| Transition metal palladium catalyzed carbon-carbon coupling reaction is an important means to construct C-C bond in organic chemistry,and it is also one of the hot issues in organic chemistry.The traditional carbon carbon coupling reaction requires the addition of organophosphine ligands and palladium.Organophosphine is sensitive to water and air,and usually requires the reaction under the condition of anhydrous and oxygen free.Moreover,the process has the disadvantages of expensive catalyst and difficult recovery,difficult separation of products and easy pollution by precious metals and environment pollution,which is not in line with the development of green chemistry.Therefore,the development of a recyclable and efficient palladium catalyst is an important research direction in organic synthesis.In organic synthesis,organic solvents are widely used because of their good solubility.Toxic and harmful organic solvents not only do harm to the environment,but also pose a threat to human health.Water is abundant in nature.It is cheap,non-toxic,safe and environmentally friendly.It is an ideal substitute of organic solvent for environmental protection.This paper is divided into two parts.One is to design and synthesize a recyclable magnetic nanoparticles supported palladium catalyst and apply it to the Suzuki coupling reaction under microwave irradiation.The other is to apply a water-soluble ligand to the carbon carbon coupling reaction in water under microwave heating.The details are as follows:1.The magnetic nano catalyst Pd SB-MNPs was designed and synthesized with magnetic nano-Fe3O4 as the framework and the coordination of Schiff base and palladium.The physicochemical properties of the catalyst were characterized by SEM,TEM,FTIR and XRD.The palladium content of the catalyst was determined by ICP-OES.The catalyst was used in microwave-assisted Suzuki coupling reaction to evaluate its catalytic performance.Through the screening of reaction conditions,the optimum reaction conditions were determined.The optimum reaction conditions were determined as follows:microwave power 320 W,1,4-dioxane: water = 1:1 as solvent,potassium phosphate as base,reaction temperature 80 ?,reaction time 20 minutes.The reaction substrate was expanded under the best reaction conditions,The results show that the activity of Suzuki coupling reaction catalyzed by the catalyst is affected by the electronic effect of the substrate.The presence of electron withdrawing substituents has high activity,while the presence of electron donating groups will reduce the activity of the reaction.At the same time,the steric hindrance has a certain effect on the reaction.The activity of ortho substitution is lower than that of corresponding para substitution.Under the action of external magnetic field,the catalyst can be sucked out from the reaction system.After washing and drying,the catalyst can be used in the catalytic cycle experiment.The catalyst can still maintain high catalytic activity after recycling for 5 times.At the same time,the reaction system was heated by microwave,the reaction time was very short,and the yield was 92% after 20 minutesThe water-soluble Salen-Pd complex was made in situ with mixture of N,N'-bis[(5-sulfonato-2-hydroxy)benzyl]-N,N'-dimethyl-ethane-1,2-diaminen and palladium acetate in water.This complex was used as catalyst for microwave-promoted Heck and Sonogashira coupling reaction.Through the screening of reaction conditions,the reaction conditions were determined.The best reaction conditions were determined by screening the reaction conditions.Heck reaction: potassium carbonate as base,tetrabutylammonium bromide as phase transfer catalyst,reaction temperature 100 ?,reaction time 8 minutes.Sonogashira coupling reaction: potassium carbonate as base,tetrabutylammonium bromide as phase transfer catalyst,reaction temperature 80 ?,reaction time 15 minutes.Under these conditions,the substrates of heck coupling reaction between bromobenzene derivatives and ethylene derivatives and Sonogashira coupling reaction between bromobenzene derivatives and acetylene derivatives were expanded.Under these conditions,the substrates of heck coupling reaction between bromobenzene derivatives and ethylene derivatives and Sonogashira coupling reaction between bromobenzene derivatives and acetylene derivatives were expanded.The results showed that both Heck reaction and Sonogashira coupling reaction showed good catalytic effect.The yield of Heck reaction was 93% in 8 minutes under microwave,and Sonogashira coupling reaction was almost complete in 15 minutes under microwave.The catalyst and product can be separated from each other by the method of separating the aqueous phase and the organic phase.The water phase was recycled for 4 times,and good yield was obtained in the first 3 times. |
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