Dmitry Tsvelikhovsky - On the Involvement of Palladium Nanoparticles in the Heck and Suzuki Reactions

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  Dmitry Tsvelikhovsky,[a] Inna Popov,[b] Vitaly Gutkin,[b] Alina   Rozin,[a] Azariya Shvartsman,[a] and Jochanan Blum*[a]


  Eur. J. Org. Chem. 2009, 98–102





  We describe two different pathways by which palladium-cat- alyzed   Heck and Suzuki coupling reactions take place. When sol–gel   entrapped palladium acetate was used as a catalyst, the reactions   proceed by the formation of metallic nanopar- ticles. Such   particles were already formed during the immo- bilization of the   palladium salt. Upon application of palla- dium derivatives of   proline, tyrosine, or alanine, either in their homogeneous or in   their sol–gel entrapped version, no Pd0 particles could be   detected, even when the couplings were carried out in boiling   mesitylene (161 °C) or during prolonged reaction periods (48 h).   The reactions in the presence of the amino acid derivatives   proceeded at a higher rate than those by the entrapped palladium   acetate. The existence of palladium nanoparticles was   investigated with the aid of high-resolution scanning   transmission electron microscopy equipped with energy dispersive   X-ray spectroscopy, as well as by X-ray photoelectron   spectroscopy.


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