Reaction Steps
H2O2 (70%, 1.25 mL, ca. 25.8 mmol) was added dropwise to a stirred solution of TFAA (3.6 mL, 25.8 mmol) in DCM (35 mL) at 0° C. The solution was stirred at 20° C. for 10 min, then cooled to 0° C., added to a solution of 1-oxide 48 (0.85 g, 2.58 mmol) and TFA (0.43 mL, 5.50 mmol) in CHCl3 (35 mL) at 0° C. The solution was stirred at 20° C. for 5 h, diluted with dilute aqueous NH3 solution until basic and extracted with CHCl3 (4×60 mL). The combined organic fraction was dried and the solvent evaporated. The residue was purified by chromatography, eluting with a gradient (3-6%) of MeOH/DCM, to give 1,4-dioxide 49 (0.37 g, 42%) as a red gum: 1H NMR δ 8.13 (s, 1H, H-9), 8.10 (s, 1H, H-5), 7.45 (br s, 1H, NH), 3.82 (t, J=6.1 Hz, 2H, CH2O), 3.74 (t, J=4.6 Hz, 2H, CH2O), 3.54 (q, J=5.7 Hz, 2H, NCH2), 2.97-3.04 (m, 4H, H-6, H-8), 2.73-2.80 (m, 6H, CH2), 2.15 (p, J=7.4 Hz, 2H, H-7), 1.91 (p, J=5.9 Hz, 2H, CH2); 13C NMR δ 158.7, 154.6, 148.8, 143.3, 129.8, 120.5, 114.7, 69.3, 68.7, 57.4, 55.8, 53.6, 38.7, 33.1, 32.3, 29.9, 25.7; HRMS (FAB+) calcd for C17H24N5O3 (MH+) m/z 346.1879, found 346.1877.
