A method for preparing aromatic primary amines by catalytic reduction of nitroarenes with an N-heterocyclic carbene copper complex

Abstract

The present invention discloses a method for preparing aromatic primary amines by homogeneous catalytic reduction of nitroarenes with an N-heterocyclic carbene copper complex. This method uses an inexpensive and stable N-heterocyclic carbene copper complex as the catalyst, ammonia borane as the hydrogen source, and ethanol as the solvent. Without the need for expensive ligands, the reduction of nitro groups can be achieved under mild conditions, and the target compound aromatic primary amine can be obtained in a relatively high yield. The present invention uses a homogeneous copper catalytic system for the reduction of nitroarenes, which has the advantages of low cost, short reaction time, mild reaction conditions, and simple operation, and avoids the use of special equipment such as hydrogen under a certain pressure and autoclaves.

Description

Technical Field

[0001] The present invention belongs to the technical field of hydrogenation of aromatic nitro compounds, and particularly relates to a method for highly selectively preparing aromatic primary amines by homogeneous catalysis of N-heterocyclic carbene copper complexes for aromatic nitro groups. Background Art

[0002] Amines are an important class of organic intermediates and are widely used in fields such as dyes, pharmaceuticals, pesticides, and chemical engineering. Therefore, developing a new strategy for constructing amine compounds has important research significance. Using nitro compounds as raw materials, direct reduction is one of the main routes to obtain amine compounds. So far, many methods for directly reducing nitroarenes to aromatic primary amines have been reported in the literature, such as catalytic hydrogenation, metal reduction, electrochemical reduction, photochemical reduction, etc.

[0003] In 2021, the Magnus Rueping research group reported that using a Mn(II) complex as a catalyst, H2 as a reducing agent, and adding a catalytic amount of potassium carbonate as an additive to the system, nitroarenes were effectively reduced to aromatic amines. This catalytic system can be compatible with functional groups such as halogens, ester groups, amide groups, and sulfonamide groups, and has high yields and good selectivity (Org. Lett. 2021, 23, 2742 - 2747).

[0004] In 2021, the Angaridis research group reported using methylhydrazine as a reducing agent and a Co(III) complex as a catalyst. In MeOH or i PrOH solvents, heating at 70 °C for 2 hours, a series of aromatic amines and heterocyclic amines were synthesized with excellent yields and chemoselectivity (J. Org. Chem. 2021, 86, 2895 - 2906).

[0005] In 2022, the Hung research group reported that commercially available ferric chloride hexahydrate was used as a catalyst, cheap bipyridine as a ligand, and hydrazine hydrate as a reducing agent. Reacting at 100 °C for 12 hours in an aqueous solution could achieve highly selective reduction of nitroarenes. This system has very good substrate applicability and can be compatible with most reducing groups, and excellent yields can be obtained for all (Catalysts. 2022, 12, 924).

[0006] In 2023, the Zhang research group reported that using a Ru complex as a catalyst, H2 as a hydrogen source, and adding a catalytic amount of p-TsOH co-catalyst, reacting at 120 °C for 24 hours in toluene solvent could achieve a large amount of reduction of nitroarenes. This system enabled the conversion of nitroarenes containing different functional groups and achieved good yields (Org. Biomol. Chem. 2023, 21, 1450–1456).

[0007] The above methods have disadvantages such as requiring stoichiometric amounts of catalysts, complex operations, strict reaction conditions, and long reaction times, which lead to certain environmental pollution and economic cost problems, especially serious in the process of large-scale industrial production. Therefore, developing a green and efficient strategy for preparing aromatic primary amines has important scientific research significance. Summary of the Invention

[0008] The object of the present invention is to provide a method for highly selectively hydrogenating and reducing aromatic nitro groups to prepare aromatic primary amines using an N-heterocyclic carbene copper complex as a catalyst and ammonia borane as a hydrogen source in a non-hydrogen atmosphere.

