Method for preparing diphenyl hydrazine or 2H-indazole compound by using azobenzene compound

Abstract

The invention belongs to the technical field of preparation of organic compounds, and particularly relates to a method for preparing diphenyl hydrazine or 2H-indazole compounds by using an azobenzene compound. The method comprises the following steps: mixing an azobenzene compound, bi-boric acid ester, water and an organic solvent, and reacting to prepare the 2H-indazole compound, the reaction is carried out under visible light; the reaction time is less than 2 hours; the azobenzene compound is selected from any one of the following components: # imgabs0 #, the azobenzene compound is used as a raw material, water is used as a hydrogen source, the bis (borate) is added, the reaction is carried out under visible light irradiation in the absence of a metal catalyst, and the 2H-indazole compound product with the yield not lower than 70% can be prepared after the reaction time is shorter than 1 hour. Moreover, the method disclosed by the invention shows wide functional group compatibility, so that various types of azobenzene compounds can be converted into 2H-indazole compounds.

Description

[0001] This application is a divisional application of an application with an application date of December 02, 2022, application number 202211535667.2, and invention name “Method for preparing diphenylhydrazine or 2H-indazole compounds using azobenzene compounds”. Technical Field

[0002] The invention belongs to the technical field of organic compound preparation, and particularly relates to a method for preparing diphenylhydrazine or 2H-indazole compounds by utilizing azobenzene compounds. Background Art

[0003] As important organic chemical raw materials, diphenylhydrazine and 2H-indazole compounds are widely used in the synthesis of various fine chemical products such as organic dyes, pigments, pesticides, medicines, functional materials, etc. At present, the methods for preparing diphenylhydrazine compounds are mainly the following: (1) reduction method of azobenzene or azobenzene oxide compounds; (2) transition metal reduction method of nitro or nitrosobenzene; (3) oxidation method of aromatic amine compounds; (4) phenylhydrazine substitution of halogenated aromatic hydrocarbons; (5) oxidation method of aromatic hydroxylamine compounds. The methods for preparing 2H-indazole compounds are mainly the following: (1) cross-coupling method of ortho-halogen-substituted benzaldehyde and phenylhydrazine; (2) 1,3-dipolar cycloaddition method of diazo compounds; (3) CH bond amination synthesis method of phenylhydrazone.

[0004] There are many existing methods for preparing diphenylhydrazine compounds, and traditional laboratory and industrial preparation methods are mostly based on aryl nitro compounds as raw materials, and reduced with zinc powder in a strong alkaline medium. This type of traditional method requires the use of a large amount of organic transition metals as catalysts, in the presence of an excess of strong base, using alcohol as a hydrogen source, reacting at a relatively high temperature, and requiring a reaction time of more than 12 hours, so the substrate has a narrow scope of application. There are attempts in the prior art to prepare diphenylhydrazine compounds without using metal catalysts, but it is often necessary to heat to a relatively high temperature, and the reaction is up to 24 hours, or even longer reaction time, in order to obtain diphenylhydrazine compounds. In the past, there were many methods reported to synthesize 2H-indazole compounds, which generally required the use of noble metal catalysis or required expensive ligands, and this type of method is not only environmentally unfriendly, but also has a relatively high cost and is difficult to apply to industrial production. There are also attempts to synthesize 2H-indazole compounds using non-metallic catalysis methods, but a large amount of additives are usually used to assist the reaction, which does not meet the requirements of atom economy.

[0005] Therefore, there is an urgent need to provide a new method for preparing diphenylhydrazine and 2H-indazole compounds, which method not only does not require the use of a metal catalyst, but also does not require heating, has a short reaction time (less than 24 hours) and a high product yield. Summary of the invention

[0006] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a method for preparing diphenylhydrazine or 2H-indazole compounds using azobenzene compounds. The method of the present invention not only does not require the use of a metal catalyst, but also does not require heating. Under normal temperature conditions, only visible light illumination is required, the reaction time is short (less than 24 hours, even less than 2 hours or 1 hour), and the product yield is high.

