A method for synthesizing pyridine-fused polycyclic nitrogen heteroaromatic compounds using electrochemical methods

Abstract

The present invention belongs to the field of organic electrosynthesis and relates to a method for electrochemically synthesizing a pyridine-fused polycyclic nitrogen heteroaromatic compound. A 2-[2-phenylethynylamine]-1,4-naphthoquinone analogue, a quaternary ammonium salt and a Lewis acid are dissolved in an organic solvent to obtain a mixed solution; an electrode is inserted into the mixed solution, a constant current is connected in an inert gas atmosphere system, and an electric reaction is carried out with stirring to obtain a pyridine-fused polycyclic nitrogen heteroaromatic compound. The present invention adopts an electrochemical synthesis method, which significantly improves the reaction efficiency. The synthesis method of the present invention does not require an oxidant or a metal catalyst, is simple to operate, and is green and efficient. The pyridine-fused polycyclic nitrogen heteroaromatic compound prepared by the present invention has the characteristics of high biological activity and is widely applicable to the fields of medicine and functional materials. The pyridine-fused polycyclic nitrogen heteroaromatic compound prepared by the present invention can be used as a standard.

Description

Technical Field

[0001] The invention belongs to the field of organic electrosynthesis and relates to a method for synthesizing pyridine-fused polycyclic nitrogen heteroaromatic compounds by electrochemistry. Background Art

[0002] Aza-fused aromatic hydrocarbons (AHs) are a class of polycyclic aromatic hydrocarbons (PAHs) containing nitrogen atoms. They possess significant biological activity and pharmacological value. They are widely used in pharmaceuticals, pesticides, dyes, optoelectronic materials, and other fields. For example, pyridine-fused PAHs exhibit promising pharmacological activities, including anticancer, antiviral, and antibacterial properties.

[0003] There are many methods for the synthesis of nitrogen-fused-ring aromatics, which usually include cyclization, oxidation, reduction, substitution, etc. Multi-step pre-functionalization including halogenation, condensation, addition, oxidation, and finally coupling and cyclization is inevitable for the construction of polycyclic nitrogen-fused-ring aromatics. In contrast, a more direct and powerful method for constructing highly functionalized polycyclic aromatics is through a one-pot multi-step cascade cyclization or transition metal-catalyzed cyclization. However, the above methods usually require the use of oxidants or transition metal catalysts, which leads to problems such as poor experimental safety, high hazards, high toxicity, and environmental unfriendliness.

[0004] Organic electrochemistry is often considered a greener and more practical synthetic method, avoiding the use of exogenous oxidants and reducing agents. Furthermore, the electrolysis process is controllable at different voltages and can be shut down at any time. Consequently, the preparation of a range of highly functionalized polycyclic nitrogen-heteroaromatic compounds via electrooxidative free radical cascade cyclization in the absence of exogenous oxidants or reducing agents has attracted widespread interest and research in organic synthesis. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the deficiencies of the existing technology and provide a new method for synthesizing pyridine-fused polycyclic nitrogen heteroaromatic compounds by electrochemical means. This method overcomes the problems of the traditional system, such as complicated reaction steps, harsh conditions, and the need for oxidants and catalysts.

[0006] In order to solve the above technical problems, the technical solutions adopted by the present invention are as follows:

[0007] The present invention discloses a pyridine-fused polycyclic nitrogen heteroaromatic compound, the structural formula of the pyridine-fused polycyclic nitrogen heteroaromatic compound is shown in Formula II:

[0008]

[0009] Among them, R 1 、R 2Independently selected from any one of hydrogen, C1-C4 alkyl, halogen, unsubstituted or substituted aromatic ring, electron withdrawing group and electron donating group.

[0010] In some embodiments, preferably, R1 is selected from unsubstituted or substituted phenyl, unsubstituted or substituted pyridyl, unsubstituted or substituted thienyl or unsubstituted or substituted naphthyl; the substitution is selected from C1-C4 alkyl, halogen, nitro, cyano, C1-C4 haloalkyl, C1-C4 alkoxy or tert-butoxycarbonylamino; R2 is selected from hydrogen, C1-C4 alkyl, halogen or trifluoromethyl.

[0011] In some embodiments, further preferably, R1 is selected from unsubstituted or substituted phenyl, pyridyl, thienyl or naphthyl; the substitution is selected from methyl, bromine, nitro, cyano, trifluoromethyl, methoxy or tert-butyloxycarbonylamino; R2 is selected from hydrogen, methyl, chlorine or trifluoromethyl.

