Synthesis method of fluorine-containing indazole derivative

Abstract

The invention provides a synthesis method of a fluorine-containing indazole derivative. 2, 3-difluorobenzoic acid is used as a raw material and is subjected to bromination, amidation and Grignard reaction to obtain aromatic substituted ketone, the aromatic substituted ketone and hydrazine hydrate are subjected to cyclization to obtain a compound with an indazole skeleton, t-butyloxycarboryl is further introduced to protect amido on an indazole ring, and then Suzuki coupling and oxidation reaction are performed to obtain the fluorine-containing indazole derivative which is not reported in literature. The problems of poor selectivity, more byproducts, difficulty in separation and the like caused by fluorination reaction are avoided.

Description

Technical Field

[0001] The invention relates to the technical field of pharmaceutical and chemical intermediate synthesis, in particular to a method for synthesizing fluorine-containing indazole derivatives. Background Art

[0002] As a unique member of nitrogen-containing heterocyclic compounds, indazole has received extensive attention and research due to its good biological properties and pharmacological activities. Drugs with indazole structure as the skeleton, such as Pazopanib, Axitinib, Entrectinib, Niraparib, etc., have broad application prospects in clinical treatment fields such as anti-tumor, anti-cancer, anti-inflammatory and antibacterial. The introduction and modification of heteroatom groups such as fluorine-containing groups can improve the distribution of electron cloud density inside the molecule, thereby promoting the production of special physical, chemical properties and physiological activities of organic compounds. Therefore, the further synthesis of drugs with high biological activity using fluorine-containing indazole derivatives as intermediates has great research prospects and value.

[0003] At present, there are two main methods for the synthesis of indazole derivatives, namely, extraction by biological methods and synthesis by chemical methods. In nature, indazole mainly exists in the form of alkaloids in black algae (Tetrahedron Lett., 1995, 36, 1993–1996.), so the extraction of indazole derivatives from black algae is a common biological extraction method. Tao Yuan et al. (J. Nat. Prod., 2014, 77, 2316−2320) used n-hexane and methanol to extract the ground powder of air-dried black algae seeds, and the extracts were separated by gel chromatography, and then purified by semi-preparative high performance liquid chromatography to obtain a variety of indazole derivatives. The specific extraction process is shown below. However, the technical barriers of biological methods in terms of raw material sources, extraction and separation, characterization optimization, and huge costs also limit their application in actual production.

[0004] Compared with biological methods, chemical synthesis is an effective method to obtain compounds with more precise structures. Among them, the most common method is to generate indazole rings by reacting aromatic aldehydes and ketones with hydrazine compounds (reaction equation a). Hari et al. (Tetrahedron Lett., 2005, 46, 3771–3774.) reported an aromatic substituted 1H-indazole obtained from 2-bromobenzaldehyde and phenylhydrazine. Another method is to use the intramolecular cyclization of N', N'-disubstituted 2-halogenated benzohydrazines to obtain similar derivatives (reaction equation b). Arán et al. (J. Heterocycl. Chem., 1985, 22, 1743–1745.) used this method to synthesize multi-substituted 1H-indazoles. In addition, the indazole skeleton is constructed by CH amination reaction (Org. Lett., 2015, 17, 3386–2289.), and the method of obtaining indazole derivatives by using pyrazole derivatives and olefins (Angewandte Chemie-International Edition in English, 2017, 56, 16262–16266.) or alkynes (Org. Lett., 2017, 19, 1450–1453.) under the action of palladium catalyst is also commonly reported (reaction equation ce). This application involves the introduction of heteroatoms (fluorine atoms). Most of the existing technologies first synthesize the indazole skeleton and then introduce fluorine atoms by fluorination reaction. Therefore, most of the existing methods have problems such as poor selectivity and many by-products. The separation and purification problems brought about by this also limit its large-scale application in industrial production to a certain extent.

[0005] The existing technologies, whether biological or chemical, mostly have problems such as low yield, poor selectivity, many by-products, and difficulty in separation and purification, making them difficult to apply to large-scale industrial production. In addition, this application proposal involves the introduction of fluorine atoms. The introduction of fluorine-containing groups into the molecular structure of natural products can give them unique biological activity and pharmacological properties, but there are few methods for incorporating fluorine elements into complex biologically active molecules, so selective fluorination is still extremely challenging. Summary of the invention

[0006] In view of the above situation, seeking an efficient method for synthesizing indazole pharmaceutical intermediates can provide new ideas for synthesizing similar compounds and provide references for industrial production. The purpose of this application proposal is to provide a method for synthesizing fluorinated indazole derivatives. The raw material is 2,3-difluorobenzoic acid, which is subjected to bromination, amidation, and Grignard reaction to obtain aromatic substituted ketones, which are then cyclized with hydrazine hydrate to obtain compounds with indazole skeletons. The amine group on the indazole ring is further protected by introducing tert-butyloxycarbonyl, and then Suzuki coupling and oxidation reactions are performed to obtain a fluorinated indazole derivative that has not been reported in the literature, which avoids the problems of poor selectivity, many by-products, and difficulty in separation caused by fluorination reactions, and provides valuable references for the above problems.

