Step 1: Preparation of allylsilane ether: add phenylacetone (1 g, 8 mmol) to a 50 mL two-necked flask, and cool the solution to 0 under nitrogen protection, then add 10 mL of anhydrous THF solution, then add lithium diisopropylammonium (2 mol/L, 4.2 mL) drop by drop to it, and when the addition is completed, remove the ice-water mixture used for cooling, and stir the solution at room temperature for 1 h. When the solution turns yellow, add trimethylchlorosilane (1.04 g, 9.6 mmol) to it drop by drop, and then add the lithium chlorotrimethylsilane (1.04 g, 9.6 mmol) to it. When the solution turned yellow, the reaction mixture was cooled to 0 again, to which trimethylchlorosilane (1.04 g, 9.6 mmol) was added dropwise with stirring at room temperature and detected by TLC until the end of the reaction. The solvent was removed by distillation under reduced pressure and the final oily liquid was separated by column chromatography (pure petroleum ether) to give product 1a (1.3 g, yield: 84%).
Step 2: Preparation of α-chloropropiophenone: To a 50 mL two-necked vial was added iodobenzene diacetate (2a) (0.244 g, 0.75 mmol) protected by nitrogen, then phenylpropiophenone enol silane (1a) (0.096 g, 0.5 mmol) and trimethylchlorosilane (3a) (0.108 g, 1 mmol) of MeCN (5 mL) solution was added to the system. The reaction system was allowed to stir at room temperature and detected by TLC until the reaction was complete. After removal of the solvent by distillation under reduced pressure, the residue was separated by column chromatography [V(petroleum ether):V(ethyl acetate) = 10:1]. Final isolation gave the product 4l (α-chloropropiophenone) as a colorless liquid in 84% yield.
