A p-dimethylaminobenzoic acid isooctyl ester and a method for preparing the same

Abstract

The application discloses p-dimethylaminobenzoic acid isooctyl ester and a preparation method thereof, and comprises the following steps: under alkaline conditions, p-dimethylaminobenzoic acid isooctyl ester is prepared by using p-aminobenzoic acid isooctyl ester and dimethyl carbonate as raw materials to carry out a methylation reaction; compared with the prior art, the raw materials are p-aminobenzoic acid isooctyl ester and dimethyl carbonate, wherein the dimethyl carbonate is used as a methylation reagent and a reaction solvent at the same time, the condition is mild, the post-treatment is simple, the purity of the product is above 99%, the yield is above 90%, and the comprehensive cost is reduced.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, specifically to isooctyl p-dimethylaminobenzoate and its preparation method. Background Technology

[0002] Isooctyl p-dimethylaminobenzoate is a good UVB absorber and has the following chemical structural formula:

[0003] .

[0004] Currently, isooctyl p-dimethylaminobenzoate is widely used in cosmetics, coatings, electronics, printing, adhesives, and other fields. In cosmetic sunscreens, the US FDA lists it as a Category 1 recommended sunscreen agent. Therefore, developing low-cost, green, efficient, and environmentally friendly preparation processes is essential.

[0005] The following are the main methods for preparing isooctyl p-dimethylaminobenzoate:

[0006] The first method involves using p-dimethylaminobenzaldehyde as a raw material, preparing p-dimethylaminobenzoic acid through an oxidation reaction, and then condensing it with isooctyl alcohol to form an ester.

[0007] Specifically, this method was reported in Chemical Industry Journal, November 12, 2005, which involves oxidizing p-dimethylaminobenzaldehyde to p-dimethylaminobenzoic acid in the presence of ammonia / silver nitrate, followed by condensation with isooctanol under acidic catalysis to form an ester. This process uses silver nitrate, is costly, and has no industrial application value.

[0008] Furthermore, CN10337225B discloses a method for synthesizing p-dimethylaminoisooctyl ester using p-aminobenzaldehyde as a raw material in a one-pot process with ferric perchlorate, hydrogen peroxide, and isooctyl alcohol. This method requires the use of hydrogen peroxide, which poses a high risk for industrial scale-up (hydrogen peroxide easily decomposes to produce oxygen, and large-scale production is prone to combustion and explosion).

[0009] The second method involves synthesizing isooctyl p-dimethylaminobenzoate from p-nitrobenzoic acid through three steps: esterification, nitro reduction, and methylation.

[0010] Specifically, the following scheme was reported in *Daily Chemical Industry*, 2003, Vol. 33, No. 2, 091: p-Nitrobenzoic acid and isooctyl alcohol are reacted with concentrated sulfuric acid to produce isooctyl p-nitrobenzoate; isooctyl p-nitrobenzoate is then catalytically hydrogenated and reduced to an amino group under methanol / Raney nickel conditions to obtain isooctyl p-aminobenzoate; and isooctyl p-dimethylaminobenzoate is then reduced and aminationed under Raney nickel / formaldehyde conditions to obtain isooctyl p-dimethylaminobenzoate. The latter two steps of this process require the use of Raney nickel, resulting in high costs and flammability during industrial scale-up, posing a high EHS risk.

[0011] The third method involves synthesizing isooctyl p-dimethylaminobenzoate in two steps: substitution with dimethylamine and esterification, using p-chlorobenzoic acid as the raw material.

[0012] Specifically, CN101863791A discloses a method that uses p-chlorobenzoic acid as a raw material and reacts it with an aqueous solution of dimethylamine under catalytic conditions to produce p-dimethylaminobenzoic acid, which is then condensed with isooctanol under acidic conditions to form an ester. This method introduces the heavy metal copper as a catalyst and produces high levels of acidic wastewater, making it environmentally unfriendly.

[0013] In summary, existing technologies generally suffer from drawbacks such as high cost, high EHS risk in industrial scale-up, environmental unfriendliness, or cumbersome operation. Summary of the Invention

[0014] In view of the shortcomings of the prior art, the purpose of this invention is to provide isooctyl p-dimethylaminobenzoate and its preparation method, so as to solve the disadvantages of the prior art, such as high cost, high EHS risk in industrial scale-up, environmental unfriendliness, or cumbersome operation.

[0015] To achieve the above objectives, the first aspect of the present invention adopts the following technical solution: a method for preparing isooctyl p-dimethylaminobenzoate, comprising the following steps: under alkaline conditions, isooctyl p-aminobenzoate and dimethyl carbonate are used as raw materials to carry out a methylation reaction to prepare isooctyl p-dimethylaminobenzoate.

