Method for in-situ nitration of halogenated aromatic hydrocarbons by electrocatalysis

Abstract

The present invention belongs to the technical field of organic electrochemical synthesis, and specifically relates to a method for electrocatalytic in-situ nitration of halogenated aromatics. The method uses a transition metal salt as a catalyst in an electrolyte and a solvent, under the action of a ligand and in a protective gas environment, to electrocatalyze halogenated aromatics and nitrites to carry out an in-situ nitration reaction of halogenated aromatics to obtain aromatic nitro compounds. The method of the present invention realizes highly selective in-situ nitration of halogenated aromatics through electrocatalysis, and has the advantages of green and environmentally friendly synthesis, mild conditions, simple operation, no need for an external oxidant, low cost, and good functional group compatibility.

Description

Technical Field

[0001] The invention belongs to the technical field of organic electrochemical synthesis, and in particular relates to a method for electrocatalytic in-situ nitration of halogenated aromatic hydrocarbons. Background Art

[0002] Aromatic nitro compounds and their derivatives are ubiquitous synthetic compounds in medicines, pesticides, functional materials and various organic synthesis intermediates. At present, the research on the synthesis of aromatic nitro compounds mainly focuses on the electrophilic nitration reaction of aromatic compounds, which leads to low regioselectivity and yield. In order to solve this problem, some highly selective synthesis of aromatic nitro compounds by in-situ nitration of Ullmann-type coupling routes catalyzed by copper or palladium under high temperature conditions have been reported in recent years. (1) In 2012, Kantam et al. produced these compounds by in-situ nitration of aromatic bromides and iodides using copper-catalyzed Ullmann-type coupling agents (Tetrahedron Lett., 2012, 53: 1511-1513). This strategy can well solve the problems of poor regioselectivity and low yield, but it often requires high temperature heating and has poor universality for aromatic chlorides. (2) In 2009, Buchwald and Fors realized the in-situ nitration of aryl chlorides under palladium catalysis (J.Am.Chem.Soc., 2009, 131, 12898-12899). This strategy avoids the problems of poor regioselectivity and poor functional group compatibility, but palladium as a precious metal catalyst is very toxic and expensive. It is worth mentioning that in 2021, Xu Hao's research group proposed a light-induced iron-catalyzed in-situ nitration strategy for aryl halides (ACS Catal., 2021, 11: 9561-9568). This method was the first to realize the in-situ nitration reaction of aryl halides under illumination conditions with cheap ferrous ion catalysis. However, this method requires strong ultraviolet light irradiation, which is very poor for conventional chlorobenzene.

[0003] In summary, in the previous Ullmann-type in-situ nitration reactions: under copper catalysis, high temperature heating is required and the universality of aromatic chlorides is very poor; under palladium catalysis, although the problem of poor reactivity of chlorobenzene can be solved well, high temperature heating is also required, and the palladium catalyst is very toxic and expensive; under iron catalysis, it often requires harsh conditions such as ultraviolet light to react. Therefore, it is of great significance to explore an in-situ nitration reaction of a cheap metal under mild conditions.

[0004] Electrocatalytic synthesis strategy has gradually developed into an important organic synthesis method, which has the advantages of easy control, mild reaction conditions, and green environmental sustainability. The process of electrocatalytic reaction is to control the ability and rate of electron transfer through electrode potential to achieve the pre-oxidation or pre-reduction process of the reaction substrate at the electrode. From the nature of electrooxidation reaction, it is generally oxidized by losing a single electron at the anode to avoid the use of oxidants.

[0005] As a cheap and low-toxic catalyst, cobalt has been widely used in thermal and photocatalytic organic reactions. Introducing it into the field of organic electrocatalysis also has far-reaching significance. Summary of the invention

[0006] The object of the present invention is to provide a method for the in-situ nitration reaction of electrocatalyzed halogenated aromatic hydrocarbons, by which aromatic nitro compounds with high added value can be generated with high selectivity.

