A method for preparing N-substituted lactamide by ion liquid catalyzed aminolysis of polylactic acid

Abstract

The application discloses a method for preparing N-substituted lactamide by catalyzing aminolysis of polylactic acid by using an ionic liquid. The method comprises the following steps: using the ionic liquid as a solvent and / or a catalyst, and allowing polylactic acid to perform aminolysis reaction with an organic amine compound to generate the N-substituted lactamide. The method does not need other transition metal catalysts, has mild reaction conditions, and has no by-products, and thus has a strong industrial application prospect.

Description

Technical Field

[0001] This invention belongs to the field of waste plastic recycling technology, specifically relating to a novel method for preparing N-substituted lactamides by catalytic aminolysis of polylactic acid (PLA) using ionic liquids. Background Technology

[0002] Polylactic acid (PLA) is widely used in daily life and production, but its large-scale accumulation puts enormous pressure on the environment and human survival. Therefore, the degradation of PLA is particularly important in the context of carbon dioxide. Currently, the depolymerization methods of PLA mainly include hydrolysis, alcoholysis, and ammonolysis, and the types of chemicals prepared from its chemical transformation are still relatively limited. N-substituted lactamides are an important class of chemical raw materials, widely used in medicine, biology, and other fields. Current synthesis methods for these compounds mainly include: high-temperature copper or iron-catalyzed reaction of lactamide with aromatic amines (aromatic iodides), reduction of N-substituted-2-oxopropionamide by zinc / polymethylhydrosiloxane, alkaline-catalyzed reaction of lactic acid esters with aromatic amines, alkaline-catalyzed hydroxylation of 2-halo-N-aryl lactamides, and reaction of lactic acid with aromatic amines. These methods generally suffer from problems such as complex reactions, low reaction efficiency, metal catalyst residue, and difficult separation. To meet the needs of green and sustainable development, developing new high-performance, green methods for preparing N-substituted lactamides is of great significance.

[0003] Ionic liquids are compounds composed of organic cations and inorganic / organic anions. Through the functional design of cations and anions, ionic liquids can be endowed with different functions and have been applied in many fields. In particular, the hydrogen bonding and electrostatic interactions in ionic liquid systems can enable catalytic chemical reactions under metal-free conditions, exhibiting unique properties and providing development opportunities for novel catalytic systems and new chemical reaction methods. However, research and techniques for the preparation of N-substituted lactamides by catalytic amination of polylactic acid using ionic liquids under metal-free conditions have not been reported. Summary of the Invention

[0004] The purpose of this invention is to provide a novel method for preparing N-substituted lactamides by catalytic aminolysis of polylactic acid using ionic liquids under mild conditions.

[0005] The novel method for preparing N-substituted lactamides provided by this invention includes the following steps:

[0006] Using an ionic liquid as a solvent and / or catalyst, polylactic acid is subjected to an aminolysis reaction with an organic amine compound to generate the N-substituted lactamide.

[0007] In the above method, the organic amine compounds include aromatic amines such as aniline, p-toluidine, m-toluidine, and p-methoxyaniline; aliphatic amines such as benzylamine, butylamine, propylamine, and dipropylamine; and aromatic hydrazine compounds such as phenylhydrazine, p-methylphenylhydrazine, m-methylphenylhydrazine, and p-methoxyphenylhydrazine.

[0008] The following are some of the names and chemical structural formulas of organic amines.

[0009] Aromatic amines:

[0010] Fatty amines:

[0011] Aromatic hydrazine:

[0012] In the above method, the N-substituted lactamides are mainly N-aryl lactamides, N-aliphatic lactamides, and N-aryl lactylhydrazides. The names and chemical structural formulas of some compounds are shown below.

[0013] N-Aromatic Lactamide:

[0014] N-Aliphatic lactamide:

[0015] N-Aromatic Lactohydrazide:

[0016] In the above method, the ionic liquid is mainly an ionic liquid that can catalyze the hydrolysis of polylactic acid amine. The names and chemical structural formulas of some ionic liquids are shown below.

[0017]

[0018] In the above method, the molar ratio of the ionic liquid to polylactic acid (monomer unit) is selected as 1:100 to 10:1, preferably 1:10 to 8:1, specifically such as 1:0.5, 1:1, 1:2, 1:5, 1:10, 5:1, 10:1.

