Reaction Steps
To a stirred solution of 5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-2′(1′H)-one (0.06 g, 0.20 mmol) in anhydrous N,N-dimethylformamide (10 mL) was added sodium hydride (60% in mineral oil, 0.20 g, 0.50 mmol) at ambient temperature. The mixture was stirred for 15 min, and iodomethane (0.14 g, 1.0 mmol) was added in one portion. The reaction mixture was stirred at ambient temperature for 1 h, and then concentrated to dryness. The residue was purified by flash chromatography with ethyl acetate in hexanes (0% to 30% gradient) to afford 1′-methyl-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-2′(1′H)-one (0.06 g, 88%): mp 187-190° C.; 1H NMR (300 MHz, CDCl3) δ7.32 (dd, J=7.4, 7.4 Hz, 1H), 7.17 (d, J=7.4 Hz, 1H), 7.06 (t, J=7.4 Hz, 1H), 6.91 (d, J=7.4 Hz, 1H), 6.49 (s, 1H), 6.40 (s, 1H), 4.79 (ABq, 2H), 4.52 (t, J=8.5 Hz, 2H), 3.28 (s, 3H), 2.98 (t, J=8.5 Hz, 2H); 13C NMR (75 MHz, CDCl3) δ 177.7, 161.6, 161.1, 142.9, 132.7, 128.6, 123.6, 123.2, 120.0, 119.7, 118.8, 108.1, 93.0, 80.4, 72.2, 57.6, 28.9, 26.6; MS (ES+) m/z 294.1 (M+1).
