Method for preparing 3,6-disubstituted imidazo[1,2-b]pyridazine compounds

Abstract

The present disclosure relates to a method for preparing a 3,6-disubstituted-imidazo[1,2-b]pyridazine compound or a salt thereof.

Description

[Technical field]

[0001] The present disclosure relates to a 3,6-disubstituted-imidazo[1,2-b]pyridazine compound or a salt thereof. [Background technology]

[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 a neurotrophic tyrosine receptor kinase (NTRK) inhibitor, and has the following chemical structure: [ka]

[0003] 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine is known to be useful in the treatment of cancer. Summary of the Invention

[0004] The present disclosure is based on the unexpected discovery that a salt (e.g., a phosphate salt) of a 3,6-disubstituted-imidazo[1,2-b]pyridazine compound 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., having significantly improved yields).

[0005] In one embodiment, the present disclosure provides a method for producing a compound of formula (2): [ka] The compound of formula (3): [ka] to react with a compound of formula (4): [ka] 1. A method of manufacturing a compound comprising forming a compound of In some embodiments, the method includes removing the protecting group PG from a compound of formula (4) to form a compound of formula (5): [ka] The method further comprises forming a compound of the formula:

[0006] In another aspect, the disclosure features a pharmaceutical composition that includes particles including 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine monoadipate and a pharma- ceutically acceptable carrier, the particles having a particle size D50 of about 20 μm to 70 μm.

[0007] Other features, objects, and advantages will be apparent from the description and claims.

[0008] Detailed Description The present disclosure generally relates to methods for making 3-{4-[(2R)-2-aminopropoxy]phenyl}-N-[(1R)-1-(3-fluorophenyl)ethyl]-imidazo[1,2-b]pyridazin-6-amine (i.e., the compound of formula (5)), and salts thereof.

[0009] In one embodiment, the present disclosure provides a method for producing a compound of formula (2): [ka] The compound of formula (3): [ka] (i.e., (R)-3-bromo-N-(1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine) to give a compound of formula (4): [ka] 1. A method of manufacturing a compound comprising forming a compound of wherein BG is a boron-containing group (eg, a boronic ester or a boronic acid group) and PG is a protecting group for a nitrogen atom. In some embodiments, the reaction is a Suzuki coupling reaction.

[0010] In some embodiments, the salt of the compound of formula (3) can be an organic salt or an inorganic salt 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 phosphate, chloride, sulfate, fumarate, citrate, tartrate, oxalate, succinate, 2,5-dihydroxybenzoate, adipate, p-toluenesulfonate or malate. Preferably, the phosphate salt of the compound of formula (3) is used in the methods described herein. In some embodiments, the phosphate salt of the compound of formula (3) can contain 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 per mole of the compound of formula (3). In some embodiments, the phosphate salt of the compound of formula (3) may contain about 1.5 moles of phosphoric acid per mole of the compound of formula (3).Without wishing to be bound by theory, it is believed that the salt of the compound of formula (3) (e.g., phosphate salt) is in solid crystalline form, and therefore can be easily isolated from the preparation reaction with high purity and high yield.Furthermore, without wishing to be bound by theory, it is believed that the compound of formula (4) can be obtained in a significantly higher yield by using the salt of the compound of formula (3) (e.g., phosphate salt) as starting material than the free base of the compound of formula (3) (e.g., liquid form) as starting material.

[0011] In some embodiments, the amount of the compound of formula (2) can range from 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 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.

[0012] The protecting group (PG) of nitrogen atom described herein is not particularly limited as long as it is a substituent that reduces the reactivity of nitrogen atom to electrophilic addition reaction.For example, the protecting group 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-butoxycarbonyl group, a fluorenylmethoxycarbonyl group or a benzyloxycarbonyl group.

[0013] In some embodiments, BG is a boron-containing group suitable for Suzuki coupling reactions. Examples of suitable BGs include boronic ester groups (e.g., [ka] ) or a boronic acid group (e.g., [ka] ) are mentioned.

[0014] In some embodiments, the palladium catalyst described herein is a divalent palladium catalyst or a zerovalent palladium catalyst. An example of a zerovalent palladium catalyst is [tris(2-methylphenyl)phosphine]palladium(0).

[0015] In some embodiments, the palladium catalyst described herein comprises a reaction product of a monodentate phosphine or bidentate phosphine with a palladium compound. Examples of suitable monodentate phosphines include triphenylphosphine, tri-t-butylphosphine, and tris(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 comprise a reaction product of palladium acetate and triphenylphosphine. Without wishing to be bound by theory, the use of a reaction product of palladium acetate and triphenylphosphine as a catalyst in the reaction of a compound of formula (2) with a salt of a compound of formula (3) is believed to be advantageous over the use of a conventional catalyst (e.g., [1,1'-bis(diphenylphosphino)ferrocene]dichloro-palladium(II)-dichloromethane (Pd(dppf)Cl 2 ·CH 2 Cl 2 )) because the former catalyst can be easily removed from the reaction and much smaller amounts of the former catalyst are required to drive the reaction to completion and produce high yields of product, leading to improved reaction efficiency and reduced production costs.

[0016] In some embodiments, the reaction of the compound of formula (2) with the salt of the compound of formula (3) can be carried out using a relatively small amount of palladium catalyst.In some embodiments, the amount of palladium catalyst used in this reaction can be in the range of at least about 0.1 mol% (for example, 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% (for example, 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 mole of the compound of formula (3). Without wishing to be bound by theory, it is believed that by using a salt of the compound of formula (3) (which is a solid) as a starting material, the amount of palladium catalyst used to obtain the compound of formula (4) can be significantly reduced compared to using the free base of the compound of formula (3) (e.g., in liquid form) as a starting material, thereby substantially reducing the production costs of the final product (i.e., the compound of formula (5) or a salt thereof).

[0017] In some embodiments, the base for use 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.

[0018] Generally, the solvent that can be used in 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.Examples of suitable solvents include dimethylacetamide (DMAc), dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP), dimethylsulfoxide (DMSO), 4-dioxane and diethylene glycol dimethyl ether.In some embodiments, the solvent is miscible with water.