[0019] In the above method, the molar ratio of the organic amine compound to polylactic acid (monomer unit) is selected as 20:1 to 1:1, preferably 1.2:1 to 10:1, specifically 1.2:1, 2:1, 5:1, 8:1, 10:1.

[0020] In the above method, the reaction temperature is preferably 80-180℃, specifically 120℃.

[0021] In the above method, the reaction time is 5 to 20 hours, specifically 12 hours.

[0022] In the above method, the reaction can be carried out in a pressure-resistant reactor, such as a pressure-resistant reaction tube.

[0023] The method further includes the step of separating N-substituted lactamides from the reaction system by column chromatography after the reaction is completed.

[0024] The specific method is as follows: After the reaction is completed, add saturated sodium chloride solution to the reaction system and let it stand for 5 minutes; extract with ethyl acetate 3 times, combine the organic phases, dry with anhydrous sodium sulfate, concentrate, and purify by silica gel column chromatography to obtain the product.

[0025] The method for preparing N-substituted lactamides by ionic liquid catalysis of polylactic acid provided by this invention has the advantages of high efficiency, simplicity, mild reaction conditions, and no metal involvement, and has strong prospects for industrial application. Detailed Implementation

[0026] The method of the present invention will be described below with reference to specific embodiments. However, the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

[0027] Unless otherwise specified, the experimental methods described in the following examples are conventional methods; the reagents and materials described are commercially available unless otherwise specified.

[0028] The ionic liquids involved in the following examples can be prepared according to the following methods:

[0029] Preparation of 1-ethyl-3-methylimidazolium lactate: NaOH (wt, 20%) aqueous solution was added dropwise to AgNO3 aqueous solution (wt, 20%) to obtain AgOH precipitate; the reaction was carried out for 1 h, filtered, washed with deionized water, and filtered again under vacuum, repeating this process three times. Then, lactic acid aqueous solution (wt, 40%) was added dropwise to the AgOH precipitate until the precipitate disappeared, yielding silver lactate aqueous solution. A portion of 1-ethyl-3-methylimidazolium chloride was added to the silver lactate aqueous solution, producing a white precipitate. After reacting for 2 h, the solution was filtered. 1-ethyl-3-methylimidazolium chloride was continued to be added dropwise to the filtrate until no more precipitate formed, and then filtered again. Most of the water was evaporated using a rotary evaporator, and then the solution was vacuum dried at 65 °C for 72 h to obtain the target product. NMR data of 1-ethyl-3-methylimidazolium lactate: 1 H NMR (400MHz, DMSO-d6, 25℃): δ=8.92(s,1H),7.92-7.94(m,1H),7.75-7.78(m,1H),5.48(s,1H) ),4.80(q,J=4.8Hz,2H),4.54-4.58(m,1H),1.57(t,J=4.8Hz,3H),1.26ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=176.9, 137.0, 123.0, 122.8, 77.8, 55.0, 37.1, 19.4ppm.

[0030] The preparation processes for 1-propyl-3-methylimidazolium lactate and 1-butyl-3-methylimidazolium lactate are similar to those for 1-ethyl-3-methylimidazolium lactate. NMR data for 1-propyl-3-methylimidazolium lactate: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 8.90 (s, 1H), 7.90-7.93 (m, 1H), 7.76-7.78 (m, 1H), 5.45 (s, 1H), 5.0 1(t,J=4.8Hz,2H),4.54-4.58(m,1H),2.07(m,2H),1.26(t,J=8.8Hz,3H),0.94ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=176.6, 137.0, 123.1, 122.6, 77.9, 55.1, 37.2, 25.3, 19.4ppm. 1-Butyl-3-methylimidazolium lactate NMR data: 1 H NMR (400MHz, DMSO-d6, 25℃): δ=8.92(s,1H),7.90-7.92(m,1H),7.76-7.77(m,1H),5.48(s,1H),5.01(t,J= 4.8Hz,2H),4.54-4.56(m,1H),2.01(m,2H),1.30(m,2H),1.25(t,J=8.8Hz,3H),0.89ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25°C): δ = 176.8, 137.0, 123.1, 122.8, 77.9, 54.2, 32.3, 20.7, 19.4, 13.8ppm.

