A heterogeneous nanostructure photocatalyst, its preparation method and application

Abstract

This invention discloses a heterogeneous nanostructure photocatalyst, its preparation method, and its application. The invention modifies the surface of the g-C3N4 photocatalyst by introducing carbon quantum dots (CDs) through doping technology. The CDs / g-C3N4 composite photocatalyst abandons conventional metal catalysis, and its preparation process is simple, low-cost, and reusable without deactivation, making it a promising new composite photocatalyst in the field of visible light catalytic oxidation technology. Applying this catalyst to the visible light selective catalytic oxidation synthesis of the key intermediate 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione demonstrates good yields.

Description

Technical Field

[0001] This invention belongs to the technical field of semiconductor photocatalyst material preparation, specifically relating to a heterogeneous nano-heterojunction photocatalyst, its preparation method, and its application. Background Technology

[0002] g-C3N4 is a typical polymer semiconductor with advantages such as good physicochemical stability, non-toxicity, a suitable bandgap energy of approximately 2.7 eV, and visible light absorption. The triazine or heptaazine CN atoms in its structure form a highly delocalized π-conjugated system through sp2 hybridization, which can effectively activate molecular oxygen and generate superoxide radicals for the catalytic oxidation of organic functional groups. However, the very low quantum efficiency of g-C3N4 limits its practical applications.

[0003] Carbon quantum dots (CDs), a novel type of carbon nanoparticle, are dispersed, spherical nanoparticles with a size of less than 10 nm. Because carbon quantum dots can efficiently capture sunlight and exhibit excellent photo-oxidation capabilities under illumination, along with remarkable conversion photoluminescence and outstanding photoinduced electron transfer capabilities, they can be combined with other semiconductor nanoparticles as light absorbers to improve their photocatalytic performance.

[0004] Unlike other carbon sources, citric acid possesses abundant functional groups and active centers, making it easier to synthesize fluorescent carbon nanomaterials through cross-linking and carbonization reactions. Due to the coupling reaction between -NH2 and -COOH, modifying the surface of citric acid carbon quantum dots with o-phenylenediamine through heat treatment can significantly enhance the graphitization degree of the formed carbon quantum dots, thereby modulating their fluorescence properties. Therefore, systematically studying the electronic structure and optical properties of g-C3N4 supported on citric acid carbon quantum dots is of urgent and important significance for photocatalytic applications.

[0005] Lenalidomide, chemically named 3-(4-amino-1-oxoisoindol-2-yl)piperidine-2,6-dione, is used to treat subtypes of myelodysplastic syndrome (MDS) and multiple myeloma, and is widely used in treatment regimens for various rare diseases. In the prior art, lenalidomide is obtained by amination of the key intermediate 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione of formula (Ⅰ), as shown below:

[0006]

[0007] Numerous methods exist for synthesizing lenalidomide, but they suffer from drawbacks such as complex preparation processes, low synthesis efficiency, low production safety, and difficulty in industrial-scale production. Therefore, current methods for preparing lenalidomide still require improvement. Consequently, research and exploration into the synthesis of lenalidomide and its key intermediate (Ⅰ, the nitro reduction product of lenalidomide) are of great significance. Patent CN111548341 A describes a method for preparing the key intermediate (Ⅰ) of lenalidomide, and its synthetic route is as follows:

[0008]

[0009] The selective oxidation of 3-(4-nitro-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione (II) obtained after condensation to obtain lenalidomide intermediate (I) has a low yield, the catalyst is not recyclable, and the reaction conditions need to be carried out at high temperature, which to some extent restricts the effectiveness of this route for large-scale preparation. Summary of the Invention

[0010] To address the above problems, the present invention aims to provide a heterogeneous nano-heterojunction photocatalyst, its preparation method, and its application.

[0011] To achieve the above objectives, the following technical solution is provided:

[0012] A method for preparing a heterogeneous nanostructure photocatalyst includes the following steps:

[0013] 1) Preparation of carbon quantum dot solution: Carbon quantum dot solution is prepared by hot water method. Citric acid is used as carbon source. Citric acid and o-phenylenediamine are dissolved in deionized water and then transferred to a hydrothermal reactor for high-temperature reaction to form carbon quantum dot solution through thermal polymerization.

[0014] 2) Preparation of g-C3N4: Melamine and ammonium salt were mixed and ground evenly, then placed in a muffle furnace and heated and calcined. The calcined solid was then pulverized to obtain g-C3N4.

