Highly Z- And Enantioselective Ring-opening/cross-metathesis Reactions Catalyzed By Stereogenic-at-mo Adamantylimido Complexes

摘要

In spite of impressive advances accomplished during the past two decades, a number of unresolved issues limit the utility of catalytic olefin metathesis reactions. A notable shortcoming is the lack of methods that selectively furnish Z alkenes. Nearly all ring-opening/ cross-metathesis (ROCM) reactions catalyzed by Mo or Ru complexes afford E olefins exclusively or predominantly. Only when the cross partner bears an sp-hybridized substituent (acrylonitrile or an enyne) are Zalkenes, at times, favored. Effective solutions to the above critical problem require the development of structurally distinct catalysts. Herein, we present an approach to catalytic enantioselective ROCM processes that delivers Z olefins exclusively (>98:<2 Z/E) or with high selectivity (≥87:13 Z/E) in 50-85% yield and up to >98:<2 enantiomer ratio (er). These transformations are promoted by <2 mol % of a chiral stereogenic-at-Mo complex.