[0031] Preparation of tetrabutylphosphine lactate: 10 mmol of lactic acid aqueous solution (wt. 30%) was added to a round-bottom flask containing 10 mmol of tetrabutylphosphine bromide aqueous solution (wt. 40%). The mixture was transferred to an oil bath at 30°C and heated with stirring for 24 hours. After the reaction was complete, most of the water was evaporated using a rotary evaporator, and then the product was dried under vacuum at 65°C for 72 hours to obtain the target product. NMR data for tetrabutylphosphine lactate: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 5.40 (s, 1H), 4.54-4.59 (m, 1H), 2.44-2.46 (m, 8 H),1.30(m,8H),1.29(m,8H),1.26(d,J=8.8Hz,3H),0.89ppm(t,J=4.8Hz,12H); 13C NMR (101MHz, DMSO-d6, 25°C): δ = 176.9, 77.8, 25.8, 25.6, 19.4, 18.9, 13.8ppm.

[0032] The preparation processes of tetramethylammonium lactate, tetraethylammonium lactate, and tetrabutylammonium lactate are similar to those for the synthesis of tetrabutylphosphine lactate. NMR data for tetramethylammonium lactate: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 5.45 (s, 1H), 4.54-4.58 (m, 1H), 3.30 (s, 12H), 1.26ppm (d, J = 8.8Hz, 3H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=176.8, 77.8, 57.0, 19.4ppm. Tetraethyllactic acid NMR data: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 5.45 (s, 1H), 4.54-4.58 (m, 1H), 3.22 (t, J = 3.6Hz, 8H), 1.77 (m, 8H), 1.26 (d, J = J = 8.8Hz, 3H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=176.8, 77.8, 55.0, 19.4, 8.3ppm. Tetrabutylammonium NMR data: 1 H NMR (400MHz, DMSO-d6, 25℃): δ=5.40(s,1H),4.54-4.59(m,1H),3.22(t,J=4.8Hz,8H ),1.70-2.74(m,8H),1.30(m,8H),1.26(d,J=8.8Hz,3H),0.89ppm(t,J=4.8Hz,12H); 13 C NMR (101MHz, DMSO-d6, 25°C): δ = 176.9, 77.8, 57.8, 23.5, 19.4, 19.0, 13.8ppm.

[0033] Example 1: Preparation of N-phenyllacticamide from the reaction of polylactic acid and aniline catalyzed by 1-ethyl-3-methylimidazolium acetate. 72 mg of polylactic acid (monomer: 1 mmol), 0.5 mmol of ionic liquid 1-ethyl-3-methylimidazolium acetate ([EtMIm][OAc]), and 10 mmol of aniline were placed in a 20 mL pressure-resistant glass reaction tube and sealed. The tube was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours. After the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, and the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 82%, and the product was N-phenyllactic acid, with a separation yield of 79%.

[0034] reaction products used 1 H and 13 Its structure was determined by C NMR spectroscopy:

[0035] 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 9.60 (s, 1H), 7.69-7.71 (m, 2H), 7.27-7.32 (m, 2H), 7. 02-7.07(m,1H),5.71(d,J=7.2Hz,1H),4.10-4.18(m,1H),1.30ppm(d,J=8.8Hz,3H);

[0036] 13 C NMR (101MHz, DMSO-d6, 25℃): δ=173.4,138.6,128.5,123.3,119.5,67.7,20.8ppm.

[0037] As can be seen from the above, the product has the correct structure and is N-phenyllactic acid amide.

[0038] Example 2: Preparation of N-phenyllacticamide from the reaction of polylactic acid and aniline catalyzed by 1-propyl-3-methylimidazolium acetate. 72 mg of polylactic acid (monomer: 1 mmol), 0.5 mmol of ionic liquid 1-propyl-3-methylimidazolium acetate ([PrMIm][OAc]), and 10 mmol of aniline were placed in a 20 mL pressure-resistant glass reaction tube and sealed. The tube was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours. After the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, and the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 84%, and the product was N-phenyllactic acid, with a separation yield of 82%.

