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Preparation of Enantiopure Non-Activated Aziridines and Synthesis of Biemamide B, D, and epiallo-Isomuscarine
Published on: June 13, 2022
Optically active (aR)- and (aS)-linear and vaulted biaryl ligands: deracemization versus oxidative dimerization.
Gang Hu1, Daniel Holmes, Brina Fay Gendhar
1Department of Chemistry, Michigan State University, East Lansing, Michigan 48824, USA.
Journal of the American Chemical Society
|September 17, 2009
Summary
Copper-mediated deracemization of VANOL and VAPOL ligands revealed an unexpected oxidative dimerization. A refined procedure effectively generates BINOL with high optical purity, highlighting ligand steric effects.
Area of Science:
- Organic Chemistry
- Asymmetric Synthesis
- Catalysis
Background:
- Biaryl ligands are crucial in asymmetric catalysis.
- Deracemization offers an efficient route to enantiopure compounds.
- Copper-mediated processes are widely used in organic synthesis.
Purpose of the Study:
- To investigate the copper-mediated deracemization of C2-symmetric vaulted biaryl ligands (VANOL and VAPOL).
- To uncover and characterize novel reaction pathways, including oxidative dimerization.
- To develop a reliable procedure for generating enantiopure biaryl ligands.
Main Methods:
- Copper-mediated deracemization reactions.
- Structural elucidation using Nuclear Magnetic Resonance (NMR) spectroscopy.
- Supportive spectroscopic techniques and chemical reactivity studies.
Main Results:
- An unprecedented oxidative dimerization of VANOL and VAPOL was discovered.
- The structures of the oxidative dimerization products were successfully elucidated.
- The new deracemization procedure efficiently produced BINOL with high optical purity.
Conclusions:
- Oxidative dimerization is specific to vaulted biaryl ligands like VANOL and VAPOL, not linear ones (BANOL, BINOL).
- The developed deracemization procedure is effective for generating enantiopure BINOL.
- Steric congestion in copper-diamine complexes influences optical purity, with VANOL and VAPOL showing higher purities than BINOL.
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