Preparation method of tecovirimat and intermediate thereof

Abstract

The invention discloses a preparation method of tecovirimat and an intermediate thereof. The preparation method of the tecovirimat comprises the following steps: (i) cyclohexene 1 and chloroform react under the action of a catalyst M and an aqueous alkali solution to generate a compound 2; (ii) carrying out pyrolytic reaction on the compound 2 in a solvent A to generate cycloheptatriene 3; (iii) carrying out reaction on cycloheptatriene 3 and a compound 4 in a solvent B to obtain a compound 5; and (iv) carrying out amine condensation reaction on the compound 5 and a compound 6 in the presence of a solvent C to obtain tecovirimat. According to the preparation method, potential safety hazards caused by high-temperature reaction are avoided, side reactions are reduced, the yield and the product quality are improved, the process is stable, and the preparation method is suitable for large-scale production. # imgabs0 #

Description

[0001] This application claims priority to Chinese patent application No. 202310778601.4, filed on June 28, 2023, and entitled “A method for preparing tecovir”, the entire contents of which are incorporated herein by reference in their entirety. Technical Field

[0002] The present invention relates to the field of medical technology, in particular to a preparation method of tecovir and an intermediate thereof. Background Art

[0003] Tecovirimat, chemically named REL-N-[(3AR, 4R, 4AR, 5AS, 6S, 6AS)-3, 3A, 4, 4A, 5, 5A, 6, 6A-octahydro-1, 3-dioxo-4, 6-ethynylcyclopropyl[F]isoindol-2(1H)-yl]-4-(trifluoromethyl)benzamide, is the first oral antiviral drug approved by the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA) for the treatment of monkeypox disease. This antiviral drug acts as an active orthopoxvirus inhibitor with excellent oral bioavailability, which can prevent the spread of the virus in the body.

[0004] SIGA Technologies reported a synthetic route I of tecoviridad as shown below (Hughes DL. Review of the Patent Literature: Synthesis and Final Forms of Anti-viral Drugs Tecovirimat and Baloxavir Marboxil [J]. Organic Process Research & Development, 2019, 23 (7).), i.e., cycloheptatriene 3 and maleic anhydride 4 undergo a Diels-Alder reaction in refluxing xylene (138-144° C.) to obtain a cycloadduct 5 and a mixture of its isomers; the intermediate 4-(trifluoromethyl)benzohydrazine 6 is obtained by reacting anhydrous hydrazine or hydrazine hydrate with methyl 4-trifluoromethylbenzoate 7 in toluene reflux, and then recrystallized from t-butyl methyl ether; subsequently, the intermediate anhydride 5 is condensed with the intermediate 6 in the reflux of anhydrous ethanol to obtain tecoviridad.

[0005] Reaction Scheme I:

[0006]

[0007] Among the reported methods for synthesizing cycloheptatriene 3, the most effective method described is the pyrolysis of compound 2. The method in the literature (Winberg, W., Synthesis of Cycloheptatriene, The Journal of Organic Chemistry, 1959, 24 (2), 264-265.) involves preparing compound 2 from dichlorocarbene and cyclohexene with a yield of 59%, and then pyrolyzing the product to obtain a mixture containing 35% cycloheptatriene 3 and 65% toluene. However, the pyrolysis reaction is carried out at 490-520° C., the reaction selectivity is poor, there are many by-products, and the yield is low.

[0008] Summary of the invention

[0009] Based on the problems existing in the above-mentioned prior art, the present invention proposes an improved process route for synthesizing cycloheptatriene and tecovirizumab, comprising: a) breaking through the key technical problems of synthesizing cycloheptatriene, reducing the reaction temperature, and avoiding the safety hazards caused by the thermal cracking high-temperature reaction of synthesizing cycloheptatriene from the source; b) selecting suitable reaction and refining solvents to reduce the temperature of the Diels-Alder reaction, so that the reaction selectivity and the quality of the product are significantly improved, and at the same time, the post-processing operations of each step are simplified, so that the reaction process is suitable for large-scale production and the process is stable.

[0010] In view of this, the present invention adopts the following technical solution:

[0011] The first aspect of the present invention provides a method for preparing cycloheptatriene, the preparation method comprising:

[0012]

[0013] (i) Cyclohexene 1 reacts with chloroform in the presence of a catalyst M and an aqueous alkali solution to produce compound 2;

[0014] (ii) Compound 2 undergoes a thermal decomposition reaction in solvent A to generate cycloheptatriene 3; the solvent A is one or more selected from 2-pyrrolidone, polyethylene glycol dimethyl ether, N,N-dimethylacetamide, and N-methylpyrrolidone; and the temperature of the thermal decomposition reaction is 160 to 200°C.

[0015] In some embodiments, in step (i), the catalyst M is one or more combinations selected from benzyltriethylammonium chloride (PTC), tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, 18 crown 6, and cyclodextrin, preferably benzyltriethylammonium chloride (PTC).

[0016] In some embodiments, in step (i), the molar ratio of cyclohexene 1 to catalyst M is 1:0.01-0.10, preferably 1:0.04-0.10, for example 1:0.05.

[0017] In some embodiments, in step (i), the alkali in the aqueous alkali solution is one or more combinations selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate and lithium carbonate, preferably sodium hydroxide. In some embodiments, the mass fraction of the aqueous alkali solution is 30%-65%; preferably 40-60%, for example 50%.

[0018] In some embodiments, in step (i), the molar ratio of cyclohexene 1 to the base is 1:1-10, preferably 1:1-5.

