Reaction Steps
To a solution of 4-[(2′-oxo-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-1′(2′H)-yl)methyl]benzamide (0.40 g, 0.96 mmol) in 1,4-dioxane (15 mL) was added N,N-dimethylacetamide dimethyl acetal (1.42 mL, 9.71 mmol). The reaction was heated to reflux for 18 h, concentrated in vacuo. To the above residue were added acetic acid (15 mL) and hydrazine monohydrate (0.15 mL, 3.17 mmol). The reaction was stirred at 90° C. for 6 h, cooled to ambient temperature, quenched with saturated sodium bicarbonate (15 mL), and extracted with chloroform. The combined organic solution was washed with water and brine, dried over anhydrous sodium sulfate and filtered. The filtrate was concentrated in vacuo. The residue was purified by column chromatography with 5% methanol in ethyl acetate, and recrystallized from dichloromethane and hexanes to afford 1′-[4-(5-methyl-4H-1,2,4-triazol-3-yl)benzyl]-5,6-dihydrospiro[benzo[1,2-b:5,4-b′]difuran-3,3′-indol]-2′(1′H)-one (0.07 g, 16%) as a colorless solid: mp 169-180° C. (hexanes); 1H NMR (300 MHz, CDCl3) δ10.72 (s, 1H), 8.01 (d, J=8.1 Hz, 2H), 7.41 (d, J=8.1 Hz, 2H), 7.15 (d, J=7.5 Hz, 2H), 7.01 (t, J=7.5 Hz, 1H), 6.79 (d, J=7.7 Hz, 1H), 6.45 (s, 1H), 6.40 (s, 1H), 5.19-4.09 (m, 4H), 4.53-4.47 (m, 2H), 2.95-2.90 (m, 2H), 2.50 (s, 3H); 13C NMR (75 MHz, CDCl3) δ178.3, 161.9, 161.4, 141.9, 136.9, 132.7, 128.8, 127.8, 126.9, 123.9, 123.6, 120.0, 119.9, 118.8, 109.4, 93.2, 80.6, 72.4, 57.8, 44.0, 28.9, 11.7; MS (ES+) m/z 450.8 (M+1).