[0007] To achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for in-situ nitration of halogenated aromatic hydrocarbons by electrocatalysis, comprising the following steps:

[0009] In an electrolyte and a solvent, a transition metal salt is used as a catalyst, and under the action of a ligand and a protective gas environment, an in-situ nitration reaction of halogenated aromatic hydrocarbons and nitrites is electrocatalyzed to obtain aromatic nitro compounds. The method of the present invention realizes the in-situ nitration reaction through single electron transfer.

[0010] The chemical formula of the halogenated aromatic hydrocarbon is

[0011] The chemical formula of the nitrite is MNO 2 ;

[0012] The chemical formula of the aromatic nitro compound is

[0013] Wherein: R is hydrogen, an electron donating group or an electron withdrawing group;

[0014] X is a halogen atom Cl, Br or I;

[0015] M is a metal ion Na, K or Cs.

[0016] The electron-donating group is methyl, isopropyl, tert-butyl, methoxy, ethoxy, hydroxyl or methylthio, and the electron-withdrawing group is nitro, cyano, ethyl ketone, fluorine or aldehyde.

[0017] The electrolyte is tetrabutylammonium bromide, tetrabutylammonium tetrafluoroborate or tetrabutylammonium perchlorate.

[0018] The solvent is dimethyl sulfoxide, acetonitrile, DMF or toluene.

[0019] The catalyst is CoCl 2 6H 2 O.

[0020] The ligand is 4-cyanopyridine, 2,2-bipyridine or 8-hydroxyquinoline.

[0021] The electrocatalysis is carried out in a sealed electrolytic cell with a graphite electrode as the anode, a platinum electrode as the cathode, and nitrogen as the protective gas, and the reaction is stirred at room temperature for 24 hours. The electrocatalytic current is 20 mA.

[0022] In a further embodiment, the molar ratio of the aryl halide to the nitrite is 1:3. The molar ratio of the electrolyte to the aryl halide is 1:0.3. The amount of the solvent added is 5 mL of solvent for every 0.3 mmol of the aryl halide.

[0023] The catalyst is added in an amount of 1 to 10% mmol of the halogenated aromatic hydrocarbon, preferably 10% mmol. The ligand is added in an amount of 1 to 20% mmol of the halogenated aromatic hydrocarbon, preferably 20% mmol.

[0024] The beneficial effects of the present invention are:

[0025] This method achieves highly selective in situ nitration of halogenated aromatics through electrocatalysis, and has the advantages of green and environmentally friendly synthesis route, mild conditions, simple operation, no need for external oxidants, low cost and good functional group compatibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of nitrobenzene in Example 1.

[0027] Figure 2 This is the carbon NMR spectrum of nitrobenzene in Example 1.

[0028] Figure 3 This is the hydrogen nuclear magnetic resonance spectrum of 3-nitrotoluene in Example 3.

[0029] Figure 4 This is the carbon NMR spectrum of 3-nitrotoluene in Example 3.

[0030] Figure 5 This is the hydrogen nuclear magnetic resonance spectrum of 2-nitroanisole in Example 8.

[0031] Figure 6 This is the hydrogen nuclear magnetic resonance spectrum of 4-nitroacetophenone in Example 17.

[0032] Figure 7 This is the carbon NMR spectrum of 4-nitroacetophenone in Example 17.

[0033] Figure 8 This is the hydrogen nuclear magnetic resonance spectrum of 2-nitroacetophenone in Example 18.

[0034] Fig. 9 This is the carbon NMR spectrum of 2-nitroacetophenone in Example 18.

[0035] Fig.10 The schematic diagram of the structure of the electrolytic cell used in the embodiment of the present invention is shown in FIG. 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, DETAILED DESCRIPTION

[0036] The present invention is described in more detail below through specific implementation modes to facilitate understanding of the technical solution of the present invention, but is not intended to limit the protection scope of the present invention.