[0019] In some embodiments, the methods described herein provide for removing the protecting group PG from a compound of formula (4) to produce a compound of formula (5): [ka] The method may further include forming a compound of the formula:

[0020] In some embodiments, the deprotection reaction may be carried out in the presence of a mineral acid (e.g., hydrochloric acid). In some embodiments, the compound of formula (5) may be isolated by adding a base (e.g., sodium hydroxide) to the solution (e.g., HCl solution) obtained from the above reaction to adjust the pH to an appropriate value (e.g., about 12) and allowing the compound of formula (5) to crystallize and precipitate from the solution. Without wishing to be bound by theory, it is believed that using a mineral acid in the deprotection reaction and a base to precipitate the compound of formula (5) from the reaction solution is easy to handle and can significantly increase the yield (e.g., about 72% to about 90%) compared to the conventional method of using an organic acid (e.g., trifluoroacetic acid) in the deprotection reaction and isolating the compound of formula (5) by column chromatography.

[0021] In some embodiments, the method may further include reacting the compound of formula (5) with an acid (e.g., adipic acid) to form a salt of the compound of formula (5) (e.g., an adipate salt). Examples of suitable salts include inorganic acid salts and organic acid salts (e.g., amino acid salts). Examples of suitable inorganic salts include hydrohalides (e.g., hydrofluoride, hydrochloride, hydrobromide or hydroiodide salts), nitrates, perchlorates, sulfates and phosphates. Examples of suitable organic acid salts include C 1 -C 6Examples of suitable salts of amino acids include alkylsulfonates (e.g., methanesulfonates, trifluoromethanesulfonates or ethanesulfonates), arylsulfonates (e.g., benzenesulfonates or p-toluenesulfonates), acetates, malates, fumarates, succinates, citrates, ascorbates, tartrates, oxalates and adipates. Examples of suitable amino acid salts include glycine salts, lysine salts, arginine salts, ornithine salts, glutamate salts and aspartate salts.

[0022] In some embodiments, the method described herein may further comprise milling (e.g., wet milling) the salt of the compound of formula (5) to form particles with an appropriate size. Milling can be carried out by methods known in the art. In some embodiments, the particles comprising the salt of the compound of formula (5) (e.g., monoadipate salt) obtained from milling 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., has a D50 greater than 70 μm), the particles comprising the salt of the compound of formula (5) may have an undesirable dissolution profile (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 (e.g., having a D50 smaller than 20 μm), the production yield of the salt of the compound of formula (5) may be too low.

[0023] In some embodiments, the particles containing a salt of a compound of Formula (5) (e.g., the monoadipate salt) may 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, the particles containing the salt of the compound of formula (5) (e.g., 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 have improved particle size uniformity.

[0024] In some embodiments, the methods described herein provide a method for producing a compound of formula (1): [ka] with a boron-containing agent (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, e.g., DMAc). Without wishing to be bound by theory, the use of the reaction product of palladium acetate and triphenylphosphine as a catalyst in this reaction is more efficient than a conventional catalyst (e.g., [1,1'-bis(diphenylphosphino)ferrocene]dichloro-palladium(II)-dichloromethane (Pd(dppf)Cl2 ·CH 2 Cl 2 )) because (1) the reaction product of palladium acetate and triphenylphosphine can be easily removed from the reaction, and (2) the reaction product of palladium acetate and triphenylphosphine can improve the yield of the reaction even when the amount of palladium acetate used is significantly less, leading to improved reaction efficiency and reduced production costs.

[0025] In some embodiments, the reaction between the compound of formula (1) and the boron-containing agent (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 by carrying out the reaction between the compound of formula (1) and the boron-containing agent within the above reaction temperature range, the reaction time can be significantly shortened (e.g., from 12 hours to 2 hours) and the reaction yield can be improved (e.g., from about 75% to about 100%) compared to the case of carrying out the reaction at a conventional temperature (i.e., 80°C).

[0026] In some embodiments, the methods described herein include: 1-Bromo-4-fluorobenzene: [ka] and, D-Alaninol: [ka] and reacting with (R)-1-(4-bromophenoxy)propan-2-amine: [ka] and forming Protect the amino group in (R)-1-(4-bromophenoxy)propan-2-amine (e.g., (R)-1-(4-bromophenoxy)propan-2-amine with di-tert-butyl dicarbonate (Boc 2 O) to form a compound of formula (1); It may further include.

[0027] In some embodiments, the methods described herein include: Formula (6): [ka] (i.e., 3-bromo-6-chloroimidazo[1,2-b]pyridazine), Formula (7): [ka] (i.e., (R)-1-(3-fluorophenyl)ethan-1-amine) with to form a compound of formula (3). In some embodiments, this reaction can be carried out in the presence of a base (e.g., cesium fluoride). In some embodiments, the methods described herein can further include reacting the compound of formula (3) with an acid (e.g., phosphoric acid) to form an acid addition salt (e.g., a phosphate salt) 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 by carrying out the reaction of a compound of formula (6) with a compound of formula (7) in the presence of cesium fluoride, the reaction time can be significantly shortened (e.g., from 20-24 hours to 13-15 hours) and the reaction temperature can be reduced (e.g., from about 130° C. to about 110-120° C.) compared to carrying out 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) by the process described herein is more advantageous than forming a free base of the compound of formula (3). This is because, at least, (a) the acid addition salt of the compound of formula (3) can be readily isolated in high purity solid form RSM from the reaction mixture (which meets the Restricted Starting Materials (RSM) requirements imposed by regulatory agencies (e.g., the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA))), whereas the free base of the compound of formula (3) generally cannot be isolated in solid form (which does not meet the RSM requirements); and (b) the acid addition salt of the compound of formula (3) can be isolated in higher yield than the free base of the compound of formula (3).

[0028] In some embodiments, the amount of the compound of formula (6) in the reaction is greater than the amount of the compound of formula (7) and is in excess of 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 (for example, 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 amount of the compound of formula (6) can significantly improve the purity of at least the product obtained from the reaction, since the compound of formula (6) is more easily removed from the reaction product than the compound of formula (7).

[0029] In some embodiments, the present disclosure features a pharmaceutical composition comprising particles containing a 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) (e.g., a pharma- ceutically acceptable salt) and a pharma-ceutically acceptable carrier. In some embodiments, the particles can be obtained by using the milling method described herein. In some embodiments, the particles thus obtained can have a suitable particle size as 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.

