Electrochemical synthesis of quinoline derivatives

Abstract

The application relates to the technical field of organic synthesis, in particular to an electrochemical synthesis method of quinoxaline derivatives. The method comprises the following steps: mixing a phenone compound, a 1,2-benzene diamine compound, an electrolyte, an iodine source, an acid and an organic solvent to obtain a reaction solution; and then performing electrochemical reaction on the reaction solution by electrification to prepare the quinoxaline derivative. According to the method, the metal catalyst is not needed, and the phenone substrate is only catalytically oxidized by using the electric induction cycle, and the by-product is hydrogen. The method has the characteristics of easy raw material acquisition and simple operation, and can efficiently, cleanly and cheaply prepare the quinoxaline derivative.

Description

Technical Field

[0001] This invention relates to the field of organic synthesis technology, and in particular to an electrochemical synthesis method for quinoxaline derivatives. Background Technology

[0002] Quinoxaline and its derivatives are an important class of nitrogen-containing heterocyclic structures found in many bioactive compounds and natural products. They also serve as the structural cores for numerous drugs, playing a crucial role in the design and synthesis of novel heterocyclic compounds. Furthermore, quinoxaline and its derivatives possess biological activity and properties, exhibiting antibacterial, anti-infective, anti-inflammatory, and antitumor effects. They also demonstrate multifunctionality in pharmacological research; for example, the anti-tuberculosis drugs rifampin and pyrazinamide, and the antibacterial drugs quinacrine and carbazoline are all quinoxaline derivatives.

[0003] Currently, the main methods for synthesizing quinoxaline and its derivatives include oxidative cyclization and catalytic cyclization reactions. In 2017, Professor Luo Sanzhong's team reported a method for synthesizing quinoxaline derivatives by cyclization reaction at 60℃ using 1,2-phenylenediamine and phenylethylamine as substrates, 4-methoxy-5-tert-butyl-o-quinone as catalyst, TsOH as additive, oxygen as oxidant, and acetonitrile as solvent (Zhang, R.; Qin, Y.; Zhang, L.; Luo, SZ. Oxidative Synthesis of Benzimidazoles, Quinoxalines, and Benzoxazoles from Primary Amines by ortho-Quinone Catalysis. Org Lett. 2017, 19, 5629-5632.). In 2020, Professor Zhang Luyong et al. first reported a method for synthesizing monosubstituted quinoxaline and its derivatives by using β-keto thiosulfonyl sulfoxide and 1,2-phenylenediamine in a tandem [4+2] cyclization reaction at 60 °C with (Cp*IrCl2)2 as catalyst, AgSbF6 as silver salt, NaHCO3 as additive, and DCM as solvent (Wang,XT.;Song,JL.;Zhong,M.;Kang,HJ.;Xie,H.,Che,T.;Shu,B.;Peng,D.;Zhang,L.;Zhang,SS. Iridium-Catalyzed[4+2] Annulations of β-Keto Sulfoxonium Ylides ando-Phenylenediamines: Mild and Facile Synthesis of Quinoxaline Derivatives. Eur J Org Chem. 2020, 3635-3639.).

[0004] In 2022, Professor Guo Xunxiang's team reported a method using 1,2-phenylenediamine and terminal alkynes as substrates, under CoBr2 catalysis, to add... A method for synthesizing quinoxaline and its derivatives by cyclization at 70 °C using MS, oxygen as the oxidant, and DCE as the solvent (Yang, HR.; Hu ZY.; Li, XC.; Wu, L.; Guo XX. Cobalt-Catalyzed Effective Access to Quinoxalines with Insights in Annulation of Terminal Alkynes and o-Phenylenediamines. Eur J Org Chem. 2020, 3635-3639.). In the same year, Nguyen, LA et al. reported a method for synthesizing quinoxaline compounds by cyclization at 110 °C using 1,2-phenylenediamine, acetophenone, α-tetrahydronaphthone, and phenylacetone as substrates, in the presence of S8, with acid as a catalyst and DMSO as a solvent (Nguyen, LA.; Nguyen, TTT.; Ngo, QA.; Nguyen, TB. Sulfur-Catalyzed Oxidative Condensation of Aryl Alkyl Ketones witho-Phenylenediamines: Access to Quinoxalines. Adv Synth Catal. 2022, 364, 2748-2752.). In 2023, Trayambek Nath Chaubey et al. reported a method for synthesizing quinoxaline compounds using various aryl / alkyl sulfoxide imides and 1,2-phenylenediamine as substrates in the presence of S8 and DMSO as solvent (Chaubey, TN.; Borpatra, PJ.; Pandey SK. Elemental Sulfur-Mediated Synthesis of Quinoxalines from Sulfoxonium Ylides. Org Lett. 2023, 25, 5329-5332).

