Expedient Access to Optically Pure Atropisomeric-NHC Ruthenium Complexes for (Z)-Selective Asymmetric Ring- Opening Cross Metathesis

Optically pure ruthenium complexes containing atropisomerically stable N-Heterocyclic Carbene (NHC) ligands are described. Isolated in excellent optical purities (up >99.5% ee) by a successful preparative HPLC resolution on a chiral stationary phase, these catalysts demonstrate excellent enantioselectivities in asymmetric ring-opening-cross metathesis (AROCM) (up to 97:3 er). Additionally, an optically pure Z-stereoselective catechodithiolated complex was also synthesized in nearly quantitative yield (or in-situ generated), furnishing enantioenriched Z-AROCM products in excellent 99/1 Z/E ratio and high enantioselectivity (up to 96.5:3.5 er).