Process for preparation of 3, 6-disubstituted-imidazo [1, 2-b] pyridazine compounds

Abstract

Provided is a process for the preparation of a 3, 6-disubstituted-imidazo [1, 2-b] pyridazine compound or a salt thereof.

Description

Technical Field

[0001] The present disclosure relates to methods for preparing 3,6-disubstituted-imidazo[1,2-b]pyridazine compounds or salts thereof. Background Art

[0002] 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine is a known ROS1 receptor tyrosine kinase inhibitor and neurotrophic tyrosine receptor kinase (NTRK) inhibitor, and has the following chemical structure:

[0003]

[0004] 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine is known to be useful for the treatment of cancer. Summary of the invention

[0005] The present disclosure is based on the unexpected discovery that salts (e.g., phosphates) of 3,6-disubstituted-imidazo[1,2-b]pyridazine compounds can be used to prepare 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine in an improved manufacturing process (e.g., with significantly improved yield).

[0006] In one aspect, the disclosure features a method of making comprising making a compound of formula (2):

[0007]

[0008] With a salt of a compound of formula (3):

[0009]

[0010] In the presence of a palladium catalyst, a base and a solvent, a compound of formula (4) is formed:

[0011]

[0012] Wherein BG is a boron-containing group (e.g., a borate ester or a boronic acid group), and PG is a protecting group for the nitrogen atom. In some embodiments, the above method may further include removing the protecting group PG from the compound of formula (4) to form a compound of formula (5):

[0013]

[0014] In another aspect, the disclosure features a pharmaceutical composition including particles comprising 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine monoadipate and a pharmaceutically acceptable carrier, wherein the particles have a particle size D50 of about 20 μm to 70 μm.

[0015] Other features, objects, and advantages will be apparent from the description and from the claims. DETAILED DESCRIPTION

[0016] The present disclosure generally relates to methods of preparing 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine (ie, a compound of formula (5)) and salts thereof.

[0017] In one aspect, the disclosure features a method of making comprising making a compound of formula (2):

[0018]

[0019] and a salt of a compound of formula (3) (ie, (R)-3-bromo-N-(1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine):

[0020]

[0021] In the presence of a palladium catalyst, a base and a solvent, a compound of formula (4) is formed:

[0022]

[0023] wherein BG is a boron-containing group (eg, a borate ester or a boronic acid group), and PG is a protecting group for the nitrogen atom. In some embodiments, the above reaction is a Suzuki coupling reaction.

[0024] In some embodiments, the salt of the compound of formula (3) can be an organic salt or an inorganic salt, which can be obtained by reacting the compound of formula (3) with an organic acid or an inorganic acid. Examples of suitable salts of the compound of formula (3) include phosphates, chloride salts, sulfates, fumarates, citrates, tartrates, oxalates, succinates, 2,5-dihydroxybenzoates, adipates, p-toluenesulfonates or malate. Preferably, the phosphate of the compound of formula (3) is used in the methods described herein. In some embodiments, the phosphate of the compound of formula (3) can include at least about 1.35 moles (e.g., at least about 1.4 moles, at least about 1.45 moles or at least about 1.5 moles) to at most about 1.65 moles (e.g., at most about 1.6 moles, at most about 1.55 moles or at most about 1.5 moles) of phosphoric acid for every 1 mole of the compound of formula (3). In some embodiments, the phosphate of the compound of formula (3) can include about 1.5 moles of phosphoric acid for every 1 mole of the compound of formula (3). Without wishing to be bound by theory, it is believed that due to the salt (e.g., phosphate) of the compound of formula (3) being in solid crystalline form, it can be easily separated from its preparation reaction with high purity and high yield. In addition, without wishing to be bound by theory, it is believed that using the salt (e.g., phosphate) of the compound of formula (3) as a starting material can obtain the compound of formula (4) with significantly higher yield than using the free alkali (e.g., in liquid form) of the compound of formula (3) as a starting material.

[0025] In some embodiments, the amount of the compound of formula (2) can be at least about 0.8 moles (e.g., at least about 0.85 moles, at least about 0.9 moles, at least about 0.95 moles, or at least about 1 mole) to at most about 1.2 moles (e.g., at most about 1.15 moles, at most about 1.1 moles, at most about 1.05 moles, or at most about 1 mole) per 1 mole of the salt of the compound of formula (3). In some embodiments, the molar ratio of the compound of formula (2) to the salt of the compound of formula (3) is about 1.1:1.

[0026] The protecting group (PG) of the nitrogen atom described herein is not particularly limited as long as it is a substituent that reduces the reactivity of the nitrogen atom to the electrophilic addition reaction. For example, the protecting groups disclosed in Protective Groups in Organic Synthesis (TW Green and PGM Wuts, John Wiley & Sons, Inc., New York, 1991) can be used. In some embodiments, the protecting group is a tert-butyloxycarbonyl group, a fluorenylmethoxycarbonyl group, or a benzyloxycarbonyl group.

[0027] In some embodiments, BG is a boron-containing group suitable for Suzuki coupling reaction. Examples of suitable BG include borate ester groups (e.g., ) or a boronic acid group (e.g., ).

[0028] In some embodiments, the palladium catalyst described herein is a divalent palladium catalyst or a zero-valent palladium catalyst. An example of a zero-valent palladium catalyst is [tri(2-methylphenyl)phosphine]palladium(0).

[0029] In some embodiments, the palladium catalyst described herein includes the reaction product of a monodentate phosphine or a bidentate phosphine and a palladium compound. Examples of suitable monodentate phosphines include triphenylphosphine, tri-tert-butylphosphine and tri(2-methylphenyl)phosphine. Examples of suitable bidentate phosphines include 1,1-bis(diphenylphosphino)methane and 1,2-bis(diphenylphosphino)ethane. Examples of suitable palladium compounds include palladium chloride and palladium acetate. In some embodiments, the palladium catalyst described herein may include the reaction product of palladium acetate and triphenylphosphine. Without wishing to be bound by theory, it is believed that the use of the reaction product of palladium acetate and triphenylphosphine as a catalyst in the reaction between the compound of formula (2) and the salt of the compound of formula (3) can be superior to conventional catalysts (e.g., [1,1'-bis(diphenylphosphino)ferrocene]dichloro-palladium(II)-dichloromethane (Pd(dppf)Cl2·CH2Cl2)) because the former catalyst can be easily removed from the reaction and a smaller amount of the former catalyst is required to complete the reaction, thereby preparing the product in a higher yield, which improves the reaction efficiency and reduces the product cost.

[0030] In some embodiments, a relatively small amount of palladium catalyst can be used to carry out the reaction between the compound of formula (2) and the salt of the compound of formula (3). In some embodiments, the amount of palladium catalyst used in this reaction can be at least about 0.1 mol% (e.g., at least about 0.2 mol%, at least about 0.4 mol%, at least about 0.5 mol%, at least about 0.6 mol%, at least about 0.8 mol%, or at least about 1 mol%) to at most about 5 mol% (e.g., at most about 4.5 mol%, at most about 4 mol%, at most about 3.5 mol%, at most about 3 mol%, at most about 2.5 mol%, at most about 2 mol%, at most about 1.5 mol%, or at most about 1 mol%) per 1 mol of the compound of formula (3). Without wishing to be bound by theory, it is believed that using a salt of a compound of formula (3) (which is a solid) as a starting material can significantly reduce the amount of palladium catalyst used to obtain a compound of formula (4) compared to using a free base of a compound of formula (3) (e.g., in liquid form) as a starting material, which will significantly reduce the cost of preparing the final product (i.e., a compound of formula (5) or a salt thereof).

[0031] In some embodiments, the base used in the above reaction can be any suitable base that promotes the Suzuki coupling reaction. Examples of suitable bases include potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, and cesium carbonate.

[0032] Generally, the solvent that can be used for the above reaction is not particularly limited. In some embodiments, the solvent does not inhibit the aromatic substitution reaction involving the CH activation reaction catalyzed by palladium. The example of a suitable solvent includes dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethyl sulfoxide (DMSO), 4-dioxane and diethylene glycol dimethyl ether. In some embodiments, the solvent is miscible with water.

