A method for preparing high purity fluralaner

Abstract

The application relates to the technical field of medicines and discloses a preparation method of high-purity fluralaner, which comprises the following steps: S1, performing esterification reaction on 2-methyl-4-acetylbenzoic acid as a starting material compound I under the action of a condensing agent I to obtain a compound II; S2, performing nucleophilic addition reaction on the compound II and 3,5-dichloroacetophenone to obtain a compound III; performing dehydration and hydrolysis reaction on the compound III under the action of an organic base to obtain a compound IV; S3, performing ring closure reaction on the compound IV under the action of hydroxylamine to obtain a compound V; and S4, performing condensation reaction on the compound V under the action of a condensing agent II and 2-amino-N-(2,2,2-trifluoroethyl)acetamide hydrochloride to obtain the high-purity fluralaner. Through the technical scheme, the problems of low yield and low purity in the fluralaner synthesis process in the prior art are solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of medicine, in particular, it relates to a preparation method of high-purity fluralaner. BACKGROUND

[0002] Fluralaner is a broad-spectrum insecticide, which has good killing activity on pests such as ticks, fleas, lice, hemiptera and diptera. There is no known drug resistance and drug compatibility taboo, and there is no mutual drug resistance with existing insecticides. After oral administration, the drug is uniformly distributed on the body surface, and the effect of killing insects can reach more than 80% after 2 hours of oral administration, and the protection period can reach 12 weeks. Repeated infection can also achieve very good insect repellent effect, and the protection covers the complete flea life cycle.

[0003] At present, there are mainly three representative routes for the synthesis of fluralaner.

[0004] The first route is to use 2-methyl-4-formaldehyde oxime benzene acid tert-butyl ester as the starting material in patent application WO2009080250A2, which is subjected to chlorination, dipole addition, hydrolysis and condensation to obtain fluralaner. The raw materials used, 2-methyl-4-formaldehyde oxime benzene acid tert-butyl ester and 1,3-dichloro-5-(1-trifluoromethyl-vinyl) benzene, are both custom-made, which are expensive and have high cost.

[0005] The second route is to use 2-methyl-4-acetylbenzoic acid as the starting material in patent application WO2021105840A1, which is subjected to amide condensation, nucleophilic addition, dehydration and ring closure reaction to obtain fluralaner. The raw materials used are inexpensive and have sufficient supply. However, the conversion rate of this process is low, and the process involves long-time high-temperature reaction, and the yield is low, which also causes high cost.

[0006] The third route is to use 2-methyl-5-bromobenzoic acid as the starting material in patent application CN114315748A, which is subjected to Suzuki coupling reaction, condensation reaction, dehydration and cyclization reaction, and amide condensation reaction to obtain fluralaner. Among them, the catalyst used in Suzuki, palladium acetate, contains noble metal and is expensive. In addition, this patent uses column chromatography twice for purification, which is complex in process operation and greatly increases the cost.

[0007] In addition, the processes used in patent applications CN114394946A and CN115594645A use strong corrosive reagents such as oxalyl chloride and phosphorus oxychloride, and the finished product still contains more than 0.2% impurities. According to the Technical Guidelines for Research on Veterinary Chemical Drugs Impurities, more work needs to be done.

[0008] Therefore, the current synthesis process of fluorofelarnae has defects such as expensive materials, low yield and low purity. Therefore, it is particularly important to develop a synthesis route suitable for industrial scale production to overcome the obvious deficiencies in the prior art of fluorofelarnae synthesis process. SUMMARY

[0009] The present application provides a preparation method of high-purity fluorofelarnae, which solves the problems of low yield and low purity in the synthesis process of fluorofelarnae in the related art.

[0010] The technical scheme of the present application is as follows:

[0011] The present application provides a preparation method of high-purity fluorofelarnae, which solves the problems of low yield and low purity in the synthesis process of fluorofelarnae in the related art.

[0012] S1, 2-methyl-4-acetylbenzoic acid is used as a starting material compound I to perform esterification reaction under the action of condensing agent I to obtain compound II;

[0013]

[0014] S2, the compound II and 3, 5-dichloroacetophenone are subjected to nucleophilic addition reaction to obtain compound III;

[0015]

[0016] The compound III is subjected to dehydration and hydrolysis reaction under the action of an organic base to obtain compound IV;

[0017]

[0018] S3, the compound IV is subjected to ring closure reaction under the action of hydroxylamine to obtain compound V;

[0019]

[0020] S4, the compound V is subjected to condensation reaction with 2-amino-N-(2, 2, 2-trifluoroethyl) acetamide hydrochloride under the action of condensing agent II to obtain high-purity fluorofelarnae.

[0021]

[0022] As a further technical scheme, the molar ratio of compound I and condensing agent I in S1 is 1:1.

[0023] As a further technical scheme, the molar ratio of compound II and 3, 5-dichloroacetophenone and organic base in S2 is 1:1:1~3,

[0024] Preferably, the molar ratio of compound II and 3,5-dichloroacetophenone to the organic base is 1:1:1.5~2.