[0019] In some embodiments, in the reaction of step (i), the molar ratio of cyclohexene 1 to chloroform is 1:0.8-1.2, preferably 1:0.9-1.1, for example 1:1.

[0020] In some embodiments, in the reaction of step (i), the reaction temperature is 40-70°C, and the reaction time is 4-10 hours; preferably, the reaction temperature is 50-60°C, and the reaction time is 5-7 hours.

[0021] In some embodiments, the reaction in step (i) can be carried out by the following specific steps: heating a mixture of cyclohexene 1, catalyst M and chloroform to 45-50°C for reaction for 10-60 minutes, for example, 20 minutes, and dropping the above-mentioned aqueous alkali solution under vigorous stirring, and intermittently adjusting the reaction temperature at 40-70°C, preferably 50-60°C for 0.5-3 hours, for example, 1.5 hours, and then continuing to keep warm and stir the reaction for 3-10 hours, for example, 6 hours.

[0022] In some embodiments, after the reaction in step (i), a post-treatment step may be further included, wherein the post-treatment step is:

[0023] After the reaction solution is cooled to room temperature, it is diluted with water, the organic phase is separated, and concentrated to obtain a crude product, which is directly used for the reaction in step (ii); or

[0024] After the reaction solution is cooled to room temperature, it is diluted with water, the organic phase is separated and concentrated to obtain a crude product; the crude product is distilled at a pressure of -0.10 to 0.08 MPa, for example, -0.09 MPa, and a fraction of 60 to 90° C. is collected to obtain compound 2; alternatively, the crude product is subjected to reduced pressure distillation at a pressure of 2 to 5 kPa, for example, 3 kPa, and a fraction of 100 to 110° C. is collected to obtain compound 2.

[0025] In some embodiments, in step (ii), the solvent A is one or more selected from 2-pyrrolidone, polyethylene glycol dimethyl ether (PEGDME), N,N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP); preferably 2-pyrrolidone.

[0026] In some embodiments, in step (ii), the mass ratio of compound 2 to solvent A is 1:1-10, preferably 1:2-4, for example 1:3.

[0027] In some embodiments, in step (ii), the temperature of the pyrolysis reaction is 160-200°C, the reaction pressure is 50-200 kPa, and the reaction time is 2-6 h; preferably, the reaction temperature is 170-180°C, the reaction pressure is 80-120 kPa, for example 90 kPa, and the reaction time is 2-4 h.

[0028] In some embodiments, after the pyrolysis reaction in step (ii), a separation and purification step is further included, and the separation and purification step includes: collecting a fraction of 70 to 100°C from the reaction product under a pressure of 80 to 120 kPa to obtain a crude product, removing the aqueous phase from the crude product, and washing the organic phase to obtain a purified product, namely cycloheptatriene 3. In some embodiments, a saturated sodium bicarbonate aqueous solution is used to wash the organic phase. In some embodiments, after washing the organic phase, a vacuum distillation step is further included, and the vacuum distillation is to collect a fraction of 20 to 30°C under a pressure of 2 to 10 kPa;

[0029] In some embodiments, after the separation and purification step, the content of by-product toluene in the product is less than 10%.

[0030] The second aspect of the present invention provides a method for preparing Tecovir, the preparation method comprising:

[0031]

[0032] (i) Cyclohexene 1 reacts with chloroform in the presence of a catalyst M and an aqueous alkali solution to produce compound 2;

[0033] (ii) Compound 2 undergoes thermal decomposition in solvent A to generate cycloheptatriene 3;

[0034] (iii) cycloheptatriene 3 reacts with compound 4 in solvent B to obtain compound 5;

[0035] (iv) Compound 5 and Compound 6 undergo an amine condensation reaction in the presence of solvent C to obtain Tecovirizumab.

[0036] In the above-mentioned method for preparing tecovir, in steps (i)-(ii), the catalyst M, the aqueous alkaline solution, the solvent A, the amounts of the reactants, and the reaction conditions are the same as those described in the above-mentioned method for preparing cycloheptatriene.

[0037] In some embodiments, in step (iii), the molar ratio of compound 4 to cycloheptatriene 3 is 1-1.2:1, preferably 1-1.1:1, such as 1.05:1.

[0038] In some embodiments, in step (iii), the solvent B is selected from one or more of dioxane, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, toluene, xylene, chlorobenzene, acetonitrile, acetone, ethanol, isopropanol, n-butanol, tert-butanol, tert-amyl alcohol, ethylene glycol, pyridine, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and water. When toluene is used as the solvent, the heating temperature is about 108°C, which reduces the reaction temperature compared to xylene (140°C), improves the overall efficiency of the reaction and the selectivity and quality of the target product, and improves the yield and purity of compound 5.

[0039] In some embodiments, in step (iii), the mass ratio of compound 3 to solvent B is 1:1-30, preferably 1:5-15, for example 1:10.

[0040] In some embodiments, in step (iii), the reaction temperature is 80-130° C., preferably 105-120° C., and the reaction time is 1-5 h, preferably 2-4 h, for example 3 h. Preferably, step (iii) is refluxed in toluene.

[0041] In some embodiments, in step (iii), the isomers in the reaction product The content of isomers is less than 10%; preferably, the content of isomers is 5-8%.

[0042] In some embodiments, in step (iii), after the reaction is completed, a purification step is further included, and the purification step includes: adding methyl tert-butyl ether (MTBE) to the cooled reaction solution, separating the precipitate and drying it, and then recrystallizing it with a methyl tert-butyl ether (MTBE)-ethanol mixed solvent to obtain a purified product, namely compound 5. In some embodiments, the volume ratio of the added amount of methyl tert-butyl ether (MTBE) to the reaction solution is 1:1-20, preferably 1:2-5, for example 1:3-4. In some embodiments, in the methyl tert-butyl ether (MTBE)-ethanol mixed solvent, the volume ratio of methyl tert-butyl ether (MTBE) to ethanol is 8-12:1, preferably 10:1. In the product of the above purification step, the isomers The content is less than 0.03%.

