| Transition-metal catalyzed reactions have arisen as one of the most valuable synthetic methods since they often provide simple, economical and efficient ways to the synthesis of structurally complex compounds or molecules of great biological interests. Most particularly, transition-metal mediated asymmetric catalysis has attracted considerable amount of interests as it offers a highly practical access to enantiopure products that are of critical importance in the pharmaceutical or agrochemical industry.;Chiral ligands play an important role in developing highly efficient transition metal complexes for asymmetric catalysis. For nearly three decades, bidentate ligands bearing C2 symmetry have been the dominant choices in the field. Recently, with the successful applications in various asymmetric transformations, the newly designed chiral monodentate phosphorus ligands have re-emerged as valuable tools in asymmetric synthesis.;In our laboratory, we have developed a library of axially chiral 3,3'-disubstituted-5,5',6,6'-tetramethylbiphenyl-2,2'-diols. Based on these chiral biphenols, a library of monodentate phosphoramidite and phosphite ligands and a library of bidentate diphosphonite ligands have been designed and synthesized. The salient feature of these ligands is their fine-tuning capabilities that allow a practical combinatorial approach to finding the most efficient ligand for a particular asymmetric reaction.;To demonstrate the efficacy of the newly designed ligands, we will present an efficient synthesis of 1-vinyltetrahydroisoquinoline via a Pd-catalyzed intramolecular allylic amination using monodentate phosphoramidite ligands. The diphosphonite ligands were applied to a Pd-catalyzed intermolecular allylic amination reaction, the key step in the total synthesis of Strychnos Indole Alkaloids, which led to high enantioselectivity and chemoselectivity. Progress towards the enantiomeric synthesis of tricyclic core of Schulzeines using Pd-diphosphonite catalyzed intramolecular allyic amination as key step will also be presented. Mechanistic study of the catalytic system using 31P NMR and molecular modeling will be included as well. |