[0007] To achieve the above object, the present invention adopts the following technical solution: A method for synthesizing a fluorine-containing indazole derivative comprises the following steps: (1) The raw material 2,3-difluorobenzoic acid and the bromination reagent are reacted in a concentrated acid condition. After the reaction is completed, the reaction solution is cooled to room temperature, poured into ice water while stirring, and filtered after standing overnight. The wet product is dried by air to obtain 5-bromo-2,3-difluorobenzoic acid, which is recorded as compound I; (2) Compound I was dissolved in an organic solvent, and a catalyst, triethylamine and an amidation reagent were added. The mixture was stirred in an ice-water bath for 10 minutes and then moved to room temperature for reaction. After the reaction was completed, water was added and the mixture was extracted with ethyl acetate. The organic phase was washed with saturated brine, dried with a desiccant, and then the solvent was removed by reduced pressure distillation. The wet product was dried in vacuo to obtain 5-bromo-2,3-difluoro-N'-methoxy-N'-methylbenzamide, which was recorded as Compound II. (3) Compound II was dissolved in an organic solvent, and a Grignard reagent was added under nitrogen protection and an ice-water bath. After the addition was completed, the reaction was carried out at room temperature. After the reaction was completed, the pH was adjusted to 3-4, and the stirring was continued for 30 minutes. Then, the mixture was allowed to stand for stratification, and the solvent was removed from the upper layer by vacuum distillation. The crude product was redissolved in ethyl acetate, washed with saturated brine, dried with a desiccant, and then the ethyl acetate was removed by vacuum distillation. The wet product was vacuum dried to obtain 1-(5'-bromo-2',3'-difluorophenyl)ethane-1-one, which was recorded as compound III. (4) Compound III was added to an organic solvent and stirred to dissolve, hydrazine hydrate was added and the temperature was raised to 150°C for reflux reaction. After the reaction was completed, the reaction solution was cooled to room temperature, and then slowly poured into ice water with continuous stirring. After standing overnight, it was filtered, and the wet product was dried by air blowing to obtain 5-bromo-7-fluoro-3-methyl-1H-indazole, which was recorded as compound IV; (5) Compound IV is dissolved in an organic solvent, di-tert-butyl dicarbonate and triethylamine are added in sequence, and a catalyst is slowly added after stirring to dissolve, and the reaction is carried out at room temperature. After the reaction is completed, the solvent is removed by distillation under reduced pressure, and the crude product is redissolved in ethyl acetate until clear, washed with saturated brine, dried with a desiccant, and then the ethyl acetate is removed by distillation under reduced pressure. The wet product is dried in vacuo to obtain 1-(tert-butyloxycarbonyl)-5-bromo-7-fluoro-3-methyl-1H-indazole, which is recorded as compound V; (6) Compound V was added to an organic solvent and stirred to dissolve, and then vinylboronic acid pinacol ester, potassium carbonate, palladium catalyst, and water were added in sequence. The temperature was raised to 90°C under nitrogen protection for reaction. After the reaction was completed, the upper liquid was poured into water while hot and continued to be stirred, and then cooled to room temperature. Then, ethyl acetate was used for extraction, and the mixture was washed with saturated brine. After drying with a desiccant, the ethyl acetate was removed by vacuum distillation. The crude product was ultrasonically dissolved with petroleum ether, filtered, and then the petroleum ether was removed by vacuum distillation. The wet product was dried in vacuo to obtain 1-(tert-butyloxycarbonyl)-5-enyl-7-fluoro-3-methyl-1H-indazole, which was recorded as compound VI. (7) Compound VI is added to an organic solvent and stirred to dissolve, and then sodium bicarbonate and potassium permanganate are added in sequence. After the addition is completed, the mixture is moved to room temperature for reaction. After the reaction is completed, the mixture is filtered and dissolved with ethyl acetate. The pH is adjusted to 4-5 with dilute acid, and impurities are removed by filtration. The mixture is then washed with saturated brine and dried with a desiccant. The ethyl acetate is removed by vacuum distillation. The wet product is dissolved with an organic solvent and pulped twice, and then filtered. The wet product is dried under vacuum to obtain 1-(tert-butyloxycarbonyl)-7-fluoro-3-methyl-1H-indazole-5-carboxylic acid, which is recorded as compound VII.

[0008] Furthermore, the bromination reagent in step (1) can be an organic bromination reagent, such as N-bromosuccinimide (NBS), DBH, PyHBr3, carbon tetrabromide, etc. The reagent is NBS, and its amount is 1 to 2 times that of the raw material; the acid is concentrated sulfuric acid, and its amount is 3 to 5 times that of the raw material; the reaction temperature is 60°C; the reaction time is 4 to 8 h; and the drying temperature is 50°C.

