Reaction Steps
To a solution of spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one (4.26 g, 15.10 mmol) in 2-butanone (120 mL) was added cesium carbonate (14.76 g, 45.30 mmol) and ethyl 5-(bromomethyl)-2-(trifluoromethyl)furan-3-carboxylate (Lyalin, V. V.; et al., Zhurnal Organicheskoi Khimii (1984), 20(4):846) (4.80 g, 15.90 mmol). The reaction mixture was heated at 60° C. to 70° C. for 18 h, cooled to ambient temperature and filtered. The solid was washed with ethyl acetate. The filtrate was concentrated in vacuo, the residue was purified by column chromatography with ethyl acetate and hexanes to afford ethyl 5-[(2′-oxospiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-1′(2′H)-yl)methyl]-2-(trifluoromethyl)furan-3-carboxylate (4.65 g, 61%): mp 162-164° C.; 1H NMR (300 MHz, CDCl3) δ 7.23-7.17 (m, 2H), 7.12-7.06 (m, 1H), 6.94 (d, J=7.8 Hz, 1H), 6.76 (s, 1H), 6.50 (s, 1H), 5.86-5.85 (m, 2H), 5.05-4.87 (m, 3H), 4.68-4.64 (m, 1H), 4.31 (q, J=7.2 Hz, 2H), 1.32 (t, J=7.2 Hz, 3H); 13C NMR (75 MHz, CDCl3) δ 177.2, 160.4, 155.9, 150.6, 149.1, 143.5, 142.5, 141.1, 132.0, 129.1, 124.2, 124.0, 120.7, 120.0, 119.0, 116.4, 111.1, 108.7, 103.0, 101.6, 93.7, 80.4, 61.7, 58.2, 36.7, 13.9; MS (ES+) m/z 502.1 (M+1).
