A method for synthesizing 2,6-naphthalene dicarboxylic acid

Abstract

The application discloses a synthesis method of 2,6-naphthalene dicarboxylic acid, which comprises the following steps: S1. Compound a is dissolved in an organic solvent, triethylamine, alcohol and a catalyst are added, and an oxidizing gas is introduced, so as to obtain compound b through reaction; and S2. Compound b is mixed with alcohol and water, an alkali is added, and an acid is added after reaction, so as to obtain a compound of formula I. The application uses a high-activity catalyst, is simple in operation, and has relatively mild reaction conditions. The addition of polyethylene glycol can further greatly improve the product yield, and the application has a wide application prospect.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of organic chemical synthesis, and particularly relates to a synthesis method of 2,6-naphthalene dicarboxylic acid. BACKGROUND

[0002] 2,6-naphthalene dicarboxylic acid is an important aromatic dicarboxylic acid monomer with a double ring structure, and can be used to manufacture polyester fiber materials with high strength and excellent dyeing performance. For example, the polycondensation product of 2,6-naphthalene dicarboxylic acid and ethylene glycol, polyethylene glycol 2,6-naphthalene dicarboxylate, can be used for special polyester bottle sheets, and has good gas barrier properties, and is suitable for use as a beer bottle, a carbonated beverage bottle and the like. In addition, the organic substance is also an important raw material for medicines and fine chemicals.

[0003] 2,6-naphthalene dicarboxylic acid can be prepared by using the MC (Mid-Century) liquid-phase air oxidation method, using a cobalt-manganese-bromine homogeneous catalyst and acetic acid as a solvent. In the last century, the American Amoco Company first realized the industrialization of 2,6-naphthalene dicarboxylic acid, and built a ten-thousand-ton industrial device, but the technology has not been further popularized, mainly because the raw materials used are o-xylene and butadiene, and the cost is too high.

[0004] Another method for preparing 2,6-naphthalene dicarboxylic acid is to use medium washing oil in coal tar as a raw material, and to obtain 2,6-naphthalene dicarboxylic acid with high purity by means of distillation. The main process is to first generate 2,6-dimethylnaphthalene by using the medium washing oil fraction in coal tar as a raw material by means of distillation, and then to generate crude 2,6-naphthalene dicarboxylic acid by using the same as a raw material for liquid-phase air oxidation under the action of a catalyst at high temperature and high pressure, and to further perform hydrogenation refining. The method can obtain 2,6-naphthalene dicarboxylic acid with high purity, but requires high temperature and high pressure conditions, and the reaction environment is relatively harsh. SUMMARY

[0005] The application provides a synthesis method of 2,6-naphthalene dicarboxylic acid based on the problems in the prior synthesis method, and the method uses a high-activity catalyst, is simple to operate, has relatively mild reaction conditions, and has a wide application prospect.

[0006] The chemical structural formulae of the compound of formula I, the compound a and the compound b are as follows, respectively.

[0007]

[0008] The synthesis method of 2,6-naphthalene dicarboxylic acid comprises the following steps:

[0009] S1. The compound a is dissolved in an organic solvent, triethylamine, alcohol, a catalyst and a cocatalyst are added, and an oxidizing gas is introduced, so as to obtain the compound b by reaction;

[0010] S2. Compound b is mixed with an alcohol, water, a base is added, after reaction an acid is added to obtain a compound of formula I.

[0011] In some embodiments, the solvent in the S1 step is selected from one or more of N,N-dimethylacetamide (DMA), N,N-dimethylformamide (DMF), N-methylpyrrolidone (NMP), dimethylsulfoxide (DMSO).

[0012] In some embodiments, the alcohol in the S1 step is ethanol.

[0013] In some embodiments, the catalyst in the S1 step is selected from one or both of Pd-TPPTS-IL / MC, Pd-TPPTS-IL / AC.

[0014] Pd-TPPTS-IL / MC, Pd-TPPTS-IL / AC is prepared by dissolving Pd(OAc)2 and TPPTS (triphenylphosphine tris-p-sulfonate sodium salt) in ionic liquid [bmim][p-CH3C6H4SO3] under stirring, loaded on MC (microspheres of carrier material) or AC (activated carbon).

[0015] In some embodiments, the co-catalyst in the S1 step is polyethylene glycol.