[0007] The inventive concept of the present invention is: the present invention uses an azobenzene compound as a raw material, uses water as a hydrogen source, adds a diphenylhydrazine ester, and in the absence of a metal catalyst, under visible light (preferably 400nm-500nm) illumination, after a reaction time of less than 1 hour, a diphenylhydrazine or 2H-indazole compound product with a yield of not less than 70% can be prepared. In addition, the method of the present invention exhibits a wide range of functional group compatibility, so that various types of azobenzene compounds can be converted into diphenylhydrazine or 2H-indazole compounds.

[0008] The first aspect of the present invention provides a method for preparing diphenylhydrazine or 2H-indazole compounds using azobenzene compounds.

[0009] Specifically, the method for preparing diphenylhydrazine or 2H-indazole compounds using azobenzene compounds comprises the following steps:

[0010] Mixing an azobenzene compound, a diboric acid ester, water and an organic solvent, and reacting them to obtain the diphenylhydrazine or 2H-indazole compound;

[0011] The reaction is carried out under visible light;

[0012] The reaction time is less than 2 hours.

[0013] Preferably, the reaction is carried out under 400nm-500nm light; further preferably, the reaction is carried out under 400nm-450nm light.

[0014] Preferably, the reaction time is less than 1 hour; further preferably, the reaction time is 30 minutes to 1 hour.

[0015] Preferably, the azobenzene compound has the general structural formula of Ar 1 -N=N-Ar 2 , among which Ar 1 and Ar 2 Each independently represents an aryl group or a substituted aryl group.

[0016] Preferably, the aryl group is an aromatic ring with 6-16 carbon atoms; further preferably, the aryl group is an aromatic ring with 6-10 carbon atoms.

[0017] More preferably, the aryl group is selected from at least one of phenyl and naphthyl.

[0018] Preferably, the substituted aryl group carries one or more substituent groups (the multiple substituent groups here refer to two or more substituent groups. When there are multiple substituent groups, the multiple substituent groups may be the same or different), and the substituent groups are selected from at least one of alkyl, alkenyl, alkynyl, aryl, halide, nitro, alkoxy, ester, sulfonamide, cyano, carbonyl and trifluoromethyl.

[0019] Preferably, the carbon number of the alkyl group or alkoxy group is 1-15; further preferably, the carbon number of the alkyl group or alkoxy group is 2-8.

[0020] Preferably, the azobenzene compound is selected from any one of the following:

[0021]

[0022] Preferably, the diphenylhydrazine compound is selected from any one of the following:

[0023]

[0024] Preferably, the 2H-indazole compound is selected from any one of the following:

[0025]

[0026] Preferably, the biboric acid ester is selected from bis( ...

[0027] The structure is

[0028] Preferably, the organic solvent is selected from at least one of tetrahydrofuran (THF), acetonitrile (MeCN), methanol (MeOH) or dichloromethane (DCM); further preferably, the organic solvent is tetrahydrofuran (THF).

[0029] Preferably, the molar ratio of the azobenzene compound, the diboric acid ester and water is 1:(0.5-5):(10-100); more preferably, the molar ratio of the azobenzene compound, the diboric acid ester and water is 1:(1-1.5):(10-50).

[0030] Preferably, the ratio of the azobenzene compound to the organic solvent is 0.1 mmol: 0.5-5 mL; preferably 0.1 mmol: 0.5-1 mL.

[0031] Preferably, the mixing process is that the components are mixed simultaneously or in steps.

[0032] Preferably, the reaction is carried out under closed conditions and an inert atmosphere (eg, nitrogen or argon) by mixing the components and irradiating with light.

[0033] Preferably, after the reaction is completed, the organic solvent is removed and the diphenylhydrazine or 2H-indazole compound is separated.

[0034] Preferably, the organic solvent is removed by rotary evaporation.

[0035] Preferably, the diphenylhydrazine or 2H-indazole compound is separated by column chromatography or high performance liquid chromatography.

[0036] The second aspect of the present invention is the application of the above method.

[0037] Specifically, the above method is applied in the field of organic synthesis.

[0038] Preferably, the organic synthesis field includes the field of synthesis of organic dyes, pigments, pesticides, medicines or functional materials.

