Reaction Steps
To a solution of 21 (crude from the previous step) in dry acetonitrile (50 mL) was added 1,2-phenylenediamine (1.83 g, 16.9 mmol) followed by Et3N (2.65 mL, 19.0 mmol), HOBt.H2O (1.03 g, 7.6 mmol) and EDCI.HCl (1.62 g, 8.5 mmol). The mixture was stirred at room temperature for 72 h, filtered to remove salts and filtrate was concentrated to form a residue, which was purified by flash chromatography on silica gel (MeOH/CH2Cl2: 2/98 to 5/95). Trituration of this material with a mixture of EtOAc/CH2Cl2, allowed affording the title compound 22a (696 mg, 1.3 mmol, 31% yield over 2 steps) as a white solid. 1H NMR: (400 MHz, DMSO-d6) δ (ppm): 9.55 (s, 1H), 8.25 (d, J=5.2 Hz, 1H), 8.00 (d, J=8.4 Hz, 2H), 7.88 (d, J=8.4 Hz, 2H), 7.77 (t, J=6.4 Hz, 1H), 7.44 (d, J=7.2 Hz, 2H), 7.11 (d, J=7.6 Hz, 1H), 7.07 (d, J=5.2 Hz, 1H), 7.01 (d, J=8.4 Hz, 2H), 6.92 (td, J=7.6, 1.6 Hz, 1H), 6.73 (dd, J=8.0, 1.6 Hz, 1H), 6.55 (td, J=7.4, 1.2 Hz, 1H), 4.85 (s, 2H), 4.61 (d, J=5.6 Hz, 2H), 4.13 (t, J=5.6 Hz, 2H), 3.55 (t, J=4.4 Hz, 4H), 2.68 (t, J=5.6 Hz, 2H), 2.45 (t, J=4.4 Hz, 4H).
