Preparation method of Nitisinone

Abstract

The invention discloses a method for preparing nitisinone, and belongs to the technical field of drug synthesis. It comprises: in the presence of anhydrous potassium fluoride, 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione undergo condensation reaction in an organic solvent to obtain nitisinone. The method for preparing nitisinone provided by the invention avoids the use of highly toxic and highly polluting reagents containing cyano groups, and in the presence of anhydrous potassium fluoride, improves the selectivity of the condensation reaction, and the crude nitisinone obtained by the reaction is then recrystallized and refined using a mixed solvent of acetone and water, so that a nitisinone raw material drug that meets the requirements of the current quality standards can be obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of drug synthesis, and in particular to a method for preparing nitisinone. Background Art

[0002] Nitisinone is an HPPD inhibitor that inhibits the normal metabolism of tyrosine in HT-1 patients, thereby preventing the accumulation of the extremely toxic maleylacetoacetate, fumarylacetoacetate and their bypass metabolites succinylacetone. It is suitable for hereditary tyrosinemia type 1 (HT-1).

[0003] At present, the common strategy for the preparation of nitisinone is to first prepare 2-nitro-4-trifluoromethylbenzoic acid into a carboxylic acid derivative (acyl chloride or methyl ester), and then condense it with 1,3-cyclohexanedione to obtain nitisinone. However, the condensation reaction is competed by the esterification side reaction, which will reduce the purity and separation yield of the product. The reaction equation is:

[0004]

[0005] When only inorganic base is used to promote the condensation reaction (US9783485), the yield of a single step is less than 50%. Studies have found that 10-20% of the enol ester isomer will be produced in the first 3 hours of the reaction. As the reaction continues, the enol ester isomer is hydrolyzed into 2-nitro-4-trifluoromethylbenzoic acid and 1,3-cyclohexanedione, which greatly reduces the conversion rate of the raw materials.

[0006] In order to convert ester isomers into nitisinone to improve the conversion rate and separation yield of the substrate, US5550165 and WO2015101794 use the organic cyanide trimethylsilyl cyanide (TMSCN) as a catalyst to obtain an ideal result of 85% single-step reaction yield and 95% purity. The reaction can also use the organic cyanide acetone cyanohydrin (Organic & Biomolecular Chemistry, 2021, 19 (47), 10432-10443) as a catalyst for converting ester isomers. However, organic cyanides are easily hydrolyzed to produce extremely toxic hydrocyanic acid, and their use does not meet the development requirements of modern pharmaceuticals for environmental friendliness and safe production.

[0007] CN201210492081.2 developed a method for promoting the conversion of the isomers using an aluminum chloride and triethylamine system, and obtained high-purity nitisinone, but did not report the separation yield of the method. Studies have found that after the reaction is subjected to a condensation reaction with the participation of an inorganic base and purified, the isomers are converted by reacting with aluminum chloride and triethylamine, and the molar yield of the two-step reaction is less than 50% (calculated from 2-nitro-4-trifluoromethylbenzoic acid).

[0008] In view of the above problems, it is necessary to provide a new method for preparing nitisinone. Summary of the invention

[0009] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and to propose a method for preparing Nitisinone.

[0010] The present invention is achieved in that:

[0011] The invention provides a method for preparing nitisinone, which comprises: in the presence of anhydrous potassium fluoride, 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione undergo condensation reaction in an organic solvent to obtain nitisinone.

[0012] The present invention has the following beneficial effects:

[0013] The present invention provides a method for preparing nitisinone, which comprises: in the presence of anhydrous potassium fluoride, 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione undergo a condensation reaction in an organic solvent to obtain nitisinone. The method for preparing nitisinone provided by the present invention avoids the use of highly toxic and highly polluting reagents containing cyano groups. The participation of anhydrous potassium fluoride improves the selectivity of the condensation reaction, and can convert the enol ester isomer produced in the condensation reaction of 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione into nitisinone, thereby improving the yield of nitisinone. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0015] Figure 1 is the H NMR spectrum of Nitisinone in Example 1;

[0016] Figure 2 This is the NMR carbon spectrum of Nitisinone in Example 1. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. If the manufacturer of the reagents or instruments used is not specified, they are all conventional products that can be purchased commercially.

[0018] The object of the present invention is to provide a method for preparing nitisinone.

[0019] In order to achieve the above-mentioned purpose of the present invention, the following technical scheme is specially adopted.

