Methods of preparing activin receptor-like kinase inhibitors

Abstract

This disclosure provides a method for preparing a compound represented by formula (I). The method comprises reacting a first starting material represented by formula (II) and a second starting material represented by formula (III) in a reaction mixture under Negishi conditions to form a compound of formula (I). R is an amine protecting group; Y is Cl, Br, or I; and Z is a trifluoromethanesulfonate, Cl, Br, or I.

Description

[0001] This application is a divisional application of patent application No. 202080068490.2, entitled "Method for preparing activin receptor-like kinase inhibitor", filed on October 2, 2020. Cross-references to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 62 / 909,533, filed October 2, 2019, the entire contents of which are incorporated herein by reference. Background Technology

[0003] Activin receptor-like kinase-2 (ALK2) is encoded by the activin A receptor, type I gene (ACVR1). ALK2 is a serine / threonine kinase in the bone morphogenetic protein (BMP) pathway (Shore et al., Nature Genetics 2006, 38: 525-27). Inhibitors of ALK2 and mutant forms of ALK2 have the potential to treat a variety of diseases, including progressive ossifying fibrous dysplasia (FOP); heterotopic ossification (HO) caused by, for example, major surgical treatment, trauma (e.g., head or blast injury), prolonged immobilization, or severe burns; diffuse endogenous pontine glioma (DIPG), a rare form of brain cancer; and anemia associated with chronic inflammatory, infectious, or neoplastic diseases.

[0004] U.S. Patent No. 10,233,186 discloses effective and highly selective inhibitors of ALK2 and its mutant forms, the entire teaching of which is incorporated herein by reference. U.S. Patent No. 10,233,186 also discloses compound 1, which serves as a key intermediate in the synthesis of the disclosed ALK2 inhibitor: Compound 1 US Patent No. 10,233,186 discloses the Suzuki reaction for preparing intermediates such as compound 1, as follows: It involves the coupling of pyrrolopyridazine intermediates with piperidinyl-pyridine compounds. Summary of the Invention

[0005] It has been found that the Suzuki coupling of 6-pyrrolopyridazine and pinacol diboronic acid ester piperidinyl-pyridine to prepare compound 1 results in a complex purity profile, while the formation of byproducts is significantly reduced in the corresponding Negishi coupling (Example 5). Negishi coupling has a further advantage in that it requires less of the expensive 6-pyrrolopyridazine starting material, involves only one separation step, and uses inexpensive reagents (ZnCl2 and...).i (-propylmagnesium chloride). Furthermore, based on the small-scale reaction, it can be expected that when compound 1 is prepared on an industrial scale using Negishi coupling, a much higher yield than that obtained using Suzuki coupling will be achieved. Based on these results, a new and improved synthesis of the important intermediate compound 1 is disclosed.

[0006] In one embodiment, this disclosure provides a method for preparing a compound represented by formula (I): The method includes reacting a first starting material, represented by formula (II), in the reaction mixture: The second starting material, represented by equation (III), reacts under Negishi conditions: The compound is formed of formula (I). R is an amine protecting group; Y is Cl, Br, or I; and Z is Cl, Br, I, or a trifluoromethanesulfonate (preferably Br). Amine protecting groups are well known in the art and are disclosed, for example, in TW Greene and PGMWuts, “Protective Groups in Organic Synthesis”, John Wiley and Sons, Inc., New York 1999. Protecting groups can be added and removed using methods known in the art. Examples of amine protecting groups include fluorenyl methyl carbamate, Cbz (benzyl carbamate), Boc (tert-butyl carbamate), acetamide, benzyl, and toluenesulfonyl (p-toluenesulfonamide). In one embodiment, the amine protecting group is Boc.

[0007] Another embodiment of this disclosure is a compound represented by formula (II), (II-A) or (II-B): , or Where Y, X and X 2 Each is independently Cl, Br, or I. In one embodiment, Y is Cl or I. As described in detail below, the compounds represented by formulas (II), (II-A), and (II-B) are intermediates in the disclosed Negishi reaction. Attached Figure Description

[0008] Figure 1 This is an ion-pair chromatography (IPC) purity profile of the reaction product obtained by preparing compound 1 via Suzuki coupling, as disclosed in U.S. Patent No. 10,233,186.

[0009] Figure 2 This is an overview of the IPC purity of the reaction product obtained by the method disclosed herein, namely the Negishi coupling preparation of compound 1. Detailed Implementation

[0010] This disclosure provides an improved method for preparing compound 1 in good yield and high purity via the Negishi reaction (also referred to herein as "Negishi coupling").

