To this flask was added THF (40 mL, 0.1 M) via cannula, and this mixture was allowed to stir at room temperature for 2 minutes to allow for complete dissolution of KOt-Bu. The reaction vessel was transferred to a -78 °C saturated dry-ice acetone bath and allowed to stir for 10 minutes before a solution of acetate 5-4 (1.5 g, 4.0 mmol, 1.0 equiv) in THF (11 mL, 1.0 M) was added over 5 minutes, resulting in a yellow reaction mixture. After the reaction mixture had stirred for 15 minutes at -78 °C, sat. aq. NH4Cl (25 mL) was added to the reaction mixture and the reaction vessel was removed from the dry-ice acetone bath. Once at room temperature, the layers were separated and the aqueous layer was extracted with EtOAc (2 x 50 mL). The combined organic extracts were washed with brine (25 mL), dried over anhydrous Na2SO4, filtered, and concentrated under reduced pressure by rotary evaporation to provide a crude yellow oil.