title: Mild and efficient nickel-catalyzed Heck reactions with electron-rich olefins.
abstract: A new efficient protocol for the nickel-catalyzed Heck reaction of aryl triflates with vinyl ethers is presented. Mild reaction conditions that equal those of the corresponding palladium-catalyzed Heck reaction are applied, representing a practical and more sustainable alternative to the conventional regioselective arylation of vinyl ethers. A catalytic system comprised of Ni(COD)(2) and 1,1'-bis(diphenylphosphino)ferrocene (DPPF) in combination with the tertiary amine Cy(2)NMe proved effective in the olefination of a wide range of aryl triflates. Both electron-deficient and electron-rich arenes proved compatible, and the corresponding aryl methyl ketone could be secured after hydrolysis in yields approaching quantitative. Good functional group tolerance was observed matching the characteristics of the analogous Pd-catalyzed Heck reaction. The high levels of catalytic activity were explained by the intermediacy of a cationic nickel(II) complex potentially responsible for the successive β-hydride elimination and base promoted catalyst regeneration. Although these elementary reactions are normally considered challenging, DFT calculations suggested this pathway to be favorable under the applied reaction conditions.
authors: The Center for Insoluble Protein Structures (inSPIN), Department of Chemistry and the Interdisciplinary Nanoscience Center, Aarhus University, Langelandsgade 140, 8000 Aarhus, Denmark.
authors: Thomas M
authors: TM
authors: Gøgsig
authors: Jonatan
authors: J
authors: Kleimark
authors: Sten O Nilsson
authors: SO
authors: Lill
authors: Signe
authors: S
authors: Korsager
authors: Anders T
authors: AT
authors: Lindhardt
authors: Per-Ola
authors: PO
authors: Norrby
authors: Troels
authors: T
authors: Skrydstrup
mesh_terms: D000475:Alkenes / Q000737:chemistry*; D002384:Catalysis; D004583:Electrons; D009532:Nickel / Q000737:chemistry*; D011789:Quantum Theory
chemical_list: D000475:Alkenes; D009532:Nickel