diisopropyl-3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, with a yield of 93%, a purity of 98.8%, and a whiteness of 72.3. Among them, potassium ions were 15.1 ppm, sodium ions were 18.7 ppm, calcium ions, magnesium ions and other transition metal ions were not detected, chloride ions were 28.0 ppm, sulfate ions were 22.0 ppm, and other anions were not detected.

[0119]

Example 3

[0120] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid:

[0121] (1) Add 900g of distilled water containing 90g sodium hydroxide, 180g of 4-methylphthalic acid, and 45g of tetrabutylammonium chloride to the reaction vessel in sequence. 80g of chlorine gas is introduced while stirring at room temperature, and then stirred at 25°C for 12h. After cooling to room temperature, add 72g of 10wt% sodium thiosulfate aqueous solution. Then neutralize with phosphoric acid to pH=3. Extract the aqueous phase three times with methyl tert-butyl ether. Dry the organic phase with 3A molecular sieve and concentrate to obtain 192g of white powdery crude product 4-chloro-5-methylphthalic acid. The obtained crude product can be directly used for the next step.

[0122] (2) 1000g of an aqueous solution containing 144g sodium hydroxide, 192g of the above-mentioned 4-chloro-5-methylphthalic acid, and 2.68g of 5% palladium on carbon catalyst were added sequentially to the reaction vessel. The temperature was raised to 60℃, and 231g of an aqueous solution containing 77g of hydroxylamine hydrochloride was added dropwise under halogen lamp irradiation. The temperature was maintained for 4 hours, followed by 6 hours of incubation. After centrifugation, phosphoric acid was added to the supernatant to adjust the pH to 2, resulting in white crystals. After filtration, 142g of crude 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid was obtained. This crude product was washed several times with deionized water and then dried to obtain pure 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid with a purity of 98.5% and a whiteness of 81.2. Sodium ions were 22.8 ppm, while potassium, calcium, magnesium and other transition metal ions were not detected. Phosphate ions were 21.7 ppm, while other anions were not detected.

[0123] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride:

[0124] (3) 130 g of the obtained 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid was refluxed in 1500 g of acetic anhydride for 4 hours, and filtered to obtain 116 g of crude product. This crude product was pulped with chloroform, then filtered, and the filter cake was washed twice with chloroform and dried to obtain 111 g of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, with a yield of 95%. The purity was 99.5%, and the whiteness was 78.5. Sodium ions were 20.1 ppm, and potassium ions, calcium ions, magnesium ions, and other transition metal ions were not detected. Phosphate ions were 20.0 ppm, and other anions were not detected.

[0125]

Example 4

[0126] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid:

[0127] (1) In a reaction vessel, 3240g of distilled water containing 90g of sodium hydroxide, 162g of 4-methylphthalic anhydride, and 81g of tetrabutylammonium iodide were added sequentially. 130g of elemental iodine was added while stirring at room temperature. The mixture was then heated to 90°C and stirred for 9 hours. After cooling to room temperature, 36g of 15wt% sodium sulfite aqueous solution was added. The mixture was then neutralized with concentrated hydrochloric acid to pH=4. The aqueous phase was extracted three times with ethyl acetate. The organic phase was dried with silica gel and concentrated to obtain 235g of white powdery crude product 4-iodo-5-methylphthalic acid. The obtained crude product can be used directly in the next step.

[0128] (2) Add 1630g of an aqueous solution containing 123g of sodium hydroxide, 235g of the above-mentioned 4-iodo-5-methylphthalic acid, and 12g of nickel-palladium-carbon catalyst (1% palladium and 1% nickel) sequentially to the reaction vessel. Heat to 50℃, and add 175g of an aqueous solution containing 75g of glycerol dropwise under tungsten lamp irradiation. Maintain the temperature for 5 hours, and then keep warm for another 5 hours. After centrifugation, add concentrated hydrochloric acid to the supernatant to adjust the pH to 2, and obtain white crystals. Filter to obtain 120g of crude 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid. Wash the crude product several times with deionized water and dry to obtain pure 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid with a purity of 99.5% and a whiteness of 79.4. Sodium ions were 11.5 ppm, while potassium, calcium, magnesium and other transition metal ions were not detected. Chloride ions were 10.8 ppm, and other anions were not detected.