[0033] In some embodiments, the methods described herein may further comprise removing the protecting group PG from the compound of formula (4) to form a compound of formula (5):

[0034]

[0035] In some embodiments, the deprotection reaction can be carried out in the presence of an inorganic acid (e.g., hydrochloric acid). In some embodiments, the compound of formula (5) can be separated by adding a base (e.g., sodium hydroxide) to a solution (e.g., HCl solution) obtained from the above reaction to adjust the pH to a suitable value (e.g., about 12) so that the compound of formula (5) crystallizes and precipitates from the solution. Without wishing to be bound by theory, it is believed that the use of an inorganic acid in the deprotection reaction and the use of a base to precipitate the compound of formula (5) from the reaction solution involves easy handling and can significantly increase the yield (e.g., from about 72% to about 90%) compared to the conventional method of using an organic acid (e.g., trifluoroacetic acid) and separating the compound of formula (5) by column chromatography in the deprotection reaction.

[0036] In some embodiments, the above method may further include reacting the compound of formula (5) with an acid (e.g., adipic acid) to form a salt (e.g., adipate) of the compound of formula (5). Suitable examples of salts include inorganic acid salts and organic acid salts (e.g., amino acid salts). Suitable examples of inorganic salts include hydrohalides (e.g., hydrofluoride, hydrochloride, hydrobromide or hydroiodide salts), nitrates, perchlorates, sulfates and phosphates. Suitable examples of organic acid salts include C1-C6 alkyl sulfonates (e.g., mesylate, trifluoromethanesulfonate or ethanesulfonate), aryl sulfonates (e.g., benzenesulfonate or p-toluenesulfonate), acetates, malates, fumarates, succinates, citrates, ascorbates, tartrates, oxalates and adipates. Suitable examples of amino acid salts include glycine, lysine, arginine, ornithine, glutamate and aspartate.

[0037] In some embodiments, the methods described herein may also include grinding (e.g., wet grinding) a salt of a compound of formula (5) to form particles of suitable size. Grinding may be performed by methods known in the art. In some embodiments, particles obtained by grinding and containing a salt of a compound of formula (5) (e.g., monoadipate) may have a median particle size D50 of at least about 20 μm (e.g., at least about 25 μm, at least about 30 μm, at least about 35 μm, or at least about 40 μm) to at most about 70 μm (e.g., at most about 65 μm, at most about 60 μm, at most about 55 μm, at most about 50 μm, or at most about 45 μm). Without wishing to be bound by theory, it is believed that if the particle size is too large (e.g., having a D50 greater than 70 μm), the particles of the salt of the compound containing formula (5) may have an undesirable dissolution curve (e.g., the particles may have a dissolution rate that is too low to meet regulatory requirements). Furthermore, without wishing to be bound by theory, it is believed that if the particle size is too small (eg, having a D50 of less than 20 μm), the production yield of the salt of the compound of formula (5) may be too low.

[0038] In some embodiments, particles containing a salt of a compound of formula (5) (e.g., a monoadipate salt) can have a particle size D90 of at least about 50 μm (e.g., at least about 60 μm, at least about 70 μm, at least about 80 μm, at least about 90 μm, or at least about 100 μm) to at most about 150 μm (e.g., at most about 140 μm, at most about 130 μm, at most about 120 μm, at most about 110 μm, or at most about 100 μm). In some embodiments, particles containing a salt of a compound of formula (5) (e.g., a monoadipate salt) can have a particle size D10 of at least about 1 μm (e.g., at least about 1.5 μm, at least about 2 μm, at least about 4 μm, at least about 5 μm, at least about 6 μm, at least about 8 μm, at least about 10 μm, at least about 12 μm, or at least about 14 μm) to at most about 25 μm (e.g., at most about 24 μm, at most about 22 μm, at most about 20 μm, at most about 18 μm, at most about 16 μm, at most about 14 μm, at most about 12 μm, or at most about 10 μm). Without wishing to be bound by theory, it is believed that when the particles described herein have a relatively low D90 and a relatively high D10, the particles will have improved particle size uniformity.

[0039] In some embodiments, the methods described herein can further comprise subjecting a compound of formula (1):

[0040]

[0041] With a boron-containing reagent (e.g., bis(pinacolato)diboron) to form a compound of formula (2). In some embodiments, the reaction can be carried out in the presence of a palladium catalyst (e.g., the reaction product of palladium acetate and triphenylphosphine), a base (e.g., potassium acetate), and a solvent (e.g., a solvent described herein, such as DMAc). Without wishing to be bound by theory, it is believed that the use of the reaction product of palladium acetate and triphenylphosphine as a catalyst in the reaction can be superior to conventional catalysts (e.g., [1,1'-bis(diphenylphosphino)ferrocene]dichloro-palladium(II)-dichloromethane (Pd(dppf)Cl2 ·CH2Cl2)) because (1) the reaction product of palladium acetate and triphenylphosphine can be easily removed from the reaction, and (2) even when a smaller amount of palladium acetate is used, the reaction product of palladium acetate and triphenylphosphine can improve the yield of the reaction, which will improve the reaction efficiency and reduce the product cost.

[0042] In some embodiments, the reaction between the compound of formula (1) and the boron-containing reagent (e.g., bis(pinacolato)diboron) can be carried out at a relatively high temperature. For example, the reaction can be carried out at a temperature of at least about 85°C (e.g., at least about 90°C, at least about 95°C, or at least about 100°C) to at most about 120°C (e.g., at most about 115°C, at most about 110°C, at most about 105°C). Without wishing to be bound by theory, it is believed that carrying out the reaction between the compound of formula (1) and the boron-containing reagent within the above reaction temperature range can significantly shorten the reaction time (e.g., from 12 hours to 2 hours) and improve the reaction yield (e.g., from about 75% to about 100%) compared to carrying out the reaction at conventional temperature (i.e., 80°C).

[0043] In some embodiments, the methods described herein may further include subjecting 1-bromo-4-fluorobenzene to With D-alaninol Reaction to form (R)-1-(4-bromophenoxy)propan-2-amine And protecting the amino group in (R)-1-(4-bromophenoxy)propan-2-amine (for example, by reacting (R)-1-(4-bromophenoxy)propan-2-amine with di-tert-butyl dicarbonate (Boc2O)) to form a compound of formula (1).

[0044] In some embodiments, the methods described herein may further comprise treating a compound of formula (6) (ie, 3-bromo-6-chloroimidazo[1,2-b]pyridazine):

[0045]

[0046] Reaction with a compound of formula (7) (i.e., (R)-1-(3-fluorophenyl)ethan-1-amine):

[0047]

[0048] To form a compound of formula (3). In some embodiments, the reaction can be carried out in the presence of a base (e.g., cesium fluoride). In some embodiments, the method described herein may further include reacting the compound of formula (3) with an acid (e.g., phosphoric acid) to form an acid addition salt (e.g., phosphate) of the compound of formula (3). Examples of suitable acids include phosphoric acid, hydrochloric acid, sulfuric acid, fumaric acid, citric acid, tartaric acid, oxalic acid, succinic acid, 2,5-dihydroxybenzoic acid, adipic acid, p-toluenesulfonic acid, or malic acid. Without wishing to be bound by theory, it is believed that the reaction between the compound of formula (6) and the compound of formula (7) in the presence of cesium fluoride can significantly shorten the reaction time (e.g., from 20-24 hours to 13-15 hours) and reduce the reaction temperature (e.g., from about 130°C to about 110-120°C) compared to the reaction in the presence of a conventional base (e.g., potassium fluoride). Furthermore, without wishing to be bound by theory, it is believed that forming an acid addition salt of a compound of formula (3) in the manufacturing methods described herein is advantageous over forming a free base of a compound of formula (3) at least because (a) the acid addition salt of a compound of formula (3) can be readily isolated from the reaction mixture in a solid form having a high purity (which will meet the regulatory starting material (RSM) requirements imposed by regulators (e.g., the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA))), whereas the free base of a compound of formula (3) cannot typically be isolated in a solid form (which will not meet the RSM requirements), and (b) the acid addition salt of a compound of formula (3) can be isolated in a higher yield than the free base of a compound of formula (3).