[0039] Example 3: Preparation of N-phenyllacticamide from the reaction of polylactic acid and aniline catalyzed by 1-ethyl-3-methylimidazolium lactate. 72 mg of polylactic acid (monomer: 1 mmol), 5 mmol of ionic liquid 1-ethyl-3-methylimidazolium lactate ([EtMIm][Lac]), and 1.2 mmol of aniline were placed in a 20 mL glass pressure-resistant reaction tube and sealed. The tube was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours. After the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, and the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 90%, and the product was N-phenyllactic acid, with a separation yield of 88%.

[0040] Example 4: Preparation of N-phenyllacticamide from the reaction of polylactic acid and aniline catalyzed by 1-propyl-3-methylimidazolium lactate. 72 mg of polylactic acid (monomer: 1 mmol), 5 mmol of ionic liquid 1-propyl-3-methylimidazolium lactate ([PrMIm][Lac]), and 1.2 mmol of aniline were placed in a 20 mL glass pressure-resistant reaction tube and sealed. The tube was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours. After the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, and the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 92%, and the product was N-phenyllactic acid, with a separation yield of 90%.

[0041] Example 5: Preparation of N-phenyllacticamide from the reaction of polylactic acid and aniline catalyzed by 1-butyl-3-methylimidazolium lactate. 72 mg of polylactic acid (monomer: 1 mmol), 0.2 mmol of ionic liquid 1-butyl-3-methylimidazolium lactate ([BuMIm][Lac]), and 10 mmol of aniline were placed in a 20 mL pressure-resistant glass reaction tube and sealed. The tube was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours. After the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, and the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 93%, and the product was N-phenyllactic acid, with a separation yield of 90%.

[0042] Example 6: Preparation of N-phenyllacticamide by the reaction of tetrabutylphosphine lactate-catalyzed polylactic acid with aniline.

[0043] 72 mg of polylactic acid (monomer: 1 mmol) and 1 mmol of tetrabutylphosphine ionic liquid ([P) were added. 4444 [Lac]), 10 mmol of aniline was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 92%, and the product was N-phenyllactic acid, with a separation yield of 91%.

[0044] Example 7: Preparation of N-phenyllacticamide by the reaction of polylactic acid and aniline catalyzed by ammonium tetramethyllacticate.

[0045] 72 mg of polylactic acid (monomer: 1 mmol) and 2 mmol of tetramethylammonium lactate ionic liquid were added. 1111 [Lac]), 10 mmol of aniline was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 ¹³C NMR analysis determined its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 88%, and the product was N-phenyllactic acid, with a separation yield of 86%.

[0046] Example 8: Preparation of N-phenyllacticamide by the reaction of polylactic acid and aniline catalyzed by tetraethylammonium lactate.

[0047] 72 mg of polylactic acid (monomer: 1 mmol) and 1.5 mmol of tetraethylammonium lactate ionic liquid ([N) were added. 2222[Lac]), 8 mmol of aniline was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to a 120 °C oil bath and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 92%, and the product was N-phenyllactic acid, with a separation yield of 90%.

[0048] Example 9: Preparation of N-phenyllacticamide by the reaction of polylactic acid and aniline catalyzed by tetrabutylammonium lactate.

[0049] 72 mg of polylactic acid (monomer: 1 mmol) and 0.2 mmol of ionic liquid tetrabutylammonium lactate ([N 4444 [Lac]), 5 mmol of aniline was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 98%, and the product was N-phenyllactic acid, with a separation yield of 96%.

[0050] Example 10: Preparation of N-p-tolyl lactamide by reacting polylactic acid with p-toluidine catalyzed by tetrabutylammonium lactate.

[0051] 72 mg of polylactic acid (monomer: 1 mmol) and 0.1 mmol of ionic liquid tetrabutylammonium lactate ([N 4444 [Lac]), 5 mmol of p-toluidine was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 Nuclear magnetic resonance (NMR) analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 98%, and the product was N-p-tolyl lactamide with a separation yield of 96%.

[0052] NMR data for N-p-tolyl lactamide: 1H NMR (400MHz, DMSO-d6, 25℃): δ = 9.47 (s, 1H), 7.56 (d, J = 8.4Hz, 2H), 7.09 (d, J = 8.4Hz, 2H),5.65(d,J=8.8Hz,1H),4.09-4.15(m,1H),2.25(s,3H),1.29ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=173.2, 136.1, 132.2, 128.9, 119.5, 67.7, 20.9, 20.4ppm.

