A method for catalytic hydrogenation cracking of carbamate compounds and a method for preparing a ruthenium catalyst with a phosphine-tridentate ligand.

Abstract

This invention provides a method for catalytic hydrogenation cracking of carbamate compounds and a method for preparing a ruthenium-nitrogen tridentate ligand catalyst. The catalytic hydrogenation cracking method uses a ruthenium-nitrogen tridentate ligand catalyst as the catalyst. In a reaction system containing an organic base and toluene, carbamate compounds undergo hydrogenation cracking under a hydrogen atmosphere to produce amines and alcohols. The preparation method includes three steps: preparing a diphenylphosphino-acetaldehyde hydrobromide dimer, preparing the phosphino-nitrogen ligand, and preparing the ruthenium-nitrogen tridentate ligand catalyst. This invention uses hydrogen as a green reducing agent to crack carbamate compounds into high-value alcohols and amines. The ruthenium catalyst used exhibits highly efficient catalytic activity in the hydrogenation cleavage of amide bonds. This method has high catalytic efficiency and broad substrate applicability.

Description

Technical Field

[0001] This invention belongs to the field of organic synthesis technology and relates to catalysts for hydrogenation cracking, specifically to a method for catalyzing the hydrogenation cracking of carbamate compounds and a method for preparing a ruthenium catalyst with a phosphine tridentate ligand. Background Technology

[0002] The reduction of carboxylic acids and their derivatives plays a crucial role in scientific research and industrial applications. Traditional reduction methods often require stoichiometric amounts of hydrogenating reagents (e.g., lithium aluminum hydride, sodium borohydride, borane, etc.), producing equimolar amounts of hydrogenation byproducts. Hydrogen, as a green reducing agent, is widely used in the catalytic hydrogenation reactions of unsaturated carbon-carbon, carbon-oxygen, and carbon-nitrogen functional groups due to its high atom economy and low waste. However, hydrogenating carboxylic acids and their derivatives under mild conditions using hydrogen is quite challenging, especially for urethanes, which are among the most difficult carbonyl compounds to reduce. This is fundamentally because the carbonyl group in urethanes is conjugated with both oxygen and nitrogen atoms, resulting in a much lower hydrogenation reactivity of the carbon-oxygen double bond compared to ordinary carbonyl compounds.

[0003] Successful case studies of catalytic hydrogenation of carbamates are reported below: D. Milstein achieved the catalytic hydrogenation of carbamates using a bipyridine-type phosphine-tridentate ligand-ruthenium catalytic system, yielding important chemical raw materials such as alcohols and amines. However, the substrate applicability is relatively narrow, and the use of tetrahydrofuran solvent at 110°C poses safety risks. M. Ito used Cp... The -Ru catalytic system achieved the catalytic hydrogenation of specific cyclic carbamates to obtain chiral alcohols as raw materials, but its catalytic system has poor universality. T. Werner used bis(diphenylphosphine) to replace the diethylamine-manganese catalytic system, with isopropanol as the hydrogen source, and achieved the catalytic hydrogenation of carbamates through transfer hydrogenation. This catalytic system has a wide range of substrate applicability, but its catalytic efficiency is low, and the catalyst is highly sensitive to water and oxygen, making it difficult to scale up. Summary of the Invention

[0004] In view of the defects and deficiencies of the existing technology, the purpose of this invention is to provide a method for catalytic hydrogenation cracking of carbamate compounds and a method for preparing a ruthenium phosphine tridentate ligand catalyst, thereby solving the technical problems of low catalytic efficiency and poor substrate applicability of hydrogenation cracking of carbamate compounds in the existing technology.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A method for catalytic hydrogenation cracking of carbamate compounds, comprising a nitrophosphine tridentate ruthenium catalyst as a catalyst, wherein the carbamate compounds are catalyzed for hydrogenation cracking in a reaction system containing an organic base and toluene under a hydrogen atmosphere to produce amines and alcohols; the chemical structural formula of the nitrophosphine tridentate ruthenium catalyst is shown in Formula I below:

[0007] Formula I;

[0008] In Formula I:

[0009] R1 is selected from methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, and phenyl;

[0010] R2 is selected from hydrogen, alkoxy, alkyl, and dimethylamino;

[0011] The chemical structural formulas of the carbamate compounds are shown in Formula II and Formula III below:

[0012] Formula II;

[0013] In Formula II:

[0014] R3 is selected from methyl, ethyl, isopropyl, n-butyl, phenyl, and benzyl;

[0015] R4 is selected from phenyl, substituted phenyl, 2-pyridyl, 1-naphthyl, α-methylbenzyl, benzyl, n-hexyl, indole, piperidine, and morpholine;

