Method for visible light catalytic cracking of beta-O-4 type lignin model compound

Abstract

The invention discloses a method for catalytic cracking of a beta-O-4 type lignin model compound by visible light, which comprises the following steps: in an inert atmosphere, mixing a photosensitizer, a beta-O-4 type lignin model compound as shown in a formula I, protonic acid, amine and a solvent, reacting for 6-48 hours under the conditions of visible light irradiation and 25-45 DEG C, and post-treating the reaction liquid to obtain the beta-O-4 type lignin model compound. Respectively obtaining an aromatic ketone compound as shown in a formula II and a phenolic compound as shown in a formula III; the method is mild, efficient, green, economical and suitable for large-scale production; # imgabs0 #

Description

Technical Field

[0001] The invention relates to a method for catalytic cracking of lignin type compounds, and in particular to a method for catalytic cracking of a beta-O-4 type lignin model compound under visible light to obtain a value-added small molecule product. Background Art

[0002] The demand for energy in modern society is increasing. The use of traditional energy will not only cause the depletion of fossil resources, but also seriously pollute the environment. Biomass is a recognized promising alternative to fossil fuels. Lignin is the most abundant natural phenolic polymer in nature, accounting for about 20% to 30% of the total mass of biomass. The unique aromatic structure of lignin gives it a unique advantage in catalytic conversion into high-value aromatic chemicals, of which β-O-4 bonds account for 43% to 62% of natural lignin bonds. By cracking the β-O-4 bonds in the structure, the lignin macromolecules are depolymerized to obtain value-added small molecule products. The reaction formula is as follows:

[0003]

[0004] Photocatalytic cleavage of β-O-4 bonds within lignin molecules yields value-added aromatic small molecules

[0005] Based on this, in the past few decades, researchers have developed different strategies for catalytic cracking of lignin-type compounds. Among them, Song et al. used AuNPs / Li-Al LDH catalysts to oxidatively depolymerize organic solvent lignin and kraft lignin (see Chemical Science., 2018, 9 (42), 8127-8133.). Sales et al. reported the catalytic oxidation of lignin by Pd / γ-Al2O3 catalyst under the action of oxygen, and a series of aromatic aldehyde products were obtained by breaking CC bonds during the reaction (see Chemical Engineering Science., 2007, 62 (18-20), 5386-5391.). Dabral et al. developed a TEMPO / DAIB catalytic system, which obtained 15% of organic components from the oxidation of lignin by breaking β-O-4 bonds and CC bonds (see Chemsuschem., 2017, 10 (13), 2707-2713.). Lin et al. selected CrCl3 and Pd / C as bifunctional catalysts, which had a synergistic effect on the cracking and hydrogenation of β-O-4 bonds, preventing the polymerization of reaction intermediates and obtaining 19.2 wt.% of aromatic monomers (see Journal of the Energy Institute., 2020, 93(2), 784-791.). Gong et al. used TiO2 co-modified with Bi and Pt to oxidatively depolymerize lignin sulfonate under sunlight (see Applied Catalysis B: Environmental., 2017, 204, 296-303.). Luo et al. reported the use of DPA-BP / NHPI / O2 photocatalytic system for aerobic oxidation of β-O-4 lignin model compounds (see Journal of Organic Chemistry., 2016, 81(19), 9131-9137.).

[0006] Unfortunately, the above-mentioned methods for catalytic cracking of lignin-type compounds all have more or less disadvantages such as harsh reaction conditions, expensive and difficult to obtain catalysts, low yield of target products, and cumbersome operations. In 2019, Gabriel's research group achieved the co-catalytic cracking of β-O-4 type lignin model compounds at room temperature using blue LED light source irradiation and [Ir(ppy)2(dtbbpy)]PF6 (see ACS Catalysis., 2019, 9, 2252-2260.). Although this method has mild reaction conditions and high conversion rate of target products, it still has limitations such as lack of substrate universality, expensive and difficult to obtain precious metal Ir as a catalyst, and poor economic practicality. Therefore, it is particularly important to find an economical, green, mild and efficient method for catalytic cracking of β-O-4 type lignin model compounds. Summary of the invention

[0007] In view of the limitations of current catalytic cracking technology, the present invention provides a method for visible light catalytic cracking of β-O-4 type lignin model compounds.

[0008] In the present invention, the oxidized β-O-4 type lignin model compound undergoes intramolecular CO bond homolysis under photocatalytic conditions to obtain value-added small molecular phenols and aromatic ketone compounds; the photocatalytic conditions are visible light irradiation and the addition of photosensitizers, amines, and protonic acids. The method of the present invention is mild, efficient, green, economical, and suitable for scale-up production.

