Pd-catalyzed Allylic Substitution for Construction of Quaternary Stereocenters

Identifier:  TDX:3335

Handle: https://hdl.handle.net/20.500.11797/TDX3335

Authors:  Cai, Aijie

Abstract:
Since the early seminal work by J. Tsuji and B. M. Trost, there has been rapid progress in the development of chiral ligands and scope of the electrophiles and nucleophiles in Pd-catalyzed allylic substitution reactions over the past few decades. In addition, Pd-catalyzed asymmetric allylic substitution reactions have been applied in total synthesis of a variety of complex chiral molecules, providing solid evidence of the efficiency of this methodology in controlling both regio- and enatioselectivities. Despite the numerous advances realized, forging chiral branched allylic derivatives from simple and readily available starting materials continues to be an important task in synthetic chemistry, due to the potential of the allylic moiety for further elaboration and asymmetric synthesis. The building allylic scaffolds bearing quaternary stereocenters based on Pd-catalyzed allylic substitution still remain rather underexplored. In this thesis, we have develop a concise and efficient methodology for synthesis of chiral a,a-disubtituted allylic amines with high levels of regio- and enantioselectivity. And then, we unlocked the origin of the regio- and enantioselectivity in the unusual allylic amination by density functional theory (DFT) calculations in combination with mechanistic control experiments.Finally, we designed a novel and highly efficient ligand to mediate regio- and enantioselective synthesis of various chiral allylic sulfones featuring quaternary stereocenters. The utility of the method will be further demonstrated by the synthesis of the sesquiterpene (-)-Agelasidine A.