Synthetic method of p-dimethylaminobenzoic acid

Abstract

The invention relates to the technical field of fine chemical synthesis, and particularly discloses a synthesis method of p-dimethylaminobenzoic acid. The synthesis method comprises the following steps: adding p-dimethylaminobenzaldehyde, a photoinitiator and alkali into a solvent, carrying out a heat preservation reaction at 65-75 DEG C until the reaction is completed, adjusting the pH value to be acidic, and carrying out reduced pressure evaporation to dryness of the solvent by using a rotary evaporator to obtain a crude product of p-dimethylaminobenzoic acid; and impurity removal: adding methanol into the p-dimethylaminobenzoic acid crude product, pulping, filtering, adding methanol again, pulping at 45-55 DEG C, filtering, and drying to obtain a p-dimethylaminobenzoic acid fine product. The preparation method is simple, Ag2O or silver nitrate does not need to be adopted, peroxide and halogenated hydrocarbon are not involved, explosive gas is not generated in the reaction process, the reaction condition is mild, toxicity is small, the raw material storage requirement is low, the enterprise safety risk is reduced, the solvent and methyl alcohol are recycled, little waste water is generated, and energy conservation and environmental protection are achieved.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of fine chemical synthesis, and in particular to a synthesis method of p-dimethylaminobenzoic acid. BACKGROUND

[0002] P-dimethylaminobenzoic acid (4-dimethylaminobenzoic acid) is an important organic synthesis intermediate. P-dimethylaminobenzoic acid is esterified to prepare a series of compounds which are widely used in various fields such as cosmetics, coatings, electronic industry, printing industry, adhesives and the like.

[0003] P-dimethylaminobenzoic acid production includes the following methods: (1) carboxylation of p-dimethylaminobenzene halide; (2) methylation of p-aminobenzoic acid; (3) direct oxidation of p-dimethylaminobenzaldehyde. Methods (1) and (2) have high raw material cost, great toxicity, and unsafe operation, and are not suitable for large-scale industrial production. Therefore, p-dimethylaminobenzaldehyde oxidation is mostly used for industrial production.

[0004] A synthesis method of p-dimethylaminobenzoic acid is disclosed in "Synthesis of p-dimethylaminobenzoic acid", Xie Chuan, Liu Jian, Li Haiyan, Synthetic Chemistry, Journal, which synthesizes p-dimethylaminobenzoic acid by air oxidation method with Ag2O as a catalyst and dimethylaminobenzaldehyde as a raw material, and the highest yield is 76.9%.

[0005] A synthesis method of p-dimethylaminobenzoic acid is disclosed in "Research on synthesis of p-dimethylaminobenzoic acid", Peng Mengxia, Chen Ziyun, Huang Xiushan, Journal of Southwest China Normal University (Natural Science Edition), Journal, which synthesizes p-dimethylaminobenzoic acid with p-dimethylaminobenzaldehyde and silver nitrate as raw materials. The best conditions are: the reaction temperature is 60 DEG C, the molar feed ratio of p-dimethylaminobenzaldehyde to silver nitrate is 1:2, the reaction time is 24 h, the concentration of the solvent sodium hydroxide aqueous solution is 7%, and the product yield is 79.2%.

[0006] The applicant believes that the yield of p-dimethylaminobenzoic acid is insufficient, the utilization rate of raw materials is low, and the production cost is high, so a synthesis method of p-dimethylaminobenzoic acid with high yield needs to be developed. SUMMARY

[0007] In order to improve the yield of p-dimethylaminobenzoic acid synthesis, the application provides a synthesis method of p-dimethylaminobenzoic acid.

[0008] The synthesis method of p-dimethylaminobenzoic acid provided by the application adopts the following technical scheme: A method comprising the following steps: adding p-dimethylaminobenzaldehyde and an alpha-hydroxy ketone photoinitiator, sodium hydroxide into a solvent, incubating at 65-75 DEG C until the reaction is completed, adjusting the pH value to be acidic, and using a rotary evaporator to evaporate the solvent under reduced pressure to obtain a crude p-dimethylaminobenzoic acid.

