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A suspension of KOH (14 g, 250 mmol) in abs. ethanol (150 mL) was treated with isatin (7.35 g, 50 mmol) and dry acetone (7.4 mL, 100 mmol) at room temperature. The reaction mixture was refluxed for 1.5 h then brought to room temperature and neutralized with con. HCl (pH~7). The reaction mixture was evaporated to dryness under vacuum to get the crude acid. The crude product was suspended in dry EtOH (150 mL), toluene (150 mL) and cone. H2SO4 (6 mL) were added drop wise carefully with stirring. The mixture was refluxed for 17 h using a Dean-Stark trap to separate the water generated during the reaction. The solvent was evaporated under vacuum and the residue was taken into EtOAc (200 mL) and washed with 0.1 N NaOH (100 mL), water (3x20 mL) and brine (2 x 20 EPO <DP n="35"/>niL). The organic layer was dried (K2CO3) overnight. The solvent was evaporated by vacuum and the residue was purified by flash chromatography (CHCl3: MeOH= 99:1) to get the title compound (7.01 g, 65.0%) as colorless oil. 1H NMR (CDCl3) delta: 1.46 (t, J = 7.03 Hz, 3H), 2.78 (s, 3H), 4.50 (d, J = 7.17, 15.34 Hz, 2H), 7.57 (dt, J = 1.07, 8.34 Hz, IH), 7.71 (dt, J = 1.32, 8.34 Hz, IH), 7.77 (s, IH), 8.07 (dd, J = 0.59, 8.34 Hz, IH), 8.68 (dd, J= 1.17, 8.49 Hz, IH). |