[0016] Technical principle:

[0017] This reaction is a methylation reaction, specifically the N-methylation of amines. The reaction formula is:

[0018]

[0019] Under alkaline conditions, the aromatic primary amino group (–NH2) in isooctyl p-aminobenzoate acts as a nucleophile, attacking the methyl carbon in dimethyl carbonate (DMC) in two separate nucleophilic substitution reactions to ultimately generate a tertiary amine (–N(CH3)2). Each step of the reaction releases one molecule of methanol and carbon dioxide, achieving overall dimethylation of the amino group. This reaction utilizes DMC as an environmentally friendly methylating agent and reaction solvent, demonstrating the characteristics of green synthetic chemistry.

[0020] Furthermore, the mass ratio of isooctyl p-aminobenzoate to dimethyl carbonate is 1:3.0~5.0.

[0021] Furthermore, the alkali is selected from one or more of potassium carbonate, sodium carbonate, and cesium carbonate.

[0022] Furthermore, the molar ratio of the base to isooctyl p-aminobenzoate is 0.5~1.0:1.

[0023] Furthermore, the methylation reaction is carried out at a temperature of 150~180℃.

[0024] Furthermore, after the methylation reaction, the resulting reaction solution is sequentially filtered and distilled.

[0025] Furthermore, the filtration process includes a step of washing the alkali with dimethyl carbonate.

[0026] Furthermore, the distillation includes sequential atmospheric distillation and vacuum distillation, and the fore-distillate separated in the atmospheric distillation is recovered and reused.

[0027] Furthermore, the temperature of atmospheric distillation is 100~150℃, and the temperature of vacuum distillation is 190~210℃.

[0028] The second aspect of the present invention adopts the following technical solution: an isooctyl p-dimethylaminobenzoate, prepared by the method for preparing isooctyl p-dimethylaminobenzoate described in the first aspect of the present invention.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] 1. This invention uses isooctyl p-aminobenzoate and dimethyl carbonate as raw materials, wherein dimethyl carbonate is used as a methylating agent, which has mild conditions, simple post-processing, and a product purity of over 99% and a yield of 90% or more, thereby reducing the overall cost.

[0031] 2. In this invention, dimethyl carbonate is used as a green solvent that can be recycled and reused, making it environmentally friendly, green, and pollution-free, and suitable for industrial scale-up.

[0032] 3. The synthetic route of this invention involves only one reaction, which is simple, efficient, and highly atom-economical. Attached Figure Description

[0033] Figure 1 The HPLC chromatogram of isooctyl p-dimethylaminobenzoate prepared in Example 1 of the present invention;

[0034] Figure 2 The HPLC chromatogram of isooctyl p-dimethylaminobenzoate prepared in Example 2 of the present invention;

[0035] Figure 3 The HPLC chromatogram of isooctyl p-dimethylaminobenzoate prepared in Example 3 of the present invention is shown. Detailed Implementation

[0036] The first aspect of the present invention adopts the following technical solution: a method for preparing isooctyl p-dimethylaminobenzoate, comprising the following steps: under alkaline conditions, isooctyl p-aminobenzoate and dimethyl carbonate are used as raw materials to carry out a methylation reaction to prepare isooctyl p-dimethylaminobenzoate.

[0037] In this invention, the mass ratio of isooctyl para-aminobenzoate to dimethyl carbonate is preferably 1:3.0~5.0, more preferably 1:3.0~4.0.

[0038] In this invention, the alkali is preferably one or more of potassium carbonate, sodium carbonate, and cesium carbonate, more preferably potassium carbonate, and most preferably a mixture of potassium carbonate and cesium carbonate; in a specific embodiment of this invention, the molar ratio of cesium carbonate to potassium carbonate is preferably 1:2 to 1:6, more preferably 1:3 to 1:5.

[0039] In this invention, the molar ratio of the alkali to isooctyl p-aminobenzoate is preferably 0.5 to 1.0:1, more preferably 0.6 to 1:1.

[0040] In this invention, the preferred temperature for the methylation reaction is 150~180°C.

[0041] The present invention further includes the following steps: after the methylation reaction, the resulting reaction solution is cooled, filtered and distilled in sequence; the present invention preferably lowers the temperature of the reaction solution to 20~50°C, more preferably to 20~40°C.

[0042] In this invention, the filtration process includes a step of washing the alkali with dimethyl carbonate; there is no limitation on the number of washes or the amount of dimethyl carbonate used in each wash, but a small amount used multiple times is preferred.

[0043] In this invention, the distillation includes atmospheric distillation and vacuum distillation performed sequentially. First, atmospheric distillation is used to separate the fore fraction, and then vacuum distillation is used to separate the main fraction. The fore fraction is recovered and reused, and the main fraction is isooctyl p-dimethylaminobenzoate.

