Oxygen-Promoted Pd(II) Catalysis for the Coupling of Organoboron Compounds and Olefins
Young Chun Jung, Rajesh Kumar Mishra, Cheol Hwan Yoon and Kyung Woon Jung*
*Loker Hydrocarbon Research Institute and Department of
Chemistry, University of Southern California, Los Angeles, California
90089-1661, Email: kwjung
usc.edu
Y. C. Jung, R. K. Mishra, C. H. Yoon, K. W. Jung, Org. Lett., 2003, 5, 2231-2234.
DOI: 10.1021/ol034458s
Abstract
A mild and efficient Pd(II) catalysis leads to the formation of carbon-carbon bonds between various organoboron compounds and alkenes. The resultant Pd(0) species is reoxidized by molecular oxygen to Pd(II). This protocol promotes the desired Pd(II) catalysis, whereas the competing Pd(0) pathways (Heck or Suzuki) are retarded.
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proposed mechanism
Details
The document reports a mild and efficient Pd(II) catalysis method for forming carbon-carbon bonds between organoboron compounds and olefins, using molecular oxygen to reoxidize Pd(0) to Pd(II). This oxygen protocol promotes Pd(II) catalysis while suppressing competing Pd(0) pathways like Heck or Suzuki couplings. Organoboron reagents, which are less toxic and more stable than other organometallic reagents, are used for these reactions. The study shows that using oxygen significantly improves yields compared to air or nitrogen conditions. Various olefins and organoboron compounds were tested, demonstrating the method's versatility and high regioselectivity, particularly favoring (E)-isomers. The proposed mechanism involves transmetalation, migratory insertion, and β-hydride elimination, with oxygen reoxidizing Pd(0) to Pd(II). This environmentally friendly approach provides good to excellent yields and offers a new mechanistic concept for Pd(II) catalysis. The research was supported by the National Institutes of Health and highlights the potential for broader applications in organic synthesis.
K. S. Yoo, C. H. Yoon, J. W. Jung, J. Am. Chem. Soc., 2006, 128, 16348-16393.
Key Words
Boronic Acids, Esters, Coupling, Olefins, Alkenylation, Oxygen
ID: J54-Y2003-460