[0039] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0040] The invention uses an azobenzene compound as a raw material, water as a hydrogen source, and a diboric acid ester, and is carried out under visible light irradiation without a metal catalyst. After a reaction time of less than 1 hour, a diphenylhydrazine or 2H-indazole compound product with a yield of not less than 70% can be prepared. In addition, the method of the invention exhibits a wide range of functional group compatibility, so that various types of azobenzene compounds can be converted into diphenylhydrazine or 2H-indazole compounds. DETAILED DESCRIPTION

[0041] In order to make the technical scheme of the present invention more clearly understood by those skilled in the art, the following embodiments are listed for illustration. It should be pointed out that the following embodiments do not limit the protection scope of the present invention.

[0042] Unless otherwise specified, the raw materials, reagents or devices used in the following examples can be obtained from conventional commercial sources or by existing known methods.

[0043] Example 1: Preparation of 1,2-diphenylhydrazine

[0044] The reaction equation involved in the preparation of 1,2-diphenylhydrazine (only the target product is reflected in the reaction equation) is as follows:

[0045]

[0046] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0047] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(cyclopentyl)benzene) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of azobenzene and 0.1 mL of water were added to a 10 mL quartz test tube equipped with a stirrer in sequence and mixed to obtain a mixture. The sealed test tube was taken out from the glove box, stirred and reacted under 450 nm light for 30 minutes, and then the organic solvent was removed under reduced pressure. The product was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1), and the product 1,2-diphenylhydrazine was separated. The yield of 1,2-diphenylhydrazine was 92.0%.

[0048] The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization results of the product obtained in this Example 1 are as follows: 1 H-NMR (CDCl3, 400MHz) δ (ppm) 7.26-7.22 (t, 4H), 6.89 -6.87 (m, 6H), 5.63 (s, 2H); 13 C-NMR (CDCl3, 125MHz) δ (ppm) 148.85, 129.36, 119.91, 112.33.

[0049] Example 2: Preparation of 1-phenyl-2-[4-(trifluoromethyl)phenyl]-hydrazine

[0050] The reaction equation involved in preparing 1-phenyl-2-[4-(trifluoromethyl)phenyl]-hydrazine (only the target product is reflected in the reaction equation) is as follows:

[0051]

[0052] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0053] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(cyclopentyl)benzene) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 4-trifluoromethylazobenzene, and 0.1 mL of water were added sequentially into a 10 mL quartz test tube equipped with a stirrer, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm illumination for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1). The product 1-phenyl-2-[4-(trifluoromethyl)phenyl]-hydrazine was separated, and the yield of 1-phenyl-2-[4-(trifluoromethyl)phenyl]-hydrazine was 91.5%.

[0054] The results of hydrogen nuclear magnetic resonance and carbon nuclear magnetic resonance characterization of the product obtained in Example 2 are as follows:1 H-NMR (CDCl3, 400MHz) δ (ppm) 7.50-7.47 (d, 2H) 7.29-7.25 (m, 2H), 6.94-6.89 (m, 3H), 6.86-6.83 (q, 2H), 5.85-5.73 (d, 2H); 13 C-NMR (CDCl3, 125MHz) δ (ppm) 151.55, 148.05, 129.49, 126.83, 126.79, 126.76, 126.72, 126.04, 123.34, 121.76, 121.43, 120.50, 112.40, 111.60.

[0055] Example 3: Preparation of 1-phenyl-2-[4-(benzoyl)phenyl]-hydrazine

[0056] The reaction equation involved in preparing 1-phenyl-2-[4-(benzoyl)phenyl]-hydrazine (only the target product is reflected in the reaction equation) is as follows:

[0057]

[0058] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0059] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(pyrocatechol) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 4-benzoylazobenzene, and 0.1 mL of water were added sequentially into a 10 mL quartz test tube equipped with a stirrer, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 5:1), and the product 1-phenyl-2-[4-(benzoyl)phenyl]-hydrazine was separated, and the yield of 1-phenyl-2-[4-(benzoyl)phenyl]-hydrazine was 97.6%.