[0030] Without wishing to be bound by theory, it is believed that pharmaceutical compositions comprising particles having a particle size as described herein (e.g., having a particle size D50 of at least about 20 μm to a maximum of about 70 μm) may have a dissolution rate that meets regulatory requirements. For example, the pharmaceutical compositions described herein may have a dissolution 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., compound of formula (5)) in an acetic acid dissolution medium having a pH of about 4 in 45 minutes, as measured by the method described in Example 6 below.

[0031] Examples of suitable pharma- ceutically acceptable salts include acid addition salts, for example, salts formed by reaction of a compound of formula (5) with hydrohalogen acids (e.g., hydrochloric acid or hydrobromic acid), mineral acids (e.g., sulfuric acid, phosphoric acid, and nitric acid), and aliphatic, alicyclic, aromatic or heterocyclic sulfonic or carboxylic acids (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, halobenzenesulfonic acid, trifluoroacetic acid, trifluoromethanesulfonic acid, toluenesulfonic acid, and naphthalenesulfonic acid).

[0032] The carrier in the pharmaceutical composition must be "acceptable" in the sense of being compatible with (and preferably capable of stabilizing) the active ingredient of the composition and not toxic to the subject being treated. One or more solubilizing agents can be utilized as pharmaceutical carriers for the delivery of the compound of formula (5) or its salt described herein. Examples of other carriers include colloidal silicon oxide, magnesium stearate, cellulose, sodium lauryl sulfate and D&C Yellow No. 10.

[0033] The pharmaceutical compositions described herein may optionally include at least one additional additive selected from disintegrants, binders, lubricants, flavoring agents, preservatives, coloring agents, and any mixture thereof. Examples of such additives and other additives are described in "Handbook of Pharmaceutical Excipients"; Ed. AH Kibbe, 3rd Ed., American Pharmaceutical Association, USA and Pharmaceutical Press UK, 2000.

[0034] The pharmaceutical compositions described herein can be adapted for oral administration or administration via the respiratory tract (e.g., in the form of aerosol or air-suspended fine powder) to subjects who need to treat a disease (e.g., cancer, such as non-small cell lung cancer or thyroid cancer).In some embodiments, the composition can be in the form of a tablet, capsule, powder, microparticle and granule.

[0035] The pharmaceutical compositions described herein generally contain a therapeutically effective amount of a compound of formula (5) or a salt thereof. By "therapeutically effective amount" is meant the amount of pharmaceutical composition required to confer a therapeutic effect on the treated subject (e.g., reversing, alleviating, delaying the onset of, or inhibiting the progression of cancer or one or more symptoms thereof).

[0036] The following examples are illustrative and not intended to be limiting.

[0037] Example 1: Preparation 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)) Synthesis of tert-butyl (R)-(1-(4-bromophenoxy)propan-2-yl)carbamate (compound of formula (1)) [ka]

[0038] NMP (4.5-5.5X), potassium t-butyl oxide (1.5 molar equivalents), and D-1-amino-2-propanol (1.1 molar equivalents) were added to the reactor. The mixture was stirred for 15-30 minutes, after which 1-bromo-4-fluorobenzene (1 molar equivalent) was added. The mixture was slowly heated to 65-75°C and then stirred at this temperature for 2-3 hours. After the in-process control (IPC) was qualified (i.e., the amount of the limiting reagent 1-bromo-4-fluorobenzene was less than or equal to 1% based on the relevant peak area of ​​HPLC), the mixture was cooled to 20-30°C. Isopropyl acetate (4.2-5.5X) and water (9.5-10.5X) were sequentially added to the above mixture. The mixture thus obtained was filtered through diatomaceous earth to separate the organic and aqueous phases. The aqueous phase was extracted with isopropyl acetate (4.5-5.5X), after which the organic phases were combined and washed twice with water (4.5-5.5X). The organic phase was concentrated to 3V, after which the isopropyl acetate was replaced with ethanol by adding ethanol (8X) twice to the organic phase and concentrated. The organic phase was finally concentrated to 3V. THF (1.9-2.1X) was added, followed by di-tert-butyl dicarbonate (1.3 molar equivalents) slowly at 0-10°C. The mixture was slowly warmed to 20-25°C and stirred at this temperature for 2-3 hours. After the IPC was qualified, ethanol (1.8-2X) was added, followed by water (7-9X) slowly. The mixture was stirred at this temperature for another 4-8 hours. The mixture was then centrifuged and the filtered product was washed with aqueous ethanol. The product thus obtained was recrystallized from aqueous ethanol and dried to give the title compound in 69-75% yield. The product had chiral purity ≧99.90%, individual impurities ≦0.10%, total impurities ≦0.50%, and residual water ≦0.50%.

[0039] 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)) [ka]

[0040] tert-Butyl (R)-(1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenoxy)propan-2-yl)carbamate (i.e., the compound of formula (2) described herein) was prepared using conventional methods and the method of the present invention as follows:

[0041] Traditional Method tert-Butyl (R)-(1-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)phenoxy)propan-2-yl)carbamate was prepared according to the procedure described in step 2 of Reference Example 1 in columns 27-28 of U.S. Pat. No. 9,187,489. Specifically, 10V of 1,4-dioxane, 1.0 molar equivalent of the above-obtained tert-butyl (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 equivalent of Pd(dppf)Cl were used. 2 ·CH 2 Cl 2were sequentially placed in a four-neck flask. 1V as used herein means 1 liter of solvent per Kg of limiting reagent (in this reaction, tert-butyl (R)-(1-(4-bromophenoxy)propan-2-yl)carbamate). The reaction mixture was degassed for 20 minutes, heated to 80°C, and maintained at this temperature under stirring for 4 hours. After the IPC was qualified (i.e., the amount of limiting reagent tert-butyl (R)-(1-(4-bromophenoxy)propan-2-yl)carbamate was 1% or less based on the corresponding peak area of ​​HPLC), the reaction mixture was cooled to 20°C. After adding 5V of ethyl acetate to the reaction mixture, the mixture was stirred for 10 minutes and filtered to remove insoluble matter. The mother liquor obtained by filtration was concentrated, dried, and purified by silica column chromatography to obtain the title product. The NMR of the product thus obtained was consistent with the NMR of the product obtained in Reference Example 15 shown on pages 31-32 of U.S. Patent No. 9,187,489.