[0025] As a further technical solution, the molar ratio of compound IV to hydroxylamine in S3 is 1:1~2, preferably, the molar ratio of compound IV to hydroxylamine is 1:1.2~1.5.

[0026] As a further technical solution, the molar ratio of compound V to condensing agent II in S4 is 1:1.

[0027] As a further technical solution, the esterification reaction temperature in S1 is 10~30℃, and the esterification reaction time is 30~60min; the nucleophilic addition reaction temperature in S2 is 20~60℃, the nucleophilic addition reaction time is 8~24h, the dehydration and hydrolysis reaction temperature is 60~90℃, and the dehydration and hydrolysis reaction time is 4~6h; the ring closing reaction temperature in S3 is 20~30℃, and the ring closing reaction time is 8h; the condensation reaction temperature in S4 is 20~30℃, and the time is 1~2h, and the time is 1h.

[0028] As a further technical solution, the condensing agent I is one of CDI, SOCl2 and POCl3; the organic base is one of sodium ethoxide and sodium methoxide; the condensing agent II is one of HATU and DPPA.

[0029] As a further technical solution, the solvent for esterification reaction in S1 is dichloromethane; the solvent for nucleophilic addition reaction in S2 is tetrahydrofuran, and the catalyst is potassium carbonate; the solvent for ring closing reaction and condensation reaction in S3 and S4 is N,N-dimethylformamide, and the catalyst is one of triethylamine and tetrabutylammonium bromide.

[0030] As a further technical solution, the esterification reaction in S1 further includes recrystallization treatment; the nucleophilic addition reaction in S2 further includes extraction, washing, drying, and concentration treatment; the ring closing reaction in S3 further includes extraction, drying, and concentration treatment; the condensation reaction in S4 further includes extraction, washing, drying, concentration, and recrystallization treatment.

[0031] As a further technical solution, the recrystallization solvent in S1 is one of methanol, ethanol, isopropanol and acetonitrile;

[0032] The recrystallization solvent in S4 is a mixed solvent composed of A solvent-B solvent, and the volume ratio of A solvent to B solvent is 1~8:1, and the mixed solvent is one of n-hexane-ethyl acetate, n-hexane-acetone and methyl tert-butyl ether-acetone,

[0033] Preferably, the mixed solvent is n-hexane-ethyl acetate, and the volume ratio of n-hexane to ethyl acetate is 2~5:1.

[0034] The working principle and beneficial effects of the present application are as follows:

[0035] 1、In the present application, 2-methyl-4-acetylbenzoic acid is used as a starting material compound, and is combined with condensation, nucleophilic addition and other reactions, and then is subjected to one-pot processes such as recrystallization, dehydration and hydrolysis reaction, so that there is only one reaction site in each reaction, and the probability of impurity generation is small, so that each reaction can obtain a compound with high purity and yield, and at the same time, column chromatography or multiple crystallization processes are avoided, so that the synthesis and preparation process is simple and easy to operate, and finally high-purity fluralaner is obtained.

[0036] 2、In the present application, by adjusting the amounts of the intermediate compound, 3,5-dichloroacetophenone and organic base, and adjusting the amounts of the intermediate compound and hydroxylamine aqueous solution, the purity and yield of the intermediate compound can be significantly improved, so that the purity and yield of the final product fluralaner are improved.

[0037] 3、In the present application, n-hexane-ethyl acetate, n-hexane-acetone and methyl tert-butyl ether-acetone are respectively used as mixed solvents, by adjusting the proportion of the two solvents in the mixed solvent, it is found that when the mixed solvent is n-hexane-ethyl acetate, the purity of fluralaner is most significantly affected, and the fluralaner with the highest purity is prepared. DETAILED DESCRIPTION

[0038] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0039] In the following examples, the raw materials used and the manufacturers are shown in the following table:

[0040]

[0041] Example 1

[0042] A preparation method of high-purity fluralaner, comprising the following steps:

[0043] S1, compound I (2-methyl-4-acetylbenzoic acid, 17.81 g, 0.1 mol), dichloromethane (178 mL) was placed in a 500 mL two-necked flask, stirred to dissolve, slowly added CDI (16.21 g, 0.1 mol), and incubated for 45 min; TLC monitoring reaction end point (DCM: MeOH = 15:1), active intermediate conversion was completed, slowly added anhydrous ethanol (4.60 g, 0.1 mol), incubated at 25°C for 45 min; TLC monitoring reaction end point (DCM: MeOH = 15:1), after the reaction was completed, washed with purified water (50 mL x 2), saturated brine (50 mL x 1); the organic phase was collected, dried over anhydrous sodium sulfate, filtered, concentrated to a light yellow oil, recrystallized from anhydrous ethanol 54 mL, crystallized at 25°C for 2 h, filtered, collected white solid, dried at 60°C for 4 h, to obtain 19.82 g of compound II, the yield was 96.15%, the purity was 98.91%;

[0044] S2, compound II (19.82 g, 0.096 mol), 3,5-dichloroacetophenone (18.15 g, 0.096 mol), potassium carbonate (19.35 g, 0.14 mol), tetrahydrofuran (100 mL), stirred to dissolve; heated to 60°C, incubated for 8 h; TLC monitoring reaction end point (HEX: EA = 5:1), after the reaction was completed, added 100 mL of water, extracted with 50 mL of ethyl acetate twice, combined the organic phase, and washed with 50 mL of water; the organic phase was collected, dried over anhydrous sodium sulfate, and concentrated to a light yellow oil to obtain compound III;

