Reaction Steps
Hydrogen peroxide (70%; 0.53 mL, ca. 10.43 mmol) was added dropwise to a stirred solution of trifluoroacetic anhydride (1.45 mL, 10.43 mmol) in DCM (20 mL) at 5° C. The solution was stirred at 20° C. for 10 min, then cooled to 5° C., added to a solution of 1-oxide 31 (260 mg, 1.04 mmol) and trifluoroactic acid (0.17 mL, 2.23 mmol) in CHCl3 (20 mL) at 5° C. The solution was stirred at 20° C. for 24 h, diluted with dilute aqueous NH3 solution (50 mL) and extracted with CHCl3 (4×50 mL). The combined organic fraction was dried and the solvent evaporated. The residue was purified by column chromatography, eluting with 5% MeOH/DCM to give 1,4-dioxide 32 (90 mg, 32%) as a bright yellow solid, mp 123-126° C.; 1H NMR δ 8.36 (d, J=9.5 Hz, 1 H, H-8), 7.77 (d, J=2.6 Hz, 1 H, H-5), 7.36 (dd, J=9.5, 2.6 Hz, 1 H, H-7), 4.29 (t, J=6.4 Hz, 2 H, CH2), 3.72 (t, J=4.6 Hz, 4 H, 2×CH2O), 3.21 (q, J=7.5 Hz, 2 H, CH2), 2.54 (t, J=7.0 Hz, 2 H, CH2), 2.47 (t, J=4.6 Hz, 4 H, 2×CH2N), 2.10-2.04 (m, 2 H, CH2), 1.44 (t, J=7.5 Hz, 3 H, CH3); 13C NMR δ 165.1, 157.1, 141.5, 129.6, 124.4, 123.4, 98.0, 68.1, 66.9 (2), 55.0, 53.7 (2), 25.9, 24.1, 9.3. Anal. Calcd for C16H22N4O4: C, 57.5; H, 6.3; N, 16.8. Found: C, 57.2; H, 6.5; N, 16.5%.