[0049] In some embodiments, the amount of the compound of formula (6) in the above reaction is greater than and exceeds the amount of the compound of formula (7). For example, the molar ratio of the compound of formula (6) to the compound of formula (7) is at least about 1:02:1 (e.g., at least about 1.04:1, at least about 1.05:1, at least about 1.06:1, at least about 1.08:1, at least about 1.1:1, or at least about 1.15:1) or at most about 1.2:1. Without wishing to be bound by theory, it is believed that using an excess of the compound of formula (6) can significantly improve the purity of the product obtained by the above reaction, at least because the compound of formula (6) is easier to remove from the reaction product than the compound of formula (7).

[0050] In some embodiments, the disclosure features a pharmaceutical composition comprising particles containing a salt (e.g., a pharmaceutically acceptable salt) of a compound of formula (5) (e.g., 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine monoadipate) and a pharmaceutically acceptable carrier. In some embodiments, the particles can be obtained by using the grinding methods described herein. In some embodiments, the particles thus obtained can have a suitable particle size, such as those described above. For example, the particles thus obtained can have a particle size D50 of at least about 20 μm to at most about 70 μm, a particle size D90 of at least about 50 μm to at most about 150 μm, and / or a particle size D10 of at least about 1 μm to at most about 25 μm.

[0051] Without wishing to be bound by theory, it is believed that pharmaceutical compositions containing particles having a particle size described herein (e.g., having a particle size D50 of at least about 20 μm to at most about 70 μm) can have a dissolution rate that meets regulatory requirements. For example, as measured by the method described in Example 6 below, the pharmaceutical compositions described herein can have a dissolved amount of at least about 75 wt% (e.g., at least about 80 wt%, at least about 82 wt%, at least about 84 wt%, at least about 85 wt%, at least about 86 wt%, at least about 88 wt%, at least about 90 wt%, at least about 92 wt%, at least about 94 wt%, at least about 95 wt%, at least about 96 wt%, at least about 98 wt%, or at least about 99 wt%) to about 100 wt% of the total weight of the active ingredient (e.g., a compound of formula (5)) in an acetic acid dissolution medium having a pH of about 4 within 45 minutes.

[0052] Examples of suitable pharmaceutically acceptable salts include acid addition salts, such as salts formed by reaction between a compound of formula (5) and a hydrohalic acid (e.g., hydrochloric acid or hydrobromic acid), an inorganic acid (e.g., sulfuric acid, phosphoric acid and nitric acid) and an aliphatic, alicyclic, aromatic or heterocyclic sulfonic acid or carboxylic acid (e.g., formic acid, acetic acid, propionic acid, succinic acid, adipic acid, glycolic acid, lactic acid, malic acid, tartaric acid, citric acid, benzoic acid, ascorbic acid, maleic acid, hydroxymaleic acid, pyruvic acid, p-hydroxybenzoic acid, embonic acid, methanesulfonic acid, ethanesulfonic acid, hydroxyethanesulfonic acid, halogenated benzenesulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, toluenesulfonic acid and naphthalenesulfonic acid).

[0053] The carrier in the pharmaceutical composition must be "acceptable", that is, it is compatible with the active ingredient of the composition (and preferably, can stabilize the active ingredient) and is not harmful to the subject to be treated. One or more solubilizing agents can be used as a pharmaceutical carrier for delivering the compound of formula (5) described herein or its salt. Examples of other carriers include colloidal silicon oxide, magnesium stearate, cellulose, sodium lauryl sulfate and D&C Yellow #10.

[0054] The pharmaceutical compositions described herein may optionally include at least one other additive selected from disintegrants, binders, lubricants, flavoring agents, preservatives, colorants, and any mixture thereof. Examples of this and other additives can be found in "Handbook of Pharmaceutical Excipients"; Ed. AHKibbe, 3rd edition, American Pharmaceutical Association, USA and Pharmaceutical Press UK, 2000.

[0055] The pharmaceutical compositions described herein may be suitable for oral administration or for administration via the respiratory tract (e.g., in the form of an aerosol or air-suspended fine powder) to individuals in need of treatment of a disease (e.g., cancer, such as non-small cell lung cancer or thyroid cancer). In some embodiments, the compositions may be in the form of tablets, capsules, powders, microparticles, and granules.

[0056] The pharmaceutical compositions described herein generally include a therapeutically effective amount of a compound of formula (5) or a salt thereof. "Therapeutically effective amount" refers to the amount of the pharmaceutical composition required to impart a therapeutic effect (e.g., to reverse, alleviate, delay the onset of cancer or one or more symptoms thereof, or inhibit its progression) to the individual being treated.

[0057] The following examples are illustrative and not intended to be limiting.

[0058] Example

[0059] Example 1: (R)-(1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenoxy) Preparation of tert-butyl propan-2-yl)carbamate (compound of formula (2))

[0060] Synthesis of tert-butyl (R)-(1-(4-bromophenoxy)propan-2-yl)carbamate (compound of formula (1))

[0061]

[0062] NMP (4.5-5.5X), potassium tert-butoxide (1.5 molar equivalents), D-1-amino-2-propanol (1.1 molar equivalents) are added to the reactor. After the mixture is stirred for 15-30 minutes, 1-bromo-4-fluorobenzene (1 molar equivalent) is added. After the mixture is slowly heated to 65-75°C, it is stirred at this temperature for 2-3 hours. After the intermediate process control (IPC) is qualified (i.e., based on the relevant peak area in HPLC, the amount of limiting reagent 1-bromo-4-fluorobenzene does not exceed 1%), the mixture is cooled to 20-30°C. Isopropyl acetate (4.2-5.5X) and water (9.5-10.5X) are added to the above mixture in sequence. The mixture thus obtained is filtered through diatomaceous earth, and the organic phase is separated from the aqueous phase. After the aqueous phase is extracted with isopropyl acetate (4.5-5.5X), the organic phases are combined and washed twice with water (4.5-5.5X). After the organic phase is concentrated to 3V, isopropyl acetate is replaced by ethanol by adding ethanol (8X) to the organic phase and concentrating twice. The organic phase is finally concentrated to 3V. After adding THF (1.9-2.1X), di-tert-butyl dicarbonate (1.3 molar equivalents) is slowly added to the mixture at 0-10°C. The mixture is slowly warmed to 20-25°C and stirred at this temperature for 2-3 hours. After IPC is qualified, ethanol (1.8-2X) is added, and then water (7-9X) is slowly added. The mixture is stirred for another 4-8 hours at this temperature. The mixture is then centrifuged, and the filtered product is washed with ethanol aqueous solution. The product thus obtained is recrystallized and dried in ethanol aqueous solution to obtain the title compound with a yield of 69-75%. The product has a chiral purity of ≥99.90%, a single impurity ≤0.10%, a total impurity ≤0.50%, and residual water ≤0.50%.