[0005] Currently, although there are many methods for synthesizing quinoxaline, existing methods still suffer from drawbacks such as the need for metal catalysts and oxidants, harsh reaction conditions, and significant amounts of waste generated during the reaction process. Therefore, developing efficient, clean, and inexpensive synthetic methods for quinoxaline derivatives remains of paramount importance. Summary of the Invention

[0006] The purpose of this invention is to provide an electrochemical synthesis method for quinoxaline derivatives, enabling efficient, clean, and inexpensive preparation of quinoxaline derivatives.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] An electrochemical synthesis method for a quinoxaline derivative includes the following steps:

[0009] A acetophenone compound, a 1,2-phenylenediamine compound, an electrolyte, an iodine source, an acid, and an organic solvent are mixed to obtain a reaction solution.

[0010] The reaction solution was electrified to carry out an electrochemical reaction, and quinoxaline derivatives were obtained.

[0011] The structure of the acetophenone compound is as follows:

[0012] The structure of the 1,2-phenylenediamine compound shown is as follows:

[0013] The quinoxaline derivative has the structure shown in formula (I):

[0014]

[0015] Ar contains a benzene ring, a substituted benzene ring, a furan ring, or a naphthalene ring, and R... 1 It contains hydrogen or a benzene ring; R contains hydrogen, methyl or ester group.

[0016] Optionally, the substituents in the substituted benzene ring include alkyl, halogen, cyano, or ester groups.

[0017] Optionally, the acetophenone compound with the structure shown in formula (II) comprises at least one of acetophenone, p-methylacetophenone, p-iodoacetophenone, methyl p-acetylbenzoate, 2-acetylfuran, diacetophenone, 2,5-dimethylacetophenone, p-cyanoacetophenone, naphthylacetophenone, and m-chloroacetophenone.

[0018] Optionally, the 1,2-phenylenediamine compound with the structure shown in formula (III) comprises at least one of 1,2-phenylenediamine, 4,5-dimethyl-1,2-phenylenediamine, and ethyl 3,4-diaminobenzoate;

[0019] The molar ratio of acetophenone to 1,2-phenylenediamine is 1:1 to 1.5.

[0020] Optionally, the electrolyte comprises at least one of ammonium iodide, ammonium acetate, and tetrabutylammonium iodide;

[0021] The molar ratio of acetophenone compound to electrolyte is 1:0.5 to 1.0.

[0022] Optionally, the iodine source comprises at least one of potassium iodide and sodium iodide;

[0023] The molar ratio of acetophenone compound to iodine source is 1:1 to 1.3.

[0024] Optionally, the acid includes at least one of oxalic acid, formic acid, and trifluoroacetic acid, and the concentration of the acid in the reaction solution is 0.083–0.167 mol / L;

[0025] The molar ratio of acetophenone compound to acid is 1:1 to 2.

[0026] Optionally, the organic solvent includes N,N-dimethylacetamide or dimethyl sulfoxide;

[0027] The ratio of acetophenone compound to organic solvent is 0.5–1.0 mmol: 6–12 mL.

[0028] Optionally, the current of the electrochemical reaction is 10-15 mA, the temperature is 80-110 °C, and the time is 16-32 h.

[0029] In the electrochemical reaction described in this invention, a graphite felt connected to the positive electrode serves as the anode. Iodine ions in the reaction solution lose electrons at the anode and undergo an oxidation reaction to transform into iodine free radicals. A platinum / nickel electrode connected to the negative electrode serves as the cathode, where free H+ ions in the reaction solution... + At the cathode, electrons are gained, and a reduction reaction occurs to produce hydrogen gas. During the reaction, acetophenone compounds combine with iodine radicals to form 2-iodoacetophenone. Under the action of acid, 2-iodoacetophenone reacts with 1,2-phenylenediamine to form 2-((2-iodo-1-phenylethylene)amino)aniline containing an imine structure. Subsequently, it loses HI to undergo cyclization and further dehydrogenates to form a quinoxaline structure.

[0030] The electrochemical synthesis method for quinoxaline provided by this invention uses only electro-induced cyclic catalytic oxidation of acetophenone substrate with iodine, and the byproduct is hydrogen. This process does not use metal catalysts, strong oxidants, or other reagents, thus avoiding pollution from reagent use. Furthermore, the reaction media KI and NaI can be recycled and reused, resulting in almost zero emissions of waste, making it more environmentally friendly. With readily available raw materials, simple operation, and environmental friendliness, it has significant practical value and socio-economic benefits. Detailed Implementation

[0031] This invention provides an electrochemical synthesis method for quinoxaline derivatives, comprising the following steps:

[0032] A acetophenone compound, a 1,2-phenylenediamine compound, an electrolyte, an iodine source, an acid, and an organic solvent are mixed to obtain a reaction solution.

[0033] The reaction solution was electrified to carry out an electrochemical reaction, and quinoxaline derivatives were obtained.