[0009] Furthermore, in the step (2), the solvent may be selected from halogenated hydrocarbons, aromatic hydrocarbons, acetonitrile, esters, ketones, dioxane, etc., and may be a single solvent or a mixed solvent. The mixing ratio is not particularly limited. The organic solvent is N-methyl-2-pyrrolidone (NMP), and its amount is 8 to 12 times that of compound I. The catalyst may be selected from carbonium salt condensation agents, phosphonium salt condensation agents, organic phosphorus condensation agents, etc. The catalyst is 2-(7-azobenzotriazole)-N,N,N',N'-tetramethyluronium hexafluorophosphate (HATU), and its amount is 1 times that of compound I. The amidating agent is N-methyl-N-methoxyamine hydrochloride, and its amount is 1 times that of compound I. The reaction time is 2 to 4 h; the desiccant can be a neutral desiccant, such as anhydrous calcium chloride, anhydrous magnesium chloride, anhydrous sodium sulfate, etc. The desiccant is anhydrous sodium sulfate, and its dosage is 5 to 10 times the volume of the reaction solution (per 100 ml); the drying temperature is 40°C.

[0010] Furthermore, in step (3), the organic solvent is tetrahydrofuran (THF), and the amount used is 5 times that of compound II; the Grignard reagent is 2.5 mol / L methylmagnesium bromide, and the amount used is 2-4 times that of compound II; the solution for adjusting pH is saturated ammonium chloride solution; the desiccant is anhydrous sodium sulfate, and the amount used is 5-10 times the volume of the reaction solution (per 100 ml); and the drying temperature is 40°C.

[0011] Furthermore, in the step (4), the organic solvent is N-methyl-2-pyrrolidone, and its amount is 5 times that of compound III; the amount of hydrazine hydrate is 2 times that of compound III; the reaction temperature is 150°C; the reflux reaction time is 3 to 5 h; the amount of ice water is 3 to 5 times the volume of the reaction solution; and the drying temperature is 50°C.

[0012] Furthermore, in the step (5), the organic solvent is dichloromethane, and its amount is 5 times that of compound IV; the amount of tert-butyloxycarboxylic anhydride is 1-1.5 times that of compound IV; the amount of triethylamine is 1-1.5 times that of compound IV; the catalyst is 4-dimethylaminopyridine (DMAP), and its amount is 0.02-0.5 mol; the reaction time is 3-5 h; the desiccant is anhydrous sodium sulfate, and its amount is 5-10 times the volume of the reaction solution (per 100 ml); and the drying temperature is 40°C.

[0013] Furthermore, in the step (6), the organic solvent is 1,4-dioxane, and its amount is 5 times that of compound V; the amount of vinylboronic acid pinacol ester is 1.5 times that of compound V; the amount of potassium carbonate is 2.5 times that of compound V; the catalyst can be a palladium catalyst, and the catalyst is 1,1'-bis(diphenylphosphino)ferrocenepalladium dichloride (PdCl2(dppf)), and its amount is 0.005~0.04 mol; the amount of water is 0.25 times that of the solvent dioxane; the temperature is 90°C; the reaction time is 3~5 h; the desiccant is anhydrous sodium sulfate, and its amount is 5~10 times the volume of the reaction solution (per 100 ml); the amount of petroleum ether is 4~6 times that of the solvent; and the drying temperature is 40°C.

[0014] Furthermore, in the step (7), the organic solvent is acetone, and its amount is 0.75 times that of compound VI (per 100 grams); the amount of sodium bicarbonate is 0.8-1 times that of compound VI; the amount of potassium permanganate is 4-5 times that of compound VI; the reaction time is 10-12 h; the dilute acid is dilute hydrochloric acid; the desiccant is anhydrous sodium sulfate, and its amount is 5-10 times the volume of the reaction solution (per 100 milliliters); the organic solvent for pulping is a mixed solution of petroleum ether and ethyl acetate, and the mixing ratio is 10:1; and the drying temperature is 40°C.

[0015] The advantages of the present invention are: The raw materials are easily available and low in price, and the relevant processes have been optimized to improve production efficiency. The synthetic method adopted avoids the fluorination reaction with poor selectivity, and the synthetic route is reasonable, the operation is simple, easy to control, the selectivity is high, the product quality is stable, and the yield is high. The waste liquid and waste gas of each step of the reaction can be reasonably recycled, which reduces the cost while being environmentally friendly, and has great application value and social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is the H NMR spectrum of 5-bromo-2,3-difluorobenzoic acid.

[0017] Figure 2 This is the H NMR spectrum of 5-bromo-2,3-difluoro-N'-methoxy-N'-methylbenzamide.

[0018] Figure 3 This is the H NMR spectrum of 1-(5'-bromo-2',3'-difluorophenyl)ethan-1-one.

[0019] Figure 4 This is the H NMR spectrum of 5-bromo-7-fluoro-3-methyl-1H-indazole.