[0043] In some embodiments, in step (iv), the amine condensation reaction is carried out under the catalysis of a catalyst, and the catalyst is selected from an organic base, such as one or more of triethylamine, N, N-diisopropylethylamine (DIEA), pyridine, morpholin or N'N-dimethyl-4-aminopyridine, preferably N, N-diisopropylethylamine (DIEA). The introduction of the catalyst shortens the reaction time and increases the yield of the target product. In some embodiments, the molar ratio of compound 5 to the amount of catalyst is 1:0.01-1.0, preferably 1:0.01-0.10, more preferably 1:0.03-0.05, for example 1:0.04.

[0044] In some embodiments, in step (iv), the molar ratio of compound 5 to compound 6 is 0.8:1 to 1.2, preferably 0.9:1 to 1.1, for example 0.9:1 to 1.05.

[0045] In some embodiments, in step (iv), the solvent C is one or more selected from methanol, ethanol, isopropanol, n-butanol or tert-butanol; preferably ethanol.

[0046] In some embodiments, in step (iv), the mass ratio of compound 5 to solvent C is 1:5-20, preferably 1:6-10, for example 1:8.

[0047] In some embodiments, in step (iv), the amine condensation reaction is carried out under reflux in solvent C for 2 to 6 hours, preferably 3 to 5 hours, such as 4 hours.

[0048] In some embodiments, in step (iv), after the amine condensation reaction, a purification step is further included, and the purification step includes: adding water to the reaction solution for crystallization, cooling, filtering and separating the solid and drying, and then recrystallizing from a solvent C-water mixed solution to obtain Tecovir. In some embodiments, the volume ratio of the amount of water added to the reaction solution is 1:3-8, preferably 1:4-6, for example 1:5. In some embodiments, the volume ratio of solvent C to water in the solvent C-water mixed solution is 1:3-8, preferably 1:4-6, for example 1:5.

[0049] In some embodiments, compound 7 can be obtained by the following method:

[0050]

[0051] (v) Compound 7 is reacted with anhydrous hydrazine or hydrazine hydrate in a methanol-water mixed solution under reflux to obtain Compound 6.

[0052] In some embodiments, in step (v), the molar ratio of compound 7 to anhydrous hydrazine or hydrazine hydrate (calculated as hydrazine) is 1:1-2, preferably 1:1.3-1.7, for example 1:1.5. In some embodiments, hydrazine hydrate is used, for example 80% hydrazine hydrate.

[0053] In some embodiments, in step (v), the ratio of methanol to water in the methanol-water mixed solution is 1:6-10, for example 1:8. In some embodiments, the mass ratio of compound 6 to the methanol-water mixed solution is 1:3-7, preferably 1:4-6.

[0054] In some embodiments, in step (v), the reflux reaction time is 2 to 8 hours, preferably 3 to 5 hours, for example 4 hours.

[0055] In some embodiments, the reaction of step (v) can be carried out by the following specific steps: Compound 7 and hydrazine hydrate are stirred at 65-70° C. for 0.5-3 h, for example, 1 h, and then the above-mentioned methanol-water mixed solution is added dropwise, and the mixture is refluxed for reaction for 3-5 hours.

[0056] In some embodiments, step (v) further includes a separation and purification step after the reaction, and the separation and purification step includes: diluting the reaction solution with water, filtering, and drying the precipitate to obtain a crude product, slurrying the crude product with 2 to 6 times, for example, 4 times the mass of the crude product, and recrystallizing with 2 to 5 times, for example, 3 times the mass of methyl tert-butyl ether (MTBE) to obtain compound 6. DETAILED DESCRIPTION

[0057] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0058] Unless otherwise specified, all reagents and solvents were purchased from commercial suppliers and used without further purification. The residual signal of deuterated solvent (DMSO-d6) was used as the internal standard and was obtained on a Brucker 400-Hz instrument. 1 H NMR and 13 C NMR. 1 H and 13The chemical shift (δ) of C is given in parts per million (ppm) and the coupling constants are reported in Hz. Multiplicities are expressed as singlet (s), doublet (d), triplet (t), quartet (q), double doublet (dd), multit (m), etc. Electrospray ionization (ESI) mass spectra were measured using a Thermo Fisher FINNIGAN LTQ instrument. For thin layer chromatography (TLC) analysis, pre-coated plates (silica gel 60GF-254, 0.25 mm) were used and UV lamps were used as developer (254 nm). Organic solutions were concentrated under reduced pressure on a Heidolph rotary evaporator. GC samples were analyzed on an Agilent Technologies 6890GS system using an HP-5 column. Liquid HPLC analysis was performed on an Agilent HPLC workstation equipped with a Waters Xbridge-C18 (4.6×75 mm, 2.5 μm).

[0059] The following is the synthetic route of Tecovir of the present invention:

[0060]

[0061] (1) Cyclohexene 1 reacts with chloroform in the presence of a catalyst M and an alkaline aqueous solution to produce compound 2;

[0062] (2) Compound 2 undergoes thermal decomposition in solvent A (e.g., 2-pyrrolidone) to generate cycloheptatriene 3;

[0063] (3) Cycloheptatriene 3 reacts with compound 4 in solvent B (such as toluene) to obtain compound 5.