[0045] Compound III was dissolved in 100 mL of anhydrous ethanol; heated to 70°C, slowly added sodium ethoxide (9.53 g, 0.14 mol), incubated for 5 h; TLC monitoring reaction end point (DCM: MeOH = 20:1), after the reaction was completed, cooled to room temperature, added 300 mL of water, extracted with 50 mL of ethyl acetate twice, collected the aqueous phase; the aqueous phase was adjusted to pH = 3-4 with hydrochloric acid, a large amount of white solid was precipitated, and stirring was continued for 2 h; filtered, collected the solid, dried at 60°C for 5 h; to obtain 35.78 g of compound IV, the purity was 97.29%, the yield was 82.87%; (calculated with compound II as reference);

[0046] S3, Compound IV (35.78 g, 0.089 mol), DMF 179 mL, was dissolved at 30°C; tetrabutylammonium bromide (5.74 g, 0.018 mol) was added to the solution; 50% mass concentration of hydroxylamine aqueous solution (8.59 g, 0.13 mol) was added dropwise; the reaction was incubated at 30°C for 8 h; TLC was used to monitor the end point of the reaction (DCM:MeOH=20:1), 1M hydrochloric acid was added to adjust pH=3~4, dichloromethane 90 mL*2 was added for extraction, the combined organic phase was dried over anhydrous sodium sulfate, and then concentrated to obtain a light yellow oil; anhydrous ethanol 54 mL was added for recrystallization, and the crystal was precipitated at 25°C for 2 h, then filtered, and the white solid was collected and dried at 60°C for 4 h to obtain 37.59 g of compound V with a purity of 99.76% and a yield of 89.89%;

[0047] S4, Preparation of filtrate A: 2-amino-N-(2,2,2-trifluoroethyl)acetamide hydrochloride (19.26 g, 0.1 mol) was dissolved in 50 mL of DMF, triethylamine (10.11 g, 0.1 mol) was added dropwise, stirred at 20°C for 30 min, filtered, and the filtrate was obtained as filtrate A;

[0048] Preparation of solution B: Compound V (37.59 g, 0.09 mol) was dissolved in 50 mL of DMF; HATU (38.02 g, 0.1 mol) was added at 30°C, and the end point of the reaction was monitored by TLC (DCM:MeOH=20:1); the reaction was carried out for 1 h to obtain solution B;

[0049] Solution A was added dropwise to solution B, and the reaction was carried out at 30°C for 1 h; the end point of the reaction was monitored by TLC (DCM:MeOH=20:1); after the reaction was completed, 200 mL of water was added, and 50 mL*2 of ethyl acetate was used for extraction, and the combined organic phase was washed with 50 mL*2 of water, dried over anhydrous sodium sulfate, and concentrated to obtain a light yellow oil;

[0050] 110 mL of a mixed solution (n-hexane:ethyl acetate=5:1) was added to the light yellow oil, which was dissolved at 60°C for 30 min; it was slowly cooled to room temperature, and the crystal was precipitated for 3 h; the solid was collected and moved to 60°C for vacuum drying for 5 h to obtain fluorofelarnet with a purity of 99.97% and a yield of 76.43%.

[0051] Example 2

[0052] A method for preparing high-purity fluorofelarnet, comprising the following steps:

[0053] S1, compound I (2-methyl-4-acetylbenzoic acid, 17.81 g, 0.1 mol), dichloromethane (178 mL) were placed in a 500 mL two-necked flask, and stirred to dissolve at 30°C, and then SOCl2 (11.89 g, 0.1 mol) was slowly added, and the reaction was kept for 30 min; TLC was used to monitor the end of the reaction (DCM:MeOH=15:1), and the active intermediate was completely converted, and then anhydrous ethanol (4.60 g, 0.1 mol) was slowly added dropwise, and the reaction was kept for 30 min at 30°C; TLC was used to monitor the end of the reaction (DCM:MeOH=15:1), and then the reaction was completed, and then purified water (50 mL x 2), saturated brine (50 mL x 1) were used for washing; the organic phase was collected, dried over anhydrous sodium sulfate, filtered, concentrated to a light yellow oil, and then recrystallized from anhydrous methanol 54 mL, and crystallized at 25°C for 2 h, filtered, and the white solid was collected, and dried at 60°C for 4 h, to obtain 19.03 g of compound II, with a yield of 92.27% and a purity of 98.34%;

[0054] S2, compound II (16.31 g, 0.079 mol), 3,5-dichloroacetophenone (23.09 g, 0.079 mol), potassium carbonate (16.59 g, 0.12 mol), tetrahydrofuran (90 mL) were stirred to dissolve, and then the temperature was increased to 20°C, and the reaction was kept for 24 h; TLC was used to monitor the end of the reaction (HEX:EA=5:1), and then the reaction was completed, and then 90 mL of water was added, and 50 mL of ethyl acetate was used for extraction twice, and then the organic phase was collected, dried over anhydrous sodium sulfate, and concentrated to obtain a light yellow oil, to obtain compound III;