[0063] Synthesis of tert-butyl (R)-(1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenoxy)propan-2-yl)carbamate (compound of formula (2))

[0064]

[0065] (R)-tert-butyl(1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenoxy)propan-2-yl)carbamate (ie, a compound of formula (2) described herein) was prepared using the following general and inventive methods:

[0066] Conventional methods

[0067] (R)-tert-butyl (1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenoxy)propan-2-yl)carbamate was prepared according to the process described in step 2 of reference example 1 in columns 27-28 of U.S. Patent No. 9,187,489. Specifically, 10V of 1,4-dioxane, 1.0 molar equivalent of the above-obtained (R)-(1-(4-bromophenoxy)propan-2-yl)carbamate, 1.2 molar equivalents of bis(pinacolato)diboron, 3.0 molar equivalents of potassium acetate and 0.1 molar equivalents of Pd(dppf)Cl2.CH2Cl2 were added sequentially to a four-necked flask. As used herein, 1V refers to 1 liter of solvent per 1Kg of limiting reagent (which is (R)-(1-(4-bromophenoxy)propan-2-yl)carbamate in this reaction). The reaction mixture was degassed for 20 minutes, heated to 80 ° C and kept stirring at this temperature for 4 hours. After IPC qualified (that is, based on the relevant peak area in HPLC, the amount of limiting reagent (R)-(1-(4-bromophenoxy) propan-2-yl) tert-butyl carbamate was no more than 1%), the reaction mixture was cooled to 20 ° C. After 5V of ethyl acetate was added to the reaction mixture, the mixture was stirred for 10 minutes, and filtered to remove any insoluble matter. The mother liquor obtained by filtration is concentrated, dried, and purified by silica gel column chromatography to obtain the title product. The NMR of the product thus obtained is consistent with the NMR of the product obtained in the reference example 15 shown on pages 31-32 of U.S. Patent No. 9,187,489.

[0068] Method of the present invention

[0069] 2.85Kg / Kg of N,N-dimethylacetamide, 1.0 molar equivalent of (R)-(1-(4-bromophenoxy)propan-2-yl)t-butyl carbamate (i.e., the compound of formula (1) described above), 1.2 molar equivalents of bis(pinacol)diboron and 0.006 molar equivalents of triphenylphosphine were sequentially charged into a four-necked flask. The flask was then purged with nitrogen until the oxygen content did not exceed 0.1%. After 2.0 molar equivalents of potassium acetate and 0.002 molar equivalents of palladium acetate were added to the reaction mixture, the flask was purged again with nitrogen and the oxygen content was monitored until it did not exceed 0.1%. The reaction mixture was heated to 100°C and kept under stirring for 1 hour. After the IPC was qualified, the reaction mixture was cooled to 20°C. After 5.93Kg / Kg of methyl tert-butyl ether and sodium chloride solution were sequentially added to the reaction mixture, the mixture was stirred and allowed to stand to form two phases. After separation of the upper organic phase, the organic phase is washed with a sodium bicarbonate solution (i.e., by adding sodium bicarbonate to the organic phase, stirring the mixture and separating the organic phase). Palladium acetate is subsequently removed from the organic phase by membrane stacking. The organic phase is then washed sequentially with (1) 5 Kg / Kg of purified water and 0.09 Kg / Kg of ethylenediamine, (2) a sodium carbonate solution and (3) a sodium chloride solution. The organic phase is then concentrated to 10-20 V under reduced pressure at a temperature not exceeding 40° C. After 6.8 Kg / Kg of n-heptane is added to the organic phase, the organic phase is concentrated to 60-80 V under reduced pressure at a temperature not exceeding 40° C. After 4.76 Kg / Kg of n-heptane is added to the organic phase, the organic phase is concentrated to 60-80 V under reduced pressure at a temperature not exceeding 40° C. The organic phase thus obtained is sampled and the residual methyl tert-butyl ether is measured to be no more than 1.0%. The solution thus obtained is heated to 45-55°C and stirred at this temperature. The solution is then cooled to 10-25°C and stirred at this temperature until solid precipitation. After 2.04 Kg / Kg of n-heptane is added to the mixture, the mixture is cooled to a temperature not exceeding -5°C and maintained at this temperature for crystallization. The mixture is then filtered at a temperature not exceeding -5°C. The solid thus obtained is dried in an oven at 15-30°C until the residual n-heptane does not exceed 5%. 1 H NMR (400MHz, DMSO-d6) δ7.62–7.53(m,2H),6.96–6.81(m,3H),3.90(p,J=4.7,4.2Hz, 1H), 3.81 (tt, J = 11.2, 5.9 Hz, 2H), 1.38 (s, 9H), 1.27 (s, 12H), 1.11 (d, J = 6.2 Hz, 3H).

[0070] The experimental conditions and results of the conventional method and the method of the present invention described above are summarized in Tables 1 and 2 below.

[0071] Table 1 Comparison of conditions between conventional method and the method of the present invention

[0072]

[0073]

[0074] Table 2 Comparison of experimental results between conventional method and the method of the present invention

[0075] Test Project Conventional methods Method of the present invention describe White solid White solid purity 99％ 99％ Yield 74％ 88％

[0076] As shown in Tables 1 and 2 above, the process of the present invention unexpectedly provides the product in a much higher yield than the conventional process even when a smaller amount of palladium catalyst is used. Without wishing to be bound by theory, it is believed that (1) the use of solution extraction as a purification method in the process of the present invention can significantly improve the yield of the reaction compared to the use of column chromatography as a purification method in the conventional process; (2) the use of the reaction product of palladium acetate and triphenylphosphine as a catalyst in the process of the present invention can also improve the yield of the reaction compared to the use of Pd(dppf)Cl2.CH2Cl2 as a catalyst in the conventional process; and (3) the use of Pd(dppf)Cl2.CH2Cl2 in the conventional process is not cost-effective because a large amount (i.e., 0.1 molar equivalent) of this catalyst is required, while only a small amount (i.e., 0.002 molar equivalent) of palladium acetate is required for the process of the present invention.

[0077] In addition, without wishing to be bound by theory, it is believed that the column chromatography used in the conventional method is a relatively cumbersome method, reduces the productive rate of the final product, and is not suitable for commercial manufacturing. On the contrary, although there is an additional step for removing the palladium catalyst in the inventive method, the solution extraction and recrystallization process used in the inventive method are relatively simple, and product can be obtained with relatively high and consistent productive rate. In addition, different from column chromatography, the solution extraction and recrystallization process used in the inventive method are easy to scale up and are suitable for commercial production.

[0078] Example 2: (R)-3-bromo-N-(1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazine-6-amine (Formula (3) Preparation of free base and phosphate salt of

[0079] The free base and phosphate salt of (R)-3-bromo-N-(1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine (ie, a compound of formula (3) described herein) were prepared using the following general and inventive methods, respectively:

[0080] Conventional methods

[0081]

[0082] (R)-3-bromo-N-(1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazine-6-amine free base was prepared according to the process described in step 1 of Example 1 in column 97 of U.S. Patent No. 9,187,489. Specifically, 20V of dimethyl sulfoxide (DMSO), 1.0 molar equivalent of 3-bromo-6-chloroimidazo[1,2-b]pyridazine (i.e., the compound of formula (6) above), 1.2 molar equivalent of (R)-1-(3-fluorophenyl)ethyl-1-amine (i.e., the compound of formula (7) above) and 2.4 molar equivalent of potassium fluoride were added sequentially to a four-necked flask. The reaction mixture was heated to 130°C and maintained under stirring for 24 hours. The reaction mixture was sampled and cooled to 20°C after passing the IPC. The reaction mixture was then added dropwise to ice water (100V) and stirred for 1 to 2 hours. The resulting solid was collected by filtration and dissolved in hot ethyl acetate. Insoluble matter is removed by filtration under heating. The mother liquor thus obtained is concentrated to form a precipitate. The mixture is then filtered and the resulting solid is dried to obtain the free base of the compound of formula (3) as a brown low-quality solid. The NMR of the compound thus obtained is consistent with the NMR of the product obtained from step 1 in Example 21 of U.S. Patent No. 9,187,489.

[0083] Method of the present invention

[0084]

[0085] 10V of DMSO, 1.1 molar equivalents of 3-bromo-6-chloroimidazo[1,2-b]pyridazine (i.e., the compound of formula (6) above), 1.0 molar equivalents of (R)-1-(3-fluorophenyl)ethyl-1-amine (i.e., the compound of formula (7) above), and 2.1 molar equivalents of cesium fluoride were added to a four-necked flask in sequence. The reaction mixture was heated to 110-120°C and kept under stirring for 13 hours. The reaction mixture was sampled and cooled to 20°C after passing the IPC. Subsequently, 5V of 2N potassium hydroxide solution, 10V of toluene, and 1V of acetonitrile were added to the reaction mixture obtained above. The mixture was stirred and formed into two phases, an aqueous phase and an organic phase. The aqueous phase was extracted with 5V of toluene and the toluene phase was combined with the previous organic phase. After 0.2g / g of activated carbon was added to the organic phase, the mixture thus obtained was stirred for 1-3 hours, filtered under pressure, and the resulting solid was washed with toluene. The organic phase (including both the molar liquid from the filtration and the toluene solution) was washed with 5V of purified water until it had a pH of 7-8 and concentrated to a volume of 3V.

