Metal complex catalyst and preparation method of 2,4,4-trimethyladipic acid

Abstract

The present invention relates to a metal complex catalyst and a method for preparing 2,4,4-trimethyladipic acid. The metal complex catalyst is used for preparing 2,4,4-trimethyladipic acid, and the metal complex catalyst comprises a transition metal salt and a ligand. Among them, the ligand is selected from at least one of them, wherein R<subgt;1< / subgt; is selected from a halogen element, hydrogen, methyl, ethyl or methoxy, R<subgt;2< / subgt> is selected from a halogen element, hydrogen, methyl, ethyl, tert-butyl or methoxy, and R<subgt;3< / subgt> and R<subgt;4< / subgt> are each independently selected from hydrogen or methyl. The metal complex catalyst can be used for the selective preparation of 2,4,4-trimethyladipic acid, and high-purity and high-yield 2,4,4-trimethyladipic acid can be obtained through simple crystallization post-treatment.

Description

Technical Field

[0001] The present invention relates to the field of fine chemical synthesis, and in particular to a metal complex catalyst and a preparation method of 2,4,4-trimethyladipic acid. Background Art

[0002] Trimethyladipic acid, like adipic acid, is a dicarboxylic acid that can be polycondensed with diamines or diols to form high molecular polymers. It can be used as a raw material for medicines, pesticides, adhesives, synthetic leather, synthetic dyes and fragrances.

[0003] Trimethyladipic acid is typically prepared using 3,3,5-trimethylcyclohexanol or 3,3,5-trimethylcyclohexanone as raw materials through methods such as electrochemical oxidation and nitric acid oxidation. However, due to the presence of two similarly active reaction sites on either side of the hydroxyl group in 3,3,5-trimethylcyclohexanol or the carbonyl group in 3,3,5-trimethylcyclohexanone, the trimethyladipic acid obtained using traditional preparation methods is a mixture of two isomers, 2,2,4-trimethyladipic acid and 2,4,4-trimethyladipic acid, in a mass ratio of 1:1. To more clearly illustrate the above issue, taking 3,3,5-trimethylcyclohexanol as an example, the oxidation reaction in the presence of nitric acid and catalysts such as copper and vanadium to produce two isomers, 2,2,4-trimethyladipic acid and 2,4,4-trimethyladipic acid, in equal proportions, is shown below, where a and b are active reaction sites:

[0004]

[0005] Since the two isomers have little difference in properties such as solubility, it is often difficult to separate and purify them in the post-processing stage, resulting in problems such as cumbersome separation process, long preparation time, and large product loss.

[0006] As patent CN104831310A reports the method for electrochemical preparation of trimethyl adipic acid, the method synthesizes 2,2,4-trimethyl adipic acid and 2,4,4-trimethyl adipic acid mixture with 3,3,5-trimethyl cyclohexanol as raw material, and the method post-processing and its cumbersome, difficult to industrialization. Patent GB915510A reports a kind of synthetic method of nitric acid preparing trimethyl adipic acid, in the case of having or without oxidizing catalyst, obtains trimethyl adipic acid mixture, the method separates trimethyl adipic acid from reaction solution by the mode of decrease temperature crystallization, but isolated trimethyl adipic acid still exists as mixture form, and filtering difficulty. Also have patent (GB954256A) report that the above-mentioned isolated trimethyl adipic acid mixture adopts the mode of nitric acid recrystallization to separate two isomers, but the method is time-consuming longer, and owing to being the crystallization of mixture, product loss is more. Summary of the Invention

[0007] Based on this, it is necessary to provide a metal complex catalyst and a preparation method of 2,4,4-trimethyladipic acid for the above problems; the metal complex catalyst can be used for the selective preparation of 2,4,4-trimethyladipic acid, and high-purity and high-yield 2,4,4-trimethyladipic acid can be obtained through simple crystallization post-treatment.

[0008] A metal complex catalyst for the preparation of 2,4,4-trimethyladipic acid, the metal complex catalyst comprising a transition metal salt and a ligand, wherein the ligand is selected from at least one of the following formulas (1), (2), and (3),

[0009]

[0010] wherein R1 is selected from halogen element, hydrogen, methyl, ethyl or methoxy, R2 is selected from halogen element, hydrogen, methyl, ethyl, tert-butyl or methoxy, and R3 and R4 are each independently selected from hydrogen or methyl.

