Reaction Steps
H2O2 (70%, 1.4 mL, ca. 28 mmol) was added dropwise to a stirred solution of TFAA (4.0 mL, 28 mmol) in DCM (30 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 34 (890 mg, 2.8 mmol) and TFA (1.1 mL, 14 mmol) in DCM (35 mL) at 0° C. The solution was stirred at 20° C. for 6 h, diluted with dilute aqueous NH3 solution (80 mL) and extracted with DCM (4×125 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 35 (390 mg, 42%) as a red solid: mp 152° C. (dec.); 1H NMR δ 8.12 (s, 1H, H-9), 8.10 (s, 1H, H-5), 7.30 (br s, 1H, NH), 4.04 (p, J=5.8 Hz, 1H, CHO), 3.67-3.72 (m, 2H, CH2N), 3.54 (dt, J=5.9, 5.5 Hz, 2H, CH2N), 3.25 (s, 3H, OCH3), 3.11 (dt, J=7.4, 0.9 Hz, 2H, H-6), 3.06 (dt, J=7.4, 1.1 Hz, 2H, H-8), 2.95-2.99 (m, 2H, CH2N), 2.78 (t, J=5.9 Hz, 2H, CH2N), 2.20 (p, J=7.5 Hz, 2H, H-7); 13C NMR δ 155.6, 149.4, 145.8, 138.0, 129.8, 115.8, 111.6, 69.9, 61.5 (2), 58.0, 56.0, 39.5, 33.4, 32.4, 25.6; MS (APCI) m/z 332 (MH+, 100%). Anal. calcd for C16H21N5O3.0.15CH2Cl2: C, 56.4; H, 6.2; N, 20.4. Found: C, 56.2; H, 6.1; N, 20.4%.