[0129] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride:

[0130] (3) 111 g of the obtained 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid was refluxed in 1620 g of propionic anhydride for 5 hours and filtered to obtain 100 g of crude product. This crude product was pulped with acetone, then filtered, and the filter cake was washed twice with acetone and dried to obtain 92 g of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, with a yield of 92%. The purity was 99.3%, and the whiteness was 78.2. Sodium ions were 10.1 ppm, and potassium ions, calcium ions, magnesium ions, and other transition metal ions were not detected. Chloride ions were 10.0 ppm, and other anions were not detected.

[0131]

Example 5

[0132] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid:

[0133] (1) In a reaction vessel, 2000g of distilled water containing 90g sodium hydroxide, 176g of 4-ethylphthalic anhydride, and 34g of tetrapropylammonium bromide were added sequentially. 168g of liquid bromine was added while stirring at room temperature. The mixture was then heated to 50°C and stirred for 3 hours. After cooling to room temperature, 40g of 10wt% sodium dithionite aqueous solution was added. The mixture was then neutralized with concentrated hydrochloric acid to pH=0. The aqueous phase was extracted three times with diethyl ether. The organic phase was dried with anhydrous sodium sulfate and concentrated to obtain 238g of white powdery crude product 4-bromo-5-ethylphthalic acid. The crude product obtained can be used directly in the next step.

[0134] (2) 1750g of an aqueous solution containing 110g of potassium hydroxide, 238g of the above-mentioned 4-bromo-5-ethylphthalic acid, and 47g of nickel-palladium-carbon catalyst (with a palladium content of 0.1% and a nickel content of 1%) were added sequentially to the reaction vessel. The temperature was raised to 40℃, and 180g of an aqueous solution containing 60g of sodium formate was added dropwise under incandescent light. The temperature was maintained for 7 hours, followed by another 3 hours of temperature maintenance. After centrifugation, concentrated hydrochloric acid was added to the supernatant to adjust the pH to 2, resulting in white crystals. After filtration, 141g of crude 6,6′-diethyl-3,3′,4,4′-biphenyltetracarboxylic acid was obtained. This crude product was washed several times with deionized water and then dried to obtain pure 6,6′-diethyl-3,3′,4,4′-biphenyltetracarboxylic acid with a purity of 99.0% and a whiteness of 74.1. The concentration of potassium ions was 12.5 ppm, while sodium, calcium, magnesium and other transition metal ions were not detected. The concentration of chloride ions was 12.9 ppm, and other anions were not detected.

[0135] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride:

[0136] (3) 135 g of the obtained 6,6′-diethyl-3,3′,4,4′-biphenyltetracarboxylic acid was refluxed in 900 g of oxaloyl chloride for 6 hours and filtered to obtain 118 g of crude product. This crude product was pulped with ethylene glycol dimethyl ether, then filtered, and the filter cake was washed twice with ethylene glycol dimethyl ether and dried to obtain 111 g of 6,6′-diethyl-3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, with a yield of 91%, a purity of 98.9%, and a whiteness of 72.3. The potassium ion content was 11.1 ppm, and sodium, calcium, magnesium, and other transition metal ions were not detected. The chloride ion content was 12.0 ppm, and other anions were not detected.

[0137]

Example 6

[0138] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid:

[0139] (1) 2000g of distilled water containing 90g sodium hydroxide, 246g of 4-trifluoromethylphthalic anhydride, and 25g of tetrabutylammonium bromide were added sequentially to the reaction vessel. 198g of liquid bromine was added while stirring at room temperature, and then stirred at 35°C for 12 hours. After cooling to room temperature, 30g of 20wt% sodium sulfite aqueous solution was added. The solution was then neutralized with concentrated sulfuric acid to pH=1. The aqueous phase was extracted three times with methyl tert-butyl ether. The organic phase was dried with 4A molecular sieve and concentrated to obtain 282g of white powdery crude product 4-bromo-5-trifluoromethyl phthalic acid. The obtained crude product can be used directly in the next step.

[0140] (2) 1800g of an aqueous solution containing 70.5g sodium hydroxide, 282g of the above-mentioned 4-bromo-5-trifluoromethyl phthalic acid, and 28g of 1% palladium on carbon catalyst were added sequentially to the reaction vessel. The temperature was raised to 70℃, and 400g of an aqueous solution containing 170g glucose was added dropwise under LED illumination. The temperature was maintained for 6 hours, followed by another 4 hours of temperature maintenance. After centrifugation, 50% sulfuric acid was added to the supernatant to adjust the pH to 2, resulting in white crystals. After filtration, 170g of crude 6,6′-ditrifluoromethyl-3,3′,4,4′-biphenyltetracarboxylic acid was obtained. This crude product was washed several times with deionized water and dried to obtain pure 6,6′-ditrifluoromethyl-3,3′,4,4′-biphenyltetracarboxylic acid with a purity of 99.0% and a whiteness of 73.2. The sodium ion content was 4.8 ppm, and calcium, magnesium, and other transition metal ions were not detected. Anions were not detected.