[0060] The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization results of the product obtained in this Example 3 are as follows: 1 H-NMR(CDCl3,400MHz)δ(ppm)7.79-7.74(m,4H),7.58-7.54(t,1H),7.49-7 .45(t,2H),7.28-7.24(q,2H),6.92-6.84(m,5H),6.09(s,1H),5.79(s,1H); 13C-NMR (CDCl3, 125MHz) δ (ppm) 195.36, 152.87, 147.99, 138.73, 132.84, 131.55, 129.59, 129.47, 128.81, 128.11, 120.51, 112.45, 111.05.

[0061] Example 4: Preparation of 1-phenyl-2-(2-iodophenyl)-hydrazine

[0062] The reaction equation involved in preparing 1-phenyl-2-(2-iodophenyl)-hydrazine (only the target product is reflected in the reaction equation) is as follows:

[0063]

[0064] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0065] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(pyrocatechol) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 2-iodoazobenzene, and 0.1 mL of water were added sequentially into a 10 mL quartz test tube equipped with a stirrer, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1), and the product 1-phenyl-2-(2-iodophenyl)-hydrazine was separated, and the yield of 1-phenyl-2-(2-iodophenyl)-hydrazine was 82.0%.

[0066] The results of hydrogen nuclear magnetic resonance and carbon nuclear magnetic resonance characterization of the product obtained in Example 4 are as follows: 1 H-NMR(CDCl3,400MHz)δ(ppm)7.72-7.70(d,1H),7.27-7.19(m,3H),6.99-6 .97(d,1H),6.90-6.87(t,1H),6.84-6.82(d,2H),6.03(s,1H),5.73(s,1H); 13 C-NMR (CDCl3, 125MHz) δ (ppm) 148.17, 147.26, 138.98, 129.51, 129.43, 121.33, 120.28, 112.89, 112.40, 81.34.

[0067] Example 5: 1-phenyl-2-(4-biphenyl)-hydrazine

[0068] The reaction equation involved in preparing 1-phenyl-2-(4-biphenyl)-hydrazine (only the target product is reflected in the reaction equation) is as follows:

[0069]

[0070] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0071] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(cyclopentyl)benzene) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 4-biphenylazobenzene, and 0.1 mL of water were added to a 10 mL quartz test tube equipped with a stirrer in sequence, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1). The product 1-phenyl-2-(4-biphenyl)-hydrazine was separated, and the yield of 1-phenyl-2-(4-biphenyl)-hydrazine was 96.0%.

[0072] The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization results of the product obtained in this Example 5 are as follows: 1 H-NMR(CDCl3,400MHzδ(ppm)7.65-7.63(d,2H),7.57-7.55(d,2H),7.52-7.48(t, 2H),7.40-7.36(t,1H),7.35-7.31(t,2H),6.99-6.93(m,5H),5.67-5.64(d,2H); 13 C-NMR (CDCl3, 125MHz) δ (ppm) 148.88, 148.38, 141.08, 132.92, 129.48, 128.81, 128.13, 126.57, 126.53, 120.08, 112.76, 112.48.

[0073] Example 6: Preparation of 1-phenyl-2-[4-(sulfonamido)phenyl]-hydrazine

[0074] The reaction equation involved in preparing 1-phenyl-2-[4-(sulfonamido)phenyl]-hydrazine (only the target product is reflected in the reaction equation) is as follows:

[0075]

[0076] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0077] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(pyrocatechol) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 4-sulfonamidoazobenzene, and 0.1 mL of water were added sequentially into a 10 mL quartz test tube equipped with a stirrer, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm illumination for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1). The product 1-phenyl-2-[4-(sulfonamido)phenyl]-hydrazine was separated, and the yield of 1-phenyl-2-[4-(sulfonamido)phenyl]-hydrazine was 81.0%.

[0078] The results of hydrogen nuclear magnetic resonance and carbon nuclear magnetic resonance characterization of the product obtained in Example 6 are as follows: 1 H-NMR (DMSO, 400MHz δ (ppm) 8.30 (s, 1H), 7.83 (s, 1H), 7.58-7.56 (d, 2H), 7.16-7.12 (t, 2H), 6.98 (s, 2H), 6.81-6.79 (d, 2H), 6.72-6.67 (q, 3H); 13 C-NMR (DMSO, 125MHz) δ (ppm) 153.21, 149.61, 132.74, 129.41, 127.86, 118.71, 112.26, 110.81.