[0016] R5 is selected from hydrogen, methyl, and phenyl;

[0017] Formula III;

[0018] In Formula III:

[0019] n is a positive integer greater than or equal to 26 and less than or equal to 32;

[0020] The preparation method of the nitrogen-phosphine tridentate ruthenium ligand catalyst specifically includes the following steps:

[0021] Step 1: Preparation of diphenylphosphine-acetaldehyde hydrobromide dimer:

[0022] Organophosphate salts were dissolved in a solvent to prepare an organophosphate salt solution. The organophosphate salt solution was added to a reaction vessel, and 2-bromoacetaldehyde diethyl acetal was added dropwise while stirring at -30°C. After the addition was complete, the system was allowed to naturally heat up to 20-30°C, and then hydrobromic acid aqueous solution was added. The mixture was stirred at 40°C for 6-8 hours. After the reaction solution cooled down, the solvent was first distilled off, and then the mixture was filtered to obtain a filter cake. The filter cake was washed, the solvent was removed, and then dried to obtain diphenylphosphine-acetaldehyde hydrobromide dimer.

[0023] The chemical structural formula of the organophosphate salt is shown in Formula IV below:

[0024] Formula IV;

[0025] In Formula IV:

[0026] M is selected from the ions corresponding to hydrogen and alkali metal elements;

[0027] R1 is selected from methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, or phenyl;

[0028] Step 2, Preparation of nitrogen-phosphine ligands:

[0029] The diphenylphosphino-acetaldehyde hydrobromide dimer, aminoquinoline compounds, sodium triacetoxyborohydride, and solvent prepared in step one were added to a reaction vessel and stirred at 20–30°C for 8–12 hours under a nitrogen atmosphere. After the reaction was completed, a saturated ammonium chloride aqueous solution was added to the reaction solution to quench the reaction. The product was then extracted with ethyl acetate, and the organic phase obtained by extraction was back-extracted with saturated brine. Finally, the product was dried, the organic phase was concentrated, and purified by column chromatography to obtain the nitrogen phosphine ligand.

[0030] The chemical structural formula of the aminoquinoline compounds is shown in Formula V below:

[0031] Formula V;

[0032] In formula V:

[0033] R2 is selected from hydrogen, alkoxy, alkyl, and dimethylamino;

[0034] Step 3: Preparation of ruthenium catalyst with phosphine tridentate ligand:

[0035] The nitrogen-phosphine ligand, tris(triphenylphosphine)carbonyl ruthenium chloride and solvent prepared in step 2 were added to the reaction vessel and stirred at 110°C for 9 to 12 hours under a nitrogen protective atmosphere. After the reaction was completed, the reaction solution was filtered to obtain a filter cake. After rinsing and drying, the nitrogen-phosphine tridentate ruthenium catalyst was obtained.

[0036] The present invention also has the following technical features:

[0037] Specifically, the hydrogenation cracking reaction conditions are: hydrogen pressure of 20-30 bar, reaction temperature of 110-130°C, and reaction time of 2-6 hours.

[0038] Specifically, the carbamate compound is methyl N-phenylcarbamate; the mass ratio of methyl N-phenylcarbamate to ruthenium tridentate ligand catalyst is (80-120):(5-7).

[0039] Specifically, the carbamate compound is polyurethane; the mass ratio of the polyurethane to the nitrophosphine tridentate ruthenium catalyst is (300-500):(5-15).

[0040] Specifically, the organic base mentioned is potassium tert-butoxide.

[0041] Specifically, in step one, the molar ratio of 2-bromoacetal diethyl acetal, organophosphate salt and hydrobromic acid is 1:(1-2):(1.5-3).

[0042] Specifically, in step two, the molar ratio of diphenylphosphine-acetaldehyde hydrobromide dimer, aminoquinoline compounds and sodium triacetoxyborohydride is 1:(1-2):(2-4).

[0043] Specifically, in step three, the molar ratio of the nitrogen phosphine ligand and tris(triphenylphosphine)carbonyl ruthenium chloride is (1-1.5):1.

[0044] Specifically, the solvent is selected from tetrahydrofuran, toluene, 2-methyltetrahydrofuran, ethyl acetate, dichloromethane, chloroform, and methanol.

[0045] The present invention also protects the preparation method of the nitrogen-phosphine tridentate ruthenium catalyst as described above.

[0046] The beneficial technical effects of this invention compared to the prior art are as follows:

[0047] (I) The method for catalytic hydrogenation cracking of carbamate compounds of the present invention uses hydrogen as a green reducing agent to crack carbamate compounds into high-value-added alcohols and amines. The ruthenium catalyst used exhibits highly efficient catalytic activity in the hydrogenation cleavage of amide bonds. The reaction conditions of this method are mild, with good selectivity and high yield, i.e., it has high catalytic efficiency. In addition, this method is applicable to both non-polymer and polymer carbamate compounds, i.e., it has broad substrate applicability.

