Reaction Steps
To a mixture of spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one (0.281 g, 1.0 mmol) and (2-methyl-5-(trifluoromethyl)oxazol-4-yl)methanol (0.18 g, 1.0 mmol) in anhydrous tetrahydrofuran (8 mL) was added tributylphosphine (0.30 g, 1.5 mmol) at 0° C., followed by additional of N,N,N′,N′-tetramethylazodicarboxamide (0.26 g, 1.5 mmol). The reaction mixture was stirred at 0° C. for 1 h and stirred at ambient temperature for 16 h. The reaction mixture was quenched with aqueous ammonium chloride (25%, 50 mL) and extracted with ethyl acetate (3×40 mL). The combined organic solution was washed with brine (30 mL), dried over anhydrous sodium sulfate and concentrated in vacuo to dryness. The residue was purified by column chromatography with ethyl acetate in hexanes (10% to 30% gradient) to give 1′-{[2-methyl-5-(trifluoromethyl)-1,3-oxazol-4-yl]methyl}spiro[furo[2,3-f][1,3]benzodioxole-7,3′-indol]-2′(1′H)-one (0.30 g, 68%) as a colorless solid: mp 136-137° C. (diethyl ether/hexane); 1H NMR (300 MHz, DMSO-d6) δ 7.32 (ddd, J=7.7, 1.2, 1.2 Hz, 1H), 7.19 (dd, J=7.6, 1.0 Hz, 1H), 7.07-7.03 (m, 2H), 6.70 (s, 1H), 6.29 (s, 1H), 5.93 (dd, J=5.0, 0.7 Hz, 2H), 4.98 (q, J=16.4 Hz, 2H), 4.75 (dd, J=20.8, 9.4 Hz, 2H), 2.46 (s, 3H); 13C NMR (75 MHz, DMSO-d6) δ 176.5, 163.6, 155.1, 148.2, 141.9, 141.5, 137.6 (d, 3JC-F=2.1 Hz), 133.5 (q, 2JC-F=42.7 Hz), 131.6, 128.7, 123.5, 123.0, 119.8, 119.2 (q, 1JC-F=266.9 Hz), 109.0, 103.0, 101.3, 93.1, 79.3, 57.2, 34.9, 13.4; MS (ES+) m/z 445.3 (M+1).