[0011] The Negishi reaction is a transition metal-catalyzed cross-coupling reaction. This reaction couples an organohalide or trifluoromethanesulfonate to an organozinc compound, thereby forming a carbon-carbon bond (cc) in this method. The transition metal catalyst is typically palladium or nickel. In the case of palladium, the catalyst is, for example, Pd(X) 1 Pd(0) in the form of )2; X 1 It is a phosphine ligand. Alternatively, Pd(0) can be derived from, for example, Pd(X). 1 Pd in ​​the form of 2Cl2 +2 The substance is generated in situ. Exemplary phosphine ligands include 1,1'-bis(di-tert-butylphosphino)ferrocene (dtbpf), 1,1'-bis(di-tert-butylphosphino)ferrocene (dcypf), 1,1'-bis(diphenylphosphino)ferrocene (dppf), and 2-di-tert-butylphosphino-2',4',6'-triisopropylbiphenyl ( t -BuXPhos), [2-(di-1-adamantylphosphino)-2',4',6'-triisopropyl-3,6-dimethoxybiphenyl][2-(2'-amino-1,1'-biphenyl)]palladium methanesulfonate(II) (AdBrettPhos), 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (SPhos), (2-dicyclohexylphosphino-2',6'-diisopropyloxy-1,1'-biphenyl)[2-(2'-amino-1,1'-biphenyl)]palladium methanesulfonate(II) (RuPhos), [2-dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl] (XPhos), [(2-dicyclohexylphosphino-3,6-dimethoxy-2',4',6'- Palladium(II) methanesulfonate (triisopropyl-1,1'-biphenyl)-2-(2'-amino-1,1'-biphenyl)] (BrettPhos), Palladium(II) methanesulfonate ((2-{bis[3,5-bis(trifluoromethyl)phenyl]phosphine}-3,6-dimethoxy-2',4',6'-triisopropyl-1,1'-biphenyl)-2-(2'-amino-1,1'-biphenyl)] (JackiePhos), Palladium(II) methanesulfonate ((2-di-tert-butylphosphino-3,6-dimethoxy-2',4',6'-triisopropyl-1,1'-biphenyl)-2-(2'-amino-1,1'-biphenyl)] ( ...t- BuBrettPhos), methanesulfonyl(2-(di-tert-butylphosphine)-1,1'-binaphthyl)[2-(2'-amino-1,1'-biphenyl)]palladium (TrixiePhos), (2-biphenyl)di-tert-butylphosphine, (2-biphenyl)di-tert-butylphosphine (JohnPhos), 2'-(di-tert-butylphosphine)-N,N-dimethylbiphenyl-2-amine ( t -BuDavePhos), 2-di-tert-butylphosphino-2'-methylbiphenyl ( t -BuMePhos), Chloro(2-dicyclohexylphosphino-1,1'-biphenyl)[2-(2'-amino-1,1'-biphenyl)]palladium(II) (CyJohnPhos), 2-dicyclohexylphosphino-2'-(N,N-dimethylamino)biphenyl (DavePhos), 2-dicyclohexylphosphino-2'-methylbiphenyl (MePhos), 2-dicyclohexylphosphino-2'-(N,N-dimethylamino)biphenyl (PhDavePhos), 2-dicyclohexylphosphino-2'-methoxy-4',6'-di-tert-butylbiphenyl (VPhos), 2-[(tert-butyl)phenylphosphine]-2',6'-bis(N,N-dimethylamino)biphenyl (PhCPhos) [(2-Dicyclohexylphosphino-2',6'-bis(N,N-dimethylamino)-1,1'-biphenyl)-2-(2'-amino-1,1'-biphenyl)]palladium(II)methanesulfonate (CPhos), methanesulfonate [2-diethylphosphino-2',6'-bis(dimethylamino)-1,1-biphenyl](2'-amino-1,1'-biphenyl-2-yl)palladium(II) (EtCPhos), 2-bis(tert-butyl)phosphino-2',4',6'-triisopropyl-3-methoxy-6-methylbiphenyl (RockPhos), di-1-adamantyl(4”-butyl-2”,3”,5”,6”-tetrafluoro-2',4',6'-triisopropyl-2-methoxy-m-terphenyl) Phosphine (AlPhos) and 2-(tert-butylphenylphosphine)-2',6'-dimethylamino-1,1'-biphenyl ((t-Bu)PhCPhos).