[0020] An embodiment of the present invention provides a method for preparing nitisinone, comprising: in the presence of anhydrous potassium fluoride, 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione undergo a condensation reaction in an organic solvent to obtain nitisinone.

[0021] Recently, there are also literature reports on the synthesis of Nitisinone at home and abroad, but the public literature only briefly introduces the preparation method of Nitisinone without detailed description. In addition, in the synthesis process of Nitisinone, toxic and harmful trimethylsilyl cyanide (TMSCN) is used as a catalyst to obtain a higher yield and purity, or other catalysts are used to avoid the use of toxic and harmful catalysts, but the yield of Nitisinone is low. How to avoid the use of toxic and harmful catalysts while obtaining Nitisinone with higher purity and yield is an urgent problem to be solved in this field. After long-term practice, the inventor proposed a new synthesis method of Nitisinone, which is to obtain Nitisinone by condensing 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione in the presence of anhydrous potassium fluoride and an organic solvent. The participation of anhydrous potassium fluoride, on the one hand, has a sufficiently weak alkalinity to ensure that the kinetically controlled product enol ester is suppressed to a lower level, and on the other hand, the fluoride ions participate in the exchange, which can convert the enol ester isomers into product structures to increase the yield of nitisinone. It can be seen that the synthesis method of nitisinone provided by the embodiment of the present invention shortens the synthesis route, successfully avoids the use of cyanide, and solves the current problem of large product toxicity residue and large side effects when taken due to the use of toxic and harmful trimethylsilyl cyanide (TMSCN) as a catalyst, which not only improves the safety and stability of experimental operations, but more importantly, improves the safety and stability of nitisinone when taken. At the same time, the use of inorganic weak base anhydrous potassium fluoride to prepare nitisinone has good reaction selectivity and conversion rate. It can be seen that the preparation method of nitisinone provided by the embodiment of the present invention is a green and environmentally friendly synthesis process that is easy to industrialize.

[0022] At the same time, anhydrous potassium fluoride is required in the synthesis process of Nitisinone. This is because potassium fluoride itself is easily deliquescent and easily absorbs water in the air, resulting in changes in dosage. At the same time, the reaction raw material 2-nitro-4-trifluoromethylbenzoyl chloride is easily hydrolyzed. Therefore, anhydrous potassium fluoride is required in the reaction.

[0023] In an optional embodiment, the preparation of nitisinone comprises the following steps: dissolving 2-nitro-4-trifluoromethylbenzoyl chloride in an organic solvent to obtain a solution, and adding dropwise to a suspension formed by mixing 1,3-cyclohexanedione, anhydrous potassium fluoride and an organic solvent, so that 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione undergo a condensation reaction to obtain nitisinone.

[0024] In an optional embodiment, the molar ratio of 2-nitro-4-trifluoromethylbenzoyl chloride to anhydrous potassium fluoride is 1.0:1.0-6.0, preferably 1.0:2.0-5.0, and further preferably 1.0:3.5-5.0.

[0025] In an optional embodiment, the molar ratio of 2-nitro-4-trifluoromethylbenzoyl chloride to 1,3-cyclohexanedione is 1.0:1.0-1.5, preferably 1.0:1.0-1.2. It should be noted that reducing or increasing the above preferred material ratio will result in insufficient raw material conversion or increased by-products.

[0026] In an optional embodiment, the organic solvent is an aprotic organic solvent. Preferably, the aprotic organic solvent includes at least one of toluene, acetonitrile, dichloromethane, ethyl acetate, acetone, dioxane and tetrahydrofuran, and more preferably at least one of toluene, acetonitrile and ethyl acetate.

[0027] In an optional embodiment, the reaction temperature of the condensation reaction is -20-50°C, and the reaction time is not less than 3 hours. The preferred reaction temperature is -10-40°C, and the reaction time is 3-72 hours. The further preferred reaction temperature is 0-30°C, and the reaction time is 8-32 hours. It should be noted that shortening or extending the above preferred reaction time will result in insufficient raw material conversion or product degradation.