[0009] For the above object, the technical solution adopted by the present invention is: using an N-heterocyclic carbene copper complex as a catalyst, ammonia borane as a hydrogen source, and ethanol as a solvent, stirring and reacting the nitroarene shown in Formula I at 40 - 60 °C under a nitrogen atmosphere and closed conditions, and separating and purifying the product after the reaction to obtain the aromatic primary amine shown in Formula I';

[0010]

[0011] In Formulas I and I', R represents any one of aryl, substituted aryl, heteroaryl, and substituted heteroaryl; specifically, for example, R represents any one of phenyl, naphthyl, fluorenyl, quinolinyl, or any one or two substitutions of phenyl by fluorine, chlorine, bromine, iodine, trifluoromethoxy, C1 - C4 alkyl, hydroxyl, nitro, C1 - C4 hydroxyalkyl, cyano, C1 - C4 alkoxy, acetylamino, amino, C1 - C4 alkylamino, phenyl, phenoxy, benzyl, benzyloxy, styryl, ester group, formyl, acetyl, methylthio, oxazolyl.

[0012] The structure of the above N-heterocyclic carbene copper complex (IMesCuCl) is as follows, and it is prepared by the method in the reference (Angew. Chem. 2016, 128, 1908 - 1912).

[0013]

[0014] In the above preparation method, preferably, the addition amount of the N-heterocyclic carbene copper complex is 1% - 2% of the molar amount of the nitroarene.

[0015] In the above preparation method, preferably, the addition amount of the ammonia borane is 2 - 4 times the molar amount of the nitroarene.

[0016] In the above preparation method, it is further preferred to stir and react at 50 °C for 12 hours under a nitrogen atmosphere and closed conditions.

[0017] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0018] (1) The present invention reports for the first time the use of a homogeneous copper catalytic system for the reduction of nitroarenes, expanding the research scope of the copper catalytic system.

[0019] (2) The reaction conditions of the present invention are mild, the operation is simple, ammonia borane is used instead of hydrogen as the hydrogen source, avoiding the use of hydrogen and autoclave equipment, improving the reaction safety. The post-treatment of the reaction is simple, avoiding the use of acid or base hydrolysis, reducing the reaction cost.

[0020] (3) The present invention has good substrate generality, has good compatibility with functional groups such as halogen, carbonyl, hydroxyl, amino, nitro, cyano, amide, ester, trifluoromethoxy, double bond, imine, etc., heterocycles and heteroatoms, and the product yield is good. Specific Embodiments

[0021] The present invention will be further described in detail below in conjunction with embodiments, but the protection scope of the present invention is not limited to these embodiments.

[0022] Example 1

[0023] Preparation of 1-naphthylamine with the following structural formula

[0024]

[0025] 0.0008 g (0.002 mmol) of N-heterocyclic carbene copper complex and 0.0362 g (0.2 mmol) of 1-nitronaphthalene were added to a 25 mL Schlenk reaction tube. Under a nitrogen atmosphere, 0.0246 g (0.8 mmol) of ammonia borane and 2.5 mL of ethanol were added successively. After sealing the tube, the reaction was stirred at 50 °C for 12 hours. After the reaction was completed, 10 mL of saturated ammonium chloride aqueous solution was added to quench the reaction, and it was extracted with ethyl acetate (10 mL each time, extracted 3 times). The extraction liquids were combined, dried over anhydrous sodium sulfate, and the product was separated by column chromatography using a mixed solution of petroleum ether and ethyl acetate with a volume ratio of 5:1 as the eluent, obtaining red-brown solid 1-naphthylamine with a yield of 95%.

[0026] The spectral data of the obtained product are as follows: 1 H NMR (400 MHz, CDCl3): δ = 7.83 (d, J = 5.9, 3.7 Hz, 2H), 7.53 - 7.42 (m, 2H), 7.38 - 7.28 (m, 2H), 6.80 (dd, J = 6.8, 1.4 Hz, 1H), 4.14 (s, 2H); 13 C NMR (100 MHz, CDCl3): δ = 142.0, 134.3, 128.5, 126.3, 125.8, 124.8, 123.6, 120.7, 118.9, 109.6.

