Reaction Steps
H2O2 (70%, 0.27 mL, ca. 5.3 mmol) was added dropwise to a stirred solution of TFAA (0.8 mL, 5.3 mmol) in DCM (10 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 177 (153 mg, 0.5 mmol) and TFA (0.20 mL, 2.7 mmol) in DCM (10 mL) at 0° C. The solution was stirred at 20° C. for 16 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 (i) starting material 177 (37 mg, 24%) and (ii) 1,4-dioxide 178 (47 mg, 29%) as a red solid: mp (MeOH) 148-151° C.; 1H NMR δ 8.02 (s, 1H, H-10), 7.98 (s, 1H, H-5), 7.35 (br s, 1H, NH), 3.63 (br t, J=6.0 Hz, 2H, CH2N), 2.98-3.04 (m, 2H, CH2), 2.91-2.96 (m, 2H, CH2), 2.61 (br t, J=6.0 Hz, 2H, CH2N), 2.30 [s, 6H, N(CH3)2], 1.83-1.92 (m, 4H, H-7, H-8); 13C NMR δ 149.4, 148.7, 138.8, 136.5, 128.9, 120.1, 115.8, 57.6, 45.2 (2), 38.9, 30.3, 29.4, 22.3, 22.0. Anal. calcd for C15H21N5O2.1½H2O: C, 54.5; H, 7.3; N, 21.2. Found: C, 54.4; H, 6.3; N, 20.7%.
