Reaction Steps
A solution of 7-methoxy-3-carboxycoumarin (335 mg, 1.5 mmol), NEt3 (1.05 mL, 7.6 mmol) and DPPA (0.36 mL, 1.7 mmol) in benzene (15 mL) was stirred at 65° C. for 4 h. A solution of 3 (260 mg, 1.3 mmol) in benzene (2 mL) was then added and the mixture stirred at 65° C. for 16 h. Upon cooling, water (40 mL) was added and the mixture extracted with DCM (3×40 mL). The combined organic phases were washed with sat. NaHCO3 (30 mL), brine (30 mL), dried over anhydrous MgSO4 and reduced to dryness. The resultant solid was purified by flash column chromatography (×2, gradient elution with DCM/EtOAC (8/2) to DCM/EtOAc/MeOH (8/1/1), and then DCM/MeOH (9/1)) to yield 5 as an off-white solid (270 mg, 49.5%). Rf 0.63 (hexanes/EtOAc 1/2); Mp. 131-134° C.; 1H NMR (300 MHz, CDCl3) δ 8.22 (1H, s), 7.34 (2H, m), 6.84 (1H, dd, J=8.6 Hz, 2.4 Hz), 6.79 (1H, d, J=2.4 Hz), 5.29 (1H, s), 4.18 (2H, t, J=6.3 Hz), 3.85 (2H, 2q, J=7.0 Hz), 3.82 (3H, s), 2.42 (2H, 2d, J=7.1 Hz), 2.22 (1H, m), 2.08 (1H, dq, J=14.2 Hz, 5.0 Hz), 1.94-1.85 (1H, m), 1.78-1.66 (3H, m), 1.52-1.42 (1H, m), 1.33 (3H, t, J=7.0 Hz); 13C NMR (75 MHz, CDCl3) δ 201.0, 176.9, 161.1, 158.9, 153.6, 151.3, 128.4, 122.0, 121.9, 113.3, 113.2, 102.4, 100.8, 66.0, 64.4, 55.9, 44.9, 28.3, 26.6 (×2), 26.2, 14.3; ESI MS m/z 438 (M++Na+).