[0079] Example 7: Preparation of 1,2-bis(4-bromophenyl)-hydrazine

[0080] The reaction equation involved in preparing 1,2-bis(4-bromophenyl)-hydrazine (only the target product is reflected in the reaction equation) is as follows:

[0081]

[0082] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0083] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(pyrocatechol) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 4,4'-dibromoazobenzene and 0.1 mL of water were added to a 10 mL quartz test tube equipped with a stirrer in sequence, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1), and the product 1,2-bis(4-bromophenyl)-hydrazine was separated and obtained with a yield of 92.4%.

[0084] The results of hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization of the product obtained in Example 7 are as follows: 1 H-NMR (CDCl3, 400MHz δ (ppm) 7.34-7.30 (m, 4H), 6.75-6.71 (m, 4H), 5.64 (s, 2H); 13 C-NMR (CDCl3, 125MHz) δ (ppm) 147.46, 132.20, 113.98, 111.92.

[0085] Example 8: Preparation of 1,2-bis[4-(acetyl)phenyl]-hydrazine

[0086] The reaction equation involved in preparing 1,2-bis[4-(acetyl)phenyl]-hydrazine (only the target product is reflected in the reaction equation) is as follows:

[0087]

[0088] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0089] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(catechol) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 4,4'-diacetyl azobenzene, and 0.1 mL of water were added to a 10 mL quartz test tube equipped with a stirrer in sequence, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1), and the product 1,2-bis[4-(acetyl)phenyl]-hydrazine was separated, and the yield of 1,2-bis[4-(acetyl)phenyl]-hydrazine was 93.9%.

[0090] The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization results of the product obtained in this Example 8 are: 1H-NMR (DMSO, 400MHz δ (ppm) 8.63 (s, 2H), 7.80-7.78 (d, 4H), 6.76.-6.73 (d, 4H), 3.36 (s, 6H); 13 C-NMR (DMSO, 125MHz) δ (ppm) 195.91, 153.86, 130.90, 127.87, 110.89, 26.48.

[0091] Example 9: Preparation of 2,3-diphenyl-2H-indazole

[0092] The reaction equation involved in the preparation of 2,3-diphenyl 2H-indazole (only the target product is reflected in the reaction equation) is as follows:

[0093]

[0094] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0095] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(cyclopentyl)benzene) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 2-benzoylazobenzene, and 0.1 mL of water were added to a 10 mL quartz test tube equipped with a stirrer in sequence, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1), and the product 2,3-diphenyl-2H-indazole was separated, and the yield of 2,3-diphenyl-2H-indazole was 89.5%.

[0096] The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization results of the product obtained in this Example 9 are: 1 H-NMR (CDCl3, 400MHz δ (ppm) 7.84-7.82 (d, 1H), 7.76-7.73 (d, 1H), 7.48-7.38 (m, 11H), 7.19-7.15 (q, 1H); 13 C-NMR(CDCl3,125MHz)δ(ppm)149.02,140.28,135.42,129.96,129.70,128.9 7,128.76,128.31,128.25,126.98,126.04,122.51,121.77,120.51,117.78.

[0097] Example 10: Preparation of 2-phenyl-3-(2-fluorophenyl)-5-chloro-2H-indazole

[0098] The reaction equation involved in preparing 2-phenyl-3-(2-fluorophenyl)-5-chloro-2H-indazole (only the target product is reflected in the reaction equation) is as follows:

[0099]

[0100] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0101] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(cyclopentyl)benzene) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 4-chloro-2-(2-fluorobenzoyl)azobenzene, and 0.1 mL of water were added sequentially into a 10 mL quartz test tube equipped with a stirrer, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm illumination for 30 minutes. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1). The product 2-phenyl-3-(2-fluorophenyl)-5-chloro-2H-indazole was separated, and the yield of 2-phenyl-3-(2-fluorophenyl)-5-chloro-2H-indazole was 97.8%.

