Preparation Of Supported Palladium Catalysts And Their Catalytic Activity For Suzuki-Miyaura Reaction

Suzuki-Miyaura reaction has been widely used in many fields,such as nanomaterials,electronic technology and pharmaceutical engineering.In the past decade,the Suzuki-Miyaura reaction has provided an effective method and idea for the synthesis of intermediates of APIs and natural products.The advantage of the Suzuki-Miyaura reaction is that the reaction has a strong functional group tolerance,and the raw material is insensitive to oxygen and water and can be stably present in the air.Most of the catalysts used in the Suzuki-Miyaura reaction are homogeneous catalysts,but it is difficult to recycle and reuse for the catalysts after the reaction,resulting in waste of precious palladium and polluting the environment.Therefore,the study of the synthesis of recyclable heterogeneous catalysts is the main research trend of Suzuki-Miyaura reaction catalysts in recent years.Based on the above background,two different supported palladium catalysts,palladium-loaded porous anodic aluminum oxide film and diimine palladium-loaded graphene oxide?Pd/AAO@Al and Pd/?-diimine/GO?were prepared.The catalysts were characterized and applied to the Suzuki reaction,and the catalytic performance of the different catalysts was studied.The main research contents are as follows:1.The self-made porous anodized aluminum oxide?AAO?material was fabricated and the nano-palladium was formed in the pores of AAO by the preparation method of impregnation-pyrolysis.It was confirmed by the means of characterization such as SEM,TEM,XRD that nano-palladium was fixed in the pores of AAO.The results of catalytic Suzuki-Miyaura reaction showed that:with a catalyst content of 0.13mol%,it has excellent catalytic activity for Suzuki-Miyaura reaction,and has a wide substrate adaptability.It can synthesize a series of biphenyl compounds and can be recycled for more than five times.In addition,the catalyst also has catalytic activity for the 4-nitrophenol reduction reaction,and the complete catalytic reduction reaction takes only 7 minutes at room temperature.2.The graphene oxide?GO?was prepared by the modified Hummers method,and the?-diimine ligand was synthesized in two steps using a2,6-dimethylaniline starting material.For the first time,the ligand was successfully grafted onto the surface of GO and coordinated with palladium to form a Pd/?-diimine/GO catalyst.The GO modified by the?-diimine ligand not only facilitates coordination with palladium,but also has better dispersibility in an organic solvent,and is more favorable for improving catalytic activity.The morphology and surface structure of the prepared catalyst were characterized by SEM,TEM,IR,XPS,etc.The results confirmed that both the ligand and palladium were supported on the surface of GO.Pd/?-diimine/GO was used as a heterogeneous catalyst to study its catalytic performance for Suzuki-Miyaura reaction.The results show that the catalyst was subjected to Suzuki-Miyaura reaction to obtain a series of biphenyl compounds in a yield of 70%to 99%under the optimal reaction conditions?K₂CO₃ as the base,EtOH/H₂O=1:1 as the solvent,the catalyst amount is 0.018mol%,and the reaction temperature is 60�C?,in which a key intermediate of the Sartan drug was successfully synthesized,and the yield was as high as 97%.Moreover,even at a lower catalyst amount?0.0036mol%?,a yield of more than 90%can be obtained,and the catalyst can be recycled at least 6 times.The results also confirms that the catalyst has a better tolerance to the substrate functional group of the Suzuki-Miyaura reaction,and important functional groups such as-CHO,-NH₂,-COOMe,and-OH which can be further converted are also compatible.