Studies On The Synthesis Of A Chiral Small Organic Molecular Ligand With A C₃-Symmetry Axis And Its Application In The Reduction Of Prochiral Ketones

This dissertation concerns the studies on the synthesis of a chiral small organic molecular ligands with a C₃-symmetry axis starting from L-proline and its application in the asymmetric borane-mediated reduction of prochiral ketones.It mainly consists of the following three parts:The first part is about the study on the application of C₃ symmetry in asymmetric catalysis and chiral recognition.C₃ symmetry is a fascinating subject not only in visual art,but also in other subjects,especially in chemistry.The chemists from all over the world has paid much attention to C₃ symmetry,especially in asymmetric catalysis and chiral recognition.In this part,it concerns the basic concept and development process of C₃ symmetry,the synthesis of many C₃-symmetric ligands and thei application in asymmetric catalysis and chiral recognition.The second part is about the study on the borane-mediated reduction of prochiral ketones.After the aminoalcohol was successfully used in the borane-mediated reduction of prochiral ketones by Corey et al,the research focuses on the synthesis of novel,chiral, aminoalcohol ligands and their application in the asymmetric reduction using chiral 1,3,2-oxazaborolidines as catalysts.In this part,We mainly reviews and discusses the borane-mediated reduction of prochiral ketones.The third part is about the synthesis of a C₃-symmetric chiral sulfonamide ligand and its application in borane-mediated reduction of prochiral ketones.We synthesized a C₃-symmetric chiral sulfonamide ligand with a high yield by five steps,which derived from natural L-proline.Very high enantiometric excesses (up to 97%ee)were obtained in the borane-mediated reduction of prochiral ketones. After the reaction was finished,we may recover the C₃-symmetric chiral sulfonamide ligand with a high yield and high purity only by simple extraction and washing process.The recycled ligand was reused four times and there was not any significant loss of catalytic activity.