[0011] In one embodiment, the molar ratio of the transition metal salt to the ligand is 1:1 - 1:2.

[0012] In one embodiment, the transition metal salt is selected from at least one of copper nitrate, ammonium metavanadate, and iron nitrate.

[0013] In one embodiment, when R1 is selected from halogen element, R2 is selected from halogen element, hydrogen, methyl, ethyl, tert-butyl or methoxy;

[0014] or, when R2 is selected from halogen element, R1 is selected from hydrogen, methyl or ethyl.

[0015] In one embodiment, formula (1) is selected from formula (1-1) shown below,

[0016]

[0017] In one embodiment, formula (2) is selected from formula (2-1) shown below,

[0018]

[0019] A preparation method of 2,4,4-trimethyladipic acid, comprising the following steps: reacting a compound under the conditions of the above-mentioned metal complex catalyst and an oxidant, and obtaining 2,4,4-trimethyladipic acid by crystallization after the reaction, wherein the compound is selected from 3,3,5-trimethylcyclohexanol and / or 3,3,5-trimethylcyclohexanone.

[0020] In one embodiment, the molar ratio of the transition metal salt in the metal complex catalyst to the compound is 1:1 - 1:2.

[0021] In one embodiment, the molar ratio of the oxidant to the compound is 3:1 - 5:1.

[0022] In one embodiment, the oxidant is selected from nitric acid.

[0023] In one embodiment, the reaction temperature is 80°C - 130°C.

[0024] In one embodiment, the compound is added in batches for the reaction.

[0025] In the present invention, a metal complex catalyst formed by a large steric hindrance ligand with a specific structure and a transition metal salt is used for the preparation of 2,4,4 - trimethyladipic acid. Since the active site a on the side of the hydroxyl group in 3,3,5 - trimethylcyclohexanol or the carbonyl group in 3,3,5 - trimethylcyclohexanone close to the 3,3 - dimethyl group has a large steric hindrance, under the selective catalytic action of the large steric hindrance metal complex catalyst, the reaction will preferentially occur at the active site b on the side of the hydroxyl group in 3,3,5 - trimethylcyclohexanol or the carbonyl group in 3,3,5 - trimethylcyclohexanone close to the 5 - methyl group for oxidative ring - opening reaction, thereby promoting the formation of 2,4,4 - trimethyladipic acid and inhibiting the production of 2,2,4 - trimethyladipic acid, such that the mass ratio of 2,4,4 - trimethyladipic acid to 2,2,4 - trimethyladipic acid in the product is up to about 9:1. Further, due to the low content of 2,2,4 - trimethyladipic acid, post - treatment by crystallization not only makes the crystallization step easier to operate, but also is beneficial to obtaining high - purity 2,4,4 - trimethyladipic acid.

[0026] Therefore, the metal complex catalyst of the present invention can be used for the selective preparation of 2,4,4 - trimethyladipic acid, and high - purity and high - yield 2,4,4 - trimethyladipic acid can be obtained through simple post - treatment by crystallization, greatly improving the industrialization efficiency of 2,4,4 - trimethyladipic acid. Description of the Drawings

[0027] Figure 1 It is the gas chromatogram of the reaction solution before crystallization of the product prepared in Example 1. Detailed Description of the Embodiments

[0028] To facilitate the understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure content of the present invention more thorough and comprehensive.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this invention belongs. The terms used in the description of the present invention herein are for the purpose of describing specific embodiments or examples only, and are not intended to limit the present invention.

[0030] The present invention provides a metal complex catalyst for preparing 2,4,4-trimethyladipic acid. The metal complex catalyst comprises a transition metal salt and a ligand. Among them, the ligand is selected from at least one of the following formulas (1), (2), and (3),

[0031]

[0032] wherein, R1 is selected from halogen element, hydrogen, methyl, ethyl or methoxy, R2 is selected from halogen element, hydrogen, methyl, ethyl, tert-butyl or methoxy, and R3 and R4 are each independently selected from hydrogen or methyl.