[0141] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride:

[0142] (3) 161 g of the obtained 6,6′-ditrifluoro-3,3′,4,4′-biphenyltetracarboxylic acid was refluxed in 840 g of oxaloyl chloride for 7 hours and filtered to obtain 152 g of crude product. This crude product was pulped with 1,4-dioxane, then filtered, and the filter cake was washed twice with 1,4-dioxane and dried to obtain 140 g of 6,6′-ditrifluoro-3,3′,4,4′-biphenyltetracarboxylic dianhydride, with a yield of 94%, a purity of 98.7%, and a whiteness of 70.9. The sodium ion content was 4.1 ppm, and calcium ions, magnesium ions, and other transition metal ions were not detected. Anions were not detected.

[0143]

Example 7

[0144] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid:

[0145] (1) In a reaction vessel, 2000g of distilled water containing 65g of potassium hydroxide, 204g of 4-butylphthalic anhydride, and 25g of tetraethylammonium chloride were added sequentially. 86g of chlorine gas was introduced while stirring at room temperature, and then the mixture was heated to 30°C and stirred for 24 hours. After cooling to room temperature, 20.4g of 20wt% hydrazine hydrate solution was added, and then the mixture was neutralized with phosphoric acid to pH=2. The aqueous phase was extracted three times with diethyl ether, and the organic phase was dried with anhydrous sodium sulfate. The mixture was concentrated to obtain 206g of white powdery crude product 4-chloro-5-butylphthalic acid. The crude product obtained can be used directly in the next step.

[0146] (2) Add 1030g of an aqueous solution containing 133g of potassium hydroxide, 206g of the above-mentioned 4-chloro-5-butylphthalic acid, and 30g of nickel-palladium-carbon catalyst (with palladium content of 0.5% and nickel content of 3%) sequentially to the reaction vessel. Raise the temperature to 85℃, and add 164g of an aqueous solution containing 41g of isopropanol dropwise under xenon lamp irradiation. Maintain the temperature for 8 hours, and then keep warm for another 0.5 hours. Then centrifuge and add concentrated hydrochloric acid to the supernatant to adjust the pH to 1 to obtain white crystals. Filter to obtain 168g of crude 6,6′-dibutyl-3,3′,4,4′-biphenyltetracarboxylic acid. Wash the crude product several times with deionized water and dry to obtain pure 6,6′-dibutyl-3,3′,4,4′-biphenyltetracarboxylic acid with a purity of 99.1% and a whiteness of 77.6. Potassium ions were 5.1 ppm, while sodium, calcium, magnesium, and other transition metal ions were not detected, and anions were not detected.

[0147] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride:

[0148] (3) 159 g of the obtained 6,6′-dibutyl-3,3′,4,4′-biphenyltetracarboxylic acid was refluxed in 1140 g of acetyl chloride for 8 hours and filtered to obtain 142 g of crude product. This crude product was pulped with methyltetrahydrofuran, then filtered, and the filter cake was washed twice with methyltetrahydrofuran and dried to obtain 136 g of 6,6′-dibutyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride, with a yield of 95%. The purity was 98.9%, and the whiteness was 74.2. The potassium ion content was 4.1 ppm, and sodium, calcium, magnesium, and other transition metal ions were not detected. Anions were not detected.

[0149]

Example 8

[0150] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid:

[0151] (1) In a reaction vessel, 2000g of distilled water containing 90g sodium hydroxide, 162g of 4-methylphthalic anhydride, and 55g of tetrapropylammonium iodide were added sequentially. 162g of elemental iodine was added while stirring at room temperature. The mixture was then heated to 60°C and stirred for 36 hours. After cooling to room temperature, 30g of 25wt% sodium bisulfite aqueous solution was added. The mixture was then neutralized with concentrated hydrochloric acid to pH=1. The aqueous phase was extracted three times with ethyl acetate. The organic phase was dried with anhydrous magnesium sulfate and concentrated to obtain 201g of white powdery crude product 4-iodo-5-methylphthalic acid. The obtained crude product can be used directly in the next step.