[0042] Methods of the Invention 2.85 Kg / Kg of N,N-dimethylacetamide, 1.0 molar equivalent of tert-butyl (R)-(1-(4-bromophenoxy)propan-2-yl)carbamate (i.e., the compound of formula (1) above), 1.2 molar equivalent of bis(pinacolato)diboron and 0.006 molar equivalent of triphenylphosphine were sequentially charged into a four-neck flask. The flask was then purged with nitrogen until the oxygen content was 0.1% or less. 2.0 molar equivalents of potassium acetate and 0.002 molar equivalents of palladium acetate were added to the reaction mixture, after which the flask was again purged with nitrogen and monitored until the oxygen content was 0.1% or less. The reaction mixture was heated to 100° C. and maintained under stirring for 1 hour. After the IPC was qualified, the reaction mixture was cooled to 20° C. 5.93 Kg / Kg of methyl tert-butyl ether and aqueous sodium chloride solution were added to the reaction mixture in sequence, after which the mixture was stirred and allowed to stand to form two phases. After separating the upper organic phase, the organic phase was washed with sodium bicarbonate solution (i.e., by adding sodium bicarbonate to the organic phase, stirring the mixture, and separating the organic phase). Palladium acetate was then removed from the organic phase through a membrane stack. Next, the organic phase was washed sequentially with (1) 5 Kg / Kg of purified water and 0.09 Kg / Kg of ethylenediamine, (2) sodium carbonate solution, and (3) aqueous sodium chloride solution. Next, the organic phase was concentrated under reduced pressure to 10-20 V at a temperature of 40° C. or less. After adding 6.8 Kg / Kg of n-heptane to the organic phase, the organic phase was concentrated under reduced pressure to 60-80 V at a temperature of 40° C. or less. After adding 4.76 Kg / Kg of n-heptane to the organic phase, the organic phase was concentrated under reduced pressure to 60-80 V at a temperature of 40°C or less. The organic phase thus obtained was sampled and the residual methyl tert-butyl ether was measured, which was 1.0% or less. The solution thus obtained was heated to 45-55°C and stirred at that temperature. The solution was then cooled to 10-25°C and stirred at that temperature until a solid precipitated. After adding 2.04 Kg / Kg of n-heptane to the mixture, the mixture was cooled to a temperature of -5°C or less and maintained at that temperature for crystallization. The mixture was then filtered at a temperature of -5°C or less. The solid thus obtained was dried in an oven at 15-30°C until the residual n-heptane was 5% or less.1 H NMR (400 MHz, DMSO-d 6 ) δ 7.62 - 7.53 (m, 2H), 6.96 - 6.81 (m, 3H), 3.90 (p, J = 4.7, 4.2 Hz, 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).

[0043] The experimental conditions and results of the above-mentioned conventional method and the method of the present invention are summarized in Tables 1 and 2 below.

[0044] [Table 1]

[0045] [Table 2]

[0046] As shown in Tables 1 and 2 above, the method of the present invention surprisingly produced products in much higher yields than the conventional method, despite the use of a much smaller amount of palladium catalyst. Without wishing to be bound by theory, (1) the use of solution extraction as a purification step in the method of the present invention can significantly improve the yield of this reaction compared to the use of column chromatography as a purification step in the conventional method; (2) the use of the reaction product of palladium acetate and triphenylphosphine as a catalyst in the method of the present invention can significantly improve the yield of Pd(dppf)Cl in the conventional method. 2 ·CH 2 Cl 2 (3) the yield of the reaction can be improved compared to when Pd(dppf)Cl is used as a catalyst in the conventional method. 2 ·CH 2 Cl 2is believed to be cost ineffective because of the large amount of catalyst required (i.e., 0.1 molar equivalents) versus the small amount of palladium acetate required in the process of the present invention (0.002 molar equivalents).

[0047] Also, without wishing to be bound by theory, it is believed that the column chromatography used in the conventional method is a relatively tedious process, resulting in a low yield of the final product and not suitable for commercial production. In contrast, although the method of the present invention has an extra step for removing the palladium catalyst, the solution extraction and recrystallization procedures used in the method of the present invention are relatively simple and can provide a stable product with a relatively high yield. Moreover, unlike column chromatography, the solution extraction and recrystallization procedures used in the method of the present invention are easily scalable and suitable for commercial production.

[0048] Example 2: Preparation of the free base and phosphate salt of (R)-3-bromo-N-(1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine (compound of formula (3)) The free base and phosphate salt of (R)-3-bromo-N-(1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine (i.e., the compound of formula (3) described herein) were prepared using the following conventional methods and the method of the present invention, respectively:

[0049] Traditional Method [ka] The free base of (R)-3-bromo-N-(1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine was prepared according to the procedure described in step 1 of Example 1 in column 97 of U.S. Pat. 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)ethan-1-amine (i.e., the compound of formula (7) above), and 2.4 molar equivalent of potassium fluoride were sequentially placed in a four-neck flask. The reaction mixture was heated to 130° C. and maintained under stirring for 24 hours. The reaction mixture was sampled and, after IPC was qualified, cooled to 20° C. The reaction mixture was then added dropwise to ice water (100V) and stirred for 1-2 hours. The solid obtained was collected by filtration and dissolved in hot ethyl acetate. The insoluble material was removed by filtration under heat. The mother liquor thus obtained was concentrated to form a precipitate. The mixture was then filtered and the solid obtained was dried to obtain the free base of the compound of formula (3) as a crude brown solid. The NMR of the compound thus obtained was consistent with that of the product obtained from step 1 of Example 21 of U.S. Pat. No. 9,187,489.

[0050] Methods of the Invention [ka] 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)ethane-1-amine (i.e., the compound of formula (7) above), and 2.1 molar equivalents of cesium fluoride were sequentially placed in a four-neck flask. The reaction mixture was heated to 110-120°C and maintained under stirring for 13 hours. The reaction mixture was sampled and, after IPC was qualified, cooled to 20°C. Then, 5V of 2N aqueous potassium hydroxide solution, 10V of toluene, and 1V of acetonitrile were added to the reaction mixture obtained above. The mixture was stirred to form 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 adding 0.2 g / g of activated carbon to the organic phase, the mixture thus obtained was stirred for 1-3 hours, filtered under pressure, and the solid obtained was washed with toluene. The organic phase (containing both the molar solution from the filtration and the toluene solution) was washed with 5V of purified water until the pH was 7-8, and then concentrated to a volume of 3V.