[0055] Compound III was dissolved in 90 mL of anhydrous ethanol, and then the temperature was increased to 70°C, and potassium ethoxide (10.89 g, 0.16 mol) was slowly added, and the reaction was kept for 5 h; TLC was used to monitor the end of the reaction (DCM:MeOH=20:1), and then the reaction was completed, and then the temperature was decreased to room temperature, and 270 mL of water was added, and 45 mL of ethyl acetate was used for extraction twice, and then the aqueous phase was collected; the aqueous phase was adjusted to pH=3-4 with hydrochloric acid, and a large amount of white solid was precipitated, and the stirring was continued for 2 h; the solid was collected by filtration, and dried at 60°C for 5 h; 32.57 g of compound IV was obtained, with a purity of 96.33% and a yield of 91.67% (calculated with reference to compound II)

[0056] S3, Compound IV (20 g, 0.045 mol), DMF 100 mL, was dissolved at 20 °C; tetrabutylammonium bromide (2.90 g, 0.009 mol) was added to the solution; 50% mass concentration hydroxylamine aqueous solution (3.56 g, 0.054 mol) was added dropwise; the reaction was incubated at 20 °C for 8 h; TLC was used to monitor the end point of the reaction (DCM:MeOH=20:1), 1M hydrochloric acid was added to adjust pH=3~4, dichloromethane 50 mL x 2 was added for extraction, the combined organic phase was dried over anhydrous sodium sulfate, and then concentrated to obtain a light yellow oil;

[0057] Recrystallization was performed by adding anhydrous ethanol 54 mL, and the crystal was precipitated at 25 °C for 2 h; white solid was collected by filtration, and vacuum drying was performed at 60 °C for 4 h to obtain 16.32 g of compound V with a purity of 93.76% and a yield of 90.92%;

[0058] S4, Preparation of filtrate A: 2-amino-N-(2,2,2-trifluoroethyl)acetamide hydrochloride (7.89 g, 0.041 mol) was dissolved in 30 mL of DMF, triethylamine (4.15 g, 0.041 mol) was added dropwise, and stirring was performed at 30 °C for 30 min; the filtrate was obtained by filtration to obtain filtrate A;

[0059] Preparation of solution B: Compound V (15 g, 0.037 mol) was dissolved in 30 mL of DMF; DPPA (15.55 g, 0.041 mol) was added at 20 °C, and TLC was used to monitor the end point of the reaction (DCM:MeOH=20:1); the reaction was performed for 2 h to obtain solution B;

[0060] Solution A was added dropwise to solution B, and the reaction was performed at 20 °C for 1 h; TLC was used to monitor the end point of the reaction (DCM:MeOH=20:1); after the reaction was completed, 100 mL of water was added, and 50 mL x 2 of ethyl acetate was used for extraction, and the combined organic phase was washed with 50 mL x 2 of water, dried over anhydrous sodium sulfate, and concentrated to obtain a light yellow oil;

[0061] 45 mL of a mixed solution (n-hexane:ethyl acetate=2:1) was added to the light yellow oil, and the solution was dissolved at 60 °C for 30 min; the temperature was slowly lowered to room temperature, and the crystal was precipitated for 3 h; the solid was collected and moved to 60 °C for vacuum drying for 5 h to obtain fluorofelarnet with a purity of 99.92% and a yield of 78.32%.

[0062] Example 3

[0063] A method for preparing high-purity fluorofelarnet, comprising the following steps:

[0064] S1, compound I (2-methyl-4-acetylbenzoic acid, 17.81 g, 0.1 mol), dichloromethane (178 mL) were placed in a 500 mL two-necked flask, and stirred to dissolve at 10°C, POCl3 (15.33 g, 0.1 mol) was slowly added, and the reaction was kept for 60 min; TLC was used to monitor the end of the reaction (DCM:MeOH=15:1), and the active intermediate was completely converted, anhydrous ethanol (4.60 g, 0.1 mol) was slowly added dropwise, and the reaction was kept for 60 min at 10°C; TLC was used to monitor the end of the reaction (DCM:MeOH=15:1), and the reaction was completed, then purified water (50 mL x 2), saturated brine (50 mL x 1) were used for washing; the organic phase was collected, dried over anhydrous sodium sulfate, filtered, concentrated to a light yellow oil, recrystallized from isopropanol 54 mL, crystallized at 25°C for 2 h, filtered, and the white solid was collected, dried at 60°C for 4 h, to obtain 19.29 g of compound II, with a yield of 93.53% and a purity of 97.39%;

[0065] S2, compound II (14.59 g, 0.071 mol), 3,5-dichloroacetophenone (18.95 g, 0.071 mol), potassium carbonate (15.20 g, 0.11 mol), tetrahydrofuran (73 mL) were stirred to dissolve; the temperature was raised to 40°C, and the reaction was kept for 10 h; TLC was used to monitor the end of the reaction (HEX:EA=5:1), and the reaction was completed, then 73 mL of water was added, extracted with 36 mL x 2 of ethyl acetate, and the organic phase was collected; the organic phase was dried over anhydrous sodium sulfate, concentrated to a light yellow oil, and compound III was obtained;