[0064] (4) Compound 7 is reacted with anhydrous hydrazine or hydrazine hydrate in a methanol-water mixed solution under reflux to obtain compound 6.

[0065] (5) Compound 5 and compound 6 undergo an amine condensation reaction in the presence of solvent C (such as ethanol) to obtain tecovir.

[0066] Example 1

[0067] (1) Synthesis of Compound 2:

[0068]

[0069] This step was performed on a 1.8 kg batch scale.

[0070] A mixture of compound 1 (1.8 kg, 22 mol, 1 eq), a water-soluble phase transfer catalyst benzyltriethylammonium chloride (PTC, 250 g, 1.1 mol, 0.05 eq) and chloroform (4 V, 7.2 L) was heated to 45-50 ° C for reaction for 20 min, and a 50% (w / w) aqueous solution of sodium hydroxide (4.4 kg, 110 mol, 5 eq) was added dropwise under vigorous stirring. The reaction was an exothermic reaction, and the reaction temperature was intermittently adjusted at 50-60 ° C for 1.5 h, and then stirred at 50-60 ° C for another 6 h. After cooling to room temperature, it was diluted with water (9 L), and the organic phase was separated. The organic phase was concentrated in vacuo at 40-50 ° C to obtain a crude product. The crude product was subjected to vacuum distillation (3 kPa) under a water pump, and the 100-110 ° C fraction was collected to obtain 2.3 kg of compound 2, with a yield of 74%, and a purity of 99.32% determined by GC.

[0071] (2) Synthesis of cycloheptatriene 3:

[0072]

[0073] Using 2-pyrrolidone as solvent, compound 2 (2.2 kg, 13.5 mol, 1 eq) and 2-pyrrolidone (4.9 kg, 2V) were added to a reactor connected to a distillation device. The reaction mixture was heated to 170-180°C for 4 hours, and the 80-100°C fraction was collected under a pressure of 100 kPa to obtain a crude product. After removing the aqueous phase from the crude product, the organic phase was washed with a saturated sodium bicarbonate aqueous solution, and then vacuum distilled under a water pump, and the 20-30°C fraction was collected under 3-4 kPa to obtain 823 g of cycloheptatriene 3, with a purity of 91.38% and containing 8% toluene.

[0074] (3) Synthesis of Compound 5:

[0075]

[0076] WO2004 / 112718A3 Example 1 In this step, xylene is used as solvent and the reaction is refluxed overnight. The yield of compound 5 is 28%, and the isomer impurity content in the product is less than 20%.

[0077] The present invention uses cycloheptatriene 3 containing toluene prepared and purified in the above step as a raw material, and uses toluene (6 kg) instead of xylene as a reaction solvent to prepare compound 5 through reaction. Specifically, cycloheptatriene 3 (747 g, 8.1 mol, 1.0 eq) and compound 4 (835 g, 8.5 mol, 1.05 eq) are refluxed at 120° C. for 3 h to obtain a reaction solution containing intermediate 5 and isomers in the above formula. After the reaction solution is cooled, MTBE (3.2 L, 4 V) is added, and the precipitated solid is filtered and dried, and MTBE: ethanol (10: 1, v / v) is used as a solvent for recrystallization to obtain a crystalline solid intermediate 5 with a yield of 82% and a purity of 99.83%. After purification, the content of the above isomers is reduced from 10% to <0.05%.

[0078] (4) Synthesis of Compound 6:

[0079]

[0080] Compound 7 (3.5 kg, 17.1 mol, 1.0 eq) and 80% hydrazine hydrate (1.6 kg, 25.7 mol, 1.5 eq) were added to the reactor, stirred at 65-70°C for 1 hour, and after the reaction was completed, methanol (1.5 kg, 0.5 v) was added, slowly added dropwise to (14 kg, 4 V) purified water, filtered and dried to obtain crude compound 6, crude compound 6 was slurried with 4 V water, and then recrystallized with 3 V MTBE to obtain a white solid, which was separated by high performance liquid chromatography (HPLC) with a yield of 77% and a purity of 99.92%. The above purification process successfully removed hydrazine hydrate from the final product.

[0081] (5) Synthesis of Tecoviride (N-[(3aR, 4R, 4aR, 5aS, 6S, 6aS)-3,3a,4,4a,5,5a,6,6a-octahydro-1,3-dioxo-4,6-vinylidenecyclopropane[f]isoindol-2(1H)-yl]-4-(trifluoromethyl)benzamide):

[0082]

[0083] In Example 1 of WO2004 / 112718A3, the condensation reaction of compounds 5 and 6 was carried out in EtOH reflux, and the reaction product was purified by silica gel column chromatography using hexane / ethyl acetate (1:1, v / v). The yield of compound 1 was 51%.

[0084] In the present invention, the step of synthesizing Tecovir is to reflux with EtOH for 4 hours in the presence of catalyst DIEA (0.04eq), so that compound 5 and equimolar amount of hydrazine compound 6 undergo amine condensation to convert into Tecovir. The specific steps are: add compound 5 (631g, 3.32mol, 1.05eq), compound 6 (645g, 3.16mol, 1.0eq) and DIEA (25g, 0.04eq), ethanol (6.5L, 10v) into the reactor, heat and reflux for 4h, and the reaction is completed. In order to obtain the ideal product with high yield, different crystallization solvents and dosages are tried. Among them, 1 / 5 volume of water of the reaction solution is added to the reaction solution for crystallization, and the obtained suspension is cooled, filtered, and dried at 50°C to obtain a crude product, which is then recrystallized by ethanol: water (5: 1v / v), and dried to obtain 99.95% purity (by HPLC) of Tecovir in the form of crystals, and a separation yield of 96% is obtained.

