Reaction Steps
A 100-mL three-neck round-bottomed flask equipped with a reflux condenser, magnetic stirrer and nitrogen inlet was charged with 231e (150 mg, 0.447 mmol), 131a (340 mg, 0.581 mmol), sodium carbonate (142 mg, 1.34 mmol), water (2 mL) and 1,4-dioxane (8 mL). After bubbling nitrogen through the resulting suspension for 30 min, tetrakis-(triphenylphosphine)palladium(0) (52 mg, 0.045 mmol) was added, and the reaction mixture was heated at reflux for 2 h. After that time, the mixture was cooled to room temperature and diluted with methylene chloride (100 mL) and water (30 mL). The organic layer was separated, and the aqueous layer was extracted with methylene chloride (3×30 mL). The combined organic layers were dried over sodium sulfate and concentrated under reduced pressure to afford a brown residue. A 100-mL single-neck round-bottomed flask equipped with a magnetic stirrer was purged with nitrogen and charged with the crude residue, THF (10 mL) and a 1 M solution of tetrabutylammonium fluoride in THF (4.50 mmol, 4.5 mL). The resulting mixture was stirred at room temperature for 2 h. After this time, the mixture was diluted with methylene chloride (100 mL) and washed with water (30 mL). The organic layer was separated, and the aqueous layer was extracted with methylene chloride (3×30 mL). The combined organic layers were dried over sodium sulfate and concentrated under reduced pressure. The residue was purified by column chromatography (silica, 0% to 10% methanol/methylene chloride) to afford a 44% yield (120 mg) of 235 as an off-white solid: mp 218-220° C. (dec); 1H NMR (500 MHz, DMSO-d6) d 9.21 (s, 1H), 7.89 (d, 1H, J=1.0 Hz), 7.70 (dd, 1H, J=8.1, 2.0 Hz), 7.50 (s, 1H), 7.34 (dd, 1H, J=9.9, 3.0 Hz), 7.30 (dd, 1H, J=9.1, 2.5 Hz), 7.13 (d, 1H, J=8.0 Hz), 4.82 (m, 1H), 4.50 (m, 1H), 4.04 (m, 1H), 4.04 (m, 1H), 3.84 (m, 1H), 3.75 (m, 4H), 3.54 (s, 3H), 3.02 (m, 1H), 2.89 (m, 1H), 2.75 (s, 2H), 2.53 (d, 2H, J=6.5 Hz), 2.46 (s, 3H), 1.23 (s, 6H); MS (ESI+) m/z 600.2 (M+H).