[0027] Example 2

[0028] To prepare 3-phenoxyaniline with the following structural formula

[0029]

[0030] In this example, equimolar 3-phenoxynitrobenzene was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain 3-phenoxyaniline with a yield of 90%.

[0031] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.35 - 7.27(m,2H),7.03(t,J=7.4Hz,1H),6.99 - 6.83(m,4H),6.69(d,J=8.8Hz,2H),3.59(s,2H); 13 C NMR(100MHz,CDCl3):δ=158.8,148.5,142.6,129.5,122.0,121.1,117.1,116.2。

[0032] Example 3

[0033] To prepare 3-(benzyloxy)-2-methylaniline with the following structural formula

[0034]

[0035] In this example, equimolar 3-(benzyloxy)-2-methylnitrobenzene was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain 3-(benzyloxy)-2-methylaniline with a yield of 90%.

[0036] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.49(d,J=6.9Hz,2H),7.43(t,J=7.3Hz,2H),7.37(d,J=7.2Hz,1H),7.01(t,J=8.1Hz,1H),6.43(dd,J=17.5,8.3Hz,2H),5.09(s,2H),3.66(s,2H),2.15(s,3H); 13 C NMR(100MHz,CDCl3):δ=157.3,145.7,137.6,128.4,127.6,127.1,126.5,110.8,108.6,102.5,70.1,9.1。

[0037] Example 4

[0038] Preparation of (E)-4-styrylaniline with the following structural formula

[0039]

[0040] In this example, equimolar (E)-1-nitro-4-styrylbenezene was used to replace 1-nitronaphthalene in Example 1, and other steps were the same as those in Example 1 to obtain (E)-4-styrylaniline with a yield of 87%.

[0041] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.50(d,J=7.3Hz,2H),7.42-7.30(m,4H),7.24(td,J=7.3Hz,1H),7.11-6.89(m,2H),6.68(m,J=8.5Hz,2H),3.74(s,2H); 13 C NMR(100MHz,CDCl3):δ=146.1,137.9,128.6,127.9,127.7,126.8,126.0,125.0,115.1。

[0042] Example 5

[0043] Preparation of 5-(4-aminophenyl)oxazole with the following structural formula

[0044]

[0045] In this example, equimolar 5-(4-nitrophenyl)oxazole was used to replace 1-nitronaphthalene in Example 1, and other steps were the same as those in Example 1 to obtain 5-(4-aminophenyl)oxazole with a yield of 74%.

[0046] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.83(s,1H),7.45(d,J=8.6Hz,2H),7.15(s,1H),6.71(d,J=8.7Hz,2H),3.86(s,2H); 13 C NMR(100MHz,CDCl3):δ=152.0,149.4,146.9,125.8,119.0,118.2,115.0。

[0047] Example 6

[0048] Preparation of 2-aminofluorene with the following structural formula

[0049]

[0050] In this example, 2-nitrofluorene with an equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain 2-aminofluorene, with a yield of 79%.

[0051] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.66(d,J=7.6Hz,1H),7.59(d,J=8.0Hz,1H),7.49(d,J=7.4Hz,1H),7.34(t,J=7.5Hz,1H),7.22(t,J=7.9Hz,1H),6.87(s,1H),6.71(dd,J=7.9Hz,1H),3.82(s,2H); 13 C NMR(100MHz,CDCl3):δ=145.0,142.2,142.0,133.0,126.6,125.0,124.7,120.5,118.5,114.0,111.9,36.8.

[0052] Example 7

[0053] Prepare N-methyl-p-phenylenediamine with the following structural formula

[0054]

[0055] In this example, N-methyl-4-nitroaniline with an equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain N-methyl-p-phenylenediamine, with a yield of 95%.

[0056] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=8.10(d,J=9.2Hz,2H),6.53(d,J=9.2Hz,2H),4.58(s,1H),2.94(d,J=5.2Hz,3H); 13 C NMR(100MHz,CDCl3):δ=154.1,126.4,110.7,30.1,1.1.