[0009] The technical solution of the present invention is as follows:

[0010] A method for catalytically cracking a β-O-4 type lignin model compound using visible light, comprising:

[0011] Under an inert atmosphere, a photosensitizer, a β-O-4 type lignin model compound represented by formula I, a protonic acid, an amine and a solvent are mixed, and reacted for 6 to 48 hours (preferably 16 hours) under visible light irradiation and 25 to 45° C. (preferably 30° C.), and then the reaction solution is post-treated to obtain an aromatic ketone compound represented by formula II and a phenolic compound represented by formula III, respectively;

[0012] in,

[0013] The molar ratio of the β-O-4 type lignin model compound shown in formula I, amine, protonic acid, and photosensitizer is 1:1.5-3:0.01-0.15:0.02-0.1, preferably 1:2.5:0.1:0.05;

[0014] The photosensitizer is selected from at least one of copper-based photosensitizer PS1, copper-based photosensitizer PS2, copper-based photosensitizer PS3, copper-based photosensitizer PS4, copper-based photosensitizer PS5, and organic photosensitizer PS6; preferably copper-based photosensitizer PS2;

[0015] The structural formula of the photosensitizer is as follows:

[0016]

[0017] The protonic acid is selected from hydrochloric acid, nitric acid, formic acid or acetic acid, preferably formic acid;

[0018] The amine is selected from triethylamine, tetramethylethylenediamine or diisopropylethylamine, preferably diisopropylethylamine;

[0019] The solvent is selected from toluene, acetonitrile, ether, dichloromethane, ethyl acetate, dimethyl sulfoxide, 1,2-dichloroethane, 1,4-dioxane, methanol, ethanol or tetrahydrofuran, preferably tetrahydrofuran;

[0020] The volume molar ratio of the solvent to the β-O-4 type lignin model compound shown in formula I is 10 to 25:1, mL / mmol; preferably 20:1, mL / mmol;

[0021] The light source of visible light adopts blue LED, which can be 10W blue LED, 15W blue LED, 30W blue LED, preferably 15W blue LED; in a specific embodiment of the present invention, the Schlenk reaction tube containing the reaction solution is placed 2 to 8 cm away from the blue LED light source;

[0022] The specific post-treatment method is as follows: after the reaction is completed, 100-200 mesh column chromatography silica gel is added to the reaction solution and the solvent is removed by distillation under reduced pressure, the crude product is dry-loaded for column chromatography separation, and gradient elution is performed using petroleum ether / ethyl acetate volume ratio = 20-10:1 as an eluent, and the target compound eluate is obtained by TLC detection, and evaporated to dryness under reduced pressure to obtain the aromatic ketone compound represented by formula II and the phenol compound represented by formula III, respectively;

[0023] The reaction formula is as follows:

[0024]

[0025] In Formula I to Formula III,

[0026] R 1 is H, 4-methoxy, 3,4-bismethoxy or 3,4,5-trimethoxy, preferably 4-methoxy or 3,4-bismethoxy;

[0027] R 2 It is H, 2-methoxy, 3-methoxy, 4-methoxy, chlorine, bromine, phenyl, cyclohexyl, 3,5-dimethyl, 3,5-dimethoxy, 2,6-dimethoxy, acetyl, tert-butyl, cyano or nitro, preferably phenyl, methoxy, dimethoxy, cyclohexyl or acetyl.

[0028] Specifically, the β-O-4 type lignin model compound shown in Formula I is one of the following:

[0029]

[0030] The β-O-4 type lignin model compound of the present invention can be prepared by those skilled in the art according to the methods disclosed in existing literature.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] 1) The β-O-4 type lignin template substrate used in the technical solution can be obtained by combining cheap and diverse fragments of commercially available drugs through simple chemical reactions, so the substrate is simple and easy to obtain, and the functional groups are diverse.

[0033] 2) This technical solution obtains value-added small molecule phenols and aromatic ketone compounds by photocatalytic pyrolysis of β-O-4 type lignin model compounds. The reaction conditions are mild, the substrate is universal, the side reactions are few and the yield of the target product is high.

[0034] 3) This technical solution uses a cheap copper complex as a photosensitizer to replace the expensive and difficult-to-obtain precious metal Ir as a catalyst for catalytic cracking of the lignin template substrate. The reaction operation is simple and economical. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 : The reaction mechanism involved in the photocatalytic reaction of the present invention. DETAILED DESCRIPTION

[0036] The present invention is further described below by means of specific embodiments, but the protection scope of the present invention is not limited thereto.

[0037] The raw material β-O-4 type lignin template substrate of the present invention can be prepared according to the literature, and the typical steps are as follows:

[0038]

[0039] Weigh the phenolic compound S2 (12mmol, 1.2equiv.) and drop it into an eggplant-shaped flask equipped with a magnet, then pour acetone (50mL) into the flask to dissolve it. Weigh potassium carbonate (15mmol, 1.5equiv.) and add it to the solution and stir for 30min. Take another beaker and weigh the α-bromoacetophenone compound S1 (10mmol, 1.0equiv.) and pour acetone (20mL) into it and stir to dissolve it. Slowly drop the S1 solution into the eggplant-shaped flask. After the dropwise addition is complete, stir and heat the suspension at 70°C under reflux overnight.