[0020] Figure 5This is the H NMR spectrum of 1-(tert-butyloxycarbonyl)-5-bromo-7-fluoro-3-methyl-1H-indazole.

[0021] Figure 6 This is the H NMR spectrum of 1-(tert-butoxycarbonyl)-5-enyl-7-fluoro-3-methyl-1H-indazole.

[0022] Figure 7 This is the H NMR spectrum of 1-(tert-butoxycarbonyl)-7-fluoro-3-methyl-1H-indazole-5-carboxylic acid. DETAILED DESCRIPTION

[0023] In order to make the above features and advantages of the present invention more clearly understood, the following embodiments are given for detailed description. The methods of the present invention are all conventional methods in the art unless otherwise specified.

[0024] This application proposal provides a method for synthesizing fluorinated indazole derivatives, using the following synthetic route: The synthesis process comprises the following steps: (1) 2,3-difluorobenzoic acid and NBS were dissolved in concentrated sulfuric acid and reacted at 60°C to prepare compound I. After the reaction was completed, the reaction solution was cooled to room temperature, poured into ice water while stirring, and filtered after standing overnight. After air drying at 50°C, 5-bromo-2,3-difluorobenzoic acid (I) was obtained. Its structure was confirmed by hydrogen nuclear magnetic resonance spectroscopy, and characterization information ( Figure 1 )as follows: 1 H NMR (300MHz, DMSO-d6) δ 13.80(br, 1H), 8.01 (m, 1H), 7.74 (m,1H).

[0025] (2) Dissolve the compound I prepared in step (1) in NMP, add HATU, triethylamine and N-methyl-N-methoxyamine hydrochloride, stir in an ice-water bath for 10 minutes and then move to room temperature for reaction. After the reaction is completed, add water and extract with ethyl acetate. The organic phase is washed with saturated brine, dried over anhydrous sodium sulfate and then distilled under reduced pressure to remove the solvent. After vacuum drying at 40°C, 5-bromo-2,3-difluoro-N'-methoxy-N'-methylbenzamide (II) is obtained. The structure is confirmed by hydrogen nuclear magnetic resonance spectroscopy, and the characterization information ( Figure 2 )as follows: 1 H NMR (300 MHz, DMSO-d6) δ 7.94 (m, 1H), 7.60 (dt, J = 3.4,1.6 Hz, 1H), 3.52 (s,3H), 3.28 (s, 3H).

[0026] (3) Dissolve the compound II prepared in step (2) in THF, add methylmagnesium bromide under nitrogen protection and ice-water bath conditions, and move to room temperature for reaction after the addition is complete. After the reaction is completed, adjust the pH to 3-4, continue stirring for 30 minutes, and then let stand to separate the layers. Remove the solvent from the upper layer by vacuum distillation. The crude product is redissolved in ethyl acetate, washed with saturated brine, dried over anhydrous sodium sulfate, and then removed by vacuum distillation. After vacuum drying at 40°C, 1-(5'-bromo-2',3'-difluorophenyl)ethane-1-one (III) is obtained. The structure is confirmed by hydrogen nuclear magnetic resonance spectroscopy, and the characterization information ( Figure 3 )as follows: 1 H NMR (300 MHz, DMSO-d6) δ 7.68 (m, 1H), 7.58 (m, 1H), 2.51 (s, 3H).

[0027] (4) The precursor ketone compound III prepared in step (3) was added to NMP and stirred to dissolve, and then 80% hydrazine hydrate was added and the temperature was raised to 150°C for reflux reaction. After the reaction was completed, the reaction solution was cooled to room temperature, and then slowly poured into ice water with continuous stirring. After standing overnight, it was filtered and dried at 50°C to obtain 5-bromo-7-fluoro-3-methyl-1H-indazole (IV). Its structure was confirmed by hydrogen nuclear magnetic resonance spectroscopy, and the characterization information ( Figure 4 )as follows: 1 H NMR (300 MHz, DMSO-d6) δ 13.42 (s, 1H), 7.84 (s,1H), 7.44 (d, J = 7.8 Hz, 1H), 2.50 (s, 3H).

[0028] (5) Dissolve the compound IV prepared in step (4) in dichloromethane, add di-tert-butyl dicarbonate and triethylamine in turn, stir to dissolve, then slowly add DMAP, and react at room temperature. After the reaction is completed, remove the solvent by distillation under reduced pressure, redissolve the crude product in ethyl acetate until clear, wash with saturated brine, dry over anhydrous sodium sulfate, and then remove ethyl acetate by distillation under reduced pressure. After vacuum drying at 40°C, 1-(tert-butyloxycarbonyl)-5-bromo-7-fluoro-3-methyl-1H-indazole (V) is obtained. The structure is confirmed by hydrogen nuclear magnetic resonance spectroscopy, and the characterization information ( Figure 5 )as follows: 1 H NMR (300 MHz, DMSO-d6) δ 7.52 (d, J =1.2 Hz, 1H), 7.32 (dd, J = 8.2, 1.2 Hz, 1H), 2.50 (s, 3H), 1.63 (s, 9H).