[0015] 3) Preparation of CDs / g-C3N4 catalyst: Take an appropriate amount of g-C3N4 obtained in step 2) and ultrasonically disperse it in the carbon quantum dot solution obtained in step 1), so that the carbon quantum dots can grow in situ and be uniformly distributed on the surface of g-C3N4. Impregnate at room temperature and dry at high temperature to obtain a solid powder labeled as CDs / g-C3N4 catalyst.

[0016] Further, the molar ratio of citric acid and o-phenylenediamine in step 1) is 1:0.5-3.

[0017] Further, the ammonium salt mentioned in step 2) is one or more of ammonium carbonate, ammonium bicarbonate and ammonium sulfate, and the mass ratio of melamine to ammonium salt is 1:0.01-18.

[0018] Further, in step 3), g-C3N4 and carbon quantum dot solution are ultrasonically dispersed at a mass-volume ratio of 1g:1-10mL.

[0019] A heterogeneous nanostructure photocatalyst prepared by the above preparation method is provided, wherein the carbon quantum dots are spherical nanoparticles, the g-C3N4 is a nanostructure, and the carbon quantum dots and g-C3N4 are closely arranged to form a heterostructure.

[0020] The application of a heterogeneous nanostructure photocatalyst in the synthesis of a key intermediate of lenalidomide involves using a 3-(4-nitro-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione compound as shown in formula (II) as a raw material. This compound is dispersed in an organic solvent along with a CDs / g-C3N4 catalyst and an oxidant, and undergoes a selective oxidation reaction under visible light irradiation. After the reaction, the resulting 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione compound, the key intermediate of lenalidomide shown in formula (I), is obtained. The reaction formula is as follows:

[0021] .

[0022] Furthermore, the visible light is white, red, green, blue, or violet, with a power of 6-30W.

[0023] Furthermore, the oxidant is oxygen.

[0024] Furthermore, the organic solvent is selected from one or more of tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, 1,2-dichloroethane, or acetonitrile.

[0025] The beneficial effects of this invention are as follows:

[0026] 1) This invention introduces carbon quantum dots into the g-C3N4 material structure, which can reduce the band gap of the catalyst and improve the separation efficiency of the hole-electron pair in g-C3N4, thereby enhancing the activity of the catalyst. Carbon quantum dots are loaded onto g-C3N4 material by hydrothermal method to form a heterostructure. This heterostructure can serve as an electron transport channel to achieve rapid electron transfer and prevent electron-hole recombination. At the same time, the uniform distribution of carbon quantum dots on the surface of g-C3N4 can effectively increase the contact area with the reaction substrate and provide more sites for the reaction.

[0027] 2) This invention uses ammonium salt as raw material, which can utilize the amino groups in its molecular structure to form hydrogen bonds with melamine, thereby inhibiting the aggregation phenomenon that may occur in the g-C3N4 polymerization process and subsequent reactions to a certain extent, increasing the surface area of ​​the catalyst to ensure the stability of its performance, and allowing it to be recycled and reused multiple times without deactivation.

[0028] 3) This invention completely avoids using metals as raw materials, and the preparation process is simple and inexpensive;

[0029] 4) This invention uses visible light selective oxidation to obtain the key intermediate of lenalidomide, which broadens the synthetic route of lenalidomide. The reaction conditions are mild, the equipment requirements are low, and it is more suitable for industrial production. Attached Figure Description

[0030] Figure 1 The X-ray diffraction pattern of the heterogeneous nanostructure composite photocatalyst of g-C3N4 and CDs / g-C3N4 in Specific Example 6 of the present invention is shown.

[0031] Figure 2 This is an example of the CDs / g-C3N4 catalyst used in the repeated recovery experiment of a key intermediate in the visible light selective catalytic oxidation synthesis of the drug lenalidomide, as described in Specific Example 21 of the present invention. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings and embodiments, but the scope of protection of the present invention is not limited thereto.

[0033] Example 1

[0034] Preparation of heterogeneous nanostructure composite photocatalysts:

[0035] 1) Preparation of carbon quantum dot solution: Citric acid (192 mg, 1 mmol) and o-phenylenediamine (108 mg, 1 mmol) were dissolved in 10 mL of deionized water and stirred until they were mixed evenly and the solution showed a clear dispersion. The synthesized dispersion was then transferred to a hydrothermal reactor and the temperature was raised to 240 °C for 6 h. After the hydrothermal reactor cooled naturally to room temperature, the reaction solution was collected.