[0085] Example 2

[0086] One-pot preparation of compound 3

[0087] A mixture of compound 1 (1.8 kg, 22 mol, 1 eq), a water-soluble phase transfer catalyst benzyltriethylammonium chloride (PTC, 250 g, 1.1 mol, 0.05 eq) and chloroform (4 V, 7.2 L) was heated to 45-50 ° C for 20 min, and a 50% (w / w) aqueous solution of sodium hydroxide (4.4 kg, 110 mol, 5 eq) was added dropwise under vigorous stirring. The reaction temperature was intermittently adjusted at 50-60 ° C for 1.5 h, and then stirred at 50-60 ° C for another 6 h. After cooling to room temperature, it was diluted with water (9 L), the organic phase was separated, and the organic phase was concentrated in vacuo at 40-50 ° C to obtain a crude product 2.

[0088] Using 2-pyrrolidone as solvent, the crude product 2 obtained in the previous step and 2-pyrrolidone (4.9 kg, 2.5 V) were added to a reactor connected to a distillation device. The reaction mixture was heated to 170-180°C for 4 hours, and the 80-100°C fraction was collected under a pressure of 100 kPa to obtain a crude product. After removing the aqueous phase from the crude product, the organic phase was washed with a saturated sodium bicarbonate aqueous solution, and then vacuum distilled under a water pump, and the 20-30°C fraction was collected under 3-4 kPa to obtain 914 g of cycloheptatriene 3 with a purity of 91.81%.

[0089] Example 3

[0090] This example is an expanded production on the scale of Example 1.

[0091] (1) Synthesis of Compound 2

[0092] A mixture of compound 1 (30 kg, 365.20 mol, 1 eq), benzyltriethylammonium chloride (4.2 kg, 18.44 mol, 0.05 eq) and chloroform (43.6 kg, 365.17 mol, 4 eq) was heated to 45-50 ° C for reaction for 20 min, and a 50% aqueous solution of sodium hydroxide (73.3 kg, 1830 mol, 5 eq) was added dropwise under vigorous stirring. The reaction temperature was intermittently adjusted at 50-60 ° C for 1.5 h, then stirred at 50-60 ° C for another 6 h, cooled to room temperature, diluted with water (90 L), the organic phase was separated, and vacuum concentrated at 40-50 ° C to obtain a crude product, which was distilled by a vacuum reactor with a water pump under the condition of -0.09 MPa, and a 60-90 ° C fraction was collected to obtain 45 kg of compound 2, with a yield of 75% and a GC purity of 99.26%. 1 H NMR (400MHz, DMSO-d6) δ2.145 (d, 1H), 2.26 (m, 1H), 2.03 (m, 1H), 1.69 (m, 2H). 13 CNMR (101 MHz, DMSO-d6) δ68.1325, 25.62, 20.22, 18.86.

[0093] (2) Synthesis of cycloheptatriene 3

[0094] Compound 2 (44.8 kg, 271.42 mol, 1 eq) and 2-pyrrolidone (134 kg, 39.48 mol, 3.0 v) were added to a reactor connected to a distillation apparatus. The reaction mixture was heated to 170-180° C., the reaction was controlled at normal pressure for 4 h, the reactant was distilled at 100 kPa, and the 80-100° C. fraction was collected to obtain a crude product. After removing the aqueous phase from the crude product, the organic phase was washed with a saturated sodium bicarbonate aqueous solution to obtain 20 kg of the product, with a yield of about 82% and a GC purity of 91.38%. The properties of the purified cycloheptatriene 3 were verified by GC-MS analysis, wherein the toluene content was less than 10%. 1 H NMR (400MHz, DMSO-d6) δ 6.59 (m, 2H), 6.18 (m, 2H), 5.35 (m, 2H), 2.18 (m, 2H). 13 C NMR (101MHz, DMSO-d6) δ130.86, 126.43, 120.54, 27.49.

[0095] (3) Synthesis of Compound 5

[0096] Compound 4 (21.1 kg, 216.52 mol, 1.05 eq) was mixed with the toluene-containing cycloheptatriene 3 (19 kg, 206.21 mol, 1.0 eq) synthesized in step (2) and toluene (200.0 kg). The mixture was heated to reflux for 3 h, and after cooling, MTBE (70 kg) was added. The precipitated solid was filtered and dried, and recrystallized using MTBE: ethanol (10: 1) as solvent. The yield was 82% and the purity was 99.83% (isomers) by HPLC. 32 kg of white crystalline compound 5 with a content of <0.03%). 1 H NMR (400MHz1, DMSO-d6) δ5.86 (s, 2H), 3.40 (t, J=1.9Hz, 2H), 3.29 (ddq, J=4.5, 2.8, 1.7Hz, 2H), 1.16 (s, 2H), 0.29 (s, 1H), 0.04 (s, 1H). 13 C NMR (101MHz, DMSO-d6) δ173.37, 128.31, 45.71, 40.15, 39.94, 39.73, 39.52, 39.21 (d, J=21.0Hz), 38.89, 33.08, 8.94, 8.73, 4.62.