[0152] (2) Add 2010g of an aqueous solution containing 100g of sodium hydroxide, 201g of the above-mentioned 4-iodo-5-methylphthalic acid, and 18g of nickel-palladium-carbon catalyst (with a palladium content of 8% and a nickel content of 0.8%) sequentially to the reaction vessel. Raise the temperature to 95℃, and add 132g of an aqueous solution containing 33g of hydrazine hydrate dropwise under LED light irradiation. Maintain the temperature for 4 hours, and then keep warm for another hour. After centrifugation, add concentrated hydrochloric acid to the supernatant to adjust the pH to 2, and white crystals are obtained. Filter to obtain 133g of crude 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid. Wash this crude product several times with deionized water and then dry to obtain pure 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid with a purity of 98.9% and a whiteness of 76.3. Sodium ions were 12.3 ppm, while calcium ions, magnesium ions, and other transition metal ions were not detected, and anions were not detected.

[0153] Preparation of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic dianhydride:

[0154] (3) 125 g of the obtained 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid was refluxed in 900 g of oxaloyl chloride for 2 hours and filtered to obtain 110 g of crude product. This crude product was pulped with tetrahydrofuran, then filtered, and the filter cake was washed twice with tetrahydrofuran and dried to obtain 105 g of 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, with a yield of 93%. The purity was 98.9%, and the whiteness was 73.1. The sodium ion content was 9.1 ppm, and calcium ions, magnesium ions, and other transition metal ions were not detected, and anions were not detected.

[0155] Comparative Example 1

[0156] Referring to the method described in existing literature (patent CN1526710A, 2003), 49g of monosodium 4-methylphthalic acid and 170g of water were added to a three-necked reaction flask, heated to 90℃ until dissolved, and then cooled to 70℃. Chlorine gas was introduced into the bottom of the reaction solution at a rate of 0.127g / min, and the reaction temperature was controlled at 70℃. The reaction was carried out for 1 hour. During the reaction, NaHCO3 solution was added to neutralize the byproduct hydrogen chloride, so that the pH value of the reaction system remained basically unchanged. Then, the chlorine gas rate was changed to 0.082g / min, and the reaction was carried out at 50℃ for 3 hours. After acidification with 30g of concentrated hydrochloric acid for 2 hours, the mixture was cooled to room temperature, extracted with diethyl ether, and evaporated to dryness to obtain 45g of crude product. The purity of 4-chloro-5-methylphthalic acid was determined by HPLC to be 36%. A large amount of unreacted 4-methylphthalic acid was found in the crude product.

[0157] Comparative Example 2

[0158] Following the method described in existing literature, 60g of water and 76g of liquid alkali (32% concentration) were added to a four-necked flask equipped with a thermometer, stirrer, dropping device, and reflux device. While stirring, 37g of purified sodium 4-chloro-5-methylphthalate monosodium salt and 0.4g of nickel-palladium-carbon catalyst (dry basis) were added. The mixture was heated to reflux, and a mixture of 16g ​​of hydroxylamine hydrochloride and 60g of water was added dropwise. The dropping rate was controlled, the liquid level was kept stable, and the reflux state was maintained for approximately 6 hours. After the addition was complete, the mixture was kept at this temperature for 1.5 hours. The temperature was then lowered to 85°C, and the mixture was filtered while hot to obtain the filtrate for later use.

[0159] 100g of water and 35g of 98% sulfuric acid were added to a four-necked flask equipped with a thermometer, stirrer, dropping device, and reflux device. The mixture was heated to reflux, and the above filtrate was added dropwise while maintaining reflux for 4 hours. The mixture was then kept at reflux for another 2 hours. The temperature was lowered to 85°C, and the mixture was filtered while hot to obtain 13g of solid product. Analysis showed that the main component of the crude product was 4-methylphthalic acid, and no 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid was detected.

