反应详情

A 250 mL round-bottom flask was charged with ethyl 2-[(2′-oxo-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-1′(2′H)-yl)methyl]pyridine-3-carboxylate (2.3 g, 5.0 mmol), lithium hydroxide (0.48 g, 20.0 mmol), tetrahydrofuran (30 mL), water (50 mL) and methanol (30 mL). The reaction mixture was stirred under nitrogen at reflux for 5 h, allowed to cool to ambient temperature and concentrated in vacuo. The residue was taken up in water (100 mL) and acidified to pH 1 by the addition of 10 M hydrochloric acid, causing a precipitate to be deposited. The solid was collected by filtration, washed with water and recrystallized from ethanol (50 mL) to afford 2-[(2′-oxo-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-1′(2′H)-yl)methyl]pyridine-3-carboxylic acid (1.96 g, 91%) as an off-white solid: 1H NMR (300 MHz, DMSO-d6) δ 8.57-8.45 (m, 1H), 8.33-8.26 (m, 1H), 7.42 (dd, J=7.82, 4.77 Hz, 1H), 7.21-6.83 (m, 4H), 6.49-6.44 (m, 2H), 5.39 (ABq, 2H), 4.72 (ABq, 2H), 4.24-4.00 (m, 4H).

1. temperatureat reflux for 5 h
2. concentrationconcentrated in vacuo
3. additionacidified to pH 1 by the addition of 10 M hydrochloric acid
4. filtrationThe solid was collected by filtration
5. washwashed with water
6. customrecrystallized from ethanol (50 mL)