Application of dendrimer encapsulated Pd nanoparticles in carbon-carbon coupling reaction (the Stille reaction)
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This thesis examines the chemistry and application of dendrimer-encapsulated Pd nano-partilces in carbon-carbon coupling reactions in homogenous solution. We prepare our dendrimer encapsulated Pd nano-particles and study their catalytic properties and, also we try to study the nanoparticles during the catalytic process. Pd nanoparticles are synthesized by mixing together the dendrimer and Pd ion solution and then chemically reducing the composite, resulting in dendrimer-encapsulated Pd nanoparticle that can be used as catalysts. We report that dendrimer-encapsulated Pd nanoparticles having a diameter of [sim symbol -varies with or similar to]1.7 nm are effective and general catalysts for coupling aryl halides to organostannanes (the Stille reaction) under mild conditions. The significant results of this study are that the Stille reaction is catalyzed by dendrimer encapsulated Pd nanoparticles in very good yield, in aqueous solution at 23 °C, and using only 0.100 atom % of Pd as catalyst. A bulky substrate consisting of a large molecular "stopper", (Mono-(6-p-iodoaniline)-[Beta symbol]-cyclodextrin), a reactive probe, and a linker, was designed as an in-situ probe for determining whether the Stille reaction takes place inside or outside of the dendrimer. We expect that if the Stille reaction occurs outside the dendrimer no product will form because the bulky substrate is unable to enter the dendrimer. However, if some Pd is present in solution (not associated with the dendrimer) then the bulky substrate will participate in the Stille reaction.