[0066] Compound III was dissolved in 73 mL of anhydrous ethanol; the temperature was raised to 70°C, sodium ethoxide (14.29 g, 0.21 mol) was slowly added, and the reaction was kept for 5 h; TLC was used to monitor the end of the reaction (DCM:MeOH=20:1), and the reaction was completed, then the temperature was lowered to room temperature, 270 mL of water was added, extracted with 36 mL x 2 of ethyl acetate, and the aqueous phase was collected; the aqueous phase was adjusted to pH=3-4 with hydrochloric acid, a large amount of white solid was precipitated, and the stirring was continued for 2 h; the solid was collected by filtration, and dried at 60°C for 5 h; 28.69 g of compound IV was obtained, with a purity of 95.08% and a yield of 90.27%; (calculated with reference to compound II);

[0067] S3, Compound IV (15 g, 0.033 mol), DMF 75 mL, was dissolved at 20 °C; tetrabutylammonium bromide (2.13 g, 0.006 mol) was added to the solution; 50% mass concentration of hydroxylamine aqueous solution (2.18 g, 0.033 mol) was added dropwise; 30 °C incubation reaction was carried out for 8 h; TLC was used to monitor the end of the reaction (DCM:MeOH=20:1), 1M hydrochloric acid was added to adjust pH=3~4, dichloromethane 38 mL x 2 was added for extraction, the combined organic phase was dried over anhydrous sodium sulfate, and then concentrated to obtain a light yellow oil;

[0068] Recrystallization was carried out by adding 54 mL of anhydrous ethanol, and the white solid was collected by filtration and dried at 60 °C under vacuum for 4 h to obtain 11.69 g of compound V with a purity of 92.69% and a yield of 86.83%;

[0069] S4, Preparation of filtrate A: 2-amino-N-(2,2,2-trifluoroethyl)acetamide hydrochloride (5.39 g, 0.028 mol) was dissolved in 50 mL of DMF, triethylamine (2.83 g, 0.028 mol) was added dropwise, and stirred at 20 °C for 30 min, then filtered to obtain filtrate A;

[0070] Preparation of solution B: Compound V (10 g, 0.025 mol) was dissolved in 20 mL of DMF; HATU (7.71 g, 0.028 mol) was added at 30 °C, and TLC was used to monitor the end of the reaction (DCM:MeOH=20:1), and the reaction was carried out for 1 h to obtain solution B;

[0071] Solution A was added dropwise to solution B, and the reaction was carried out at 30 °C for 1 h; TLC was used to monitor the end of the reaction (DCM:MeOH=20:1); after the reaction was completed, 80 mL of water was added, and 30 mL x 2 of ethyl acetate was used for extraction, and the combined organic phase was washed with 40 mL x 2 of water, dried over anhydrous sodium sulfate, and concentrated to obtain a light yellow oil with a purity of 98.92%;

[0072] To the light yellow oil, 30 mL of a mixed solution (methyl tert-butyl ether:acetone=5:1) was added, and the solution was dissolved at 60 °C for 30 min; it was slowly cooled to room temperature, and the solid was collected after crystallization for 3 h, and then moved to 60 °C for vacuum drying for 5 h to obtain fluralaner with a purity of 99.89% and a yield of 74.46%.

[0073] Example 4

[0074] The difference between this example and example 3 is that 30 mL of a mixed solution of n-hexane-acetone with a molar ratio of 5:1 is added, and fluralaner with a purity of 99.78% and a yield of 75.08% is obtained.

[0075] Example 5

[0076] The only difference between this example and Example 3 is that 30 mL of a mixed solution with a molar ratio of 8:1 (n-hexane-ethyl acetate) was added, resulting in a Freranar with a purity of 99.82% and a yield of 77.09%.

[0077] Example 6

[0078] The only difference between this embodiment and Example 1 is in the method for preparing high-purity fluorenazine:

[0079] S2. Compound II (10.00 g, 0.048 mol), 3,5-dichloroacetophenone (23.33 g, 0.096 mol), potassium carbonate (9.96 g, 0.072 mol), and tetrahydrofuran (50 mL) were stirred until dissolved. The mixture was heated to 60 °C and kept at that temperature for 8 h. The reaction endpoint was monitored by TLC (HEX:EA = 5:1). After the reaction was complete, 50 mL of water was added, and the mixture was extracted with 50 mL of ethyl acetate twice. The organic phases were combined and washed with 50 mL of water. The organic phase was collected, dried over anhydrous sodium sulfate, and concentrated to obtain a pale yellow oily substance, which yielded compound III.

[0080] Compound III was dissolved in 100 mL of anhydrous ethanol; the temperature was raised to 70 °C, and sodium ethoxide (4.90 g, 0.072 mol) was slowly added. The reaction was maintained at this temperature for 5 h. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). After the reaction was completed, the temperature was lowered to room temperature, 150 mL of water was added, and the mixture was extracted with 25 mL of ethyl acetate twice. The aqueous phase was collected. The pH of the aqueous phase was adjusted to 3-4 with hydrochloric acid, and a large amount of white solid precipitated. The mixture was stirred for another 2 h. The solid was collected by filtration and dried at 60 °C for 5 h. 19.32 g of compound IV was obtained, with a purity of 86.44% and a yield of 88.69% (calculated with compound II as a reference).