[0097] (4) Synthesis of Compound 6

[0098] Compound 7 (50 kg, 244.92 mol, 1.0 eq) and 80% hydrazine hydrate (18.4 kg, 367.38 mol, 1.5 eq) were added into the reactor, stirred at 65-70°C for 1 hour, a mixture of methanol and water (25 kg / 200 kg) was added dropwise, and the mixture was refluxed for 4 hours. After the reaction was completed, the reaction mixture was diluted with water (250 kg), filtered, and the precipitate was dried to obtain a crude compound 6. The crude compound 6 was slurried with water (200 kg, 4 v), and then recrystallized with MTBE (150 kg, 3 v) to obtain 38 kg of compound 7 as a white solid (75%, HPLC purity is 99.95%). 1 H NMR (400MHz, DMSO-d6) δ10.02 (s, 1H), 8.01 (s, 2H), 7.82 (s, 2H), 4.60 (s, 2H). 13 C NMR (101MHz, DMSO-d6) δ 164.57, 137.13, 131.35 (d, J = 31.9Hz), 131.06, 127.89, 125.35, 122.60, 119.89, 39.53. ESI-MS(m / z):204.05[mH] - .

[0099] (5) Synthesis of Tecovir

[0100] Compound 5 (31.8 kg, 167.16 mol, 1.0 eq), compound 6 (35.7 kg, 175.55 mol, 1.05 eq) and DIEA (0.87 kg, 6.69 mol, 0.04 eq) and ethanol (250 kg, 10 v) were added to the reactor and heated to reflux for 4 h. After the reaction was completed, water (62 kg, 2 v) was added for crystallization. The resulting suspension was cooled, filtered, and dried at 50 ° C to obtain a crude product (65 kg), which was then recrystallized from ethanol: water (300 kg, 5:1 v / v) and dried to obtain 60 kg of tecovirizumab crystals (yield 96%, HPLC purity 99.97%). 1 H NMR (400MHz, DMSO-d6) δ11.40 (s, 1H), 8.10 (d, J=8.3Hz, 2H), 7.93 (d, J=8.3Hz, 2H), 5.90-5.67 (m, 2H), 3.26 (d, J=27.6Hz, 4H), 1.18 (d, J=8.4Hz, 2H), 0.32-0.19 (m, 1H), 0.07 (q, J=6.3, 4.2Hz, 1H). 13 CNMR (101MHz, DMSO-d6) δ174.77, 163.58, 163.13, 135.05, 134.67, 132.48, 132.17, 128.69, 127.62, 127 .34, 125.84, 125.81, 125.77, 125.73, 125.13, 122.42, 119.72, 43.39, 43.00, 33.08, 32.80, 9.22, 4.13. ESI-MS(m / z): 376.10[mH] - .

[0101] Example 4

[0102] For the reaction of synthesizing cycloheptatriene 3 from compound 2 in step (2) of the above reaction route, the reaction effects of different reaction solvents, temperatures, times and catalysts were compared. The results are shown in Table 1.

[0103] Table 1

[0104]

[0105]

[0106] a Reaction conditions: Compound 2 (1 eq), b Solvent (3v), cCatalyst (0.05eq), heated at 160-200°C for 2-6h, collected crude fractions at 70-90°C for 1.5h, monitored by GC-MS. d Isolated yield (40.0 g scale). f The purity was determined by GC. e Large scale results (2.2 kg scale), the remaining groups are 40 g small scale experiments.

[0107] First, we tried to use aprotic solvents, such as quinoline, MeOH (methanol) and PEG200 as reaction solvents. The reaction was pyrolyzed at 140-200°C for 1-6h, but the ideal product could not be obtained. Further, we tried to use aprotic polar solvents as reaction solvents, such as polyethylene glycol dimethyl ether (PEGDME), N, N-dimethylacetamide (DMAC), N-methylpyrrolidone (NMP), and 2-pyrrolidone. As shown in Table 1, when PEGDME was used as solvent, the yield of cycloheptatriene 3 was 21% under the conditions of reaction temperature of 180°C and reaction time of 6h, and the product contained excessive toluene (experiment 1); when DMAC was used as reaction solvent, the yield of cycloheptatriene 3 was relatively increased at high temperature, increased to 50% under the conditions of reaction temperature increased to 200°C and reaction time of 6h (experiment 2). It can be seen that polar solvents have a positive effect on the increase of yield. Experiments 3-4 using NMP or 2-pyrrolidone as the reaction solvent showed improved yield and purity compared to Experiments 1-2, especially for 2-pyrrolidone.

[0108] Experiments 4-6 show that satisfactory yields can be obtained by increasing the temperature and reaction time of the reaction with 2-pyrrolidone as the solvent. However, at a reaction temperature higher than 180°C, the purity of cycloheptatriene 3 is significantly reduced due to the decomposition of the solvent and the byproduct toluene during the reaction (experiment 7). Due to the potential safety hazards of the increased temperature in the pyrolysis reaction, no further research was conducted at temperatures above 180°C (temperatures between 180 and 200°C). From the perspective of reaction time, it is obvious that maintaining a reaction for 2 to 4 hours is appropriate, and extending the reaction time and increasing the temperature will not increase the yield and purity of the desired product (experiment 7).

[0109] Under low temperature conditions, it is usually difficult to increase the yield based on solvents. It is generally believed that catalysts can shorten the reaction time and increase the yield. Therefore, we tried to add CuCl and C to the 2-pyrrolidone reaction system. x2O, CuBr2 and CuBr and other copper catalysts. However, the results of tests 8-11 prove that this is not the case with this reaction, and the copper catalyst has no significant effect on the yield and purity of the desired product. Therefore, the test 12 of the scaled-up test repeated the conditions in test 6, and the by-product of this reaction was identified as toluene (8%) through GC-MS. As expected, the by-product of this reaction was identified as toluene (8%) through GC-MS.

