Reaction Steps
Hydrogen peroxide (70%, 0.44 mL, ca. 8.7 mmol) was added dropwise to a stirred solution of trifluoroacetic anhydride (1.23 mL, 8.7 mmol) in DCM (20 mL) at 5° C. The mixture was stirred at 5° C. for 5 min, warmed to 20° C., stirred for 10 min, and cooled to 5° C. The mixture was added to a stirred solution of 1-oxide 13 (268 mg, 0.9 mmol) and trifluoroacetic acid (0.34 mL, 4.4 mmol) in DCM (20 mL) at 5° C. and the mixture stirred at 20° C. for 6 h. The solution was carefully diluted with dil. aq. NH3 solution (2.0 mL) and the mixture extracted with CHCl3 (5×50 mL). The 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 14 (140 mg, 50%) as a red solid, mp (MeOH/DCM) 146-149° C.; 1H NMR δ 8.21 (d, J=9.6 Hz, 1 H, H-8), 7.52 (d, J=2.6 Hz, 1 H, H-5), 7.48 (br s, 1 H, NH), 7.10 (dd, J=9.6, 2.6 Hz, 1 H, H-7), 4.31-4.36 (m, 2 H, CH2O), 3.81-3.84 (m, 2 H, CH2O), 3.61-3.65 (m, 2 H, CH2N), 3.47 (s, 3 H, OCH3), 2.62 (br t, J=6.0 Hz, 2 H, CH2N), 2.31 [s, 6 H, (CH3)2]; 13C NMR δ 165.2, 150.2, 140.2, 125.7, 123.5, 120.5, 95.6, 70.3, 68.8, 59.2, 57.5, 45.0 (2), 38.9. Anal. Calcd for C14H21N5O4¼CH2Cl2: C, 50.1; H, 6.2; N, 20.2. Found: C, 50.1; H, 6.1; N, 20.6%.
