Bis-(2,5-diphenylphospholanes) with sp2 carbon linkers: synthesis and application in asymmetric hydrogenation

J Org Chem. 2008 Feb 1;73(3):775-84. doi: 10.1021/jo7014938. Epub 2007 Oct 19.

Abstract

Four chiral diphosphine ligands consisting of bis(2,5-diphenylphospholan-1-yl) groups connected by the sp(2) carbon linkers 2,3-quinoxaline ((S,S)-Ph-Quinox), 2,3-pyrazine ((S,S)-Ph-Pyrazine), maleic anhydride ((S,S)-Ph-MalPhos), and 1,1'-ferrocene ((S,S)-Ph-5-Fc) were synthesized, and their cationic [rhodium(I)(COD)] complexes were prepared. These complexes were tested in asymmetric hydrogenation of functionalized olefins. [((S,S)-Ph-Quinox)Rh(COD)]BF4 showed high activity and selectivity against itaconate and dehydroamino acid substrates. The corresponding (S,S)-Ph-Pyrazine and (S,S)-Ph-MalPhos complexes exhibited lower activities and selectivities. [((S,S)-Ph-5-Fc)Rh(COD)]BF4 showed high activity with low selectivity for these substrates, but high activity and selectivity against 2-C-substituted cinnamate salts, whereas rhodium complexes of (S,S)-Ph-Quinox and (R,R)-Ph-BPE showed low activity and selectivity against 2-C-substituted cinnamate salts.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbon / chemistry*
  • Catalysis
  • Cinnamates / chemistry
  • Cross-Linking Reagents / chemistry*
  • Hydrogenation
  • Ligands
  • Magnetic Resonance Spectroscopy
  • Maleic Anhydrides / chemistry
  • Models, Molecular
  • Molecular Structure
  • Phenol / chemical synthesis
  • Phenol / chemistry*
  • Phosphorus / chemistry*
  • Pyrazines / chemistry
  • Quinoxalines / chemistry
  • Rhodium / chemistry
  • Stereoisomerism
  • Succinates / chemistry

Substances

  • Cinnamates
  • Cross-Linking Reagents
  • Ligands
  • Maleic Anhydrides
  • Pyrazines
  • Quinoxalines
  • Succinates
  • cinnamic acid
  • Phosphorus
  • Phenol
  • Carbon
  • Rhodium
  • itaconic acid