Reaction Steps
To a solution of 3-benzyl-5-(4-methoxyphenyl)pyrazin-2-amine (12) (synthesized by the process of M. Adamczyk, et al., Org. Prep. Proced. Int., 33, 477-485 (2001)) (500 mg, 1.72 mmol) in pyridine (5 mL) were successively added 4-(dimethylamino)pyridine (21.0 mg, 172 μmol) and 4-methoxybenzoyl chloride (17) (587 mg, 3.44 mmol) at room temperature, and the mixture was heated with stirring at 50° C. for 17 hours. After cooling to room temperature, to the mixture was added water and the product was extracted with dichloromethane (×3). The combined organic extract was dried over anhydrous sodium sulfate, filtered and concentrated under reduced pressure. The residual pyridine was azeotropically removed with toluene (×3). The residue was purified by column chromatography (silica gel 50g, dichloromethane/ethyl acetate=9/1). The residue was further recrystallized from ethyl acetate to give Compound 11x (592 mg, 1.39 mmol, 80.8%) as a colorless solid. Rf=0.63 (dichloromethane/ethyl acetate=9/1); 1H NMR (400 MHz, DMSO-d6) δ 3.83 (s, 3H), 3.85 (s, 3H), 4.17 (s, 2H), 7.04-7.11 (m, 4H), 7.14-7.26 (m, 5H), 7.93-7.98 (AA′BB′, 2H), 8.05-8.11 (AA′BB′, 2H), 8.96 (s, 1H), 10.63 (s, 1H); 13C NMR (67.8 MHz, DMSO+CDCl3) δ 40.3, 54.7, 54.8, 112.9 (2C), 113.7 (2C), 125.4, 125.7, 127.4 (2C), 127.7 (2C), 128.0, 128.5 (2C), 129.4 (2C), 136.2, 137.6, 143.6, 148.2, 150.4, 160.1, 162.0, 165.5; IR (KBr, cm−1) 700, 743, 843, 1030, 1159, 1177, 1258, 1290, 1452, 1485, 1514, 1535, 1580, 1609, 1643, 3242; Anal. Calcd. For C26H23N3O3: C, 73.39; H, 5.45; N, 9.88. Found: C, 73.48; H, 5.40; N, 9.94.