[0057] Example 8

[0058] Prepare p-aminophenyl methyl sulfide with the following structural formula

[0059]

[0060] In this example, p-nitrophenyl methyl sulfide with an equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain p-aminophenyl methyl sulfide, with a yield of 88%.

[0061] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.18(d,J=8.6Hz,2H),6.63(d,J=8.6Hz,2H),3.66(s,2H),2.41(s,3H); 13 C NMR(100MHz,CDCl3):δ=145.1,131.0,125.8,115.7,18.8.

[0062] Example 9

[0063] Prepare p-aminotrifluoromethoxybenzene with the following structural formula

[0064]

[0065] In this example, equimolar p-nitrotrifluoromethoxybenzene was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain p-aminotrifluoromethoxybenzene with a yield of 81%.

[0066] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.01(d,J=8.8Hz,2H),6.64(d,J=8.9Hz,2H),3.70(s,2H); 13 C NMR(100MHz,CDCl3):δ=145.2,141.3,122.4,119.3(q,J=253.7Hz),115.5; 19 F NMR(376MHz,CDCl3):δ=-58.4.

[0067] Example 10

[0068] Prepare 1,2-dimethoxy-4-aminobenzene with the following structural formula

[0069]

[0070] In this example, equimolar 1,2-dimethoxy-4-nitrobenzene was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain 1,2-dimethoxy-4-aminobenzene with a yield of 89%.

[0071] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=6.69(d,J=8.4Hz,1H),6.30(d,J=2.6Hz,1H),6.22(dd,J=8.4,2.6Hz,1H),3.81(d,J=9.6Hz,6H),3.43(s,2H);13 CNMR(100MHz, CDCl3): δ = 149.7, 142.0, 140.6, 112.9, 106.3, 100.6, 56.5, 55.6.

[0072] Example 11

[0073] Prepare p-aminobenzonitrile with the following structural formula

[0074]

[0075] In this example, equimolar p-nitrobenzonitrile was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, obtaining p-aminobenzonitrile with a yield of 74%.

[0076] The spectral data of the obtained product are as follows: 1 H NMR(400MHz, CDCl3): δ = 7.42(, J = 8.7Hz, 2H), 6.64(d, J = 8.7Hz, 2H), 4.14(s, 2H); 13 C NMR(100MHz, CDCl3): δ = 150.3, 133.8, 123.7, 114.4, 100.3.

[0077] Example 12

[0078] Prepare p-aminoacetanilide with the following structural formula

[0079]

[0080] In this example, equimolar p-nitroacetanilide was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, obtaining p-aminoacetanilide with a yield of 84%.

[0081] The spectral data of the obtained product are as follows: 1 H NMR(400MHz, CDCl3): δ = 7.26 - 7.21(m, 2H), 7.09(s, 1H), 6.63(d, J = 8.7Hz, 2H), 3.62(s, 2H), 2.12(s, 3H); 13 C NMR(100MHz, CDCl3): δ = 168.2, 143.3, 129.1, 128.1, 122.2, 115.4, 24.3.

[0082] Example 13

[0083] Prepare 3-aminobiphenyl with the following structural formula

[0084]

[0085] In this example, 3-nitrobiphenyl with an equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain 3-aminobiphenyl with a yield of 98%.

[0086] The spectral data of the obtained product are as follows: 1 H NMR (400 MHz, CDCl3): δ = 7.59 (d, J = 7.3 Hz, 2H), 7.44 (t, J = 7.5 Hz, 2H), 7.36 (t, J = 7.3 Hz, 1H), 7.25 (t, J = 7.8 Hz, 1H), 7.02 (d, J = 7.7 Hz, 1H), 6.92 (s, 1H), 6.69 (dd, J = 7.9, 2.3 Hz, 1H), 3.69 (s, 2H); 13 C NMR (100 MHz, CDCl3): δ = 146.7, 142.4, 141.3, 129.6, 128.6, 127.2, 127.0, 117.6, 114.0, 113.8.