[0053] Example 11: Preparation of N-m-tolyl lactamide by the reaction of polylactic acid and m-toluidine catalyzed by tetrabutylammonium lactate.

[0054] 72 mg of polylactic acid (monomer: 1 mmol) and 0.5 mmol of ionic liquid tetrabutylammonium lactate ([N) were added. 4444 [Lac]), 10 mmol of m-toluidine was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 94%, and the product was N-m-tolyl lactamide with a separation yield of 92%.

[0055] NMR data for N-m-tolyl lactamide: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 9.50 (s, 1H), 7.54 (s, 1H), 7.46-7.49 (m, 1H), 7.14-7.20 (m, 1H), 6. 86-6.88(m,1H),5.70(d,J=7.6Hz,1H),4.08-4.17(m,1H),2.27(s,3H),1.29ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25°C): δ = 173.4, 138.5, 137.7, 128.4, 124.0, 120.0, 116.7, 67.7, 21.2, 20.9ppm.

[0056] Example 12: Preparation of N-p-methoxyphenyl lactamide by the reaction of polylactic acid and p-methoxyaniline catalyzed by tetrabutylammonium lactate.

[0057] 72 mg of polylactic acid (monomer: 1 mmol) and 0.1 mmol of ionic liquid tetrabutylammonium lactate ([N 4444 [Lac]), 5 mmol of p-methoxyaniline was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours; after the reaction was complete, saturated sodium chloride solution (5 mL) was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis determined its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 98%, and the product was N-p-methoxyphenyl lactamide with a separation yield of 96%. NMR data for N-p-methoxyphenyl lactamide: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 9.56 (s, 1H), 7.40-7.41 (m, 1H), 7.21-7.22 (m, 1H), 7.16-7 .19(m,1H),6.62-6.64(m,1H),4.11-4.16(m,1H),3.72(s,3H),1.30ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=173.5, 159.5, 139.8, 129.4, 111.8, 108.9, 105.3, 67.8, 55.0, 20.9ppm.

[0058] Example 13: Preparation of N-benzyl lactamide by the reaction of polylactic acid and benzylamine catalyzed by tetrabutylammonium lactate.

[0059] 72 mg of polylactic acid (monomer: 1 mmol) and 10 mmol of tetrabutylammonium lactate ionic liquid were added. 4444 [Lac]), 2 mmol of benzylamine was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to a 120 °C oil bath and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis determined its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 96%, and the product was N-benzyl lactamide with a separation yield of 92%. NMR data for N-benzyl lactamide: 1H NMR (400MHz, DMSO-d6, 25℃): δ = 8.87 (s, 1H), 7.30-7.32 (m, 2H), 7.28-7.29 (m, 1H), 7 .22-7.24(m,2H),5.48(m,1H),4.40(s,2H),4.02(m,1H),1.14ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=173.0, 137.9, 128.5, 126.9, 126.7, 67.2, 43.9, 19.3ppm.

[0060] Example 14: Preparation of N-butyllacticamide from polylactic acid and butylamine catalyzed by tetrabutylammonium lactate.

[0061] 72 mg of polylactic acid (monomer: 1 mmol) and 10 mmol of tetrabutylammonium lactate ionic liquid were added. 4444 [Lac]), 3 mmol of butylamine were placed in a 20 mL glass pressure-resistant reaction tube and sealed; the tube was then transferred to a 120 °C oil bath and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 10 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 ¹³C NMR analysis determined its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 97%, and the product was N-butyl lactamide with a separation yield of 96%.

[0062] N-Butyllactic acid NMR data: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 8.01 (s, 1H), 5.48 (m, 1H), 4.02 (m, 1H), 3.18 (t, J = 4. 8Hz,2H),1.49(m,2H),1.29(m,2H),1.14(d,J=8.8Hz,3H),0.89ppm(t,J=4.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25°C): δ=172.7, 67.2, 39.2, 32.2, 19.8, 19.3, 13.8ppm.

[0063] Example 15: Preparation of N-propyllacticamide from the reaction of polylactic acid and propylamine catalyzed by tetrabutylammonium lactate.

