To a solution of 3F (400 mg, 1.07 mmol) in DMF (8 mL) was added cesium carbonate (873 mg, 2.68 mmol), followed by benzyl bromide (0.38 mL, 3.21 mmol). The reaction mixture was stirred at 50° C. for 1 h. After cooling to RT, water (100 mL) was added. The reaction mixture was extracted with EtOAc (3×30 mL). During the extraction, some precipitates formed. The solid was collected by filtration and washed with EtOAc to give the title compound (250 mg). The combined organics were washed with saturated NaCl, dried over Na2SO4, filtered and concentrated. The resultant residue was purified by silica gel (40 g) column chromatography eluting with a gradient of EtOAc (0-60%) in hexane to give additional 160 mg of the title compound (total 410 mg, 83%) as a white solid. LC/MS (method A): retention time=3.55 min, (M+H)+=464.