[0037] The electrolytic cell used in the embodiment of the present invention is as follows Fig.10 As shown, the electrolytic cell includes an electrolytic cell body 3, which is a tubular structure. A sealing cover 4 made of polytetrafluoroethylene material is arranged on the electrolytic cell body 3, and a graphite electrode and a platinum sheet electrode are inserted in the sealing cover 4. The graphite electrode and the platinum sheet electrode are respectively connected to the anode 1 and the cathode 2; the electrolytic cell body 3 is also connected to a protective air pipe 5, the end of the protective air pipe 5 is connected to a protective balloon, and a valve 51 is also arranged on the protective air pipe 5.

[0038] Example 1 In-situ nitration of iodobenzene

[0039] First, take 0.3 mmol of iodobenzene and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of MeCN as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product nitrobenzene, with a yield of 70%.

[0040] The nuclear magnetic resonance hydrogen spectrum of nitrobenzene is characterized as follows: 1 H NMR (300 MHz, CDCl 3 )δ8.19(dd,J=8.4,2.3Hz,2H),7.76–7.66(m,1H),7.54(ddd,J=8.9,7.4,1.9Hz,2H).

[0041] The carbon NMR spectrum of nitrobenzene is characterized as follows: 13 C NMR (100 MHz, CDCl 3) δ148.0,134.6,129.3,123.2.

[0042] The reaction equation is as follows:

[0043]

[0044] Example In-situ nitration of diiodobenzene

[0045] First, take 0.3 mmol of iodobenzene and 0.9 mmol of sodium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of MeCN as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product nitrobenzene, with a yield of 56%.

[0046] The nuclear magnetic resonance hydrogen spectrum of nitrobenzene is characterized as follows: 1 H NMR (300 MHz, CDCl 3 )δ8.19(dd,J=8.4,2.3Hz,2H),7.76–7.66(m,1H),7.54(ddd,J=8.9,7.4,1.9Hz,2H)..

[0047] The carbon NMR spectrum of nitrobenzene is characterized as follows: 13 C NMR (100 MHz, CDCl 3) δ148.0,134.6,129.3,123.2.

[0048] The reaction equation is as follows:

[0049]

[0050] Example 3 In-situ nitration of 3-bromotoluene

[0051] First, take 0.3 mmol of 3-bromotoluene and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of DMSO as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 3-nitrotoluene, with a yield of 60%.

[0052] The nuclear magnetic resonance hydrogen spectrum of 3-nitrotoluene is characterized as follows: 1 H NMR (400 MHz, CDCl 3 )δ7.93(d,J=8.6Hz,2H),7.41(d,J=7.6Hz,1H),7.32(t,J=7.7Hz,1H),2.37(s,3H)..

[0053] The carbon NMR spectrum of 3-nitrotoluene is characterized as follows: 13 C NMR (100 MHz, CDCl 3 )δ147.2,138.7,134.3,128.0,122.8,119.6,76.4,76.1,75.7,20.2.

[0054] The reaction equation is as follows:

[0055]

[0056] Example 4 In-situ nitration of 3-iodotoluene

[0057] First, take 0.3 mmol of 3-iodotoluene and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20%mmol of ligand 4-cyanopyridine, then take 1mmol of tetrabutylammonium tetrafluoroborate, add 5mL of DMSO as solvent, add them into a 25mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20mA) at room temperature to react for 24h. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 3-nitrotoluene, with a yield of 71%.

[0058] The nuclear magnetic resonance hydrogen spectrum of 3-nitrotoluene is characterized as follows: 1 H NMR (400 MHz, CDCl 3 )δ7.93(d,J=8.6Hz,2H),7.41(d,J=7.6Hz,1H),7.32(t,J=7.7Hz,1H),2.37(s,3H)..