[0029] (6) Add compound V obtained in step (5) to 1,4-dioxane and stir to dissolve, then add vinylboronic acid pinacol ester, potassium carbonate, PdCl2 (dppf), and water in turn. Under nitrogen protection, heat to 90°C for reaction. After the reaction is completed, pour the upper liquid into water while hot and continue stirring, then cool to room temperature, then extract with ethyl acetate, wash with saturated brine, dry with anhydrous sodium sulfate, remove ethyl acetate by vacuum distillation, ultrasonically dissolve the crude product with petroleum ether, filter and remove petroleum ether by vacuum distillation, and dry at 40°C to obtain 1-(tert-butyloxycarbonyl)-5-enyl-7-fluoro-3-methyl-1H-indazole (VI). Its structure was confirmed by hydrogen nuclear magnetic resonance spectroscopy, and characterization information ( Figure 6 )as follows: 1 H NMR (300 MHz, DMSO-d6) δ 7.29 (dd, J = 5.4, 1.1 Hz, 1H), 7.19 (s, 1H), 6.70 (dd, J =13.2,8.2 Hz, 1H), 5.68 (d, J = 13.1 Hz, 1H), 5.25 (d, J = 8.2 Hz, 1H), 2.50 (s, 3H), 1.61 (s, 9H).

[0030] (7) Add compound VI prepared in step (6) to acetone and stir to dissolve, then add sodium bicarbonate and potassium permanganate in sequence, and move to room temperature for reaction. After the reaction is completed, filter, dissolve with ethyl acetate, adjust the pH to 4-5 with dilute acid, filter to remove impurities, then wash with saturated brine and dry with anhydrous sodium sulfate, finally remove ethyl acetate by vacuum distillation, dissolve the wet product with a mixed solution of petroleum ether: ethyl acetate = 10:1 by volume, and slurry twice, finally filter, and vacuum dry at 40°C to obtain 1-(tert-butyloxycarbonyl)-7-fluoro-3-methyl-1H-indazole-5-carboxylic acid (VII). Its structure was confirmed by hydrogen nuclear magnetic resonance spectroscopy, and characterization information ( Figure 7 )as follows: 1 H NMR (300 MHz, DMSO-d6) δ 13.21 (br, 1H), 8.14 (d, J = 1.0Hz, 1H), 7.75 (dd, J =9.3, 1.0 Hz, 1H), 2.49 (s, 3H), 1.55 (s, 9H).

[0031] The present application proposal is further described below in conjunction with specific embodiments, and the advantages and features of the present application proposal will become clearer as the description proceeds. However, the embodiments are merely exemplary and do not constitute any limitation to the scope of the present application proposal.

[0032] Example 1: Synthesis of 5-bromo-2,3-difluorobenzoic acid (I) At room temperature, 2,3-difluorobenzoic acid (100 g, 0.633 mol) was placed in a 1L three-necked flask, 300 mL of concentrated sulfuric acid was added, and then NBS (136.33 g, 0.766 mol) was added and stirred until dissolved, and the temperature was controlled at 60°C for 3 h. After the reaction was completed, the reaction solution was cooled to room temperature, and then the reaction solution was poured into ice water batch by batch and stirred continuously. After overnight, it was filtered and the filter cake was rinsed with appropriate amount of water to obtain a white solid. The wet product was dried at 50°C for 24 h to obtain 120 g of 5-bromo-2,3-difluorobenzoic acid with a molar yield of 80.0%.

[0033] Example 2: Synthesis of 5-bromo-2,3-difluoro-N'-methoxy-N'-methylbenzamide (II) Compound I (120 g, 0.507 mol) was placed in a 5 L three-necked flask, 1.2 L N-methyl-2-pyrrolidone was added and stirred to dissolve, and HATU (212.4 g, 0.559 mol), triethylamine (178.8 g, 1.770 mol), and N-methyl-N-methoxyamine hydrochloride (58.1 g, 0.596 mol) were added in sequence. The entire feeding process was carried out in an ice-water bath. After the addition was completed, the mixture was stirred for another 10 minutes, and then moved to room temperature for reaction for 3 h. After the reaction was completed, the same volume of water was added to the reaction solution, and then extracted three times with ethyl acetate. The combined ethyl acetate organic phase was washed three times with saturated brine, dried with anhydrous sodium sulfate for about 30 minutes, and then the ethyl acetate was removed by vacuum rotary evaporation. The wet product was vacuum dried at 40 ° C for 12 h to obtain 95.6 g of gray-green solid with a molar yield of 67.4%.

