title: Z- and enantioselective ring-opening/cross-metathesis with enol ethers catalyzed by stereogenic-at-Ru carbenes: reactivity, selectivity, and Curtin-Hammett kinetics.
abstract: The first instances of Z- and enantioselective Ru-catalyzed olefin metathesis are presented. Ring-opening/cross-metathesis (ROCM) reactions of oxabicyclic alkenes and enol ethers and a phenyl vinyl sulfide are promoted by 0.5-5.0 mol % of enantiomerically pure stereogenic-at-Ru complexes with an aryloxy chelate tethered to the N-heterocyclic carbene. Products are formed efficiently and with exceptional enantioselectivity (>98:2 enantiomer ratio). Surprisingly, the enantioselective ROCM reactions proceed with high Z selectivity (up to 98% Z). Moreover, reactions proceed with the opposite sense of enantioselectivity versus aryl olefins, which afford E isomers exclusively. Preliminary DFT calculations in support of Curtin-Hammett kinetics as well as initial models that account for the stereoselectivity levels and trends are provided.
authors: Department of Chemistry, Merkert Chemistry Center, Boston College, Chestnut Hill, Massachusetts 02467, United States.
authors: R Kashif M
authors: RK
authors: Khan
authors: Robert V
authors: RV
authors: O'Brien
authors: Sebastian
authors: S
authors: Torker
authors: Bo
authors: B
authors: Li
authors: Amir H
authors: AH
authors: Hoveyda