Reaction Steps
A mixture of 2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one (0.30 g, 1.03 mmol), 2-(iodomethyl)-1,4-dioxane (0.31 g, 1.35 mmol) and cesium carbonate (0.52 g, 1.58 mmol) in 2-butanone (7 mL) was stirred at reflux under nitrogen for 4 h. Once cooled, the reaction was diluted with ethyl acetate and the suspension was filtered through Celite. The filtrate was concentrated under reduced pressure and the residue was purified by flash column chromatography with dichloromethane/diethyl ether (14:1) to afford 1′-(1,4-dioxan-2-ylmethyl)-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one as an inseparable mixture with unreacted lactam (0.36 g). A mixture of this material, benzyl bromide (0.12 mL, 1.00 mmol) and cesium carbonate (0.50 g, 1.55 mmol) in 2-butanone (7 mL) was then stirred at reflux under nitrogen for 15 h. Work-up as described above and purified by flash column chromatography with (hexanes/ethyl acetate) (2:1, increased to 1:1) afforded 1′-(1,4-dioxan-2-ylmethyl)-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one (0.24 g, 58%) as a colorless solid, along with 1′-benzyl-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one (0.09 g, 24%) as a colorless solid. Characterization for 1-(1,4-dioxan-2-ylmethyl)-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-2′(1′H)-one: mp 160-165° C. (hexanes); 1H NMR (300 MHz, CDCl3) (diastereomers) δ7.26-7.34 (m, 1H), 7.16 (d, J=7.5 Hz, 1H), 7.01-7.09 (m, 2H), 6.49 (s, 1H), 6.24 (s, 0.5H), 6.21 (s, 0.5H), 4.88 (d, J=8.9 Hz, 0.5 Hz), 4.87 (d, J=8.9 Hz, 0.5H), 4.64 (d, J=8.9 Hz, 0.5H), 4.63 (d, J=8.9 Hz, 0.5H), 4.22-4.16 (m, 2H), 4.15-4.09 (m, 2H), 3.99-3.78 (m, 4H), 3.76-3.55 (m, 4H), 3.47-3.37 (m, 1H); 13C NMR (75 MHz, CDCl3) (diastereomers) δ177.9, 177.8, 156.3, 155.3, 144.71, 144.69, 142.72, 142.66, 138.42, 138.39, 132.4, 132.3, 128.91, 128.85, 123.9, 123.8, 123.5, 121.3, 121.1, 111.7, 111.6, 109.6, 109.4, 99.49, 99.46, 80.2, 80.0, 73.32, 73.29, 69.4, 69.2, 66.8, 66.7, 66.52, 66.48, 64.6, 64.0, 58.1, 58.0, 41.85, 41.76; MS (ES+) m/z 396.2 (M+1).