[0087] Example 14

[0088] To prepare 4-aminobiphenyl with the following structural formula

[0089]

[0090] In this example, 4-nitrobiphenyl with an equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain 4-aminobiphenyl with a yield of 86%.

[0091] The spectral data of the obtained product are as follows: 1 H NMR (400 MHz, CDCl3): δ = 7.58 (dd, J = 8.3, 1.2 Hz, 2H), 7.44 (dd, J = 12.4, 8.3 Hz, 4H), 7.31 (t, J = 7.4 Hz, 1H), 6.92 - 6.64 (m, 2H), 3.74 (s, 2H); 13 C NMR (100 MHz, CDCl3): δ = 145.8, 141.1, 131.5, 128.6, 127.9, 126.3, 126.2, 115.3.

[0092] Example 15

[0093] To prepare p-chloroaniline with the following structural formula

[0094]

[0095] In this example, p-chloronitrobenzene in equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, to obtain p-chloroaniline with a yield of 80%.

[0096] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.10(d,J=8.8Hz,2H),6.60(d,J=8.8Hz,2H),3.67(s,2H); 13 C NMR(100MHz,CDCl3):δ=144.9,129.1,123.1,116.2.

[0097] Example 16

[0098] Prepare m-aminobenzaldehyde with the following structural formula

[0099]

[0100] In this example, m-aminobenzaldehyde in equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, to obtain m-aminobenzaldehyde with a yield of 76%.

[0101] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,DMSO-d6)δ=6.86(t,J=7.7Hz,1H),6.46(s,1H),6.40-6.23(m,1H),5.02-4.79(m,2H),4.26(d,J=5.7Hz,2H); 13 C NMR(100MHz,DMSO-d6):δ=148.6,143.3,128.6,114.1,112.4,112.2,63.4.

[0102] Example 17

[0103] Prepare 1-methoxy-4-aniline with the following structural formula

[0104]

[0105] In this example, 1-methoxy-4-nitrobenzene in equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, to obtain 1-methoxy-4-aniline with a yield of 73%.

[0106] The spectral data of the obtained product are as follows: 11H NMR (400 MHz, CDCl3): δ = 6.75 (d, J = 9.0 Hz, 2H), 6.65 (d, J = 9.0 Hz, 2H), 3.75 (s, 3H), 3.40 (s, 2H); 13 13C NMR (100 MHz, CDCl3): δ = 152.7, 139.8, 116.4, 114.7, 55.7.

[0107] Example 18

[0108] Prepare p-bromoaniline with the following structural formula

[0109]

[0110] In this example, equimolar p-bromonitrobenzene was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain p-bromoaniline with a yield of 82%.

[0111] The spectral data of the obtained product are as follows: 1 1H NMR (400 MHz, CDCl3) δ = 7.23 (d, J = 8.8 Hz, 2H), 6.56 (d, J = 8.8 Hz, 2H), 3.67 (s, 2H); 13 13C NMR (100 MHz, CDCl3): δ = 145.4, 132.0, 116.7, 110.1, 60.4, 14.2.

[0112] Example 19

[0113] Prepare ethyl p-aminobenzoate with the following structural formula

[0114]

[0115] In this example, equimolar ethyl p-nitrobenzoate was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain ethyl p-aminobenzoate with a yield of 77%.

[0116] The spectral data of the obtained product are as follows: 1 1H NMR (400 MHz, CDCl3) δ = 7.85 (d, J = 8.8 Hz, 2H), 6.63 (d, J = 8.7 Hz, 2H), 4.31 (q, J = 7.1 Hz, 2H), 4.08 (s, 2H), 1.35 (t, J = 7.1 Hz, 3H); 13 13C NMR (100 MHz, CDCl3): δ = 166.7, 150.7, 131.5, 119.9, 113.7, 60.3, 51.6, 14.4.

[0117] Example 20

[0118] Prepare benzo[d][1,3]dioxol-5-amine with the following structural formula

[0119]

[0120] In this example, 5-nitrobenzo[d][1,3]dioxole was used to replace 1-nitronaphthalene in Example 1 in an equimolar amount, and the other steps were the same as those in Example 1, obtaining benzo[d][1,3]dioxol-5-amine with a yield of 74%.

