The Carbon-carbon Coupling Reactions Catalized By Palladium Supported On Porous Organic Polymer

The palladium-catalyzed Suzuki-Miyaura and Sonogashira coupling reactions are very important and powerful methods for the construction of carbon-carbon bonds.Significant progress has been achieved using various homogeneous palladium catalysts.However,it is difficult to separate and reuse the expensive palladium catalysts and palladium species may also be a toxic contamination in the product in a homogeneous catalysis system.To overcome these issues,considerable efforts have been directed toward the development of the heterogeneous palladium catalysts.A successful example is that palladium nanoparticles(PdNPs)have been used for the formation of C-C bonds.It is a well-known fact that PdNPs without stabilization are prone to aggregate resulting loss of their catalytic activity.Therefore,looking for suitable support materials is still an attractive challenge in the field of heterogeneous catalysis.So far various solid materials,such as mesoporous silica,ionic liquids,polymers,metal oxides,inorganic-organic hybrid materials,and metal organic frameworks(MOFs)have also been successfully applied as catalyst supports,but less attention has been directed towards porous organic polymers(POPs).POPs are the promising solid platforms for heterogeneous catalysis due to their large surface area,low skeleton density and high thermal as well as chemical stability.Great efforts have led to the rapid development of various POPs with interesting structures and properties,but there is still a pressing requirement to improve their application in heterogeneous catalysis.This work describes the preparation of the PdNPs supported on a porous organic polymer(Pd/POP)and its characterization by TGA,SEM,PXRD,followed by its application in Suzuki-Miyaura and Sonogashira coupling reactions.The reaction conditions such as solvent,base and reaction temperature have been optimized.The suitable reaction conditions were applied to determine the electronic and steric effect on the reactivity of different substitutes.On the other hand,recyclability of the catalyst was also tested,and found that developed Pd/POP can catalyze Suzuki-Miyaura and Songashira reactions efficiently on extensive variety of substrates.The catalyst can be utilized upto third time without significant loss of activity.Futhermore,we prepared Pd2+/POP to study the differences of catalytic performance compared with Pd/POP.Finally,we found that Pd/POP is better than Pd2+/POP,as the particles size of Pd2+/POP is larger and easy to leach out during the reaction.