Trifluoroacetic acid → HCID 10805772, compound

Participants

Reaction Steps

NaOMe (4.8 mL of a 1.28 M solution in MeOH, 6.1 mmol) was added dropwise to a solution of 1-(t-butyloxycarbonyl)-3,3-di(methoxycarbonyl)-6-nitroindoline (2.11 g, 5.55 mmol) in THF (100 mL) under nitrogen at 20° C., immediately giving an intense purple colour. After 5 min trifluoroacetic acid (0.51 mL, 6.7 mmol) was added in one portion, causing the nitronate colour to disperse. The pale yellow solution was diluted with aq. NaCl, extracted with EtOAc, and the extracts dried (Na2SO4) and evaporated to give crude title compound as a pale yellow oil. This compound showed signs of air oxidation on standing at room temperature, so was not further purified but used directly in the next step. 1H NMR (CDCl3) δ8.67, 8.34 (2 x br s, 1H, H-7), 7.85 (dd, J=8.2, 2.1 Hz, 1H, H-5), 7.49 (d, J=8.2 Hz, 1H, H-4), 4.48 (dd, J=10.5, 5.4 Hz, 1H, NCH2CH), 4.28 (dd, J=10.5, 5.3 Hz, 1H, NCH2CH), 4.22 (t, J=10.6 Hz, 1H, NCH2CH), 3.82 (s, 3H, CO2Me), 1.60 (s, 9H, t-Bu): 13C NMR δ170.5 (CO2Me), 151.6, 149.1 (C-6,8,9, NCO2, two peaks not observed), 125.5, 117.7, 109.9 (C-4,5,7), (OCMe3 peak not observed), 53.1 (OMe), 50.3 (C-2), 44.4 (C-3), 28.3 (C(CH3)3). HRMS calculated for C15H18N2O6 : 322.11649. Found: 322.11627.

Provenance & Evidence