[0034] The structure of the acetophenone compound is as follows:

[0035] The structure of the 1,2-phenylenediamine compound shown is as follows:

[0036] The quinoxaline derivative has the structure shown in formula (I):

[0037]

[0038] Ar contains a benzene ring, a substituted benzene ring, a furan ring, or a naphthalene ring, and R... 1 It contains hydrogen or a benzene ring; R contains hydrogen, methyl or ester group, and when R is an ester group, it is preferably an ethyl formate group.

[0039] In this invention, the substituents in the substituted benzene ring preferably include alkyl, halogen, cyano or ester groups, the alkyl group is preferably p-methyl or 2,5-dimethyl, the halogen is preferably iodine or chlorine, more preferably p-iodine or m-chlorine, the cyano group is preferably p-cyano, and the ester group is preferably methyl formate.

[0040] In this invention, the acetophenone compound with the structure shown in formula (II) preferably includes acetophenone, p-methylacetophenone, p-iodoacetophenone, methyl p-acetylbenzoate, 2-acetylfuran, diacetophenone, 2,5-dimethylacetophenone, p-cyanoacetophenone, naphthylacetophenone, or m-chloroacetophenone.

[0041] In this invention, the 1,2-phenylenediamine compound with the structure shown in formula (III) preferably contains 1,2-phenylenediamine, 4,5-dimethyl-1,2-phenylenediamine or ethyl 3,4-diaminobenzoate.

[0042] The molar ratio of acetophenone compound to 1,2-phenylenediamine compound is preferably 1:1 to 1.5, more preferably 1:1.2 to 1.5, and even more preferably 1:1.4 to 1.5.

[0043] In this invention, the electrolyte preferably comprises ammonium iodide, ammonium acetate, or tetrabutylammonium iodide;

[0044] The molar ratio of acetophenone compound to electrolyte is preferably 1:0.5 to 1.0, more preferably 1:0.5 to 0.75, and even more preferably 1:0.5 to 0.6.

[0045] In this invention, the iodine source is preferably potassium iodide or sodium iodide;

[0046] The molar ratio of acetophenone compound to iodine source is preferably 1:1 to 1.3, more preferably 1:1.1 to 1.3, and even more preferably 1:1.2 to 1.3.

[0047] In this invention, the acid preferably includes at least one of oxalic acid, formic acid, and trifluoroacetic acid, and the concentration of the acid in the reaction solution is 0.083 to 0.167 mol / L;

[0048] The molar ratio of acetophenone compound to acid is preferably 1:1 to 2, more preferably 1:1 to 1.5, and even more preferably 1:1 to 1.2.

[0049] In this invention, the organic solvent preferably includes N,N-dimethylacetamide (DMA) or dimethyl sulfoxide (DMSO);

[0050] The preferred ratio of acetophenone compound to organic solvent is 0.5–1.0 mmol: 6–12 mL, more preferably 0.5–0.8 mmol: 6–10 mL, and even more preferably 0.5–0.75 mmol: 6–8 mL.

[0051] In this invention, it is preferable to place a graphite felt electrode and a platinum electrode, or a graphite felt electrode and a nickel foam electrode, in the reaction solution before the electrochemical reaction begins.

[0052] In this invention, the general reaction formula for the electrochemical synthesis is:

[0053]

[0054] In this invention, the current of the electrochemical reaction is preferably 10-15 mA, more preferably 12-15 mA, and even more preferably 14-15 mA;

[0055] The preferred temperature is 80–110°C, more preferably 90–110°C, and even more preferably 100–110°C;

[0056] The preferred time is 16 to 32 hours, more preferably 18 to 30 hours, and even more preferably 20 to 24 hours.

[0057] In this invention, after the electrochemical reaction is completed, the preferred steps are to sequentially cool, wash the graphite felt electrode and combine the washing solutions, microwave sonicate the graphite felt electrode in the washing solution, combine the reaction solution and the washing solution after microwave sonication, extract and retain the organic phase, wash the organic phase, dry the organic phase, evaporate under reduced pressure, elute, and separate by column chromatography to obtain the quinoxaline derivative.

[0058] The preferred method for washing the graphite felt electrode is to wash it three times with ethyl acetate, and the amount of ethyl acetate used in the washing process is adjusted according to actual needs.

[0059] The preferred extraction method involves extracting three times each with ethyl acetate and water, with the amounts of ethyl acetate and water used adjusted according to actual needs during the extraction process.

[0060] The washing organic phase is preferably washed once with saturated brine, and the amount of saturated brine is adjusted according to actual needs;

[0061] The dried organic phase is preferably dried using anhydrous sodium sulfate.

[0062] The temperature for vacuum distillation is preferably 40–55°C, more preferably 45–50°C; the time is preferably 30–45 min, more preferably 35–40 min.