[0040] After the reaction, the obtained suspension was distilled under reduced pressure to remove the solvent, and then water was added to shake and dissolve the solid. The obtained solution was extracted with ethyl acetate (3×50 mL), and the organic phases were combined and dried and filtered with anhydrous Na2SO4. 100-200 mesh column chromatography silica gel was added to the filtrate and the solvent was distilled under reduced pressure to remove the solvent. The obtained crude product was separated by column chromatography and eluted and separated with petroleum ether / ethyl acetate = 10:1 as the eluent to obtain β-O-4 type lignin template substrate S3.

[0041] The β-O-4 type lignin model compounds (I) are all known substances. 1 The H NMR characterization results were consistent with those reported in the literature.

[0042] The synthesis method of the photosensitizer PS2 used in the following examples is as follows:

[0043] Synthesis of photosensitizer PS2:

[0044]

[0045] Take a 50mL three-necked flask and add a magnetic bar. Add 4,7-diphenyl-1,10-phenanthroline (1.5mmol, 1.0equiv.) to the flask, replace argon three times, and blow with a hot air gun for 20min to dry. Add 15mL of redispersed dried toluene, then add isopropyl lithium (6mL, 4.0equiv., 1M in Hexane) dropwise under ice bath conditions, and stir the reaction at room temperature for 16 hours. After the reaction, remove toluene by rotary evaporation, then add dichloromethane to dissolve, and then add active manganese dioxide (15mmol, 10.0equiv) to the reaction solution, stir at room temperature overnight, and finally separate the yellow ligand 2,9-diisopropyl-4,7-diphenylphenanthroline (1mmol, 1.0equiv.) by column chromatography (PE:EA=20:1), with a yield of 67%.

[0046] Take a 50mL three-necked flask, add a magnetic bar and connect a condenser reflux tube, add Cu(MeCN)4PF6 (1mmol, 1.0equiv.) and 4,5-bis(diphenylphosphino)-9,9-dimethyloxanthene (1mmol, 1.0equiv.) to the flask, replace the argon gas three times, and then add redispersed and dried dichloromethane (30mL). Heat and stir at 35°C for 4 hours, then slowly add a dichloromethane (10mL) solution of 2,9-diisopropyl-4,7-diphenylphenanthroline (1mmol, 1.0equiv.) at room temperature, and continue to heat and stir at 35°C for 3 hours after the addition is complete. After the reaction is completed, cool to room temperature, slowly add the reaction solution dropwise into vigorously stirred n-hexane (150mL) to precipitate the crude product, filter and wash the filter cake with n-hexane (3×30mL), the resulting filter cake is photosensitizer PS2, the yield is 1mmol, and the yield is 100%.

[0047] Example of catalytic cracking of β-O-4 type lignin model compound:

[0048] Example 1

[0049]

[0050] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(2-methoxyphenoxy)-1-acetophenone (0.2mmol, 48mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products acetophenone and guaiacol are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are white crystals and yellow liquids, respectively, with yields of 15.8mg and 15.3mg, respectively, and yields of 66% and 62%, respectively.

[0051] Characterization Data: Acetophenone 1 H NMR (400MHz, CDCl3) δ8.01-7.89(m,2H),7.60-7.53(m,1H),7.50-7.42(m,2H),2.61(s,3H). 13 C NMR (101MHz,CDCl3)δ198.16,137.14,133.11,128.58,128.32,26.62.Guaiacol 1H NMR (400MHz, CDCl3) δ6.97-6.94(m,1H),6.90(dd,J=5.6,3.6Hz,1H),6.88-6.86(m,2H),5.69(br,1H),3.89(s,3H). 13 C NMR (101MHz, CDCl3) δ146.7,145.8,121.6,120.3,114.7,110.9,56.0.

[0052] Example 2

[0053]

[0054] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(2-methoxyphenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 54mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and guaiacol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are white crystals and yellow liquids, respectively, with yields of 23.1mg and 18.8mg, respectively, and yields of 77% and 76%, respectively.

[0055] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.94 (d, J = 8.8 Hz, 2H), 6.93 (d, J = 8.8 Hz, 2H), 3.87 (s, 3H), 2.56 (s, 3H). 13 C NMR (101MHz, CDCl3) δ196.9, 163.6, 130.7 (2C), 130.5, 113.8 (2C), 55.6, 26.5. 1 H NMR (400MHz, CDCl3) δ6.96-6.93(m,1H),6.89(dd,J=5.6,3.6Hz,1H),6.87-6.85(m,2H),5.68(br,1H),3.88(s,3H). 13 C NMR (101MHz, CDCl3) δ146.8,145.7,121.5,120.2,114.6,110.8,55.9.

