Synthesis Of Several Supported L-proline Derivative Catalysts And Their Catalytic Properties For Asymmetric Aldol Reaction Or Asymmetric Mannich Reaction

Supported asymmetric catalysts, as one of important branches of asymmetric catalysis,gain extensive attention of scholars these years. High performance small organic asymmetriccatalysts are supported on appropriate supporters. Not only does this strategy make the obtainedcatalyst re-usable, but it also lets the reaction system much simpler. Moreover, the production canbe obtained easier. L-Proline and its derivatives which had been found as a kind of effectiveasymmetric catalysts have been used for catalyzing asymmetric Aldol reaction, asymmetricMannich reaction, etc. Although kinds of supported L-Proline catalysts have been prepared, mostof them have drawbacks, such as low catalytic activity, high catalyst dosage. So the research aboutimmobilization of L-Proline is still a meaningful work. In this article, several supported L-Prolinecatalysts were prepared and used for catalyzing asymmetric Aldol reaction and Mannich reaction.1. Phenolic L-prolinamide was allowed to participate in enzymatic polymerization withhorseradish peroxidase as the catalyst generating immobilized L-prolinamide. The catalyticperformance of resultant polymer-supported L-prolinamide for direct asymmetric Aldol reactionbetween aromatic aldehyde and cyclohexanone was studied. Results show that as-preparedL-prolinamide can catalyze the aldol reaction at room temperature in the presence of H2O.Relevant aldol addition products are obtained with good yields (up to91%), highdiastereoselectivities (up to6:94dr) and medium enantioselectivities (up to87%ee). Moreover,the title polymer-supported catalyst can be recovered and reused for at least five cycles while theactivity remains almost unchanged. 2. L-Proline-L-Threonine peptide catalyst was grafted with Merrifield Resin generatingimmobilized catalyst. Obtained catalyst was used in asymmetric Aldol reaction. Reactionconditions, such as solvent, dosage of the catalyst, and the reusability of the catalyst were studied.Results showed that this catalyst could catalyze the asymmetric Aldol reaction. When Tween-20aqueous solution was used as solvent, the Aldol productions could be obtained with good yields(up to89%), medium diastereoselectivities (up to14:86dr) and medium enantioselectivities (up to78%ee). In additional, the catalyst possessed good reusability.3. DMAP or pyridine ionic liquid functional PVC was prepared and used to supportL-Proline. Then as-prepared catalyst systems were used to catalyze asymmetric Aldol reaction andasymmetric Mannich reaction. When trace H2O was added into the reaction system as addition, theAldol productions could be obtained with high stereoselectivity (up to9:91dr, up to97%ee).Moreover, the dosage of electrophile was only2equivalents. Results also showed that this kindcatalyst system could catalyze asymmetric Mannich reaction when NMP was employed as solvent.Mannich productions were obtained with medium stereoselectivity (up to6:94dr, up to80%ee).But catalytic activity and stereoselectivity of these catalyst systems decreased apparently whenthey were reused several times later.