[0016] In some embodiments, the oxidizing gas in the S1 step is carbon monoxide.

[0017] Preferably, the solvent in the S1 step is N,N-dimethylacetamide, the alcohol is ethanol, the catalyst is selected from one of Pd-TPPTS-IL / MC, Pd-TPPTS-IL / AC, and the oxidizing gas is carbon monoxide.

[0018] In some embodiments, the alcohol in the S2 step is selected from one or both of methanol, ethanol.

[0019] In some embodiments, the base in the S2 step is selected from one or more of sodium hydroxide, lithium hydroxide, potassium hydroxide.

[0020] In some embodiments, the acid in the S2 step is selected from one or more of hydrochloric acid, sulfuric acid, hydrobromic acid.

[0021] Preferably, the alcohol in the S2 step is methanol, the base is sodium hydroxide, and the acid is hydrochloric acid.

[0022] In some embodiments, the number average molecular weight of the polyethylene glycol added in the S1 step is between 200 and 1000.

[0023] The addition of polyethylene glycol can improve the reaction yield under the same conditions.

[0024] In some specific embodiments, in the S1 step, the molar ratio of compound a, triethylamine, ethanol is 1-2:2-5:5-10, the mass ratio of compound a, Pd-TPPTS-IL / MC or Pd-TPPTS-IL / AC and polyethylene glycol is 1-2:3.5-5:0.2-1, and the mass(g):volume(ml) ratio of compound a and N,N-dimethylacetamide is 1-5:10-50.

[0025] In some specific embodiments, in the S1 step, the molar ratio of compound a, triethylamine, ethanol is 1:2:5, the mass ratio of compound a, Pd-TPPTS-IL / MC or Pd-TPPTS-IL / AC and polyethylene glycol is 1:3.5:0.2, and the mass(g):volume(ml) ratio of compound a and N,N-dimethylacetamide is 1:10.

[0026] In some specific embodiments, in the S2 step, the molar ratio of compound b, sodium hydroxide is 1-2:4-10, and the mass(g):volume(ml) ratio of compound b, methanol, water is 1-2:10-20:2-5.

[0027] In some specific embodiments, in the S2 step, the molar ratio of compound b, sodium hydroxide is 1:4, and the mass(g):volume(ml) ratio of compound b, methanol, water is 1:10:2.

[0028] Compared with the prior art, the present application uses a highly active catalyst, is simple to operate, and has relatively mild reaction conditions. The addition of polyethylene glycol can further greatly improve the product yield, and has a wide application prospect.

[0029] The concept and technical effects of the present application will be further described below to fully understand the purpose, features and effects of the present application. DETAILED DESCRIPTION

[0030] In order to make the technical means, creative features, purposes and effects of the application easy to understand, the application will be further described below. However, the application is not limited to the following embodiments.

[0031] It should be noted that the embodiments and the like in the specification are only used to illustrate the content disclosed in the specification for those skilled in the art to understand and read, and are not used to limit the limited conditions that the application can be implemented. Therefore, the adjustment does not pay creative labor, and falls within the scope of the technical content disclosed by the application without affecting the effects and purposes that the application can produce.

[0032] The various reagents involved in the examples, comparative examples, are commercially available products, unless otherwise specified. Polyethylene glycol was purchased from Sigma-Aldrich, average relative molecular mass 400.

[0033] Method for preparing Pd-TPPTS-IL / MC catalyst in the present invention:

[0034] This was carried out under strictly excluded oxygen conditions. In a typical preparation experiment, Pd(OAc)2(16.0 mg, 0.07 mmol) and TPPTS (trisodium triphenylphosphine 3-m-sulfonate) (240.5 mg, 0.42 mmol) were dissolved in ionic liquid [bmim][p-CH3C6H4SO3] (5.9 ml) under stirring. The catalyst solution was kept at 40 °C for about 30 min. A total of 5.0 g of catalyst support material microspheres were degassed under vacuum and stored under argon. Then, they were impregnated with absolute ethanol for 1 h, removed and oven dried before pouring into the catalyst solution. After 30 min at 40 °C, the catalyst support material microspheres were allowed to fully absorb the catalyst solution before drying under supercritical carbon dioxide conditions for storage.