[0051] After adding 18V of dimethoxyethane to the concentrated solution obtained above, the mixture thus obtained was heated to 45-55°C. Then, 2 molar equivalents of the dimethoxyethane phosphoric acid solution were added to the mixture. The reaction mixture thus obtained was stirred at 45-55°C for 1-2 hours, and then cooled to 15-25°C. The reaction mixture was filtered and dried to obtain the phosphate salt of the compound of formula (3) as a white solid. 1 H NMR (400 MHz, DMSO-d 6 ) δ 8.89 (s, 5H), 7.71 (d, J = 9.7 Hz, 2H), 7.46 (s, 1H), 7.40 - 7.15 (m, 3H), 7.02 (dddd, J = 9.1, 8.0, 2.7, 1.1 Hz, 1H), 6.76 (d, J = 9.7 Hz, 1H), 4.95 (t, J = 6.6 Hz, 1H), 1.49 (d, J = 7.0 Hz, 3H).

[0052] The experimental conditions and results of the above-mentioned conventional method and the method of the present invention are summarized in Tables 3 and 4 below.

[0053] [Table 3]

[0054] [Table 4]

[0055] As shown in Tables 3 and 4 above, the method of the present invention surprisingly produced products in higher purity and yield than the conventional methods, even though the reaction was carried out at a lower reaction temperature and for a shorter reaction time than the conventional methods. Without wishing to be bound by theory, it is believed that the phosphate salt of the compound of formula (3) is in a solid crystalline form and can be easily isolated in high purity and yield from the preparation reaction.

[0056] In addition, the conventional method produced a brown solid product of low quality containing residual solvents and impurities. This product (i.e., the compound of formula (3)) is a starting material for the drug (the compound of formula (5) or a salt thereof), and therefore must be a stable physical solid under the requirements of RSM. The conventional method did not produce a high-quality solid product, making it unsuitable for commercial production.

[0057] Example 3: Preparation of tert-butyl ((R)-1-(4-(6-(((R)-1-(3-fluorophenyl)ethyl)amino)-imidazo[1,2-b]pyridazin-3-yl)phenoxy)propan-2-yl)carbamate (compound of formula (4)) 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., the compound of formula (4) described herein) was prepared using conventional methods and the method of the present invention as follows:

[0058] Traditional Method [ka] 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. Pat. No. 9,187,489. Specifically, 73.5 V of 1,4-dioxane, 14.7 V 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 eq of the compound of formula (2) obtained in Example 1 above, 4.0 molar equivalents of potassium carbonate, and 0.1 molar equivalent of Pd(dppf)Cl were added to the reaction mixture. 2 ·CH 2 Cl 2 was added to a four-neck 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 IPC was qualified, the reaction mixture was cooled to 20°C. Ethyl acetate and purified water were added to the reaction mixture, and the mixture was stirred to form two phases. The organic phase was washed with saturated aqueous sodium chloride solution, dried over anhydrous magnesium sulfate, and concentrated to dryness. 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 from step 2 of Example 21 in column 125 of U.S. Pat. No. 9,187,489.

[0059] Methods of the Invention [ka] 4.68Kg / Kg of N,N-dimethylacetamide (DMAc), 1.0 molar equivalent of the compound of formula (3) phosphate salt obtained in Example 2 above, 1.51V of purified water and 4.6 molar equivalent of potassium hydroxide were sequentially placed in a four-neck flask. At a temperature of 20-30°C, 2.5V of purified water, 1.5 molar equivalent of potassium phosphate and 1.1 molar equivalent 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 was 0.1% or less. After adding 0.008 molar equivalent of triphenylphosphine and 0.004 molar equivalent of palladium acetate, the reaction mixture was again purged with nitrogen until the oxygen content was 0.1% or less. 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 4Kg / Kg of purified water to the reaction mixture, the mixture was extracted by adding 9Kg / Kg of ethyl acetate, stirred, and allowed to stand to separate into two phases. The upper organic phase was washed successively with (1) 3Kg / Kg of pure water and (2) sodium bicarbonate aqueous solution. After adding 0.1Kg / Kg of activated carbon to the organic phase at a temperature of 20-30°C, the organic phase was stirred and filtered to measure the palladium content. 5Kg / Kg of purified water and 0.38Kg / Kg of L-cysteine ​​were mixed and stirred to prepare an L-cysteine ​​solution. The organic phase was washed with (1) the L-cysteine ​​solution and (2) 5Kg / Kg of purified water at a temperature of 20-30°C, and the palladium content in the organic phase was measured. After adding 0.1Kg / Kg of activated carbon to the organic phase at a temperature of 20-30°C, the organic phase was stirred and filtered. After washing with 1.8Kg / Kg of ethyl acetate, the organic phases were combined and the palladium content was measured. If the palladium content was >7ppm, the L-cysteine ​​and activated carbon removal procedures were repeated until the palladium content was ≦7ppm. The organic phase was then concentrated to 6-8 vol. under reduced pressure at a temperature of 50°C or less. After adding 7.9Kg / Kg of methanol to the organic phase, the organic phase was concentrated to 6-8 vol. under reduced pressure at a temperature of 50°C or less. This process was repeated once, and the residual ethyl acetate in the organic phase was measured and confirmed to be ≦3%.The organic phase was heated to 45-55°C, after which 2Kg / Kg of purified water was added dropwise to the organic phase at this temperature with stirring, followed by 3Kg / Kg of purified water added dropwise to the organic phase at this temperature. The organic phase was then cooled to 0-10°C and maintained at this temperature with stirring to allow crystallization. The mixture was 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 obtained was dried in an oven below 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 (400 MHz, DMSO-d 6 ) δ 7.80 - 7.71 (m, 4H), 7.63 (d, J = 6.1 Hz, 1H), 7.41 (td, J = 7.8, 6.0 Hz, 1H), 7.31 - 7.21 (m, 2H), 7.03 (td, J = 8.6, 2.6 Hz, 1H), 6.97 - 6.90 (m, 3H), 6.77 (d, J = 9.7 Hz, 1H), 4.85 (p, J = 6.7 Hz, 1H), 3.96 (dd, J = 8.7, 5.4 Hz, 1H), 3.85 (dq, J = 21.5, 6.8 Hz, 2H), 1.49 (d, J = 6.9 Hz, 3H), 1.42 (s, 9H), 1.16 (d, J = 6.4 Hz, 3H).

