Process for the preparation of diphenylhydrazines or 2h-indazoles from azobenzene compounds

Abstract

The application belongs to the technical field of organic compound preparation, and particularly relates to a method for preparing diphenylhydrazine or 2H-indazole compound by using azobenzene compound. The method comprises the following steps: mixing azobenzene compound, biborate, water and organic solvent, and reacting to prepare 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: the application uses azobenzene compound as raw material, uses water as hydrogen source, adds biborate, and carries out the reaction under visible light irradiation without metal catalyst, and 2H-indazole compound product with a yield of not less than 70% can be prepared in a reaction time of less than 1 hour. Moreover, the method of the application 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 the application with the application number 202211535667.2 and the application title "Method for preparing diphenylhydrazine or 2H-indazole compound by using azobenzene compound", which was filed on December 2, 2022. TECHNICAL FIELD

[0002] The present application belongs to the technical field of organic compound preparation, and particularly relates to a method for preparing diphenylhydrazine or 2H-indazole compound by using azobenzene compound. BACKGROUND

[0003] Diphenylhydrazine and 2H-indazole compounds are important organic chemical raw materials, and are widely used in the synthesis of various fine chemical products such as organic dyes, pigments, pesticides, medicines, and functional materials. At present, the methods for preparing diphenylhydrazine compounds mainly include the following types: (1) reduction of azobenzene or azoxybenzene compound; (2) transition metal reduction of nitro or nitroso benzene; (3) oxidation of arylamine compound; (4) substitution of benzene hydrazine for halogenated aromatic hydrocarbon; (5) oxidation of aryl hydroxylamine compound. The methods for preparing 2H-indazole compounds mainly include the following types: (1) cross-coupling of ortho-halogen-substituted benzaldehyde and phenylhydrazine; (2) 1,3-dipolar cycloaddition of diazo compound; (3) C-H bond amination synthesis of phenylhydrazone.

[0004] There are many methods for preparing diphenylhydrazine compounds at present, and most of the traditional laboratory and industrial preparation methods use aryl nitro compounds as raw materials and reduce them with zinc powder in strong base medium. This kind of traditional method needs to use a large amount of organic transition metal as catalyst, and needs to use alcohol as hydrogen source in the presence of excess strong base at a relatively high temperature, and needs a reaction time of more than 12 hours, so the scope of substrate application is narrow. In the prior art, there are methods for preparing diphenylhydrazine compounds without using metal catalysts, but they often need to be heated to a high temperature, and the reaction time is as long as 24 hours or even longer, in order to obtain diphenylhydrazine compounds. There are many methods for synthesizing 2H-indazole compounds reported in the past, which generally need to use noble metal catalysis or need expensive ligands. Such methods are not only environmentally unfriendly, but also high in cost, and are difficult to be used in industrial production. At present, there are also attempts to synthesize 2H-indazole compounds by using non-metal catalysts, but a large amount of additives are usually used to assist the reaction, which does not meet the requirements of atom economy.

[0005] Therefore, it is urgent to provide a new method for preparing diphenylhydrazine and 2H-indazole compounds, which does not need to use metal catalysts, does not need to be heated, has a short reaction time (less than 24 hours), and has a high product yield. SUMMARY

[0006] The present application aims to at least solve one of the technical problems existing in the prior art. To this end, the present application proposes a method for preparing diphenylhydrazine or 2H-indazole compounds using azobenzene compounds. The method described in the present application not only does not require the use of metal catalysts, but also does not require heating, and only needs visible light irradiation at room temperature, with a short reaction time (less than 24 hours, even less than 2 hours or 1 hour), and a high product yield.

[0007] The inventive concept of the present application is that the present application uses azobenzene compounds as raw materials, water as a hydrogen source, and adds boronate ester, without metal catalysts, under visible light (preferably 400-500 nm) irradiation, and within a reaction time of less than 1 hour, to prepare diphenylhydrazine or 2H-indazole compound products with a yield of not less than 70%. Moreover, the method described in the present application shows wide functional group compatibility, allowing various types of azobenzene compounds to be converted into diphenylhydrazine or 2H-indazole compounds.