[0081] S3. Compound IV (10 g, 0.022 mol) and DMF (100 mL) were dissolved at 30 °C. Tetrabutylammonium bromide (1.42 g, 0.0044 mol) was added to the solution. Hydroxylamine aqueous solution (1.72 g, 0.026 mol) with a mass concentration of 50% was added dropwise. The reaction was carried out at 30 °C for 8 h. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). 1 M hydrochloric acid was added to adjust the pH to 3-4. Dichloromethane (50 mL × 2) was added for extraction. The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated to obtain a pale yellow oil.

[0082] Recrystallization was performed by adding 54 mL of anhydrous ethanol and crystallizing at 25 °C for 2 h. The crystals were then filtered, and the white solid was collected and dried under vacuum at 60 °C for 4 h to obtain 6.97 g of compound V with a purity of 82.32% and a yield of 77.66%.

[0083] S4. Preparation of filtrate A: Dissolve 2-amino-N-(2,2,2-trifluoroethyl)acetamide hydrochloride (2.50 g, 0.013 mol) in 10 mL of DMF, add triethylamine (1.32 g, 0.013 mol) dropwise, stir at 20 °C for 30 min, filter, and collect the filtrate to obtain filtrate A;

[0084] Preparation of solution B: Compound V (5 g, 0.012 mol) was dissolved in 10 mL of DMF; HATU (4.94 g, 0.013 mol) was added at 30 °C, and the reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). The reaction was carried out for 1 hour to obtain solution B.

[0085] Solution A was added dropwise to solution B and reacted at 30°C for 1 h. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). After the reaction was complete, 50 mL of water was added and the mixture was extracted with ethyl acetate (25 mL × 2). The organic phases were combined. The organic phases were washed with water (25 mL × 2) and dried with anhydrous sodium sulfate. The mixture was then concentrated to obtain a pale yellow oil.

[0086] 110 mL of a mixed solution (methyl tert-butyl ether: acetone = 4:1) was added to the pale yellow oily substance, and the solution was dissolved at 60 °C and kept at this temperature for 30 min. The solution was then slowly cooled to room temperature and allowed to crystallize for 3 h. The solid was collected and dried under vacuum at 60 °C for 5 h to obtain freranar with a purity of 98.62% and a yield of 56.97%.

[0087] Example 7

[0088] The only difference between this embodiment and Example 1 is in the method for preparing high-purity fluorenazine:

[0089] S2. Compound II (15 g, 0.073 mol), 3,5-dichloroacetophenone (17.74 g, 0.073 mol), potassium carbonate (15.21 g, 0.11 mol), and tetrahydrofuran (75 mL) were stirred until dissolved. The mixture was heated to 60 °C and kept at that temperature for 8 h. The reaction endpoint was monitored by TLC (HEX:EA = 5:1). After the reaction was complete, 75 mL of water was added, and the mixture was extracted with 50 mL × 2 ethyl acetate. The organic phases were combined and washed with 50 mL of water. The organic phase was collected, dried over anhydrous sodium sulfate, and concentrated to obtain a pale yellow oily substance, which yielded compound III.

[0090] Compound III was dissolved in 75 mL of anhydrous ethanol; the temperature was raised to 70 °C, and sodium hydroxide (4.4 g, 0.11 mol) was slowly added. The reaction was maintained at this temperature for 5 h. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). After the reaction was completed, the temperature was lowered to room temperature, 200 mL of water was added, and the mixture was extracted with 35 mL × 2 ethyl acetates. The aqueous phase was collected. The pH of the aqueous phase was adjusted to 3-4 with hydrochloric acid, and a large amount of white solid precipitated. The mixture was stirred for another 2 h. The solid was collected by filtration and dried at 60 °C for 5 h. 25.98 g of compound IV was obtained, with a purity of 77.29% and a yield of 79.51% (calculated with compound II as a reference).

[0091] S3. Compound IV (20 g, 0.045 mol) and DMF (100 mL) were dissolved at 20 °C. Tetrabutylammonium bromide (2.90 g, 0.009 mol) was added to the solution. Hydroxylamine aqueous solution (3.56 g, 0.09 mol) with a mass concentration of 50% was added dropwise. The reaction was carried out at 20 °C for 8 h. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). 1 M hydrochloric acid was added to adjust the pH to 3-4. Dichloromethane (50 mL × 2) was added for extraction. The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated to obtain a pale yellow oil.

[0092] Recrystallization was performed by adding 54 mL of anhydrous ethanol and crystallizing at 25 °C for 2 h. The crystals were then filtered, and the white solid was collected and dried under vacuum at 60 °C for 4 h to obtain 13.69 g of compound V with a purity of 80.36% and a yield of 76.27%.