[0086] After 18V of dimethoxyethane is added to the concentrated solution obtained above, the mixture thus obtained is heated to 45-55°C. Then 2 molar equivalents of dimethoxyethane phosphate solution are added to the mixture. The reaction mixture thus obtained is stirred at 45-55°C for 1-2 hours and then cooled to 15-25°C. The reaction mixture is filtered and dried to obtain the phosphate of the compound of formula (3) as a white solid. 1 H NMR (400MHz, DMSO-d6) δ8.89 (s, 5H), 7.71 (d, J = 9.7Hz, 2H), 7.46 (s, 1H), 7.40–7.15 (m, 3H), 7.02 (dd dd,J=9.1,8.0,2.7,1.1Hz,1H),6.76(d,J=9.7Hz,1H),4.95(t,J=6.6Hz,1H),1.49(d,J=7.0Hz,3H).

[0087] The experimental conditions and results of the conventional method and the method of the present invention described above are summarized in Tables 3 and 4 below.

[0088] Table 3 Comparison of conditions between conventional method and the method of the present invention

[0089]

[0090] Table 4 Comparison of experimental results between conventional method and the method of the present invention

[0091] Test Project Conventional methods Method of the present invention describe Brown low quality solid White solid purity 96％ 99％ Yield 87％ 89％

[0092] As shown in Table 3 and Table 4 above, even if the method of the present invention is carried out at a lower reaction temperature and a shorter reaction time than the conventional method, the method of the present invention unexpectedly obtains a product with a higher purity with a higher yield than the conventional method. Without wishing to be bound by theory, it is believed that since the phosphate of the compound of formula (3) is in a solid crystalline form, it can be easily separated from its preparation reaction with high purity and high yield.

[0093] In addition, conventional methods obtain brown low-quality solid products containing residual solvents and impurities. Since the product (i.e., the compound of formula (3)) is the starting material of a drug (the compound of formula (5) or its salt), it needs to be a stable physical solid under the RSM requirements. Since conventional methods cannot produce high-quality solid products, they are not suitable for commercial manufacturing.

[0094] Example 3: ((R)-1-(4-(6-(((R)-1-(3-fluorophenyl)ethyl)amino)-imidazo[1,2-b]pyridazine- Preparation of tert-butyl 3-(3-yl)phenoxy)propan-2-yl)carbamate (compound of formula (4))

[0095] tert-Butyl ((R)-1-(4-(6-(((R)-1-(3-fluorophenyl)ethyl)amino)imidazo[1,2-b]pyridazin-3-yl)phenoxy)propan-2-yl)carbamate (i.e., a compound of formula (4) described herein) was prepared using the following general and inventive methods:

[0096] Conventional methods

[0097]

[0098] Tert-butyl ((R)-1-(4-(6-(((R)-1-(3-fluorophenyl)ethyl)amino)imidazo[1,2-b]pyridazin-3-yl)phenoxy)propan-2-yl)carbamate was prepared according to the procedure described in step 2 of Example 21 in column 125 of U.S. Patent No. 9,187,489. Specifically, 73.5V of 1,4-dioxane, 14.7V of purified water, 1.0 molar equivalent of the free base of the compound of formula (3) obtained in Example 2 above, 1.2 molar equivalent of the compound of formula (2) obtained in Example 1 above, 4.0 molar equivalent of potassium carbonate and 0.1 molar equivalent of Pd(dppf)Cl2·CH2Cl2 were added to a four-necked flask. The reaction mixture was purged with nitrogen for 20 minutes, heated to 85°C, and stirred at this temperature for 1.5 hours. After passing the IPC, the reaction mixture was cooled to 20°C. After ethyl acetate and purified water were added to the reaction mixture, the mixture was stirred and allowed to form two phases. The organic phase was washed with a saturated sodium chloride solution, dried over anhydrous magnesium sulfate, concentrated and dried. The crude product was purified by column chromatography to obtain the title compound. The NMR of the compound thus obtained was consistent with that of the product obtained in step 2 of Example 21 in column 125 of U.S. Patent No. 9,187,489.

[0099] Method of the present invention

[0100]

[0101] 4.68Kg / Kg of N,N-dimethylacetamide (DMAc), 1.0 molar equivalent of the phosphate of the compound of formula (3) obtained in Example 2 above, 1.51V of purified water and 4.6 molar equivalents of potassium hydroxide were added to a four-necked flask in sequence. At a temperature of 20-30°C, 2.5V of purified water, 1.5 molar equivalents of potassium phosphate and 1.1 molar equivalents of the compound of formula (2) obtained in Example 1 above were added to the reaction mixture, which was stirred to completely dissolve the reagents. The reaction mixture was then purged with nitrogen until the oxygen content did not exceed 0.1%. After adding 0.008 molar equivalents of triphenylphosphine and 0.004 molar equivalents of palladium acetate, the reaction mixture was purged with nitrogen again until the oxygen content did not exceed 0.1%. The reaction mixture was then heated to 90°C and stirred at this temperature for 3 hours. After the IPC was qualified, the reaction mixture was cooled to 20°C. After adding 4 Kg / Kg of purified water to the reaction mixture, the mixture was extracted by adding 9 Kg / Kg of ethyl acetate, stirred, allowed to stand and separated into two phases. The upper organic phase was washed with (1) 3 Kg / Kg of purified water and (2) sodium bicarbonate solution in sequence. At a temperature of 20-30°C, after adding 0.1 Kg / Kg of activated carbon to the organic phase, the organic phase was stirred and filtered, and the palladium content was measured. 5 Kg / Kg of purified water and 0.38 Kg / Kg of L-cysteine ​​were mixed and stirred to prepare an L-cysteine ​​solution. At a temperature of 20-30°C, the above organic phase was washed with (1) L-cysteine ​​solution and (2) 5 Kg / Kg of purified water, and the palladium content in the organic phase was measured. At a temperature of 20-30°C, after adding 0.1 Kg / Kg of activated carbon to the organic phase, the organic phase was stirred and filtered. After washing with 1.8Kg / Kg of ethyl acetate, the organic phases are combined and the palladium content is measured. If the palladium content is >7ppm, repeat the L-cysteine ​​and activated carbon removal operation until the palladium content is ≤7ppm. The organic phase is then concentrated to 6-8 volumes under reduced pressure at a temperature not exceeding 50°C. After 7.9Kg / Kg of methanol is added to the organic phase, the organic phase is concentrated to 6-8 volumes under reduced pressure at a temperature not exceeding 50°C. Repeat this step once and measure the residual ethyl acetate in the organic phase to ensure that it does not exceed 3%. After the organic phase is heated to 45-55°C, 2Kg / Kg of purified water is added dropwise to the organic phase at this temperature while stirring, and then 3Kg / Kg of purified water is added dropwise to the organic phase at this temperature. The organic phase is then cooled to 0-10°C, maintained at this temperature, and stirred for crystallization. The mixture is filtered and eluted with a pre-cooled 0-10°C mixture of 0.79Kg / Kg of methanol and 0.7Kg / Kg of purified water. The solid thus obtained was dried in an oven at a temperature not exceeding 60° C. After drying for 24 hours, samples were taken every 4-12 hours until the loss on drying (LOD) was ≤ 1%.1 H NMR (400MHz, DMSO-d6) δ7.80–7.71(m,4H),7.63(d,J=6.1Hz,1H),7.41(td,J=7. 8,6.0Hz,1H),7.31–7.21(m,2H),7.03(td,J=8.6,2.6Hz,1H),6.97–6.90(m,3H), 6.77(d,J=9.7Hz,1H),4.85(p,J=6.7Hz,1H),3.96(dd,J=8.7,5.4Hz,1H),3.85(d q, J=21.5, 6.8Hz, 2H), 1.49 (d, J=6.9Hz, 3H), 1.42 (s, 9H), 1.16 (d, J=6.4Hz, 3H).