[0009] By adopting the technical scheme, the reaction structural formula is as follows:

[0010] The preparation method is simple, and the production process of preparing p-dimethylaminobenzaldehyde into p-dimethylaminobenzoic acid does not need to use Ag2O or silver nitrate, does not involve peroxide and halogenated hydrocarbon, no explosive gas is generated in the reaction process, the reaction condition is mild and the toxicity is small, the raw material storage requirement is low, the enterprise safety risk is reduced. And the alpha-hydroxy ketone photoinitiator is used instead of metal catalyst, free radicals are generated under visible light / ultraviolet light, the conversion of aldehyde group to carboxyl group is driven, the reaction condition is mild (65-75 DEG C), the mass yield is more than 90%, the reaction time is short, the solvent is recycled by using a rotary evaporator to evaporate the solvent under reduced pressure, the COD content in the generated wastewater is small, energy saving and environmental protection are achieved.

[0011] Optionally, the method further comprises a step of removing impurities: the crude p-dimethylaminobenzoic acid is added with methanol for beating, then filtered, and then added with methanol for beating at 45-55 DEG C, filtered, and dried to obtain fine p-dimethylaminobenzoic acid.

[0012] By adopting the technical scheme, the impurities are removed conveniently and simply, the methanol added later can be directly recycled and used for the first time in the next impurity removal, the methanol can be recycled and utilized, raw materials are saved, and costs are reduced.

[0013] Optionally, the photoinitiator is one of photoinitiator 184, photoinitiator 2959, photoinitiator 1173, photoinitiator 784, photoinitiator TPO or photoinitiator 819.

[0014] By adopting the technical scheme, Optionally, the photoinitiator is photoinitiator 184.

[0015] By adopting the technical scheme, photoinitiator 184 is not sensitive to oxygen, and is chemically stable under light-proof conditions, convenient to store, and relatively safe. Photoinitiator 184 has the best effect, and the mass yield reaches 94.7%.

[0016] Optionally, the pH value is adjusted to 6-7.

[0017] By adopting the technical scheme, after the reaction is completed, there are more sodium dimethylaminobenzoate in the alkaline environment, after adjusting the pH to 6-7, the by-product is reduced, and at the same time, an acidic environment is provided, the product is easily precipitated, and the yield is improved.

[0018] Optionally, the drying temperature is 75-85°C.

[0019] Optionally, the solvent is one of ethylene glycol ether or propylene glycol methyl ether.

[0020] By adopting the technical scheme, ethylene glycol ether or propylene glycol methyl ether is used as the solvent, the ether bond structure forms a hydrogen bond network with the carbonyl group of the photoinitiator 184, the low polarity inhibits the Cannizzaro side reaction, and the by-product is reduced.

[0021] Optionally, the mass fractions of the p-dimethylaminobenzaldehyde, sodium hydroxide and the photoinitiator 184 are 22-28 parts, 12-15 parts and 4.7-5.3 parts.

[0022] By adopting the technical scheme, the component fraction is appropriate, the reaction completion rate is high, and the waste of raw materials is unlikely.

[0023] In summary, the present application has at least one of the following beneficial technical effects: 1. The preparation method is simple, does not need to use Ag2O or silver nitrate, does not involve peroxide and halogenated hydrocarbon, no explosive gas is generated in the reaction process, the reaction condition is mild and the toxicity is small, the raw material storage requirement is low, and the enterprise safety risk is reduced; 2. And the present application uses an alpha-hydroxy ketone photoinitiator to replace a metal catalyst, generates free radicals under visible light / ultraviolet light, drives the conversion of aldehyde group→carboxyl group, the reaction condition is mild (65-75°C), the mass yield is 90-95%, the reaction time is short, and the production efficiency is improved; 3. The solvent and methanol are recycled, less wastewater is generated, and energy saving and environmental protection are achieved; 4. Ethylene glycol ether or propylene glycol methyl ether is used as the solvent, the ether bond structure forms a hydrogen bond network with the carbonyl group of the photoinitiator 184, has a synergistic effect, improves the free radical generation efficiency, and thus the catalytic effect is better and the yield is improved. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 is the liquid chromatogram of the crude p-dimethylaminobenzoic acid of Example 1.

[0025] Figure 2 is the liquid chromatogram of the fine p-dimethylaminobenzoic acid product of Example 1.

[0026] Figure 3 is the liquid chromatogram of the dimethylaminobenzoic acid purchased on the market, as a product control.

[0027] Figure 4 Liquid chromatogram of the raw material of p-dimethylaminobenzaldehyde for Example 1.

[0028] Figure 5 Liquid chromatogram of the reaction solution at the beginning of the reaction for Example 1.

[0029] Figure 6 Liquid chromatogram of the reaction solution at the end of the reaction for Example 1. DETAILED DESCRIPTION

[0030] The present application is further described in conjunction with the following examples.