[0012] Exemplary palladium catalysts include Pd(dppe)2 (bis[1,2-bis(diphenylphosphine)ethane]palladium(0)), Pd(dba)2 (bis(dibenzylideneacetone)palladium(0)), CX-11 (1,3-bis(2,6-diisopropylphenyl)imidazolium-2-ylidene(1,4-naphthoquinone)palladium(0) dimer), CX-12 (1,3-bis(2,4,6-trimethylphenyl)imidazolium-2-ylidene(1,4-naphthoquinone)palladium(0) dimer), Pd(t-Bu3P)2(bis(tri-tert-butylphosphine)palladium(0)), Pd(PCy3)2(bis(tricyclohexylphosphine)palladium(0)), Pd(PPh3)4(tetra(triphenylphosphine)palladium(0)), Pd2(dba)3(tris(dibenzylacetone)dipalladium(0)), Pd(OAc)2(palladium(II) acetate), PdCl2(PPh3)2(dichlorobis(triphenylphosphine)palladium(II)), PdCl2(Amphos)2(bis(di-tert-butyl(4-dimethylaminophenyl)phosphine)dichloropalladium(II)), Pd(MeCN)2Cl2(bis(acetonitrile)dichloropalladium(II)), PdCl2(P( o -Tol)3)2(dichlorobis(tri-o-tolylphosphine)palladium(II)), Pd(dppf)Cl2(1,1'-bis(diphenylphosphine)ferrocene]dichloropalladium(II)), Pd(MeCN)4(BF4)2(tetra(acetonitrile)palladium(II)tetrafluoroborate), Pd-PEPPSI-IPent (dichloro[1,3-bis(2,6-di-3-pentylphenyl)imidazol-2-ylidene](3-chloropyridinyl)palladium(II)), Pd-PEPPSI-IPr ([1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](3-chloropyridinyl)palladium(II)) and Pd-PEPPSI-SIPr ((1,3-bis(2,6-diisopropylphenyl)imidazoline)(3-chloropyridinyl)palladium(II)).

[0013] Alternatively, the palladium catalyst can be selected from Pd(MeCN)2Cl2, Pd[P( o -Tol)3]2Cl2, PdCl2(Amphos)2, and Pd(dba)2. In another alternative, the palladium catalyst is selected from Pd2(dba)3 / P(R 1 )3, Pd(PPh3)4, Pd(PPh3)2Cl2, Pd(MeCN)2Cl2, Pd[P( o -Tol)3]2Cl2, PdCl2(Amphos)2, Pd(PtBu3)2, Pd(dppf)Cl2, Pd(dba)2, Pd2(dba)3 and Pd(XPhos); each R 1It is a C1-C6 alkyl, C3-C6 cycloalkyl, benzyl, or phenyl group, wherein each of the benzyl or phenyl groups is optionally and independently substituted by one or more groups selected from halogens, C1-C3 alkyl groups, and C1-C3 alkoxy groups. In another alternative, the palladium catalyst is Pd2(dba)3. In yet another alternative, the palladium catalyst is pdp( t Bu)3.

[0014] In another embodiment, the palladium catalyst may be conjugated with a phosphine ligand, for example, a palladium catalyst conjugated with P( t Pd2(dba) of Bu)3 combination.

[0015] In the case of nickel, the catalyst is Ni(0); and Ni(0) can be produced by Ni +2 Substances such as NiCl2 are generated in situ. Exemplary nickel catalysts include Ni(acac)2, Ni(cod)2, Ni(PCy3)2Cl2, NiBr2, NiI2, Ni(OAc)2, Ni(OTf)2, Ni(BF4)2, and NiCl2(PPh3)2.

[0016] In the Negishi reaction, the organohalide or organotrifluoromethanesulfonate can be an alkenyl, aryl, allyl, alkynyl, or propargyl halide or trifluoromethanesulfonate; and the organozinc compound is R-Zn-X, where X is a chloride, bromide, or iodide, and R is alkenyl, aryl, allyl, alkyl, benzyl, homoallyl, or homopropargyl. Conditions for the Negishi reaction are described, for example, in *Recent Developments in Negishi Cross-Coupling Reactions* by Diana Haas, Jeffrey M. Hammann, Robert Greiner, and Paul Knochel. ACS Catal. 2016, V6(3)p1540-1552; Mild Negishi Cross-Coupling Reactions Catalyzed byAcenaphthoimidazolylidene Palladium Complexes at Low Catalyst Loadings Z.Liu, N. Dong, M. Xu, Z. Sun, T. Tu, J. Org. Chem. ,2013, 78, 7436-7444; AnExtremely Active Catalyst for the Negishi Cross-Coupling Reaction J. E.Milne, S. L. Buchwald, J. Am. Chem. Soc. ,2004, 126 , 13028-13032; One-PotNegishi Cross-Coupling Reactions of In Situ Generated Zinc Reagents with ArylChlorides, Bromides, and Triflates S. Sase, M. Jaric, A. Metzger, V.Malakhov, P. Knochel, J. Org. Chem. ,2008, 73 , 7380-7382; Efficient NegishiCoupling Reactions of Aryl Chlorides Catalyzed by Binuclear and MononuclearNickel-N-Heterocyclic Carbene Complexes Z. Xi, Y. Zhou, W. Chen, J. Org. Chem. ,2008, 73 , 8497-8501; Cross-Coupling of Aryltrimethylammonium Iodideswith Arylzinc Reagents Catalyzed by Amido Pincer Nickel Complexes X.-Q.Zhang, Z.-X. Wang, J. Org. Chem. ,2012, 77 , 3658-3663; Efficient Cross-Couplingof Aryl Chlorides with Arylzinc Reagents Catalyzed by Amido Pincer Complexesof Nickel L. Wang, Z.-X. Wang, Org. Lett. ,2007, 9 , 4335-4338; Highly Regio- andStereoselective Synthesis of ( Z)-Trisubstituted Alkenes via PropyneBromoboration and Tandem Pd-Catalyzed Cross-Coupling C. Wang, T. Tobrman, Z.Xu, E.-i. Negishi, Org. Lett. ,2009, 11 , 4092-4095; Highly RegioselectiveSynthesis of Trisubstituted Allenes via Lithiation of 1-Aryl-3-alkylpropadiene, Subsequent Transmetalation, and Pd-Catalyzed NegishiCoupling Reaction J. Zhao, Y. Liu, S. Ma, Org. Lett. ,2008, 10 , 1521-1523; HighTemperature Metalation of Functionalized Aromatics and Heteroaromatics using(tmp)2Zn·2MgCl2·2LiCl and Microwave Irradiation S. Wunderlich, P. Knochel, Org. Lett. ,2008, 10 , 4705-4707; A Mild Negishi Cross-Coupling of 2-Heterocyclic Organozinc Reagents and Aryl Chlorides M. R. Luzung, J. S.Patel, J. Yin, J. Org. Chem. ,2010, 75 , 8330-8332; Synthesis of SubstitutedCyclopropanecarboxylates via Room Temperature Palladium-Catalyzed α-Arylationof Reformatsky Reagents S. N. Greszler, G. T. Halvorsen, E. A. Voight, Org. Lett. ,2017, 19, 2490-2493; and Enantioselective, Palladium-Catalyzed α-Arylation of N -Boc-pyrrolidine KR Campos, A. Klapars, JH Waldman, PGDormer, C.-Y. Chen, J. Am. Chem. Soc. ,2006, 128 , 3538-3539.