[0008] The first aspect of the present application proposes 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 azobenzene compounds, boronate ester, water, and organic solvent, and reacting to prepare the diphenylhydrazine or 2H-indazole compounds;

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

[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 structure Ar 1 -N=N-Ar 2 wherein Ar 1 and Ar 2 independently represent 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] Further preferably, the aryl group is selected from at least one of phenyl and naphthyl.

[0018] Preferably, the substituted aryl group has one or more substituent groups (herein, the plural substituent groups refer to two or more substituent groups, and when the plural substituent groups are present, the plural substituent groups can be the same or different), and the substituent group is selected from at least one of alkyl, alkenyl, alkynyl, aryl, halogen, nitro, alkoxy, ester, sulfonamide, cyano, carbonyl, and trifluoromethyl.

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

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

[0021]

[0022] Preferably, the hydrazine 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 bisboronic acid ester is selected from biscatechol boronic acid ester (bisboronic acid ester is abbreviated as B2cat2.

[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 bisboronic acid ester, and water is 1:(0.5-5):(10-100); further preferably, the molar ratio of the azobenzene compound, the bisboronic acid ester, and water is 1:(1-1.5):(10-50).

[0030] Preferably, the amount 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 simultaneous mixing of all components or stepwise mixing.

[0032] Preferably, the reaction is carried out in a closed condition, inert atmosphere (e.g. nitrogen, argon), mixing the components, irradiation, and reaction.

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

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

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

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

[0037] In particular, the above method is used in the field of organic synthesis.

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

[0039] Compared with the prior art, the present application has the following advantages:

[0040] The present application uses azobenzene compounds as raw materials, water as hydrogen source, and adds bisborate ester, and the reaction is carried out under visible light irradiation without metal catalyst. The diphenylhydrazine or 2H-indazole compound product with a yield of not less than 70% can be obtained within a reaction time of less than 1 hour. Moreover, the method of the present application shows wide 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 those skilled in the art more clearly understand the technical solutions of the present application, the following examples are given for illustration. It should be pointed out that the following examples do not constitute a limitation on the scope of protection required by the present application.

[0042] The raw materials, reagents or devices used in the following examples, if not specifically stated, can be obtained from conventional commercial channels, or can be obtained by 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 shown in the reaction equation) is as follows:

[0045]

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

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

[0048] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this example 1 are: 1 H-NMR (CDCI3, 400 MHz) δ (ppm) 7.26-7.22 (t, 4H), 6.89-6.87 (m, 6H), 5.63 (s, 2H); 13 C-NMR (CDCI3, 125 MHz) 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 (only the target product is embodied in the reaction equation) involved in the preparation of 1-phenyl-2-[4-(trifluoromethyl)phenyl]-hydrazine 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 nitrogen atmosphere, 0.3 mmol of biscatechol borate (B2cat2), 1.5 mL of organic solvent tetrahydrofuran, 0.2 mmol of 4-trifluoromethyl azobenzene, 0.1 mL of water were sequentially added into a 10 mL quartz test tube with a stirrer, mixed to obtain a mixture, the sealed test tube was taken out of the glove box, placed under 450 nm light, stirred for 30 minutes, then the organic solvent was removed under reduced pressure, separated and purified by column chromatography, the developing agent 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 nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this example 2 are:1 H-NMR (CDC13, 400 MHz) 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 (CDC13, 125 MHz) 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 the preparation of 1-phenyl-2-[4-(benzoyl)phenyl]-hydrazine (only the target product is embodied in the reaction equation) is as follows:

[0057]

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

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

[0060] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this example 3 are as follows: 1 H-NMR (CDC13, 400 MHz) 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 (CDC13, 125 MHz) 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 the preparation of 1-phenyl-2-(2-iodophenyl)-hydrazine (only the target product is embodied in the reaction equation) is as follows:

[0063]

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

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

[0066] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this embodiment 4 are as follows: 1 H-NMR (CDC13, 400 MHz) 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 (CDC13, 125 MHz) 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 the preparation of 1-phenyl-2-(4-biphenyl)-hydrazine (only the target product is embodied in the reaction equation) is as follows:

[0069]

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

[0071] In a glove box under nitrogen atmosphere, 0.3 mmol of bis-catechol borate (B2cat2), 1.5 mL of organic solvent tetrahydrofuran, 0.2 mmol of 4-biphenyl azobenzene, and 0.1 mL of water are sequentially added into a 10 mL quartz test tube with a stirrer, mixed to obtain a mixture, the sealed test tube is taken out of the glove box, and placed under 450 nm light for stirring reaction for 30 minutes, then the organic solvent is removed under reduced pressure, and the product 1-phenyl-2-(4-biphenyl)-hydrazine is separated and purified by column chromatography, wherein the developing agent used in the separation and purification process is a mixed solution of n-hexane / ethyl acetate (volume ratio is 15:1), and the yield of 1-phenyl-2-(4-biphenyl)-hydrazine is 96.0%.