[0031] Raw materials: p-dimethylaminobenzaldehyde (industrial grade), sodium hydroxide (industrial grade), potassium hydroxide (industrial grade), photoinitiator 184 (1-hydroxycyclohexyl phenyl ketone, industrial grade), photoinitiator 2959 (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, industrial grade), photoinitiator 127 (2-hydroxy-2-methyl-1-phenyl-1-propanone, industrial grade), photoinitiator 1173 (2-hydroxy-2-methyl-1-phenyl-1-propanone, industrial grade), photoinitiator 784 (industrial grade), photoinitiator TPO (industrial grade), photoinitiator 819 (industrial grade), ethylene glycol ethyl ether (reagent grade), propylene glycol methyl ether (reagent grade), ethylene glycol methyl ether (reagent grade), dimethyl formamide (reagent grade), dimethyl acetamide (reagent grade), methanol (industrial grade), refined hydrochloric acid (industrial grade).

[0032] Example 1

[0033] The synthesis method of p-dimethylaminobenzoic acid includes the following steps: p-dimethylaminobenzaldehyde 25 g, photoinitiator 184 5 g, sodium hydroxide 12.5 g, are added to 100 ml ethylene glycol ethyl ether, and reacted at 70°C for 15 h. The pH value is adjusted to 6.6 with refined hydrochloric acid, and the solvent is evaporated at reduced pressure with a rotary evaporator at 70°C to obtain crude p-dimethylaminobenzoic acid.

[0034] The crude p-dimethylaminobenzoic acid is added with 125 ml of methanol for beating, then filtered, and again added with 125 ml of methanol for beating at 50°C, filtered, and dried in an oven at 80°C to obtain fine p-dimethylaminobenzoic acid 24.11 with a weight yield of 96.0%.

[0035] Example 2 The synthesis method of p-dimethylaminobenzoic acid comprises the following steps: adding p-dimethylaminobenzaldehyde 22 g, photoinitiator 184 4.7 g, sodium hydroxide 12 g into 100 ml ethylene glycol ether, keeping at 65 ℃ for 16 h, adjusting the pH value to 6.1 by refined hydrochloric acid, and evaporating the solvent at 70 ℃ under reduced pressure to obtain the crude p-dimethylaminobenzoic acid.

[0036] The crude p-dimethylaminobenzoic acid is added with 125 ml of methanol for beating, and then filtered, and then added with 125 ml of methanol for beating at 45 ℃, filtered, and dried in an oven at 80 ℃ to obtain the fine p-dimethylaminobenzoic acid 21.08 g, with a weight yield of 95.8%.

[0037] Example 3 The synthesis method of p-dimethylaminobenzoic acid comprises the following steps: adding p-dimethylaminobenzaldehyde 22 g, photoinitiator 184 4.7 g, sodium hydroxide 12 g into 100 ml ethylene glycol ether, keeping at 65 ℃ for 16 h, adjusting the pH value to 6.1 by refined hydrochloric acid, and evaporating the solvent at 70 ℃ under reduced pressure to obtain the crude p-dimethylaminobenzoic acid.

[0038] The crude p-dimethylaminobenzoic acid is added with 125 ml of methanol for beating, and then filtered, and then added with 125 ml of methanol for beating at 45 ℃, filtered, and dried in an oven at 80 ℃ to obtain the fine p-dimethylaminobenzoic acid 21.08 g, with a weight yield of 95.8%.

[0039] Example 4 The difference from example 1 is that the equal mass of photoinitiator 1773 is used to replace the photoinitiator 184, and the weight yield is 93.6%.

[0040] Example 5 The difference from example 1 is that the equal mass of photoinitiator 127 is used to replace the photoinitiator 184, and the weight yield is 91.2%.

[0041] Example 6 The difference from example 1 is that the equal mass of photoinitiator 2959 is used to replace the photoinitiator 184, and the weight yield is 90.3%.

[0042] Example 7 The difference from example 1 is that the equal mass of photoinitiator 784 is used to replace the photoinitiator 184, and the weight yield is 87.3%.

[0043] Example 8 The difference from example 1 is that the equal mass of photoinitiator TPO is used to replace the photoinitiator 184, and the weight yield is 88.5%.

[0044] Example 9 The difference from Example 1 is that equal mass of photoinitiator 819 replaces photoinitiator 184, and the weight yield is 89.1%.

[0045] Example 10 The difference from Example 1 is that equal volume of propylene glycol methyl ether replaces ethylene glycol ethyl ether, and the weight yield is 95.9%.

[0046] Example 11 The difference from Example 1 is that equal volume of ethylene glycol methyl ether replaces ethylene glycol ethyl ether, and the weight yield is 95.2%.