[0033] The present invention uses a metal complex catalyst formed by a large steric hindrance ligand with a specific structure and a transition metal salt for preparing 2,4,4-trimethyladipic acid. Since the active site a on the side of the hydroxyl group in 3,3,5-trimethylcyclohexanol or the carbonyl group in 3,3,5-trimethylcyclohexanone close to the 3,3-dimethyl group has a large steric hindrance, under the selective catalysis of the large steric hindrance metal complex catalyst, the reaction will preferentially occur at the active site b on the side of the hydroxyl group in 3,3,5-trimethylcyclohexanol or the carbonyl group in 3,3,5-trimethylcyclohexanone close to the 5-methyl group for oxidative ring-opening reaction, thereby promoting the formation of 2,4,4-trimethyladipic acid and inhibiting the production of 2,2,4-trimethyladipic acid, so that the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the product is as high as about 9:1. This not only facilitates the subsequent separation of 2,4,4-trimethyladipic acid, but also greatly improves the purity and yield of the 2,4,4-trimethyladipic acid product.

[0034] Preferably, the molar ratio of the transition metal salt to the ligand is 1:1 - 1:2, and more preferably 1:1 - 1:1.5, which is more conducive to regulating the catalytic performance of the coordination compound catalyst and improving the reaction selectivity.

[0035] Specifically, the transition metal salt includes but is not limited to at least one of copper nitrate, ammonium metavanadate, and iron nitrate, and is preferably at least one of copper nitrate, ammonium metavanadate, and iron nitrate.

[0036] In one embodiment, when R1 is selected from halogen element, R2 is selected from halogen element, hydrogen, methyl, ethyl, tert-butyl or methoxy;

[0037] Alternatively, when R2 is selected from halogen elements, R1 is selected from hydrogen, methyl or ethyl.

[0038] Among them, the halogen elements include but are not limited to Cl, Br, I, and more preferably Br.

[0039] Further preferably, R1 is selected from Br, and R2 is selected from tert-butyl, that is, the specific structure of formula (1) is preferably formula (1-1) shown as follows:

[0040]

[0041] In one embodiment, the specific structure of formula (2) is preferably formula (2-1) shown as follows,

[0042]

[0043] More preferably, the ligand is selected from at least one of formula (1-1), formula (2-1), and formula (3) shown as follows,

[0044]

[0045] It should be noted that the present invention does not limit the preparation method of the ligand, and those skilled in the art can obtain the structures shown in formula (1), formula (2), and formula (3) according to the existing preparation methods.

[0046] In one embodiment, the ligand shown in formula (1) is obtained by reacting 2-amino-2'-hydroxy-1,1'-binaphthalene with a salicylaldehyde compound, wherein the salicylaldehyde compound includes but is not limited to 3-bromosalicylaldehyde, 3-chlorosalicylaldehyde, 3-iodosalicylaldehyde, 3,5-dibromosalicylaldehyde, 3,5-dichlorosalicylaldehyde, 3,5-diiodosalicylaldehyde, 3-bromo-5-chlorosalicylaldehyde, 3-bromo-5-methylsalicylaldehyde, 3-bromo-5-ethylsalicylaldehyde, 3-bromo-5-methoxysalicylaldehyde, 3-bromo-5-tert-butylsalicylaldehyde, 3-chloro-5-tert-butylsalicylaldehyde, 3-iodo-5-tert-butylsalicylaldehyde, 5-bromosalicylaldehyde, 5-chlorosalicylaldehyde, 5-iodosalicylaldehyde, 3-methyl-5-bromosalicylaldehyde, 3-methyl-5-chlorosalicylaldehyde, 3-methoxysalicylaldehyde, 3-methoxy-5-bromosalicylaldehyde, 3-ethyl-5-bromosalicylaldehyde, and at least one of them is preferably 3-bromo-5-tert-butylsalicylaldehyde.

[0047] In one embodiment, the ligand shown in formula (2) is obtained by reacting a phosphonyl aniline compound with N-acetylanthranilic acid under the action of a benzenesulfonyl chloride coupling agent, wherein the phosphonyl aniline compound includes at least one of 2-diphenylphosphonyl aniline, 2-(diphenylphosphonyl)-4-methylaniline, 2-(diphenylphosphonyl)-6-methylaniline, 2-(diphenylphosphonyl)-4,6-dimethylaniline, and is preferably 2-diphenylphosphonyl aniline.

[0048] In one embodiment, the ligand shown in formula (3) is obtained by reacting 1,2,3,4-tetrahydroisoquinoline with 1,2-naphthol under the action of a benzaldehyde activator.

[0049] In one embodiment, the metal complex catalyst can be obtained by mixing and reacting the transition metal salt and the ligand.