[0059] The carbon NMR spectrum of 3-nitrotoluene is characterized as follows: 13 C NMR (100 MHz, CDCl 3 )δ147.2,138.7,134.3,128.0,122.8,119.6,76.4,76.1,75.7,20.2.

[0060] The reaction equation is as follows:

[0061]

[0062] Example 5 In-situ nitration of 4-isopropyl iodobenzene

[0063] First, take 0.3 mmol of 4-isopropyl iodobenzene and 1 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium perchlorate, add 5 mL of MeCN as solvent, add them into a special 25 mL sealed electrolytic cell in sequence, use graphite electrode as anode, platinum electrode as cathode, nitrogen as protective gas, seal and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out and detect the final product by TCL, and finally separate by column chromatography to obtain the final product 4-isopropylnitrobenzene, with a yield of 41%.

[0064] The nuclear magnetic resonance hydrogen spectrum of 4-isopropylnitrobenzene is characterized as follows: 1 H NMR (400 MHz, DMSO-d 6 )δ8.06(d,J=8.6Hz,2H),7.45(d,J=8.6Hz,2H),3.03-2.94(m,1H),1.16(d,J=6.9Hz,6H).

[0065] The carbon NMR spectrum of 4-isopropylnitrobenzene is characterized as follows: 13 C NMR (100 MHz, DMSO-d 6 )δ157.1,146.3,128.2,124.0,33.9,23.8.

[0066] The reaction equation is as follows:

[0067]

[0068] Example 6 In-situ nitration of 4-tert-butyl iodobenzene

[0069] First, take 0.3 mmol of 4-tert-butyl iodobenzene and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium bromide, add 5 mL of MeCN as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 4-tert-butylnitrobenzene, with a yield of 32%.

[0070] The nuclear magnetic resonance hydrogen spectrum of 4-tert-butylnitrobenzene is characterized as follows: 1 H NMR (400 MHz, DMSO-d 6 )δ8.15-8.09(m,2H),7.67-7.61(m,2H),1.30(s,9H).

[0071] The carbon NMR spectrum of 4-tert-butylnitrobenzene is characterized as follows: 13 C NMR (100 MHz, DMSO-d 6 )δ159.1,145.9,127.1,123.6,35.6,31.1.

[0072] The reaction equation is as follows:

[0073]

[0074] Example 7 In-situ nitration of 4-bromoanisole

[0075] First, take 0.3 mmol of 4-bromoanisole and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20%mmol of ligand 4-cyanopyridine, then take 1mmol of tetrabutylammonium tetrafluoroborate, add 5mL of MeCN as solvent, add them into a special 25mL sealed electrolytic cell in sequence, use graphite electrode as anode, platinum electrode as cathode, nitrogen as protective gas, seal and stir (I=20mA) at room temperature to react for 24h. After the reaction is completed, take out and detect the final product by TCL, and finally separate by column chromatography to obtain the final product 4-nitroanisole, with a yield of 52%.

[0076] The nuclear magnetic resonance hydrogen spectrum of 4-nitroanisole is characterized as follows: 1 H NMR (400 MHz, CDCl 3)δ8.20(d,J=9.2Hz,2H),6.96(d,J=9.2Hz,2H),3.91(s,3H).

[0077] The carbon NMR spectrum of 4-nitroanisole is characterized as follows: 13 C NMR (100 MHz, CDCl 3 )δ164.7,141.6,125.9,114.1,55.9.

[0078] The reaction equation is as follows:

[0079]

[0080] Example 8 In-situ nitration of 2-iodoanisole

[0081] First, take 0.3 mmol of 2-iodoanisole and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20%mmol of ligand 4-cyanopyridine, then take 1mmol of tetrabutylammonium tetrafluoroborate, add 5mL of MeCN as solvent, add them into a 25mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20mA) at room temperature to react for 24h. After the reaction is completed, take out the final product for TCL detection, and finally separate by column chromatography to obtain the final product 2-nitroanisole, with a yield of 69%.

