Chiral Biferrocene-Based Bis(oxazolines): Ligands for Cu(I)-Catalyzed Asymmetric Cyclopropanations of Ene—Diazoacetates.

TL;DR: Chiral biferrocene-based bis(oxazolinyl)biferrocenes were found to be conformationally flexible and have a wide bite angle by NMR and molecular modeling studies as discussed by the authors.

Abstract: Chiral biferrocene-based bis(oxazoline) compounds, which have both planar and central chirality, are synthesized. The Cu(I)-complexes of the bis(oxazolinyl)biferrocenes were found to be conformationally flexible and have a wide bite angle (136°) by NMR and molecular modeling studies. The complexes catalyzed the intramolecular cyclopropanation reaction of ene-diazoacetates, and low to moderate enantioselectivities and decreased reactivity were observed, compared to known malonate-derived bis(oxazoline) systems.