[0063] The elution is preferably carried out using a mixture of petroleum ether and ethyl acetate as the eluent, and the ratio and amount of petroleum ether and ethyl acetate are adjusted according to actual needs.

[0064] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0065] Example 1

[0066] Acetophenone (60 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMSO (6 mL) were mixed to form a reaction solution. Graphite felt and platinum electrodes were then inserted into the reaction solution, and the current was adjusted to a constant 15 mA. The reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). Afterwards, the graphite felt electrode was washed three times with ethyl acetate. The washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution was combined with the microwaved washing solution, and extracted three times sequentially with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate (volume ratio 100:3) was used as the eluent. Separation by silica gel column chromatography yielded 70 mg of a yellow solid, with a yield of 68%. This yellow solid is the quinoxaline derivative 2-phenylquinoxaline (Ia), and its structural formula is:

[0067]

[0068] 1H NMR (600MHz, Chloroform-d) δ9.33 (s, 1H), 8.22-8.19 (m, 2H), 8.15 (ddd, J = 22. 2,8.4,1.8Hz,2H),7.77(dddd,J=23.4,8.4,7.2,1.2Hz,2H),7.59-7.52(m,3H).

[0069] 13 C NMR (150MHz, Chloroform-d) δ152.23,143.66,142.66,141.85,137.10,130.69,130.57,129.97,129.94,129.53,129.43,127.92.

[0070] HRMS(ESI)calcd for C 14 H 10 N2[M+H] + :207.0917,found:207.0911.

[0071] Example 2

[0072] Acetophenone (60 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), ammonium iodide (36 mg, 0.25 mmol), and DMA (6 mL) were mixed to form a reaction solution. Graphite felt and platinum electrodes were then inserted into the reaction solution, and the current was adjusted to a constant 15 mA. The reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrode was then washed with ethyl acetate. The washing solutions were combined three times, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3 was used as the eluent. The solid was separated by silica gel column chromatography to obtain 68 mg of yellow solid, with a yield of 66%. This yellow solid was the quinoxaline derivative 2-phenylquinoxaline (Ia).

[0073] Example 3

[0074] A acetophenone (60 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), ammonium acetate (19 mg, 0.25 mmol), and DMA (6 mL) were mixed to form a reaction solution. Graphite felt and platinum electrodes were then inserted into the reaction solution, and the current was adjusted to a constant 15 mA. The reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrode was then washed with ethyl acetate. The washing solutions were combined three times, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3 was used as the eluent. The solid was separated by silica gel column chromatography to obtain 67 mg of yellow solid, with a yield of 65%. This yellow solid was the quinoxaline derivative 2-phenylquinoxaline (Ia).

[0075] Example 4

[0076] Acetophenone (60 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMSO (6 mL) were mixed to form a reaction solution. Graphite felt and platinum electrodes were then inserted into the reaction solution, and the current was adjusted to a constant 15 mA. The reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite was then washed with ethyl acetate. The graphite felt electrode was subjected to three extractions. The washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution was combined with the washing solution after microwave sonication, and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and then dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, it was eluted with a mixture of petroleum ether and ethyl acetate at a volume ratio of 100:3. The solid was separated by silica gel column chromatography to obtain 69 mg of yellow solid, with a yield of 67%. This yellow solid was the quinoxaline derivative 2-phenylquinoxaline (Ia).

[0077] Example 5

[0078] Acetophenone (60 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL) were mixed to form a reaction solution. Graphite felt and platinum electrodes were then inserted into the reaction solution, and the current was adjusted to a constant 13 mA. The reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt was then washed with ethyl acetate. The electrode was subjected to three extractions. The washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution was combined with the washing solution after microwave sonication, and extracted three times with ethyl acetate and water in sequence. The organic phase was retained, washed once with saturated brine, and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3 was used as the eluent for elution. Separation by silica gel column chromatography yielded 67 mg of yellow solid, with a yield of 65%. This yellow solid was the quinoxaline derivative 2-phenylquinoxaline (Ia).

[0079] Example 6

[0080] Acetophenone (60 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL) were mixed to form a reaction solution. Graphite felt and platinum electrodes were then inserted into the reaction solution, and the current was adjusted to a constant 14 mA. The reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt was then washed with ethyl acetate. The electrode was subjected to three extractions. The washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution was combined with the washing solution after microwave sonication, and extracted three times with ethyl acetate and water in sequence. The organic phase was retained, washed once with saturated brine, and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3 was used as the eluent for elution. Separation by silica gel column chromatography yielded 67 mg of yellow solid, with a yield of 65%. This yellow solid was the quinoxaline derivative 2-phenylquinoxaline (Ia).

