Methods of preparing activin receptor-like kinase inhibitors

Abstract

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

Description

[0001] 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:

[0005]

[0006] US Patent No. 10,233,186 discloses the Suzuki reaction for preparing intermediates such as compound 1, as follows:

[0007]

[0008] It involves the coupling of pyrrolopyridazine intermediates with piperidinyl-pyridine compounds. Summary of the Invention

[0009] It has been found that the Suzuki coupling of 6-pyrrolopyridazine and pinacol diboronate 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 preparing compound 1 on an industrial scale using Negishi coupling, a much higher yield than that obtained with Suzuki coupling will be obtained. Based on these results, a novel and improved synthesis of the important intermediate compound 1 is disclosed.

[0010] In one embodiment, this disclosure provides a method for preparing a compound represented by formula (I):

[0011]

[0012] The method includes reacting a first starting material, represented by formula (II), in the reaction mixture:

[0013]

[0014] The second starting material, represented by formula (III), reacts under Negishi conditions:

[0015]

[0016] 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 PGM Watts, “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.

[0017] Another embodiment of this disclosure is a compound represented by formula (II), (II-A) or (II-B):

[0018]

[0019] Where Y, X and X 2Each 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

[0020] 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.

[0021] 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

[0022] 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").

[0023] 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), 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(II) methanesulfonate (AdBrettPhos), 2-dicyclohexylphosphino-2',6'-dimethoxybiphenyl (SPhos), (2-dicyclohexylphosphino-2'... Palladium (II) methanesulfonate (RuPhos), [2-Dicyclohexylphosphino-2',4',6'-triisopropylbiphenyl] (XPhos), [(2-Dicyclohexylphosphino-3,6-dimethoxy-2',4',6'-triisopropyl-1,1'-biphenyl)-2-(2'-amino-1,1'-biphenyl)] methanesulfonate (II) (BrettPhos), [(2-{bis[3,5-bis(trifluoromethyl)phenyl]phosphine}-3,6-dimethoxy-2',4',6'-triisopropyl-1,1'-biphenyl)-2-(2'-amino-1,1'-biphenyl)] methanesulfonate (RuPhos), [2-Dicyclohexylphosphino-3,6-dimethoxy-2',4',6'-triisopropyl-1,1'-biphenyl)-2-(2'-amino ... [2-(2-di-tert-butylphosphino-3,6-dimethoxy-2',4',6'-triisopropyl-1,1'-biphenyl)-2-(2'-amino-1,1'-biphenyl)]palladium(II) methanesulfonate (t-BuBrettPhos), methanesulfonyl(2-(di-tert-butylphosphino)-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), and methanesulfonate [2-diethylphosphino-2',6'-bis(dimethylamino)-1,1-biphenyl](2'-amino-1,1'-biphenyl-2-yl)palladium(II) (EtCPhos) 2-Di(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).

[0024] 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 acetate(II)), PdCl2(PPh3)2(dichlorobis(triphenylphosphine)palladium(II)), PdCl2(Amphos)2(bis(di-tert-butylphosphine) 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)).

[0025] Alternatively, the palladium catalyst is 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)₂. 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 1The palladium catalyst 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 with 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(tBu)3.

[0026] In another embodiment, the palladium catalyst may be combined with a phosphine ligand, for example, the palladium catalyst is Pd2(dba) combined with P(tBu)3.

[0027] 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.

[0028] The organohalides or organotrifluoromethanesulfonates in the Negishi reaction can be alkenyl, aryl, allyl, alkynyl, or propargyl halides or trifluoromethanesulfonates; 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. The conditions for carrying out the Negishi reaction are described, for example, in *Recent Developments in Negishi Cross-Coupling Reactions*. Diana Haas , Jeffrey M. Hammann , Robert Greiner , 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;An Extremely ActiveCatalyst for the Negishi Cross-Coupling Reaction J.E.Milne,S.L.Buchwald,J.Am.Chem.Soc.,2004,126,13028-13032;One-Pot Negishi Cross-Coupling Reactionsof In Situ Generated Zinc Reagents with Aryl Chlorides,Bromides,and TriflatesS.Sase,M.Jaric,A.Metzger,V.Malakhov,P.Knochel,J.Org.Chem.,2008,73,7380-7382;Efficient Negishi Coupling Reactions of Aryl Chlorides Catalyzed by Binuclearand Mononuclear Nickel-N-Heterocyclic Carbene Complexes Z.Xi,Y.Zhou,W.Chen,J.Org.Chem.,2008,73,8497-8501;Cross-Coupling of Aryltri methylammoniumIodides with Arylzinc Reagents Catalyzed by Amido Pincer Nickel Complexes X.-Q.Zhang,Z.-X.Wang,J.Org.Chem.,2012,77,3658-3663;Efficient Cross-Coupling ofAryl Chlor ides with Arylzinc Reagents Catalyzed by Amido Pincer Complexe sof 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 Cro ss-Coupling C.Wang,T.Tobrman,Z.Xu,E.-i.Negishi,Org.Let t.,2009,11,4092-4095;Highly Regioselective Synthesis ofTrisub stituted Allenes via Lithiation of 1-Aryl-3-alkylpropadiene,Subsequent Transmetalation,and Pd-Catalyzed Negishi Coupling Reaction J.Zhao,Y.Liu,S.Ma,Org.Lett.,2008,10,1521-1523;High Te mperature Metalation ofFunctionalized Aromatics and Heteroaroma tics using(tmp)2Zn·2MgCl2·2LiCl andMicrowave Irradiation S.Wunderlich,P.Knochel,Org.Lett.,2008,10,4705-4707;AMild Negishi Cross-Coupling of 2-Heterocyclic Organozinc Reagents and ArylChlorides M.R.Luzung,J.S.Patel,J.Yin,J.Org.Chem.,2010,75,8330-8332;Synthesisof Substituted Cyclopropanecarboxy lates via Room Temperature Palladium-Catalyzedα-Arylation of Re formatsky Reagents S.N.Greszler,G.T.Halvorsen,E.A.Voight,Org.Lett.,2017,19,2490-2493; and Enantioselective,Palladium-Catalyzedα-Arylation of N-Boc-pyrrolidine KRCampos,A.Kla pars,JHWaldman,PGDormer,C.-Y.Chen,J.Am.Chem.Soc.,2006,128,3538-3539. .