[0012] Furthermore, the present invention discloses a method for preparing a pyridine-fused polycyclic nitrogen heteroaromatic compound, comprising dissolving a compound I, a quaternary ammonium salt, and a Lewis acid in an organic solvent to obtain a mixed solution; inserting an electrode into the mixed solution, connecting a constant current in an inert gas atmosphere, and stirring to carry out an electrical reaction, thereby obtaining a pyridine-fused polycyclic nitrogen heteroaromatic compound II;

[0013] The structural formula of the compound I is shown in Formula I, and the structural formula of the pyridine-fused polycyclic nitrogen heteroaromatic compound II is shown in Formula II. The structural formulas of Formula I and Formula II are as follows:

[0014]

[0015] Among them, R 1 、R 2 Independently selected from any one of hydrogen, C1-C4 alkyl, halogen, unsubstituted or substituted aromatic ring, electron withdrawing group and electron donating group;

[0016] The organic solvent is methanol, or a combination of methanol and other solvents.

[0017] In some embodiments, the quaternary ammonium salt is any one or a combination of tetrabutylammonium hexafluorophosphate, tetrabutylammonium acetate, tetrabutylammonium tetrafluoroborate and tetrabutylammonium iodide, preferably any one or a combination of tetrabutylammonium hexafluorophosphate, tetrabutylammonium acetate and tetrabutylammonium tetrafluoroborate, further preferably tetrabutylammonium hexafluorophosphate.

[0018] In some embodiments, the Lewis acid is any one or a combination of lanthanum trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate, indium trifluoromethanesulfonate, bismuth trifluoromethanesulfonate and hafnium trifluoromethanesulfonate, preferably any one or a combination of lanthanum trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate and indium trifluoromethanesulfonate, further preferably lanthanum trifluoromethanesulfonate.

[0019] In some embodiments, the other solvent is any one or a combination of acetonitrile, ethanol, dimethyl sulfoxide, N,N-dimethylformamide, methyl tert-butyl ether, trifluoroethanol and hexafluoroisopropanol.

[0020] In some embodiments, preferably, the other solvent is any one or a combination of acetonitrile, dimethyl sulfoxide, N,N-dimethylformamide, methyl tert-butyl ether and trifluoroethanol.

[0021] In some embodiments, further preferably, the other solvent is acetonitrile.

[0022] In some embodiments, more preferably, the organic solvent is a composition of acetonitrile and methanol in a volume ratio of 7:1.

[0023] In some embodiments, in the mixed solution, the concentration of Compound I is 0.025-0.0375 mmol / mL, the concentration of the quaternary ammonium salt is 0.05-0.075 mmol / mL, and the concentration of the Lewis acid is 0.005-0.0075 mmol / mL.

[0024] In some embodiments, preferably, in the mixed solution, the concentration of Compound I is 0.025 mmol / mL, the concentration of the quaternary ammonium salt is 0.05 mmol / mL, and the concentration of the Lewis acid is 0.005 mmol / mL.

[0025] In some embodiments, the positive electrode of the electrode is a carbon cloth electrode, a carbon rod electrode, a foam carbon electrode or a platinum electrode, and the negative electrode is an iron electrode, a nickel electrode or a platinum electrode.

[0026] In some embodiments, preferably, the positive electrode of the electrodes is a carbon cloth electrode or a foam carbon electrode, and the negative electrode is a nickel electrode or a platinum electrode.

[0027] In some embodiments, further preferably, the positive electrode of the electrode is a carbon cloth electrode, and the negative electrode is a platinum electrode.

[0028] In some embodiments, the constant current is 8-12 mA, preferably 10 mA.

[0029] In some embodiments, the electrical reaction has a reaction temperature of 20 to 50° C. and a reaction time of 3 to 5 hours.

[0030] In some embodiments, preferably, the electrical reaction has a reaction temperature of 25° C. and a reaction time of 3 h.

[0031] In some embodiments, the inert gas is N2.

[0032] Among them, the above-mentioned compound I is a 2-[2-phenylethynylamine]-1,4-naphthoquinone analog. The specific synthesis method refers to the prior art: Org. Biomol. Chem. 16, 5483-5491; 2018.

[0033] Beneficial effects:

[0034] (1) The present invention adopts an electrochemical synthesis method, which significantly improves the reaction efficiency.

[0035] (2) The synthesis method of the present invention does not require an oxidant, is simple to operate, and is green and efficient.

[0036] (3) The pyridine-fused polycyclic nitrogen heteroaromatic compounds prepared by the present invention are generally applicable to the fields of medicine and functional materials.

[0037] (4) The pyridine-fused polycyclic nitrogen heteroaromatic compound prepared by the present invention can be used as a standard. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0039] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of the product 2a in Example 1.

[0040] Figure 2 This is the hydrogen nuclear magnetic resonance spectrum of the product 2b in Example 11.

[0041] Figure 3 This is the hydrogen nuclear magnetic resonance spectrum of product 2c in Example 12.

[0042] Figure 4 This is the hydrogen nuclear magnetic resonance spectrum of product 2d in Example 13.

[0043] Figure 5 This is the hydrogen nuclear magnetic resonance spectrum of the product 2e in Example 14.

[0044] Figure 6 This is the hydrogen nuclear magnetic resonance spectrum of the product 2f in Example 15.

[0045] Figure 7 This is the hydrogen nuclear magnetic resonance spectrum of product 2g in Example 16.

