Example 11
Step a: To a stirred suspension of 2,4-dichloro-6-methyl-3-nitropyridine (2.5 g, 12 mmol) in 24 mL of THE was added a solution of 7N NH3 in MeOH (14 mL, 98 mmol). After stirring for 3 h, the volatiles were removed in vacuo. The crude residue was purified by silica gel column chromatography to give 2-chloro-6-methyl-3-nitropyridin-4-amine. C6H7CN3O2 [M+H]+ 188.0, found 188.0.
Step b: To a stirred mixture of 2-chloro-6-methyl-3-nitropyridin-4-amine (760 mg, 4.1 mmol) and Fe (1.1 g, 20 mmol) in a 5:1 solution of EtOH/H2O (24 mL) was added 4.4 mL of conc. HCl. The contents were refluxed for 30 min, then cooled to room temperature and quenched with 100 mL of sat. NaHCO3 (aq). The mixture was extracted with EtOAc and the combined organic layers were dried over MgSO4, filtered, and concentrated in vacuo to yield 2-chloro-6-methylpyridine-3,4-diamine. MS: (ES) m/z calculated for C6H9ClN3 [M+H]+ 158.0, found 158.0.
Step c: To a stirred solution of 2-chloro-6-methylpyridine-3,4-diamine (0.49 g, 3.1 mmol) in 3 mL of EtOH was added a 40% w/w aqueous solution of glyoxal (2.0 mL, 12 mmol). After refluxing for 16 h, the mixture was diluted with H2O and extracted with EtOAc. The organic layers were combined, dried over MgSO4, filtered and concentrated in vacuo. The crude residue was purified by silica gel column chromatography to give 5-chloro-7-methylpyrido[3,4-b]pyrazine. MS: (ES) m/z calculated for C8H7ClN3 [M+H]+ 180.0, found 180.1.
Step d: To a stirred solution of 5-chloro-7-methylpyrido[3,4-b]pyrazine (200 mg, 1.0 mmol) and 2′-chloro-2-methyl-3′-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-[1,1′-biphenyl]-3-amine (350 mg, 1.0 mmol) in 2 mL of MeCN was added AcOH (0.18 mL, 3.1 mmol). After 30 min, the volatiles were concentrated in vacuo. The crude residue was purified by silica gel column chromatography to give N-(2′-chloro-2-methyl-3′-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-[1,1′-biphenyl]-3-yl)-7-methylpyrido[3,4-b]pyrazin-5-amine. MS: (ES) m/z calculated for C27H29BClN4O2 [M+H]+ 487.2, found 487.2.
Step e: To a stirred solution of N-(2′-chloro-2-methyl-3′-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-[1,1′-biphenyl]-3-yl)-7-methylpyrido[3,4-b]pyrazin-5-amine (390 mg, 0.66 mmol), 6-chloro-2-methoxynicotinaldehyde (240 mg, 1.4 mmol), and K3PO4 (490 mg, 2.3 mmol) in a 1:1 solution of 1,4-dioxane/H2O (3.3 mL) under N2 (g) was added Pd(PPh3)4 (76 mg, 0.066 mmol). The mixture was stirred under N2 (g) at 90° C. for 3 h. The mixture was diluted with H2O and then extracted with EtOAc. The combined organic layers were dried over MgSO4, filtered, and concentrated. The crude residue was purified by silica gel column chromatography to give 6-(2-chloro-2′-methyl-3′-((7-methylpyrido[3,4-b]pyrazin-5-yl)amino)-[1,1′-biphenyl]-3-yl)-2-methoxynicotinaldehyde. MS: (ES) m/z calculated for C28H23ClN5O2 [M+H]+ 496.2, found 496.2.
Step f: To a stirred mixture of 6-(2-chloro-2′-methyl-3′-((7-methylpyrido[3,4-b]pyrazin-5-yl)amino)-[1,1′-biphenyl]-3-yl)-2-methoxynicotinaldehyde (120 mg, 0.25 mmol), (S)-5-(aminomethyl)pyrrolidin-2-one hydrochloride (150 mg, 0.99 mmol), and trimethylamine (0.14 mL, 0.99 mmol) in a 4:1 solution of DCM/MeOH (5 mL) was added NaBH(OAc)3 (530 mg, 2.5 mmol). After stirring for 30 min, the mixture was filtered through Celite, and the filtrate was concentrated in vacuo. The product was purified by preparative HPLC to give the product (S)-5-((((6-(2-chloro-2′-methyl-3′-((7-methylpyrido[3,4-b]pyrazin-5-yl)amino)-[1,1′-biphenyl]-3-yl)-2-hydroxypyridin-3-yl)methyl)amino)methyl)pyrrolidin-2-one. 1H NMR (400 MHz, DMSO-d6) δ 12.59 (s, 1H), 9.32 (s, 1H), 9.07 (d, J=2.0 Hz, 1H), 8.86 (d, J=2.0 Hz, 1H), 8.23 (d, J=8.7 Hz, 1H), 7.76 (d, J=7.0 Hz, 1H), 7.62 (s, 1H), 7.55 (d, J=7.5 Hz, 1H), 7.50-7.43 (m, 1H), 7.35 (dd, J=7.9, 7.9 Hz, 1H), 7.12 (s, 1H), 6.96 (d, J=7.5 Hz, 1H), 6.55 (s, 2H), 6.43 (d, J=7.1 Hz, 1H), 4.07 (s, 3H), 3.95-3.84 (m, 1H), 2.48 (s, 4H), 2.26-2.15 (m, 3H), 2.11 (s, 3H), 1.86-1.70 (m, 1H). MS: (ES) m/z calculated for C32H31ClN7O2 [M+H]+ 580.2, found 580.1.