[0017] Arylzinc can be prepared using mild reaction conditions via Grignard or organolithium intermediates with metallic zinc (e.g., ZnCl2 or ZnBr2). See, for example, Negishi Cross-Coupling Reactions, Diana Haas, Jeffrey M. Hammann, Robert Greiner, Paul Knochel. ACS Catal.2016, V6(3) p1540-1552. Giovannini R, Knochel P (1998). "Ni(II)-Catalyzed Cross-Coupling between Polyfunctional Arylzinc Derivatives and Primary Alkyl Iodides”. Journal of the American Chemical Society. 120 (43): 11186-11187. doi:10.1021 / ja982520o Jie Jack Li, Chapter 3 - Applications of Palladium Chemistry to the Total Synthesis of Naturally Occurring of Indole Alkaloids in “Alkaloids: Chemical and Biological Perspectives” 14:437-503 (1999). In some cases, organozinc compounds can be prepared directly by reacting with ZnCl2. (SP Nolan and O. Navarro, 11.01-CC Bond Formation by Cross-coupling in “Comprehensive Organometallic Chemistry III” 11:1-37 (2007)).

[0018] The term "under Negishi conditions" refers to a transition metal-catalyzed cross-coupling reaction involving carbon-carbon bond formation between organohalides and organozinc compounds. "Under Negishi conditions" also includes the formation of organozinc compounds, for example, through the reaction of zinc halides with Grignard reagents or organolithium intermediates.

[0019] In one aspect, i) the first starting material is converted into an organozinc intermediate represented by formula (II-B): .

[0020] The organozinc intermediate reacts with a second starting material in the presence of a palladium catalyst to form a compound of formula (I). X is Cl, Br, or I. Alternatively, X in the organozinc intermediate (formula (II-B)) is Cl; and Y in the second starting material (formula II) is Br. Solvents suitable for this reaction include ether solvents such as tetrahydrofuran, methyltetrahydrofuran, anisole, and mixtures thereof. The organozinc intermediate typically reacts with the second starting material without isolating the organozinc intermediate.

[0021] In one aspect, a solution of an alkoxide or amine base in the ether solvent is bound to an organozinc intermediate prior to reaction with the second starting material. Adding a base to the reaction mixture has the advantage of reducing byproduct formation. Examples of suitable bases include potassium tert-butoxide (KO42-K). t Bu), morpholine, piperazine, benzylpiperazine, NH3, NH4Cl, and hexamethyldisilazane. KO is commonly used. t Bu. In one aspect, the base content is between 0.5 and 3.0 equivalents relative to the first starting material. In another aspect, the base content is between 1.5 and 3.0 equivalents relative to the first starting material. Methyltetrahydrofuran is a commonly used ether solvent.

[0022] In another aspect, the reaction of the organozinc intermediate with the second starting material in polar aprotic solvents such as... N The procedure is carried out in the presence of 2-methyl-2-pyrrolidone, dimethylformamide, or dimethyl sulfoxide. Typically, the following methods are used: N 2-Methyl-2-pyrrolidone. In one respect, 0.05 to 1.5 volumes or mL of a polar aprotic solvent is used per gram of starting material.