[0047] Example 12 The difference from Example 1 is that equal volume of dimethyl formamide replaces ethylene glycol ethyl ether, and the weight yield is 89.1%.

[0048] Example 13 The difference from Example 1 is that equal volume of dimethyl acetamide replaces ethylene glycol ethyl ether, and the weight yield is 90.6%.

[0049] Example 14 The difference from Example 1 is that potassium hydroxide is used to adjust the pH to 6.5, and the weight yield is 96.0%.

[0050] Comparative Example 1 The difference from Example 1 is that no initiator is added, and no reaction occurs, with a yield of 0%. From the experimental data of Example 1 and Examples 4-9, it can be seen that the yield is highest when photoinitiator 184 is used.

[0051] From the experimental data of Example 1 and Examples 10-13, it can be seen that when propylene glycol methyl ether, ethylene glycol methyl ether, dimethyl formamide, and dimethyl acetamide are used to replace ethylene glycol ethyl ether as a solvent, the reaction yield is better when ethylene glycol ethyl ether, propylene glycol methyl ether, and ethylene glycol methyl ether are used as solvents, with a yield of over 95%. When dimethyl formamide and dimethyl acetamide are used as solvents, the reaction yield is poorer.

[0052] In summary, the present application develops a new preparation scheme for p-dimethylaminobenzoic acid, which has the advantages of simple preparation method, mild reaction conditions, low toxicity, low raw material storage requirement, and reduced enterprise safety risk. The solvent and methanol are recycled, less wastewater is generated, and energy saving and environmental protection are achieved. When ethylene glycol ethyl ether or propylene glycol methyl ether is used as a solvent, the ether bond structure forms a hydrogen bond network with the carbonyl group of photoinitiator 184, has a synergistic effect, improves the efficiency of free radical generation, and thus the catalytic effect is better and the yield is improved.

[0053] Experiment: Liquid chromatography is used to analyze the following substances: The solvent is methanol, the solute concentration is 10 mg / ml, and the solute is the crude p-dimethylaminobenzoic acid of Example 1, the fine p-dimethylaminobenzoic acid of Example 1, commercially available p-dimethylaminobenzoic acid, raw material p-dimethylaminobenzaldehyde, reaction initial liquid, and reaction end liquid. This embodiment is merely an explanation of the present application and is not a limitation of the present application. Those skilled in the art can make modifications to this embodiment without creative contribution after reading the present specification, but as long as the modifications are within the scope of the claims of the present application, they are protected by the Patent Law.

Claims

1. A method for synthesizing p-dimethylaminobenzoic acid, characterized in that, The process includes the following steps: adding p-dimethylaminobenzoaldehyde, a photoinitiator, and an alkali to a solvent, maintaining the temperature at 65-75℃ until the reaction is complete, adjusting the pH to acidic, and then using a rotary evaporator to evaporate the solvent under reduced pressure to obtain crude p-dimethylaminobenzoic acid.

2. The method for synthesizing p-dimethylaminobenzoic acid according to claim 1, characterized in that: It also includes a purification step: methanol is added to the crude dimethylaminobenzoic acid and pulped, then filtered, methanol is added again and pulped at 45-55℃, filtered, and dried to obtain the refined dimethylaminobenzoic acid.

3. The method for synthesizing p-dimethylaminobenzoic acid according to claim 1, characterized in that: The photoinitiator is one of photoinitiator 184, photoinitiator 2959, photoinitiator 1173, photoinitiator 784, photoinitiator TPO, or photoinitiator 819.

4. The method for synthesizing p-dimethylaminobenzoic acid according to claim 1, characterized in that: The photoinitiator is photoinitiator 184.

5. The method for synthesizing p-dimethylaminobenzoic acid according to claim 1, characterized in that: Adjust the pH value to 6-7.

6. The method for synthesizing p-dimethylaminobenzoic acid according to claim 1, characterized in that: Drying is carried out in an oven at a temperature of 75-85℃.

7. The method for synthesizing p-dimethylaminobenzoic acid according to claim 1, characterized in that: The solvent is one of ethylene glycol ethyl ether, propylene glycol methyl ether, ethylene glycol methyl ether, dimethylformamide, or dimethylacetamide.

8. The method for synthesizing p-dimethylaminobenzoic acid according to claim 3, characterized in that: By weight, the amounts of p-dimethylaminobenzaldehyde, sodium hydroxide, and photoinitiator 184 are 22-28 parts, 12-15 parts, and 4.7-5.3 parts, respectively.

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