[0081] Example 7

[0082] Acetophenone (60 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), CF3COOH (57 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL) were mixed to form a reaction solution. Graphite felt and platinum electrodes were then inserted into the reaction solution, and the current was adjusted to a constant 15 mA. The reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrode was then washed with ethyl acetate. The washing solutions were combined three times, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3 was used as the eluent. The solid was separated by silica gel column chromatography to obtain 64 mg of yellow solid, with a yield of 63%. This yellow solid was the quinoxaline derivative 2-phenylquinoxaline (Ia).

[0083] Example 8

[0084] Acetophenone (60 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), formic acid (23 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL) were mixed to form a reaction solution. Graphite felt and platinum electrodes were then inserted into the reaction solution, and the current was adjusted to a constant 15 mA. The reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrode was then washed three times with ethyl acetate. The washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3 was used as the eluent. The solid was separated by silica gel column chromatography to obtain 69 mg of yellow solid, with a yield of 67%. This yellow solid was the quinoxaline derivative 2-phenylquinoxaline (Ia).

[0085] Example 9

[0086] A reaction solution was prepared by mixing p-methylacetophenone (67 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed with ethyl acetate. Next, the washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined, and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3 was used as the eluent. Separation by silica gel column chromatography yielded 72 mg of a yellow solid, with a yield of 65%. This yellow solid is the quinoxaline derivative 2-(p-tolyl)quinoxaline (Ib), and its structural formula is:

[0087]

[0088] 1 HNMR (600MHz, Chloroform-d) δ9.32 (s, 1H), 8.18-8.09 (m, 4H), 7.76 (dddd, J = 27.0, 8.4, 6.8, 1.2Hz, 2H), 7.38 (d, J = 7.8Hz, 2H), 2.46 (s, 3H).

[0089] 13 CNMR(150MHz,Chloroform-d)δ151.80,143.08,142.25,141.16,140.56,133.80,130.26,129.87,129.44,129.36,128.91,127.40,21.37.

[0090] HRMS(ESI)calcd for C 15 H 12 N2[M+H] + :221.1074,found:221.1067.

[0091] Example 10

[0092] A reaction solution was prepared by mixing p-iodoacetophenone (123 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed with ethyl acetate. Next, the washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined, and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3 was used as the eluent. Separation by silica gel column chromatography yielded 75 mg of a yellow solid, with a yield of 45%. This yellow solid is the quinoxaline derivative 2-(4-iodophenyl)quinoxaline (Ic), and its structural formula is:

[0093]

[0094] 1 HNMR(600MHz,Chloroform-d)δ9.29(s,1H),8.17-8.10(m,2H),7.96-7.93(m,2H),7.92-7.88(m,2H),7.78(dddd,J=19.8,8.4,6.6,1.8Hz,2H).

[0095] 13 CNMR(150MHz,Chloroform-d)δ151.1,143.0,142.6,142.0,138.7,136.5,130.9,130.2,130.0,129.5,129.4,97.4.

[0096] HRMS(ESI+)calcd for C 14 H9IN2[M+H] + :331.9810,found:331.9778.

[0097] Example 11

[0098] A reaction solution was prepared by mixing methyl acetylbenzoate (89 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was completed, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed with ethyl acetate. Next, the washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined, and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 35:1 was used as the eluent. Separation by silica gel column chromatography yielded 74 mg of a yellow solid, with a yield of 56%. This yellow solid is the quinoxaline derivative methyl 4-(quinoxaline-2-yl)benzoate (Id), and its structural formula is:

[0099]

[0100] 1 HNMR(600MHz,Chloroform-d)δ9.37(s,1H),8.31-8.28(m,2H),8.25-8.22(m, 2H),8.20-8.14(m,2H),7.81(dddd,J=18.0,8.4,7.2,1.8Hz,2H),3.98(s,3H).

[0101] 13 CNMR(150MHz,Chloroform-d)δ166.81,150.82,143.27,142.44,141.95,140.95,131.61,130.77,130.51,130.33,129.92,129.32,127.65,52.51.

[0102] HRMS(ESI+)calcd for C 16 H 12 N₂O₂[M+H] + :265.0972,found:265.0978.

[0103] Example 12

[0104] A reaction solution was prepared by mixing p-2-acetylfuran (55 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (30 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed with ethyl acetate. The washing solutions were combined three times, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution was combined with the microwaved washing solution, and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 30:1 was used as the eluent. Separation by silica gel column chromatography yielded 52 mg of yellow solid, with a yield of 53%. This yellow solid is the quinoxaline derivative 2-(furan-2-yl)quinoxaline (Ie), and its structural formula is:

[0105]

[0106] 1 HNMR(600MHz,Chloroform-d)δ9.24(d,J=2.4Hz,1H),8.08(ddd,J=19.8,8.4,1.8Hz,2H),7.75(d dq,J=8.4,6.6,1.2Hz,1H),7.72-7.67(m,2H),7.32(t,J=3.0Hz,1H),6.63(dt,J=3.0,1.8Hz,1H).