[0048] (II) The method for preparing the ruthenium catalyst with phosphine tridentate ligand of the present invention uses an aminoquinoline compound as the ligand skeleton, introduces phosphine structural units through a reduction amination reaction to synthesize phosphine tridentate ligand, and then uses the phosphine tridentate ligand and metal ruthenium salt to complex a novel ruthenium catalyst. The ruthenium catalyst has strong structural rigidity, coordination ability and catalytic efficiency.

[0049] The technical solution of the present invention will be further described below with reference to the embodiments. Detailed Implementation

[0050] In this invention:

[0051] Carbamates are compounds that contain carbamate groups, including polymers with carbamate groups in their main chain, such as polyurethane.

[0052] The synthetic route for the ruthenium catalyst of this invention is as follows:

[0053] ;

[0054] in:

[0055] M is hydrogen or an alkali metal element;

[0056] R1 is methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, or phenyl.

[0057] R2 can be hydrogen, alkoxy, alkyl, or dimethylamino.

[0058] The hydrogenation cracking reaction of non-polymer carbamate compounds catalyzed by a ruthenium catalyst in this invention is shown below:

[0059] ;

[0060] in:

[0061] R3 can be methyl, ethyl, isopropyl, n-butyl, phenyl, or benzyl.

[0062] R4 is phenyl, substituted phenyl, 2-pyridyl, 1-naphthyl, α-methylbenzyl, benzyl, n-hexyl, indole, piperidine, or morpholine;

[0063] R5 represents hydrogen, methyl, or phenyl.

[0064] The hydrogenation and cracking reaction of polyurethane catalyzed by a ruthenium catalyst in this invention is shown below:

[0065] ;

[0066] Where: n = 26~32.

[0067] It should be noted that, unless otherwise specified, all raw materials and reagents used in this invention are those known in the art.

[0068] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0069] Example 1:

[0070] This embodiment provides a method for preparing a diphenylphosphine-acetaldehyde hydrobromide dimer (2)-1. The method specifically includes the following steps: potassium diphenylphosphine is dissolved in tetrahydrofuran to prepare an organophosphate solution (0.5M); 34 mL of the organophosphate solution is added to a dry three-necked flask equipped with a constant pressure dropping funnel and a thermometer, and then 3.4 g of 2-bromoacetaldehyde diethyl acetal is added dropwise while stirring at -30°C. After the addition is completed, the system is allowed to return to room temperature naturally. Then, 6.8 mL of 10 wt.% hydrobromic acid aqueous solution is added, and the mixture is stirred at 40°C for 8 hours. After the above reaction solution is cooled to room temperature, half of the solvent is distilled off, filtered, and the filter cake is washed sequentially with 10 mL of water and 10 mL of ethyl acetate. The solvent is then removed, and the product is dried under vacuum to obtain 10 g of white solid product.

[0071] In this embodiment, the white solid product was identified, and its characterization data are as follows:

[0072] 1 H NMR (500MHz, d) 6 -DMSO): δppm7.32-7.41 (m, 20H), 5.21(dd, 1H), 5.08(dd, 1H), 2.76 (m, 2H), 2.98 (m, 2H).

[0073] 31 P {H} NMR (202 MHz, d 6 -DMSO): δppm 21.1 (s), 30.4 (s).

[0074] As can be seen from the above structural characterization data, the white solid product obtained in this embodiment is diphenylphosphino-acetaldehyde hydrobromide dimer (2)-1. In this embodiment, the yield of diphenylphosphino-acetaldehyde hydrobromide dimer (2)-1 is 94.3%. It should be noted that the NMR signal of this product is relatively weak and difficult to detect.

[0075] The reaction route in this embodiment is as follows:

[0076] ;

[0077] in:

[0078] This indicates 2-bromoacetal diethyl acetal;

[0079] This represents potassium diphenylphosphine;

[0080] HBr represents hydrobromic acid;

[0081] It represents the diphenylphosphine-acetaldehyde hydrobromide dimer (2)-1.