[0034] Example 3: Synthesis of 1-(5'-bromo-2',3'-difluorophenyl)ethane-1-one (III) Compound II (95.6 g, 0.342 mol) was placed in a 2 L three-necked flask, 500 mL of ultra-dry THF was added and stirred to dissolve, 300 mL of 2.5 mol / L methylmagnesium bromide THF solution was slowly added under N2 protection and ice-water bath, and the mixture was moved to room temperature for reaction for 3 h. After the reaction was completed, saturated ammonium chloride solution was slowly added under ice-water bath to adjust the pH to 3-4, and then the mixture was stirred at room temperature for 30 minutes, and the mixture was allowed to stand for stratification. The upper liquid was evaporated under reduced pressure to remove THF, and the obtained black viscous substance was dissolved in ethyl acetate, washed with saturated brine three times, dried with anhydrous sodium sulfate for 30 minutes, and then the ethyl acetate was removed by reduced pressure rotary evaporation. The wet product was vacuum dried at 40 ° C for 12 h to obtain 66.9 g of gray-green solid with a molar yield of 83.3%.

[0035] Example 4: Synthesis of 5-bromo-7-fluoro-3-methyl-1H-indazole (IV) Compound III (66.9 g, 0.285 mol) was placed in a 1 L three-necked flask, 330 mL of N-methyl-2-pyrrolidone was added, and the mixture was stirred and dissolved. Then, a hydrazine hydrate solution (36.1 g, 0.578 mol) with a mass fraction of 80% in NMP was added. After the addition was completed, the mixture was heated to 150°C and refluxed for 3 h. After the reaction was completed, the reaction solution was cooled to room temperature, slowly poured into 5 times the volume of ice water and stirred continuously, and allowed to stand overnight. The filter cake was then filtered and rinsed with an appropriate amount of water. The wet product was dried at 50°C with air blast for 24 h to obtain 46.7 g of a yellow solid with a molar yield of 71.6%.

[0036] Example 5: Synthesis of 1-(tert-butyloxycarbonyl)-5-bromo-7-fluoro-3-methyl-1H-indazole (V) At room temperature, compound IV (46.7 g, 0.204 mol) was placed in a 1 L three-necked flask, 230 mL of dichloromethane was added and stirred to dissolve, and then di-tert-butyl dicarbonate (67.2 g, 0.308 mol) and triethylamine (31.3 g, 0.310 mol) were added in sequence. After the solution was clarified, an appropriate amount of DMAP was slowly added and reacted at room temperature for 3 h. After the reaction was completed, dichloromethane was removed by vacuum rotary evaporation, and the obtained black viscous material was dissolved in ethyl acetate until clarified, washed with saturated brine 3 times, and dried with anhydrous sodium sulfate for about 30 minutes. Finally, ethyl acetate was removed by vacuum rotary evaporation, and the wet product was vacuum dried at 40 ° C for 12 h to obtain 46.4 g of gray solid, with a molar yield of 69.2%.

[0037] Example 6: Synthesis of 1-(tert-butyloxycarbonyl)-5-enyl-7-fluoro-3-methyl-1H-indazole (VI) Compound V (46.4 g, 0.141 mol) was placed in a 1 L three-necked flask, 230 mL of 1,4-dioxane was added and stirred to dissolve, and then vinylboronic acid pinacol ester (32.5 g, 0.211 mol), potassium carbonate (48.7 g, 0.353 mol), PdCl2 (dppf) (4.1 g, 5.64×10 -3mol), water 57.5 mL. Under N2 protection, heat to 90 ° C for 3 h. After the reaction is completed, pour the upper liquid into three times the volume of water while stirring, and then cool to room temperature. Then use ethyl acetate to extract three times, wash with saturated brine three times, and then dry with anhydrous sodium sulfate for about 30 minutes, and then remove ethyl acetate by vacuum rotary evaporation to obtain a black solid. The black solid is ultrasonically dissolved with a large amount of petroleum ether, filtered and vacuum rotary evaporation to remove petroleum ether to obtain the desired product. The wet product is vacuum dried at 40 ° C for 2 h to obtain 29.5 g of a yellow solid with a molar yield of 75.8%.

[0038] Example 7: Synthesis of 1-(tert-butyloxycarbonyl)-7-fluoro-3-methyl-1H-indazole-5-carboxylic acid (VII) Under ice water bath, compound VI (29.5 g, 0.107 mol) was placed in a 5 L three-necked flask, 2.2 L acetone was added and stirred to dissolve, and then sodium bicarbonate (7.4 g, 0.088 mol) and potassium permanganate (73.8 g, 0.467 mol) were added in sequence. After the addition, the mixture was moved to room temperature for reaction for 12 h. After the reaction was completed, the mixture was filtered, and the obtained black solid was dissolved in ethyl acetate and the pH was adjusted to 4-5 with dilute hydrochloric acid. The impurities were removed by filtration, and then washed with saturated brine for 3 times and dried with anhydrous sodium sulfate for about 30 minutes. The ethyl acetate was removed by vacuum evaporation, and the wet product was slurried twice with a mixed solution of petroleum ether: ethyl acetate = 10:1 by volume, and finally filtered. The wet product was vacuum dried at 40 ° C for 2 h to obtain 27.8 g of light yellow solid with a molar yield of 88.3%.

