Reaction Steps
H2O2 (70%, 0.46 mL, 7.7 mmol) was added drop-wise (over 5 min) to a stirred solution of 1-oxide 140 (292 mg, 0.77 mmol), TFA (0.32 mL, 3.9 mmol), and TFAA (1.24 mL, 7.7 mmol) in DCM (25 mL) at 20° C. and the mixture stirred at 20° C. for 17 h. Another aliquot of H2O2 (70%, 0.46 mL, 7.7 mmol) and TFAA (1.24 mL, 7.7 mmol) were added and the mixture was stirred for 1 h. Aqueous NH3 solution (2 M, 30 mL) was added at 0° C. and the mixture stirred at 0° C. for 10 min, then stirred at 20° C. for 20 min. The mixture was extracted with DCM (5×80 mL), the combined organic fraction was dried and the solvent evaporated. The residue was purified by chromatography, eluting with a gradient (0-5%) of MeOH/DCM, to give 1,4-dioxide 141 (169 mg, 61%) as a dull orange solid: mp (MeOH/DCM) 112-114° C.; 1H NMR δ 8.30 (s, 1H, H-9), 8.26 (s, 1H, H-5), 3.73 (d, J=6.4 Hz, 2H, CH2O), 3.45 (br s, 4H, 2×CH2O), 3.21-3.37 (m, 4H, H-8, CH2), 3.00-3.09 (m, 2H, CH2), 2.83-2.92 (m, 1H, H-7), 2.50 (t, J=6.4 Hz, 2H, CH2N), 2.39 (br s, 4H, 2×CH2N), 2.07-2.15 (m, 2H, CH2), OH not observed; 13C NMR [(CD3)2SO] δ 154.1, 153.7, 149.3, 138.7, 133.5, 115.3, 113.3, 66.0 (2), 63.4, 57.2, 53.0 (2), 41.5, 35.6, 35.1, 28.0, 21.0. HRMS (FAB+) calcd for C18H25N4O4 (MH+) m/z 361.1876, found 361.1878.