[0082] Example 2:

[0083] This embodiment provides a method for preparing a dicyclohexylphosphine-acetaldehyde hydrobromide dimer (2)-2. The method specifically includes the following steps: dissolving dicyclohexylphosphine potassium in tetrahydrofuran to prepare an organophosphate salt solution (0.5M); adding 19 mL of the organophosphate salt solution to a dry three-necked flask equipped with a constant pressure dropping funnel and a thermometer, and then adding 1.7 g of 2-bromoacetaldehyde diethyl acetal dropwise while stirring at -30℃. After the addition is completed, the system is allowed to return to room temperature naturally. Then, 3.4 mL of 10 wt.% hydrobromic acid aqueous solution is added, and the mixture is stirred at 40℃ for 6 hours. After the above reaction solution is cooled to room temperature, half of the solvent is distilled off, filtered, and the filter cake is washed sequentially with 10 mL of water and 10 mL of ethyl acetate. The solvent is then removed, and the product is dried under vacuum to obtain 4.7 g of white solid product.

[0084] In this embodiment, the white solid product was identified, and its characterization data are as follows:

[0085] 1 H NMR (500MHz, CD3CN): δppm1.42-2.19 (m, 44H), 2.80 (q, 2H), 3.08 (m, 2H), 5.39 (dd, 1H), 5.23 (dd, 1H).

[0086] 31 P{H} NMR (202 MHz, CD3CN): δppm 27.2 (s), 28.1 (s).

[0087] Based on the structural characterization data above, the white solid product obtained in this embodiment is diphenylphosphino-acetaldehyde hydrobromide dimer (2)-2. In this embodiment, the yield of diphenylphosphino-acetaldehyde hydrobromide dimer (2)-2 is 84%. It should be noted that the NMR signal of this product is relatively weak and difficult to detect.

[0088] The reaction route in this embodiment is as follows:

[0089] ;

[0090] in:

[0091] This indicates dicyclohexylphosphine potassium;

[0092] It represents the dicyclohexylphosphine-acetaldehyde hydrobromide dimer (2)-2.

[0093] Example 3:

[0094] This embodiment provides a method for preparing a nitrogen phosphine ligand (3)-1. The method specifically includes the following steps: 618 mg of diphenylphosphino-acetaldehyde hydrobromide dimer (2)-1, 288 mg of 8-aminoquinoline, 848 mg of sodium triacetoxyborohydride and 15 mL of tetrahydrofuran are added to a dry Shrek tube and stirred at room temperature (20-30°C) for 12 hours under a nitrogen atmosphere. Then, 10 mL of saturated ammonium chloride aqueous solution is added to the above reaction solution under a nitrogen atmosphere to quench the reaction. The mixture is stirred for 10 minutes, extracted with 20 mL of ethyl acetate, back-extracted with 20 mL of saturated brine, dried with anhydrous sodium sulfate for 30 minutes, concentrated, and finally purified by rapid column chromatography under an inert gas atmosphere to obtain 592 mg of colorless liquid product.

[0095] In this embodiment, the colorless liquid product was identified, and its NMR data are as follows:

[0096] 1 H NMR (500MHz, CDCl3): δppm 8.67 (d, 1H), 8.00 (d, 1H), 7.46 (m, 4H), 7.32 (m, 6H), 7.01 (d, 4H), 6.51 (d, 1H), 6.31 (s, 1H), 3.45 (m, 2H), 2.60-2.46(m,2H);

[0097] 13 C NMR (125MHz, CDCl3): δppm 146.82, 144.25, 138.17, 135.95, 132.86, 132.71, 128.76, 128.67, 128.57, 128.52, 128.05, 127.72, 121.37, 113.93,104.66, 40.51, 40.32, 28.38, 28.28;

[0098] 31 P NMR (202MHz, CDCl3): δppm -21.09.

[0099] Based on the above structural characterization data, the colorless liquid product obtained in this embodiment is phosphine ligand (3)-1. In this embodiment, the yield of phosphine ligand (3)-1 is 83%, and the content is 95%.

[0100] The reaction route in this embodiment is as follows:

[0101] ;

[0102] in:

[0103] It represents 8-aminoquinoline;

[0104] This indicates sodium triacetoxyborohydride;

[0105] THF stands for tetrahydrofuran;

[0106] This indicates the nitrogen phosphine ligand (3)-1.

[0107] Example 4:

[0108] This embodiment provides a method for preparing a nitrogen phosphine ligand (3)-2. The method specifically includes the following steps: 220 mg of dicyclohexylphosphino-acetaldehyde hydrobromide dimer (2)-2, 96 mg of 8-aminoquinoline, 283 mg of sodium triacetoxyborohydride and 8 mL of tetrahydrofuran are added to a dry Shrek tube and stirred at room temperature for 8 hours under a nitrogen atmosphere. Then, 5 mL of saturated ammonium chloride aqueous solution is added to the above reaction solution under a nitrogen atmosphere to quench the reaction, and the mixture is stirred for 10 minutes. 10 mL of ethyl acetate is added for extraction, and the organic phase is back-extracted with 10 mL of saturated brine. The organic phase is dried with anhydrous sodium sulfate for 20 minutes, and the organic phase is concentrated. Finally, the product is purified by rapid column chromatography under an inert gas atmosphere to obtain 196 mg of colorless liquid product.

