Efficient And Recyclable Palladium Nano-catalyst Is Used In The Study Of Methylpyrrole C2/C5 Diarylation Reaction In Aqueous Medium

In recent years,palladium-catalyzed direct arylation of pyrroles by catalytic C-H activation has been a great success.Compared with the traditional cross-coupling reaction,such reactions do not require pre-activation steps,which has a higher efficiency,atomic and process economy.In this paper,The highly efficient and recyclable mesoporous palladium-based catalysts were prepared.Nitrogen-doped mesoporous polymer supported palladium catalysts were used to catalyze the direct bisarylation of pyrrole with diphenyliodonium salt in aqueous medium.It is proved that Pd is the multiphase active center and the catalyst can be reused.This paper includes four chapters.The first chapter is the literature review,mainly introduces the research progress of the mesoporous materials,the modification methods,as well as the research status of metal Pd in the field of C-H activation.In the second chapter,Pd/ODDMA-MP supported on the quaternary ammonium salt-modified mesoporous polymer was used to catalyze the direct bisarylation of methylpyrrole with diphenyliodonium salt in aqueous medium.The reaction system conditions are mild?60 ^oC?,and no air removal or alkali or other additives are needed during the reaction.the catalytic conversion frequency?TOF?of Pd/ODDMA-MP was93 h^-1.The catalytic activity of the catalyst was confirmed by the hot filtration and mercapto trapping experiments.It was confirmed that the catalytic activity of the catalyst was obtained from the palladium nanoparticles immobilized on the carrier instead of the palladium in the reaction solution.Cyclic experiments were performed to demonstrate high stability and repeatability.The catalyst could be reused more than 6times.This is the first example of direct bisarylation of pyrrole catalyzed by a heterogeneous catalyst.In the third chapter,the high-order carbon-silica composite was used as the carrier,and the amine functional groups were modified on the surface.The Pd-N coordination was used to stabilize the Pd nanoparticles to obtain ordered mesoporous carbon-silica Supported Pd nanocatalyst.These catalysts have a large specific surface area?202-252 m²/g?,uniform pore size?5.3-6.3 nm?,high nitrogen content?1.7-2.0wt%?.The palladium nanoparticles are dispersed uniformly and have a particle size of 1.7-2.6 nm.The fourth chapter summarizes the full text.