[0046] Figure 8This is the hydrogen nuclear magnetic resonance spectrum of the product 2h in Example 17.

[0047] Figure 9 This is the hydrogen nuclear magnetic resonance spectrum of product 2i in Example 18.

[0048] Figure 10 This is the hydrogen nuclear magnetic resonance spectrum of product 2j in Example 19.

[0049] Figure 11 This is the hydrogen nuclear magnetic resonance spectrum of the product 2k in Example 20.

[0050] Figure 12 This is the hydrogen nuclear magnetic resonance spectrum of product 21 in Example 21.

[0051] Figure 13 This is the hydrogen nuclear magnetic resonance spectrum of product 2m in Example 22.

[0052] Figure 14 This is the hydrogen nuclear magnetic resonance spectrum of product 2n in Example 23.

[0053] Figure 15 This is the hydrogen nuclear magnetic resonance spectrum of the product 2o in Example 24.

[0054] Figure 16 This is the reaction equation for the electrochemical synthesis of pyridine-fused polycyclic nitrogen heteroaromatic compounds. DETAILED DESCRIPTION

[0055] The present invention can be better understood according to the following examples. However, it is easy for those skilled in the art to understand that the contents described in the examples are only used to illustrate the present invention, and should not and will not limit the present invention described in detail in the claims.

[0056] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials are commercially available unless otherwise specified.

[0057] The reaction equation for the electrochemical synthesis of pyridine-fused polycyclic nitrogen heteroaromatic compounds in the embodiment of the present invention is shown in Figure 16 .

[0058] The specific synthesis method of the 2-[2-phenylethynylamine]-1,4-naphthoquinone analogue used in the examples of the present invention is referred to the prior art: Org. Biomol. Chem. 16, 5483-5491; 2018.

[0059] Among them, the pyridine-fused polycyclic nitrogen heteroaromatic compounds 2 shown in Table 1 are all products synthesized by the method of the present invention and confirmed by nuclear magnetic resonance characterization; Table 2 shows the reactant 1 used in the examples of the present invention.

[0060] Table 1 Pyridine-fused polycyclic nitrogen heteroaromatic compounds 2 in the examples of the present invention

[0061]

[0062]

[0063] Table 2 Reactants used in the examples of the present invention

[0064]

[0065]

[0066] Example 1: Synthesis of Compound 2a

[0067] 2-[2-phenylethynylamine]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), acetonitrile (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. The reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in an 84% yield.

[0068] Figure 1 This is the hydrogen nuclear magnetic resonance spectrum of product 2a in Example 1. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0069] 1H NMR(400MHz,Chloroform-d)δ8.53-8.49(m,0.5H),8.44-8.40(m,0.5H),8.30(ddd ,J=7.5,5.9,1.4Hz,1H),7.93-7.88(m,1H),7.86-7.82(m,1H),7.82-7.78(m,1H),7 .76-7.66(m,1.5H),7.66-7.51(m,2.5H),7.45-7.39(m,1.5H),7.39-7.35(m,1H), 7.24-7.20(m,1.5H),3.71(s,1.5H),3.34(s,1.5H),3.08(s,1.5H),2.82(s,1.5H); 13 C NMR(101MHz,Chloroform-d)δ184.90,150.22,146.54,143.27,139.73,138.62,137.32,135.01,132.87,132.36,130.96,13 0.15,129.68,129.58,129.20,128.36,126.70,125.40,123.98,123.86,115.54,101.78,53.34,51.13; HRMS(ESI-TOF)Calcd for C 26 H 20 NO4[M+H] + :410.1387; found:410.1394.

[0070] Example 2: Synthesis of Compound 2a - Solvent Screening

[0071] 2-[2-phenylethynylamine]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), dimethyl sulfoxide (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. Reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 21%.

[0072] Example 3: Synthesis of Compound 2a - Solvent Screening

[0073] 2-[2-phenylethynylamino]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), methyl tert-butyl ether (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. The reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 33%.

[0074] Example 4: Synthesis of Compound 2a - Solvent Screening

[0075] 2-[2-phenylethynylamino]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), N,N-dimethylformamide (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. Reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After completion of the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 43%.

[0076] Example 5: Synthesis of Compound 2a and Screening of Quaternary Ammonium Salts

[0077] 2-[2-phenylethynylamine]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium tetrafluoroborate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), acetonitrile (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. The reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 42%.

[0078] Example 6: Synthesis of Compound 2a - Quaternary Ammonium Salt Screening

[0079] 2-[2-phenylethynylamine]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium acetate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), acetonitrile (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. Reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 63%.

[0080] Example 7: Synthesis of Compound 2a - Lewis Acid Screening

[0081] 2-[2-phenylethynylamino]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), ytterbium trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), acetonitrile (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture and the reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. Reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 64%.

[0082] Example 8: Synthesis of Compound 2a - Lewis Acid Screening

[0083] 2-[2-phenylethynylamine]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), indium trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), acetonitrile (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. The reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 78%.