[0056] Example 3

[0057]

[0058] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(3-methoxyphenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 54mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and 3-methoxyphenol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are white crystals and red liquids, respectively, with yields of 21.9mg and 17.6mg, respectively, and yields of 73% and 71%, respectively.

[0059] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.96 (d, J = 8.8 Hz, 2H), 6.95 (d, J = 8.8 Hz, 2H), 3.89 (s, 3H), 2.58 (s, 3H). 13 C NMR (101MHz, CDCl3) δ196.8, 163.5, 130.6 (2C), 130.4, 113.7 (2C), 55.5, 26.4. 3-Methoxyphenol 1 H NMR (400MHz, CDCl3) δ7.15 (t, J = 8.4Hz, 1H), 6.54 (dd, J = 1.6Hz, 7.6Hz, 1H), 6.48-6.44 (m, 2H), 5.72 (br-s, 1H), 3.79 (s, 3H). 13 CNMR (125MHz, CDCl3) δ161.10,156.83,130.28,107.86,106.58,101.62,55.41.

[0060] Example 4

[0061]

[0062] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(4-methoxyphenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 54mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and 4-methoxyphenol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are all white crystals, with yields of 24mg and 18.9mg, respectively, and yields of 75% and 76%, respectively.

[0063] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.94 (d, J = 8.8 Hz, 2H), 6.93 (d, J = 8.8 Hz, 2H), 3.87 (s, 3H), 2.56 (s, 3H). 13 C NMR (101MHz, CDCl3)δ196.9,163.6,130.7(2C),130.5,113.8(2C),55.6,26.5.4-Methoxyphenol 1 H NMR (400MHz, CDCl3) δ7.03-6.53(m,4H),4.60(s,1H),3.77(s,3H). 13 C NMR (125MHz, CDCl3) δ153.79,149.47,116.07,113.86,57.83.

[0064] Example 5

[0065]

[0066] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(2-bromophenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 64mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and o-bromophenol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are white crystals and colorless liquids, respectively, with yields of 24.9mg and 26.6mg, respectively, and yields of 83% and 77%, respectively.

[0067] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.96 (d, J = 8.8 Hz, 2H), 6.95 (d, J = 8.8 Hz, 2H), 3.89 (s, 3H), 2.58 (s, 3H). 13 C NMR (101MHz,CDCl3)δ196.8,163.5,130.6(2C),130.4,113.7(2C),55.5,26.4. o-bromophenol 1 H NMR (400MHz, CDCl3) δ7.47(dd,J=8.0,1.6Hz,1H),7.23(td,J=7.7,1.6Hz,1H),7.03(dd,J=8.2,1.6Hz,1H),6.81(td,J=7.7,1.6Hz,1H). 13 C NMR (101MHz, CDCl3) δ152.37,132.15,129.33,121.96,116.27,110.39.

[0068] Example 6

[0069]

[0070] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(3-chlorophenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 64mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and m-chlorophenol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are white crystals and white solids, respectively, with yields of 26.4mg and 21.3mg, respectively, and yields of 88% and 83%, respectively.

[0071] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.94 (d, J = 8.8 Hz, 2H), 6.93 (d, J = 8.8 Hz, 2H), 3.87 (s, 3H), 2.56 (s, 3H). 13 C NMR (101MHz, CDCl3) δ196.9, 163.6, 130.7 (2C), 130.5, 113.8 (2C), 55.6, 26.5. m-Chlorophenol 1 H NMR (400MHz, CDCl3) δ6.20-6.16 (t, J = 8Hz, 1H), 6.95-6.89 (m, 2H), 6.77-6.74 (m, 1H), 5.49 (s, br, 1H). 13 C NMR (101MHz, CDCl3) δ156.37,134.89,130.50,121.01,115.96,113.85.

[0072] Example 7

[0073]

[0074] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(biphenyl-4-oxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 63.6mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and 4-hydroxybiphenyl, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are white crystals and white solids, respectively, with yields of 23.1mg and 24.5mg, respectively, and yields of 77% and 72%, respectively.

[0075] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.95 (d, J = 8.8 Hz, 2H), 6.94 (d, J = 8.8 Hz, 2H), 3.88 (s, 3H), 2.57 (s, 3H). 13 C NMR (101 MHz, CDCl3) δ 196.8, 163.5, 130.6 (2C), 130.4, 113.7 (2C), 55.5, 26.4. 4-Hydroxybiphenyl 1 H NMR (400MHz, CDCl3) δ7.55 (t, J = 8.3Hz, 2H), 7.49 (q, J = 11.3Hz, 2H), 7.44-7.40 (m, 2H), 7.33-7.21 (m, 1H), 6.91 (d, J = 8.6Hz, 2H), 4.81 (s, br, 1H). 13 C NMR (101MHz, CDCl3) δ154.86,140.57,133.86,128.57,128.24,126.56,115.46.