[0050] The present invention also provides a method for preparing 2,4,4-trimethyladipic acid, which includes the following steps: under the conditions of the metal complex catalyst and an oxidant as described above, reacting a compound, and after the reaction is completed, 2,4,4-trimethyladipic acid is obtained by crystallization. The compound is selected from 3,3,5-trimethylcyclohexanol and / or 3,3,5-trimethylcyclohexanone.

[0051] Preferably, the molar ratio of the transition metal salt in the metal complex catalyst to the compound is 1:1 - 1:2, which is more conducive to selectively regulating the ratio of 2,2,4-trimethyladipic acid to 2,4,4-trimethyladipic acid, so that the mass ratio of the 2,4,4-trimethyladipic acid product to the 2,2,4-trimethyladipic acid product is higher than 9:1. This not only facilitates the subsequent separation of 2,4,4-trimethyladipic acid, but also greatly improves the purity and yield of the 2,4,4-trimethyladipic acid product.

[0052] Preferably, the molar ratio of the oxidant to the compound is 3:1 - 5:1. By reasonably regulating the amount of the oxidant, not only can the carbon-carbon bond be oxidized to break the carbon-carbon bond and open the ring to form a carboxyl group, making the reaction more complete, but also the increase of by-products can be avoided.

[0053] Specifically, the oxidant includes but is not limited to nitric acid, preferably nitric acid, and further preferably the concentration of nitric acid is 50% - 65%.

[0054] In one embodiment, the reaction temperature is preferably 80°C - 130°C.

[0055] In one embodiment, it is preferred to add 3,3,5-trimethylcyclohexanol or 3,3,5-trimethylcyclohexanone in batches for the reaction, and more preferably by dropwise addition.

[0056] Furthermore, since the content of 2,2,4-trimethyladipic acid is small, after the reaction is completed, crystallization is used for post-treatment, which not only makes the crystallization step easier to operate, but also is conducive to obtaining high-purity 2,4,4-trimethyladipic acid.

[0057] Therefore, the metal complex catalyst of the present invention can be used for the selective preparation of 2,4,4-trimethyladipic acid, and high-purity and high-yield 2,4,4-trimethyladipic acid can be obtained through simple crystallization post-treatment, greatly improving the industrialization efficiency of 2,4,4-trimethyladipic acid.

[0058] Hereinafter, the metal complex catalyst and the preparation method of 2,4,4-trimethyladipic acid will be further described through the following specific examples.

[0059] Example 1

[0060] Provide the ligand shown in formula (1-1) (0.162 g, 0.31 mmol), add it together with copper nitrate (0.052 g, 0.28 mmol) to a reaction flask, then add nitric acid (7.4 mL, 108 mmol, concentration 65%) and stir to dissolve. After heating to 90 °C, slowly dropwise add 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol). After the reaction is complete, take a sample for detection. The specific detection process is as follows: Take 1 g of the reaction solution, dissolve it in 50 g of acetone, then add 10 g of diazomethane solution, stir at room temperature for 30 min to obtain a derivatized reaction solution. Then, quantitatively determine the composition of the derivatized reaction solution by gas chromatography. The obtained gas chromatogram is as Figure 1 shown. By integral calculation, the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample is about 97.4:2.6. Then slowly cool down to 0 °C, a large amount of solid products precipitate. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid is obtained with a yield of 87.03% and a purity of 97.75%.

[0061]

[0062] Example 2

[0063] Provide the ligand shown in formula (2-1) (0.149 g, 0.31 mmol), add it together with copper nitrate (0.052 g, 0.28 mmol) to a reaction flask, then add nitric acid (7.4 mL, 108 mmol, concentration 65%) and stir to dissolve. After heating to 90 °C, slowly dropwise add 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol). After the reaction is complete, take a sample for detection. The mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample is about 97.3:2.7. Then slowly cool down to 0 °C, a large amount of solid products precipitate. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid is obtained with a yield of 85.28% and a purity of 96.87%.

[0064]

[0065] Example 3

[0066] Provide the ligand shown in formula (3) (0.141 g, 0.31 mmol), add it together with copper nitrate (0.052 g, 0.28 mmol) into a reaction flask, then add nitric acid (7.4 mL, 108 mmol, concentration 65%) and stir to dissolve. After heating to 90 °C, slowly dropwise add 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol). After the reaction is complete, take a sample for detection. The mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample is about 96:4. Then slowly cool down to 0 °C, a large amount of solid product precipitates. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid is obtained with a yield of 80.88% and a purity of 95.05%.