[0028] In an optional embodiment, 2-nitro-4-trifluoromethylbenzoyl chloride is prepared by the following steps:

[0029] In the presence of an aprotic organic solvent, using N,N-dimethylformamide as a catalyst, 2-nitro-4-trifluoromethylbenzoic acid and thionyl chloride undergo chlorination reaction to obtain 2-nitro-4-trifluoromethylbenzoyl chloride;

[0030] Preferably, the molar ratio of 2-nitro-4-trifluoromethylbenzoic acid to thionyl chloride is 1.0:1.1-3.0, preferably 1.0:1.1-2.0, and more preferably 1.0:1.3-1.8; the molar ratio of 2-nitro-4-trifluoromethylbenzoic acid to N,N-dimethylformamide is 1.0:0.01-0.1;

[0031] Preferably, the reaction temperature of the chlorination reaction is controlled to be 40-120°C, and the reaction time is 3-8h;

[0032] Preferably, the aprotic organic solvent includes at least one of ester, aromatic, ether and alkane organic solvents, preferably at least one of propyl acetate, ethyl acetate, toluene, benzene, xylene, dioxane, tetrahydrofuran, methyl tert-butyl ether, dichloromethane and chloroform, and more preferably at least one of ethyl acetate, toluene and dichloromethane.

[0033] In an optional embodiment, the method further comprises: after the condensation reaction is completed, the reaction mixture is washed, extracted, dried, filtered, and concentrated to obtain a crude product of nitisinone, and the crude product of nitisinone is then recrystallized and refined to obtain pharmaceutical-grade nitisinone.

[0034] In an optional embodiment, the solvent used for recrystallization purification is a mixed solvent of acetone and water, and the volume ratio of acetone to water is 1.0:0.5-3.0, preferably 1.0:0.6-2.4, and further preferably 1.0:0.8-1.5.

[0035] In an optional embodiment, the recrystallization refining temperature is 30-100°C, preferably 35-80°C, and more preferably 40-65°C.

[0036] In the embodiment of the present invention, the obtained crude nitisinone is recrystallized and purified using a mixture of acetone and water as a solvent, wherein a large amount of organic impurities remain in the acetone and inorganic impurities remain in the water. This purification process has a better effect than recrystallization using ethyl acetate as a solvent. The results of HPLC test show that the purity of the product is greatly improved, and a nitisinone raw material that meets the current quality standard requirements can be obtained.

[0037] As described above, the embodiment of the present invention provides a novel method for preparing nitisinone, comprising: in the presence of anhydrous potassium fluoride and an organic solvent, 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione are subjected to a condensation reaction to obtain nitisinone. The method avoids the use of extremely toxic cyaniding reagents, and the method of preparing nitisinone by using inorganic weak base potassium fluoride to participate in the reaction has good reaction selectivity, conversion rate, good purity and separation yield, and has the advantages of easy availability of raw materials, environmental friendliness, and atomic and process economy.

[0038] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0039] The present invention provides a new method for preparing nitisinone, firstly, 2-nitro-4-trifluoromethylbenzoic acid is used as a raw material to undergo a chlorination reaction with thionyl chloride to prepare 2-nitro-4-trifluoromethylbenzoyl chloride, and then the prepared 2-nitro-4-trifluoromethylbenzoyl chloride is subjected to a condensation reaction with 1,3-cyclohexanedione in the presence of anhydrous potassium fluoride without separation to obtain a crude nitisinone product, which is then purified by recrystallization to obtain a nitisinone raw material drug that meets the requirements of the current quality standards. The reaction equation is as follows:

[0040]

[0041] Example 1

[0042] Under nitrogen protection, 35 ml of dry toluene and catalytic amount of N,N-dimethylformamide (3 drops) were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. Under ice bath, 3.60 g of thionyl chloride solution dissolved in 20 ml of dry toluene was slowly added dropwise. After the addition was completed, the temperature was raised to 110°C and refluxed. After reacting for 4 hours, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After evaporation, the residual thionyl chloride was removed three times with 20 ml of toluene each time. After evaporation to dryness, colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of toluene was added to dissolve it for later use.

[0043] Under nitrogen protection, 2.52g of 1,3-cyclohexanedione, 5.2g of potassium fluoride powder dried to constant weight, and 100ml of dry toluene were stirred and mixed at 25°C, and then the above-mentioned toluene solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added to the suspension under ice bath. After the addition was completed, the temperature was raised to 25°C for reaction for 30h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (twice), 150ml of saturated sodium chloride solution and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered and concentrated to obtain 6.35g of crude nitisinone in a light yellow powder with an HPLC purity of 96.2%.