[0036] 2) Preparation of g-C3N4: Melamine (0.4g, 3.17mmol) and ammonium carbonate (1g, 10.41mmol) were mixed, ground and dispersed, and then placed in a muffle furnace and heated to 400℃ for 3h. The solid after calcination was crushed to obtain g-C3N4 with nitrogen defects.

[0037] 3) Preparation of CDs / g-C3N4 catalyst: 1g of g-C3N4 yellow powder was dispersed in 10mL of carbon quantum dot solution prepared in step (1) and ultrasonically treated (400w, 15min) to obtain a uniformly dispersed suspension, so that CDs grow in situ and are uniformly distributed on the surface of g-C3N4. The solution was impregnated at room temperature for 24h and finally dried at 200℃ for 6h. The resulting solid powder was labeled as CDs / g-C3N4.

[0038] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0039]

[0040] 1.5 g (5.45 mmol) of 3-(4-nitro-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione, as shown in formula (II), and 20 mg of heterogeneous nanostructured composite photocatalyst (CDs / g-C3N4) were dispersed in 5 ml of 1,4-dioxane reaction solvent and reacted under 6 W blue light irradiation in an oxygen atmosphere for 3 h. After the reaction was completed, the catalyst was removed by filtration, and the solvent was removed by concentration under reduced pressure to obtain the crude product. The crude product was obtained by slurrying with petroleum ether:ethyl acetate (volume ratio of 3:1) to obtain a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione, with a yield of 45.4% and an HPLC purity of 93.2%.

[0041] 1 H NMR (400 MHz, DMSO-d 6) δ 11.03 (s, 1H), 8.47 (d, J=7.7 Hz, 1H), 8.19 (d, J=7.3Hz, 1H), 7.84 (t, J=7.8 Hz, 1H), 5 .18 (dd,J=13.1, 5.1 Hz, 1H), 4.95-4.76 (m,2H), 2.92 (ddd, J=17.1, 13.4, 5.3 Hz, 1H), 2.64-2.51 (m, 2H), 2.10-1.98 (m, 1H).

[0042] The recovered CDs / g-C3N4 catalyst was thoroughly washed with methanol (5×3mL) and water (5×3mL), and the solid and washing liquid were separated by centrifugation. It was then dried at 60°C for 6 hours and applied again to the visible light selective catalytic oxidation synthesis of the key intermediate of the drug lenalidomide. The application process was the same as above.

[0043] Example 2

[0044] Preparation of heterogeneous nanostructure composite photocatalysts:

[0045] The preparation process is the same as in Example 1, except that the mass of o-phenylenediamine in step 1) is replaced with 216 mg and 2 mmol.

[0046] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0047] The method of Example 1 was followed to synthesize a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 50.3% and an HPLC purity of 92.7%.

[0048] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0049] Example 3

[0050] Preparation of heterogeneous nanostructure composite photocatalysts:

[0051] The preparation process is the same as in Example 1, except that the mass of ammonium carbonate in step 2) is replaced with 3g and 31.23mmol.

[0052] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0053] The method of Example 1 was followed to synthesize a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 53.6% and an HPLC purity of 92.9%.

[0054] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0055] Example 4

[0056] Preparation of heterogeneous nanostructure composite photocatalysts:

[0057] The preparation process is the same as in Example 1, except that the reaction temperature in the hydrothermal reactor in step 1) is changed to 120°C.

[0058] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0059] The method of Example 1 was followed to synthesize a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 55.8% and an HPLC purity of 92.7%.

[0060] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0061] Example 5

[0062] Preparation of heterogeneous nanostructure composite photocatalysts:

[0063] The preparation process was the same as in Example 4, except that the mass of melamine was changed to 2g (15.87mmol) and the mass of ammonium carbonate was changed to 1g (10.41mmol).

[0064] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0065] The method of Example 1 was followed to synthesize a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 66.0% and an HPLC purity of 94.9%.

[0066] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0067] Example 6

[0068] Preparation of heterogeneous nanostructure composite photocatalysts:

[0069] The preparation process was the same as in Example 4, except that the mass of melamine was changed to 20g (158.58mmol) and the mass of ammonium carbonate was changed to 15g (156.11mmol).

[0070] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0071] The method of Example 1 was followed to synthesize a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 68.9% and an HPLC purity of 96.7%.

[0072] The X-ray diffraction pattern of the prepared g-C3N4 and CDs / g-C3N4 heterogeneous nanostructure composite photocatalyst is shown below. Figure 1 As shown.