[0072] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this embodiment 5 are as follows: 1 H-NMR (CDCI3, 400 MHz δ (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 (CDCI3, 125 MHz) 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] Embodiment 6: Preparation of 1-phenyl-2-[4-(sulfonamido)phenyl]-hydrazine

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

[0075]

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

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

[0078] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in Example 6 are as follows: 1 H-NMR (DMSO, 400 MHz 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, 125 MHz) 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 (only the target product is represented in the reaction equation) involved in the preparation of 1,2-bis(4-bromophenyl)-hydrazine is as follows:

[0081]

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

[0083] In a glove box under nitrogen atmosphere, 0.3 mmol of biscatechol borate (B2cat2), 1.5 mL of organic solvent tetrahydrofuran, 0.2 mmol of 4,4'-dibromoazobenzene, 0.1 mL of water were sequentially added into a 10 mL quartz test tube with a stirrer, mixed to obtain a mixture, the sealed test tube was taken out of the glove box, placed under 450 nm light, stirred for 30 minutes, then the organic solvent was removed under reduced pressure, separated and purified by column chromatography, the developing agent 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, the yield of 1,2-bis(4-bromophenyl)-hydrazine was 92.4%.

[0084] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this example 7 are: 1 H-NMR (CDCI3, 400 MHz δ (ppm) 7.34-7.30 (m, 4H), 6.75-6.71 (m, 4H), 5.64 (s, 2H); 13 C-NMR (CDCI3, 125 MHz) 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 (only the target product is embodied in the reaction equation) involved in the preparation of 1,2-bis[4-(acetyl)phenyl]-hydrazine 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 nitrogen atmosphere, 0.3 mmol of biscatechol borate (B2cat2), 1.5 mL of organic solvent tetrahydrofuran, 0.2 mmol of 4,4'-dibromoazobenzene, 0.1 mL of water were sequentially added into a 10 mL quartz test tube with a stirrer, mixed to obtain a mixture, the sealed test tube was taken out of the glove box, placed under 450 nm light, stirred for 30 minutes, then the organic solvent was removed under reduced pressure, separated and purified by column chromatography, the developing agent 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, the yield of 1,2-bis(4-bromophenyl)-hydrazine was 92.4%.

[0090] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this example 8 are: 1H-NMR (DMSO, 400 MHz 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, 125 MHz) 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 embodied 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 nitrogen atmosphere, 0.3 mmol of bis-catechol borate (B2cat2), 1.5 mL of organic solvent tetrahydrofuran, 0.2 mmol of 2-benzoyl azobenzene, and 0.1 mL of water are sequentially added into a 10 mL quartz test tube with a stirrer, mixed to obtain a mixture, the sealed test tube is taken out of the glove box, and placed under 450 nm light for stirring reaction for 30 minutes, then the organic solvent is removed under reduced pressure, and the product 2,3-diphenyl-2H-indazole is separated and purified by column chromatography, wherein the developing agent used in the separation and purification process is a mixed solution of n-hexane / ethyl acetate (volume ratio is 15:1), and the yield of 2,3-diphenyl-2H-indazole is 89.5%.

[0096] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this example 9 are as follows: 1 H-NMR (DMSO, 400 MHz 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, 125 MHz) δ (ppm) 195.91, 153.86, 130.90, 127.87, 110.89, 26.48.