[0084] Example 9: Synthesis of Compound 2a - Cathode Screening

[0085] 2-[2-phenylethynylamino]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), acetonitrile (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A foam carbon electrode (35 mm x 15 mm x 1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. Reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 62%.

[0086] Example 10: Synthesis of Compound 2a - Negative Electrode Screening

[0087] 2-[2-phenylethynylamino]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), acetonitrile (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture. The reaction was carried out under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a nickel electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The constant current was maintained at 10 mA, and the reaction time was approximately 3 h. Reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1). After completion of the reaction, the reaction solution was extracted with ethyl acetate (50 mL × 3) and water (50 mL × 3). The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated. The crude product was separated by silica gel column chromatography using petroleum ether / ethyl acetate = 10:1 as the developing solvent to obtain the target product 2a in a yield of 75%.

[0088] Example 11: Synthesis of Compound 2b

[0089] The method was the same as that in Example 1, except that compound 1b was used in the reaction. The yield was 78%, and product 2b was obtained after column chromatography separation.

[0090] Figure 2 This is the H NMR spectrum of product 2b in Example 11. The specific NMR data and mass spectrometry data are as follows:

[0091] 1 H NMR(400MHz,Chloroform-d)δ8.55-8.49(m,0.5H),8.46-8.40(m,0.5H),8.30(ddd,J =7.8,5.0,1.4Hz,1H),7.97-7.89(m,1H),7.88-7.83(m,1H),7.83-7.78(m,0.5H),7. 76-7.66(m,2.5H),7.60-7.52(m,2H),7.32-7.20(m,2H),7.08-6.99(m,1H),3.72(s, 1.5H),3.35(s,1.5H),3.10(s,1.5H),2.83(s,1.5H),2.37(s,1.5H),2.23(s,1.5H); 13C NMR(101MHz,Chloroform-d)δ184.93,150.31,146.54,143.44,139.02,138.79,136.94,136.81,134.91,132.87,132.30,130.9 4,130.10,129.62,129.55,129.09,126.61,125.39,123.97,123.90,116.10,101.64,53.28,51.10,21.27; HRMS(ESI-TOF)Calcd for C 27 H 22 NO4[M+H] + :424.1543; found:424.1546.

[0092] Example 12: Synthesis of Compound 2c

[0093] The method was the same as that in Example 1, except that compound 1c was used in the reaction. The yield was 82%, and product 2c was obtained after column chromatography separation.

[0094] Figure 3 This is the hydrogen nuclear magnetic resonance spectrum of the product 2c in Example 12. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0095] 1 H NMR(400MHz,Chloroform-d)δ8.55-8.48(m,0.5H),8.46-8.41(m,0.5H),8.30(dd,J=7.6,5.3Hz ,1H),7.92-7.87(m,0.5H),7.86-7.80(m,2H),7.78-7.71(m,1H),7.71-7.66(m,1.5H),7.65-7.5 9(m,1.5H),7.58-7.54(m,1H),7.44-7.40(m,0.5H),7.39-7.32(m,1H),7.24-7.20(m,1H),3.70 (d,J=11.2Hz,1.5H),3.34(d,J=4.6Hz,1.5H),3.09(d,J=4.9Hz,1.5H),2.82(d,J=5.1Hz,1.5H); 13C NMR(101MHz,Chloroform-d)δ184.74,150.31,146.80,143.26,139.72,138.93,138.62,137.30,134.51,132.78,132.37,13 1.60,129.76,129.70,128.53,128.45,126.70,125.21,123.59,123.34,115.35,101.87,53.41,51.16; HRMS(ESI-TOF)Calcd for C 26 H 19 BrNO4[M+H] + :488.0492;found:488.0502.

[0096] Example 13: Synthesis of Compound 2d

[0097] The method was the same as that in Example 1, except that compound 1d was used in the reaction. The yield was 83%, and product 2d was obtained after column chromatography separation.

[0098] Figure 4 This is the hydrogen nuclear magnetic resonance spectrum of product 2d in Example 13. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0099] 1 H NMR(400MHz,Chloroform-d)δ8.55-8.50(m,0.65H),8.48-8.43(m,0.35H),8.31(d dd,J=7.8,5.2,1.4Hz,1H),7.99-7.92(m,1.3H),7.89-7.84(m,1H),7.84-7.79(m, 1H),7.79-7.73(m,1H),7.72-7.68(m,2H),7.68-7.62(m,1.3H),7.62-7.56(m,1H) ,7.48(s,1.4H),3.71(s,1.05H),3.34(s,1.05H),3.09(s,1.95H),2.84(s,1.95H); 13C NMR(101MHz,Chloroform-d)δ184.68,150.27,146.52,143.58,142.50,137.91,137.36,135.38,132.80,132.53,131.12(q,J=23.2Hz),130.39,129.8 0,129.76,129.66,127.26,125.39(td,J=8.1,4.0Hz),125.23,123.88(q,J =252.2Hz),123.48,123.00,122.63,122.45,115.07,102.06,51.20,51.17; 19 F NMR(376MHz,Chloroform-d)δ-62.66; HRMS(ESI-TOF)Calcd forC 27 H 19 F3NO4[M+H] + :478.1261; found:478.1262.