[0102] The experimental conditions and results of the conventional method and the method of the present invention described above are summarized in Tables 5 and 6 below.

[0103] Table 5 Comparison of conditions between conventional method and the method of the present invention

[0104]

[0105] Table 6 Comparison of experimental results between conventional method and the method of the present invention

[0106] Test Project Conventional methods Method of the present invention describe Light yellow solid White solid purity 95％ 99％ Yield 66％ 84％

[0107] As shown in Tables 5 and 6 above, the process of the present invention unexpectedly provides a product with higher purity in a much higher yield than the conventional process, even when a smaller amount of palladium catalyst is used. Without wishing to be bound by theory, it is believed that the use of Pd(dppf)Cl2.CH2Cl2 in the conventional process is not cost-effective because a large amount (i.e., 0.1 g / g) of this catalyst is required, while the process of the present invention requires only a small amount (i.e., 0.004 molar equivalent) of palladium acetate.

[0108] In addition, without wishing to be bound by theory, it is believed that the column chromatography used in the conventional method is a relatively cumbersome method, and reduces the productive rate of the final product. On the contrary, although there is an additional step of removing the palladium catalyst in the inventive method, the solution extraction and recrystallization process used in the inventive method are relatively simple, and can obtain the product with relatively high and consistent productive rate. In addition, different from column chromatography, the solution extraction and recrystallization process used in the inventive method are easy to scale up and are suitable for commercial production.

[0109] Example 4: 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl) Preparation of imidazo[1,2-b]pyridazine-6-amine (compound of formula (5))

[0110]

[0111] 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine (ie, a compound of formula (5) described herein) was prepared using the following general and inventive methods:

[0112] Conventional methods

[0113] 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine was prepared in a manner similar to the process described in step 3 of Example 21 in column 126 of U.S. Patent No. 9,187,489. Specifically, 10V of dichloromethane, 1.0 molar equivalent of the compound obtained in Example 3 above, and 2V of trifluoroacetic acid were added sequentially to a four-necked flask. The reaction mixture was reacted at a temperature of 15-25°C for 1.5 hours. After the IPC was qualified, the reaction mixture was washed with a sodium bicarbonate solution, and the aqueous phase was extracted with chloroform. The organic phases were combined, concentrated and dried. The crude product was purified by column chromatography to obtain the title compound. The NMR of the compound thus obtained was consistent with the NMR of the product obtained from step 3 of Example 21 in column 126 of U.S. Patent No. 9,187,489.

[0114] Method of the present invention

[0115] 5.84Kg / Kg of anhydrous ethanol and 1.0 molar equivalents of the compound obtained in Example 3 above are added to a four-necked flask in sequence. After the reaction mixture is heated to a temperature of 65-75°C and maintained at this temperature, 3 equivalents of hydrochloric acid are added dropwise to the reaction mixture to react for 3 hours. After IPC is qualified, the temperature of the reaction mixture is maintained at 50-70°C, and 6.66Kg / Kg of purified water is added to the reaction mixture. While maintaining the temperature at 60-70°C, 10N sodium hydroxide solution (containing 0.735Kg / Kg of purified water and 0.32Kg / Kg of sodium hydroxide) is added dropwise to the reaction mixture. While maintaining the temperature at 60-70°C, the reaction mixture is stirred for 1-3 hours, and solid crystallization is checked. If there is no crystallization, a seed suspension (which is prepared by 0.00075Kg / Kg of seed and 0.01Kg / Kg of water) is added to the reaction mixture, which is stirred for another 1 to 3 hours. If there is still no crystallization, repeat the above operation. Then stir the reaction mixture at 70-75 ° C for 1-2 hours, cool to -5-5 ° C, and keep 3-5 hours at this temperature to complete crystallization. The reaction mixture is filtered and the filter cake is washed with ethanol solution (1.85Kg / Kg of purified water and 1.46Kg / Kg of ethanol, -5-5 ° C). After 3.7Kg / Kg of purified water is added to the filter cake, the mixture is stirred for 10-30 minutes and filtered. Measure the pH of the filter cake and the content of ethylenediamine residues in the filter cake. If the pH is greater than 8, wash the filter cake again with 3.7Kg of purified water until the pH of the filter cake does not exceed 8.

[0116] The purity and residual amount of palladium in the filter cake are measured. The standards are as follows: purity ≥ 98.0%, fluorine-free compound of formula (5) (which is the main impurity) ≤ 1.0%, other individual impurities ≤ 0.30%, and palladium residue ≤ 7ppm. If the product does not meet any of the above standards, the filter cake is washed and filtered again, while the temperature of the filter cake is maintained at a temperature not exceeding 50° C., and the solid thus formed is dried in an oven. Samples are taken every 8 to 12 hours for measurement until the residual KF does not exceed 5%. The solid is collected and its weight is recorded as Y.

[0117] After 3.945Y of anhydrous ethanol is added to the reaction tank 1, the solid obtained above is added to the reactor in an amount of Y. The mixture is stirred at a temperature of 20-30°C to completely dissolve, and transferred to another reaction tank 2. 0.05Y of activated carbon is moistened with 0.1Y-0.2Y of ethanol and added to tank 2 at 20-30°C, and the mixture is stirred for 3-5 hours at 20-30°C. The mixture is then filtered, the filter cake is eluted with 1.578Y of ethanol, and the eluent is merged into tank 3. While the temperature of tank 3 is maintained at 30-40°C, 7Y of purified water is slowly added to the eluent, and the mixture is stirred for 1-3 hours. If there is no crystallization, a seed seeding operation is performed (by adding 0.001Y seed and 0.01Y water to the mixture to obtain a suspension and stirring the mixture for 1-3 hours), and if necessary, the seed seeding operation is repeated. If there is a solid precipitate, the mixture is cooled to -5-5°C and maintained at this temperature for 3-5 hours to complete crystallization. The mixture is filtered and the filter cake is washed with an ethanol solution (which is prepared by mixing 2.5Y of purified water and 1.97Y of ethanol, stirring and maintaining at -5-5°C). After the filter cake is added to 5Y of purified water, the mixture is stirred for 10-30 minutes and filtered. A sample of the filter cake is taken to measure its purity or the content of residual palladium. If the purity is ≥98.0%, the compound of formula (5) containing no fluorine is ≤1.0%, any other single impurity is ≤0.30%, and the residual palladium is ≤7ppm, the filter cake is collected and dried. If any of the above criteria is not met, the above post-treatment operation is repeated until all of the above criteria are met. If the residual palladium meets the relevant requirements, activated carbon is no longer used to remove palladium.

[0118] The solid obtained above was dried in an oven at a temperature not exceeding 50° C. for 12 hours. Then samples were taken every 8-12 hours to check the residual solvent and water content until the residual ethanol was ≤0.5%, the residual ethyl acetate was ≤0.5% and the residual KF was ≤5%. 1 H NMR(400MHz,DMSO-d6)δ7.80–7.70(m,4H),7.63(d,J=6.1Hz,1H),7.40(td ,J=7.9,6.0Hz,1H),7.31–7.21(m,2H),7.07–6.99(m,1H),6.96–6.89(m,2 H),6.77(d,J=9.6Hz,1H),4.84(p,J=6.8Hz,1H),3.85–3.69(m,2H),3.17( h, J=6.3Hz, 1H), 1.59 (s, 2H), 1.48 (d, J=6.9Hz, 3H), 1.09 (d, J=6.5Hz, 3H).

[0119] The experimental conditions and results of the conventional method and the method of the present invention described above are summarized in Tables 7 and 8 below.

