Cesium carbonate → methyl 2-[(2'-oxospiro[furo[2,3-f][1,3]benzodioxole-7,3'-indol]-1'(2'H)-yl)methyl]-1,3-oxazole-4-carboxylate

Participants

Reaction Steps

A suspended mixture of spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one (1.60 g, 5.70 mmol), methyl 2-(chloromethyl)oxazole-4-carboxylate (1.00 g, 5.70 mmol) and cesium carbonate (3.71 g, 11.4 mmol) in tetrahydrofuran (10 mL) was refluxed for 16 h. The reaction mixture was cold down to ambient temperature and concentrated in vacuo. The residue was treated with water (20 mL) and extracted with ethyl acetate (3×20 mL). The combined organic solution was dried over sodium sulfate and filtered. The filtrate was concentrated in vacuo to dryness. The residue was purified by column chromatography with a 20% to 30% gradient of ethyl acetate in hexanes to afford methyl 2-[(2′-oxospiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-1′(2′H)-yl)methyl]-1,3-oxazole-4-carboxylate (2.19 g, 92%) as a colorless solid: mp 183-185° C.; 1H NMR (300 MHz, DMSO-d6) δ 8.86 (s, 1H), 7.28 (t, J=7.2 Hz, 1H), 7.16 (d, J=7.0 Hz, 1H), 7.09 (d, J=7.8 Hz, 1H), 7.03 (t, J=7.5 Hz, 1H), 6.66 (s, 1H), 6.41 (s, 1H), 5.90 (d, J=2.1 Hz, 2H), 5.23-5.17 (m, 2H), 4.74 (ABq, 2H), 3.74 (s, 3H); 13C NMR (75 MHz, DMSO-d6) δ177.2, 161.3, 160.2, 155.6, 148.8, 146.9, 142.3, 142.0, 132.8, 132.4, 129.4, 124.1, 123.9, 120.4, 109.7, 103.9, 101.9, 93.7, 80.0, 57.9, 52.3, 37.4; MS (ES+) m/z 421.2 (M+1).

Provenance & Evidence