[0109] In this embodiment, the colorless liquid product was identified, and its characterization data are as follows:

[0110] 1 H NMR (500 MHz, CDCl3) δppm: 1.17–1.30(m, 10H), 1.57–1.62(m, 2H), 1.69–1.79(m, 10H), 1.85–1.89(m, 2H), 3.41–3.46(m, 2H), 6.30(s, 1H), 6.66–6.67(dd, 1H), 7.02–7.05(m, 1H), 7.34–7.40(m, 2H), 8.03–8.05 (dd, 1H), 8.70–8.71(dd, 1H).

[0111] 13 C NMR (126 MHz, CDCl3) δppm: 21.83, 27.36, 27.46, 29.07, 30.41,33.37, 43.23, 104.84, 113.88, 121.46, 127.92, 128.79, 136.08, 138.31, 144.58,146.92.

[0112] 31 P{1H} NMR (202 MHz, CDCl3) δppm: –8.61.

[0113] Based on the structural characterization data above, the colorless liquid product obtained in this embodiment is phosphine ligand (3)-2. In this embodiment, the yield of phosphine ligand (3)-2 is 80%, and the content is 95%.

[0114] The reaction route in this embodiment is as follows:

[0115] ;

[0116] in:

[0117] This indicates the nitrogen phosphine ligand (3)-2.

[0118] Example 5:

[0119] This embodiment provides a method for preparing a nitrogen phosphine ligand (3)-3. The method specifically includes the following steps: 309 mg of diphenylphosphino-acetaldehyde hydrobromide dimer (2)-1, 174 mg of 4-methoxy-8-aminoquinoline, 424 mg of sodium triacetoxyborohydride and 10 mL of tetrahydrofuran are added to a dry Shrek tube and stirred at room temperature for 10 hours under a nitrogen atmosphere. Then, under a nitrogen atmosphere, 10 mL of saturated ammonium chloride aqueous solution is added to the above reaction solution to quench the reaction, and the mixture is stirred for 10 minutes. 10 mL of ethyl acetate is added for extraction, and the organic phase is back-extracted with 10 mL of saturated brine. The organic phase is dried with anhydrous sodium sulfate for 20 minutes, the organic phase is concentrated, and finally purified by rapid column chromatography under an inert gas atmosphere to obtain 340 mg of colorless liquid product.

[0120] In this embodiment, the colorless liquid product was identified, and its characterization data are as follows:

[0121] 1 H NMR (500MHz, CDCl3): δppm 8.96 (d, 1H), 7.81 (d, 1H), 7.65 (d, 1H), 7.47 (d, 1H), 7.42 (m, 6H), 7.33 (m, 1H), 7.15 (d, 4H), 6.52 (s, 1H), 3.81 (s, 3H), 3.43 (m, 2H), 2.62-2.48 (m, 2H);

[0122] 13C NMR (125MHz, CDCl3): δppm 166.31, 151.26, 143.11, 138.92, 137.88, 132.71, 128.76, 128.67, 128.57, 128.52, 128.05, 127.72, 120.41, 113.93,104.66, 56.7, 42.53, 42.36, 29.57, 29.39;

[0123] 31 P NMR (202MHz, CDCl3): δppm -22.18.

[0124] Based on the above structural characterization data, the colorless liquid product obtained in this embodiment is phosphine ligand (3)-3. In this embodiment, the yield of phosphine ligand (3)-3 is 88%, and the content is 96%.

[0125] The reaction route in this embodiment is as follows:

[0126] ;

[0127] in:

[0128] It represents 4-methoxy-8-aminoquinoline;

[0129] It represents the nitrogen phosphine ligand (3)-3.

[0130] Example 6:

[0131] This embodiment provides a method for preparing a nitrophosphine tridentate ruthenium catalyst (1)-1. The method specifically includes the following steps: 392 mg of nitrophosphine ligand (3)-1, 490 mg of tris(triphenylphosphine)carbonyl ruthenium chloride and 5 mL of toluene are added to a dry Shrek tube and heated and stirred at 110 °C for 12 hours under a nitrogen atmosphere. The reaction solution is then filtered under a nitrogen atmosphere, and the filter cake is washed sequentially with 5 mL of toluene and 5 mL of diethyl ether. The resulting solid is then quickly transferred to a round-bottom flask and dried under vacuum to obtain 444 mg of a deep yellow solid product.