[0100] Example 14: Synthesis of Compound 2e

[0101] The method was the same as that in Example 1, except that compound 1e was used in the reaction. The yield was 77%, and product 2e was obtained after column chromatography separation.

[0102] Figure 5 This is the hydrogen nuclear magnetic resonance spectrum of the product 2e in Example 14. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0103] 1 H NMR(400MHz,Chloroform-d)δ8.55-8.50(m,0.4H),8.49-8.42(m,0.6H),8.31(ddd,J=7.5,5.9,1. 5Hz,1H),7.97-7.93(m,0.8H),7.89-7.83(m,1H),7.83-7.77(m,1H),7.76(d,J=1.4Hz,0.4H),7.75 -7.73(m,1H),7.72-7.70(m,1H),7.70-7.65(m,1H),7.64-7.61(m,1H),7.60-7.57(m,0.4H),7.55- 7.49(m,1.2H),7.48-7.42(m,1.2H),3.70(s,1.8H),3.34(s,1.8H),3.08(s,1.2H),2.84(s,1.2H); 13C NMR(101MHz,Chloroform-d)δ184.44,150.34,146.84,145.03,142.50,137.97,137.38,135.53,132.93,132.54,132.23,130.99 ,130.33,129.86,129.82,127.49,125.34,123.18,122.79,118.24,114.63,112.88,101.91,53.54,51.18; HRMS(ESI-TOF)Calcd for C 27 H 19 N2O4[M+H] + :435.1339; found:435.1348.

[0104] Example 15: Synthesis of Compound 2f

[0105] The method was the same as that in Example 1, except that compound 1f was used in the reaction. The yield was 62%, and product 2f was obtained after column chromatography separation.

[0106] Figure 6 This is the hydrogen nuclear magnetic resonance spectrum of the product 2f in Example 15. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0107] 1 H NMR(400MHz,Chloroform-d)δ8.56-8.51(m,0.67H),8.48-8.44(m,0.33H),8. 35-8.32(m,0.33H),8.32-8.25(m,2H),8.09-8.05(m,0.67H),8.04-8.00(m,1H ),7.79-7.78(m,2H),7.80-7.73(m,1H),7.72-7.65(m,2H),7.65-7.58(m,1.33 H),7.55-7.49(m,0.67H),3.71(s,1H),3.35(s,1H),3.10(s,2H),2.86(s,2H); 13C NMR(101MHz,Chloroform-d)δ184.52,150.30,148.09,146.39,142.03,137.61,133.98,132.96,132.83,131.25,130.54,12 9.91,129.88,129.79,127.99,125.26,124.37,123.68,123.59,123.23,114.59,102.25,51.29,51.21; HRMS(ESI-TOF)Calcd for C 26 H 19 N2O6[M+H] + :455.1238; found:455.1272.

[0108] Example 16: Synthesis of Compound 2g

[0109] The method was the same as that in Example 1, except that 1 g of compound was involved in the reaction. The yield was 78%, and 2 g of product was obtained after column chromatography separation.

[0110] Figure 7 This is the hydrogen nuclear magnetic resonance spectrum of product 2g in Example 16. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0111] 1 H NMR (400MHz, Chloroform-d) δ8.51-8.45(m,0.6H),8.42-8.38(m,0.4H),8.27(ddd,J=7.8,4.6,1. 3Hz,1H),7.91-7.87(m,0.8H),7.86-7.75(m,2H),7.74-7.69(m,1.6H),7.68-7.64(m,0.8H),7.64 -7.60(m,0.4H),7.60-7.51(m,1.8H),7.30-7.27(m,0.6H),6.94-6.89(m,1.2H),6.75-6.69(m,0. 8H),3.79(s,1.8H),3.68(s,1.2H),3.66(s,1.2H),3.31(s,1.2H),3.08(s,1.8H),2.79(s,1.8H); 13C NMR(101MHz,Chloroform-d)δ184.92,160.11,150.19,146.51,143.40,138.45,137.23,133.98,132.78,132.31,132.21,130.9 3,130.10,129.62,129.55,128.10,125.19,123.85,123.39,116.02,113.66,101.55,55.28,53.27,51.13; HRMS(ESI-TOF)Calcd for C 27 H 22 NO5[M+H] + :440.1492; found:440.1495.

[0112] Example 17: Synthesis of Compound 2h

[0113] The method was the same as that in Example 1, except that compound 1h was used in the reaction. The yield was 82%, and product 2h was obtained after column chromatography separation.

