After the reaction had stirred at room temperature for 30 minutes, the reaction mixture was diluted with water (30 mL). The layers were separated, and the aqueous layer was extracted with 1:1 hexanes/Et2O (2 x 50 mL). The combined organic extracts were washed with brine (2 x 50 mL), dried over anhydrous Na2SO4, filtered and concentrated under reduced pressure by rotary evaporation to give a yellow viscous oil. Purification by flash column chromatography on silica gel (10% Et2O/hexanes to 30% Et2O/hexanes) afforded 4-9 (4.1 g, 51% over two steps) as a colorless solid.