The Preparation Of Hairy Nanoparticles Immobilized With Chiral Catalysts And Application In Asymmetric Aldol Reaction

The immobilized catalyst has received much attention, its advantages is high stability, extensivesuitability to solvents, easy separation and purification of product, lower environmental hazard, easyseparation recovery from reaction system and reuse, and so on. In this thesis, two new hairy silicananoparticles immobilized polymer chains with pendant chiral catalyst units had been synthesized bysurface-initiated reversible addition fragmentation chain transfer （SI-RAFT）. And the catalyst had beenused in direct asymmetric Aldol reaction reaction to investigate the performance of catalyst and the effectof recycling. The paper could be divided into two parts.The synthesis and characterization of hairy SiO₂nanoparticles immobilized polymer chains withpendant chiral catalyst units:（1） Synthesis and characterization of hairy silica nanoparticles immobilized with Poly（N-vinylphenylsulfonyl prolinamide）：First of all, we prepared vinyl benzene sulfonamide with vinyl benzenesulfonate by two-step, Then prepared polymerizable monomer N-vinyl phenylsulfonyl-Boc-L-prolinamideby reation with Boc-L-proline in THF，DCC as the condensing agent. RAFT chain revesible agent wasattached on the surface of silica nanoparticles, and hairy silica nanoparticles immobilized polymeric chainspoly （N-vinyl phenylsulfonyl-Boc-L-prolinamide） were obtained from surface of silica by surface-initiatedreversible addition fragmentation active radical polymerization （SI-RAFT） technical. Finally hairy silicananoparticles immobilized poly （N-vinyl phenylsulfonyl prolinamide） chains were achieved bydeprotection. The products were characterized by nuclear magnetic resonance （NMR）, IR spectra and TGA.（2） Synthesis and characterization of hairy silica nanoparticles immobilized with Poly[（S）-5-（4-acryloyloxy ethoxy benzyl）-2,2,3-trimethyl-4-Imidazolidin]: First of all, we prepared MacMillan chiralamine, namely,（S）-5-（4-acrinyl）-2,2,3-trimethyl-4-Imidazolidin with L-tyrosine by three-step, ThenCs₂CO₃as catalyst, preparation of polymerizable monomer （S）-5-（4-acryloyloxy ethoxy benzyl）-2,2,3-trimethyl-4-Imidazolidin by reation with hydroxyethyl acrylate activated by methanesulfonyl chloride inDMF. RAFT chain revesible agent was attached on the surface of silica nanoparticles, and hairy silicananoparticles linking polymeric chains with MacMillan chiral amine were obtained from surface of silica by surface-initiated reversible addition fragmentation active radical polymerization （SI-RAFT） technical.The chemical compounds and catalyst were characterized by nuclear magnetic resonance （NMR）, IRspectra and TGA.The application of hairy SiO₂nanoparticles immobilized polymer chains with pendant L-proline unitsin direct asymmetric Aldol reation:Hairy silica nanoparticles grafted with Poly （N-vinyl phenylsulfonyl prolinamide） was carried out indirect asymmetric Aldol reaction, and the performance of the catalyst was benchmarked in typical aldolreaction of p-nitrobenzaldehyde with acetone. The experiment results show that the catalyst in asymmetricAldol reaction of p-nitrobenzaldehyde with acetone perform better catalytic activity and enantioselectivity（73%yield and98%ee value） in optimized reaction conditions （DMF as solvent,20mol%catalytic amountand less then5℃）. Through simple centrifugation separation, catalyst can be duplicated.