[0102] The results of hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization of the product obtained in Example 10 are as follows: 1 H-NMR(CDCl3,400MHzδ(ppm)7.79-7.77(d,1H),7.59(s,1H),7.46-7.30(m,8H),7.24-7.20(m,1H),7.15-7.11(t,1H); 13 C-NMR(CDCl3,125MHz)δ(ppm)160.79,158.30,147.30,140.14,131.79,131.77,131.31,131.23,129.36,129.0 7,128.56,128.40,128.34,125.05,124.66,124.62,123.11,119.52,119.11,117.61,117.46,116.60,116.39.

[0103] Example 11: Preparation of 2-phenyl-3-naphthyl-2H-indazole

[0104] The reaction equation involved in preparing 2-phenyl-3-naphthyl-2H-indazole (only the target product is reflected in the reaction equation) is as follows:

[0105]

[0106] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0107] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(phthalic acid)phenol) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 2-(1-naphthoyl)azobenzene, and 0.1 mL of water were added sequentially into a 10 mL quartz test tube equipped with a stirrer, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 1 hour. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1). The product 2-phenyl-3-naphthyl-2H-indazole was separated, and the yield of 2-phenyl-3-naphthyl-2H-indazole was 99.4%.

[0108] The results of hydrogen nuclear magnetic resonance and carbon nuclear magnetic resonance characterization of the product obtained in Example 11 are as follows: 1 H-NMR (CDCl3, 400MHz δ (ppm) 7.96-7.92 (m, 3H), 7.71-7.69 (d, 2H), 7.54-7.38 (m, 8H), 7.25-7.23 (t, 3H), 7.12-7.08 (q, 1H); 13 C-NMR(CDCl3,125MHz)δ(ppm)148.91,140.28,134.01,133.77,132.08,129.65,129.53,1 28.82,127.08,126.84,126.34,125.65,125.32,125.06,123.45,122.33,120.87,117.87.

[0109] Example 12: Preparation of 2-phenyl-3-(2-chlorophenyl)-2H-indazole

[0110] The reaction equation involved in preparing 2-phenyl-3-(2-chlorophenyl)-2H-indazole (only the target product is reflected in the reaction equation) is as follows:

[0111]

[0112] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0113] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(cyclopentyl)phenol) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 2-(2-chlorobenzoyl)azobenzene, and 0.1 mL of water were added to a 10 mL quartz test tube equipped with a stirrer in sequence, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 1 hour. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1). The product 2-phenyl-3-(2-chlorophenyl)-2H-indazole was separated, and the yield of 2-phenyl-3-(2-chlorophenyl)-2H-indazole was 96.9%.

[0114] The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization results of the product obtained in this Example 12 are: 1 H-NMR (CDCl3, 400MHz δ (ppm) 7.84-7.82 (d, 1H), 7.70-7.68 (d, 1H), 7.45-7.38 (m, 8H), 7.31-7.29 (d, 2H), 7.19-7.16 (q, 1H); 13 C-NMR(CDCl3,125MHz)δ(ppm)148.99,140.00,134.50,134.13,130.86,129.1 5,129.14,128.51,128.40,127.12,126.04,122.89,121.73,120.12,117.91.

[0115] Example 13: Preparation of 2-phenyl-3-cyclohexyl-2H-indazole

[0116] The reaction equation involved in preparing 2-phenyl-3-cyclohexyl-2H-indazole (only the target product is reflected in the reaction equation) is as follows:

[0117]

[0118] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0119] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(cyclohexyl)benzene) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 2-cyclohexylformylazobenzene and 0.1 mL of water were added to a 10 mL quartz test tube equipped with a stirrer in sequence, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 1 hour. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1). The product 2-phenyl-3-cyclohexyl-2H-indazole was separated, and the yield of 2-phenyl-3-cyclohexyl-2H-indazole was 96.6%.