[0044] The crude product was recrystallized at 50°C with 200ml acetone / water (5:3, v / v), cooled to 5°C to precipitate solid, filtered, and the filter cake was washed with 20ml ice water. The filter cake was vacuum dried at 40°C (0.01MPa) to constant weight to obtain 4.4g of white needle-like solid, with a total molar yield of 66% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.9%, and the largest single impurity: 0.04%. Melting point: 140.1-141.5°C;

[0045] H NMR spectrum Figure 1 , 1 H NMR (400 MHz, CDCl 3): δ16.28(s,1H),8.50(s,1H),7.97(d,J=8.0Hz,1H),7.40(d,J=8.0Hz,1H),2.84(t,J=6.6Hz,2H),2.38(t,J=6.6Hz,2H),2.07(m,2H);

[0046] Carbon spectrum see Figure 2 , 13 C NMR (100 MHz, CDCl 3 ):δ196.34,195.75,194.13,145.67,139.73,132.31,131.95,130.76,127.70,121.18,112.67,37.34,31.89,19.13;TOF-HRMS(+ESI):measured value C 14 H 11 F 3 NO 5 [M+H] + 330.0593, theoretical value 330.0589.

[0047] Example 2

[0048] Under nitrogen protection, 40 ml of dry ethyl acetate and catalytic amount of N,N-dimethylformamide (3 drops) were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. 4.30 g of thionyl chloride was slowly added dropwise under ice bath. After the addition was completed, the temperature was raised to 70°C. After 8 hours of reaction, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After the solvent was evaporated, the residual thionyl chloride was removed three times with 20 ml of n-heptane each time. After evaporation to dryness, colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of acetonitrile was added to dissolve it for later use.

[0049] Under nitrogen protection, 2.77g of 1,3-cyclohexanedione, 4.50g of potassium fluoride powder dried to constant weight, and 100ml of dry acetonitrile were stirred and mixed at 25°C, and the above-mentioned acetonitrile solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added to the suspension at 10°C. After the addition was completed, the temperature was raised to 35°C for reaction for 12h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (twice), 150ml of saturated sodium chloride solution and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered and concentrated to obtain 6.14g of crude nitisinone in a light yellow powder with an HPLC purity of 95.5%.

[0050] The crude product was recrystallized at 55°C with 350ml acetone / water (1:1, v / v), cooled to 5°C to precipitate solid, filtered, and the filter cake was washed with 20ml ice water. The filter cake was vacuum dried at 40°C (0.01MPa) to constant weight to obtain 4.8g of white needle-shaped solid, with a total molar yield of 74% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.9%, and the largest single impurity: 0.02%. The characterization data of the target compound such as H NMR spectrum, C spectrum, and high-resolution mass spectrum can be found in Example 1.

[0051] Example 3

[0052] Under nitrogen protection, 40 ml of dry ethyl acetate and 0.10 g of N,N-dimethylformamide were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. 4.85 g of thionyl chloride was slowly added dropwise under ice bath. After the addition was completed, the temperature was raised to 80°C. After 6 hours of reaction, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After the solvent was evaporated, 20 ml of n-heptane was used to remove the remaining thionyl chloride three times. After evaporation to dryness, a colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of ethyl acetate was added to dissolve the solution for later use.

[0053] Under nitrogen protection, 2.33g of 1,3-cyclohexanedione, 5.00g of potassium fluoride powder dried to constant weight, and 80ml of dry ethyl acetate were stirred and mixed at 25°C, and the above-mentioned acetonitrile solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added to the suspension at -5°C. After the addition was completed, the temperature was raised to 40°C for reaction for 15h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (twice), 150ml of saturated sodium chloride solution and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered and concentrated to obtain 6.50g of crude nitisinone in a light yellow powder with an HPLC purity of 93.4%.

[0054] The crude product was recrystallized at 65°C with 250 ml of acetone / water (4:3, v / v), cooled to 5°C to precipitate solids, filtered, and the filter cake was washed with 20 ml of ice water. The filter cake was vacuum dried at 40°C (0.01 MPa) to constant weight to obtain 4.5 g of white needle-shaped solids, with a total molar yield of 68% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.8%, and the largest single impurity: 0.06%. The characterization data of the target compound such as H NMR spectrum, C spectrum, and high-resolution mass spectrum can be found in Example 1.

[0055] Example 4

[0056] Under nitrogen protection, 30 ml of dry dichloromethane and 0.05 g of N,N-dimethylformamide were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. 5.0 g of thionyl chloride was slowly added dropwise under ice bath. After the addition was completed, the temperature was raised to 40°C. After 12 hours of reaction, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After evaporation, the residual thionyl chloride was removed three times with 20 ml of n-heptane each time. After evaporation to dryness, a colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of dichloromethane was added to dissolve it for later use.