[0076] Example 8

[0077]

[0078] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(cyclohexyl-4-phenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 64.8mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorne ketone and 4-cyclohexylphenol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substance was white crystal and white solid, with yields of 21 mg and 23.9 mg, and yields of 70% and 68%, respectively.

[0079] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.96 (d, J = 8.8 Hz, 2H), 6.95 (d, J = 8.8 Hz, 2H), 3.89 (s, 3H), 2.58 (s, 3H). 13 C NMR (101MHz, CDCl3)δ196.82,163.53,130.61(2C),130.42,113.71(2C),55.51,26.42.4-cyclohexylphenol 1 H NMR (400MHz, CDCl3) δ7.07(d,J=8.4Hz,2H),6.75(d,J=8.4Hz,2H),4.70(br,1H),2.43(tt,J=8.4,3.6Hz ,1H),1.93-1.79(m,4H),1.73(dd,J=12.4,3.2,1.6Hz,1H),1.62(m,1H),1.37(m,3H),1.29-1.16(m,1H). 13 CNMR (101MHz, CDCl3) δ153.5,140.5,127.8,115.0,43.7,34.7,27.0,26.2.

[0080] Example 9

[0081]

[0082] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(3,5-dimethylphenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 54mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then drop diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). The reaction tube was placed 3 cm away from a 15W blue LED light source and reacted at 30°C for 16 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and 3,5-dimethylphenol, were purified by column chromatography (eluent PE / EA=20:1-10:1). The substances were white crystals and white solids, respectively, with yields of 21.6mg and 17mg, respectively, and yields of 72% and 70%, respectively.

[0083] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.95 (d, J = 8.8 Hz, 2H), 6.94 (d, J = 8.8 Hz, 2H), 3.88 (s, 3H), 2.57 (s, 3H). 13 C NMR (101MHz,CDCl3)δ196.84,163.53,130.61(2C),130.42,113.72(2C),55.51,26.43.3,5-Dimethylphenol 1 H NMR (400MHz, CDCl3) δ6.60(s,1H),6.48(s,2H),2.28(s,6H). 13 C NMR (101MHz, CDCl3) δ155.48,139.67,122.70,113.19,21.36.

[0084] Example 10

[0085]

[0086] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-phenoxy-1-acetophenone (0.2mmol, 42mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products acetophenone and phenol are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are white crystals and colorless crystals, respectively, with yields of 13.4mg and 10mg, respectively, and yields of 56% and 52%, respectively.

[0087] Characterization Data: Acetophenone 1 H NMR (400MHz, CDCl3) δ8.02-7.88(m,2H),7.61-7.54(m,1H),7.51-7.43(m,2H),2.62(s,3H). 13 C NMR (101MHz, CDCl3) δ 198.15, 137.16, 133.15, 128.59, 128.33, 26.64. Phenol 1 H NMR (400MHz, CDCl3) δ7.30-7.22(m,2H),6.95(tt,J=7.3,1.1Hz,1H),6.89-6.79(m,2H),4.90-4.60(m,1H). 13 C NMR (101MHz, CDCl3) δ155.42,129.71,120.87,115.30.

[0088] Embodiment 11

[0089]

[0090] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(2,6-dimethoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanone (0.2mmol, 66.4mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products 3,4-dimethoxyacetophenone and 2,6-dimethoxyphenol are purified by column chromatography (eluent PE / EA=20:1-10:1). The substance was colorless crystal and white solid, with yields of 28.4 mg and 24.2 mg, respectively, and yields of 79% and 77%, respectively.

[0091] Characterization data: 3,4-dimethoxyacetophenone 1 H NMR (400MHz, CDCl3) δ7.57(dd,J=8.3,1.9Hz,1H),7.52(d,J=1.9Hz,1H),6.88(d,J=8.3Hz,1H),3.94(s,3H),3.93(s,3H),2.56(s,3H). 13 CNMR (101MHz,CDCl3)δ196.9,153.4,149.1,130.6,123.4,110.2,110.1,56.2,56.1,26.3.2,6-dimethoxyphenol 1 H NMR (400MHz, CDCl3) δ6.80 (t, J = 8.4Hz, 1H), 6.59 (d, J = 8.4Hz, 2H), 5.51 (br, 1H), 3.89 (s, 6H). 13 C NMR (101MHz, CDCl3) δ147.3(2C),134.9,119.1,104.9(2C),56.3(2C).

