Reaction Steps
H2O2 (70%, 0.39 mL, ca. 7.7 mmol) was added dropwise to a stirred solution of TFAA (1.1 mL, 7.7 mmol) in DCM (15 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 28 (253 mg, 0.8 mmol) and TFA (0.30 mL, 3.8 mmol) in DCM (20 mL) at 0° C. The solution was stirred at 5° C. for 4 h, diluted with dilute aqueous NH3 solution (10 mL) and extracted with CHCl3 (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 1,4-dioxide 29 (134 mg, 50%) as a red solid: mp (MeOH/EtOAc) 142-145° C.; 1H NMR δ 8.12 (s, 1H, H-9), 8.10 (s, 1H, H-5), 7.46 (br s, 1H, NH), 3.54-3.60 (m, 2H, CH2N), 3.03-3.11 (m, 4H, H-6, H-8), 2.74 (dd, J=6.1, 5.9 Hz, 2H, CH2N), 2.43-2.47 (m, 4H, 2×CH2N), 2.16-2.24 (m, 2H, H-7), 1.45-1.54 (m, 4H, 2×CH2), 0.91 (t, J=7.4 Hz, 6H, 2×CH3); 13C NMR δ 155.5, 149.5, 145.7, 138.0, 129.6, 115.7, 111.6, 56.0 (2), 52.5, 39.1, 33.4, 32.4, 25.6, 20.4 (2), 11.8 (2). Anal. calcd for C18H27N5O2: C, 62.6; H, 7.9; N, 20.3. Found: C, 62.3; H, 8.0; N, 20.2%.