[0120] The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization results of the product obtained in this Example 13 are as follows: 1 H-NMR(CDCl3,400MHzδ(ppm)7.90-7.88(d,1H),7.76-7.73(d,1H),7.54-7.51(m,5H),7.34 -7.30(m,1H),7.09-7.05(m,1H),3.04-2.96(m,1H),2.03-1.85(m,6H),1.45-1.22(m,4H); 13 C-NMR(CDCl3,125MHz)δ(ppm)148.88,141.14,140.23,129.14,128.98,126 .45,126.32,121.24,120.55,119.53,117.84,37.32,32.60,26.59,25.88.

[0121] Example 14: Preparation of 2-phenyl-3-undecyl-2H-indazole

[0122] The reaction equation involved in preparing 2-phenyl-3-undecyl-2H-indazole (only the target product is reflected in the reaction equation) is as follows:

[0123]

[0124] The method for preparing diphenylhydrazine or 2H-indazole compounds by using azobenzene compounds comprises the following steps:

[0125] In a glove box under a nitrogen atmosphere, 0.3 mmol of bis(bis(cyclopentyl)-1-diol) borate (B2cat2), 1.5 mL of an organic solvent of tetrahydrofuran, 0.2 mmol of 2-dodecanoyl azobenzene, and 0.1 mL of water were added to a 10 mL quartz test tube equipped with a stirrer in sequence, and the mixture was mixed to obtain a mixture. The sealed test tube was taken out from the glove box, and the mixture was stirred and reacted under 450 nm light for 40 min. The organic solvent was then removed under reduced pressure, and the mixture was separated and purified by column chromatography. The developing solvent used in the separation and purification process was a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1), and the product 2-phenyl-3-undecyl-2H-indazole was separated, and the yield of 2-phenyl-3-undecyl-2H-indazole was 70.5%.

[0126] The hydrogen nuclear magnetic resonance spectrum and carbon nuclear magnetic resonance spectrum characterization results of the product obtained in this Example 14 are as follows: 1 H-NMR(CDCl3,400MHzδ(ppm)7.76-7.74(d,1H),7.70-7.68(d,1H),7.55-7.48(m,5H),7.35-7.32(t, 1H),7.11-7.07(q,1H),3.07-3.03(t,2H),1.70-1.63(m,2H),1.31-1.22(m,16H),0.92-0.89(t,3H); 13 C-NMR(CDCl3,125MHz)δ(ppm)148.64,140.16,136.93,129.14,128.85,126.63,126.21,121.09,120 .89,120.24,117.62,31.90,29.57,29.55,29.38,29.37,29.31,29.28,29.10,25.29,22.68,14.10.

[0127] Comparative Example 1

[0128] Compared with Example 1, the difference of Comparative Example 1 is that an equal amount of bipyrocatechol borate (B2cat2) is used to replace the bis(bis(pyrocatechol) borate in Example 1, and the yield of 1,2-diphenylhydrazine obtained is 15%.

Claims

1. A method for preparing 2H-indazole compounds using azobenzene compounds, characterized in that: The following steps are involved: Mixing an azobenzene compound, a diboric acid ester, water and an organic solvent, and reacting them to obtain the 2H-indazole compound; The reaction is carried out under visible light; The reaction time is less than 2 hours; The azobenzene compound is selected from any one of the following:

2. The method according to claim 1, characterized in that The reaction is carried out under 400nm-500nm light.

3. The method according to claim 1, characterized in that The reaction time is less than 1 hour.

4. The method according to claim 1, characterized in that: The biboric acid ester is selected from bis(bis(catechol) borate.

5. The method according to claim 1, characterized in that The organic solvent is selected from at least one of tetrahydrofuran, acetonitrile, methanol or dichloromethane.

6. The method according to claim 1, characterized in that The dosage ratio of the azobenzene compound to the organic solvent is 0.1 mmol: 0.5-5 mL.

7. The method according to claim 1, characterized in that The molar ratio of the azobenzene compound, the biboric acid ester and water is 1:(0.5-5):(10-100).

8. The method according to claim 1, characterized in that The 2H-indazole compound is selected from any one of the following:

9. Application of the method according to any one of claims 1 to 8 in the field of organic synthesis.

10. The use according to claim 9, characterized in that: The organic synthesis field includes the field of synthesis of organic dyes, pigments, pesticides, medicines or functional materials.

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