Study on the Direct Functionalization of Nitrogen Heterocycles Catalyzed by Nitrogen-Doped Carbon Materials Supported Nanocobalts

Author:Xie Feng

Supervisor:zhang zuo

Database:Doctor

Degree Year:2019

Download:19

Pages:260

Size:20506K

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Catalytic technology is critical to the current renewable energy,environment and petro-chemical industries.Nitrogen-doped carbon supported base metal nanoparticles constitute new types of heterogeneous catalysts having the merits of high activity,stability,easy separation and recycling.The introduction of nanomaterials into catalytic field has injected new vitality to the development of green catalysis.The incorporation of electron-rich nitrogen in the carbon material is beneficial to increase the interaction between the metal and support,and the number of chemically active sites,anchor the metal particles,and prevent the metal from assembling or leaking.Nitrogen-containing heterocyclic compounds constitute important components of heterocyclic compounds,which exhibit a wide range of physiological and pharmaceutical activities.Further functionalization of N-heterocycles compounds to generate novel N-heterocycles molecules with structural diversity is of significant importance.Therefore,via a catalyst design strategy,the work in this thesis focused on the preparation of a series of nitrogen-doped carbon-supported nanocatalysts by using naturally abundant and inexpensive cobalt as metal sources,which has been utilized for direct functionalization of nitrogen heterocyclic compounds.The main content of the thesis is composed of the following three sections:(1)By using SiO2 nanospheres as a hard template and aniline as the source of nitrogen-doped carbon support,we have prepared a novel and acid-resistant multi-spherical cavity carbon-supported cobalt oxide nanocatalysts(CoOx/MSCC).Via the as-obtained catalyst and a hydrogen transfer-mediated activation mode for non-activated N-heteroaromatics,we present a direct reductive quinolyl and isoquinolylβ-C-H alkylation with various aldehydes as the alkylating agents for the first time.The catalytic transformation features broad substrate scope,excellent functional tolerance,use of reusable cobalt catalysts and biomass-derived formic acid as a hydrogen source,and no need for pre-functionalizations,demonstrating that the developed nanocatalysts enable to directly functionalize inert N-heteroaryl systems that are difficult to realize by organometallic complexes.(2)By employing UiO-66-NH2 MOF as sacrificial template,we have developed a highly dipersed and ultralow loading cobalt nanocatalyst(Co-ZrO2/N-C),which has been applied in the oxidative functionalization of easily available cyclic amines with 2-aminoarylmethanols to ring-fused quinazolinones,the core structures of numerous valuable products.The developed catalytic transformation proceeds with the merits of broad substrate scope,good functional tolerance and chemoselectivity,high step-and atom-efficiency,use of natural abundant Co/O2system,which offers a practical way for the preparation of quinazolinones with structural diversity.The poisoning experiments and characterization of nanocatalyst indicate that the highly dispersed Co-Nx species serve as active centers for this reaction.The work presented has built an important basis for direct conversion of cyclic amine motifs into functional frameworks.(3)By employing ZIF-8 MOF as sacrificial template,we have manufactured a highly dispersed and acid-resistant subnanometer cobalt catalyst(Co-N-C),which has been applied for the selective C-H oxidative sulfonylation of tetrahydroquinoxalines with odorless sodium sulfinates.The transformation enables generation of a variety of sulfonylquinoxalines with the merits of good substrate and functional compatibility,high regio-and chemoselectivity,and the use of reusable metal catalyst.The recycling experiments show that the catalyst still maintains good catalytic activity and stability even after reuse of 5 times.The work presented offers the potential for further design of heterogeneous nanocatalysts,and the fabrication of functional N-heterocycles molecules that are inaccessible or difficult to prepare by homogeneous catalysis.