Palladium Nanoparticles In Ionic Liquids Catalyzed Ullmann Reaction And Sonogashira Reaction

Ionic liquids(ILs) have emerged as important stabilizing and recyclable agents for metal nanoparticles(NPs), simultaneously avoiding the use of highly toxic solvents. Hence, transition metal NPs stabilized in ILs have been employed for hydrogenation, oxidation, C-C coupling reactions, and so on.Transition metal NPs catalyzed carbon-carbon formation reaction, for example Ullmann reaction, Suzuki reaction, Sonogashira reaction and Heck reaction, is one of the important reactions in modern organic synthesis. In the past three decades, the palladium-catalyzed carbon-carbon formation reaction played a key role in the synthesis of functional materials, pharmaceuticals, agrochemicals and natural products.Generally, the palladium-catalyzed carbon-carbon formation reaction requires the participation of ligand, amounts of catalyst and high reaction temperature. Ligand, catalyst and temperature indeed promote the development of carbon-carbon formation reaction, especially in the activation of inactivated aryl bromides or aryl cholorides. Recently, ligand-free, less dosage of catalyst, moderate temperature and ILs stabilized transition metal NPs catalytic system attracts attention due to its simpleness, high efficiency and greenness. In the basis of the research on the PdNPs@[Bmim] catalytic system, the catalytic performance of PdNPs@[Bmim]Lac catalyst in Ullmann and Sonogashira coupling reaction are reported in this thesis.The activity of PdNPs@[Bmim]Lac catalyst was tested by Ullmann reactions. The effect of bases, solvents, reaction temperature, time and amount of catalyst on reactions were all discussed in detail. It is found that PdNPs@[Bmim]Lac catalyst shows high efficiency and good functional group tolerance in the Ullmann reaction under the optimized conditions: aryl halide(1.0 mmol), 4 mol% Pd, CH3ONa(1.5 mmol), TBAB(1 mmol), PEG4000(1 g), H2O(3.0 mL), 100 ℃. Regardless of Aryl iodides bearing electron-donating(-CH3,-OCH3), electron-neutral(H), or electron-withdrawing(-F,-Cl) groups are all efficiently coupled with themselves to afford the desired products in good to excellent yields. In addition, the coupling reaction can be efficiently accomplished with bromobenzene bearing electron-donating(-CH3,-CH3O), the yields of the products can be as high as 98%. The catalyst can be used for four runs and retained its catalytic activity in the Ullmann reaction.The activity of PdNPs@[Bmim]Lac catalyst was tested by Sonogashira reactions. The effect of bases, solvents, reaction temperature, time and amount of catalyst on reactions were all discussed in detail. The PdNPs@[Bmim]Lac catalyst can also catalyze efficiently the phenyl iodides substituted with electron-withdrawing(-Br,-F,-Cl), electron-neutral group(H) or electron-donating groups(-OCH3,-CH3) coupling well with phenylacetylene and give the corresponding products of high yields under the optimized conditions of the Sonogashira: 0.5 mmol aryl halide, 0.75 mmol aromatic terminal alkyne, 0.01 mol% PdNPs@[Bmim]Lac, 1.5 mmol Na3PO4.12H2 O and 3.0 ml EtOH/H2O=2:1 at 80 ℃.The iodobenzene with electron-donating groups(-OCH3) is very active with alkynes such asphenylacetylene 4-methyl phenyl acetylene, 3-amino phenyl acetylene and 4-methoxy phenyl acetylene, the yields of the products were 100%. The catalyst can be recycled up to three consecutive times in the Sonogashira reaction.