Palladium Deposited on Naturally Occurring Supports as a Powerful Catalyst for Carbon-Carbon Bond Formation Reactions

Palladium catalysts supported on different inorganic materials have been reported to catalyze C-C bond formation reactions and extensive review articles are available in the literature considering this issue. However, in order to increase the capacity of the supports to bind palladium as the active catalyst, the surface of a large number of solids has been modified with organic moieties. The negative aspects of these modifications are that they are time-consuming and sometimes tedious procedures. In addition, they increase the cost of the reactions which is not desirable in economic point of view. On the other hand, naturally occurring organic solids which are inexpensive, available and abundant in nature are good alternative to inorganic supports despite their relatively lower thermal stabilities. The surface of these solids fully covered by chelating groups and often the surface modifications are not needed. In a recent perspective article, the application of palladium supported on polysaccharides in coupling reactions has been reviewed by Molnar and Papp. In the present review, we have focused our attention to the endeavors utilizing palladium particles supported on natural organic solids for the construction of C-C bonds by Mizoroki-Heck, Sonogashira- Hagihara, Suzuki-Miyaura and homocoupling reactions which are the most important palladium-catalyzed reactions.