[0114] Figure 8 This is the hydrogen nuclear magnetic resonance spectrum of the product 2h in Example 17. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0115] 1 H NMR(400MHz,Chloroform-d)δ8.57(m,0.85H),8.47(m,0.15H),8.32-8.24(m,1H),8.10-8. 04(m,0.85H),7.92-7.84(m,1.85H),7.81(m,0.15H),7.70(m,2H),7.62(m,0.15H),7.55(m ,1.15H),7.37(m,0.85H),7.26(m,0.85H),7.20(m,0.15H),7.07(dd,J=7.8,1.4Hz,1H),6. 99(m,1H),3.70(s,0.45H),3.34(s,0.45H),2.90(s,3H),2.85(s,2.55H),2.80(s,2.55H); 13C NMR(101MHz,Chloroform-d)δ184.80,150.09,146.54,144.02,138.78,137.96,137.77,137.55,136.76,133.71,132.99,132.44,132.3 8,132.21,130.99,130.29,129.48,129.03,127.65,125.10,125.07,124.74,118.30,101.54,50.95,50.88,21.02; HRMS(ESI-TOF)Calcd for C 27 H 22 NO4[M+H] + :424.1543; found:424.1546.

[0116] Example 18: Synthesis of Compound 2i

[0117] The method was the same as that in Example 1, except that compound 1i was involved in the reaction. The yield was 70%, and product 2i was obtained after column chromatography separation.

[0118] Figure 9 This is the hydrogen nuclear magnetic resonance spectrum of the product 2i in Example 18. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0119] 1 H NMR (400MHz, Chloroform-d) δ8.52-8.45(m,0.6H),8.43-8.39(m,0.4H),8.28(ddd,J=7.8,3. 0,1.3Hz,1H),7.91-7.86(m,0.8H),7.85-7.79(m,1.6H),7.75-7.71(m,1.4H),7.69-7.64(m,1 H),7.63-7.54(m,2H),7.45-7.39(m,1.2H),7.30-7.18(m,2H),6.62(s,0.6H),6.48(s,0.4H) ,3.69(s,1.2H),3.33(s,1.2H),3.09(s,1.8H),2.80(s,1.8H),1.50(s,5.4H),1.44(s,3.6H); 13C NMR(101MHz,Chloroform-d)δ184.89,152.63,150.20,146.51,143.28,139.17,138.93,134.52,134.26,134.01,132.73,132.31,130.9 3,130.09,129.66,129.45,127.58,125.19,123.85,123.38,118.00,115.83,101.66,80.78,51.11,51.09,28.32; HRMS(ESI-TOF)Calcd for C 31 H 29 N2O6[M+H] + :525.2020;found:525.2039.

[0120] Example 19: Synthesis of Compound 2j

[0121] The method was the same as that in Example 1, except that compound 1j was involved in the reaction. The yield was 70%, and product 2j was obtained after column chromatography separation.

[0122] Figure 10 This is the hydrogen nuclear magnetic resonance spectrum of product 2j in Example 19. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0123] 1 H NMR (400MHz, Chloroform-d) δ8.56-8.52(m,0.5H),8.46-8.39(m,0.5H),8.33(ddd,J=9.0,7.7,1. 4Hz,1H),8.29-8.25(m,0.5H),8.23-8.18(m,0.5H),7.98-7.89(m,2H),7.88-7.83(m,2H),7.83-7. 77(m,1H),7.74-7.66(m,2H),7.65-7.62(m,0.5H),7.61-7.56(m,1.5H),7.55-7.48(m,1.5H),7.4 8-7.39(m,1H),7.15-7.07(m,0.5H),3.78(s,1.5H),3.37(s,1.5H),3.09(s,1.5H),2.88(s,1.5H); 13C NMR(101MHz,Chloroform-d)δ184.89,150.34,146.58,143.21,138.38,137.18,134.03,133.64,132.84,132.78,132.38,131.01,130.19,129.66 ,129.63,128.82,128.36,127.66,126.83,126.32,126.08,125.22,124. 45,124.03,123.89,116.09,101.88,51.22,51.15; HRMS(ESI-TOF)Calcd for C 30 H 22 NO4[M+H] + :460.1543; found:460.1544.

[0124] Example 20: Synthesis of Compound 2k

[0125] The method was the same as that in Example 1, except that compound 1k was involved in the reaction. The yield was 68%, and product 2k was obtained after column chromatography separation.

[0126] Figure 11 This is the hydrogen nuclear magnetic resonance spectrum of the product 2k in Example 20. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0127] 1 H NMR(400MHz,Chloroform-d)δ8.65-8.61(m,0.8H),8.58(m,0.2H),8.52-8.49(m,1H),8.31- 8.26(m,1H),8.22-8.17(m,0.8H),8.13-8.10(m,0.2H),7.99-7.95(m,1H),7.95-7.90(m,1H ),7.90-7.86(m,1H),7.86-7.82(m,1H),7.77-7.68(m,2H),7.61-7.56(m,1H),7.50-7.47(m ,0.2H),7.37-7.32(m,0.8H),3.73(s,0.6H),3.37(s,0.6H),3.04(s,2.4H),2.88(s,2.4H); 13C NMR(101MHz,Chloroform-d)δ181.77,157.42,150.28,148.78,147.93,141.06,138.03,134.78,134.73,133.64,133.25,132.56 ,131.64,129.82,129.61,129.08,128.33,127.57,124.70,124.26,122.53,120.83,100.07,51.31,50.89; HRMS(ESI-TOF)Calcd for C 25 H 19 N2O4[M+H] + :411.1339; found:411.1346.

