Reaction Steps
To a stirred solution of 4 (1.30 g, 2.72 mmol) in anhydrous DMF (20 mL) at room temperature under nitrogen were added Et3N (330 μl, 3.26 mmol) and BOP reagent (1.32 g, 2.99 mmol), respectively. After 30 min, a solution of 1,2-phenylenediamine (352 mg, 3.26 mmol), Et3N (1.14 mL, 8.15 mmol) in anhydrous DMF (3 mL) was added dropwise. After 3 h the reaction mixture was poured into saturated aqueous solution of NH4Cl, and extracted with AcOEt. The extract was washed with saturated NH4Cl, water and brine, dried over MgSO4, filtered, concentrated and purified by flash chromatography on silica gel (MeOH/CH2Cl2, 5/95 plus several drops of NH4OH), to afford the title compound 5 (1.49 g, 2.62 mmol, 96% yield) as a yellow sticky foam. 1H NMR (300 MHz, DMSO-d6) δ (ppm): 10.78 (s, 1H), 9.40 (s, 1H), 7.59 (d, J=8.0 Hz, 2H), 7.58 (d, J=15.8 Hz, 1H), 7.45 (d, J=7.9 Hz, 2H), 7.40 (t, J=7.7 Hz, 2H), 7.35 (d, J=8.4 Hz, 1H), 7.14 (s, 1H), 7.07 (t, J=7.5 Hz, 1H), 7.05-6.85 (m, 3H), 6.79 (d, J=7.9 Hz, 1H), 6.62 (t, J=7.5 Hz, 1H), 4.98 (bs, 2H), 3.80 (s, 2H), 3.71 (t, J=6.2 Hz, 2H), 2.95-2.75 (m, 4H), 2.71 (t, J=6.2 Hz, 2H), 0.89 (s, 9H), 0.05 (s, 6H).
