To a stirred solution of 4-[(2′-oxo-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-1′(2′H)-yl)methyl]benzoic acid (0.400 g, 0.93 mmol) in anhydrous chloroform (20 mL) was added thionyl chloride (0.27 mL, 3.7 mmol). The solution was heated at reflux for 2 h and concentrated in vacuo to afford 4-[(2′-oxo-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-1′(2′H)-yl)methyl]benzoyl chloride (0.45 g) as a pale yellow solid. To a solution of 2-fluoroaniline (0.1 mL, 1.0 mmol) and triethylamine (0.43 mL, 3.1 mmol) in anhydrous dichloromethane (10 mL) at 0° C. under nitrogen was added 4-((2′-oxo-3,7-dihydro-2H-spiro[benzofuro[5,6-b][1,4]dioxine-8,3′-indoline]-1′-yl)methyl)benzoyl chloride (0.46 g, 1.0 mmol). The reaction mixture was stirred at ambient temperature for 42 h and was washed with 10% w/v hydrochloric acid (10 mL), water (10 mL) and brine (10 mL). The organic phase was dried over anhydrous magnesium sulfate, filtered and concentrated in vacuo. The residue was purified by column chromatography and eluted with hexanes/ethyl acetate (1/1) to afford N-(2-fluorophenyl)-4-[(2′-oxo-2,3-dihydrospiro[furo[2,3-g][1,4]benzodioxine-8,3′-indol]-1′(2′H)-yl)methyl]benzamide (0.262 g, 49%) as a colorless solid: mp 245-251° C.; 1H NMR (300 MHz, CDCl3) δ 8.48-8.43 (m, 1H), 8.11-8.04 (m, 1H), 7.88 (d, J=8.1 Hz, 2H), 7.46 (d, J=8.1 Hz, 2H), 7.24-7.02 (m, 6H), 6.75 (d, J=7.8 Hz, 1H), 6.52 (s, 1H), 6.24 (s, 1H), 5.16 (d, J=15.9 Hz, 1H), 4.95 (d, J=8.7 Hz, 1H), 4.89 (d, J=15.9 Hz, 1H), 4.68 (d, J=9.0 Hz, 1H), 4.21-4.10 (m, 4H); 13C NMR (75 MHz, CDCl3) δ 177.6, 164.9, 155.3, 152.7 (d, J=241.4 Hz), 144.7, 141.7, 140.0, 138.3, 134.1, 132.2, 128.8, 127.8 (d, J=4.1 Hz), 126.4 (d, J=9.8 Hz), 124.7-124.6 (m), 124.1, 123.7, 121.8, 120.8, 114.8 (d, J=19.1 Hz), 111.4, 109.1, 99.5, 80.1, 64.5, 63.9, 58.0, 43.8; MS (ES+) m/z 523.0 (M+1).
