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) δ8.57-8.45 (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)