Synthesis of E-alpha,beta-unsaturated ketones with complete stereoselectivity via sequential aldol-type/elimination reactions promoted by samarium diiodide or chromium dichloride

摘要

E-alpha,beta-Unsaturated ketones can be obtained with complete E-selectivity by a sequential reaction of dichloroketones with a variety of aldehydes. This transformation was promoted by SmI2, SmI2 in the presence of FeCl3 or CrCl2. The best results were obtained when CrCl2 was used as the metallating agent. A mechanism based on a successive aldol-type reaction and a beta-elimination is proposed to explain these results.