[0029] Aryl zinc 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 JackLi,Chapter 3-Applications of Palladium Chemistry to the Total Synthesis ofNaturally 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. (SPNolan and O.Navarro, 11.01-CC Bond Formation by Cross-coupling in "Comprehensive Organometallic Chemistry III" 11:1-37 (2007)).

[0030] 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.

[0031] In one aspect, i) the first starting material is converted into an organozinc intermediate represented by formula (II-B):

[0032]

[0033] 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.

[0034] In one aspect, a solution of an alkoxide or amine base in the ether solvent is combined with 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 (KOtBu), morpholine, piperazine, benzylpiperazine, NH3, NH4Cl, and hexamethyldisilazane. KOtBu is commonly used. In one aspect, the amount of base is between 0.5 and 3.0 equivalents relative to the first starting material. In another aspect, the amount of base is between 1.5 and 3.0 equivalents relative to the first starting material. Methyltetrahydrofuran is a commonly used ether solvent.

[0035] In another aspect, the reaction of the organozinc intermediate with the second starting material is carried out in the presence of a polar aprotic solvent such as N-methyl-2-pyrrolidone, dimethylformamide, or dimethyl sulfoxide. N-methyl-2-pyrrolidone is typically used. In one aspect, 0.05 to 1.5 volumes or mL of the polar aprotic solvent are used per gram of starting material.

[0036] In another aspect, after the formation of the compound of formula (I), the reaction mixture containing the organozinc intermediate and the second starting material is extracted with an alkaline aqueous solution of N-acetyl-L-cysteine. The concentration of the N-acetyl-L-cysteine ​​solution is typically less than 1 g / 5 mL of water. “Extraction” of the reaction mixture refers to directly washing the reaction mixture with the N-acetyl-L-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, and the aqueous phase is then extracted with the N-acetyl-L-cysteine ​​solution. Extraction with the N-acetyl-L-cysteine ​​solution has the advantage of reducing residual palladium in the final reaction product (compound 1).

[0037] In another aspect, by reacting the first starting material with the Grignard reagent R 1 The MgX2 reaction yields an organometallic intermediate by forming an organometallic intermediate represented by formula (II-A):

[0038]

[0039] 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 The reagent can be Cl, Br, or I. In one respect, the Grignard reagent is isopropyl magnesium chloride (i-PrMgCl). Conveniently, the organometallic intermediate reacts with ZnX2 without isolating the organometallic intermediate.

[0040] 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.

[0041] 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.

[0042] The following examples are intended to be illustrative and not to limit the scope of this disclosure in any way.

[0043] Example

[0044] 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

[0045]

[0046] 1.1 Preparation of 2-bromo-5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridine (compound 2)

[0047] 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.

[0048] 1.2 Preparation of tert-butyl 4-(6-bromopyrrolo[1,2-b]pyridazin-4-yl)piperazine-1-carboxylate (compound 3)

[0049] 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). 1.3 Preparation of 4-(6-(5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridin-2-yl)pyrrolo[1,2-b]pyridazine-4-yl)piperazine-1-carboxylic acid tert-butyl ester (compound 1)

[0050] 2-Bromo-5-(4-ethoxy-1-isopropylpiperidin-4-yl)pyridine (compound 2, 5.9 kg, prepared as disclosed in US10233186) 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 tert-Bu3P·HBF4 (23 g) were then added to the resulting organozinc (intermediate 1) solution. In addition, N-methyl-2-pyrrolidone (0.6 L) was added, followed by 4-(6-bromopyrrolo[1,2-b]pyridazin-4-yl)piperazine-1-carboxylic acid tert-butyl ester (compound 3, prepared as disclosed in US10233186) 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.

