Chiral Cyclopentadienyl-Iron and -Ruthenium Lewis Acids Containing the Electron-Poor BIPHOP-F Ligand: a Comparison as Catalysts in an Asymmetric Diels-Alder Reaction

Chiral iron and ruthenium Lewis acids: analogies and differences between the catalysts and the role of the anion in catalytic Diels-Alder reaction. In short: Fe catalysts are faster but Ru analogues are more stable and can be recovered quantitatively. Rational ligand design is shown to result in a large increase in chiral induction.