[0035] Method for preparing Pd-TPPTS-IL / AC catalyst in the present invention:

[0036] This was carried out under strictly excluded oxygen conditions. In a typical preparation experiment, Pd(OAc)2(16.0 mg, 0.07 mmol) and TPPTS (trisodium triphenylphosphine 3-m-sulfonate) (240.5 mg, 0.42 mmol) were dissolved in ionic liquid [bmim][p-CH3C6H4SO3] (5.9 ml) under stirring. The catalyst solution was kept at 40 °C for about 30 min. 2 g of activated carbon were degassed under vacuum and stored under argon. Then, they were impregnated with absolute ethanol for 1 h, removed and oven dried before pouring into the catalyst solution. After 30 min at 40 °C, the activated carbon was allowed to fully absorb the catalyst solution before drying under supercritical carbon dioxide conditions for storage.

[0037] Example 1

[0038] 10g of compound a (2,6-dibromonaphthalene) was dissolved in DMA (100mL), followed by triethylamine (7.06g) and ethanol (8g). Then, 35g of a catalyst (containing 0.5mmol of palladium acetate, supported by a palladium catalyst (Pd-TPPTS-IL / MC, [bmim][p-CH3C6H4SO3], with a loading of 10%, and an inorganic support, MC) and 2g of polyethylene glycol (number-average molecular weight, 400) were added. The reaction system was placed in a stainless steel autoclave, and carbon monoxide was introduced at a pressure of 4 MPa at 120°C with stirring for 12 hours. After completion of the reaction, as determined by TLC, the mixture was diluted with 200mL of ethyl acetate and 200mL of water. The organic phase was then washed with saturated brine, concentrated to dryness, and purified by column chromatography to yield 5.7g of compound b (diethyl 2,6-naphthalenedicarboxylate) in a 60% yield.

[0039] Example 2

[0040] 20g of compound a (2,6-dibromonaphthalene) was dissolved in DMA (200mL), followed by the addition of triethylamine (14.1g) and ethanol (16g). Then, 70g of a catalyst (containing 1mmol of palladium acetate, supported by a palladium catalyst (Pd-TPPTS-IL / MC, [bmim][p-CH3C6H4SO3], with a loading of 10%) and an inorganic support, MC, and 4g of polyethylene glycol (number-average molecular weight, 400) were added. The reaction system was placed in a stainless steel autoclave, and carbon monoxide was introduced at a pressure of 4MPa at 120°C with stirring for 12 hours. After completion of the reaction, as determined by TLC, the mixture was diluted with 400mL of ethyl acetate and 400mL of water. The organic phase was then washed with saturated brine, concentrated to dryness, and purified by column chromatography to yield 11.6g of compound b (diethyl 2,6-naphthalenedicarboxylate) in a 61% yield.

[0041] Example 3

[0042] Dissolve 10g of compound a (2,6-dibromonaphthalene) in DMA (100mL), add triethylamine (7.06g) and ethanol (8g), then add 35g of a catalyst (containing 0.5mmol of palladium acetate, supported by a palladium catalyst (Pd-TPPTS-IL / MC, the ionic liquid is [bmim][p-CH3C6H4SO3], with a loading of 10%), and an inorganic support, MC, and 1g of polyethylene glycol (number-average molecular weight, 400). The reaction system was placed in a stainless steel autoclave, and carbon monoxide was introduced at a pressure of 4MPa at 120°C with stirring for 12 hours. After completion of the reaction, as determined by TLC, the mixture was diluted with 200mL of ethyl acetate and 200mL of water. The organic phase was then washed with saturated brine, concentrated to dryness, and purified by column chromatography to yield 4.75g of compound b (diethyl 2,6-naphthalenedicarboxylate) in a 50% yield.

[0043] Example 4

[0044] Dissolve 10 g of compound a (2,6-dibromonaphthalene) in DMA (100 mL), add triethylamine (7.06 g) and ethanol (8 g), then add 35 g (containing 0.5 mmol of palladium acetate, the supported ionic liquid is a palladium catalyst (Pd-TPPTS-IL / MC, the ionic liquid is [bmim][p-CH3C6H4SO3]), the loading is 10%, and the inorganic carrier is the catalyst carrier material MC) and 3 g of polyethylene glycol (number average molecular weight 400). The reaction system is placed in a stainless steel autoclave, carbon monoxide is introduced, the pressure is 4 MPa, and stirring is carried out at 120°C for 12 hours. After the reaction is detected by TLC, 200 mL of ethyl acetate and 200 mL of water are added for dilution, the organic phase is washed with saturated brine, and after being concentrated and dried, column chromatography is used for purification to obtain 5.7 g of compound b (2,6-naphthalene dicarboxylic acid diethyl ester), the yield is 59%.