[0121] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3)δ=6.62(d,J=8.2Hz,1H),6.29(d,J=2.3Hz,1H),6.13(dd,J=8.2,2.3Hz,1H),5.86(s,2H),3.47(s,2H); 13 C NMR(100MHz,CDCl3):δ=148.1,141.3,140.3,108.5,106.8,100.6,98.0。

[0122] Example 21

[0123] Prepare p-iodoaniline with the following structural formula

[0124]

[0125] In this example, p-nitroiodobenzene was used to replace 1-nitronaphthalene in Example 1 in an equimolar amount, and the other steps were the same as those in Example 1, obtaining p-iodoaniline with a yield of 70%.

[0126] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3):δ=7.41(d,J=8.7Hz,2H),6.47(d,J=8.7Hz,2H),3.68(s,2H); 13 C NMR(100MHz,CDCl3):δ=146.0,137.9,117.3,79.3。

[0127] Example 22

[0128] Prepare 9,9-dimethyl-2-aminofluorene with the following structural formula

[0129]

[0130] In this example, 9,9-dimethyl-2-nitrofluorene with an equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, obtaining 9,9-dimethyl-2-aminofluorene with a yield of 94%.

[0131] The spectral data of the obtained product are as follows: 1 H NMR (400 MHz, CDCl3): δ = 7.60 (d, J = 8.3, 2.2, 0.9 Hz, 1H), 7.53 (d, J = 8.0, 1.6 Hz, 1H), 7.39 (d, J = 7.4, 1.2 Hz, 1H), 7.30 (td, J = 7.5, 2.7, 1.3 Hz, 1H), 7.23 (td, J = 7.4, 2.6, 1.2 Hz, 1H), 6.78 (d, J = 2.2 Hz, 1H), 6.68 (dd, J = 8.0, 2.2 Hz, 1H), 4.55 - 2.84 (m, 2H), 1.46 (s, 6H); 13 C NMR (100 MHz, CDCl3): δ = 155.5, 152.7, 146.0, 139.6, 130.3, 126.8, 125.5, 122.3, 120.8, 118.7, 114.0, 109.5, 46.5, 27.3.

[0132] Example 23

[0133] Prepare 8-aminoquinoline with the following structural formula

[0134]

[0135] In this example, 8-aminoquinoline with an equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, obtaining 8-aminoquinoline with a yield of 70%.

[0136] The spectral data of the obtained product are as follows: 1 H NMR (400 MHz, CDCl3) δ = 9.07 (dd, J = 4.2, 1.7 Hz, 1H), 8.27 (dd, J = 8.4, 1.7 Hz, 1H), 8.04 (d, J = 7.9 Hz, 2H), 7.67 - 7.51 (m, 2H); 13 C NMR (100 MHz, CDCl3): δ = 152.6, 148.2, 139.5, 136.2, 132.1, 129.0, 125.3, 123.8, 122.8.

[0137] Example 24

[0138] Prepare phenylenediamine with the following structural formula

[0139]

[0140] In this example, equimolar p-nitroaniline was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain phenylenediamine with a yield of 60%.

[0141] The spectral data of the obtained product are as follows: 1 H NMR (400 MHz, CDCl3) δ = 6.57 (s, 2H), 3.25 (s, 2H); 13 C NMR (100 MHz, CDCl3): δ = 138.5, 116.7.

[0142] Example 25

[0143] Prepare p-aminoacetophenone with the following structural formula

[0144]

[0145] In this example, equimolar p-nitroacetophenone was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain p-aminoacetophenone with a yield of 64%.

[0146] The spectral data of the obtained product are as follows: 1 H NMR (400 MHz, CDCl3) δ = 7.14 - 7.06 (m, 2H), 6.72 - 6.63 (m, 2H), 4.19 (q, J = 6.4 Hz, 1H), 3.18 (s, 3H); 13 C NMR (100 MHz, CDCl3): δ = 145.7, 133.3, 127.4, 115.0, 79.2, 56.1, 23.7.