[0023] In another aspect, after the compound of formula (I) is formed, using N -acetyl- L - An alkaline aqueous solution of cysteine ​​is used to extract the reaction mixture containing an organozinc intermediate and a second starting material from the reaction product. N -acetyl- L - The concentration of cysteine ​​solution is typically less than 1 g / 5 mL water. "Extraction" of the reaction mixture refers to direct application of... N -acetyl- L The reaction mixture is washed with a cysteine ​​solution to form an aqueous and an organic phase. The organic phase containing compound 1 is then separated from the aqueous phase. Alternatively, "extraction" refers to quenching the reaction mixture with an aqueous solution to form an aqueous and an organic phase. The organic phase containing compound 1 is then separated from the aqueous phase, followed by... N-acetyl- L - Cysteine ​​solution was used to extract the aqueous phase. N -acetyl- L - Cysteine ​​solution extraction has the advantage of reducing residual palladium in the final reaction product (compound 1).

[0024] In another aspect, by mixing the first starting material with Grignard reagent R 1 The MgX2 reaction yields an organometallic intermediate by forming an organometallic intermediate represented by formula (II-A): .

[0025] The organometallic intermediate then reacts with ZnX2 to form an organozinc intermediate. R' is a C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, phenyl, benzyl, or monocyclic heteroaryl; the phenyl, benzyl, or heteroaryl group is optionally and independently substituted by one or more groups selected from halogens, C1-C3 alkyl, and C1-C3 alkoxy groups; and X... 2 It can be Cl, Br, or I. In one respect, the Grignard reagent is isopropyl magnesium chloride (Cl, Br, or I). i -PrMgCl). Conveniently, the organometallic intermediate reacts with ZnX2 without separating the organometallic intermediate.

[0026] The reaction of the first starting material with the Grignard reagent can be carried out in an ether solvent. A commonly used ether solvent is tetrahydrofuran. In one aspect, the reaction of the first starting material with the Grignard reagent is carried out in a mixture containing anisole and an ether solvent. The use of anisole in the reaction mixture has the advantage of reducing byproducts. In another aspect, the reaction of the first starting material with the Grignard reagent is carried out in a mixture containing aromatic solvents such as benzene, toluene, xylene, and mixtures thereof.

[0027] Specific conditions for preparing compound 1 by the method of this disclosure are provided in Examples 1 and 5. Compound 1 can be readily converted into an ALK-2 inhibitor by first removing the amine protecting group and then carbamylated the resulting free amine to the desired ALK-2 inhibitor. Conditions suitable for both conversions are disclosed in U.S. Patent No. 10,233,186. Specific conditions for removing the Boc protecting group are provided in Example 2 below; and specific conditions for carbamylation are provided in Example 3.

[0028] The following examples are intended to be illustrative and not to limit the scope of this disclosure in any way.

[0029] Example Example 1 Preparation of tert-butyl 4-(6-(5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridin-2-yl)pyrrolo[1,2-b]pyridazin-4-yl)piperazine-1-carboxylic acid 1.1 Preparation of 2-bromo-5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridine (compound 2) Compound 2 was prepared from the starting materials 1-isopropylpiperidin-4-one and 2-bromo-5-iodopyridine via the synthetic route shown above. It is also available from Acceledev.

[0030] 1.2 Preparation of tert-butyl 4-(6-bromopyrrolo[1,2-b]pyridazine-4-yl)piperazine-1-carboxylate (compound 3) A mixture of 6-bromopyrrolo[1,2-b]pyridazin-4-ol (5.5 kg, 25.8 mol) and triethylamine (3.1 kg, 1.2 equivalents) in acetonitrile (27 L, 4.9 V) was stirred at -10 °C. Trifluoromethanesulfonic anhydride (7.1 kg, 0.98 equivalents) was added to the mixture, followed by rinsing with acetonitrile (2 L, 0.36 V). The reaction was stirred until complete, at which point trimethylsilyl chloride (0.3 kg, 0.1 equivalents) was added. Then, triethylamine (3.7 kg, 1.3 equivalents) and N-Boc-piperazine (5.5 kg, 1.2 equivalents) were added to the mixture, followed by rinsing with acetonitrile (2 L, 0.36 V). The reaction mixture was heated to 65–75 °C until complete. The reaction mixture was concentrated at 45–55 °C and diluted with water, then cooled to 15–25 °C to allow the product to crystallize. The product was filtered and washed with isopropanol (2 × 11 L, 2 × 2 volumes) to give 7.0 kg (72.4% yield).