[0082] The nuclear magnetic resonance hydrogen spectrum of 2-nitroanisole is characterized as follows: 1 H NMR (400MHz, Chloroform-d) δ7.85 (dd, J=8.1, 1.7Hz, 1H), 7.54 (ddd, J=8.8, 7.5, 1.8Hz, 1H), 7.09 (d, J=8.4Hz, 1H), 7.08–6.99 (m, 1H), 3.97 (s, 3H).

[0083] The carbon NMR spectrum of 2-nitroanisole is characterized as follows: 13 C NMR (100 MHz, DMSO-d 6 )δ152.3,139.8,134.9,125.3,120.9,114.6,57.1.

[0084] The reaction equation is as follows:

[0085]

[0086] Example 9 In-situ nitration of 4-iodophenethyl ether

[0087] First, take 0.3 mmol of 4-iodophenyl ether and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 2,2-bipyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of MeCN as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I = 20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 4-nitrophenyl ethyl ether, with a yield of 42%.

[0088] The nuclear magnetic resonance hydrogen spectrum of 4-nitrophenyl ether is characterized as follows: 1 H NMR (400 MHz, CDCl 3 )δ8.14-8.09(m,2H),6.90-6.83(m,2H),4.09-4.03(m,2H),1.40(t,J=7.0Hz,3H).

[0089] The carbon NMR spectrum of 4-nitrophenyl ethyl ether is characterized as follows: 13 C NMR (100 MHz, CDCl 3 )δ164.1,141.4,125.9,114.4,64.5,14.6..

[0090] The reaction equation is as follows:

[0091]

[0092] Example 10 In-situ nitration of 2-iodophenol

[0093] First, take 0.3 mmol of 2-iodophenol and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of MeCN as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 2-nitrophenol, with a yield of 46%.

[0094] The nuclear magnetic resonance hydrogen spectrum of 2-nitrophenol is characterized as follows: 1 HNMR (400MHz, CDCl 3)δ10.57(s,1H),8.10-8.07(m,1H),7.60-7.54(m,1H),7.16-7.13(m,1H),7.01-6.94(m,1H).

[0095] The carbon NMR spectrum of 2-nitrophenol is characterized as follows: 13 C NMR (100 MHz, CDCl 3 )δ155.2 137.6,133.7,125.1,120.3,119.9.

[0096] The reaction equation is as follows:

[0097]

[0098] Example 11 In-situ nitration of 4-iodoanisyl thioether

[0099] First, take 0.3 mmol of 4-iodoanisyl thioether and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20%mmol of ligand 2,2-bipyridine, then take 1mmol of tetrabutylammonium tetrafluoroborate, add 5mL of MeCN as solvent, add them into a 25mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20mA) at room temperature to react for 24h. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 4-nitroanisyl thioether with a yield of 35%.

[0100] The nuclear magnetic resonance hydrogen spectrum of 4-nitroanisole is characterized as follows: 1 H NMR (400 MHz, DMSO-d 6 )δ8.15(d,J=8.6Hz,2H),7.50(d,J=8.9Hz,2H),2.63(s,3H).

[0101] The carbon NMR spectrum of 4-nitroanisole is as follows: 13 C NMR (100 MHz, DMSO-d 6 )δ149.3,144.5,125.6,124.1,14.5.

[0102] The reaction equation is as follows:

[0103]

[0104] Example 12 In-situ nitration of 4-fluoroiodobenzene

[0105] First, take 0.3 mmol of 4-fluoroiodobenzene and 0.9 mmol of cesium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium bromide, add 5 mL of MeCN as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 4-fluoronitrobenzene, with a yield of 86%.

[0106] The nuclear magnetic resonance hydrogen spectrum of 4-fluoronitrobenzene is characterized as follows: 1 H NMR (400 MHz, CDCl 3 )δ8.26-8.22(m,2H),7.21-7.15(m,2H).

