Rate-Limiting Step of the Rh-Catalyzed Carboacylation of Alkenes: C鈥揅 Bond Activation or Migratory Insertion?

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• 作者：J. Patrick Lutz ; Colin M. Rathbun ; Susan M. Stevenson ; Breanna M. Powell ; Timothy S. Boman ; Casey E. Baxter ; John M. Zona ; Jeffrey B. Johnson
• 刊名：The Journal of the American Chemical Society
• 出版年：2012
• 出版时间：January 11, 2012
• 年：2012
• 卷：134
• 期：1
• 页码：715-722
• 全文大小：455K
• 年卷期：v.134,no.1(January 11, 2012)
• ISSN：1520-5126

文摘

Rhodium-catalyzed intramolecular carboacylation of alkenes, achieved using quinolinyl ketones containing tethered alkenes, proceeds via the activation and functionalization of a carbon鈥揷arbon single bond. This transformation has been demonstrated using RhCl(PPh₃)₃ and [Rh(C₂H₄)₂Cl]₂ catalysts. Mechanistic investigations of these systems, including determination of the rate law and kinetic isotope effects, were utilized to identify a change in mechanism with substrate. With each catalyst, the transformation occurs via rate-limiting carbon鈥揷arbon bond activation for species with minimal alkene substitution, but alkene insertion becomes rate-limiting for more sterically encumbered substrates. Hammett studies and analysis of a series of substituted analogues provide additional insight into the nature of these turnover-limiting elementary steps of catalysis and the relative energies of the carbon鈥揷arbon bond activation and alkene insertion steps.