Preparation Of Supported Metal Compelx Catalysts And Their Application In The Oxidation Of Alkylaromatics

The oxidation of alkylaromatics is one of the most important and challenging transformations in modern organic chemistry,due to it's oxidative products play very important roles in organic synthesis,fine chemistry and medical intermediates.Traditional approaches for the reaction were based on stoichiometric reagents(potassium hypermanganate)oxidation,but the disadvantages of low products selectivity,high cost and environmental pollutions could not be avoided.In recent years,green oxidation of alkylaromatics is attracting continuous attention due to the development of oxidation technology.In this thesis,recent reviews aiming at the developments of catalysts for the oxidation of alkylaromatics are summerized,and several new supported metal complex catalysts are developed for the xidation of alkylaromatics.An amorphous silica supported cobalt complex was prepared via covalently grafting of silane functionalized cobalt Schiff base onto the surface of the silica through the hydroxyl group.It could effectively catalyze the oxidation of alkylaromatics combined with N-hydroxyphthalimide(NHPI).The catalytic system showed excellent activity in acetic acid using O2 as oxidant under mild conditions.The catalyst was simply recovered by filtration,and it could be used several times without significant loss of activity.The reaction was free radical reaction,and the radical intermediate(PINO)reacted with alkylaromatics to form alkyl peroxide,then decomposed to generate products by cobalt species.The silica coated Fe3O4 was chosen as the support,and functionalized by the interaction of the surface hydroxyl group with the aminosilane,and then a new type of magnetic nanoparticle supported copper Schiff base catalyst was obtained via condensation reaction with silane functionalized support and the Schiff base ligand.The oxidation of alkylaromatics to corresponding acetones with as-prepared catalyst using TBHP as oxidant under solvent free condition were investigated.The reaction could be well carried out under a low catalyst loading(0.45 mol%),and good to excellent conversions(78%-99%)and selectivities(90%-99%)were obtained.The catalytic system had good universality for a variety of substituents such as nitro,alkoxy and halo groups.During the reaction,the catalyst could be uniformly dispersed in the reaction system to form a quasi-homogeneous rather than the general heterogeneous reaction system,to avoid some of the defects of the heterogeneous load.The catalyst could be easily recovered by an external magnet and reused six times without remarkable loss of efficiency.Magnetic chitosan microspheres were prepared by surface adsorption using nano-iron tetraoxide particles as magnetic carrier,and then reacted with aldehydes to form Schiff base ligands,which were coordinated with manganese salts to prepare a novel magnetic nanoparticles supported manganese-chitosan Schiff base catalyst.The as-prepared catalyst showed good activity on the oxidation of alkylaromatics with TBHP under solvent free condition.Under the optimum reaction conditions,the conversion of alkylaromatic hydrocarbons could reach 77%-98%,and the selectivity of aromatic ketones in the oxidation products is above 85%.The catalytic system had good universality for a variety of substituents such as nitro,alkoxy and halo groups,especially when the catalytic oxidation of a substrate containing a plurality of benzene rings such as diphenylmethane and fluorene,more than 96%of conversions were obtained and the selectivity were up to 99%.The catalyst could be easily recovered by an external magnet and reused five times without significant loss of activity.The chloromethylated crosslinked polystyrene was chosen as support,and the methylpyrazole containing N ligand was grafted onto the surface of the carrier through the formation of C-N bond under alkaline condition.And then the polymer contaning N ligand reacted with molybdenum trioxide treated with hydrogen peroxid.A new type of organic polymer supported molybdenum complex catalyst was prepared and applied to the oxidation reaction of alkylaromatic hydrocarbons.In the absence of solvent conditions,the catalyst can effectively catalyze the oxidation of a series of alkyl aromatic hydrocarbons to the corresponding aromatic ketone with TBHP.Good to excellent conversion(75%-98%)of alkylaromatics were obtained under the optimum reaction conditions,and the selectivity of aromatic ketone in the product were above 85%.At the end of the reaction,the catalyst was separated by simple filtration,washed and dried,and could be reused many times with high catalytic activity.