Endo-Selective Enyne Ring-Closing Metathesis Promoted by Stereogenic-at-Mo Monoalkoxide and Monoaryloxide Complexes. Efficient Synthesis of Cyclic Dienes Not Accessible throught Reactions with Ru Carbenes
Author(s)Lee, Yeon-Ju; Hoveyda, Amir H.; Schrock, Richard Royce
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Stereogenic-at-Mo monoalkoxide and monoaryloxide complexes promote enyne ring-closing metathesis (RCM) reactions, affording the corresponding endo products with high selectivity (typically >98:<2 endo:exo). All catalysts can be prepared and used in situ. Five-, six-, and seven-membered rings are obtained through reactions with enyne substrates that bear all-carbon tethers as well as those that contain heteroatom substituents. The newly developed catalytic protocols complement the related exo-selective Ru-catalyzed processes. In cases where Ru-based complexes deliver exo and endo products nondiscriminately, such as when tetrasubstituted cyclic alkenes are generated, Mo-catalyzed reactions afford the endo product exclusively. The efficiency of synthesis of N- and O-containing endo diene heterocycles can be improved significantly through structural modification of Mo catalysts. The modularity of Mo-based monopyrrolides is thus exploited in the identification of the most effective catalyst variants. Through alteration of O-based monodentate ligands, catalysts have been identified that promote enyne RCM with improved efficiency. The structural attributes of three Mo complexes are elucidated through X-ray crystallography. The first examples of catalytic enantioselective enyne RCM reactions are reported (up to 98:2 enantiomer ratio and >98% endo).
DepartmentMassachusetts Institute of Technology. Department of Chemistry
Journal of the American Chemical Society
American Chemical Society (ACS)
Lee, Yeon-Ju, Richard R. Schrock, and Amir H. Hoveyda. “Endo-Selective Enyne Ring-Closing Metathesis Promoted by Stereogenic-at-Mo Monoalkoxide and Monoaryloxide Complexes. Efficient Synthesis of Cyclic Dienes Not Accessible through Reactions with Ru Carbenes.” Journal of the American Chemical Society 131, no. 30 (August 5, 2009): 10652-10661.
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