[0092] Example 12

[0093]

[0094] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(3,5-dimethoxyphenoxy)-1-(3,4-dimethoxyphenyl)ethanone (0.2mmol, 66.4mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products 3,4-dimethoxyacetophenone and 3,5-dimethoxyphenol are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances were colorless crystals with yields of 27 mg and 22.1 mg, and yields of 75% and 72%, respectively.

[0095] Characterization data: 3,4-dimethoxyacetophenone 1 H NMR (400MHz, CDCl3) δ7.54(dd,J=8.3,1.9Hz,1H),7.49(d,J=1.9Hz,1H),6.85(d,J=8.3Hz,1H),3.91(s,3H),3.89(s,3H),2.53(s,3H). 13 CNMR (101MHz,CDCl3)δ196.9,153.4,149.1,130.6,123.4,110.2,110.1,56.2,56.1,26.3.3,5-dimethoxyphenol 1 H NMR (400MHz, CDCl3) δ6.04 (t, J = 2.0Hz, 1H), 6.02 (d, J = 2.0Hz, 2H), 4.73 (br, s, 1H), 3.71 (s, 6H). 13 C NMR (101MHz, CDCl3) δ161.5,157.6,94.3,92.9,55.3.

[0096] Example 13

[0097]

[0098] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(2-methoxyphenoxy)-1-(3,4,5-trimethoxyphenyl)ethanone (0.2mmol, 66.4mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products 3,4,5-trimethoxyacetophenone and guaiacol are purified by column chromatography (eluent PE / EA = 20:1-10:1). The substance was white crystal and yellow liquid, with a yield of 37 mg and 20.3 mg, respectively, and a yield of 89% and 82%, respectively.

[0099] Characterization data: 3,4,5-Trimethoxyacetophenone 1 H NMR (400MHz, CDCl3) δ2.60 (s, 3H), 3.93 (d, J = 2.5Hz, 9H), 7.22 (s, 2H). 13 C NMR (101 MHz, CDCl3) δ 26.4, 56.3, 60.9, 105.9, 132.5, 143.1, 153.1, 196.9. Guaiacol 1 H NMR (400MHz, CDCl3) δ6.96-6.93(m,1H),6.89(dd,J=5.6,3.6Hz,1H),6.87-6.85(m,2H),5.68(br,1H),3.88(s,3H). 13 C NMR (101MHz, CDCl3) δ146.8,145.7,121.5,120.2,114.6,110.8,55.9.

[0100] Embodiment 14

[0101]

[0102] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(4-acetylphenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 59.6mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and p-hydroxyacetophenone, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are all white solids, with yields of 20.4mg and 19.8mg, respectively, and yields of 68% and 73%, respectively.

[0103] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.95 (d, J = 8.8 Hz, 2H), 6.94 (d, J = 8.8 Hz, 2H), 3.88 (s, 3H), 2.57 (s, 3H). 13 C NMR (101MHz, CDCl3) δ196.8, 163.5, 130.6 (2C), 130.4, 113.7 (2C), 55.5, 26.4. p-Hydroxyacetophenone 1 H NMR (400MHz, CDCl3) δ7.91 (d, J = 8.6 Hz, 2H), 6.89 (d, J = 8.6 Hz, 2H), 5.73 (br, 1H), 2.57 (br, 3H). 13 C NMR (101MHz, CDCl3) δ198.2,161.0,131.3(2C),130.1,115.6(2C),26.5.

[0104] Embodiment 15

[0105]

[0106] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(4-acetylphenoxy)-1-(3,4-dimethoxyphenyl)ethanone (0.2mmol, 65.6mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products 3,4-dimethoxyacetophenone and p-hydroxyacetophenone are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances were both white solids with yields of 25.2 mg and 20.2 mg, and yields of 70% and 74%, respectively.

[0107] Characterization data: 3,4-dimethoxyacetophenone 1 H NMR (400MHz, CDCl3) δ7.57(dd,J=8.3,1.9Hz,1H),7.52(d,J=1.9Hz,1H),6.88(d,J=8.3Hz,1H),3.94(s,3H),3.93(s,3H),2.56(s,3H). 13 CNMR (101MHz, CDCl3)δ196.9,153.4,149.1,130.6,123.4,110.2,110.1,56.2,56.1,26.3. p-Hydroxyacetophenone 1 H NMR (400MHz, CDCl3) δ7.92 (d, J = 8.6 Hz, 2H), 6.90 (d, J = 8.6 Hz, 2H), 5.74 (br, 1H), 2.58 (br, 3H). 13 C NMR (101MHz, CDCl3) δ198.21,161.02,131.32(2C),130.14,115.62(2C),26.53.