[0051] 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)

[0052]

[0053] 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.

[0054] Example 3: Preparation of ALK-2 inhibitor from compound 4

[0055]

[0056] 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.

[0057] 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.

[0058] 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. 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 isopropylmagnesium chloride (2 M in tetrahydrofuran) was added to complete the reaction. At this point, 1.20 equivalents of ZnCl2 (2 M 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-methyl-2-pyrrolidone, 1 mol% of Pd2(dba)3, and 4 mol% of tBu3P·HBF4 were added. Add 2.5 volumes of methyltetrahydrofuran (MeTHF) solution containing 1.0 equivalent of compound 3 (30.4 g) over 30 minutes at 45 °C. After 1 hour, add 0.4 volumes of tetrahydrofuran solution containing 0.15 equivalents of compound 3. Stir the mixture at 45 °C for 2 hours, transfer it to another reaction vessel, wash 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 fractions. Each fraction is washed with 2 × 1.6 volumes of (i) potassium carbonate, (ii) 2,4,6-trimercapto-1,3,5-triazine (TMT), or (iii) N-acetylcysteine. Then add 3.3 volumes of water and 0.95 volumes of 2M HCl and separate the organic phase. Subsequently, 0.30 volumes of 30% w / w NaOH and Norit CGP super (approximately 0.5 g) were added. The mixture was stirred at IT 45°C for 2 hours, filtered, and washed with 0.33 volumes of MeTHF. The organic phase was washed with 2 × 1 volumes of water. Boc₂O (0.08 volumes, 2 M) was added, and the mixture was stirred at 24°C for 15 minutes. MeTHF was distilled at JT 80–120°C while n-heptane (3 × 1.6 volumes) was added. The brown slurry was cooled to 0°C, stirred for 15 minutes, filtered, and washed with 2 × 0.7 volumes of n-heptane (then washed with the slurry).

[0059] The quenched reaction mixture was divided into three portions, and the palladium content was determined by inductively coupled plasma mass spectrometry (IPC-MS) as follows: reference (K2CO3): 1,400 ppm Pd; twice extracted with TMT: 1,000 ppm Pd; and twice extracted with N-acetylcysteine: 120 ppm Pd.

[0060] Example 5: The product produced by the Negishi method for preparing compound 1 had fewer impurities than the corresponding Suzuki method.

[0061]

[0062] 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 ).

[0063] 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 0.1 equivalents of Pdp(tBu3)2 with 3 volumes of THF to compound 3 and stir the mixture until the reaction is observed to be complete by HPLC. Figure 2 ).

[0064] 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 selected from Fmoc, Cbz, Boc, acetamide, benzyl, and toluenesulfonyl; Y is Br; and Z is Br, wherein: i) Convert the first starting material of formula (II) into an organozinc intermediate represented by formula (II-B): By reacting the first starting material of formula (II) with the Grignard reagent R'MgX 2 The mixture of anisole and tetrahydrofuran is reacted to form an organometallic intermediate represented by formula (II-A): Furthermore, the organometallic intermediate of formula (II-A) is reacted with ZnX2 to form the organozinc intermediate of formula (II-B), wherein R' is a C1-C6 alkyl, C1-C6 alkenyl, C1-C6 alkynyl, phenyl, benzyl, or monocyclic heteroaryl, wherein each of the phenyl, benzyl, or monocyclic heteroaryl groups is optionally and independently substituted by one or more groups selected from halogens, C1-C3 alkyl, and C1-C3 alkoxy groups, and X... 2 For Cl, Br, or I: and ii) The organozinc intermediate of formula (II-B) reacts with the second starting material of formula (III) in the presence of a palladium catalyst to form a compound of formula (I), wherein X is Cl, and wherein the palladium catalyst is Pd2(dba)3 or PdP( t Bu)3, Prior to reacting with the second starting material of formula (III), the KO in tetrahydrofuran t Bu combines with the organozinc intermediate of formula (II-B).

2. The method according to claim 1, wherein the organozinc intermediate of formula (II-B) reacts with the second starting material of formula (III) without separating the organozinc intermediate of formula (II-B).

3. The method according to claim 1, wherein the Grignard reagent is i -PrMgCl.

4. The method according to claim 1, wherein the organometallic intermediate of formula (II-A) reacts with ZnX2 without separating the organometallic intermediate of formula (II-A).

5. The method according to claim 1, wherein the reaction of the organozinc intermediate of formula (II-B) with the second starting material of formula (III) is in N The procedure is carried out in the presence of 2-methyl-2-pyrrolidone.

6. The method according to claim 1, 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.

7. The method according to claim 1, wherein R is tert-butyloxycarbonyl.

8. A compound represented by formula (II-A) or (II-B): or Where X and X 2 Each is independently represented by Cl.

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