[0031] 1.3 4-(6-(5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridin-2-yl)pyrrolo[1,2-b]pyridazine- Preparation of 4-yl)piperazine-1-carboxylic acid tert-butyl ester (compound 1) 2-Bromo-5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridine (compound 2, 5.9 kg, prepared as disclosed in US 10233186) was dissolved in anisole (24 L). The resulting solution was heated to 90-100 °C and partially distilled to reduce the water content. The remaining reaction solution was cooled to 45-55 °C and 9.6 kg of isopropyl magnesium chloride (20% tetrahydrofuran solution) was added. Once complete conversion was observed, 10.7 kg of zinc chloride solution (25% in methyltetrahydrofuran) was added while heating continued. Potassium tert-butoxide (25% methyltetrahydrofuran solution, 17.6 kg), Pd2(dba)3 (18 g), and... were then added to the resulting organozinc (intermediate 1) solution. tert -Bu3P•HBF4 (23g). Additionally, add... N0.6 L of methyl-2-pyrrolidone was added, followed by the addition of tert-butyl 4-(6-bromopyrrolo[1,2-b]pyridazin-4-yl)piperazine-1-carboxylate (compound 3, prepared as disclosed in US 10233186) as a solution in tetrahydrofuran (9 L of tetrahydrofuran solution of 6.0 Kg of compound 3). Heating continued until complete conversion to compound 1.

[0032] Example 2 Preparation of 6-(5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridin-2-yl)-4-(piperazin-1-yl)pyrrolo[1,2-b]pyridazine (compound 4) Compound 1, prepared as described in Example 1, was used without purification or separation from the reaction mixture. The reaction mixture was diluted with tetrahydrofuran (8.8 kg) and a solution of 33% hydrochloric acid (21 kg) in water (36 kg) was added. The acidic aqueous mixture containing the product was washed with methyltetrahydrofuran (31 kg), followed by washing with isopropyl acetate (2 × 11 kg). Subsequently, the aqueous solution was diluted with isopropyl acetate (53 kg) and alkalized with ammonia (25%, 33 kg). The organic phase was separated and washed with acetylcysteine ​​(3 × 26 kg) and water (2 × 18 kg). The organic solution was inoculated and heptane (41.7 kg) was added to crystallize the product, which was then separated by filtration and dried to give approximately 3.6 kg of compound 4.

[0033] Example 3: Preparation of ALK-2 inhibitor from compound 4 Add 1,1-carbonyldiimidazole (1.51 kg), isopropyl acetate (6.4 kg), and alcohol R-OH (e.g., 1.1 equivalents relative to 1,1-carbonyldiimidazole) to the reactor. Stir the reaction at 20-30°C for 30 minutes until the reaction is complete. Heat the reaction to 30-40°C and filter, washing the filter with isopropyl acetate (7.7 kg). Add ammonia (25%, 3.2 kg) and compound 4 (3.5 kg) to the diluted mixture. Heat the reaction to 50-60°C and distill under vacuum. Further dilute the mixture with isopropyl acetate (6.1 kg) and confirm the reaction is complete. At this point, dilute the reaction mixture with water (3.5 kg) and isopropyl acetate (36.9 kg) and stir. Allow the mixture to settle and separate the organic phase. Further wash the organic solution with water (5 × 7 kg). Dilute the finally separated organic phase with isopropyl acetate (7.7 kg) and distill under vacuum at 50-60°C to reduce the water content. The organic solvent can then be removed to isolate the ALK-2 inhibitor.

[0034] Example 4: N-acetylcysteine ​​was significantly more effective than potassium carbonate and 2,4,6-trithio-1,3,5-triazine (TMT) in removing palladium from the reaction in Example 1. Six volumes of toluene were added to 1.15 equivalents of 2-bromo-5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridine (compound 2), and the mixture was heated to a jacket temperature (JT) of 145 °C. 1 Four volumes of toluene were distilled at an internal temperature (IT) of 112-121°C. At IT 45°C, a total of 1.37 equivalents of isopropyl magnesium chloride (2M in tetrahydrofuran) was added to complete the reaction. At this point, 1.20 equivalents of ZnCl2 (2M in tetrahydrofuran) were added at 45°C, and the mixture was stirred at JT 80°C for 14 hours. At IT 45°C, 0.1 volume of... N 1-Methyl-2-pyrrolidone, 1 mol% Pd2(dba)3, 4 mol% t Bu3P•HBF4. Add 1.0 equivalent of compound 3 (30.4 g) in 2.5 volumes of methyltetrahydrofuran (MeTHF) solution over 30 minutes at 45°C. After 1 hour, add 0.15 equivalents of compound 3 in 0.4 volumes of tetrahydrofuran solution. Stir the mixture at 45°C for 2 hours, transfer to another reaction vessel, rinse with 1.6 volumes of MeTHF, and then add it to a solution of 4.1 equivalents of K2CO3 in 25 volumes of water over 10 minutes at 24°C. Then add 0.43 volumes of 30%-w / w NaOH. Separate the aqueous phase and divide the organic phase into three portions. Each portion is treated with 2 × 1.6 volumes of (i) potassium carbonate, (ii) 2,4,6-trimercapto-1,3,5-triazine (TMT), or (iii) N Wash with acetylcysteine. Then add 3.3 volumes of water and 0.95 volumes of 2M HCl and separate the organic phase. Subsequently add 0.30 volumes of 30%-w / w NaOH and Norit CGP super (approximately 0.5 g). Stir the mixture at IT 45°C for 2 hours, filter, and wash with 0.33 volumes of MeTHF. Wash the organic phase with 2 × 1 volumes of water. Add Boc₂O (0.08 volumes, 2M) and stir the mixture at 24°C for 15 minutes. Distill the MeTHF at JT 80-120°C while adding n-heptane (3 × 1.6 volumes). Cool the brown slurry to 0°C, stir for 15 minutes, filter, and wash with 2 × 0.7 volumes of n-heptane (re-wash the slurry).