[0108] Example 16

[0109]

[0110] Photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(4-acetylphenoxy)-1-acetophenone (0.2mmol, 50.8mg, 1.0equiv.) were added to the dried Schlenk reaction tube, argon was replaced three times, and then diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL) were added dropwise. The reaction tube was placed 3 cm away from a 15W blue LED light source and reacted at 30°C for 16 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the corresponding products acetophenone and p-hydroxyacetophenone were purified by column chromatography (eluent PE / EA=20:1-10:1). The substances were all white solids, with yields of 15.4mg and 17.9mg, respectively, and yields of 64% and 66%, respectively.

[0111] Characterization Data: Acetophenone 1 H NMR (400MHz, CDCl3) δ8.02-7.88(m,2H),7.61-7.54(m,1H),7.51-7.43(m,2H),2.62(s,3H). 13 C NMR (101MHz, CDCl3)δ198.15,137.16,133.15,128.59,128.33,26.64. p-Hydroxyacetophenone 1 H NMR (400MHz, CDCl3) δ7.94 (d, J = 8.6 Hz, 2H), 6.92 (d, J = 8.6 Hz, 2H), 5.76 (br, 1H), 2.60 (br, 3H). 13 C NMR (101MHz, CDCl3) δ198.25,161.03,131.32(2C),130.14,115.62(2C),26.52.

[0112] Embodiment 17

[0113]

[0114] Photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(4-methoxyphenoxy)-1-acetophenone (0.2mmol, 48.4mg, 1.0equiv.) were added to the dried Schlenk reaction tube, argon was replaced three times, and then diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL) were added dropwise. The reaction tube was placed 3 cm away from a 15W blue LED light source and reacted at 30°C for 16 hours. After the reaction was completed, the solvent was removed by rotary evaporation, and the corresponding products acetophenone and p-methoxyphenol were purified by column chromatography (eluent PE / EA=20:1-10:1). The substances were all white solids, with yields of 16.8mg and 16.9mg, respectively, and yields of 70% and 68%, respectively.

[0115] Characterization Data: Acetophenone 1 H NMR (400MHz, CDCl3) δ8.01-7.90(m,2H),7.63-7.50(m,1H),7.53-7.43(m,2H),2.60(s,3H). 13 C NMR (101MHz,CDCl3)δ198.14,137.18,133.12,128.60,128.34,26.65.4-Methoxyphenol 1 H NMR (400MHz, CDCl3) δ7.01-6.52(m,4H),4.63(s,1H),3.78(s,3H). 13 C NMR (125MHz, CDCl3) δ153.77,149.49,116.03,113.82,57.86.

[0116] Embodiment 18

[0117]

[0118] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(4-tert-butylphenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 59.6mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and p-tert-butylphenol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are all white solids, with yields of 22.5mg and 21.9mg, respectively, and yields of 75% and 73%, respectively.

[0119] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.95 (d, J = 8.8 Hz, 2H), 6.94 (d, J = 8.8 Hz, 2H), 3.88 (s, 3H), 2.57 (s, 3H). 13 C NMR (101MHz, CDCl3) δ196.81, 163.52, 130.62 (2C), 130.41, 113.74 (2C), 55.52, 26.41. 4-tert-butylphenol 1 H NMR (400MHz, CDCl3) δ7.29-7.21(m,2H),6.80-6.74(m,2H),1.29(s,9H). 13 C NMR (101MHz, CDCl3) δ31.6, 34.1, 114.8, 126.4, 143.5, 153.2.

[0120] Embodiment 19

[0121]

[0122] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(2-nitrophenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 57.4mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and o-nitrophenol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are white solid and yellow solid, respectively, with yields of 23.7mg and 21.4mg, respectively, and yields of 79% and 77%, respectively.

[0123] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.96 (d, J = 8.8 Hz, 2H), 6.95 (d, J = 8.8 Hz, 2H), 3.89 (s, 3H), 2.58 (s, 3H). 13 C NMR (101MHz, CDCl3)δ196.82,163.53,130.61(2C),130.42,113.71(2C),55.51,26.42. o-Nitrophenol 1 H NMR (400MHz, CDCl3) δ10.59(br,1H),8.11(d,J=8.4Hz,1H),7.59(t,J=7.7Hz,1H),7.16(d,J=8.4Hz,1H),6.99(t,J=7.8Hz,1H). 13 CNMR (101MHz, CDCl3) δ155.26,137.67,133.84,125.21,120.35,120.11.

