Water → (E)-1-Chloro-2-propenylbenzene

48 ml of 2-chlorobenzenaldehyde (0.42 mol) and 49.7 ml of 3-pentanone (0.47 mol) were dissolved in 600 mL of hexane in flask, and then stirred with raising the temperature. 53.6 ml of Boron trifluoride etherate (BF3OEt2, 0.42 mol) was added to the resultant under reflux conditions. When the reaction was completed, water was added thereto. After layer separation, the obtained organic layer was washed twice with 1M sodium hydroxide solution (1M NaOH), and then the separated organic layer was washed with water. The separated organic layer was dehydrated with anhydrous magnesium sulfate (MgSO4) and concentrated. The concentrated residue was purified by a silica gel column chromatography to produce the title compound (38 g, yield 58%). 1H NMR (400 MHz, CDCl3) δ1.94 (d, J=4.8 Hz, 3H), 6.24 (m, 1H), 6.78 (d, J=14 Hz, 1H), 7.11˜7.51 (m, 4H)