[0044] In this invention, the temperature of atmospheric distillation is 100~150℃, and the temperature of vacuum distillation is 190~210℃.

[0045] The second aspect of the present invention adopts the following technical solution: an isooctyl p-dimethylaminobenzoate, which is prepared by the preparation method of isooctyl p-dimethylaminobenzoate described in the first aspect of the present invention.

[0046] In this invention, dimethyl carbonate is used as the methylating agent and reaction solvent. The conditions are mild, the post-processing is simple, the product yield and purity are high, and the dimethyl carbonate can be recycled and reused, resulting in low overall cost. In addition, the synthetic route of this invention has only one step, which is simple, efficient and atom-economical.

[0047] The present invention will be further described in detail below through specific embodiments:

[0048] Example 1

[0049] Add 100g of isooctyl p-aminobenzoate, 300g of dimethyl carbonate, and 55.2g of potassium carbonate to a high-pressure reactor. Purge with nitrogen, start stirring, and adjust the reaction system temperature to 150℃. Control the reaction system temperature at 150℃ for 12 hours, take samples for monitoring, and detect when the reaction reaches the endpoint.

[0050] After cooling the reaction solution to 20°C, filter it and wash the filter cake with 100g of dimethyl carbonate. Combine the washing liquid with the filtrate.

[0051] The filtrate was distilled at 110°C under normal pressure to remove dimethyl carbonate solvent until no forefraction remained. The removed solvent was then recycled.

[0052] The concentrated residual reaction solution was distilled under reduced pressure at 190℃ to obtain 102.9 g of the main fraction, isooctyl dimethylaminobenzoate.

[0053] According to testing and calculation, the product prepared in this embodiment has a yield of 93.0% and a purity of 99.75%.

[0054] Example 2

[0055] Add 100g of isooctyl p-aminobenzoate, 400g of dimethyl carbonate, and 27.6g of potassium carbonate to a high-pressure reactor. Purge with nitrogen, start stirring, and adjust the reaction system temperature to 180℃. Control the reaction system temperature at 180℃ for 12 hours, take samples for monitoring, and detect when the reaction reaches the endpoint.

[0056] After cooling the reaction solution to 40°C, filter it and wash the filter cake with 100g of dimethyl carbonate. Combine the washing liquid with the filtrate.

[0057] The filtrate was distilled at 115°C under normal pressure to remove dimethyl carbonate solvent until no forefraction remained. The removed solvent was then recycled.

[0058] The concentrated residual reaction solution was distilled under reduced pressure at 210℃ to obtain 101.2 g of the main fraction, isooctyl dimethylaminobenzoate.

[0059] According to testing and calculation, the product prepared in this embodiment has a yield of 91.0% and a purity of 99.49%.

[0060] Example 3

[0061] Add 100g of isooctyl p-aminobenzoate, 500g of dimethyl carbonate, and 42.4g of sodium carbonate to a high-pressure reactor. Purge with nitrogen, start stirring, and adjust the reaction system temperature to 160℃. Control the reaction system temperature at 160℃ for 12 hours, take samples for monitoring, and detect when the reaction reaches the endpoint.

[0062] After cooling the reaction solution to 28°C, filter it and wash the filter cake with 100g of dimethyl carbonate. Combine the washing liquid with the filtrate.

[0063] The filtrate was distilled at 135°C under normal pressure to remove dimethyl carbonate solvent until no forefraction remained. The removed solvent was then recycled.

[0064] The concentrated residual reaction solution was distilled under reduced pressure at 198°C to obtain 102.3 g of the main fraction, isooctyl dimethylaminobenzoate.

[0065] According to testing and calculation, the product prepared in this embodiment has a yield of 92.0% and a purity of 99.02%.

[0066] Example 4

[0067] 100g of isooctyl p-aminobenzoate, 400g of dimethyl carbonate, and 97.7g of cesium carbonate were added to a high-pressure reactor. Nitrogen was used to purge the reactor, stirring was started, and the temperature of the reaction system was adjusted to 170℃. The reaction system was controlled at 170℃ for 12 hours, and samples were taken to monitor the reaction and detect when the endpoint was reached.

[0068] After cooling the reaction solution to 35°C, filter it and wash the filter cake with 100g of dimethyl carbonate. Combine the washing liquid with the filtrate.

[0069] The filtrate was distilled at 140°C under normal pressure to remove dimethyl carbonate solvent until no forefraction remained. The removed solvent was then recycled.

[0070] The concentrated residual reaction solution was distilled under reduced pressure at 205℃ to obtain 100.1 g of the main fraction, isooctyl dimethylaminobenzoate.

[0071] Based on testing and calculations, the product prepared in this embodiment has a yield of 90.0% and a purity of 99.1%.