[0147] Example 26

[0148] Prepare 5-aminoquinoline with the following structural formula

[0149]

[0150] In this example, equimolar 5-nitroquinoline was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain 5-aminoquinoline with a yield of 72%.

[0151] The spectral data of the obtained product are as follows: 11H NMR (400 MHz, CDCl3) δ = 8.87 (dd, J = 4.2, 1.7 Hz, 1H), 8.16 (dd, J = 8.5, 1.7, 0.9 Hz, 1H), 7.56 (dd, J = 8.4, 1.0 Hz, 1H), 7.49 (dd, J = 8.5, 7.4 Hz, 1H), 7.32 (dd, J = 8.5, 4.2 Hz, 1H), 6.80 (dd, J = 7.3, 1.1 Hz, 1H), 4.55 - 3.98 (m, 2H); 13 13C NMR (100 MHz, CDCl3): δ = 149.6 (d, J = 117.2 Hz), 142.3, 129.8 (d, J = 45.8 Hz), 119.7 (d, J = 44.6 Hz), 109.9.

[0152] Example 27

[0153] Prepare o - phenylenediamine with the following structural formula

[0154]

[0155] In this example, equimolar o - nitroaniline was used to replace 1 - nitronaphthalene in Example 1, and the other steps were the same as those in Example 1. o - Phenylenediamine was obtained with a yield of 89%.

[0156] The spectral data of the obtained product are as follows: 1 1H NMR (400 MHz, CDCl3) δ = 6.94 - 6.48 (m, 4H), 3.35 (s, 4H); 13 13C NMR (100 MHz, CDCl3): δ = 134.7, 120.2, 116.7.

[0157] Example 28

[0158] Prepare m - phenylenediamine with the following structural formula

[0159]

[0160] In this example, equimolar m - nitroaniline was used to replace 1 - nitronaphthalene in Example 1, and the other steps were the same as those in Example 1. m - Phenylenediamine was obtained with a yield of 82%.

[0161] The spectral data of the obtained product are as follows: 1 1H NMR (400 MHz, CDCl3) δ = 6.94 (t, J = 7.9 Hz, 1H), 6.12 - 6.04 (m, 3H), 3.34 (s, 4H); 13 13C NMR (100 MHz, CDCl3): δ = 147.5, 130.2, 106.0, 101.9.

[0162] Example 29

[0163] Prepare o-aminophenol with the following structural formula

[0164]

[0165] In this example, equimolar o-nitrophenol was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain o-aminophenol with a yield of 90%.

[0166] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3)δ=8.95(s,1H),6.63(dd,J=7.7,1.4Hz,1H),6.60 - 6.48(m,2H),6.38(td,J=7.5,1.8Hz,1H),4.47(s,2H); 13 C NMR(100MHz,CDCl3):δ=144.1,136.7,119.6,116.5,114.6,114.5。

[0167] Example 30

[0168] Prepare aniline with the following structural formula

[0169]

[0170] In this example, equimolar nitrobenzene was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1 to obtain aniline with a yield of 68%.

[0171] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3)δ=7.47 - 7.31(m,2H),6.99(t,J=7.5,1.1Hz,1H),6.81(dd,J=8.6,1.1Hz,2H),3.74(s,2H); 13 C NMR(100MHz,CDCl3):δ=146.2,128.8,117.9,114.6。

[0172] Example 31

[0173] Synthesize 4-((m-tolylimino)methyl)aniline with the following structural formula

[0174]

[0175] In this example, 1-(4-nitrophenyl)-N-(m-tolyl)methanimine in equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, obtaining 4-((m-tolylimino)methyl)aniline with a yield of 63%.

[0176] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3)δ=7.13(t,J=7.7Hz,1H),6.99(d,J=8.6Hz,2H),6.87-6.68(m,2H),6.57(d,J=8.5Hz,3H),4.22(s,1H),3.74(s,2H),2.25(s,3H); 13 C NMR(100MHz,CDCl3):δ=160.8,146.6,146.0,140.9,129.7,129.5,126.6,117.6,113.9(d,J=12.6Hz),112.9,48.6,20.4.

