Reaction Steps
H2O2 (70%, 0.67 mL, ca. 13.3 mmol) was added dropwise to a stirred solution of TFAA (1.9 mL, 13.3 mmol) in DCM (20 mL) at 0° C. The solution was stirred at 0° C. for 5 min, warmed to 20° C. for 10 min, then cooled to 0° C. and added to a stirred solution of 1-oxide 56 (449 mg, 1.3 mmol) and TFA (0.51 mL, 6.6 mmol) in DCM (20 mL) at 0° C. The solution was stirred at 20° C. for 8 h, diluted with dilute aqueous NH3 solution (10 mL) and extracted with DCM (4×50 mL). The combined organic fraction was dried and the solvent evaporated. The residue was purified by chromatography, eluting with a gradient (0-10%) of MeOH/DCM, to give (i) starting material 56 (198 mg, 44%) and (ii) 1,4-dioxide 57 (70 mg, 15%) as a red gum: 1H NMR δ 8.15 (br t, J=5.3 Hz, 1H, NH), 8.12 (s, 1H, H-9), 8.08 (s, 1H, H-5), 3.62-3.68 (m, 2H, CH2N), 3.15-3.23 (m, 2H, CH2N), 3.11 (br t, J=7.5 Hz, 2H, H-6), 3.07 (br t, J=7.5 Hz, 2H, H-8), 2.90-2.95 (m, 1H, CHCN), 2.73 (t, J=6.3 Hz, 2H, CH2N), 2.50-2.61 (m, 2H, CH2N), 2.33-2.43 (m, 1H, CH2), 2.11-2.24 (m, 3H, CH2, H-7), 1.91 (p, J=6.3 Hz, 2H, CH2); 13C NMR δ 155.7, 149.4, 145.7, 138.0, 129.6, 122.0, 115.8, 111.5, 57.3, 53.5, 52.8, 41.0, 33.4, 32.3, 29.1, 26.9, 26.1, 25.3; MS (FAB+) m/z 355 (MH+, 30%), 339 (10); HRMS (FAB+) calcd for C18H23N6O2 (MH+) m/z 355.1883, found 355.1893.
