A 500 mL round-bottom flask was charged with a stir-bar, AlCl3 (5.5 g, 41.2 mmol, 1 equiv.), and anhydrous CH2Cl2 (20 mL). The mixture was cooled to 0 °C using an ice-water bath. Freshly prepared (Z)-prop-1-en-1-ylmagnesium bromide solution (1 M in THF, 124 mL, 124 mmol, 3 equiv.) was added over a period of one hour, and the mixture was allowed to warm to room temperature over a period of 12 hours.