Hydrochloric Acid → 2-((2'-oxo-6H-spiro[benzofuro[6,5-d][1,3]dioxole-7,3'-indoline]-1'-yl)methyl)oxazole-4-carboxylic acid

Participants

Reaction Steps

To a solution of methyl 2-[(2′-oxospiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-1′(2′H)-yl)methyl]-1,3-oxazole-4-carboxylate (1.17 g, 2.79 mmol) in tetrahydrofuran (20 mL) was added a solution of sodium hydroxide (0.45 g, 11.1 mmol) in water (5 mL). The mixture was stirred at reflux for 16 h. After cooling down to ambient temperature, the mixture was acidified with concentrated hydrochloric acid (2 mL). The reaction mixture was concentrated in vacuo to remove most of tetrahydrofuran and extracted with ethyl acetate (3×25 mL). The combined organic solution was dried over sodium sulfate and filtered. The filtrate was concentrated in vacuo to dryness. The residue was triturated with diethyl ether and ethyl acetate to afford 2-[(2′-oxospiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-1′(2′H)-yl)methyl]-1,3-oxazole-4-carboxylic acid (0.65 g, 58%) as a colorless solid: 1H NMR (300 MHz, DMSO-d6) δ 13.07 (br, 1H), 8.74 (s, 1H), 7.29 (t, J=7.7 Hz, 1H), 7.17 (d, J=6.6 Hz, 1H), 7.10 (d, J=7.8 Hz, 1H), 7.04 (t, J=7.5 Hz, 1H), 6.66 (s, 1H), 6.34 (s, 1H), 6.04 (s, 2H), 5.20-5.08 (m, 2H), 4.73 (ABq, 2H); 13C NMR (75 MHz, DMSO-d6) δ177.1, 162.2, 159.9, 155.7, 148.8, 146.4, 142.2, 142.1, 133.8, 132.2, 129.4, 124.1, 123.9, 120.3, 109.7, 103.8, 101.9, 93.7, 80.0, 57.8, 31.2; MS (ES+) m/z 407.1 (M+1).

Provenance & Evidence