[0057] Under nitrogen protection, 2.46g of 1,3-cyclohexanedione, 4.80g of potassium fluoride powder dried to constant weight, and 120ml of dry dichloromethane were stirred at room temperature, and the dichloromethane solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added to the suspension at 3°C. After the addition was completed, the mixture was reacted at room temperature for 40h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (2 times), 150ml of saturated sodium chloride solution, and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered, and concentrated to obtain 6.08g of crude nitisinone in a light yellow powder with an HPLC purity of 95.4%.

[0058] The crude product was recrystallized at 50°C with 150ml acetone / water (2:1, v / v), cooled to 5°C to precipitate solid, filtered, and the filter cake was washed with 20ml ice water. The filter cake was vacuum dried at 40°C (0.01MPa) to constant weight to obtain 3.9g of white needle-shaped solid, with a total molar yield of 60% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.9%, and the largest single impurity: 0.03%. The characterization data of the target compound such as H NMR spectrum, C spectrum, and high-resolution mass spectrum can be found in Example 1.

[0059] Example 5

[0060] Under nitrogen protection, 40 ml of dry toluene and 0.05 g of N,N-dimethylformamide were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. 4.5 g of thionyl chloride was slowly added dropwise under ice bath. After the addition was completed, the temperature was raised to 90°C. After 16 hours of reaction, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After evaporation, the residual thionyl chloride was removed three times with 20 ml of n-heptane each time. After evaporation to dryness, a colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of acetonitrile was added to dissolve it for later use.

[0061] Under nitrogen protection, 2.88g of 1,3-cyclohexanedione, 3.5g of potassium fluoride powder dried to constant weight, and 100ml of dry acetonitrile were stirred and mixed at 25°C, and the above-mentioned acetonitrile solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added to the suspension at 10°C. After the addition was completed, the temperature was raised to 40°C for reaction for 9h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (twice), 150ml of saturated sodium chloride solution and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered and concentrated to obtain 6.27g of crude nitisinone in a light yellow powder with an HPLC purity of 96.9%.

[0062] The crude product was recrystallized at 60°C with 250ml acetone / water (2:1, v / v), cooled to 5°C to precipitate solid, filtered, and the filter cake was washed with 20ml ice water. The filter cake was vacuum dried at 40°C (0.01MPa) to constant weight to obtain 4.5g of white needle-shaped solid, with a total molar yield of 70% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.9%, and the largest single impurity: 0.02%. The characterization data of the target compound such as H NMR spectrum, C spectrum, and high-resolution mass spectrum can be found in Example 1.

[0063] Comparative Example 1

[0064] The steps were similar to those in Example 1, except that anhydrous potassium fluoride was replaced with anhydrous potassium carbonate (2.5 molar equivalents). The results were as follows.

[0065] Under nitrogen protection, 35 ml of dry toluene and catalytic amount of N,N-dimethylformamide (3 drops) were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. Under ice bath, 3.60 g of thionyl chloride solution dissolved in 20 ml of dry toluene was slowly added dropwise. After the addition was completed, the temperature was raised to 110°C and refluxed. After reacting for 4 hours, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After evaporation, the residual thionyl chloride was removed three times with 20 ml of toluene each time. After evaporation to dryness, colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of toluene was added to dissolve it for later use.

[0066] Under nitrogen protection, 2.52g of 1,3-cyclohexanedione, 6.50g of dried potassium carbonate powder, and 100ml of dried toluene were stirred and mixed at 25°C, and then the above-mentioned toluene solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added dropwise to the suspension in an ice bath. After the addition was completed, the temperature was raised to 25°C for reaction for 30h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (twice), 150ml of saturated sodium chloride solution, and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered, and concentrated to obtain 4.20g of yellow powdery crude nitisinone with an HPLC purity of 94.5%.

[0067] The crude product was recrystallized from 150 ml of acetone / water (5:3, v / v) at 50°C, cooled to 5°C to precipitate a solid, filtered, and the filter cake was washed with 20 ml of ice water. The filter cake was dried under vacuum (0.01 MPa) at 40°C to constant weight to obtain 2.6 g of a white needle-like solid with a total molar yield of 40% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.0%, and the largest single impurity: 0.11%.

[0068] Comparative Example 2

[0069] The steps are similar to those in Example 1, except that the amount of anhydrous potassium fluoride is reduced to 2.5 molar equivalents. The experiment is as follows.

