PVP-stabilized palladium nanoparticles as catalysts in Stille and Heck reactions in aqueous medium

GARCIA CAROLINA SOLEDAD; UBERMAN PAULA MARINA; MARTIN SANDRA E.

Foz do Iguaçu

Congreso; CLAFQO-12 12a Conferencia Latinoamericana de Físico-Química Orgánica 12th Latin American Conference on Physical Organic Chemistry; 2013

  Transition-metal nanoparticles (NPs) have become of increasing scientific interest due to their particular physical and chemical properties and their diverse application fields. An important field of application for NPs is that of catalysis as a result of their extremely small size and high surface-to-volume ratio.1 A variety of PdNPs with high activity, stability and recyclability have been used as catalyst in C-C coupling reactions.2 Recently, we developed a high reproducibility, simple and fast methodology to obtain PVP-stabilized PdNPs by direct electroreduction of H2PdCl4 in aqueous solution containing PVP. The catalytic activity of as-prepared PVP-stabilized PdNPs was evaluated in the Suzuki-Miyaura coupling reaction of aryl halides in aqueous medium.3 The PdNPs exhibited an outstanding catalytic activity for the Suzuki-Miyaura coupling reaction under mild conditions, with remarkably high turnover numbers (TON up to 104 to 105), and they could be reused at least for five cycles, without loss of activity.In order to extend the scope of this PVP-PdNPs; herein we report the results of the performance of the PVP-PdNPs in the Stille and Heck reactions using aryl iodides and bromides in aqueous medium (Figure 1). The use of water as a reaction medium for Pd-catalyzed reactions is very attractive for organic synthesis, due to environmental, economical, and safety reasons. The effect of different substituent in the aryl halide, additives and temperature in the catalytic activity of the PVP-PdNPs was investigated. They exhibited a great catalytic activity for this coupling reaction under mild conditions in an environmental friendly solvent system, with high turnover numbers and the corresponding products could be obtained in very good yields. 1 Astruc, D.; Lu, F.; Ruiz Aranzaes, J. Angew. Chem. Int. Ed. 2005, 44, 7852.2. Molnár, Á. Chem. Rev. 2011, 111, 2251.3. Uberman, P. M.; Perez, L. A.; Lacconi, G. I; Martín, S. E.; J. Mol. Catal. A: Chem. 2012, 363-364, 245