title: Chiral Cationic Cp(x)Ru(II) Complexes for Enantioselective Yne-Enone Cyclizations.
abstract: The cyclopentadienyl (Cp) group is a ligand of great importance for many transition-metal complexes used in catalysis. Cationic CpRu(II) complexes with three free coordination sites are highly versatile catalysts for many atom-economic transformations. We report the synthesis of a family of Cp(x)Ru(II) complexes with chiral Cp ligands keeping the maximum number of available coordination sites. The cationic members are efficient and selective catalysts for yne-enone cyclizations via formal hetero-Diels-Alder reactions. The transformation proceeds in <1 h at -20 °C and provides pyrans in up to 99:1 er. Unsaturated ester or Weinreb-amide substrates directly yield the iridoid skeleton.
authors.affiliation: Laboratory of Asymmetric Catalysis and Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Kossler
authors.affiliation: Laboratory of Asymmetric Catalysis and Synthesis, Institute of Chemical Sciences and Engineering, Ecole Polytechnique Fédérale de Lausanne (EPFL) , CH-1015 Lausanne, Switzerland.
authors.forename: Nicolai
authors.initials: N
authors.lastname: Cramer