[0045] Comparative Example 1

[0046] Dissolve 10 g of compound a (2,6-dibromonaphthalene) in DMA (100 mL), add triethylamine (7.06 g) and ethanol (8 g), then add 35 g (containing 0.5 mmol of palladium acetate, the supported ionic liquid is a palladium catalyst (Pd-TPPTS-IL / MC, the ionic liquid is [bmim][p-CH3C6H4SO3]), the loading is 10%, and the inorganic carrier is the catalyst carrier material MC). The reaction system is placed in a stainless steel autoclave, carbon monoxide is introduced, the pressure is 4 MPa, and stirring is carried out at 120°C for 12 hours. After the reaction is detected by TLC, 200 mL of ethyl acetate and 200 mL of water are added for dilution, the organic phase is washed with saturated brine, and after being concentrated and dried, column chromatography is used for purification to obtain 3.8 g of compound b (2,6-naphthalene dicarboxylic acid diethyl ester), the yield is 40%.

[0047] Example 5

[0048] Dissolve 10 g of compound a (2,6-dibromonaphthalene) in DMA (100 mL), add triethylamine (7.06 g) and ethanol (8 g), then add 35 g (containing 0.5 mmol of palladium acetate, the supported ionic liquid is a palladium catalyst (Pd-TPPTS-IL / AC, the ionic liquid is [bmim][p-CH3C6H4SO3]), the loading is 10%, and the inorganic carrier is the catalyst carrier material AC) and 2 g of polyethylene glycol (number average molecular weight 400). The reaction system is placed in a stainless steel autoclave, carbon monoxide is introduced, the pressure is 4 MPa, and stirring is performed at 120°C for 12 hours. After the reaction is detected by TLC, 200 mL of ethyl acetate and 200 mL of water are added for dilution, the organic phase is washed with saturated brine, and after being concentrated and dried, column chromatography is used for purification to obtain 6.18 g of compound b (2,6-naphthalene dicarboxylic acid diethyl ester), the yield is 65%.

[0049] Example 6

[0050] Dissolve 20 g of compound a (2,6-dibromonaphthalene) in DMA (200 mL), add triethylamine (14.1 g) and ethanol (16 g), then add 70 g (containing 1 mmol of palladium acetate, the supported ionic liquid is a palladium catalyst (Pd-TPPTS-IL / AC, the ionic liquid is [bmim][p-CH3C6H4SO3]), the loading is 10%, and the inorganic carrier is the catalyst carrier material AC) and 4 g of polyethylene glycol (number average molecular weight 400). The reaction system is placed in a stainless steel autoclave, carbon monoxide is introduced, the pressure is 4 MPa, and stirring is performed at 120°C for 12 hours. After the reaction is detected by TLC, 400 mL of ethyl acetate and 400 mL of water are added for dilution, the organic phase is washed with saturated brine, and after being concentrated and dried, column chromatography is used for purification to obtain 12.7 g of compound b (2,6-naphthalene dicarboxylic acid diethyl ester), the yield is 67%.

[0051] Comparative Example 2

[0052] Dissolve 10 g of compound a (2,6-dibromonaphthalene) in DMA (100 mL), add triethylamine (7.06 g) and ethanol (8 g), then add 35 g (containing 0.5 mmol of palladium acetate, the supported ionic liquid is a palladium catalyst (Pd-TPPTS-IL / AC, the ionic liquid is [bmim][p-CH3C6H4SO3]), the loading is 10%, and the inorganic carrier is the catalyst carrier material AC). The reaction system is placed in a stainless steel autoclave, carbon monoxide is introduced, the pressure is 4 MPa, and stirring is performed at 120°C for 12 hours. After the reaction is detected by TLC, 200 mL of ethyl acetate and 200 mL of water are added for dilution, the organic phase is washed with saturated brine, and after being concentrated and dried, column chromatography is used for purification to obtain 3.3 g of compound b (2,6-naphthalene dicarboxylic acid diethyl ester), the yield is 35%.