[0070] Under nitrogen protection, 35 ml of dry toluene and catalytic amount of N,N-dimethylformamide (3 drops) were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. Under ice bath, 3.60 g of thionyl chloride solution dissolved in 20 ml of dry toluene was slowly added dropwise. After the addition was completed, the temperature was raised to 110°C and refluxed. After reacting for 4 hours, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After evaporation, the residual thionyl chloride was removed three times with 20 ml of toluene each time. After evaporation to dryness, colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of acetonitrile was added to dissolve it for later use.

[0071] Under nitrogen protection, 2.52g of 1,3-cyclohexanedione, 2.90g of potassium fluoride powder dried to constant weight, and 100ml of dry acetonitrile were stirred and mixed at 25°C, and then the above-mentioned acetonitrile solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added dropwise to the suspension in an ice bath. After the addition was completed, the temperature was raised to 25°C for reaction for 32h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (twice), 150ml of saturated sodium chloride solution and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered and concentrated to obtain 3.75g of crude nitisinone in a light yellow powder with an HPLC purity of 93.5%.

[0072] The crude product was recrystallized from 180 ml of acetone / water (4:3, v / v) at 50°C, cooled to 5°C to precipitate a solid, filtered, and the filter cake was washed with 20 ml of ice water. The filter cake was dried under vacuum (0.01 MPa) at 40°C to constant weight to obtain 2.2 g of a white needle-like solid with a total molar yield of 33% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.1%, and the largest single impurity: 0.15%.

[0073] Comparative Example 3

[0074] The steps were similar to those in Example 1, except that the raw material ratio of the condensation reaction was increased to 1.3 molar equivalents of 1,3-cyclohexanedione. The results were as follows.

[0075] Under nitrogen protection, 35 ml of dry toluene and catalytic amount of N,N-dimethylformamide (3 drops) were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. Under ice bath, 3.60 g of thionyl chloride solution dissolved in 20 ml of dry toluene was slowly added dropwise. After the addition was completed, the temperature was raised to 110°C and refluxed. After reacting for 4 hours, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After evaporation, the residual thionyl chloride was removed three times with 20 ml of toluene each time. After evaporation to dryness, colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of toluene was added to dissolve it for later use.

[0076] Under nitrogen protection, 2.92g of 1,3-cyclohexanedione, 5.2g of potassium fluoride powder dried to constant weight, and 100ml of dry toluene were stirred and mixed at 25°C, and then the above-mentioned toluene solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added to the suspension under ice bath. After the addition was completed, the temperature was raised to 25°C for reaction for 30h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (twice), 150ml of saturated sodium chloride solution and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered and concentrated to obtain 6.44g of crude nitisinone in a light yellow powder with an HPLC purity of 95.0%.

[0077] The crude product was recrystallized from 200 ml of acetone / water (5:3, v / v) at 50°C, cooled to 5°C to precipitate a solid, filtered, and the filter cake was washed with 20 ml of ice water. The filter cake was dried under vacuum (0.01 MPa) at 40°C to constant weight to obtain 4.3 g of a white needle-like solid with a total molar yield of 64% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.5%, and the largest single impurity: 0.10%.

[0078] Comparative Example 4

[0079] The steps were similar to those in Example 1, except that the condensation reaction temperature was increased to 45°C. The results were as follows.

[0080] Under nitrogen protection, 35 ml of dry toluene and catalytic amount of N,N-dimethylformamide (3 drops) were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. Under ice bath, 3.60 g of thionyl chloride solution dissolved in 20 ml of dry toluene was slowly added dropwise. After the addition was completed, the temperature was raised to 110°C and refluxed. After reacting for 4 hours, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After evaporation, the residual thionyl chloride was removed three times with 20 ml of toluene each time. After evaporation to dryness, colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of toluene was added to dissolve it for later use.

[0081] Under nitrogen protection, 2.52g of 1,3-cyclohexanedione, 5.2g of potassium fluoride powder dried to constant weight, and 100ml of dry toluene were stirred and mixed at 25°C, and then the above-mentioned toluene solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added to the suspension at 10°C. After the addition was completed, the temperature was raised to 45°C for reaction for 8h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (2 times), 150ml of saturated sodium chloride solution and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered and concentrated to obtain 6.10g of crude nitisinone in a light yellow powder with an HPLC purity of 90.8%.