[0093] S4. Preparation of filtrate A: Dissolve 5.39 g (0.028 mol) of 2-amino-N-(2,2,2-trifluoroethyl)acetamide hydrochloride in 50 mL of DMF, add triethylamine (2.83 g, 0.028 mol) dropwise, stir at 20 °C for 30 min, filter, and collect the filtrate to obtain filtrate A;

[0094] Preparation of solution B: Compound V (10 g, 0.025 mol) was dissolved in 20 mL of DMF; HATU (7.71 g, 0.028 mol) was added at 30 °C, and the reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). The reaction was carried out for 1 hour to obtain solution B.

[0095] Solution A was added dropwise to solution B, and the reaction was carried out at 30°C for 1 hour. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). After the reaction was completed, 80 mL of water was added, and the mixture was extracted with ethyl acetate (30 mL × 2). The organic phases were combined. The organic phases were washed with water (40 mL × 2), dried over anhydrous sodium sulfate, and concentrated to obtain a pale yellow oil with a purity of 98.92%.

[0096] Add 30 mL of a mixed solution (n-hexane:acetone = 1:1) to the pale yellow oily substance, dissolve it at 60 °C, and keep warm for 30 min; slowly cool to room temperature, crystallize for 3 h, collect the solid, transfer it to 60 °C and vacuum dry for 5 h to obtain freranar with a purity of 96.27% and a yield of 58.36%.

[0097] Example 8

[0098] The only difference between this embodiment and Example 1 is in the method for preparing high-purity fluorenazine:

[0099] S2. Compound II (15 g, 0.073 mol), 3,5-dichloroacetophenone (17.74 g, 0.073 mol), potassium carbonate (15.21 g, 0.11 mol), and tetrahydrofuran (75 mL) were stirred until dissolved. The mixture was heated to 60 °C and kept at that temperature for 8 h. The reaction endpoint was monitored by TLC (HEX:EA = 5:1). After the reaction was complete, 75 mL of water was added, and the mixture was extracted with 50 mL × 2 ethyl acetate. The organic phases were combined and washed with 50 mL of water. The organic phase was collected, dried over anhydrous sodium sulfate, and concentrated to obtain a pale yellow oily substance, which yielded compound III.

[0100] Compound III was dissolved in 75 mL of anhydrous ethanol; the temperature was raised to 70 °C, and sodium ethoxide (7.49 g, 0.11 mol) was slowly added. The reaction was maintained at this temperature for 5 h. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). After the reaction was completed, the temperature was lowered to room temperature, 200 mL of water was added, and the mixture was extracted with 35 mL × 2 ethyl acetate. The aqueous phase was collected. The pH of the aqueous phase was adjusted to 3-4 with hydrochloric acid, and a large amount of white solid precipitated. The mixture was stirred for another 2 h. The solid was collected by filtration and dried at 60 °C for 5 h. 26.68 g of compound IV was obtained, with a purity of 96.89% and a yield of 82.26% (calculated with compound II as a reference).

[0101] S3. Compound IV (20 g, 0.045 mol) and DMF (100 mL) were dissolved at 20 °C. Tetrabutylammonium bromide (2.90 g, 0.009 mol) was added to the solution. Hydroxylamine aqueous solution (3.56 g, 0.054 mol) with a mass concentration of 50% was added dropwise. The reaction was carried out at 20 °C for 8 h. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). 1 M hydrochloric acid was added to adjust the pH to 3-4. Dichloromethane (50 mL × 2) was added for extraction. The organic phases were combined, dried over anhydrous sodium sulfate, and concentrated to obtain a pale yellow oil.

[0102] Recrystallization was performed by adding 54 mL of anhydrous ethanol and crystallizing at 25 °C for 2 h. The crystals were then filtered, and the white solid was collected and dried under vacuum at 60 °C for 4 h to obtain 16.55 g of compound V with a purity of 98.33% and a yield of 92.20%.

[0103] S4. Preparation of filtrate A: Dissolve 5.39 g (0.028 mol) of 2-amino-N-(2,2,2-trifluoroethyl)acetamide hydrochloride in 50 mL of DMF, add triethylamine (2.83 g, 0.028 mol) dropwise, stir at 20 °C for 30 min, filter, and collect the filtrate to obtain filtrate A;

[0104] Preparation of solution B: Compound V (10 g, 0.025 mol) was dissolved in 20 mL of DMF; HATU (7.71 g, 0.028 mol) was added at 30 °C, and the reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). The reaction was carried out for 1 hour to obtain solution B.

[0105] Solution A was added dropwise to solution B, and the reaction was carried out at 30°C for 1 hour. The reaction endpoint was monitored by TLC (DCM:MeOH = 20:1). After the reaction was completed, 80 mL of water was added, and the mixture was extracted with ethyl acetate (30 mL × 2). The organic phases were combined. The organic phases were washed with water (40 mL × 2), dried over anhydrous sodium sulfate, and concentrated to obtain a pale yellow oil with a purity of 98.92%.

[0106] Add 30 mL of a mixed solution (n-hexane:acetone = 2:1) to the pale yellow oily substance, dissolve it at 60 °C and keep warm for 30 min; slowly cool to room temperature and crystallize for 3 h, collect the solid, transfer it to 60 °C and vacuum dry for 5 h to obtain freranar with a purity of 95.65% and a yield of 55.66%.

