DEVELOPMENT OF EFFECTIVE CHIRAL LIGANDS FOR CATALYTIC ASYMMETRIC HYDROGENATION
Open Access
- Author:
- Zhang, Weicheng
- Graduate Program:
- Chemistry
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- February 16, 2009
- Committee Members:
- Prof Xumu Zhang, Dissertation Advisor/Co-Advisor
Xumu Zhang, Committee Chair/Co-Chair
Scott Trent Feldman, Committee Chair/Co-Chair
Steven M Weinreb, Committee Member
Gong Chen, Committee Member
Qing Wang, Committee Member - Keywords:
- hydrogenation
asymmetric
catalysis
ligand
rhodium - Abstract:
- This thesis summarizes the author’s graduate research on catalytic asymmetric hydrogenation at Penn State. The first chapter gives a brief review of ligand development in asymmetric hydrogenation, with a focus on the long-term effort of the Zhang group in this area. Several important factors for ligand design are discussed, including steric hindrance, electronic control, and practical considerations. Chapter 2 delineates the development of a novel triphosphorus bidentate phosphine-phosphoramidite ligand with pseudo C2-symmetry, from initial design, through ligand synthesis and characterization, to its application in asymmetric hydrogenation. A major success of this ligand is highlighted in asymmetric hydrogenation of ortho substituted á-arylenamides with excellent enantioselectivity (up to 99.6% ee), which had not been possible prior to this work. In Chapter 3, the development of conformationally rigid spirocyclic monodentate phosphoramidite ligands is discussed. A highly efficient, large-scale route for the synthesis of chiral spirocyclic diol is presented, followed by the discovery of an interesting acid-mediated rearrangement of spirocyclic backbones. These spirocyclic ligands are applied in highly enantioselective catalytic asymmetric hydrogenation and asymmetric conjugate addition reactions.