[0035] The quenched reaction mixture was divided into three portions, and the palladium content, determined by inductively coupled plasma mass spectrometry (IPC-MS), was as follows: reference (K₂CO₃): 1,400 ppm Pd; 2 extractions with TMT: 1,000 ppm Pd; and...N - Acetylcysteine ​​double extraction: 120 ppm Pd.

[0036] Example 5: The product produced by the Negishi method for preparing compound 1 has fewer impurities than that produced by the corresponding Suzuki method. To a container containing a solution of compound 4 (1.0 g) in 2.4 mL (2.4 volumes) of water and 12.0 mL (12 volumes) of 1,4-dioxane, 0.68 g (1.0 equivalent) of 2-bromo-5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridine (compound 2), K₂CO₃ (0.57 g, 2.0 equivalent), and Pd(PPH₃)₄ (0.12 g, 0.05 equivalent) were added. The reaction was heated to 80 °C until the reaction was observed to be complete by HPLC. Figure 1 ).

[0037] To 3.27 g of 2-bromo-5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridine (compound 2), add 6 volumes of toluene and 1.2 equivalents of iPrMgCl (2 M in THF). Heat the mixture to 65 °C. Once the reaction is complete, add 1.3 equivalents of ZnCl2 (1.9 M in MeTHF) and maintain the reaction at 20–25 °C. At 45 °C, add Pdp (containing 3 volumes of THF) to compound 3. t Bu3)2 (0.1 equivalent) and stir the mixture until the reaction is observed to be complete by HPLC. Figure 2 ).

[0038] from Figure 1 and 2 It can be seen that the preparation of compound 1 by the method disclosed herein is cleaner and produces far fewer impurities than the corresponding Suzuki coupling.

Claims

1. A method for preparing a compound represented by formula (I): The method includes reacting a first starting material, represented by formula (II), in a reaction mixture: Reacts with the second starting material represented by formula (III) under Negishi conditions: Compounds of formula (I) are formed, wherein R is an amine protecting group; Y is Cl, Br or I; and Z is Cl, Br, I or trifluoromethanesulfonate.

2. The method according to claim 1, wherein the reaction is mediated by a palladium catalyst.

3. The method according to claim 2, wherein: i) Convert the first starting material into an organozinc intermediate represented by formula (II-B): ； and ii) The organozinc intermediate reacts with the second starting material in the presence of the palladium catalyst to form a compound of formula (I), wherein X is Cl, Br or I.

4. The method according to any one of claims 1-3, wherein X is Cl and Y is Br.

5. The method according to claim 3 or 4, wherein the organozinc intermediate reacts with the second starting material without separating the organozinc intermediate.

6. The process of any one of claims 2-5, wherein the palladium catalyst is selected from Pd(X 1 )2 and Pd(X 1 )2Cl2, wherein each X 1 is independently a phosphine ligand.

7. The method of claim 6, wherein the phosphine ligand is selected from dtbpf, dcypf, dppf, t- BuXPhos, AdBrettPhos, SPhos, RuPhos, XPhos, BrettPhos, JackiePhos, t- BuBrettPhos, TrixiePhos, JohnPhos, t- BuDavePhos, t- BuMePhos, CyJohnPhos, DavePhos, MePhos, PhDavePhos, VPhos, PhCPhos, CPhos, EtCPhos, RockPhos, AlPhos, and t- Bu)PhCPhos.