[0073] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0074] Example 7

[0075] Preparation of heterogeneous nanostructure composite photocatalysts:

[0076] The preparation process is the same as in Example 6.

[0077] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0078] Synthesized according to the method in Example 1, with the blue light changed to 12W, a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione was obtained with a yield of 73.7% and an HPLC purity of 98.7%.

[0079] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0080] Example 8

[0081] Preparation of heterogeneous nanostructure composite photocatalysts:

[0082] The preparation process is the same as in Example 6.

[0083] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0084] Synthesized according to the method in Example 1, with the blue light changed to 24W, a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione was obtained with a yield of 75.5% and an HPLC purity of 98.3%.

[0085] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0086] Example 9

[0087] Preparation of heterogeneous nanostructure composite photocatalysts:

[0088] The preparation process is the same as in Example 6.

[0089] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0090] Synthesized according to the method in Example 1, with the blue light changed to 30W, a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione was obtained with a yield of 75.5% and an HPLC purity of 98.3%.

[0091] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0092] Example 10

[0093] Preparation of heterogeneous nanostructure composite photocatalysts:

[0094] The preparation process is the same as in Example 6.

[0095] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0096] Synthesized according to the method in Example 8, with the visible light reaction time changed to 6 h, yielding a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 95.3% and an HPLC purity of 96.6%.

[0097] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0098] Example 11

[0099] Preparation of heterogeneous nanostructure composite photocatalysts:

[0100] The preparation process is the same as in Example 6.

[0101] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0102] Synthesized according to the method in Example 8, with the visible light reaction time changed to 12 h, yielding a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 70.1% and an HPLC purity of 96.6%.

[0103] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0104] Example 12

[0105] Preparation of heterogeneous nanostructure composite photocatalysts:

[0106] The preparation process is the same as in Example 6.

[0107] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0108] The method of Example 10 was followed, but the visible light source was changed to white light to obtain a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 80.1% and an HPLC purity of 97.7%.

[0109] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0110] Example 13

[0111] Preparation of heterogeneous nanostructure composite photocatalysts:

[0112] The preparation process is the same as in Example 6.

[0113] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0114] Synthesized according to the method of Example 10, with the visible light source changed to red light, a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione was obtained with a yield of 50.8% and an HPLC purity of 92.5%.

[0115] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0116] Example 14

[0117] Preparation of heterogeneous nanostructure composite photocatalysts:

[0118] The preparation process is the same as in Example 6.

[0119] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0120] Synthesized according to the method of Example 10, with the visible light source changed to green light, a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione was obtained with a yield of 31.0% and an HPLC purity of 95.6%.

[0121] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0122] Example 15

[0123] Preparation of heterogeneous nanostructure composite photocatalysts:

[0124] The preparation process is the same as in Example 6.

[0125] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0126] Synthesized according to the method of Example 10, with the visible light source changed to violet light, a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione was obtained with a yield of 84.7% and an HPLC purity of 98.4%.

[0127] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0128] Example 16

[0129] Preparation of heterogeneous nanostructure composite photocatalysts:

[0130] The preparation process is the same as in Example 6.

[0131] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0132] Synthesized according to the method of Example 10, the reaction solution was replaced with tetrahydrofuran to obtain a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 85.8% and an HPLC purity of 98.8%.

[0133] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0134] Example 17

[0135] Preparation of heterogeneous nanostructure composite photocatalysts:

[0136] The preparation process is the same as in Example 6.

[0137] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0138] Synthesized according to the method of Example 10, the reaction solution was replaced with N,N-dimethylformamide to obtain a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 85.8% and an HPLC purity of 98.8%.

[0139] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0140] Example 18

[0141] Preparation of heterogeneous nanostructure composite photocatalysts:

[0142] The preparation process is the same as in Example 6.

[0143] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0144] The reaction solution was replaced with dimethyl sulfoxide according to the method of Example 10, yielding a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 93.8% and an HPLC purity of 95.4%. Repeated recovery experiments of the CDs / g-C3N4 catalyst were conducted according to the method of Example 1.

[0145] Example 19

[0146] Preparation of heterogeneous nanostructure composite photocatalysts:

[0147] The preparation process is the same as in Example 6.

[0148] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0149] Synthesized according to the method of Example 10, the reaction solution was replaced with 1,2-dichloroethane to obtain a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 90.0% and an HPLC purity of 92.95%.

