Modified Graphite-supported Palladium Catalyst For The Suzuki-Miyaura Cross-Coupling Reaction Of 4-bromotoluene And Phenylboronic Acid

Palladium-catalyzed Suzuki cross-coupling reaction is one of the most important tools in organic synthesis due to its efficient construction of carbon-carbon bonds.During the preparation of the catalyst,the support plays an important role in dispersion and stability of the active metal while enhancing the catalytic performance of the active metal.Carbon materials are favored by researchers for their large surface area,stable physicochemical properties and adjustable surface groups.As catalyst supports,carbon materials are limited by their surface structure,especially their inherent oxygen-containing groups unable to provide sufficient sites for metal ions.Therefore,it is of great significance to develop effective catalyst support to disperse active metals and improve their catalytic properties.In this paper,graphite was used as the support,modified graphite was prepared by two different modification methods to prepare Pd-supported catalysts,and the catalyst of catalytic activity was studied by the Suzuki reaction of 4-bromotulene and phenylboronic acid.The details are as follows:?1?A serial of surfactant modified graphite-supported magnetic heterogeneous palladium catalysts?FeOx-Pd/G-?M1??were designed and synthesized via a facile sequential reduction strategy.The surface modified graphite containing S=O functional group?SDBS,SDS-SO₄and SDS-SO₃?were used as support.Under mild conditions,the FeOx-Pd/G-?SDBS?catalyst efficiently catalyzed the Suzuki reaction of 4-bromotoluene and phenylboronic acid reaction with conversion of 4-bromotoluene and the yield of 4-methylbiphenyl was 97%and 81%,respectively.The catalysts of physical-chemical property and magnetism were characterized by FT-IR,SEM-EDS,TEM,XRD and VSM.Importantly,the prepared FeOx-Pd/G-?SDBS?catalyst could easily be recovered by external magnetic field and 70%yield was achieved after 5 recycle tests.?2?Palladium catalyst?Pd/Gx-NH₂?M2??was successfully prepared by modified graphite with amino silane coupling agent?APTES?.The catalyst?Pd/Gx-NH₂?M2??was characterized by FT-IR,SEM-EDS,TEM and XRD.Under the same reaction conditions,the optimum catalyst preparation conditions:using 325 mesh graphite as the support,0.5 M HNO₃ to pretreatment graphite,toluene as the amino silane of solvent,and Na₂SO₃ as the reductant to prepare catalyst?Pd/G₁-NH₂?C₇H₈??,the yield of the product of 4-methyldiphenyl reached to 90%,the conversion of 4-brominetoluene was 98%.