8. The method according to claim 6, wherein the palladium catalyst is selected from: Pd(dppe)2 (bis[1,2-bis(diphenylphosphine)ethane]palladium(O)), Pd(dba)2 (bis(dibenzylacetone)palladium(O)), CX-11 (1,3-bis(2,6-diisopropylphenyl)imidazolium-2-ylidene(1,4-naphthoquinone)palladium(O) dimer), CX-12 (1,3-bis(2,4,6-trimethylphenyl)imidazolium-2-ylidene(1,4-naphthoquinone)palladium(O) dimer), Pd(t-Bu3P)2 (bis(tri-tert-butylphosphine)palladium(O)), Pd(PCy3)2 (bis(tricyclohexylphosphine)palladium(O)), Pd(PPh3)4 (tetra(triphenylphosphine)dipalladium(O)), Pd2(dba3)3 (tris(dibenzylacetone)palladium(0)), Pd(OAc)2 (palladium(II) acetate), PdCl2(PPh3)2 (dichlorobis(triphenylphosphine)palladium(II)), PdCl2(Amphos)2 (bis(di-tert-butyl(4-dimethylaminophenyl)phosphine)dichloropalladium(II)), Pd(MeCN)2Cl2 (bis(acetonitrile)dichloropalladium(II)), PdCl2(P( o -Tol)3)2 (dichlorobis(tri-o-tolylphosphine)palladium(II)), Pd(dppf)Cl2(1,1'-bis(diphenylphosphine)ferrocene]dichloropalladium(II)), Pd(MeCN)4(BF4)2(tetra(acetonitrile)tetrafluoroboratepalladium(II)), Pd-PEPPSI-IPent(dichloro[1,3-bis(2,6-di-3-pentylphenyl)imidazol-2-ylidene](3-chloropyridinyl)palladium(II)), Pd-PEPPSI-IPr ([1,3-bis(2,6-diisopropylphenyl)imidazol-2-ylidene](3-chloropyridinyl)palladium(II)) and Pd-PEPPSI-SIPr ((1,3-bis(2,6-diisopropylphenyl)imidazoline)(3-chloropyridinyl)palladium(II)).

9. The method according to claim 6, wherein the palladium catalyst is selected from Pd(MeCN)₂Cl₂, Pd[P( o -Tol)3]2Cl2, PdCl2(Amphos)2 and Pd(dba)2.

10. The method according to claim 6, wherein the palladium catalyst is selected from Pd2(dba)3 / P(R 1 )3, Pd(PPh3)4, Pd(PPh3)2Cl2, Pd(MeCN)2Cl2, Pd[P(o-Tol)3]2Cl2, PdCl2(Amphos)2, Pd(P t Bu3)2, Pd(zdppf)Cl2, Pd(dba)2, Pd2(dba)3 and Pd(XPhos), where each R 1 It is a C1-C6 alkyl, C3-C6 cycloalkyl, benzyl or phenyl, and wherein each of the benzyl or phenyl groups is optionally and independently substituted by one or more groups selected from halogen, C1-C3 alkyl and C1-C3 alkoxy.

11. The method according to claim 6, wherein the palladium catalyst is Pd2(dba)3.

12. The method according to claim 6, wherein the palladium catalyst is PdP ( t Bu)3.

13. The method of any one of claims 2-12, wherein the first starting material is reacted with a Grignard reagent R’MgX 2 to form an organometallic intermediate represented by Formula (II-A): and reacting the organometallic intermediate with ZnX2to form the organozinc intermediate, wherein R' is Ci-C6alkyl, Ci-C6alkenyl, Ci-C6alkynyl, phenyl, benzyl, or monocyclic heteroaryl, wherein each of the phenyl, benzyl, or heteroaryl is optionally and independently substituted with one or more groups selected from halogen, Ci-C3alkyl, and Ci-C3alkoxy, and X 2 is CI, Br, or I.

14. The method of claim 13, wherein the Grignard reagent is i -PrMgCl.

15. The method according to claim 13, wherein the organometallic intermediate reacts with ZnX2 without separating the organometallic intermediate.

16. The method according to any one of claims 13-15, wherein the first starting material reacts with the Grignard reagent in a mixture containing anisole.

17. The method of claim 16, wherein the first starting material reacts with the Grignard reagent in a mixture of anisole and an ether solvent.

18. The method of claim 17, wherein the ether solvent is tetrahydrofuran.

19. The method according to any one of claims 3-18, wherein the KO in the ether solvent is removed before reacting with the second starting material. t Bu binds to the organozinc intermediate.

20. The method of claim 19, wherein the organozinc intermediate and KO t Bu combines with tetrahydrofuran.

21. The method according to claim 19 or 20, wherein the reaction of the organozinc intermediate with the second starting material is... N The procedure is carried out in the presence of 2-methyl-2-pyrrolidone.

22. The method according to any one of claims 1-21, further comprising, after forming the compound of formula (I), using N -acetyl- L The reaction mixture was extracted with an alkaline aqueous solution of cysteine.

23. The method according to any one of claims 1-22, wherein R is selected from Fmoc (fluorenyl methyl carbamate), Cbz (benzyl carbamate), Boc (tert-butyl carbamate), acetamide, benzyl, and toluenesulfonyl (p-toluenesulfonamide).

24. The method of claim 23, wherein R is tert-butyloxycarbonyl.

25. The method according to any one of claims 1-24, wherein Z is Br.

26. A compound represented by formula (II), (II-A), or (II-B): , or wherein X and X 2 each independently Cl, Br, or I; and Y is Cl or I.

27. The method according to any one of claims 13-15, wherein the first starting material reacts with the Grignard reagent in a mixture comprising an aromatic solvent selected from benzene, toluene, and xylene.

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