[0107] The carbon NMR spectrum of 4-fluoronitrobenzene is characterized as follows: 13 C NMR (100 MHz, CDCl 3 )δ166.32(d,J=257.5Hz),144.4,126.3(d,J=10.1Hz),116.4(d,J=23.7Hz)..

[0108] The reaction equation is as follows:

[0109]

[0110] Example 13 In-situ nitration of 2-nitroiodobenzene

[0111] First, take 0.3 mmol of 2-nitroiodobenzene and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20%mmol of ligand 4-cyanopyridine, then take 1mmol of tetrabutylammonium perchlorate, add 5mL of MeCN as solvent, add them into a 25mL sealed electrolytic cell in sequence, use graphite electrode as anode, platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20mA) at room temperature to react for 24h. After the reaction is completed, take out the final product for TCL detection, and finally separate by column chromatography to obtain the final product 1,2-dinitrobenzene with a yield of 62%.

[0112] The nuclear magnetic resonance hydrogen spectrum of 1,2-dinitrobenzene is characterized as follows: 1 H NMR (400 MHz, CDCl 3)δ8.91(t,J=2.2Hz,1H),8.52-8.51(m,2H),7.81(t,J=8.2Hz,1H).

[0113] The carbon NMR spectrum of 1,2-dinitrobenzene is characterized as follows: 13 C NMR (100 MHz, CDCl 3 )δ148.2,130.8,128.7,118.7.

[0114] The reaction equation is as follows:

[0115]

[0116] Example 14 In-situ nitration of 4-chlorobenzonitrile

[0117] First, take 0.3 mmol of 4-chlorobenzonitrile and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of DMSO as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 4-nitrobenzonitrile, with a yield of 70%.

[0118] The nuclear magnetic resonance hydrogen spectrum of 4-nitrobenzonitrile is characterized as follows: 1H NMR (300 MHz, CDCl3) δ 8.29 (d, J = 8.6 Hz, 1H), 7.73 (d, J = 8.8 Hz, 1H).

[0119] The carbon NMR spectrum of 4-nitrobenzonitrile is characterized as follows: 13 C NMR (75MHz, CDCl 3 )δ150.0,133.4,124.2,118.2,116.8.

[0120] The reaction equation is as follows:

[0121]

[0122] Example 15 In-situ nitration of 2-iodobenzonitrile

[0123] First, take 0.3 mmol of 2-iodobenzonitrile and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of DMSO as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 2-nitrobenzonitrile, with a yield of 80%.

[0124] The nuclear magnetic resonance hydrogen spectrum of 2-nitrobenzonitrile is characterized as follows: 1 H NMR (300 MHz, CDCl 3 )δ8.29-8.26(m,1H),7.88-7.83(m,1H),7.82-7.75(m,2H).

[0125] The carbon NMR spectrum of 2-nitrobenzonitrile is characterized as follows: 13 C NMR (100MHz, DMSO-d6) δ148.2,136.0,135.2,135.1,126.2,115.7,107.2.

[0126] The reaction equation is as follows:

[0127]

[0128] Example 16 In-situ nitration of 3-bromobenzonitrile

[0129] First, take 0.3 mmol of 3-bromobenzonitrile and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of DMSO as solvent, add them into a special 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I = 20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 3-nitrobenzonitrile with a yield of 77%.

[0130] The nuclear magnetic resonance hydrogen spectrum of 3-nitrobenzonitrile is characterized as follows: 1 H NMR (400 MHz, CDCl 3 )δ8.55(t,J=1.8Hz,1H),8.50-8.50(m,1H),8.03-8.03(m,1H),7.76(t,J=8.1Hz,1H).

[0131] The carbon NMR spectrum of 3-nitrobenzonitrile is as follows: 13 C NMR (100 MHz, CDCl 3 )δ148.1,137.4,130.6,127.7,127.4,116.3,114.1.