[0082] The crude product was recrystallized with 220 ml of acetone / water (2:1, v / v) at 50°C, and the solid was precipitated by cooling to 5°C. The solid was filtered and the filter cake was washed with 20 ml of ice water. The filter cake was dried under vacuum (0.01 MPa) at 40°C to constant weight to obtain 3.3 g of white needle-like solid. The total molar yield was 50% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 98.7%, and the largest single impurity: 0.21%.

[0083] Comparative Example 5

[0084] The steps are similar to those in Example 1, except that the amount of anhydrous potassium fluoride is increased to 6.5 molar equivalents. The experiment is as follows.

[0085] Under nitrogen protection, 35 ml of dry toluene and catalytic amount of N,N-dimethylformamide (3 drops) were used to dissolve 4.70 g of 2-nitro-4-trifluoromethylbenzoic acid at room temperature. Under ice bath, 3.60 g of thionyl chloride solution dissolved in 20 ml of dry toluene was slowly added dropwise. After the addition was completed, the temperature was raised to 110°C and refluxed. After reacting for 4 hours, the temperature was lowered to room temperature. The solvent was evaporated under reduced pressure. After evaporation, the residual thionyl chloride was removed three times with 20 ml of toluene each time. After evaporation to dryness, colorless oily 2-nitro-4-trifluoromethylbenzoyl chloride was obtained. 50 ml of toluene was added to dissolve it for later use.

[0086] Under nitrogen protection, 2.52g of 1,3-cyclohexanedione, 7.60g of potassium fluoride powder dried to constant weight, and 100ml of dry toluene were stirred and mixed at 25°C, and then the above-mentioned toluene solution of 2-nitro-4-trifluoromethylbenzoyl chloride was slowly added dropwise to the suspension in an ice bath. After the addition was completed, the temperature was raised to 25°C for reaction for 30h. After the reaction was completed, 100ml of 10% sodium chloride solution was added to the reaction mixture, and the liquid was separated. After discarding the aqueous phase, the organic phase was washed with 150ml of 2mol / L hydrochloric acid (twice), 150ml of saturated sodium chloride solution and 50ml of purified water in sequence, dried over anhydrous sodium sulfate, filtered and concentrated to obtain 6.04g of crude nitisinone in a light yellow powder with an HPLC purity of 95.0%.

[0087] The crude product was recrystallized with 180 ml of acetone / water (2:1, v / v) at 50°C, and the solid was precipitated by cooling to 5°C. The solid was filtered and the filter cake was washed with 20 ml of ice water. The filter cake was dried under vacuum (0.01 MPa) at 40°C to constant weight to obtain 3.31 g of white needle-like solid. The total molar yield was 50% (based on 2-nitro-4-trifluoromethylbenzoic acid), HPLC purity: 99.4%, and the largest single impurity: 0.10%.

[0088] In summary, the embodiment of the present invention provides a method for preparing nitisinone, comprising: in the presence of anhydrous potassium fluoride, 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione undergo a condensation reaction in an organic solvent to obtain nitisinone. The method for preparing nitisinone provided by the embodiment of the present invention avoids the use of highly toxic and highly polluting reagents containing cyano groups, and in the presence of potassium fluoride, the selectivity of the condensation reaction is improved. The crude nitisinone obtained by the reaction is then recrystallized and refined using a mixed solvent of acetone and water to obtain pharmaceutical-grade nitisinone. The method for preparing pharmaceutical-grade nitisinone provided by the embodiment of the present invention provides a basis for its wide application.

[0089] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing nitisinone, characterized in that: In the presence of anhydrous potassium fluoride, 2-nitro-4-trifluoromethylbenzoyl chloride and 1,3-cyclohexanedione undergo a condensation reaction in an organic solvent to obtain nitisinone, wherein: The molar ratio of the 2-nitro-4-trifluoromethylbenzoyl chloride to the anhydrous potassium fluoride is 1.0:1.0-6.0; The molar ratio of the 2-nitro-4-trifluoromethylbenzoyl chloride to the 1,3-cyclohexanedione is 1.0:1.0-1.5; The reaction temperature of the condensation reaction is -20-50°C, and the reaction time is not less than 3h.

2. The preparation method according to claim 1, characterized in that: The method comprises the following steps: dissolving the 2-nitro-4-trifluoromethylbenzoyl chloride in the organic solvent to obtain a solution, and adding dropwise the solution into a suspension formed by mixing the 1,3-cyclohexanedione, the anhydrous potassium fluoride and the organic solvent, so that the 2-nitro-4-trifluoromethylbenzoyl chloride and the 1,3-cyclohexanedione undergo a condensation reaction to obtain nitisinone.

3. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the 2-nitro-4-trifluoromethylbenzoyl chloride to the anhydrous potassium fluoride is 1.0:2.0-5.

0.

4. The preparation method according to claim 3, characterized in that: The molar ratio of the feeding amount of the 2-nitro-4-trifluoromethylbenzoyl chloride to the anhydrous potassium fluoride is 1.0:3.5-5.

0.

5. The preparation method according to claim 1 or 2, characterized in that: The molar ratio of the feeding amount of the 2-nitro-4-trifluoromethylbenzoyl chloride to the 1,3-cyclohexanedione is 1.0:1.0-1.

2.

6. The preparation method according to claim 1 or 2, characterized in that: The organic solvent is an aprotic organic solvent.

7. The preparation method according to claim 6, characterized in that: The aprotic organic solvent includes at least one of toluene, acetonitrile, dichloromethane, ethyl acetate, acetone, dioxane and tetrahydrofuran.

8. The preparation method according to claim 7, characterized in that: The aprotic organic solvent is at least one of toluene, acetonitrile and ethyl acetate.

9. The preparation method according to claim 1 or 2, characterized in that: The reaction temperature of the condensation reaction is -10-40°C and the reaction time is 3-72h.

10. The preparation method according to claim 9, characterized in that: The reaction temperature of the condensation reaction is 0-30°C and the reaction time is 8-32h.

11. The preparation method according to claim 1 or 2, characterized in that: The 2-nitro-4-trifluoromethylbenzoyl chloride is prepared by the following steps: In the presence of a non-protonic organic solvent, N,N-dimethylformamide is used as a catalyst to cause chlorination reaction between 2-nitro-4-trifluoromethylbenzoic acid and thionyl chloride to obtain the 2-nitro-4-trifluoromethylbenzoyl chloride.

12. The preparation method according to claim 11, characterized in that: The molar ratio of the feeding amount of the 2-nitro-4-trifluoromethylbenzoic acid to the thionyl chloride is 1.0:1.1-3.0; the molar ratio of the feeding amount of the 2-nitro-4-trifluoromethylbenzoic acid to the N,N-dimethylformamide is 1.0:0.01-0.

1.

13. The preparation method according to claim 12, characterized in that: The molar ratio of the feeding amount of the 2-nitro-4-trifluoromethylbenzoic acid to the thionyl chloride is 1.0:1.1-2.

0.

14. The preparation method according to claim 13, characterized in that: The molar ratio of the feeding amount of the 2-nitro-4-trifluoromethylbenzoic acid to the thionyl chloride is 1.0:1.3-1.

8.

15. The preparation method according to claim 11, characterized in that: The reaction temperature of the chlorination reaction is controlled to be 40-120°C and the reaction time is 3-8h.

16. The preparation method according to claim 11, characterized in that: The aprotic organic solvent includes at least one of ester, aromatic, ether and alkane organic solvents.

17. The preparation method according to claim 16, characterized in that: The aprotic organic solvent is at least one of propyl acetate, ethyl acetate, toluene, benzene, xylene, dioxane, tetrahydrofuran, methyl tert-butyl ether, dichloromethane and chloroform.

18. The preparation method according to claim 17, characterized in that: The aprotic organic solvent is at least one of ethyl acetate, toluene and dichloromethane.

19. The preparation method according to claim 1 or 2, characterized in that: Also includes: After the condensation reaction is completed, the reaction mixture is washed, extracted, dried, filtered and concentrated to obtain a crude product of nitisinone, and then the crude product of nitisinone is recrystallized and refined to obtain pharmaceutical grade nitisinone.

20. The preparation method according to claim 19, characterized in that: The solvent used for recrystallization purification is a mixed solvent of acetone and water, and the volume ratio of acetone to water is 1.0:0.5-3.

0.

21. The preparation method according to claim 20, characterized in that: The solvent used for recrystallization purification is a mixed solvent of acetone and water, and the volume ratio of acetone to water is 1.0:0.6-2.

4.

22. The preparation method according to claim 21, characterized in that: The solvent used for recrystallization purification is a mixed solvent of acetone and water, and the volume ratio of acetone to water is 1.0:0.8-1.

5.

23. The preparation method according to claim 19, characterized in that: The temperature of recrystallization refining is 30-100℃.

24. The preparation method according to claim 23, characterized in that: The temperature of recrystallization refining is 35-80℃.

25. The preparation method according to claim 24, characterized in that: The temperature of recrystallization refining is 40-65℃.

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