[0150] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0151] Example 20

[0152] Preparation of heterogeneous nanostructure composite photocatalysts:

[0153] The preparation process is the same as in Example 6.

[0154] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0155] Synthesized according to the method of Example 10, but with the reaction solution replaced by acetonitrile, yielding a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione with a yield of 98.1% and an HPLC purity of 96.2%.

[0156] The repeated recovery experiments of the CDs / g-C3N4 catalyst were conducted according to the method in Example 1. After multiple recovery cycles, the catalytic activity was as follows: Figure 2 As shown, from Figure 2 The results showed that after multiple recycling processes, its catalytic activity only decreased slightly.

[0157] Example 21

[0158] Preparation of heterogeneous nanostructure composite photocatalysts:

[0159] The preparation process is the same as in Example 6.

[0160] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0161] The heterogeneous nano-heterojunction composite photocatalyst (CDs / g-C3N4) was synthesized according to the method of Example 20, with the dosage of 10 mg replaced to obtain a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione, with a yield of 34.1% and an HPLC purity of 93.8%.

[0162] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0163] Example 22

[0164] Preparation of heterogeneous nanostructure composite photocatalysts:

[0165] The preparation process is the same as in Example 6.

[0166] Application of key intermediates in the visible light selective catalytic oxidation synthesis of the drug lenalidomide:

[0167] The heterogeneous nano-heterojunction composite photocatalyst (CDs / g-C3N4) was synthesized according to the method of Example 20, with the dosage of 40 mg replaced to obtain a grayish-white solid 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione, with a yield of 34.1% and an HPLC purity of 93.8%.

[0168] The repeated recovery experiments of CDs / g-C3N4 catalyst were carried out according to the method in Example 1.

[0169] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit the present invention. 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 invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications and substitutions should be covered within the scope of the claims of the present invention.

Claims

1. The application of a heterogeneous nanostructure photocatalyst in the synthesis of a key intermediate of lenalidomide, characterized in that, Using 3-(4-nitro-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione compounds as shown in formula (II) as raw materials, they were dispersed in an organic solvent together with CDs / g-C3N4 catalyst and oxidant, and subjected to selective oxidation reaction under visible light irradiation. After the reaction, the key intermediate of lenalidomide, 3-(4-nitro-1-oxo-1,3-dihydro-2H-isoindol-2-yl)piperidine-2,6-dione compounds as shown in formula (I), was obtained. The reaction formula is as follows: ； A method for preparing heterogeneous nanostructure photocatalysts, characterized by comprising the following steps: 1) Preparation of carbon quantum dot solution: Carbon quantum dot solution is prepared by hot water method. Citric acid is used as carbon source. Citric acid and o-phenylenediamine are dissolved in deionized water and then transferred to a hydrothermal reactor for high-temperature reaction to form carbon quantum dot solution through thermal polymerization. 2) Preparation of g-C3N4: Melamine and ammonium salt were mixed and ground evenly, then placed in a muffle furnace and heated and calcined. The calcined solid was then pulverized to obtain g-C3N4. 3) Preparation of CDs / g-C3N4 catalyst: Take an appropriate amount of g-C3N4 obtained in step 2) and ultrasonically disperse it in the carbon quantum dot solution obtained in step 1), so that the carbon quantum dots can grow in situ and be uniformly distributed on the surface of g-C3N4. Impregnate at room temperature and dry at high temperature to obtain a solid powder labeled as CDs / g-C3N4 catalyst.

2. The application as described in claim 1, characterized in that, The molar ratio of citric acid and o-phenylenediamine mentioned in step 1) is 1:0.5-3.

3. The application as described in claim 1, characterized in that, The ammonium salt mentioned in step 2) is one or more of ammonium carbonate, ammonium bicarbonate and ammonium sulfate, and the mass ratio of melamine to ammonium salt is 1:0.01-18.

4. The application as described in claim 1, characterized in that, In step 3), g-C3N4 and carbon quantum dot solution are ultrasonically dispersed at a mass-volume ratio of 1g:1-10mL.

5. The application as described in claim 1, characterized in that, Visible light includes white, red, green, blue, or violet light, with a power of 6-30W.

6. The application as described in claim 1, characterized in that, The oxidant is oxygen.

7. The application as described in claim 1, characterized in that, The organic solvent is selected from one or more of tetrahydrofuran, N,N-dimethylformamide, dimethyl sulfoxide, 1,4-dioxane, 1,2-dichloroethane, or acetonitrile.

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