[0160]

Experimental Example

[0161] 1. Nuclear magnetic resonance characterization

[0162] The 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid prepared in Example 1 was characterized by 1H NMR spectroscopy, and the results are as follows: Figure 2 As shown, in the 1H NMR spectrum, the singlet at approximately δ = 7.85 ppm belongs to carbon 6 between the carbonyl group and the biphenyl bond on the benzene ring. It shifts to a lower field due to the influence of the carbonyl group. The singlet at δ = 7.65 ppm belongs to carbon 3 between the carbonyl group and the methyl group. Its chemical shift is smaller than that of the hydrogen on carbon 6 due to the combined effects of electron donation from the methyl group and electron withdrawal from the carbonyl group. δ = 2.50 ppm is the solvent peak of deuterated dimethyl sulfoxide. The singlet at approximately δ = 2.41 ppm belongs to the hydrogen on the methyl group, indicating that the prepared sample is 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid. Furthermore, the obtained NMR spectrum is pure, with no other obvious signal peaks observed, indicating that the content of other impurities in the sample is less than 5%.

[0163] The 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid prepared in Examples 2-8 were also characterized by proton nuclear magnetic resonance spectroscopy, and it was verified that the obtained product was indeed 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid.

[0164] 2. Mass spectrometry characterization

[0165] The 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid prepared in Example 1 was characterized by mass spectrometry, and the results are as follows: Figure 3 As shown, [MH] － (C8H 13 The theoretical m / z value for O8 is 357.0610, and the measured value is 357.060; [M-2H] 2- The theoretical m / z value for / 2(C9H6O4) is 178.0266, and the measured value is 178.0260; [M-2H+Na] － (C 18 H 12 The theoretical value of NaO8 is 379.0430, and the measured value is 379.0422. This indicates that the prepared product is 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid.

[0166] The 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid prepared in Examples 2-8 was also subjected to mass spectrometry detection, and it was verified that the obtained product was indeed 6,6′-dimethyl-3,3′,4,4′-biphenyltetracarboxylic acid.

[0167] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A method for preparing 6, 6'-disubstituted-3, 3', 4, 4'-biphenyltetracarboxylic acid, comprising: (1) mixing 4-substituted phthalic acid and / or anhydride thereof, quaternary ammonium salt, strong alkali aqueous solution, and then adding halogen element, to react, and then adding reducing agent solution after the reaction is completed, and then treating to obtain intermediate product I; the quaternary ammonium salt has a structural formula of (R1R2R3R4) NY, wherein R1, R2, R3, and R4 are each independently selected from one of C1-C10 alkyl, Y is selected from one of halide, and is consistent with the element type of the halogen element; the substituent group in the 4-substituted phthalic acid and / or anhydride thereof is selected from C1-C10 alkyl or C1-C10 alkoxy; (2) adding the intermediate product I into inorganic alkali aqueous solution, and then adding catalyst and reducing agent, to react and treat to obtain 6, 6'-disubstituted-3, 3', 4, 4'-biphenyltetracarboxylic acid; in step (2), the catalyst is selected from palladium-carbon catalyst and / or nickel-palladium-carbon catalyst; in step (2), the reducing agent is added under visible light irradiation, and the reaction is carried out under visible light; the reducing agent is selected from one or more of hydroxylamine hydrochloride, hydroxylamine sulfate, hydrazine hydrate, hydrazine hydrochloride, hydrazine sulfate, glycerol, glucose, sodium formate, potassium formate, ammonium formate, and isopropyl alcohol. In step (1), the strong alkali is selected from at least one of sodium hydroxide, potassium hydroxide, and cesium hydroxide; and / or, the halogen element is selected from at least one of chlorine, bromine, and iodine element. In step (1), the weight ratio of the quaternary ammonium salt to the 4-substituted phthalic acid and / or anhydride thereof is (0.1-0.5) : 1; and / or, the weight ratio of the halogen element to the 4-substituted phthalic acid and / or anhydride thereof is (0.4-1) : 1; and / or, the weight ratio of the strong alkali in the strong alkali aqueous solution to the 4-substituted phthalic acid and / or anhydride thereof is 1: (1-4) ; and / or, the weight ratio of the strong alkali aqueous solution to the 4-substituted phthalic acid and / or anhydride thereof is (5-20) :

1.

2. The production method according to claim 1, characterized by, In step (1), the weight ratio of the strong alkali in the strong alkali aqueous solution to the 4-substituted phthalic acid and / or anhydride thereof is 1: (1.8-3.2). 5.The method according to claim 1, wherein, in step (1), the temperature of the reaction is 0-100 ℃, and the time is 3-36 hours; and / or, after the reaction is completed, the solution is cooled to room temperature, and the reducing agent solution is added; and / or, the post-treatment comprises: (a) adjusting the pH value of the reaction system to 0-4, (b) extracting the organic phase by using an organic solvent, and (c) drying the organic phase, and optionally concentrating to obtain the intermediate product I. 6.The method according to claim 5, wherein, the reducing agent solution is selected from at least one of sodium sulfite solution, sodium bisulfite solution, sodium thiosulfate solution, sodium hydrosulfite solution, hydrazine hydrate, and hydroxylamine solution; and / or, 3. The preparation method according to claim 1, characterized in that, ​ ​ ​ ​ ​ 4. The method of claim 1, wherein, ​ ​ ​ ​ ​ ​ ​ ​ ​ (a) adjusting the pH of the reaction system to 1-2.

