Solid support catalysts Stille reactions

While drawn by surface forces to the interface, the catalyst complex is still free to take up a configuration that is most favorable to the reaction. Thus, compared to a solid-supported catalyst, it will function more like a homogeneous catalyst and show more of the latter s characteristic features, namely, high reactivity, selectivity, and reproducibility under mild reaction conditions. Moreovo, because the catalyst complex is in a dissolved state, the reaction mixture may also be easier to han e than the slurry counterpart that would result from the use of a solid-supported catalyst. 

A general tendency for the three methods lies in the need to raise the Pd ratio up to 5-10% in order to avoid a too long reaction time. Nevertheless, the continuing search for new solid supports, linkers or palladium catalysts will ensure the development of the supported Stille coupling reaction . 

Much work is still in progress to improve the Ru-carbene complexes. Considerable attention has recently also been directed at efforts to immobilize a Ru-based metathesis catalyst on solid supports, which could make the metathesis reaction even more attractive for industrial applications. 

During the past 20 years, solid-supported organic catalysts have become powerful synthetic tools readily available to the chemical community. The reasons for developing an immobihzed version of a chiral catalyst go weU beyond the simple-yet still fundamental-aspect of the recovery and recycling of the precious catalytic species. Catalyst stabihty, structural characterization, catalytic behavior, new or different solubihty properties, simphfication of the reaction work-up, catalyst discovery and optimization, use in environmentally friendly or green solvents are all issues that may be converhently addressed working with supported systems. 

In the alkylation section, it was stated that the immobilized ionic liquids can combine the advantage of green media with solid support materials, which may enable the wide apphcation of precious ionic hquids by the reduchon of usage and also realize the sustainability of the chemical reaction process. The supported ionic hquids (SlLs) catalysts commonly employ the supports such as the macroporous polymer, metal oxide (SiO, AI2O3, etc.), zeohte, clay, and achve carbon, and after the immobilization of the ionic hquids, the ionic hquids still maintain their special solvent effect. Presently, the immobilized ionic hquids have been applied extensively to the alkylation, acylation, hydroformylation, oxidation, esterihcation, hydrolyza-tion, hydrogenahon, and other unit reactions this part of the chapter only discusses the application of immobilized ionic hquids to the acylahon. 

Since the renaissance of solid-phase organic chemistry in 1992, carbon-carbon bond formation reactions on solid support have probably been the best studied reactions. Many different facets of the Suzuki, Heck and Stille reactions have been evaluated. The influence of linkers, catalyst, solvents, microwave, polymer-bound aryl halides or polymer-bound arylboronic acids (or stannanes) have been studied in detail. 

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