[0072] Example 5

[0073] Add 100g of isooctyl p-aminobenzoate, 500g of dimethyl carbonate, 16.3g of cesium carbonate and 20.7g of potassium carbonate to a high-pressure reactor, purge with nitrogen, turn on the stirrer and adjust the reaction system temperature to 160℃; control the reaction system temperature at 160℃ for 12 hours, take samples for monitoring, and detect when the reaction reaches the endpoint;

[0074] After cooling the reaction solution to 35°C, filter it and wash the filter cake with 100g of dimethyl carbonate. Combine the washing liquid with the filtrate.

[0075] The filtrate was distilled at 120°C under normal pressure to remove dimethyl carbonate solvent until no forefraction remained. The removed solvent was then recycled.

[0076] The concentrated residual reaction solution was distilled under reduced pressure at 205℃ to obtain 103.0 g of the main fraction, isooctyl dimethylaminobenzoate.

[0077] According to testing and calculation, the product prepared in this embodiment has a yield of 92.5% and a purity of 99.1%.

[0078] Comparative Example 1

[0079] The only difference from Example 1 is that the amount of potassium carbonate used is adjusted from 55.2g to 61g.

[0080] According to testing and calculation, the product prepared in this embodiment has a yield of 88.5% and a purity of 98.5%.

[0081] Comparative Example 2

[0082] The only difference from Example 1 is that the amount of potassium carbonate used is adjusted from 55.2g to 25g.

[0083] According to testing and calculation, the product prepared in this embodiment has a yield of 86.5% and a purity of 98.8%.

[0084] Comparative Example 3

[0085] The only difference from Example 5 is that the amount of cesium carbonate used is adjusted from 16.3g to 48.82g.

[0086] According to testing and calculation, the product prepared in this embodiment has a yield of 75.2% and a purity of 98.1%.

[0087] Comparative Example 4

[0088] The only difference from Example 5 is that the amount of cesium carbonate used is adjusted from 16.3g to 6.97g.

[0089] According to testing and calculation, the product prepared in this embodiment has a yield of 81.5% and a purity of 97.5%.

[0090] Comparative Example 5

[0091] The only difference from Example 1 is that the potassium carbonate is replaced with an equal amount of NaY zeolite.

[0092] According to testing and calculation, the product yield prepared in this example was 72.3%, and the purity was 98.0%. The product yield and purity in this comparative example are significantly lower than those in Example 1. This may be because isooctyl p-aminobenzoate is a substrate with long-chain, sterically hindered substituents. Due to its large molecular size, its diffusion and effective adsorption within the NaY zeolite channels are limited, resulting in low reactivity and unsatisfactory selectivity. Furthermore, NaY zeolite is easily deactivated by steric hindrance, leading to relatively low product yield and purity.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A process for the preparation of p-dimethylamino benzoic acid isooctyl ester, characterized in that, Includes the following steps: Isooctyl p-dimethylaminobenzoate was prepared by methylation reaction using isooctyl p-aminobenzoate and dimethyl carbonate as raw materials under alkaline conditions.

2. The method for preparing isooctyl p-dimethylaminobenzoate according to claim 1, characterized in that, The mass ratio of isooctyl p-aminobenzoate to dimethyl carbonate is 1:3.0~5.

0.

3. The method for preparing isooctyl p-dimethylaminobenzoate according to claim 1, characterized in that, The alkali is selected from one or more of potassium carbonate, sodium carbonate, and cesium carbonate.

4. A method for preparing isooctyl p-dimethylaminobenzoate according to claim 1 or 3, characterized in that, The molar ratio of the base to isooctyl p-aminobenzoate is 0.5~1.0:

1.

5. The method for preparing isooctyl p-dimethylaminobenzoate according to claim 1, characterized in that, The methylation reaction is carried out at a temperature of 150~180℃.

6. A method for preparing isooctyl p-dimethylaminobenzoate according to claim 1, 2, 3 or 5, characterized in that, The methylation reaction is followed by sequential filtration and distillation of the resulting reaction solution.

7. The method for preparing isooctyl p-dimethylaminobenzoate according to claim 6, characterized in that, The filtration process includes a step of washing with alkali using dimethyl carbonate.

8. The method for preparing isooctyl p-dimethylaminobenzoate according to claim 6, characterized in that, The distillation includes sequential atmospheric distillation and vacuum distillation, and the fore-fraction separated in the atmospheric distillation is recovered and reused.

9. The method for preparing isooctyl p-dimethylaminobenzoate according to claim 8, characterized in that, The atmospheric distillation temperature is 100~150℃, and the vacuum distillation temperature is 190~210℃.

10. An isooctyl p-dimethylaminobenzoate, characterized in that, It is prepared by any one of the methods for preparing isooctyl p-dimethylaminobenzoate according to claims 1-9.

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