[0132] In this embodiment, the deep yellow solid product was identified, and its characterization data are as follows:

[0133] 1 H NMR (500MHz, DMSO-) d6): δppm 9.71 (s, 1H), 8.72 (dd, 2H), 8.38 (d, 1H), 8.21 (d, 1H), 7.98 (t, 3H), 7.66 (d, 3H), 7.55-7.38 (m, 2H), 7.28 (t, 2H), 6.91 (t, 2H), 4.14 (m, 1H), 3.25 (m, 2H), 1.86-1.58 (m, 1H), -14.3 (s, 1H);

[0134] 13 C NMR (125MHz, DMSO-) d 6): δppm 156.68, 146.26, 142.68, 139.32, 132.86,132.71, 131.76, 131.67, 131.57, 130.52, 130.35, 130.12, 129.97, 129.83,129.56, 129.42, 129.21, 128.83, 128.16, 124.51, 57.38, 57.08;

[0135] 31 P NMR (202MHz, DMSO-) d 6): δppm 9.31.

[0136] Based on the above structural characterization data, the deep yellow solid product obtained in this embodiment is ruthenium catalyst (1)-1. In this embodiment, the yield of ruthenium catalyst (1)-1 is 85%, and the content is 97%.

[0137] The reaction route in this embodiment is as follows:

[0138] ;

[0139] This indicates tris(triphenylphosphine)carbonyl ruthenium chloride;

[0140] TOL stands for toluene;

[0141] This indicates a ruthenium catalyst (1)-1.

[0142] Example 7:

[0143] This embodiment provides a method for preparing a nitrophosphine tridentate ruthenium catalyst (1)-2. The method specifically includes the following steps: 135 mg of nitrophosphine ligand (3)-2, 163 mg of tris(triphenylphosphine)carbonyl ruthenium chloride and 2 mL of toluene are added to a dry Shrek tube and heated and stirred at 110 °C for 9 hours under a nitrogen atmosphere; the reaction solution is then filtered under a nitrogen atmosphere, and the filter cake is washed sequentially with 5 mL of toluene and 5 mL of diethyl ether. The resulting solid is then quickly transferred to a round-bottom flask and dried under vacuum to obtain 145 mg of a deep yellow solid product.

[0144] In this embodiment, the deep yellow solid product was identified, and its characterization data are as follows:

[0145] 1 H NMR (500MHz, DMSO-) d 6): δppm 9.62 (d, 1H), 9.14 (d, 1H), 8.28 (m, 1H), 8.21 (d, 1H), 7.78 (d, 1H), 7.68-7.62 (m, 1H), 7.02 (s, 1H), 4.44-4.32 (m, 1H), 3.28-3.15(m, 2H), 1.96–1.91(m, 2H), 1.82–1.73(m, 11H), 1.44–1.26(m, 10H), -10.6(s, 1H);

[0146] 31 P NMR (202MHz, DMSO-) d 6): δppm 27.46.

[0147] Based on the above structural characterization data, the deep yellow solid product obtained in this embodiment is ruthenium catalyst (1)-2. In this embodiment, the yield of ruthenium catalyst (1)-2 is 82%, and the content is 96%. It should be noted that the NMR signal of this product is relatively weak and difficult to detect.

[0148] The reaction route in this embodiment is as follows:

[0149] ;

[0150] This indicates a ruthenium catalyst (1)-2.

[0151] Example 8:

[0152] This embodiment provides a method for preparing a nitrophosphine tridentate ruthenium catalyst (1)-3. The method specifically includes the following steps: 212 mg of nitrophosphine ligand (3)-3, 245 mg of tris(triphenylphosphine)carbonyl ruthenium chloride and 3 mL of toluene are added to a dry Shrek tube and heated and stirred at 110 °C for 10 hours under a nitrogen atmosphere; the reaction solution is then filtered under a nitrogen atmosphere, and the filter cake is washed sequentially with 5 mL of toluene and 5 mL of diethyl ether. The resulting solid is then quickly transferred to a round-bottom flask and dried under vacuum to obtain 237 mg of yellow solid product.

[0153] In this embodiment, the yellow solid product was identified, and its characterization data are as follows:

[0154] 1 H NMR (500MHz, DMSO-) d 6): δppm 9.98 (s, 1H), 8.43 (d, 1H), 8.28 (d, 1H), 8.01 (d, 1H), 7.79-7.71 (m, 4H), 7.68-7.55 (m, 4H), 7.50-7.41 (d, 2H), 7.28-7.21(d,2H), 4.11-4.05(m,1H), 3.82(s,3H), 3.26-3.13(m,2H), 1.83-1.62(m,1H), -14.3(s,1H);

[0155] 31 P NMR (202MHz, DMSO-) d 6): δppm 9.18.