[0064] 72 mg of polylactic acid (monomer: 1 mmol) and 10 mmol of tetrabutylammonium lactate ionic liquid were added. 4444[Lac]), 2 mmol of propylamine were placed in a 20 mL glass pressure-resistant reaction tube and sealed; the tube was then transferred to a 120 °C oil bath and heated with stirring for 12 hours; after the reaction was complete, saturated sodium chloride solution (5 mL) was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 ¹³C NMR analysis determined its composition and structure. Based on the analysis results, the raw material conversion rate was determined to be 97%, and the product was N-propyl lactamide with a separation yield of 96%.

[0065] NMR data of N-propylamine lactamide: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 8.01 (s, 1H), 5.48 (m, 1H), 4.02 (m, 1H), 3.18 (t ,J=4.8Hz,2H),1.54(m,2H),1.14(d,J=8.8Hz,3H),0.87ppm(t,J=4.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=172.7, 67.2, 39.2, 32.2, 19.7, 13.6ppm.

[0066] Example 16: Preparation of N-dipropyllacticamide by the reaction of polylactic acid and dipropylamine catalyzed by tetrabutylammonium lactate.

[0067] 72 mg of polylactic acid (monomer: 1 mmol) and 10 mmol of tetrabutylammonium lactate ionic liquid were added. 4444 [Lac]) 3 mmol of dipropylamine was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to a 120 °C oil bath and heated with stirring for 12 hours; after the reaction was complete, saturated sodium chloride solution (5 mL) was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis was performed to determine its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 97%, and the product was N-dipropyl lactamide with a separation yield of 96%.

[0068] NMR data of N-dipropylamine lactamide: 1H NMR (400MHz, DMSO-d6, 25℃): δ = 8.00 (s, 1H), 5.48 (m, 1H), 4.02 (m, 1H), 3.19 (t ,J=4.8Hz,4H),1.55(m,4H),1.14(d,J=8.8Hz,3H),0.88ppm(t,J=4.8Hz,6H); 13 C NMR (101MHz, DMSO-d6, 25℃): δ=172.7, 67.2, 39.2, 32.2, 19.7, 13.6ppm.

[0069] Example 17: Preparation of N-phenyllacticolhydrazide by the reaction of polylactic acid and phenylhydrazine catalyzed by tetrabutylammonium lactate.

[0070] 72 mg of polylactic acid (monomer: 1 mmol) and 0.2 mmol of ionic liquid tetrabutylammonium lactate ([N 4444 [Lac]), 10 mmol of phenylhydrazine was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to a 120 °C oil bath and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis determined its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 96%, and the product was N-phenyllactic acid hydrazide with a separation yield of 94%. N-phenyllactic acid hydrazide NMR data: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 9.54 (d, J = 2.8Hz, 1H), 7.59 (d, J = 2.8Hz, 1H), 7.11-7.1 4(m,2H),6.67-6.72(m,3H),5.48(m,1H),4.08-4.14(m,1H),1.27ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25°C): δ = 174.1, 149.4, 128.6, 118.3, 112.2, 66.8, 21.0ppm.

[0071] Example 18: Preparation of N-p-tolyllactichydrazide from polylactic acid and p-toluhydrazide catalyzed by tetrabutylammonium lactate.

[0072] 72 mg of polylactic acid (monomer: 1 mmol) and 0.1 mmol of ionic liquid tetrabutylammonium lactate ([N 4444[Lac]), 8 mmol of p-toluidine was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to a 120 °C oil bath and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 NMR analysis determined its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 96%, and the product was N-p-tolyl lactohydrazide with a separation yield of 94%. NMR data for N-p-tolyl lactohydrazide: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 9.54 (d, J = 2.8Hz, 1H), 7.59 (d, J = 2.8Hz, 1H), 7.10-7.12 (m, 2H ),6.83-6.86(m,2H),5.48(m,1H),4.00-4.03(m,1H),2.32(s,3H),1.27ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25°C): δ = 174.1, 149.4, 131.6, 128.5, 113.1, 69.2, 21.3, 19.6ppm.

[0073] Example 19: Preparation of N-m-tolyllactichydrazide by the reaction of polylactic acid and m-tolylhydrazide catalyzed by tetrabutylammonium lactate.

