Immobilization Of The Functionalized MacMillan Catalyst On Silla Gel And Its Application In Enantioselective Diels-Alder Reaction

This dissertation consists of two parts: 1) synthesis of functionalized MacMillan chiral amine catalysts, 2) immobilization of the functionalized MacMillan chiral amines on silica gel and its application in the enantioselective Diels-Alder reaction.Twelve functionalized MacMillan chiral amine catalysts were synthesized at first. Using the Diels-Alder reaction between (E)-cinnamaldehyde and cyclepentadiene as a model, the catalytic activity and enantioselectivity of these fuctionalized chiral amines were evaluated. With 10% catalyst loading, the Diels-Alder adduct was obtained in moderate yield and excellent enantioselectivity (84%-92% yield, 85%-95%ee). Among these chiral amines, 4c performed best (86% yield, 94%,95%ee). The aryl moiety, in stead of the nitrogen atom of amide group orientating away from catalytically active site, is identified as the suitable site for introduction of the support.The functionalized MacMillan catalysts with aryl group bearing free amine group were selected as the precursor for immobilization on silica gel. The polyleucine tag for immobilization of the catalyst was introduced by an amine-initiated polymerization of N-carboxy-anhydride of L-leucine. The polymerization degree of the polyleucine tag displayed significantly influence on the performance of the immobilized catalysts with immobilized catalyst 8 (n = 5) giving the best result (91% yield, 91% 93% ee). Separation and recovery of the polyleucine-tagged, silica-supported MacMillan catalyst could be effected by simply change of solvents and filtration while preserving comparable enantioselectivity to the parent MacMillan catalyst in the model reaction, asymmetric Diels-Alder cycloaddition of cyclopentadiene with cinnamaldehyde.The immobilized catalyst could be recycled with only a slight loss of efficiency. In fact, after 8 times of recycling the immobilized catalyst 8 still gave Diels-Alder adduct in the model reaction in 90% yield, 89 and 88% ee for endo and exo isomers, respectively.