[0132] The reaction equation is as follows:

[0133]

[0134] Example 17 In-situ nitration of 4-iodoacetophenone

[0135] First, take 0.3 mmol of 4-iodoacetophenone and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 8-hydroxyquinoline, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of MeCN as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 4-nitroacetophenone with a yield of 69%.

[0136] The nuclear magnetic resonance hydrogen spectrum of 4-nitroacetophenone is characterized as follows: 1 H NMR (300MHz, Chloroform-d) δ8.30–8.17(m,1H),8.10–7.98(m,1H),2.62(d,J=1.1Hz,1H).

[0137] The carbon NMR spectrum of 4-nitroacetophenone is as follows: 13 C NMR (75MHz, CDCl 3 )δ196.4,150.3,141.4,129.3,123.9,77.0,77.1,76.6,27.0.

[0138] The reaction equation is as follows:

[0139]

[0140] Example 18 In-situ nitration of 2-iodoacetophenone

[0141] First, take 0.3 mmol of 2-iodoacetophenone and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2O and 20%mmol of ligand 2,2-bipyridine, then take 1mmol of tetrabutylammonium tetrafluoroborate, add 5mL of MeCN as solvent, add them into a 25mL sealed electrolytic cell in sequence, use graphite electrode as anode, platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20mA) at room temperature to react for 24h. After the reaction is completed, take out the final product for TCL detection, and finally separate by column chromatography to obtain the final product 2-nitroacetophenone with a yield of 72%.

[0142] The nuclear magnetic resonance hydrogen spectrum of 2-nitroacetophenone is characterized as follows: 1 H NMR (300MHz, Chloroform-d) δ8.29–8.19(m,2H),8.09–7.99(m,2H),2.62(d,J=1.1Hz,3H).

[0143] The carbon NMR spectrum of 2-nitroacetophenone is as follows: 13 C NMR (100 MHz, CDCl 3 )δ199.9,137.8,134.1,130.8,127.1,124.2,30.1.

[0144] The reaction equation is as follows:

[0145]

[0146] Example 19 In-situ nitration of 4-iodobenzaldehyde

[0147] First, take 0.3 mmol of 4-iodobenzaldehyde and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20% mmol of ligand 4-cyanopyridine, then take 1 mmol of tetrabutylammonium tetrafluoroborate, add 5 mL of toluene as solvent, add them into a 25 mL sealed electrolytic cell in sequence, use a graphite electrode as anode, a platinum electrode as cathode, and nitrogen as protective gas, and stir (I=20 mA) at room temperature to react for 24 hours. After the reaction is completed, take out the final product for TCL detection, and finally separate it by column chromatography to obtain the final product 4-nitrobenzaldehyde, with a yield of 60%.

[0148] The nuclear magnetic resonance hydrogen spectrum of 4-nitrobenzaldehyde is characterized as follows: 1 H NMR (400 MHz, CDCl 3 )δ10.17(s,1H),8.40(d,J=8.7Hz,2H),8.11(d,J=8.7Hz,2H).

[0149] The carbon NMR spectrum of 4-nitrobenzaldehyde is characterized as follows:13 C NMR (100 MHz, CDCl 3 )δ190.2,151.0,140.1,130.5,124.2.

[0150] The reaction equation is as follows:

[0151]

[0152] Example 20 In-situ nitration of 2-iodobenzaldehyde

[0153] First, take 0.3 mmol of 2-iodobenzaldehyde and 0.9 mmol of potassium nitrite, then take 10% mmol of catalyst CoCl 2 6H 2 O and 20%mmol of ligand 2,2-bipyridine, then take 1mmol of tetrabutylammonium tetrafluoroborate, add 5mL of DMF as solvent, add them into a 25mL sealed electrolytic cell in sequence, use graphite electrode as anode, platinum electrode as cathode, nitrogen as protective gas, seal and stir (I=20mA) at room temperature to react for 24h. After the reaction is completed, take out the final product for TCL detection, and finally separate by column chromatography to obtain the final product 2-nitrobenzaldehyde with a yield of 40%.