[0107] 13 CNMR(150MHz,Chloroform-d)δ151.49,145.05,143.75,142.01,141.96,141.19,130.42,129.27,129.13,112.44,111.78.

[0108] HRMS(ESI+)calcd for C 16 H 14 N2[M+H] + :197.0710,found:197.0723.

[0109] Example 13

[0110] Acetophenone (60 mg, 0.5 mmol), 4,5-dimethyl-1,2-phenylenediamine (102 mg, 0.75 mmol), C2H2O4·2H2O (30 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL) were mixed to form a reaction solution. Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed with ethyl acetate. The washing solutions were combined three times, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution was then combined with the microwaved washing solution, and extracted three times sequentially with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was then distilled under reduced pressure at 45 °C for 30 min to remove the solvent. The solution was then eluted with a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3. Separation by silica gel column chromatography yielded 83 mg of a yellow solid, with a yield of 71%. This yellow solid was the quinoxaline derivative 6,7-dimethyl-2-phenylquinoxaline (If), with the following structural formula:

[0111]

[0112] 1 HNMR(600MHz,Chloroform-d)δ9.23(s,1H),8.18-8.16(m,2H),7.93(s,1H),7.89(s,1H),7.58-7.50(m,4H),2.52(s,6H).

[0113] 13 CNMR(150MHz,Chloroform-d)δ151.45,142.25,141.68,141.52,140.90,137.28,130.35,129.49,128.98,128.16,127.78,20.78,20.74.

[0114] HRMS(ESI+)calcd for C 16 H 14 N2[M+H] + :235.1230,found:235.1219.

[0115] Example 14

[0116] A reaction solution was prepared by mixing phenylethyl ketone (98 mg, 0.5 mmol), 4,5-dimethyl-1,2-phenylenediamine (102 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed with ethyl acetate. The washing solutions were combined three times, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution was then combined with the microwaved washing solution, and extracted three times sequentially with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. The solution was then eluted with a mixture of petroleum ether and ethyl acetate at a volume ratio of 50:1. Separation by silica gel column chromatography yielded 81 mg of a yellow solid, with a yield of 52%. This yellow solid was the quinoxaline derivative 6,7-dimethyl-2,3-diphenylquinoxaline (Ig), with the following structural formula:

[0117]

[0118] 1 HNMR (600MHz, Chloroform-d) δ7.95 (s, 2H), 7.50 (dd, J = 7.8, 1.2Hz, 4H), 7.36-7.31 (m, 6H), 2.52 (s, 6H).

[0119] 13 CNMR(150MHz,Chloroform-d)δ152.57,140.86,140.23,139.31,130.01,128.76,128.36,128.25,20.60.

[0120] HRMS(ESI+)calcd for C 22 H 18 N2[M+H] + :311.1543,found:311.1529.

[0121] Example 15

[0122] A reaction solution was prepared by mixing phenylethyl ketone (98 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed with ethyl acetate. Next, the washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined, and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate at a volume ratio of 50:1 was used as the eluent. Separation by silica gel column chromatography yielded 65 mg of yellow solid, with a yield of 46%. This yellow solid is the quinoxaline derivative 2,3-diphenylquinoxaline (Ih), and its structural formula is:

[0123]

[0124] 1 H NMR (600MHz, Chloroform-d) δ7.95 (s, 2H), 7.50 (dd, J = 7.8, 1.2Hz, 4H), 7.36-7.31 (m, 6H), 2.52 (s, 6H).

[0125] 13 C NMR (150MHz, Chloroform-d) δ152.57,140.86,140.23,139.31,130.01,128.76,128.36,128.25,20.60.

[0126] HRMS(ESI+)calcd for C 20 H 14 N2[M+H] + :283.1230,found:283.1219.

[0127] Example 16

[0128] A reaction solution was prepared by mixing 2,5-dimethylacetophenone (74 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrode was then washed with ethyl acetate. The reaction mixture was subjected to three extractions. The washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution was then combined with the microwaved washing solution and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. The solvent was then removed by elution with a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3. Separation by silica gel column chromatography yielded 61 mg of a yellow solid, with a yield of 52%. This yellow solid was the quinoxaline derivative 2-(3-chlorophenyl)quinoxaline (Ii), and its structural formula is:

[0129]

[0130] 1 H NMR(600MHz,Chloroform-d)δ8.89(s,1H),8.05(ddd,J=7.2,4.8,2.4Hz,2H),7.69(tt,J=7.2,5.4Hz, 2H),7.26(d,J=2.4Hz,1H),7.14(d,J=7.2Hz,1H),7.10(dd,J=7.8,2.4Hz,1H),2.30(d,J=5.4Hz,6H).

