Cinchona Alkaloids-Based Squaramide Catalyzed Asymmetric Additions Ofα-Aryl Isocyanoacetates To Maleimides

This thesis mainly focused on cinchona alkaloids-based squaramide catalyzed the Michael addition reactions of α-aryl isocyanoacetates to maleimides and the asymmetric formal [3+2] cycloaddition reaction of α-aryl isocyanoesters with maleimides by bifunctional cinchona alkaloids-based squaramide/AgSbF6cooperative catalysis.A series of squaramide catalysts derived from cinchona alkaloid and chiral cyclohexanediamine were employed in the asymmetric Michael addition reactions of α-aryl isocyanoacetates to maleimides. It was found that I-3h and I-3s were the best organocatalysts, and the corresponding adducts were obtained in excellent yields (up to99%), excellent diastereoselectivities (up to>20:1dr) and good to excellent enantioselectivities (76%-94%ee). The electronic and stric properties of the substituents on the α-aryl isocyanoesters and maleimides were examined and the plausible transition model was proposed.In addition, the asymmetric formal [3+2] cycloaddition reaction of α-aryl isocyanoesters with maleimides had also been investigated by bifunctional cinchona alkaloids-based squaramide/Ag1salt cooperative catalysis. The corresponding products were obtained in excellent yields (up to98%), excellent diastereoselectivities (up to>20:1dr) and excellent enantioselectivities (up to94%ee) by using cinchonine derived squaramide Ⅱ-3i and AgSbF6cooperative catalysis. The electronic and steric properties of the substituents on the α-aryl isocyanoesters and maleimides were examined and the absolute configuration of adducts was determined by X-ray diffraction as (1R,3aS,6aR)-configuration. Based on the above results and generally accepted mechanism, a plausible transition state mode was proposed.