[0120] Table 7 Comparison of conditions between conventional method and the method of the present invention

[0121]

[0122] Table 8 Comparison of experimental results between conventional method and the method of the present invention

[0123] Test Project Conventional methods Method of the present invention describe White solid White solid purity 99.6％ 99.9％ Yield 72％ 91％

[0124] As shown in Tables 7 and 8 above, the method of the present invention unexpectedly obtains the product in a much higher yield than the conventional method. In addition, the yield in the conventional method (i.e., 72%) is much higher than the yield obtained by step 3 of Example 21 of U.S. Patent No. 9,187,489 (i.e., about 29%). In other words, the yield of the method of the present invention is significantly higher than the yield obtained by step 3 of Example 21 of U.S. Patent No. 9,187,489.

[0125] Without wishing to be bound by theory, it is believed that although the reaction in the conventional method can be completed relatively quickly, the post-treatment column chromatography is a relatively cumbersome purification method, which results in relatively low and inconsistent yields. In contrast, although the method of the present invention involves an additional crystallization step as a post-treatment of the preparation process, these steps are relatively simple to operate and can achieve high and consistent yields.

[0126] Example 5: 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo Preparation of [1,2-b]pyridazine-6-amine (compound of formula (5)) adipate

[0127]

[0128] 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine adipate (i.e., the adipate salt of the compound of formula (5) described herein) was prepared using the following general methods and the methods of the present invention:

[0129] Conventional methods

[0130] 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine adipate was prepared according to the process described in Example 146 in columns 228-229 of U.S. Patent No. 9,187,489. Specifically, 10V of 1-propanol, 1.0 molar equivalent of the compound of formula (5) obtained in Example 4 above, and 1.1 molar equivalent of adipic acid were added sequentially to a four-necked flask. The reaction mixture was stirred at 40° C. for 24 hours, cooled to 20° C., and stirred for another 0.5 hour for crystallization. The reaction mixture was filtered, and the solid thus obtained was dried to obtain the title compound. The NMR of the compound thus obtained was consistent with the NMR of the product obtained in step 3 of Example 21 in column 126 of U.S. Patent No. 9,187,489.

[0131] Method of the present invention

[0132] 3.156 Kg / Kg of anhydrous ethanol and 1.0 molar equivalent of the compound of formula (5) obtained by Example 4 above are added to the reactor. The reaction mixture is heated to 45-55°C (target: 50°C) and stirred until a clear solution is formed. While maintaining the temperature at 10-30°C (target: 20°C), adipic acid solution is prepared by dissolving 0.396 Kg / Kg (1.1 molar equivalent) of adipic acid into a mixed solution of 2.367 Kg / Kg of anhydrous ethanol and 3.0 Kg / Kg of purified water. While maintaining the temperature at 45-55°C (target: 50°C), the adipic acid solution is added to the reactor to form a mixture, which is stirred for 1-3 hours (target: 2 hours) after the addition is completed. The reaction mixture is then concentrated under reduced pressure to 4.0-6.0 volumes (target: 5.0 volumes) at 45-55°C (target: 50°C) and stirred at this temperature for 0.5-1.5 hours (target: 1 hour) until there is a solid precipitate. After the mixture is cooled to 20-30°C (target: 25°C) at a cooling rate of 5-15°C / h (target: 10°C / h), 8.0 Kg / Kg of purified water is added to the mixture at 20-30°C (target: 25°C), and the mixture is stirred at this temperature for 0.5-1.5 hours (target: 1 hour). The mixture is then cooled to -5-5°C (target: 0°C) at a cooling rate of 5-15°C / h (target: 10°C / h), maintained at this temperature for 4-8 hours (target: 6 hours) and filtered. The solid thus obtained is dried at a temperature not exceeding 70°C until the LOD does not exceed 5%. The solid is then collected to obtain a crude product.

[0133] Purify and grind the crude product as follows: After 4.02Kg / Kg of anhydrous ethanol and 2.2Kg / Kg of purified water are added to the reactor and stirred, the crude product obtained above is added to the mixture. The reaction mixture is heated to 65-70°C and stirred until a clear solution is obtained. The recommended stirring time and speed are 0.5-1 hour and 60-100rpm, respectively. The reaction mixture is then cooled to 50-55°C (target temperature: 53°C) at a recommended cooling rate of 5-10°C / h. After 0.01Kg / Kg of adipic acid salt of the compound of formula (5) is added to the mixture at 50-55°C, the mixture is stirred for 1-3 hours (target: 2 hours) at this temperature. The reaction mixture is cooled to 20-30°C (target temperature: 25°C) at a recommended cooling rate of 5-10°C / h. After 8.4 Kg / Kg of purified water is slowly added to the mixture at 20-30°C over 1-3 hours (target: 2 hours), the mixture is stirred at this temperature for 1-3 hours (target: 2 hours). The mixture is cooled to -5 to 5°C (target temperature: 0°C) at a cooling rate of 5 to 10°C / h, and stirred at this temperature for 4 to 8 hours (target: 6 hours). While maintaining the temperature at -5 to 5°C (target temperature: 0°C), the reaction mixture is passed through a wet mill (blade numbers 2, 6, and 6; rotation speed: 6,000-10,000 rpm, target: 8,000 rpm). Samples are taken every 20-30 minutes to measure the particle size of the solid after wet milling until D50 does not exceed 45 μm (target: 35-45 μm). The reaction mixture is filtered through a filter with a filter dryer jacket pre-cooled to T = -5-5°C. The filter cake was washed with a mixture of 1.1 Kg / Kg of purified water and 0.39 Kg / Kg of anhydrous ethanol (precooled to -5-5°C and kept for at least 0.5 hours). The solid thus obtained was dried in an oven at 50-60°C for 12 hours at a controlled temperature not exceeding 70°C. Samples were taken every 4-8 hours to track the residual ethanol and to ensure that the residual ethanol content did not exceed 0.4%. After drying, the solid was cooled to 20-30°C to obtain the title compound in high purity. 1H NMR (400MHz, DMSO-d6) δ8.97 (s, 4H), 7.79–7.64 (m, 5H), 7.37 (td, J = 7.9, 6. 0Hz,1H),7.30–7.18(m,2H),7.04–6.91(m,3H),6.80(d,J=9.7Hz,1H),4.83 (p,J=6.7Hz,1H),4.10–3.89(m,2H),3.52–3.35(m,1H),2.14(h,J=3.4Hz,4 H), 1.50 (h, J = 3.7, 3.3Hz, 4H), 1.46 (d, J = 6.9Hz, 3H), 1.25 (d, J = 6.6Hz, 3H). The NMR of the compound thus obtained was consistent with that of the product obtained in step 3 of Example 21 in column 126 of US Pat. No. 9,187,489. The solid powder thus obtained had a particle size D10 of 7.2 μm, a particle size D50 of 44 μm, and a particle size D90 of 107 μm.

[0134] The experimental conditions and results of the conventional method and the method of the present invention described above are summarized in Tables 9 and 10 below.

[0135] Table 9 Comparison of conditions between conventional method and the method of the present invention

[0136] Synthetic pathway Solvents Reaction temperature Adipic acid Compound of formula (5) Reaction time Conventional methods 1-Propanol 40℃ 1.1 molar equivalent 1.0 molar equivalent 24h Method of the present invention EtOH 45～55℃ 1.1 molar equivalent 1.0 molar equivalent 1-3 hours

[0137] Table 10 Comparison of experimental results between conventional method and the method of the present invention

[0138] Test Project Conventional methods Method of the present invention describe White solid White solid purity 99.6％ 99.7％ Yield 91％ 94％

[0139] As shown in Tables 9 and 10 above, even though the inventive method involves more steps, the inventive method unexpectedly provides products in higher yields than conventional methods. In addition, without wishing to be bound by theory, it is believed that the inventive method uses heating and cooling during the crystallization process, which can result in products with more uniform particle sizes. In addition, the inventive method includes a wet grinding step, which can result in products with desired particle sizes.