[0154] The nuclear magnetic resonance hydrogen spectrum of 2-nitrobenzaldehyde is characterized as follows: 1 H NMR (400 MHz, CDCl 3 )δ10.40(s,1H),8.13-8.12(m,1H),7.96-7.94(m,1H),7.83-7.77(m,2H).

[0155] The carbon NMR spectrum of 2-nitrobenzaldehyde is as follows: 13 C NMR (100 MHz, CDCl 3 )δ188.0,149.4,134.1,133.4,131.2,129.4,124.1.

[0156] The reaction equation is as follows:

[0157]

[0158] The embodiments described above are only preferred embodiments of the present invention and are not intended to limit the scope of implementation of the present invention. Therefore, any equivalent changes or modifications made according to the structures, features and principles described in the patent scope of the present invention should be included in the scope of the patent application of the present invention.

Claims

1. A method for in-situ nitration of halogenated aromatics by electrocatalysis, characterized in that: The following steps are involved: In electrolyte and solvent, using transition metal salt as catalyst, under the action of ligand and protective gas environment, electrocatalyze halogenated aromatic hydrocarbons and nitrites to carry out in-situ nitration reaction of halogenated aromatic hydrocarbons to obtain aromatic nitro compounds; The catalyst is CoCl2·6H2O; the ligand is 4-cyanopyridine, 2,2-bipyridine or 8-hydroxyquinoline; The chemical formula of the halogenated aromatic hydrocarbon is The chemical formula of the nitrite is MNO2; The chemical formula of the aromatic nitro compound is Wherein: R is hydrogen, an electron donating group or an electron withdrawing group; X is a halogen atom Cl, Br or I; M is a metal ion Na, K or Cs.

2. The method for in-situ electrocatalytic nitration of halogenated aromatics according to claim 1, characterized in that: The electron-donating group is methyl, isopropyl, tert-butyl, methoxy, ethoxy, hydroxyl or methylthio, and the electron-withdrawing group is nitro, cyano, ethyl ketone, fluorine or aldehyde.

3. The method for in-situ electrocatalytic nitration of halogenated aromatics according to claim 1, characterized in that: The electrolyte is tetrabutylammonium bromide, tetrabutylammonium tetrafluoroborate or tetrabutylammonium perchlorate.

4. The method for in-situ electrocatalytic nitration of halogenated aromatics according to claim 1, characterized in that: The solvent is dimethyl sulfoxide, acetonitrile, DMF or toluene.

5. The method for in-situ electrocatalytic nitration of halogenated aromatics according to claim 1, characterized in that: The electrocatalysis is carried out in a sealed electrolytic cell, with a graphite electrode as an anode, a platinum sheet electrode as a cathode, and nitrogen as a protective gas, and the reaction is stirred at room temperature for 24 hours.

6. The method for in-situ electrocatalytic nitration of halogenated aromatics according to claim 1, characterized in that: The electrocatalytic current was 20 mA.

7. The method for in-situ electrocatalytic nitration of halogenated aromatics according to claim 1, characterized in that: The molar ratio of the halogenated aromatic hydrocarbon to the nitrite is 1:3, the molar ratio of the electrolyte to the halogenated aromatic hydrocarbon is 1:0.3, and the amount of the solvent added is 5 mL of the solvent for every 0.3 mmol of the halogenated aromatic hydrocarbon.

8. The method for in-situ electrocatalytic nitration of halogenated aromatics according to claim 1, characterized in that: The catalyst is added in an amount of 1 to 10% mmol of the halogenated aromatic hydrocarbon, and the ligand is added in an amount of 1 to 20% mmol of the halogenated aromatic hydrocarbon.

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