[0067]

[0068] Example 4

[0069] Add the ligand shown in formula (1-1) (0.162 g, 0.31 mmol) together with copper nitrate (0.052 g, 0.28 mmol) into a reaction flask, then add nitric acid (7.4 mL, 108 mmol, concentration 65%) and stir to dissolve. After heating to 80 °C, slowly dropwise add 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol). After the reaction is complete, take a sample for detection. The mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample is about 87:13. Then slowly cool down to 0 °C, a large amount of solid product precipitates. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid is obtained with a yield of 83.20% and a purity of 93.91%.

[0070] Example 5

[0071] Add the ligand shown in formula (1-1) (0.162 g, 0.31 mmol) together with copper nitrate (0.052 g, 0.28 mmol) into a reaction flask, then add nitric acid (7.4 mL, 108 mmol, concentration 65%) and stir to dissolve. After heating to 110 °C, slowly dropwise add 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol). After the reaction is complete, take a sample for detection. The mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample is about 95:5. Then slowly cool down to 0 °C, a large amount of solid product precipitates. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid is obtained with a yield of 88.50% and a purity of 98.34%.

[0072] Example 6

[0073] The ligand shown in formula (1-1) (0.162 g, 0.31 mmol) and copper nitrate (0.052 g, 0.28 mmol) were added into a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred until dissolved. After heating to 130 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 91:9. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 85.12% and a purity of 92.17%.

[0074] Example 7

[0075] The ligand shown in formula (1-1) (0.162 g, 0.31 mmol) and ammonium metavanadate (0.033 g, 0.28 mmol) were added into a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred until dissolved. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 89:11. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 83.70% and a purity of 96.31%.

[0076] Example 8

[0077] The ligand shown in formula (1-1) (0.162 g, 0.31 mmol) and iron nitrate (0.068 g, 0.28 mmol) were added into a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred until dissolved. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 90:10. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 74.33% and a purity of 95.32%.

[0078] Example 9

[0079] The ligand shown in formula (1-1) (0.147 g, 0.28 mmol) and copper nitrate (0.026 g, 0.14 mmol) were added into a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred until dissolved. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 96.5:3.5. Then the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 78.30% and a purity of 96.70%.

[0080] Example 10

[0081] The ligand shown in formula (1-1) (0.219 g, 0.42 mmol) and copper nitrate (0.078 g, 0.42 mmol) were added into a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred until dissolved. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 95.3:4.7. Then the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 89.01% and a purity of 98.11%.

[0082] Example 11

[0083] The ligand shown in formula (1-1) (0.162 g, 0.31 mmol) and copper nitrate (0.052 g, 0.28 mmol) were added into a reaction flask, and then nitric acid (9.9 mL, 144 mmol, concentration 65%) was added and stirred until dissolved. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 97:3. Then the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 87.24% and a purity of 96.20%.

[0084] Example 12

[0085] A ligand shown in formula (1-1) (0.162 g, 0.31 mmol) was added to a reaction flask together with copper nitrate (0.052 g, 0.28 mmol), and then nitric acid (12.34 mL, 180 mmol, concentration 65%) was added and stirred to dissolve. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 97.1:2.9. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 86.20% and a purity of 94.10%.

[0086] Example 13

[0087] A ligand shown in formula (1-2) (0.149 g, 0.31 mmol) was added to a reaction flask together with copper nitrate (0.052 g, 0.28 mmol), and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred to dissolve. After heating to 90 °C, 3,3,5-trimethylcyclohexanone (5.1 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 96.8:3.2. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 85.7% and a purity of 93.73%.

[0088]

[0089] Example 14

[0090] A ligand shown in formula (1-3) (0.141 g, 0.31 mmol) was added to a reaction flask together with copper nitrate (0.052 g, 0.28 mmol), and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred to dissolve. After heating to 90 °C, 3,3,5-trimethylcyclohexanone (5.1 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 96.1:3.9. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 85.3% and a purity of 92.8%.

[0091]

[0092] Example 15

[0093] A ligand shown in formula (2-2) (0.139 g, 0.31 mmol) was provided and added to a reaction flask together with copper nitrate (0.052 g, 0.28 mmol). Then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred until dissolved. After heating to 90 °C, 3,3,5-trimethylcyclohexanone (5.1 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 96.2:3.8. Then the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 84.8% and a purity of 91.8%.

[0094]

[0095] Comparative Example 1

[0096] Copper nitrate (0.052 g, 0.28 mmol) was added to a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred until dissolved. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 1:1. Then the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 45.3% and a purity of 50.2%.