[0156] Based on the above structural characterization data, the yellow solid product obtained in this embodiment is ruthenium catalyst (1)-3. In this embodiment, the yield of ruthenium catalyst (1)-3 is 86%, and the content is 96%. It should be noted that the NMR signal of this product is relatively weak and difficult to detect.

[0157] The reaction route in this embodiment is as follows:

[0158] ;

[0159] This indicates a ruthenium catalyst (1)-3.

[0160] Example 9:

[0161] This embodiment provides a method for the hydrogenation cracking of N-phenylcarbamate using a ruthenium catalyst. The method specifically includes the following steps: 1.1 g of N-phenylcarbamate, 63 mg of the ruthenium catalyst (I)-1 prepared in Example 6, 27 mg of potassium tert-butoxide, and 2 mL of toluene are added to a pressure vessel. The pressure vessel is closed, and the system is first replaced with a nitrogen atmosphere three times, and then replaced with a hydrogen atmosphere three times. The hydrogen pressure of the system is controlled at 20 bar, and the mixture is stirred at 110°C for 2 hours. The system is then cooled to room temperature, and the pressure is slowly released in a fume hood. After the system pressure drops to one atmosphere, the pressure vessel is opened to obtain the product.

[0162] In this embodiment, GC-MS analysis revealed that the products were aniline and methanol. After column chromatography purification, the purified products were further identified by NMR, with the following results:

[0163] 1 H NMR (500MHz, CDCl3): δppm 7.15-7.26 (m, 2H), 6.71-6.83 (m, 3H), 3.8 (s, 2H);

[0164] 13 C NMR (125MHz, CDCl3): δppm 146.48, 129.21, 118.33, 115.08.

[0165] As can be seen from the above structural characterization data, one of the products obtained in this embodiment is indeed aniline, and based on the principles of chemical reaction, the other product can be determined to be methanol. In this embodiment, the yield of aniline is 91%.

[0166] The reaction route in this embodiment is as follows:

[0167] ;

[0168] in:

[0169] It represents methyl N-phenylcarbamate;

[0170] KO t Bu represents potassium tert-butoxide;

[0171] It represents aniline;

[0172] CH3OH represents methanol.

[0173] Example 10:

[0174] This embodiment provides a method for hydrogenation cracking of N-phenylcarbamate using a ruthenium catalyst. This method is basically the same as that in Example 9, except that the ruthenium catalyst is the ruthenium catalyst (1)-2 prepared in Example 7.

[0175] In this embodiment, GC-MS analysis revealed that the products were aniline and methanol. The yield of aniline in this embodiment was 89%.

[0176] Example 11:

[0177] This embodiment provides a method for hydrogenation cracking of N-phenylcarbamate using a ruthenium catalyst. This method is basically the same as that in Example 9, except that the ruthenium catalyst is the ruthenium catalyst (1)-3 prepared in Example 8.

[0178] In this embodiment, GC-MS analysis revealed that the products were aniline and methanol. The yield of aniline in this embodiment was 94%.

[0179] Example 12:

[0180] This embodiment provides a method for catalyzing the hydrogenation cracking of polyurethane using ruthenium catalyst (1)-3 prepared in Example 8. The method specifically includes the following steps: 414 mg of polyurethane (weight average molecular weight of 11000), 10 mg of ruthenium catalyst (I)-3 prepared in Example 8, 4.5 mg of potassium tert-butoxide, and 1 mL of toluene are added to a pressure vessel. The pressure vessel is then closed, and the system is first replaced with a nitrogen atmosphere three times, and then replaced with a hydrogen atmosphere three times. The hydrogen pressure of the system is controlled at 30 bar, and the system is stirred at 130°C for 6 hours. The system is then cooled to room temperature, and the pressure is slowly released in a fume hood. After the system pressure drops to one atmosphere, the pressure vessel is opened to obtain the product.

[0181] In this embodiment, GC-MS analysis revealed that the products were 4,4'-methylenediphenylamine and 1,5-pentanediol. After column chromatography purification, the purified products were further identified by NMR, with the following results:

[0182] 1 H NMR (500MHz, CDCl3): δppm 7.05-6.93 (m, 4H), 6.69-6.58 (m, 4H), 3.80 (s, 2H), 3.48 (brs, 4H);

[0183] 13 C NMR (125MHz, CDCl3): δppm 144.56, 132.18, 129.75, 115.43, 40.33.

[0184] Based on the above structural characterization data, it can be seen that one of the products obtained in this embodiment is indeed 4,4'-methylenediphenylamine, and based on the principle of chemical reaction, the other product can be determined to be 1,5-pentanediol.

[0185] In this embodiment, the yield of the product 4,4'-methylenediphenylamine was 51%; after rapid column chromatography purification and separation, the yield of 4,4'-methylenediphenylamine was 45%.