[0110] Example 5

[0111] For the reaction of synthesizing compound 5 from compound 3 and maleic anhydride 4 in reaction step (3) of Example 1 above, based on this step, the effects of different maleic anhydride feed amounts and reaction temperatures on the reaction were adjusted. The results are shown in Table 2 below.

[0112] Table 2

[0113] test Maleic anhydride equivalent Reaction conditions Yield of compound 5 Product purity 1 1.2eq Toluene refluxed for 3 hours 72.4％ 99.86％ 2 1.05eq Toluene refluxed for 3 hours 82.0％ 99.83％ 3 1.05eq 80℃ for 3h 64.3％ 99.80％ 4 1.05eq 100℃ for 3h 77.4％ 99.89％

[0114] Example 6

[0115] For the reaction of synthesizing Tecovir from Compound 5 and Compound 6 in reaction step (5) of Example 1, based on the reaction in Example 1, the reaction effects of different amounts of catalysts, different amounts of reaction solvents, and different feed ratios were compared. The results are shown in Table 3 below.

[0116] Table 3

[0117] test Reaction conditions Yield purity 1 The reaction solvent was 10V ethanol, without catalyst 82.7％ Untested 2 The reaction solvent is 10V ethanol, 0.04eq triethylamine 89.5％ Untested 3 The reaction solvent is 10V ethanol, 1.0eq DIEA 34.0％ Untested 4 The reaction solvent is 10V ethanol, 0.04eq DIEA 91.0％ 99.88％ 5 The reaction solvent is 20V ethanol, 0.04eq DIEA 87.5％ 99.46％

[0118] Although embodiments of the present invention have been shown and described, it will be apparent to those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing cycloheptatriene, the method comprising: (i) Cyclohexene 1 reacts with chloroform in the presence of a catalyst M and an aqueous alkali solution to produce compound 2; (ii) Compound 2 undergoes a thermal decomposition reaction in solvent A to generate cycloheptatriene 3; the solvent A is one or more selected from 2-pyrrolidone, polyethylene glycol dimethyl ether, N,N-dimethylacetamide, and N-methylpyrrolidone; and the temperature of the thermal decomposition reaction is 160 to 200°C.

2. The preparation method according to claim 1, characterized in that: In step (i): The catalyst M is one or more selected from benzyltriethylammonium chloride, tetrabutylammonium bromide, tetrabutylammonium chloride, tetrabutylammonium hydrogen sulfate, trioctylmethylammonium chloride, dodecyltrimethylammonium chloride, tetradecyltrimethylammonium chloride, 18 crown 6, and cyclodextrin, preferably benzyltriethylammonium chloride; and / or The molar ratio of cyclohexene 1 to catalyst M is 1:0.01-0.10, preferably 1:0.04-0.10; and / or The alkali in the alkaline aqueous solution is one or more combinations selected from sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium carbonate, potassium carbonate and lithium carbonate, preferably sodium hydroxide; and / or The mass fraction of the alkaline aqueous solution is 30%-65%; preferably 40-60%; and / or The molar ratio of cyclohexene 1 to the base is 1:1 to 10, preferably 1:1 to 5; and / or The molar ratio of cyclohexene 1 to chloroform is 1:0.8-1.2, preferably 1:0.9-1.1; and / or The reaction temperature is 40-70°C, and the reaction time is 4-10h; preferably, the reaction temperature is 50-60°C, and the reaction time is 5-7h; or The reaction of step (i) adopts the following specific steps: heating a mixture of cyclohexene 1, catalyst M and chloroform to 45-50° C. for reaction for 10-60 min, and dripping the alkaline aqueous solution under vigorous stirring, the reaction temperature is intermittently adjusted at 40-70° C., preferably 50-60° C. for 0.5-3 h, and then continuing to keep warm and stir the reaction for 3-10 h.

3. The preparation method according to claim 1, characterized in that: After the reaction of step (i), a post-processing step is further included, wherein the post-processing step is: After the reaction solution is cooled to room temperature, it is diluted with water, the organic phase is separated, and concentrated to obtain a crude product, which is directly used for the reaction in step (ii); or After the reaction solution is cooled to room temperature, it is diluted with water, the organic phase is separated, and concentrated to obtain a crude product; the crude product is distilled at a pressure of -0.10 to 0.08 MPa, and the fraction at 60 to 90° C. is collected to obtain compound 2; alternatively, the crude product is subjected to reduced pressure distillation at a pressure of 2 to 5 kPa, and the fraction at 100 to 110° C. is collected to obtain compound 2.

4. The preparation method according to claim 1, characterized in that: In step (ii): The solvent A is 2-pyrrolidone; and / or The mass ratio of compound 2 to solvent A is 1:1 to 10, preferably 1:2 to 4; and / or The pyrolysis reaction pressure is 50-200 kPa, and the reaction time is 2-6 h; preferably, the reaction temperature is 170-180° C., the reaction pressure is 80-120 kPa, and the reaction time is 2-4 h.

5. The preparation method according to claim 1, characterized in that: After the pyrolysis reaction in step (ii), a separation and purification step is further included, which includes: collecting a fraction of 70 to 100° C. in the reaction product under a pressure of 80 to 120 kPa to obtain a crude product, removing the aqueous phase in the crude product, and washing the organic phase to obtain a purified product, namely cycloheptatriene 3; preferably, a saturated sodium bicarbonate aqueous solution is used to wash the organic phase; preferably, after washing the organic phase, a vacuum distillation step is further included, and the vacuum distillation is performed under a pressure of 2 to 10 kPa to collect a fraction of 20 to 30° C.; preferably, after the separation and purification step, the content of by-product toluene in the product is less than 10%.

