After stirring at room temperature for 16 hours, the reaction mixture was diluted with water (150 mL) and the layers were separated. The aqueous layer was extracted with EtOAc (3 x 50 mL). The combined organic extracts were washed with brine (100 mL), dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure by rotary evaporation to provide a crude yellow oil. Purification by flash column chromatography on silica gel (5% EtOAc/hexanes to 30% EtOAc/hexanes) afforded 9-1 (707 mg, 34%) as a colorless foam and recovered 3-1 (938 mg, 47%) as a yellow oil.