The Application Of Chiral Semi-aza-crown Ether Ligand In The Catalytic Asymmetric Michael Reaction

1. Asymmetric Micheal Addition Reaction of β,γ-Unsaturated α-Ketoesters with Cyclic DiketonesSix-membered oxygenated compounds are one of the most common natural product frameworks, which exhibit extensive array of biological and physiological activities, the Michael addition reaction of β, γ- unsaturated-α- asymmetric ketoester and 1,3- cyclohexanedione is a very efficient method. As a result, following the early pioneering work of J?rgensen and co-workers, the Michael addition reactions of cyclic 1,3-dicarbonyl compounds and b,g-unsaturated a-ketoesters have drawn intensive studies in recent three years, and a variety of synthetically and pharmaceutically useful chiral chromene derivatives are directly produced in excellent yields and stereoselectivities.As a well-developed bifunctional chiral catalyst, the Trost’s dinuclear zinc-Pro Phenol complex has demonstrated remarkable catalytic efficiency and stereoselectivity in asymmetric catalytic additions. Therefore, we explored the Michael addition reaction of 1,3-dicarbonyl compounds and b,g-unsaturated a-ketoesters with this ligand. In the presence of 5 mol% of L1 and 10 mol% of Et2 Zn, this asymmetric reaction shows the good yields(up to 96%) and good enantioselectivities(up to 96% ee) at 10 °C. 2. Asymmetric Addition Reaction of β,γ-Unsaturated α-Ketoesters with Formaldehyde tert-Butyl HydrazoneThe first time we have with metal catalyst on the reaction were studied. By screening we got the optimum conditions: the present reaction is best performed with10 mol% of L2 and 20 mol% of Zn Et2 in dichloromethane at 0℃. With the optimal reaction conditions achieved above, this asymmetric reaction shows the good yields(up to 97%) and good enantioselectivities(up to 98% ee).