[0053] Example 7

[0054] Into a 100 mL reaction flask, compound b (diethyl 2,6-naphthalene dicarboxylate) (5 g) was added, followed by methanol (50 mL) and water (10 mL). Sodium hydroxide (2.94 g) was added in portions at room temperature. After the addition was completed, the reaction was stirred at 60 °C for 24 h. The reaction solution was concentrated to dryness, and the pH was adjusted to 3-4 using 3 M hydrochloric acid. A solid was precipitated, which was filtered, washed with deionized water, and dried to give 3.57 g of compound of formula I, i.e., 2,6-naphthalene dicarboxylic acid, in a yield of 90%.

[0055] As can be seen from the comparison between the examples and the comparative examples, the addition of polyethylene glycol can greatly improve the yield of step S1. We speculate that polyethylene glycol, as a surfactant, has good solubility in alcohol. It can dissolve the metal active component by complexing the oxygen atom with the metal ion in the catalyst, thereby improving the catalytic effect of the palladium catalyst.

[0056] The preferred embodiments of the present application are described in detail above. It should be understood that those of ordinary skill in the art can make many modifications and variations to the present application without departing from the spirit of the present application. Therefore, any technical solutions obtained by logical analysis, reasoning or limited experiments based on the concept of the present application and the prior art should be within the scope of protection defined by the claims.

Claims

1. A method for synthesizing 2,6-naphthalenedicarboxylic acid, characterized in that: The steps include: S1. Compound a is dissolved in an organic solvent, triethylamine, an alcohol, a catalyst, and a co-catalyst are added, and an oxidizing gas is introduced to react to obtain compound b; the solvent is selected from one or more of N,N-dimethylacetamide, N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide; the alcohol is ethanol, the catalyst is Pd-TPPTS-IL / AC, the co-catalyst is polyethylene glycol, and the oxidizing gas is carbon monoxide; the number average molecular weight of the polyethylene glycol is 400; the IL in the catalyst is an ionic liquid [bmim][p-CH3C6H4SO3]; S2. Compound b is mixed with alcohol and water, a base is added, and after the reaction, an acid is added to obtain a compound of formula I; The chemical structural formulas of the compound of formula I, compound a, and compound b are as follows:

2. The synthesis method according to claim 1, wherein The solvent in step S1 is N,N-dimethylacetamide.

3. The synthesis method according to claim 1, wherein The alcohol in step S2 is selected from one or both of methanol and ethanol; the base in step S2 is selected from one or more of sodium hydroxide, potassium hydroxide, and lithium hydroxide; the acid in step S2 is selected from one or more of hydrochloric acid, sulfuric acid, and hydrobromic acid.

4. The synthesis method according to any one of claims 1 or 3, characterized in that In step S2, the alcohol is methanol, the base is sodium hydroxide, and the acid is hydrochloric acid.

5. The synthesis method according to claim 1, characterized in that In step S1, the molar ratio of compound a, triethylamine, and ethanol is 1-2:2-5:5-10, the mass ratio of compound a to Pd-TPPTS-IL / AC and polyethylene glycol is 1-2:3.5-5:0.2-1; the mass is expressed in grams and the volume is expressed in milliliters, and the mass-to-volume ratio of compound a to N,N-dimethylacetamide is 1-5:10-50.

6. The synthesis method according to claim 5, characterized in that In step S1, the molar ratio of compound a, triethylamine, and ethanol is 1:2:5, the mass ratio of compound a to Pd-TPPTS-IL / AC and polyethylene glycol is 1:3.5:0.2; the mass is expressed in grams and the volume is expressed in milliliters, and the mass-to-volume ratio of compound a to N,N-dimethylacetamide is 1:

10.

7. The synthesis method according to claim 4, characterized in that In step S2, the molar ratio of compound b to sodium hydroxide is 1-2:4-10; the mass is expressed in grams and the volume is expressed in milliliters; the mass-volume ratio of compound b to methanol and water is 1-2:10-20:2-5.

8. The synthesis method according to claim 7, characterized in that In step S2, the molar ratio of compound b to sodium hydroxide is 1:4; the mass in grams and the volume in milliliters, and the mass-to-volume ratio of compound b to methanol and water is 1:10:2.

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