Trifluoroacetic acid → 3-(tert-butyloxycarbonyl)-1-methoxycarbonyl-5-nitro-1,2-dihydro-3H-benz[e]indole

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Reaction Steps

NaOMe (5.61 mL of a 0.62 M solution in MeOH, 3.48 mmol) was added dropwise to a stirred solution of 10 (1.00 g, 2.32 mmol) in THF (20 mL) at 10° C. After 15 min at 20° C., trifluoroacetic acid (0.29 mL, 3.8 mmol) was added in one portion, causing dissipation of the deep purple colour of the solution. The reaction was diluted with saturated NaCl, extracted with CH2Cl2 and the extract was washed twice with water and dried (Na2SO4). The CH2Cl2 solution was filtered through a short column of silica gel, eluting with additional CH2Cl2, and the solvent was evaporated under reduced pressure below 30° C. to give crude 3-(tert-butyloxycarbonyl)-1-methoxycarbonyl-5-nitro-1,2-dihydro-3H-benz[e]indole (11) (0.85 g, 98%), which was used without further purification. 1H NMR (CDCl3) δ8.89 (br s, 1 H, H-9), 8.38 (br s, 1 H, H-7), 7.87 (d, J=8.3 Hz, 1 H, H-4), 7.63-7.51 (m, 2 H, H-5,6), 4.61 (dd, J=10.5, 3.9 Hz, 1 H, NCH2CH), 4.50 (br s, 1 H, NCH2CH), 4.32 (t, J=11.1 Hz, 1 H, HCH2CH), 3.72 (s, 3 H, CO2CH3), 1.61 (s, 9 H, C(CH3)3).

Provenance & Evidence