After stirring for 25 minutes at 0 °C, Bu3SnH (0.29 mL, 1.1 mmol, 1.1 equiv) was added dropwise to the reaction mixture over 3 minutes at 0 °C, resulting in a yellow reaction mixture. Once the reaction mixture had stirred for an additional 10 minutes at 0 °C, the reaction vessel was transferred to a -78 °C saturated dry-ice acetone bath, and the reaction mixture was allowed to stir for 5 minutes at -78 °C. To the reaction mixture was added a solution of β-ethoxy enone SI-4 (140 mg, 1.0 mmol, 1.0 equiv) in THF (1.0 mL, 1.0 M) dropwise over 5 minutes, which resulted in an orange reaction mixture.