KOH (10 equiv.) and THF (10 mL) were added to a dry round-bottom flask and cooled down to °C. Triethyl phosphonoacetate (1.25 equiv.) in THF (7 mL) was added and the mixture stirred for 30 min. A solution of aldehyde (0.54 g, 5 mmol, 1.0 equiv.) in THF (7 mL) was added and stirred overnight at room temperature. The reaction mixture was diluted in diethyl ether and dried over MgSO4, followed by a filtration over Celite®. The solution was concentrated to yield the crude.