[0039] Biological evaluation Test example: Inhibitory effect of compound VII on sGC activity Guanylate cyclase (sGC) is closely related to the occurrence and development of tumors. Guanylate cyclase is mainly involved in various biological processes in cells, such as purine metabolism and nucleic acid synthesis. However, overexpression of sGC can induce DNA mutations and make the genome unstable. Therefore, high expression of guanylate cyclase usually induces tumor cell proliferation and growth, leading to the occurrence and deterioration of tumors. Currently, many anticancer drugs on the market achieve anti-cancer effects by inhibiting the catalytic activity of sGC, or use sGC as a target to detect the expression level of guanylate cyclase in tumor cells for drug screening and new drug development. The following experimental method is used to determine the inhibitory effect of the target product on human soluble guanylate cyclase (sGC) under in vitro conditions. This method uses the human guanylate cyclase (sGC) kit (ELISA) and measures the absorbance (OD value) by an enzyme reader. The concentration of sGC is positively correlated with the OD value. The IC value of the inhibitory activity of the compound is calculated based on the concentration and luminescence signal value of the compound. 50 value.

[0040] The specific experimental method refers to the instruction manual of the kit. The experimental process is as follows: prepare the sample to be tested synthesized in this application proposal into a DMSO solution with a final concentration of 10 mM. Set up standard wells and sample wells on the ELISA plate, and add 50 μL of standard of different concentrations to each standard well. The sample wells are set as blank wells (blank control wells do not add samples and enzyme-labeled reagents, and the rest of the steps are the same as the sample wells to be tested) and sample wells to be tested. Add 40 μl of sample diluent and 10 μl of sample solution to the sample wells to be tested, dilute the sample solution to 5 times, and shake gently without touching the well wall as much as possible. Add 100 μl of enzyme-labeled reagent to each well except the blank well, seal the plate with a sealing film, and incubate at 37°C for 60 minutes. Remove the sealing film, discard the liquid, spin dry, fill each well with concentrated washing solution (pre-diluted 20 times with distilled water), let it stand for 30 seconds and then discard it. Repeat the above washing steps 5 times and pat dry. Add 50 μl of colorimetric reagent A and colorimetric reagent B to each well, shake and mix, and color develop at 37°C in the dark for 15 minutes, then add 50 μl of stop solution to terminate the reaction. Measure the absorbance 15 minutes after adding the stop solution, adjust the blank well to zero, and measure the absorbance (OD value) of each well in sequence at a wavelength of 450nm using an enzyme reader. Compare the absorbance ratio with the control group to calculate the inhibition rate of the compound at each concentration, and then use GraphPadPrism5 to perform nonlinear curve fitting using logarithmic concentration-inhibition rate to calculate the IC value of the compound. 50 The performance of the sGC inhibitor NS-2028 was compared with that of the common sGC inhibitor NS-2028. The data are shown in the following table.

[0041] It can be seen from the data in the table that the compound VII synthesized in the present application proposal has a certain inhibitory effect on the sGC enzyme, and its inhibitory activity is better than that of the control compound NS-2028. Therefore, the compound of the present invention is expected to be used for the treatment of sGC inhibitors and related diseases.

[0042] It should be noted that the above specific scheme is not limited to the above examples. The technical features not described in the present invention can be achieved by or by adopting the existing technology, which will not be repeated here. The above embodiments are only used to illustrate the technical scheme of the present application, and are not limitations of the present application. The present invention is described in detail with reference to the preferred implementation methods. Ordinary technicians in this field should understand that the changes, modifications, additions or substitutions made by ordinary technicians in this technical field within the essential scope of the present application do not depart from the purpose of the present application, and should also fall within the scope of protection of the claims of the present application.