[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 using azobenzene compounds comprises the following steps:

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

[0102] The results of hydrogen nuclear magnetic resonance (HNMR) and carbon nuclear magnetic resonance (CNMR) 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 compound by using azobenzene compound comprises the following steps:

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

[0108] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in this example 11 are as follows: 1 H-NMR (CDCI3, 400 MHz 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 (CDCI3, 125 MHz) δ (ppm) 148.91, 140.28, 134.01, 133.77, 132.08, 129.65, 129.53, 128.82, 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 (only the target product is represented in the reaction equation) involved in the preparation of 2-phenyl-3-(2-chlorophenyl)-2H-indazole is as follows:

[0111]

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

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

[0114] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in Example 12 are as follows: 1 H-NMR (CDCI3, 400 MHz 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 (CDCI3, 125 MHz) δ (ppm) 148.99, 140.00, 134.50, 134.13, 130.86, 129.15, 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 (only the target product is represented in the reaction equation) involved in the preparation of 2-phenyl-3-cyclohexyl-2H-indazole 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 nitrogen atmosphere, 0.3 mmol of bis-catechol borate (B2cat2), 1.5 mL of organic solvent tetrahydrofuran, 0.2 mmol of 2-cyclohexylcarbonyl azobenzene, 0.1 mL of water were sequentially added into a 10 mL quartz test tube with a stirrer, mixed to obtain a mixture, the sealed test tube was taken out of the glove box, and placed under 450 nm light to stir the reaction for 1 hour, then the organic solvent was removed under reduced pressure, and separated and purified by column chromatography. The developing agent used in the separation and purification process was a mixture of n-hexane / ethyl acetate (volume ratio of 15:1). The isolated product was 2-phenyl-3-cyclohexyl-2H-indazole, and the yield of 2-phenyl-3-cyclohexyl-2H-indazole was 96.6%.

[0120] The nuclear magnetic resonance hydrogen spectrum and nuclear magnetic resonance carbon spectrum characterization results of the product prepared in Example 13 are as follows: 1 H-NMR (CDCI3, 400 MHz δ (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 (CDCI3, 125 MHz) 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 (only the target product is represented in the reaction equation) involved in the preparation of 2-phenyl-3-undecyl-2H-indazole 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 nitrogen atmosphere, 0.3 mmol of biscatechol borate (B2cat2), 1.5 mL of organic solvent tetrahydrofuran, 0.2 mmol of 2-dodecanoyl azobenzene, 0.1 mL of water were sequentially added into a 10 mL quartz test tube with a stirrer, mixed to obtain a mixture, the sealed test tube was taken out of the glove box, placed under 450 nm light, and stirred for 40 min, then the organic solvent was removed under reduced pressure, and the product 2-phenyl-3-undecyl-2H-indazole was separated and purified by column chromatography. The separation and purification process used a mixed solution of n-hexane / ethyl acetate (volume ratio of 15:1) as the developing agent, and the yield of 2-phenyl-3-undecyl-2H-indazole was 70.5%.

[0126] The results of the nuclear magnetic resonance hydrogen spectrum and the nuclear magnetic resonance carbon spectrum of the product prepared in Example 14 are as follows: 1 H-NMR (CDCI3, 400 MHz δ (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 (CDCI3, 125 MHz) 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] Comparative Example 1 is different from Example 1 only in that an equal amount of bisboronic acid pinacol is used instead of biscatechol borate (B2cat2) in Example 1, and the yield of 1,2-diphenylhydrazine is 15%.

Claims

1. A process for the preparation of 2H-indazoles using azobenzene compounds, characterized in that, The method comprises the following steps: mixing an azobenzene compound, a bisboronic acid ester, water and an organic solvent, and reacting 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: The 2H-indazole compound is selected from any one of the following:

2. The method of claim 1, wherein, The reaction is carried out under light with a wavelength of 400-500 nm.

3. The method of claim 1, wherein, The reaction time is less than 1 hour.

4. The method of claim 1, wherein, The bisboronic acid ester is selected from bis-o-benzosemicarbazide boronic acid ester.

5. The method of claim 1, wherein, The organic solvent is selected from at least one of tetrahydrofuran, acetonitrile, methanol or dichloromethane.

6. The method of claim 1, wherein, The ratio of the azobenzene compound to the organic solvent is 0.1 mmol: 0.5-5 mL.

7. The method of claim 1, wherein, The molar ratio of the azobenzene compound, the bisboronic acid ester and water is 1:(0.5-5):(10-100).

8. Use of the method according to any one of claims 1-7 in the field of synthesis of organic dyes, pigments, pesticides, medicines or functional materials.

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