Acetic Acid → 1,3-Dihydro-pyrrolo[3,2-f]quinoline-2-one

Participants

Reaction Steps

A solution of 2.3 g (12 mmol) of 3-H-pyrrolo[3,2-f]quinoline-1,2-dione (prepared from 6-aminoquinoline according to Procedure A) and 2.0 ml (0.06 mol) of hydrazine in 50 ml of DMF and 50 ml of ethanol was stirred at reflux for 2 h. The resulting suspension was allowed to cool to ambient temperature and was then chilled in an ice bath and filtered. The solid was washed with a small volume of ethanol and allowed to air dry to give 1-hydrazono-1,3-dihydropyrrolo[3,2-f]quinolin-2-one as an orange solid (1.8 g, 73%): 1H NMR (DMSO-d6): δ 7.37 (d, J=8.8 Hz, 1H), 7.47 (dd, J=8.4, 4.2 Hz,1H), 7.81 (d, J=8.8 Hz, 1H), 8.71 (dd, J=4.2, 1.6 Hz, 1H), 8.80 (d, J=8.4 Hz, 1H), 9.90 (br d, J=14.7 Hz, 1H), 10.89 (br d, J=14.7 Hz, 1H), 10.95 (br s, 1H); ESI-MS m/z 213 (M+H)+. A solution 1.8 g (8.5 mmol) of 1-hydrazono-1,3-dihydropyrrolo[3,2-f]quinolin-2 -one in 50 ml of freshly prepared 0.5 M sodium ethoxide solution was stirred at reflux for 3 h. The solution was diluted with 50 ml of water, neutralized with acetic acid, and concentrated on a rotary evaporator until cloudy. The solution was stored in a refrigerator overnight. The solid was filtered off, and the filtrate was extracted with three 80-ml portions of EtOAc. A solution of the solid in MeOH/EtOAc was combined with the extracts and passed through a short pad of silica gel, eluting with EtOAc. The solution was then concentrated to a small volume on a rotary evaporator, and the resulting suspension was diluted with an equal volume of ethanol, sonicated, and filtered to give 3-H-pyrrolo[3,2-f]quinoline-2-one as a light green solid (0.52 g; 33%); 1H NMR (DMSO-d6): δ 3.80 (s, 2H), 7.35 (d, J=8.8 Hz, 1H), 7.44 (dd, J=8.4, 4.2 Hz, 1H), 7.88 (d, J=8.8 Hz, 1H), 8.08 (d, J=8.4 Hz, 1H), 8.70 (dd, J=4.2, 1.6 Hz,1H), 10.57 (br s, 1H); APCI-MS m/z. 183 (M−H)−.

Provenance & Evidence