Pentane → 1,1'-diBOC-2,10-dicarbethoxy-6-ethoxycarbonyloxy-indolo[2,3-b]carbazole

Participants

Reaction Conditions

Reaction Steps

2,10-Dicarbethoxy-6-ethoxycarbonyloxy-5,7-dihydro-indolo [2,3-b]carbazole (63). To a solution of 1.7 M t-BuLi in pentane (32.3 mL, 54.8 mmol) in THF (200 mL) at −100° C. under argon was added 61 (7.0 g, 9.97 mmol) in THF (20 mL), and stirred for 10 min. ClCO2CH2CH3 (30 mL) was added and the mixture was slowly warmed to −10° C. during 2.5 h. The reaction mixture was poured into saturated aqueous NH4Cl and extracted with 50% EtOAc/hexane. The combined organic extracts were dried (MgSO4), filtered, and concentrated to afford a crude product. Flash chromatography (10%; 20% EtOAc/hexane) yielded 1,1′-diBOC-2,10-dicarbethoxy-6-ethoxycarbonyloxy-indolo[2,3-b]carbazole 62 as a white solid (6.1 g, 89%). 62 (4.3 g, 6.24 mmol) was deprotected using the general procedure. Recrystallization (ethyl acetate/hexane) afforded 63 as a white solid (2.8 g, 92%): 1H NMR (300 MHz, CDCl3) δ 1.50 (m, 9, CO2CH2CH3), 4.48 (m, 6, CO2CH2CH3), 7.46 (d, J=8.3 Hz, 2, ArH), 8.16 (dd, J=1.5, 8.3 Hz, 2, ArH), 8.49 (br.s, 2, NH), 8.71 (s, 1, ArH), 8.89 (d, J=1.5 Hz, 2, ArH).

Provenance & Evidence