Pd/Al(OH)3 Nanopaticles-catalyzed Stille Cross-coupling Reactions Of Aryl Halides

The biaryls have become extremely useful chemical intermediates in organic synthesis.They have been widely applied in a wide range of pharmaceuticals,natural products,polymers,and liquid crystal materials.Thus,the synthesis and preparation of biaryls has been very significant.Moreover,the development of the new synthetic methods of biaryls is gradually more and more important.The Stille cross-coupling reactions have evolved as a reliable method to synthesize biaryls.It was reported that in this paper the Stille cross-coupling reactions of tributylphenyltin with aryl halides were catalyzed by palladium nanoparticles which was prepared through one-pot three-component method.Next,a variety of aryl halides were examined for the cross-coupling reactions under optimized conditions.Aryl iodides and bromides gave products in good to excellent yields,however,somewhat sluggish yields were obtained when aryl chlorides were used as the substrates.The reaction conditions were optimized focused on the Pd loading,solvent,solvent dose and temperature.After all these extensive experiments,it was discovered that when reactions were performed on a 0.2 mmol scale of tributylphenyltin,the optimal conditions employed 0.3 mol%Pd and 1.0 equiv.of iodobenzene in 1.0 mL DMF at 70 ? for 24 h which provided biphenyl in 99%isolated yield.It was shown that whatever the electronic and the steric nature of the cross-coupling partners,most of the reactions gave products in good to excellent yields.In this paper,the products were determined by TLC,IR,1H NMR.The advantages of this method included:(1)easily available,high activity(2)ligand-free.Therefore,this research provides a reference value for our future commercial application.