[0131] 13 C NMR (150MHz, Chloroform-d) δ155.1,145.9,142.0,140.9,136.9,135.8,133.3,131.1,130.5,130.2,130.1,129.6,129.5,129.1,20.9,19.8.

[0132] HRMS(ESI+)calcd for C 16 H 14 N2[M+H] + :235.1230,found:235.1222.

[0133] Example 17

[0134] A reaction solution was prepared by mixing p-cyanoacetophenone (74 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was completed, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed three times with ethyl acetate. The washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined, and the mixture was extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. The solvent was then eluted with a mixture of petroleum ether and ethyl acetate in a volume ratio of 100:3. The solid was separated by silica gel column chromatography to obtain 41 mg of yellow solid, with a yield of 35%. This yellow solid is the quinoxaline derivative 4-(quinoxaline-2-yl)benzonitrile (Ij), and its structural formula is:

[0135]

[0136] 1 H NMR (600MHz, Chloroform-d) δ9.35 (s, 1H), 8.36-8.33 (m, 2H), 8.17 (tt, J = 8.4, 1.8Hz, 2H), 7.88-7.80 (m, 4H).

[0137] 13 C NMR (150MHz, Chloroform-d) δ149.5,142.7,142.2,141.9,140.8,132.8,130.8,130.5,129.7,129.2,128.0,118.4,113.6.

[0138] HRMS(ESI+)calcd for C 15 H9N3[M+H]+:232.2870,found:232.2866.

[0139] Example 18

[0140] A reaction solution was prepared by mixing naphthyl ethyl ketone (85 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), C2H2O4·2H2O (63 mg, 0.5 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were then washed three times with ethyl acetate. The washing solutions were combined, and the graphite felt electrode was immersed in the washing solution and microwaved for 5 min. The reaction solution and the microwaved washing solution were combined, and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 35:1 was used as the eluent. Separation by silica gel column chromatography yielded 60 mg of a yellow solid, with a yield of 47%. This yellow solid is the quinoxaline derivative 2-(naphth-2-yl)quinoxaline (Ik), and its structural formula is:

[0141]

[0142] 1 H NMR(600MHz,Chloroform-d)δ9.48(s,1H),8.66(d,J=1.8Hz,1H),8.36(dd,J=8.4,1.8Hz,1H),8.21(dd,J=8.4,1.8Hz,1H),8.15(dd,J=8.4 ,1.8Hz,1H),8.04-8.01(m,2H),7.92-7.89(m,1H),7.81(ddd,J=8.4,6.8,1.8Hz,1H),7.76(ddd,J=8.4,6.8,1.8Hz,1H),7.59-7.55(m,2H).

[0143] 13 C NMR(150MHz,Chloroform-d)δ151.64,143.32,142.32,141.35,134.07,133.93,133.3 0,130.34,129.56,129.54,129.00,128.84,127.74,127.44,127.26,126.63,124.39.

[0144] HRMS(ESI+)calcd for C 18 H 16N₂O₂[M+H] + :257.1074,found:257.1061.

[0145] Example 19

[0146] A reaction solution was prepared by mixing p-methylacetophenone (67 mg, 0.5 mmol), ethyl 3,4-diaminobenzoate (135 mg, 0.75 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). A graphite felt electrode and a nickel foam electrode were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was completed, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrode was washed three times with ethyl acetate, and the washings were combined. The electrode was immersed in washing solution and microwaved for 5 min. The reaction solution and the washing solution after microwave sonication were combined and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate in a volume ratio of 35:1 was used as the eluent. Separation by silica gel column chromatography yielded 63 mg of a yellow solid, with a yield of 43%. This yellow solid was the quinoxaline derivative 2-(p-tolyl)quinoxaline-6-carboxylic acid ethyl ester (Im), and its structural formula is:

[0147]

[0148] 1 H NMR(600MHz,Chloroform-d)δ9.42-9.35(m,1H),8.93-8.79(m,1H),8.39-8.30(m,1H),8.19-8.1 1(m,3H),7.39(d,J=7.8Hz,2H),4.48(qd,J=7.2,0.6Hz,2H),2.46(s,3H),1.47(t,J=7.2Hz,3H).

[0149] 13 C NMR(150MHz,Chloroform-d)δ165.8,153.1,152.5,144.8,144.3,144.1,143.2,141.2,141.0,140.5,133.3,132 .0,131.9,131.6,130.8,130.0,129.9,129.8,129.6,129.2,128.8,127.6,127.4,61.5,61.5,21.4,21.4,14.3.

[0150] HRMS(ESI+)calcd for C 18 H 16 N₂O₂[M+H] + :293.1285,found:293.1277.