Claims

1. A method for synthesizing fluorine-containing indazole derivatives, characterized in that: The following steps are involved: (1) The raw material 2,3-difluorobenzoic acid and the bromination reagent are reacted in a concentrated acid condition. After the reaction is completed, the reaction solution is cooled to room temperature, poured into ice water while stirring, and filtered after standing overnight. The wet product is dried by air to obtain 5-bromo-2,3-difluorobenzoic acid, which is recorded as compound I; (2) Compound I was dissolved in an organic solvent, and a catalyst, triethylamine and an amidation reagent were added. The mixture was stirred in an ice-water bath for 10 minutes and then moved to room temperature for reaction. After the reaction was completed, water was added and the mixture was extracted with ethyl acetate. The organic phase was washed with saturated brine, dried with a desiccant, and then the solvent was removed by reduced pressure distillation. The wet product was dried in vacuo to obtain 5-bromo-2,3-difluoro-N'-methoxy-N'-methylbenzamide, which was recorded as Compound II. (3) Compound II was dissolved in an organic solvent, and a Grignard reagent was added under nitrogen protection and an ice-water bath. After the addition was completed, the reaction was carried out at room temperature. After the reaction was completed, the pH was adjusted to 3-4, and the stirring was continued for 30 minutes. Then, the mixture was allowed to stand for stratification, and the solvent was removed from the upper layer by vacuum distillation. The crude product was redissolved in ethyl acetate, washed with saturated brine, dried with a desiccant, and then the ethyl acetate was removed by vacuum distillation. The wet product was vacuum dried to obtain 1-(5'-bromo-2',3'-difluorophenyl)ethane-1-one, which was recorded as compound III. (4) Compound III was added to an organic solvent and stirred to dissolve, hydrazine hydrate was added and the temperature was raised to 150°C for reflux reaction. After the reaction was completed, the reaction solution was cooled to room temperature, and then slowly poured into ice water with continuous stirring. After standing overnight, it was filtered, and the wet product was dried by air blowing to obtain 5-bromo-7-fluoro-3-methyl-1H-indazole, which was recorded as compound IV; (5) Compound IV is dissolved in an organic solvent, di-tert-butyl dicarbonate and triethylamine are added in sequence, and a catalyst is slowly added after stirring to dissolve, and the reaction is carried out at room temperature. After the reaction is completed, the solvent is removed by distillation under reduced pressure, and the crude product is redissolved in ethyl acetate until clear, washed with saturated brine, dried with a desiccant, and then the ethyl acetate is removed by distillation under reduced pressure. The wet product is dried in vacuo to obtain 1-(tert-butyloxycarbonyl)-5-bromo-7-fluoro-3-methyl-1H-indazole, which is recorded as compound V; (6) Compound V was added to an organic solvent and stirred to dissolve, and then vinylboronic acid pinacol ester, potassium carbonate, palladium catalyst, and water were added in sequence. The temperature was raised to 90°C under nitrogen protection for reaction. After the reaction was completed, the upper liquid was poured into water while hot and continued to be stirred, and then cooled to room temperature. Then, ethyl acetate was used for extraction, and the mixture was washed with saturated brine. After drying with a desiccant, the ethyl acetate was removed by vacuum distillation. The crude product was ultrasonically dissolved with petroleum ether, filtered, and then the petroleum ether was removed by vacuum distillation. The wet product was dried in vacuo to obtain 1-(tert-butyloxycarbonyl)-5-enyl-7-fluoro-3-methyl-1H-indazole, which was recorded as compound VI. (7) Compound VI is added to an organic solvent and stirred to dissolve, and then sodium bicarbonate and potassium permanganate are added in sequence. After the addition is completed, the mixture is moved to room temperature for reaction. After the reaction is completed, the mixture is filtered and dissolved with ethyl acetate. The pH is adjusted to 4-5 with dilute acid, and impurities are removed by filtration. The mixture is then washed with saturated brine and dried with a desiccant. The ethyl acetate is removed by vacuum distillation. The wet product is dissolved with an organic solvent and pulped twice, and then filtered. The wet product is dried under vacuum to obtain 1-(tert-butyloxycarbonyl)-7-fluoro-3-methyl-1H-indazole-5-carboxylic acid, which is recorded as compound VII.

2. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: The bromination reagent in step (1) includes one of NBS, DBH, PyHBr3, and carbon tetrabromide, and its amount is 1 to 2 times the molar amount of the raw material 2,3-difluorobenzoic acid; the concentrated acid is concentrated sulfuric acid; the reaction temperature is 60°C; the reaction time is 4 to 8 hours; and the drying temperature is 50°C.

3. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: In step (2), the organic solvent includes one or more of halogenated hydrocarbons, aromatic hydrocarbons, acetonitrile, esters, ketones, and dioxane; the catalyst includes one of a carbonium salt condensation agent, a phosphonium salt condensation agent, and an organic phosphorus condensation agent; the amidation agent is N-methyl-N-methoxyamine hydrochloride; the reaction time is 2 to 4 hours; and the vacuum drying temperature is 40°C.

4. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: In step (3), the organic solvent is tetrahydrofuran; the Grignard reagent is methylmagnesium bromide; and the vacuum drying temperature is 40°C.

5. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: In step (4), the organic solvent is N-methyl-2-pyrrolidone; the reflux reaction time is 3 to 5 h; and the drying temperature is 50°C.

6. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: In step (5), the organic solvent is dichloromethane; the catalyst is 4-dimethylaminopyridine; the reaction time is 3 to 5 h; and the vacuum drying temperature is 40°C.

7. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: In step (6), the organic solvent is 1,4-dioxane; the reaction time is 3-5 h; and the vacuum drying temperature is 40°C.

8. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: In step (7), the organic solvent for dissolving compound VI is acetone; and the reaction time is 10 to 12 h.

9. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: The organic solvent used for pulping in step (7) is a mixed solution of petroleum ether and ethyl acetate, and the mixed volume ratio is 10:

1.

10. The method for synthesizing a fluorine-containing indazole derivative according to claim 1, characterized in that: The vacuum drying temperature in step (7) is 40°C.

Images