Reaction Steps
H2O2 (70%, 2.5 mL, ca. 51 mmol) was added dropwise to a stirred solution of TFAA (7.1 mL, 51 mmol) in DCM (70 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 40 (1.75 g, 5.1 mmol) and TFA (0.84 mL, 11 mmol) in CHCl3 (70 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 (3×80 mL). The combined organic fraction was dried and the solvent evaporated. The residue was purified by column chromatography, eluting with a gradient (4-20%) of MeOH/DCM, to give 1,4-dioxide 41 (0.15 g, 8%) as a red gum: 1H NMR δ 8.91 (br s, 1H, NH), 8.05 (s, 2H, H-5, H-9), 4.09 (t, J=5.8 Hz, 2H, CH2N), 3.84 (td, J=12.8, 1.9 Hz, 1H, CHO), 3.57-3.66 (m, 4H, 2×CH2), 3.57 (s, 3H, OMe), 3.40 (td, J=13.3, 3.5 Hz, 1H, CH2), 3.01-3.12 (m, 5H, H-6, H-8, CH2), 2.19 (p, J=7.4 Hz, 2H, H-7), 2.16-2.23 (m, 1H, CH2), 2.02-2.08 (m, 1H, CH2), 1.62-1.72 (m, 1H, CH2), 1.37-1.48 (m, 1H, CH2); 13C NMR δ 155.6, 149.4, 146.1, 138.1, 129.7, 115.5, 111.7, 73.2, 69.7, 67.6, 61.4, 56.9, 36.5, 33.3, 32.4, 28.5, 25.6, 20.3; HRMS (FAB+) calcd for C18H26N5O3 (MH+) m/z 360.2036, found 360.2039.