[0074] 72 mg of polylactic acid (monomer: 1 mmol) and 0.5 mmol of ionic liquid tetrabutylammonium lactate ([N) were added. 4444 [Lac]), 10 mmol of m-toluidine was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours; after the reaction was complete, 5 mL of saturated sodium chloride solution was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 ¹³C NMR analysis determined its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 90%, and the product was N-m-tolyl lactohydrazide with a separation yield of 87%.

[0075] NMR data for N-m-tolyl lactohydrazide: 1H NMR (400MHz, DMSO-d6, 25℃): δ = 9.54 (d, J = 2.8Hz, 1H), 7.59 (d, J = 2.8Hz, 1H), 7.10-7.12 (m, 1H), 7.00 (s, 1H), 6.96-6.98(m,1H),6.56-6.58(m,1H),5.48(m,1H),4.00-4.03(m,1H),2.27(s,3H),1.14ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25°C): δ = 174.1, 147.6, 138.9, 129.1, 119.4, 112.8, 111.0, 69.2, 21.5, 19.6ppm.

[0076] Example 20: Preparation of N-p-methoxyphenyllacticolhydrazide by the reaction of polylactic acid with p-methoxyphenylhydrazine catalyzed by tetrabutylammonium lactate.

[0077] 72 mg of polylactic acid (monomer: 1 mmol) and 0.1 mmol of ionic liquid tetrabutylammonium lactate ([N 4444 [Lac]), 5 mmol of p-methoxyphenylhydrazine was placed in a 20 mL glass pressure-resistant reaction tube and sealed; it was then transferred to an oil bath at 120 °C and heated with stirring for 12 hours; after the reaction was complete, saturated sodium chloride solution (5 mL) was added to the system, and the mixture was allowed to stand for 5 minutes. The mixture was extracted three times with 5 mL of ethyl acetate, the organic phases were combined, dried over anhydrous sodium sulfate for 30 minutes, concentrated, and purified by silica gel column chromatography to obtain the product. 1 H and 13 ¹³C NMR analysis determined its composition and structure. Based on the analysis results, the conversion rate of the raw material was determined to be 96%, and the product was N-p-methoxyphenyl lactohydrazide with a separation yield of 94%.

[0078] N-p-methoxyphenyl lactohydrazide NMR data: 1 H NMR (400MHz, DMSO-d6, 25℃): δ = 9.54 (d, J = 2.8Hz, 1H), 7.59 (d, J = 2.8Hz, 1H), 7.10-7.12 (m, 2H ),6.83-6.86(m,2H),5.48(m,1H),4.00-4.03(m,1H),3.32(s,3H),1.27ppm(d,J=8.8Hz,3H); 13 C NMR (101MHz, DMSO-d6, 25°C): δ = 174.1, 149.4, 131.6, 128.5, 113.1, 69.2, 55.8, 19.6ppm.

Claims

1. A method for preparing N-substituted lactamides, comprising the following steps: using an ionic liquid as a solvent and catalyst, reacting polylactic acid with an organic amine compound via an aminolysis reaction to generate the N-substituted lactamide; The organic amine compound is selected from any one of phenylhydrazine, p-methylphenylhydrazine, m-methylphenylhydrazine, and p-methoxyphenylhydrazine; The ionic liquid is tetrabutylammonium lactate; The N-substituted lactamides are selected from any one of the following: 。 2. The method according to claim 1, characterized in that: The molar ratio of the ionic liquid to the polylactic acid monomer unit is selected to be 1:100 to 10:1; The molar ratio of the organic amine compound to the polylactic acid monomer unit is 20:1 to 1:

1.

3. The method according to claim 1 or 2, characterized in that: The reaction temperature is 80~180℃; The reaction time is 5 to 20 hours.

4. The method according to claim 1 or 2, characterized in that: The method further includes the step of separating N-substituted lactamides from the reaction system by column chromatography after the reaction is completed.

5. The method according to claim 4, characterized in that: The specific steps are as follows: After the reaction is completed, saturated sodium chloride solution is added to the reaction system and allowed to stand for 5 minutes; the system is extracted three times with ethyl acetate, the organic phases are combined, dried over anhydrous sodium sulfate, concentrated, and purified by silica gel chromatography to obtain the product.

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