The Immobilization Of Proline And Their Application In Assymetric Aldol Reaction In Water

Organocatalyst possessed unique advantages such as high efficient, mild reactionconditions, easy recycling and environmental benign is in line with the requirementsof the ideal catalyst for green chemistry. Especially, small organic molecules asasymmetric catalysts has become one of the most attractive research topic. Prolineand its derivatives as typical small organic molecule catalysts with superior catalyticperformance have been widely applied to the Aldol reaction, Mannich reaction,Michael addition reaction and other asymmetric carbon-carbon bond formationreactions. Recently, with the development of new catalytic reaction system, theimmobilization and recycling of proline have attracted extensive attention. This thesisis focused on the development of immobilized and reusable proline to achieve thecatalytic asymmetric Aldol reaction in aqueous media, including the following twoparts.Part I: A terpolymer P(POSS-St-Prol) containing L-proline, octavinyl polyhedraloligomeric silsesquioxane (Ov-POSS) and styrene blocks was synthesized viaconventional radical polymerization. Proline was successfully immobilized onto theorganic-inorganic hybrid materials to obtain a catalyst suitable for asymmetric Aldolreactions in aqueous media. The asymmetric Aldol condensation betweencyclohexanone and4-nitrobenzaldehyde catalyzed by P(POSS-St-Prol) wasunderwent smoothly with high yield (98%) and excellent stereoselectivity (99%, ee).Catalyst recycling experiments indicated that the catalytic performance ofP(POSS-St-Prol) is not significantly reduced after reused for5times.Part II: RAFT polymerization was successfully applied to the synthesis of aPhoto-sensitive supported catalyst containing L-proline,7-hydroxy-umbelliferone andpolyethylene glycol. The performances of the synthesized catalyst for the Aldolreaction between cyclohexanone and4-nitrobenzaldehyde in water was tested. Theresults showed that this catalyst before UV irradiation is able to achieve high yield(74%) and high stereoselectivity (96%, ee) for aqueous phase Aldol reaction. AfterUV irradiation, the yield and stereoselectivity were increased slightly, but notsignificantly. Although the synthesized catalyst does not achieve the desired catalyticperformance of intelligent optical response, it provides a reference for theimmobilization of proline.