[0151] Example 20

[0152] A reaction solution was prepared by mixing m-chloroacetophenone (77 mg, 0.5 mmol), 1,2-phenylenediamine (81 mg, 0.75 mmol), potassium iodide (108 mg, 0.65 mmol), tetrabutylammonium iodide (92 mg, 0.25 mmol), and DMA (6 mL). Graphite felt electrodes and nickel foam electrodes were then inserted into the reaction solution. The current was adjusted to a constant 15 mA, and the reaction was stirred at 110 °C for 20 h. After the reaction was complete, heating was stopped, and the reaction solution was allowed to cool to room temperature (25 °C). The graphite felt electrodes were washed three times with ethyl acetate, and the washings were combined. The electrode was immersed in washing solution and microwaved for 5 min. The reaction solution and the washing solution after microwave sonication were combined and extracted three times with ethyl acetate and water, retaining the organic phase. The organic phase was washed once with saturated brine and dried with anhydrous sodium sulfate. The dried organic phase was distilled under reduced pressure at 45 °C for 30 min to remove the solvent. Then, a mixture of petroleum ether and ethyl acetate at a volume ratio of 35:1 was used as the eluent. Separation by silica gel column chromatography yielded 63 mg of a yellow solid, with a yield of 43%. This yellow solid was the quinoxaline derivative 2-(3-chlorophenyl)quinoxaline (In), and its structural formula is:

[0153]

[0154] 1 H NMR (600MHz, Chloroform-d) δ9.30 (s, 1H), 8.24 (q, J = 1.5Hz, 1H), 8.15 (ddd, J = 15.0, 8.4, 1. 8Hz,2H),8.07(ddd,J=6.8,3.6,1.8Hz,1H),7.84-7.76(m,2H),7.50(dd,J=3.6,1.8Hz,2H).

[0155] 13 C NMR (150MHz, Chloroform-d)150.3,142.8,142.2,141.7,138.4,135.3,130.5,130.3,130.2,130.0,129.6,129.1,127.6,125.5.

[0156] HRMS(ESI+)calcd for C 18 H 16 N₂O₂[M+H] + :241.0528,found:241.0513.

[0157] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An electrochemical synthesis method for a quinoxaline derivative, characterized in that, Includes the following steps: A acetophenone compound, a 1,2-phenylenediamine compound, an electrolyte, an iodine source, an acid, and an organic solvent are mixed to obtain a reaction solution. The reaction solution was electrified to carry out an electrochemical reaction, and quinoxaline derivatives were obtained. The structure of the acetophenone compound is as follows: The structure of the 1,2-phenylenediamine compound shown is as follows: The quinoxaline derivative has the structure shown in formula (I): Wherein, Ar is a benzene ring, a substituted benzene ring, a furan ring, or a naphthalene ring, and R... 1 R is hydrogen or a benzene ring; R is hydrogen, methyl or ester group; the substituent in the substituted benzene ring is alkyl, halogen, cyano or ester group; The electrolyte is at least one of ammonium iodide, ammonium acetate, and tetrabutylammonium iodide; The iodine source is at least one of potassium iodide and sodium iodide.

2. The electrochemical synthesis method according to claim 1, characterized in that, The acetophenone compound with the structure shown in formula (II) is at least one of acetophenone, p-methylacetophenone, p-iodoacetophenone, methyl p-acetylbenzoate, 2-acetylfuran, diacetophenone, 2,5-dimethylacetophenone, p-cyanoacetophenone, naphthylacetophenone, and m-chloroacetophenone.

3. The electrochemical synthesis method according to claim 1, characterized in that, The 1,2-phenylenediamine compound with the structure shown in formula (III) is at least one of 1,2-phenylenediamine, 4,5-dimethyl-1,2-phenylenediamine, and ethyl 3,4-diaminobenzoate; The molar ratio of the acetophenone compound to the 1,2-phenylenediamine compound is 1:1 to 1.

5.

4. The electrochemical synthesis method according to claim 1, characterized in that, The molar ratio of the acetophenone compound to the electrolyte is 1:0.5 to 1.

0.

5. The electrochemical synthesis method according to claim 1, characterized in that, The molar ratio of the acetophenone compound to the iodine source is 1:1 to 1.

3.

6. The electrochemical synthesis method according to claim 1, characterized in that, The acid is at least one of oxalic acid, formic acid, and trifluoroacetic acid, and the concentration of the acid in the reaction solution is 0.083–0.167 mol / L; The molar ratio of the acetophenone compound to the acid is 1:1 to 2.

7. The electrochemical synthesis method according to claim 1, characterized in that, The organic solvent is N,N-dimethylacetamide or dimethyl sulfoxide; The ratio of the acetophenone compound to the organic solvent is 0.5–1.0 mmol: 6–12 mL.

8. The electrochemical synthesis method according to claim 1, characterized in that, The electrochemical reaction is carried out at a current of 10–15 mA, a temperature of 80–110 °C, and a time of 16–32 h.

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