Preparation Of Supported Chiral Monoamine Catalysts And Their Properties For Asymmetric Michael Addition Reaction

Chiral cinchonine-based squaramide, as one kind of important organocatalysts forcarbon-carbon bond formation reactions，has been investigated extensively in variousasymmetric reactions recently. In particular, cinchona-based squaramide organocatalystshave exhibit excellent enantioselectivity in asymmetric Michael addition of l?3-dicarbonylcompounds to nitroalkenes. More interestingly, cinchonine-substituted squaramide canaccelerate significantly asymmetirc Michael addition in brine reaction system, which is onthe verge of being applied in industry. However, due to complicate synthetic process andexpensive price of chiral cinchona-based squaramides, it is high desire to recycle theseligands.Taking advantage of imidazolium and CTATos phase-transfer function, we hadsynthesized two kinds of bifunctional catalysts and compared their catalytic performance:1-.CSFIBOIHS Taking advantage of imidazolium phase-transfer function，weincorporate conveniently chiral cinchonine-substituted squaramide organocatalyst ontoimidazolium-based organic-inorganic hybrid silica and construct a bifunctionalheterogeneous catalyst. As presented in this study, this catalyst displays excellent catalyticactivity and enantiosclcctivity in asymmetric Michael addition of1,3-dicarbonyl compoundsto nitroalkenes in brine. It is also found that the synergistic effect of imidazoliumphase-transfer function and confined site-isolated squaramide species significantly promotesthe catalytic performance.2.CSF-MSNs Taking advantage of CTATos phase-transfer function, we incorporateconveniently chiral cinchonine-substituted squaramide organocatalyst onto macroporoussilicon materials containing CTATos and construct a bifunctional heterogeneous catalyst. Aspresented in this study, this catalyst displays excellent catalytic activity andenantioselectivity in asymmetric Michael addition of1,3-dicarbonyl compounds tonitroalkenes in brine. It is also found that the synergistic effect of imidazolium phase-transferfunction and confined site-isolated squaramide species significantly promotes the catalyticperformance. The heterogeneous catalyst can be readily recycled and reused repeatedly for atleast ten times...