[0107] The purity of the fluranar prepared in Examples 1-8 above was determined by HPLC-PDA. The detection conditions were as follows: mobile phase A: 0.03% TFA, mobile phase B: acetonitrile; diluent: acetonitrile; chromatographic column: Thermo ODS Hypersil C18, column temperature: 35℃.

[0108] Comparing the data from Examples 1-8, it was found that the intermediate compound IV obtained in step S2 of Examples 1-2 had higher purity and yield compared to Examples 6-7, indicating that adjusting the amounts of the intermediate compound, 3,5-dichloroacetophenone, and organic base could significantly improve the purity and yield of the intermediate compound. Compared to Examples 3 and 7, the intermediate compound V obtained in step S3 of Examples 1-2 had higher purity and yield, indicating that adjusting the amount of hydroxylamine aqueous solution could improve the purity and yield of the intermediate compound, as well as the purity and yield of the final product, freranal.

[0109] Compared with Examples 3-8, the fluorenarian prepared in Examples 1-2 had higher purity, indicating that adjusting the ratio of the two solvents in the mixed solvent and using n-hexane-ethyl acetate as the mixed solvent had the most significant impact on the purity of fluorenarian, resulting in the highest purity fluorenarian.

[0110] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing fluorellanar, characterized in that, Includes the following steps: S1. Compound I, using 2-methyl-4-acetylbenzoic acid as the starting material, undergoes an esterification reaction under the action of condensing agent I to obtain compound II; S2. Compound II and 3,5-dichloro-2,2,2-trifluoroacetophenone are subjected to a nucleophilic addition reaction to obtain compound III; Compound III was subjected to dehydration and hydrolysis under the action of an organic base to obtain compound IV; S3. Compound IV undergoes a ring-closing reaction under the action of hydroxylamine to obtain compound V; S4. Compound V is subjected to a condensation reaction with 2-amino-N-(2,2,2-trifluoroethyl)acetamide hydrochloride under the action of condensing agent II to obtain freranar; The organic base is one of sodium ethoxide and sodium methoxide; The structural formula of compound I is: ； The structural formula of compound II is: ； The structural formula of compound III is: ； The structural formula of compound IV is: ； The structural formula of compound V is: 。 2. The method for preparing fluorellaranoside according to claim 1, characterized in that, The molar ratio of compound I and condensing agent I in S1 is 1:

1.

3. The method for preparing fluorellaranoside according to claim 1, characterized in that, In S2, the molar ratio of compound II and 3,5-dichloro-2,2,2-trifluoroacetophenone to the organic base is 1:1:1.5~2.

4. The method for preparing freranal according to claim 1, characterized in that, In S3, the molar ratio of compound IV to hydroxylamine is 1:1.2~1.

5.

5. The method for preparing fluorellaranol according to claim 1, characterized in that, The molar ratio of compound V to condensing agent II in S4 is 1:

1.

6. The method for preparing freranil as described in claim 1, characterized in that, In S1, the esterification reaction temperature is 10~30℃ and the esterification reaction time is 30~60min; in S2, the nucleophilic addition reaction temperature is 20~60℃ and the nucleophilic addition reaction time is 8~24h; the dehydration and hydrolysis reaction temperature is 60~90℃ and the dehydration and hydrolysis reaction time is 4~6h; in S3, the ring-closing reaction temperature is 20~30℃ and the ring-closing reaction time is 8h; in S4, the condensation reaction temperature is 20~30℃ and the time is 1~2h.

7. The method for preparing fluorellaranoside according to claim 1, characterized in that, The condensing agent I is one of CDI, SOCl2 and POCl3; the condensing agent II is one of HATU and DPPA.

8. The method for preparing fluorellaranoside according to claim 1, characterized in that, The solvent for the esterification reaction in S1 is dichloromethane; the solvent for the nucleophilic addition reaction in S2 is tetrahydrofuran, and the catalyst is potassium carbonate; the solvent for the ring-closing reaction and the condensation reaction in S3 and S4 is N,N-dimethylformamide, and the catalyst is one of triethylamine and tetrabutylammonium bromide.

9. The method for preparing fluorellaranoside according to claim 1, characterized in that, The esterification reaction in S1 is followed by recrystallization; the nucleophilic addition reaction in S2 is followed by extraction, washing, drying, and concentration; the ring-closing reaction in S3 is followed by extraction, drying, and concentration; and the condensation reaction in S4 is followed by extraction, washing, drying, concentration, and recrystallization.

10. The method for preparing freranil according to claim 9, characterized in that, The recrystallization solvent in S1 is one of methanol, ethanol, isopropanol, and acetonitrile. The recrystallization solvent in S4 is a mixed solvent composed of solvent A and solvent B, with a volume ratio of solvent A to solvent B of 1 to 8:

1.

11. The method for preparing freranil as described in claim 10, characterized in that, The mixed solvent is n-hexane-ethyl acetate, with a volume ratio of n-hexane to ethyl acetate of 2~5:1.

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