[0124] Embodiment 20

[0125]

[0126] Add photosensitizer PS2 (0.01mmol, 12mg, 5mol%), 2-(4-cyanophenoxy)-1-(4-methoxyphenyl)ethanone (0.2mmol, 53.4mg, 1.0equiv.) to a dry Schlenk reaction tube, replace argon three times, and then dropwise add diisopropylethylamine (0.5mmol, 65mg, 2.5equiv.), HCOOH (0.02mmol, 81mg, 0.1equiv.) and tetrahydrofuran (4mL). Place the reaction tube 3 cm away from a 15W blue LED light source and react at 30°C for 16 hours. After the reaction is completed, the solvent is removed by rotary evaporation, and the corresponding products, hawthorn flower ketone and p-cyanophenol, are purified by column chromatography (eluent PE / EA=20:1-10:1). The substances are all white crystals, with yields of 21mg and 16.2mg, respectively, and yields of 70% and 68%, respectively.

[0127] Characterization data: Hawthorne flower ketone 1 H NMR (400MHz, CDCl3) δ7.94 (d, J = 8.8 Hz, 2H), 6.93 (d, J = 8.8 Hz, 2H), 3.87 (s, 3H), 2.55 (s, 3H). 13 C NMR (101MHz, CDCl3) δ196.83, 163.52, 130.61 (2C), 130.42, 113.71 (2C), 55.53, 26.42. p-Cyanophenol 1 H NMR (400MHz, CDCl3) δ7.55 (d, J = 8.4Hz, 2H), 6.95 (d, J = 8.4Hz, 2H), 6.84 (br, s, 1H). 13 C NMR (101MHz, CDCl3) δ160.4, 134.5, 119.4, 116.6, 103.0.

Claims

1. A method for catalytic cracking of β-O-4 type lignin model compounds using visible light, characterized in that: The method comprises: Under an inert atmosphere, a photosensitizer, a β-O-4 type lignin model compound shown in formula I, a protonic acid, an amine and a solvent are mixed, and reacted under visible light irradiation and 25 to 45° C. for 6 to 48 hours, and then the reaction solution is post-treated to obtain an aromatic ketone compound shown in formula II and a phenolic compound shown in formula III, respectively; in, The photosensitizer is selected from at least one of copper-based photosensitizer PS1, copper-based photosensitizer PS2, copper-based photosensitizer PS3, copper-based photosensitizer PS4, copper-based photosensitizer PS5, and organic photosensitizer PS6; the structural formula of the photosensitizer is as follows: The protic acid is selected from hydrochloric acid, nitric acid, formic acid or acetic acid; The amine is selected from triethylamine, tetramethylethylenediamine or diisopropylethylamine; The reaction formula is as follows: In Formula I to Formula III, R 1 is H, 4-methoxy, 3,4-dimethoxy or 3,4,5-trimethoxy; R 2 is H, 2-methoxy, 3-methoxy, 4-methoxy, chloro, bromo, phenyl, cyclohexyl, 3,5-dimethyl, 3,5-dimethoxy, 2,6-dimethoxy, acetyl, tert-butyl, cyano or nitro.

2. The method for catalytic cracking of β-O-4 type lignin model compound by visible light according to claim 1, characterized in that: The molar ratio of the beta-O-4 type lignin model compound shown in formula I, amine, protonic acid and photosensitizer is 1:1.5-3:0.01-0.15:0.02-0.

1.

3. The method for catalytic cracking of β-O-4 type lignin model compound by visible light according to claim 1, characterized in that: The photosensitizer is copper-based photosensitizer PS2.

4. The method for catalytic cracking of β-O-4 type lignin model compound by visible light according to claim 1, characterized in that: The protic acid is formic acid.

5. The method for catalytic cracking of β-O-4 type lignin model compound by visible light according to claim 1, characterized in that: The amine was diisopropylethylamine.

6. The method for catalytic cracking of β-O-4 type lignin model compound under visible light as claimed in claim 1, characterized in that: The solvent is selected from toluene, acetonitrile, diethyl ether, dichloromethane, ethyl acetate, dimethyl sulfoxide, 1,2-dichloroethane, 1,4-dioxane, methanol, ethanol or tetrahydrofuran.

7. The method for catalytic cracking of β-O-4 type lignin model compound by visible light according to claim 1, characterized in that: The volume molar ratio of the solvent to the beta-O-4 type lignin model compound shown in formula I is 10-25:1, mL / mmol.

8. The method for catalytic cracking of β-O-4 type lignin model compound under visible light as claimed in claim 1, characterized in that: The visible light source uses blue LED.

9. The method for catalytic cracking of β-O-4 type lignin model compound by visible light according to claim 1, characterized in that: The post-treatment method is as follows: after the reaction is completed, 100-200 mesh column chromatography silica gel is added to the reaction solution and the solvent is removed by distillation under reduced pressure, the crude product is dry-loaded for column chromatography separation, and gradient elution is performed using petroleum ether / ethyl acetate volume ratio = 20-10:1 as an eluent, and the target compound eluate is obtained by TLC detection, and evaporated to dryness under reduced pressure to obtain the aromatic ketone compound shown in formula II and the phenol compound shown in formula III, respectively.

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