An oven-dried 500 mL two-neck round-bottom flask was equipped with a magnetic stir bar and a reflux condenser. The flask was evacuated and backfilled with N2. Mg turnings (4.4 g, 183 mmol, 1.5 equiv.), a few crystals of iodine, and anhydrous THF (124 mL) were added. Next, Cis-1-bromo-1-propene (10.6 mL, 15.1 g, 125 mmol) was slowly added (Caution! There is a significant exotherm during Grignard reagent formation, which may lead to THF reflux). The mixture was stirred at room temperature for 6 hours.