[0128] Example 21: Synthesis of Compound 21

[0129] The method was the same as that in Example 1, except that compound 11 was used in the reaction. The yield was 62%, and product 21 was obtained after column chromatography separation.

[0130] Figure 12 This is the hydrogen nuclear magnetic resonance spectrum of the product 21 in Example 21. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0131] 1 H NMR(400MHz,Chloroform-d)δ8.53-8.48(m,0.6H),8.47-8.41(m,0.4H),8.31-8.24(m,1H),8. 18-8.11(m,0.4H),8.04-7.99(m,0.6H),7.96-7.91(m,0.4H),7.87-7.82(m,1H),7.81-7.76(m ,0.6H),7.70-7.64(m,2H),7.61-7.55(m,1H),7.45-7.40(m,0.6H),7.23-7.18(m,1H),7.02-6 .94(m,1H),6.85-6.82(m,0.4H),3.70(s,1.2H),3.32(s,1.2H),3.17(s,1.8H),2.88(s,1.8H); 13C NMR(101MHz,Chloroform-d)δ184.69,150.30,146.52,143.37,142.86,138.06,136.89,133.97,132.78,132.32,131.01,13 0.23,129.68,129.57,127.06,126.95,126.86,125.29,123.74,123.63,113.50,101.70,51.39,51.25; HRMS(ESI-TOF)Calcd for C 24 H 18 NO4S[M+H] + :416.0951;found:416.0953.

[0132] Example 22: Synthesis of Compound 2m

[0133] The method was the same as that in Example 1, except that compound 1m was used in the reaction. The yield was 78%, and product 2m was obtained after column chromatography separation.

[0134] Figure 13 This is the hydrogen nuclear magnetic resonance spectrum of the product 2m in Example 22. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0135] 1 H NMR(400MHz,Chloroform-d)δ8.40-8.35(m,0.57H),8.30-8.23(m,1.43H),7.8 9-7.85(m,0.43H),7.83-7.80(m,0.57H),7.79-7.76(m,1H),7.67-7.60(m,2H), 7.58-7.49(m,2H),7.43-7.38(m,1.57H),7.37-7.34(m,1H),7.26-7.15(m,1.4 3H),3.69(s,1.3H),3.31(s,1.3H),3.02(s,1.7H),2.82(s,1.7H),2.43(s,3H); 13C NMR(101MHz,Chloroform-d)δ184.87,148.82,145.57,142.16,141.09,139.88,138.38,134.53,133.99,133.41,132.68,131.9 8,129.56,129.51,129.16,128.41,126.68,125.13,122.59,122.18,116.06,101.66,51.19,51.06,22.09; HRMS(ESI-TOF)Calcd for C 27 H 22 NO4[M+H] + :424.1543; found:424.1549.

[0136] Example 23: Synthesis of Compound 2n

[0137] The method was the same as that in Example 1, except that compound 1n was involved in the reaction. The yield was 70%, and product 2n was obtained after column chromatography separation.

[0138] Figure 14 This is the hydrogen nuclear magnetic resonance spectrum of the product 2n in Example 23. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0139] 1 H NMR(400MHz,Chloroform-d)δ8.46-8.41(m,0.4H),8.37-8.33(m,0.6H),8.32-8.27(m, 1H),8.17-8.10(m,0.4H),7.93-7.89(m,0.6H),7.87-7.82(m,1H),7.80-7.76(m,1H),7 .75-7.70(m,1H),7.69-7.65(m,1H),7.64-7.58(m,1H),7.46-7.42(m,1H),7.38-7.35( m,1H),7.28-7.24(m,2H),3.71(s,1.8H),3.34(s,1.8H),3.07(s,1.2H),2.84(s,1.2H); 13CNMR(101MHz,Chloroform-d)δ184.42,148.66,146.93,143.33,139.24,138.42,136.20,135.70,133.76,133.63,133.02,13 1.82,129.75,129.70,129.16,128.55,126.67,125.45,125.24,122.35,115.30,101.74,51.23,51.18; HRMS(ESI-TOF)Calcd for C 26 H 19 ClNO4[M+H] + :444.0997; found:444.0975.

[0140] Example 24: Synthesis of Compound 2o

[0141] The method was the same as that in Example 1, except that compound 1o was used in the reaction. The yield was 74%, and product 2o was obtained after column chromatography separation.

