Reaction Steps
Under an argon atmosphere, to a mixture of 5-[4-(tert-butyldimethylsilyloxy)phenyl]-3-[4-(dimethylamino)phenyl]pyrazin-2-amine (7n) (315 mg, 749 μmol) and 4-(dimethylamino)pyridine (14.8 mg, 121 μmol) dissolved in anhydrous pyridine (15 mL) was added 2-[4-(tert-butyl dimethylsilyloxy)phenyl]acetyl chloride (10) prepared above at 0° C. and the mixture was hetated with stirring at 50° C. for 20 hours. After cooling to room temperature, to this was added water and the product was extracted with ethyl acetate (100 mL×3). The combined organic extract was washed successively with water (200 mL) and brine (200 mL), followed by drying over anhydrous sodium sulfate. After filtration and concentration under reduced pressure, the residue was purified by column chromatography (silica gel 50 g, n-hexane/ethyl acetate=2/1) to give Compound 11n (200 mg, 300 μmol, 40.0%) as a yellow solid. Rf=0.26 (n-hexane/ethyl acetate=2/1); 1H NMR (400 MHz, DMSO-d6) δ 0.17 (s, 6H), 0.23 (s, 6H), 0.95 (s, 9H), 0.97 (s, 9H), 2.95 (s, 6H), 3.50 (s, 2H), 6.52-6.65 (AA′BB′, 2H), 6.75-6.85 (AA′BB′, 2H), 6.95-7.05 (AA′BB′, 2H), 7.10-7.20 (AA′BB′, 2H), 7.56-7.66 (AA′BB′, 2H), 8.04-8.10 (AA′BB′, 2H), 8.82 (s, 1H), 10.41 (s, 1H); 13C NMR (67.8 MHz, DMSO-d6) δ −4.5 (2C), −4.6 (2C), 17.9, 18.0, 25.5 (6C), 39.8 (2C), 41.8, 111.3 (2C), 119.5 (2C), 120.3 (2C), 124.4, 128.05, 128.07 (2C), 128.9 (2C), 129.2, 130.4 (2C), 135.8, 142.0, 147.78, 147.84, 150.5, 153.8, 156.6, 169.3; IR (KBr, cm−1) 527, 685, 781, 839, 914, 1080, 1167, 1256, 1371, 1441, 1508, 1607, 1668, 2857, 2928, 2955, 3233.