[0140] Example 6: 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo Dissolution measurement of [1,2-b]pyridazin-6-amine monoadipate (monoadipate salt of the compound of formula (5))

[0141] Granules containing 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine monoadipate having eight different size distributions (i.e., batches 1-8) were prepared without milling or by using a wet milling process similar to that described in Example 5. The particle size distributions for these eight different batches are summarized in Table 11 below.

[0142] Table 11

[0143]

[0144] Capsules containing the above 8 batches of granules were prepared. The dissolution of these capsules was measured by a Distek Model 2500 RTD dissolution system available from Distek, Inc. (North Brunswick, NJ) using the dissolution parameters summarized in Table 12 below.

[0145] Table 12 Dissolution parameters

[0146]

[0147]

[0148] The amount of active ingredient dissolved from the capsules was measured by an ACQUITY Arc HPLC system purchased from Waters Corporation (Milford, MA) with a 2998 PDA detector and a 2489 UV / Vis detector using the conditions summarized in Table 13 below.

[0149] Table 13 Chromatographic conditions

[0150]

[0151] During use, balance HPLC until a flat baseline is obtained. The chromatogram of the sample solution is obtained using the minimum recommended injection sequence listed in Table 14. The diluent is prepared by mixing 500mL of 0.05mol / L acetic acid-sodium acetate buffer solution (pH 4.0) with 500mL of acetonitrile. Standard solutions 1 and 2 are prepared by the following process: after accurately weighing 28mg (± 2.8mg) of the monoadipic acid salt of the compound of formula (5) as a reference standard in a 20mL volumetric flask, about 15mL of the above obtained diluent is added to the volumetric flask. The mixture is ultrasonically treated under occasional shaking until the solid is completely dissolved. The solution is cooled to temperature, diluted to 20mL with the above diluent, and fully mixed. 2mL of the above solution is accurately drawn into a 20mL volumetric flask, diluted to 20mL with a dissolving medium, and fully mixed.

[0152] Table 14

[0153]

[0154] HPLC needs to meet the following requirements to be suitable for measuring the dissolved amount of active ingredients: (1) no obvious interfering peaks should be observed at the retention time of interest in the blank chromatogram; (2) the peak area (x ) of the active ingredient in the first 7 injections of the standard solution (5 × Std1 + 2 × Std2) should be i) The relative standard deviation of the weight conversion should not exceed 2.0%; and (3) the peak area (x i ) Weight conversion must be performed by averaging the peak area ratio (R Ave ) is within 98.0% to 102.0%.

[0155] The dissolved amount of active ingredient (i.e., the monoadipate salt of the compound of formula (5)) was calculated using the following four equations:

[0156]

[0157] Among them A Si is the peak area of ​​the active ingredient in the standard solution; W Si is the weight of the reference standard of the active ingredient (mg); F p is the purity factor of the reference standard of the active ingredient; x i is the peak area ratio of the active ingredient in the standard solution; R Ave is the average peak area ratio of the active ingredient in the first 7 injections of the standard solution; 405.47 is the molecular weight of the free form of the active ingredient (i.e., the compound of formula (5)); 551.61 is the molecular weight of the active ingredient; A T is the peak area of ​​the active ingredient obtained from the sample solution; L is the labeled amount of the capsule (mg); A n is the dissolved amount at each time point; and V1 is the constant sampling volume at each time point.

[0158] The dissolution results are summarized in Table 15 below.

[0159] Table 15

[0160]

[0161]

[0162] * Because the tested capsules were not completely dissolved, the RSD value at the 10-min time point was relatively large.

[0163] As shown in Tables 11 and 15, batch 8 (which contains particles having a particle size D50 of 90 μm) exhibited a dissolution amount of 72 wt% in 45 minutes, which is lower than the relevant regulatory requirements (e.g., a dissolution amount of 75 wt% or 80 wt% in 45 minutes). In contrast, batches 1-7 (which contain particles having a particle size D50 of 6.4-64 μm) were able to meet the relevant regulatory requirements.

[0164] In addition, the product yield of batch 1 (which contains particles having a particle size D50 of 6.4 μm) is about 67%, which is lower than the product yields of batches 2-8 (e.g., 86-96%). Therefore, although the product yield of batch 1 is acceptable, batch 1 is less preferred than batches 2-8.

[0165] Other implementations are within the scope of the following claims.

Claims

1. A manufacturing method comprising: The compound of formula (2): With a salt of a compound of formula (3): In the presence of a palladium catalyst, a base and a solvent, a compound of formula (4) is formed: wherein BG is a boronate ester or acid group, and PG is a protecting group for the nitrogen atom.

2. The method of claim 1, further comprising removing the protecting group PG from the compound of formula (4) to form a compound of formula (5):

3. The method of claim 3, further comprising reacting the compound of formula (5) with adipic acid to form an adipate salt of the compound of formula (5).

4. The method of claim 1, wherein the salt of the compound of formula (3) is a phosphate.

5. The method of claim 4, wherein the phosphate salt of the compound of formula (3) contains about 1.5 moles of phosphoric acid per 1 mole of the compound of formula (3). The method of claim 1 , wherein PG is a tert-butyloxycarbonyl group, a fluorenylmethoxycarbonyl group, or a benzyloxycarbonyl group.

7. The method of claim 1, wherein BG is 8. The method of claim 1, wherein the palladium catalyst comprises a reaction product of a monodentate phosphine or a bidentate phosphine and a palladium compound.

9. The method of claim 8, wherein the monodentate phosphine is triphenylphosphine, tri-tert-butylphosphine or tri(2-methylphenyl)phosphine.

10. The method of claim 8, wherein the bidentate phosphine is 1,1-bis(diphenylphosphino)methane or 1,2-bis(diphenylphosphino)ethane.

11. The method of claim 8, wherein the palladium compound is palladium chloride or palladium acetate.

12. The method of claim 8, wherein the palladium catalyst comprises the reaction product of palladium acetate and triphenylphosphine.

13. The method of claim 1, wherein the palladium catalyst is about 0.1 mol% to about 5 mol% based on the amount of the compound of formula (3).

14. The method of claim 1, wherein the base comprises potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate, or cesium carbonate.

15. The method of claim 1, wherein the solvent comprises dimethylacetamide, dimethylformamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide, 4-dioxane or diethylene glycol dimethyl ether.

16. The method of claim 1, further comprising treating a compound of formula (1): Reaction with a boron-containing reagent to form the compound of formula (2).

17. The method of claim 16, wherein the boron-containing reagent is bis(pinacolato)diboron.

18. The method of claim 16, further comprising reacting 1-bromo-4-fluorobenzene with D-alaninol to form (R)-1-(4-bromophenoxy)propan-2-amine, and protecting the amino group in (R)-1-(4-bromophenoxy)propan-2-amine to form the compound of formula (1).

19. The method of claim 18, wherein protecting the amino group in (R)-1-(4-bromophenoxy)propan-2-amine is carried out by reacting (R)-1-(4-bromophenoxy)propan-2-amine with di-tert-butyl dicarbonate.

20. The method of claim 1, further comprising treating a compound of formula (6): Reaction with a compound of formula (7): To form the compound of formula (3).

21. The method of claim 20, further comprising reacting the compound of formula (3) with an acid to form a salt of the compound of formula (3).

22. A pharmaceutical composition comprising: particles comprising 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine monoadipate; and a pharmaceutically acceptable carrier; The particles have a particle size D50 of about 20 μm to 70 μm.

23. The composition of claim 22, wherein the particles have a particle size D50 of about 20 μm to 60 μm.

24. The composition of claim 22, wherein the particles have a particle size D50 of about 25 μm to 55 μm.

25. The composition of claim 22, wherein the particles have a particle size D90 of about 50 μm to 150 μm.

26. The composition of claim 22, wherein the particles have a particle size D10 of about 1 μm to 25 μm.

27. The composition of claim 22, wherein the composition is a capsule or a tablet.

Images