7. The preparation method according to claim 5, characterized in that, The weight concentration of the reducing agent solution is 10-25 wt%.

8. The preparation method according to claim 5, characterized in that, The weight ratio of the reducing agent solution to 4-substituted phthalic acid and / or anhydride thereof is (0.1-0.4):

1.

9. The preparation method according to any one of claims 1-8, wherein, In step (2), the inorganic base is selected from one or more of sodium hydroxide, potassium hydroxide, cesium hydroxide, sodium carbonate, potassium carbonate, and cesium carbonate.

10. The preparation method according to claim 9, wherein, The weight ratio of the inorganic base to intermediate product I is (0.25-0.75):1; and / or, the weight ratio of the inorganic base aqueous solution to intermediate product I is (5.0-10.0):1; and / or, The content of palladium in the palladium-carbon catalyst is 1-20% of the total mass of the palladium-carbon catalyst; and / or, the content of palladium in the nickel-palladium-carbon catalyst is 0.1-8% of the total mass of the nickel-palladium-carbon catalyst, and the mass ratio of palladium to nickel is 1:0.1-1:10; and the amount of the catalyst used is 0.1-20 wt% of intermediate product I.

11. The preparation method according to claim 9, wherein, In step (2), the temperature of the reaction is 40-120°C; and / or, In step (2), the post-treatment comprises: first centrifugal separation, then adding a strong acid substance to the supernatant to precipitate the crude 6,6'-disubstituted-3,3',4,4'-biphenyltetracarboxylic acid product, and finally washing with water to obtain the pure 6,6'-disubstituted-3,3',4,4'-biphenyltetracarboxylic acid product.

12. The preparation method according to claim 11, wherein, In step (2), the weight ratio of the reducing agent to intermediate product I is 1:(1-6); and / or, In the post-treatment of step (2), a strong acid substance is added to adjust the pH of the reaction system to 1-4.

13. The preparation method according to claim 11, characterized in that, In step (2), the reducing agent is added dropwise in the form of an aqueous solution, the dropwise addition time is 4-24 hours, and the incubation time is 0-6 hours.

14. A method of making a 6,6'-disubstituted-3,3',4,4'-biphenyltetracarboxylic dianhydride, the method comprising: First, 6,6'-disubstituted-3,3',4,4'-biphenyltetracarboxylic acid is obtained by the preparation method according to any one of claims 1-13, then 6,6'-disubstituted-3,3',4,4'-biphenyltetracarboxylic acid is subjected to dehydration treatment and washing to obtain 6,6'-disubstituted-3,3',4,4'-biphenyltetracarboxylic dianhydride.

15. The preparation method according to claim 14, wherein, The dehydration treatment is performed using a dehydration agent selected from one or more of acetyl chloride, propionyl chloride, acetic anhydride, propionic anhydride, oxalyl chloride, dichlorosulfoxide, and di-tert-butyl dicarbonate; and / or, The mass ratio of the dehydration agent to 6,6'-disubstituted-3,3',4,4'-biphenyltetracarboxylic acid is (4-15):1; and / or, The dehydration treatment is performed by refluxing for 2-8 hours in the presence of the dehydration agent; and / or, The washing is performed using an aprotic solvent.

16. The method of claim 15, wherein, The aprotic solvent is selected from one or more of methyl tert-butyl ether, diethyl ether, 1,4-dioxane, acetone, methyl isopropyl ketone, ethylene glycol dimethyl ether, tetrahydrofuran, methyltetrahydrofuran. The aprotic solvent is selected from one or more of methyl tert-butyl ether, diethyl ether, 1,4-dioxane, acetone, methyl isopropyl ketone, ethylene glycol dimethyl ether, tetrahydrofuran, methyltetrahydrofuran. The aprotic solvent is selected from one or more of methyl tert-butyl ether, diethyl ether, 1,4-dioxane, acetone, methyl

Images