[0177] Example 32

[0178] Prepare 3,5-dichloroaniline with the following structural formula

[0179]

[0180] In this example, 3,5-dichloronitrobenzene in equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, obtaining 3,5-dichloroaniline with a yield of 78%.

[0181] The spectral data of the obtained product are as follows: 1 H NMR(400MHz,CDCl3)δ=6.72(s,1H),6.53(s,2H),3.80(s,2H); 13 C NMR(100MHz,CDCl3):δ=148.2,135.4,118.3,113.2.

[0182] Example 33

[0183] Prepare p-nitroaniline with the following structural formula

[0184]

[0185] In this example, p-dinitrobenzene in equimolar amount was used to replace 1-nitronaphthalene in Example 1, and the other steps were the same as those in Example 1, obtaining p-nitroaniline with a yield of 59%.

[0186] The spectral data of the obtained product are as follows: 11H NMR (400 MHz, DMSO-d6) δ = 7.80 (d, J = 9.1 Hz, 2H), 6.69 - 6.36 (m, 4H); 13 13C NMR (100 MHz, DMSO-d6): δ = 155.9, 135.8, 126.6, 112.5.

[0187] Example 34

[0188] Prepare p-fluoroaniline with the following structural formula

[0189]

[0190] In this example, p-fluoronitrobenzene in equimolar amount was used to replace 1-nitronaphthalene in Example 1, and other steps were the same as those in Example 1, to obtain p-fluoroaniline with a yield of 74%.

[0191] The spectral data of the obtained product are as follows: 1 1H NMR (400 MHz, CDCl3): δ = 6.89 (t, J = 8.8 Hz, 2H), 6.59 (dd, J = 8.9, 4.6 Hz, 2H), 3.62 (s, 2H); 13 13C NMR (100 MHz, CDCl3): δ = 157.1, 154.7, 142.4, 121.3 - 102.7 (m); 19 19F NMR (376 MHz, CDCl3) δ = -126.8.

Claims

1. A N - method for preparing aromatic primary amines by homogeneous catalysis of a heterocyclic carbene copper complex to reduce nitroarenes, characterized in that: Using N - a heterocyclic carbene copper complex as a catalyst, ammonia borane as a hydrogen source, and ethanol as a solvent, the nitroarene shown in Formula I is stirred and reacted at 40-60 °C under a nitrogen atmosphere and closed conditions. After the reaction is completed, the product is separated and purified to obtain the aryl primary amine shown in Formula I′; In Formula I and I', R represents any one of phenyl, naphthyl, fluorenyl, quinolinyl, or phenyl substituted by any one or two of fluorine, chlorine, bromine, iodine, trifluoromethoxy, C1-C4 alkyl, hydroxy, C1-C4 hydroxyalkyl, cyano, C1-C4 alkoxy, acetamido, amino, C1-C4 alkylamino, phenyl, phenoxy, benzyl, benzyloxy, styryl, formyl, acetyl, methylthio, oxazolyl; The above-mentioned N - The structural formula of the heterocyclic carbene copper complex is as follows: 。 2. According to claim 1 N - A method for preparing aromatic primary amines by catalytic reduction of nitroarenes with a heterocyclic carbene copper complex, characterized in that: The N - The addition amount of the heterocyclic carbene copper complex is 1% to 2% of the molar amount of the nitroarene.

3. According to claim 1 N - A method for preparing aromatic primary amines by catalytic reduction of nitroarenes with a heterocyclic carbene copper complex, characterized in that: The addition amount of the ammonia borane is 2 to 4 times the molar amount of the nitroarene.

4. According to claim 1 N - A method for preparing aromatic primary amines by catalytic reduction of nitroarenes with a heterocyclic carbene copper complex, characterized in that: Stir and react at 50 °C for 12 hours under a nitrogen atmosphere and in a sealed condition.

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