[0142] Figure 15 This is the hydrogen nuclear magnetic resonance spectrum of the product 2o in Example 24. The specific nuclear magnetic resonance data and mass spectrum data are as follows:

[0143] 1 H NMR(400MHz,Chloroform-d)δ8.68-8.60(m,0.63H),8.58-8.51(m,0.37H),8.35-8.27(m,1H ),8.25(d,J=2.0Hz,0.37H),8.14(d,J=2.0Hz,0.63H),8.02-7.95(m,1H),7.93-7.86(m,1H) ,7.85-7.79(m,1.26H),7.78-7.68(m,1H),7.67-7.56(m,1H),7.49-7.45(m,0.74H),7.45-7 .37(m,2H),7.29-7.24(m,1H),3.76(s,1.1H),3.37(s,1.1H),3.13(s,1.9H),2.87(s,1.9H); 13C NMR(101MHz,Chloroform-d)δ184.47,151.08,148.44,144.78,139.30,138.11,133.47,133.30,133.12,131.40(q,J=33.3Hz),129.83,129.73,1 29.49,128.60,126.68,126.56,126.37(q,J=3.1Hz),125.34,123.35(q, J=274.7Hz),123.09,121.52(q,J=5.1Hz),115.87,101.73,51.29,51.25; 19 F NMR(376MHz,Chloroform-d)δ-62.82; HRMS(ESI-TOF)Calcd for C 27 H 19 F3NO4[M+H] + :478.1261; found:478.1267.

[0144] Example 25: Necessity of Electric Current

[0145] 2-[2-phenylethynylamine]-1,4-naphthoquinone 1a (0.2 mmol, 1.0 equiv), tetrabutylammonium hexafluorophosphate (0.4 mmol, 2.0 equiv), lanthanum trifluoromethanesulfonate (0.04 mmol, 0.2 equiv), acetonitrile (7 mL), and methanol (1 mL) were weighed and mixed to obtain a mixture. Electrodes were inserted into the mixture under a nitrogen atmosphere. The reaction temperature was controlled at 25°C. A carbon cloth electrode (35 mm x 15 mm x 0.1 mm) was used as the positive electrode, and a platinum electrode (10 mm x 10 mm x 0.1 mm) was used as the negative electrode. The reaction was carried out without power for approximately 3 hours. Reaction progress was monitored by TLC (petroleum ether:ethyl acetate = 4:1), and no target product 2a was detected.

[0146] The present invention provides a method and concept for electrochemically synthesizing pyridine-fused polycyclic nitrogen heteroaromatic compounds. Numerous methods and approaches exist for implementing this technical solution. The foregoing merely represents a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A method for preparing a pyridine-fused polycyclic nitrogen heteroaromatic compound, characterized in that: Dissolving compound I, a quaternary ammonium salt, and a Lewis acid in an organic solvent to obtain a mixed solution; inserting an electrode into the mixed solution, connecting a constant current in an inert gas atmosphere, and stirring to perform an electric reaction to obtain a pyridine-fused polycyclic nitrogen heteroaromatic compound II; The structural formula of the compound I is shown in Formula I, and the structural formula of the pyridine-fused polycyclic nitrogen heteroaromatic compound II is shown in Formula II. The structural formulas of Formula I and Formula II are as follows: ； wherein R1 is selected from unsubstituted or substituted phenyl, pyridyl, thienyl or naphthyl; the substitution is selected from methyl, bromo, nitro, cyano, trifluoromethyl, methoxy or tert-butyloxycarbonylamino; R2 is selected from hydrogen, methyl, chloro or trifluoromethyl; The organic solvent is methanol, or a combination of methanol and other solvents.

2. The preparation method according to claim 1, characterized in that The quaternary ammonium salt is any one of tetrabutylammonium hexafluorophosphate, tetrabutylammonium acetate, tetrabutylammonium tetrafluoroborate and tetrabutylammonium iodide, or a combination thereof.

3. The preparation method according to claim 1, characterized in that The Lewis acid is any one of lanthanum trifluoromethanesulfonate, ytterbium trifluoromethanesulfonate, indium trifluoromethanesulfonate, bismuth trifluoromethanesulfonate and hafnium trifluoromethanesulfonate, or a combination thereof.

4. The preparation method according to claim 1, characterized in that The other solvents are any one or a combination of acetonitrile, ethanol, dimethyl sulfoxide, N,N-dimethylformamide, methyl tert-butyl ether, trifluoroethanol and hexafluoroisopropanol.

5. The preparation method according to claim 1, characterized in that In the mixed solution, the concentration of compound I is 0.025~0.0375 mmol / mL, the concentration of the quaternary ammonium salt is 0.05~0.075 mmol / mL, and the concentration of the Lewis acid is 0.005~0.0075 mmol / mL.

6. The preparation method according to claim 1, characterized in that The electrodes include a positive electrode which is a carbon cloth electrode, a carbon rod electrode, a foam carbon electrode or a platinum electrode, and a negative electrode which is an iron electrode, a nickel electrode or a platinum electrode.

7. The preparation method according to claim 1, characterized in that The constant current is 8-12 mA.

8. The preparation method according to claim 1, characterized in that The electroreaction has a reaction temperature of 20-50° C. and a reaction time of 3-5 h.

9. The preparation method according to claim 1, characterized in that The inert gas is N2.

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