6. Use of the intermediate 3 prepared by the preparation method according to any one of claims 1 to 5 in the preparation of Tecovirizumab.

7. A method for preparing Tecovir, comprising: (i) Cyclohexene 1 reacts with chloroform in the presence of a catalyst M and an aqueous alkali solution to produce compound 2; (ii) Compound 2 undergoes a thermal decomposition reaction in solvent A to generate cycloheptatriene 3; the solvent A is one or more selected from 2-pyrrolidone, polyethylene glycol dimethyl ether, N,N-dimethylacetamide, and N-methylpyrrolidone; the thermal decomposition reaction temperature is 160-200° C.; (iii) cycloheptatriene 3 reacts with compound 4 in solvent B to obtain compound 5; (iv) Compound 5 and Compound 6 undergo an amine condensation reaction in the presence of solvent C to obtain Tecovirizumab.

8. The preparation method according to claim 7, characterized in that: In steps (i)-(ii), the catalyst M, the alkaline aqueous solution, the solvent A, the amounts of the reactants, and the reaction conditions are as described in the method for preparing cycloheptatriene according to any one of claims 1 to 5; or, In step (iii): The molar ratio of compound 4 to cycloheptatriene 3 is 1-1.2:1, preferably 1-1.1:1; and / or The solvent B is selected from one or more of dioxane, 2-methyltetrahydrofuran, ethylene glycol dimethyl ether, toluene, xylene, chlorobenzene, acetonitrile, acetone, ethanol, isopropanol, n-butanol, tert-butanol, tert-amyl alcohol, ethylene glycol, pyridine, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, dimethyl sulfoxide, and water; preferably toluene; and / or The mass ratio of compound 3 to solvent B is 1:1 to 30, preferably 1:5 to 15; and / or The reaction temperature of step (iii) is 80-130°C, preferably 105-120°C; the reaction time is 1-5h; preferably 2-4h; preferably, step (iii) is refluxed under toluene; and / or In the reaction product of step (iii), isomers The content of isomers is less than 10%; preferably, the content of isomers is 5-8%; and / or After the reaction of step (iii) is completed, a purification step is further included, which comprises: adding methyl tert-butyl ether to the cooled reaction solution, separating and drying the precipitate, and then recrystallizing with a methyl tert-butyl ether-ethanol mixed solvent to obtain a purified product, namely compound 5; preferably, the volume ratio of the added amount of methyl tert-butyl ether to the reaction solution is 1:1-20, preferably 1:2-5, and more preferably 1:3-4; preferably, in the methyl tert-butyl ether-ethanol mixed solvent, the volume ratio of methyl tert-butyl ether to ethanol is 8-12:1, preferably 10:1; preferably, in the product of the purification step, the isomers The content is less than 0.03%.

9. The preparation method according to claim 7, characterized in that: In step (iv): The amine condensation reaction is carried out under the catalysis of a catalyst, wherein the catalyst is selected from an organic base, such as one or more of triethylamine, N,N-diisopropylethylamine, pyridine, morphine or N'N-dimethyl-4-aminopyridine, preferably N,N-diisopropylethylamine; and / or The molar ratio of compound 5 to the amount of catalyst is 1:0.01-1.0, preferably 1:0.01-0.1, more preferably 1:0.03-0.05; and / or The molar ratio of compound 5 to compound 6 is 0.8:1 to 1.2, preferably 0.9:1 to 1.1, more preferably 0.9:1 to 1.05; and / or The solvent C is one or more selected from methanol, ethanol, isopropanol, n-butanol or tert-butanol; preferably ethanol; the mass ratio of compound 5 to solvent C is 1:5-20, preferably 1:6-10; and / or The amine condensation reaction is carried out under reflux in solvent C for 2 to 6 hours, preferably 3 to 5 hours; After the amine condensation reaction, a purification step is also included, which includes: adding water to the reaction solution for crystallization, cooling, filtering to separate the solid and drying, and then recrystallizing from a solvent C-water mixed solution to obtain tecovir; preferably, the volume ratio of the added amount of water to the reaction solution is 1:3-8, preferably 1:4-6; preferably, the volume ratio of solvent C to water in the solvent C-water mixed solution is 1:3-8, preferably 1:4-6.

10. The preparation method according to claim 7, characterized in that: Compound 7 was obtained by the following method: (v) Compound 7 is reacted with anhydrous hydrazine or hydrated hydrazine in a methanol-water mixed solution under reflux to obtain Compound 6; Preferably, the molar ratio of compound 7 to anhydrous hydrazine or hydrazine hydrate, calculated as hydrazine, is 1:1-2, preferably 1:1.3-1.7, for example 1:1.5; and / or In the methanol-water mixed solution, the ratio of methanol to water is 1:6-10; and / or The mass ratio of compound 6 to the methanol-water mixed solution is 1:3-7, preferably 1:4-6; and / or The reflux reaction time is 2 to 8 hours, preferably 3 to 5 hours: Preferably, the reaction in step (v) adopts the following specific steps: Compound 7 and hydrazine hydrate are stirred at 65-70° C. for 0.5-3 h, then the above-mentioned methanol-water mixed solution is added dropwise, and the mixture is refluxed for reaction for 3-5 hours; Preferably, step (v) further includes a separation and purification step after the reaction, which includes: diluting the reaction solution with water, filtering, drying the precipitate to obtain a crude product, slurrying the crude product with water 2 to 6 times the mass of the crude product, and recrystallizing with methyl tert-butyl ether 2 to 5 times the mass of the crude product to obtain compound 6.

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