[0097] Comparative Example 2

[0098] The ligand shown in formula (1-1) (0.13 g, 0.3 mmol) was added to a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred until dissolved. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was about 1:1. Then the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 38.7% and a purity of 46.3%.

[0099] Comparative Example 3

[0100] The ligand shown in formula (2-1) (0.18 g, 0.34 mmol) was added to a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred to dissolve. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was measured to be approximately 1:1. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 35.6% and a purity of 45.8%.

[0101] Comparative Example 4

[0102] The ligand shown in formula (3) (0.18 g, 0.42 mmol) was added to a reaction flask, and then nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred to dissolve. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was measured to be approximately 1:1. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 40.7% and a purity of 42.6%.

[0103] Comparative Example 5

[0104] The ligand shown in formula (4) (0.06 g, 0.30 mmol) was provided and added together with copper nitrate (0.052 g, 0.28 mmol) to a reaction flask. Then, nitric acid (7.4 mL, 108 mmol, concentration 65%) was added and stirred to dissolve. After heating to 90 °C, 3,3,5-trimethylcyclohexanol (5.2 g, 36 mmol) was slowly added dropwise. After the reaction was completed, a sample was taken for detection, and the mass ratio of 2,4,4-trimethyladipic acid to 2,2,4-trimethyladipic acid in the sample was measured to be approximately 6:4. Then, the temperature was slowly lowered to 0 °C, and a large amount of solid product was precipitated. After filtration, washing with water, and drying, 2,4,4-trimethyladipic acid was obtained with a yield of 56.3% and a purity of 60.5%.

[0105]

[0106] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered to be within the scope described in this specification.

[0107] The above-described embodiments merely represent several implementation manners of the present invention. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all fall within the protection scope of the present invention. Therefore, the protection scope of the present invention patent shall be subject to the appended claims.

Claims

1. A metal complex catalyst for the preparation of 2,4,4-trimethyladipic acid, characterized in that, The metal complex catalyst comprises a transition metal salt and a ligand, wherein the transition metal salt is selected from at least one of copper nitrate, ammonium metavanadate, and iron nitrate, and the ligand is selected from at least one of the following formulas (1), (2), and (3). 、 、 ， Wherein, R1 is selected from a halogen element, hydrogen, methyl, ethyl, or methoxy, R2 is selected from a halogen element, hydrogen, methyl, ethyl, tert-butyl, or methoxy, and R3 and R4 are each independently selected from hydrogen or methyl.

2. The metal complex catalyst according to claim 1, characterized in that, The molar ratio of the transition metal salt to the ligand is 1:1 - 1:

2.

3. The metal complex catalyst according to claim 1 or 2, characterized in that, When R1 is selected from a halogen element, R2 is selected from a halogen element, hydrogen, methyl, ethyl, tert-butyl, or methoxy. Or, when R2 is selected from a halogen element, R1 is selected from hydrogen, methyl, or ethyl.

4. The metal complex catalyst according to claim 3, wherein Formula (1) is selected from the following formula (1-1). 。 5. The metal complex catalyst according to claim 1, wherein Formula (2) is selected from the following formula (2-1). 。 6. A method for preparing 2,4,4-trimethyladipic acid, characterized in that, Comprising the following steps: Under the conditions of the metal complex catalyst as described in any one of claims 1-5 and an oxidizing agent, reacting the compound, and after the reaction is completed, obtaining 2,4,4-trimethyladipic acid by crystallization, wherein the compound is selected from 3,3,5-trimethylcyclohexanol and / or 3,3,5-trimethylcyclohexanone.

7. The method for preparing 2,4,4-trimethyladipic acid according to claim 6, wherein The molar ratio of the transition metal salt in the metal complex catalyst to the compound is 1:1 - 1:

2.

8. The method for preparing 2,4,4-trimethyladipic acid according to claim 6, wherein The molar ratio of the oxidizing agent to the compound is 3:1 - 5:

1.

9. The method for preparing 2,4,4-trimethyladipic acid according to claim 6, characterized in that, The oxidizing agent is selected from nitric acid.

10. The preparation method of 2,4,4-trimethyladipic acid according to claim 6, characterized in that, The reaction temperature is 80°C - 130°C.

11. The method for preparing 2,4,4-trimethyladipic acid according to claim 6, wherein The compound is added in batches for the reaction.

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