[0060] The experimental conditions and results of the above conventional method and the method of the present invention are summarized in Tables 5 and 6 below.

[0061] [Table 5]

[0062] [Table 6]

[0063] As shown in Tables 5 and 6 above, the method of the present invention surprisingly produced a much higher yield and higher purity product than the conventional method, despite using a much smaller amount of palladium catalyst. Without wishing to be bound by theory, it is believed that the conventional method can produce a much higher yield and higher purity product than the conventional method, despite using a much smaller amount of palladium catalyst. 2 ·CH 2 Cl 2 would not be cost-effective to use because of the large amounts (i.e., 0.1 g / g) of this catalyst required, whereas the process of the present invention requires only small amounts (i.e., 0.004 molar equivalents) of palladium acetate.

[0064] Also, without wishing to be bound by theory, it is believed that the column chromatography used in the conventional method is a relatively laborious process, which reduces the yield of the final product. In contrast, although the method of the present invention has an extra step of removing the palladium catalyst, the solution extraction and recrystallization procedures used in the method of the present invention are relatively simple and can provide products with relatively high and consistent yields. Moreover, unlike column chromatography, the solution extraction and recrystallization procedures used in the method of the present invention are easily scalable and suitable for commercial production.

[0065] Example 4 Preparation of 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine (compound of formula (5)) [ka]

[0066] 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine (i.e., the compound of formula (5) described herein) was prepared using conventional methods and the method of the present invention as follows:

[0067] Traditional Method 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 that described in step 3 of Example 21 in column 126 of U.S. Pat. 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 sequentially placed in a four-neck flask. The reaction mixture was reacted at a temperature of 15-25°C for 1.5 hours. After IPC was qualified, the reaction mixture was washed with 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 that of the product obtained from step 3 of Example 21 in column 126 of U.S. Pat. No. 9,187,489.

[0068] Methods of the Invention 5.84Kg / Kg of anhydrous ethanol and 1.0 molar equivalent of the compound obtained in Example 3 above were sequentially placed in a four-neck flask. The reaction mixture was heated to a temperature of 65-75°C, maintained at this temperature, and 3 equivalents of hydrochloric acid were added dropwise and reacted for 3 hours. After the IPC was qualified, the temperature of the reaction mixture was maintained at 50-70°C, and 6.66Kg / kg of purified water was 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) was added dropwise to the reaction mixture. While maintaining the temperature at 60-70°C, the reaction mixture was stirred for 1-3 hours to check for solid crystallization. In the absence of crystallization, a seed crystal suspension (prepared from 0.00075Kg / Kg of seed crystal and 0.01Kg / Kg of water) was added to the reaction mixture and stirred for another 1-3 hours. If there is still no crystallization, repeat the above operation. Then, the reaction mixture was stirred at 70-75°C for 1-2 hours, cooled to -5-5°C, and maintained at this temperature for 3-5 hours to complete the crystallization. The reaction mixture was filtered, and the filter cake was washed with an ethanol solution (1.85Kg / Kg purified water, 1.46Kg / Kg ethanol, -5-5°C). After adding 3.7kg / kg purified water to the filter cake, the mixture was stirred for 10-30 minutes and filtered. The pH of the filter cake and the content of ethylenediamine residues in the filter cake were measured. If the pH was greater than 8, the filter cake was washed again with 3.7kg purified water until the pH of the filter cake was 8 or less.

[0069] The purity and residual amount of palladium in the filter cake were measured. The criteria were: purity ≥ 98.0%, compound of formula (5) without fluorine (major impurity) ≤ 1.0%, other individual impurities ≤ 0.30%, palladium residual ≤ 7 ppm. If the product did not meet any of the above criteria, the filter cake was washed and filtered again while maintaining the temperature of the filter cake below 50°C, and the solid thus produced was dried in an oven. Samples were taken and measured every 8-12 hours until the residual KF was below 5%. The solid was collected and its weight was recorded as Y.

[0070] After 3.945Y of anhydrous ethanol was added to the reaction tank 1, the above Y amount of solid was added to the reaction tank. The mixture was stirred at 20-30°C to completely dissolve, and then transferred to another reaction tank 2, where 0.05Y of activated carbon was moistened with 0.1Y-0.2Y of ethanol and added to the reaction tank 2 at 20-30°C and stirred at 20-30°C for 3-5 hours. The mixture was then filtered, the filter cake was eluted with 1.578Y of ethanol, and the eluate was mixed into tank 3. While maintaining the temperature of tank 3 at 30-40°C, 7Y of purified water was slowly added to the eluate, and the mixture was stirred for 1-3 hours. If there was no crystallization, a crystal seeding operation was performed (by adding 0.001Y of seed crystals and 0.01Y of water to the mixture and stirring the mixture for 1-3 hours to obtain a suspension), and repeated as necessary. If there was solid precipitation, the mixture was cooled to -5-5°C and maintained at that temperature for 3-5 hours to complete the crystallization. The mixture was filtered, and the filter cake was washed with an ethanol solution (prepared by mixing 2.5Y purified water and 1.97Y ethanol, stirring, and maintaining at -5 to 5°C). After the filter cake was placed in 5Y purified water, the mixture was stirred for 10 to 30 minutes and filtered. A sample of the filter cake was taken to measure its purity or residual palladium content. If the purity was ≥ 98.0%, the compound of formula (5) without fluorine ≤ 1.0%, other individual impurities ≤ 0.30%, and residual palladium ≤ 7 ppm, the filter cake was collected and dried. If any of the above criteria was not met, the above post-treatment operations were repeated until all of the above criteria were met. If the residual palladium met the relevant requirements, no further activated carbon was used to remove palladium.