[0186] The reaction route in this embodiment is as follows:

[0187] ;

[0188] in:

[0189] Indicates polyurethane;

[0190] This represents 4,4'-diaminodiphenylmethane;

[0191] It represents pentanediol.

Claims

1. A method for catalytic hydrogenation cracking of carbamate compounds, characterized in that, This method uses a nitrophosphine-tridentate ruthenium catalyst as a catalyst to catalyze the hydrogenation and cracking of carbamate compounds in a reaction system containing organic bases and toluene under a hydrogen atmosphere, producing amines and alcohols; The chemical structural formulas of the carbamate compounds are shown in Formula II or Formula III below: Formula II; In Formula II: R3 is selected from methyl, ethyl, isopropyl, n-butyl, phenyl, and benzyl; R4 is selected from phenyl, 2-pyridyl, 1-naphthyl, α-methylbenzyl, benzyl, n-hexyl, indole, piperidine, and morpholine; R5 is selected from hydrogen, methyl, and phenyl; Formula III; In Formula III: n is a positive integer greater than or equal to 26 and less than or equal to 32; The hydrogenation cracking reaction conditions are as follows: hydrogen pressure of 20-30 bar, reaction temperature of 110-130°C, and reaction time of 2-6 hours. The mass ratio of the carbamate compound to the nitrophosphine tridentate ruthenium catalyst is (300-500):(5-15); The preparation method of the nitrogen-phosphine tridentate ruthenium ligand catalyst specifically includes the following steps: Step 1: Preparation of disubstituted phosphine-acetaldehyde hydrobromide dimer: Organophosphate salts were dissolved in a solvent to prepare an organophosphate salt solution. The organophosphate salt solution was added to a reaction vessel, and 2-bromoacetaldehyde diethyl acetal was added dropwise while stirring at -30°C. After the addition was completed, the system was allowed to naturally heat up to 20-30°C, and then hydrobromic acid aqueous solution was added. The mixture was stirred at 40°C for 6-8 hours. After the reaction solution cooled down, the solvent was first distilled off, and then the mixture was filtered to obtain a filter cake. The filter cake was washed, the solvent was removed, and then dried to obtain a disubstituted phosphine-acetaldehyde hydrobromide dimer. The chemical structural formula of the organophosphate salt is shown in Formula IV below: Formula IV; In Formula IV: M is selected from the ions corresponding to hydrogen and alkali metal elements; R1 is selected from methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, and phenyl; Step 2, Preparation of nitrogen-phosphine ligands: The disubstituted phosphino-acetaldehyde hydrobromide dimer obtained in step one, aminoquinoline compounds, sodium triacetoxyborohydride, and solvent were added to the reaction vessel and stirred at 20–30°C for 8–12 hours under a nitrogen atmosphere. After the reaction was completed, a saturated ammonium chloride aqueous solution was added to the reaction solution to quench the reaction. The product was then extracted with ethyl acetate, and the organic phase obtained by extraction was back-extracted with saturated brine. Finally, the product was dried, the organic phase was concentrated, and purified by column chromatography to obtain the nitrogen phosphine ligand. The chemical structural formula of the aminoquinoline compounds is shown in Formula V below: Formula V; In formula V: R2 is selected from hydrogen, alkoxy, alkyl, and dimethylamino; Step 3: Preparation of ruthenium catalyst with phosphine tridentate ligand: The nitrogen-phosphine ligand, tris(triphenylphosphine)carbonyl ruthenium chloride and solvent prepared in step 2 were added to the reaction vessel and stirred at 110°C for 9 to 12 hours under a nitrogen protective atmosphere. After the reaction was completed, the reaction solution was filtered to obtain a filter cake. After rinsing and drying, the nitrogen-phosphine tridentate ruthenium catalyst was obtained. The chemical structural formula of the nitrogen-phosphine tridentate ruthenium ligand catalyst is shown in Formula I below: Formula I; In Formula I: R1 is selected from methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, and phenyl; R2 is selected from hydrogen, alkoxy, alkyl, and dimethylamino; In step one, the molar ratio of 2-bromoacetal diethyl acetal, organophosphate salt and hydrobromic acid is 1:(1-2):(1.5-3). In step two, the molar ratio of the disubstituted phosphino-acetaldehyde hydrobromide dimer, the aminoquinoline compound, and sodium triacetoxyborohydride is 1:(1-2):(2-4). In step three, the molar ratio of the nitrogen phosphine ligand and tris(triphenylphosphine)carbonyl ruthenium chloride is (1-1.5):1; The solvent is selected from tetrahydrofuran, toluene, 2-methyltetrahydrofuran, ethyl acetate, dichloromethane, chloroform, and methanol.

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