Reaction Steps
To a stirred suspension of 3 (0.43 g, 1 mmol) in 1,2,3-trimethoxybenzene (5 mL), TFA (10 mL, dropwsie) was added. The reaction mixture was heated at 60° C. for 3 h. TFA was evaporated on rotary evaporator after the disappearance of starting material (TLC) and excess of sodium bicarbonate was added. The reaction mixture was extracted with EtOAc (30×3 mL), washed with brine, dried (anhyd. Na2SO4) and adsorbed over silica and purified through column chromatography to afford 14 as yellowish white solid (0.38 g, 80%); mp: decomposed >225° C. IR: 1734 (C═O str.), 1620, 1514, 1247 (C—O str.) cm−1. 1H NMR (400 MHz, d6-DMSO): δ=3.52 (s, 3H, OCH3), 3.69 (s, 6H, OCH3), 4.60 (dd, J=15.1, 18.3 Hz, 2H, CH2), 5.80 (J=8.7 Hz, 1H, Ar—H), 6.50 (J=8.7 Hz, 1H, Ar—H), 6.85 (d, J=8.7 Hz, 2H, Ar—H), 7.22 (d, J=8.7 Hz, 2H, Ar—H), 7.50 (s, 1H, Ar—CH═N—), 7:85 (s, 1H, Imid-H), 9.40 (brs, 1H, D2O-exchangable NH). 13C NMR (100 MHz, d6-DMSO): δ=42.9, 55.6, 56.3, 60.7, 60.8, 63.4, 106.7, 114.2, 120.0, 122.0, 122.8, 129.1, 129.9, 134.9, 137.2, 142.0, 146.0, 152.6, 154.2, 154.7, 156.6, 159.1. HRMS (FAB) Calcd for C24H24N6O5, 476.1808 (M+); observed m/z 477.1875 (M+H)+.