[0071] The solid obtained above was dried in an oven at a temperature of 50° C. or less for 12 hours. Samples were then taken every 8 to 12 hours to check the residual solvent and moisture content until the residual ethanol was ≦0.5%, the residual ethyl acetate was ≦0.5%, and the residual KF was ≦5%. 1 H NMR (400 MHz, DMSO-d 6) δ 7.80 - 7.70 (m, 4H), 7.63 (d, J = 6.1 Hz, 1H), 7.40 (td, J = 7.9, 6.0 Hz, 1H), 7.31 - 7.21 (m, 2H), 7.07 - 6.99 (m, 1H), 6.96 - 6.89 (m, 2H), 6.77 (d, J = 9.6 Hz, 1H), 4.84 (p, J = 6.8 Hz, 1H), 3.85 - 3.69 (m, 2H), 3.17 (h, J = 6.3 Hz, 1H), 1.59 (s, 2H), 1.48 (d, J = 6.9 Hz, 3H), 1.09 (d, J = 6.5 Hz, 3H).

[0072] The experimental conditions and results of the above conventional method and the method of the present invention are summarized in Tables 7 and 8 below.

[0073] [Table 7]

[0074] [Table 8]

[0075] As shown in Tables 7 and 8 above, the method of the present invention surprisingly provided a much higher yield of product than the conventional method. Moreover, the yield in the conventional method (i.e., 72%) was much higher than the yield obtained from step 3 of Example 21 of U.S. Patent No. 9,187,489 (about 29%). In other words, the yield of the method of the present invention was substantially higher than the yield obtained from step 3 of Example 21 of U.S. Patent No. 9,187,489.

[0076] Without wishing to be bound by theory, it is believed that the reaction in the conventional method can be completed relatively quickly, but the post-treatment column chromatography is a relatively tedious purification process, resulting in relatively low and inconsistent yields. In contrast, although the method of the present invention includes additional crystallization steps as post-treatment of the manufacturing process, these steps are relatively simple to operate and can achieve high and consistent yields.

[0077] Example 5: Preparation of the adipate salt of 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine (compound of formula (5)) [ka]

[0078] The adipate salt of 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine (i.e., the adipate salt of the compound of formula (5) described herein) was prepared using conventional methods and the method of the present invention as follows:

[0079] Traditional Method 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 method described in Example 146, columns 228-229 of U.S. Pat. No. 9,187,489. Specifically, 10V of 1-propanol, 1.0 molar equivalent of the compound of formula (5) obtained from Example 4 above, and 1.1 molar equivalent of adipic acid were sequentially placed in a four-neck flask. The reaction mixture was stirred at 40° C. for 24 hours, cooled to 20° C., and stirred for another 0.5 hours to allow 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 that of the product obtained from step 3 of Example 21, column 126 of U.S. Pat. No. 9,187,489.

[0080] Methods of the Invention 3.156Kg / Kg of absolute ethanol and 1.0 molar equivalent of the compound of formula (5) obtained from Example 4 above were charged to the reactor. The reaction mixture was heated to 45-55°C (target: 50°C) and stirred until a clear solution was formed. An adipic acid solution was prepared by dissolving 0.396Kg / Kg (1.1 molar equivalents) of adipic acid in a mixed solution of 2.367Kg / Kg of absolute ethanol and 3.0Kg / Kg of purified water while maintaining the temperature at 10-30°C (target: 20°C). The adipic acid solution was charged to the reactor while maintaining the temperature at 45-55°C (target: 50°C) to form a mixture, which was stirred for 1-3 hours (target: 2 hours) after charging was completed. The reaction mixture was then concentrated under reduced pressure at 45-55 °C (target: 50 °C) to 4.0-6.0 volumes (target: 5.0 volumes) and stirred at this temperature for 0.5-1.5 hours (target: 1 hour) until solid precipitation occurred. The mixture was then cooled to 20-30 °C (target: 25 °C) at a cooling rate of 5-15 °C / h (target: 10 °C / h), after which 8.0 Kg / Kg of purified water was added to the mixture at 20-30 °C (target: 25 °C) and the mixture was stirred at this temperature for 0.5-1.5 hours (target: 1 hour). The mixture was 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 resulting solid was dried at a temperature of 70 °C or less until the LOD was 5% or less. The solid was then collected to obtain the crude product.

[0081] The crude product was purified and ground as follows: 4.02 Kg / Kg of absolute ethanol and 2.2 Kg / Kg of purified water were placed in a reactor and stirred, after which the crude product obtained above was added. The reaction mixture was heated to 65-70°C and stirred until a clear solution was obtained. The recommended stirring time was 0.5-1 h and the rotation speed was 60-100 rpm. The reaction mixture was then cooled to 50-55°C (target temperature: 53°C) at a recommended cooling rate of 5-10°C / h. 0.01 kg / kg of seed crystals of the adipate salt of the compound of formula (5) were added to the mixture at 50-55°C, after which the mixture was stirred at this temperature for 1-3 h (target: 2 h). The reaction mixture was cooled to 20-30°C (target temperature: 25°C) at a recommended cooling rate of 5-10°C / h. 8.4Kg / Kg of purified water was slowly added at 20-30°C for 1-3 hours (target: 2 hours) and then stirred at this temperature for 1-3 hours (target: 2 hours). The mixture was cooled to -5-5°C (target temperature: 0°C) at a cooling rate of 5-10°C / h and stirred at this temperature for 4-8 hours (target: 6 hours). The reaction mixture was passed through a wet mill (blade no. 2, blade no. 6, blade no. 6; rotation speed: 6,000-10,000 rpm, target: 8,000 rpm) while maintaining the temperature at -5°C-5°C (target temperature: 0°C). Samples were taken every 20-30 minutes to measure the particle size of the solid after wet milling until D50 was 45μm or less (target: 35-45μm). The reaction mixture was filtered through a filter equipped with a filter dryer precooled to T=-5-5°C. The filter cake was washed with a mixture of 1.1 Kg / Kg purified water and 0.39 Kg / Kg absolute ethanol, which was pre-cooled to -5-5°C and maintained for at least 0.5 hours. The solid thus obtained was dried at 50-60°C in an oven controlled at 70°C or less for 12 hours. Samples were taken every 4-8 hours to track the residual ethanol and it was found that the content of residual ethanol was 0.4% or less. After drying, the solid was cooled to 20-30°C to obtain the title compound in high purity. 1 H NMR (400 MHz, DMSO-d 6) δ 8.97 (s, 4H), 7.79 - 7.64 (m, 5H), 7.37 (td, J = 7.9, 6.0 Hz, 1H), 7.30 - 7.18 (m, 2H), 7.04 -- 6.91 (m, 3H), 6.80 (d, J = 9.7 Hz, 1H), 4.83 (p, J = 6.7 Hz, 1H), 4.10 - 3.89 (m, 2H), 3.52 - 3.35 (m, 1H), 2.14 (h, J = 3.4 Hz, 4H), 1.50 (h, J = 3.7, 3.3 Hz, 4H), 1.46 (d, J = 6.9 Hz, 3H), 1.25 (d, J = 6.6 Hz, 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 U.S. Pat. No. 9,187,489. The solid powder 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.

[0082] The experimental conditions and results of the above conventional method and the method of the present invention are summarized in Tables 9 and 10 below.

[0083] [Table 9]

[0084] [Table 10]

[0085] As shown in Tables 9 and 10, the method of the present invention surprisingly produced a higher yield of product than the conventional method, despite the increased number of steps. Furthermore, without wishing to be bound by theory, it is believed that the method of the present invention uses heating and cooling during the crystallization step, which can result in a product with a more uniform particle size. Furthermore, the method of the present invention includes a wet-milling step, which can result in a product with a desired particle size.

[0086] Example 6: Dissolution measurement of 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine monoadipate (monoadipate salt of the compound of formula (5)) Particles containing 3-(4-((R)-2-aminopropoxy)phenyl)-N-((R)-1-(3-fluorophenyl)ethyl)imidazo[1,2-b]pyridazin-6-amine monoadipate with eight different size distributions (i.e., batches No. 1-8) were prepared without milling or using a wet milling process similar to that described in Example 5. The particle size distributions of these eight batches are summarized in Table 11 below.

[0087] [Table 11]

[0088] Capsules containing the eight batches of particles were prepared, and the dissolution amounts of these capsules were measured using a Disek Model 2500 RTD Dissolution System available from Distek, Inc. (North Brunswick, NJ) using the dissolution parameters summarized in Table 12 below.

[0089] [Table 12]

[0090] The amount of active ingredient released from the capsules was measured using an ACQUITY Arc HPLC system equipped with a 2998 PDA detector and a 2489 UV / Vis detector available from Waters Corporation (Milford, Mass.) using the conditions summarized in Table 13 below.

[0091] [Table 13]

[0092] During use, the HPLC was allowed to equilibrate until a flat baseline was obtained. Chromatographs of the sample solutions were obtained using the minimum recommended injection sequence outlined in Table 14. The diluent was prepared by mixing 500 mL of 0.05 mol / L acetic acid-sodium acetate buffer (pH 4.0) and 500 mL of acetonitrile. Standard solutions 1 and 2 were prepared as follows: 28 mg (± 2.8 mg) of the monoadipate salt of the compound of formula (5) was accurately weighed into a 20 mL volumetric flask as a reference standard, and then approximately 15 mL of the diluent obtained above was added to the volumetric flask. The mixture was sonicated with occasional shaking until the solids were completely dissolved. The solution was cooled to temperature and diluted to 20 mL with the diluent above and mixed thoroughly. 2 mL of the above solution was accurately pipetted into a 20 mL volumetric flask and diluted to 20 mL with the dissolution solvent and mixed thoroughly.

[0093] [Table 14]

[0094] For HPLC to be suitable for measuring the amount of eluted active ingredient, the following requirements must be met: (1) No significant interference peaks should be observed in the blank chromatogram at the retention time of interest. (2) The peak area (x i (3) The relative standard deviation of the weight-converted peak area (x) of the active ingredient in BKT standard solution 1 (Std1 was injected after 10 sample injections and at the end of the sequence) is 2.0% or less. i ) is the average peak area ratio (R Ave ) must be within 98.0 to 102.0% of the

[0095] The amount of the active ingredient (i.e., the monoadipate salt of the compound of formula (5)) dissolved was calculated using the following four formulas.

number

number

number

[0096] The dissolution results are summarized in Table 15 below. [Table 15]

[0097] As shown in Tables 11 and 15, batch No. 8 (containing particles with a particle size D50 of 90 μm) showed a dissolution amount of 72 wt% in 45 min, which is below the relevant regulatory requirements (e.g., 75 wt% or 80 wt% dissolution amount in 45 min). In contrast, batches Nos. 1 to 7 (containing particles with a particle size D50 of 6.4 to 64 μm) could meet the relevant regulatory requirements.

[0098] Furthermore, the product yield of batch No. 1 (containing particles having a particle size D50 of 6.4 μm) is about 67%, which is lower than the product yields (e.g., 86-96%) of batches No. 2-8. Thus, although the product yield of batch No. 1 is acceptable, batch No. 1 is less preferred than batches No. 2-8.

[0099] Other embodiments are within the scope of the following claims.

Claims

1. In the presence of a palladium catalyst, a base and a solvent, Formula (2): 【Chemistry 1】 The compound Formula (3): 【Chemistry 2】 to react with a compound of formula (4): 【Chemistry 3】 forming a compound of formula (I) wherein BG is a boronic ester or acid group and PG is a protecting group for the nitrogen atom.

2. Removal of the protecting group PG from the compound of formula (4) gives a compound of formula (5): 【Chemistry 4】 2. The method of claim 1, further comprising forming a compound of formula:

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

5. 5. The method of claim 4, wherein the phosphate salt of the compound of formula (3) comprises about 1.5 moles of phosphoric acid per mole of the compound of formula (3).

6. 2. The method of claim 1, wherein PG is a tert-butoxycarbonyl group, a fluorenylmethoxycarbonyl group, or a benzyloxycarbonyl group.

7. BG, 【Chemistry 5】 The method of claim 1, wherein

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

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

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

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

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

13. 2. 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. 2. The method of claim 1, wherein the base comprises potassium hydroxide, sodium hydroxide, sodium carbonate, potassium carbonate or cesium carbonate.

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

16. Formula (1): 【Chemistry 6】 2. The method of claim 1, further comprising reacting the compound of formula (1) with a boron-containing agent to form a compound of formula (2).

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

18. 17. 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. 19. The method of claim 18, wherein the protection of 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. Formula (6): 【Chemistry 7】 The compound of formula (7): 【Chemistry 8】 2. The method of claim 1, further comprising reacting a compound of formula (3) with a compound of formula (4).

21. 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. 1. 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 pharma- ceutically acceptable carrier, wherein the particles have a particle size D50 of about 20 μm to 70 μm.

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

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

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

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

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

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