Synthesis Of Magnetic Nanoparticles Or Mesoporous MCM-41-supported Gold Complexes Catalysts And Their Applications In Organic Synthesis

Recently,gold-catalyzed carbon–carbon and carbon–heteroatom bonds formation reactions and construction of heterocyclic compounds have received much attention.However,expensive homogeneous gold catalysts are difficult to separate from the product and can not be recycled,the isolated product is easily contaminated by gold species,which restricting their practical applications.Therefore,the development of heterogeneous gold catalysts having high catalytic activity and excellent recyclability and applications of them to gold-catalyzed organic transformations have important theoretical and practical significance.To solve these key problems restricting the practical applications of homogeneous gold catalysis,immobilization of homogeneous gold catalysts on the surfaces of solid supports is usually the method of choice since the supported gold catalysts can be facilely recovered and recycled without the catalytic activity of homogeneous gold catalysts being decreased.Based on the excellent properties of magnetic nanoparticles and mesoporous MCM-41 materials as the supports for immobilizing transition-metal catalysts,in this dissertation,we designed and prepared a series of magnetic Fe₃O₄ nanoparticles or mesoporous MCM-41-immobilized gold complexes.These heterogeneous gold complexes were characterized and used as catalysts for carbon–carbon bond and carbon–heteroatom bond formation reactions and synthesis of heterocyclic compounds.The research works are mainly divided in seven parts as follow:?1?The condensation reaction of commercially available 2-?diphenylphosphino?-ethyltriethoxysilane with silica-coated Fe₃O₄?Fe₃O₄@SiO₂?gave the diphenylphosphino-functionalized magnetic nanoparticles?Fe₃O₄@SiO₂-P?,the latter was reacted with AuCl in MeOH to afford the magnetic nanoparticles-supported phosphine gold?I?complex?Fe₃O₄@SiO₂-P-AuCl?.This heterogeneous phosphine gold?I?complex was characterized and utilized as catalyst in direct reductive amination of aldehydes and ketones with amines.The results showed that this heterogeneous gold?I?-catalyzed direct reductive amination reaction proceeded smoothly at room temperature under neutral conditions,yielding a variety of secondary amines in excellent yields.Moreover,this heterogeneous gold?I?catalyst can be recycled for 10 times without any loss of activity.?2?The condensation reaction of triethoxysilyl-functionalized bipyridine ligand with Fe₃O₄@SiO₂ gave the bipyridine-functionalized magnetic nanoparticles?Fe₃O₄@ SiO₂-bipy?,the latter reacted with AuCl₃ in MeOH to give the magnetic nanoparticlessupported gold???-bipy complex?Fe₃O₄@SiO₂-bipy-AuCl₃?.This heterogeneous gold???complex was characterized and applied to oxidative ?-cyanation of tertiary amines with trimethylsilyl cyanide.After the optimization of reaction conditions and examinations of substrate scope and recyclability,it was found that the heterogeneous gold???-catalyzed ?-cyanation of tertiary amines proceeded smoothly under acid-free and mild conditions,afford the corresponding ?-aminonitriles in good to excellent yields.The catalytic efficiency of the catalyst remains unaltered even after recycling 10 times,providing a new,practical and green route to ?-aminonitriles.?3?The treatment of 3-aminopropyltriethoxysilane with bis?bromomethyl?-functionalized bipy-gold???complex [?BrCH₂?₂bipy-AuCl₂][AuCl₄] generated triethoxysilyl-functionalized bipy-gold???complex,the latter was condensed with Fe₃O₄@ SiO₂ to afford the magnetic nanoparticles-immobilized bipy-gold???complex?Fe₃O₄ @SiO₂-bipy-AuCl₂][AuCl₄]?.This heterogeneous Au???complex was characterized and utilized as catalyst for cross-dehydrogenative coupling?CDC?of tertiary amines with nitroalkanes and various unmodified ketones.The result showed that this heterogeneous Au???-catalyzed cross-dehydrogenative coupling proceeded smoothly under mild conditions using air as the sole oxidant,to afford the corresponding C–C coupling products in good to excellent yields.The new heterogeneous gold???catalyst can be recycled for at least 10 times without a significant loss of activity.?4?The condensation of triethoxysilyl-functionalized PPh₃ ligand with mesoporous MCM-41,followed by silylation with Me₃SiCl afforded the triphenylphosphinefunctionalized MCM-41?MCM-41-PPh₃?,the latter was reacted with Me₂SAuCl in DCM,followed by treatment with AgNTf₂ to give the MCM-41-supported phosphine gold?I?complex [MCM-41-PPh₃-AuNTf₂].This heterogeneous gold?I?complex was characterized and applied to [2 + 2 + 1] annulation of terminal alkynes,nitriles,and oxygen atoms.After the optimization of reaction conditions and examinations of substrate scope and recyclability,it was found that this heterogeneous gold?I?-catalyzed [2 + 2 + 1] annulation proceeded smoothly under mild conditions,yielding a variety of 2,5-disubstituted oxazoles in good to excellent yields.The catalyst can easily be recycled for at least 8 times without significant loss of activity.?5?The reaction of triphenylphosphine-functionalized MCM-41?MCM-41-PPh₃?with Me2 SAuCl in DCM,followed by treatment with AgOTf afforded the MCM-41-supported phosphine gold?I?complex [MCM-41-PPh₃-AuOTf].This heterogeneous gold?I?complex was characterized and used as catalyst for the intermolecular cycloaddition between 2-aminoaryl carbonyl compounds and internal alkynes.The results showed that this heterogeneous gold?I?-catalyzed intermolecular annulation proceeded smoothly at 100 oC,affording a variety of quinoline derivatives in high yields.The new gold?I?catalyst can be reused for at least 8 times without any loss of activity.?6?The double hydroamination of 2-alkynylanilines with terminal alkynes was investigated by using Fe₃O₄@SiO₂-bipy-AuCl₃/AgOTf as catalysts to synthesize N-vinylindoles.The results indicated that this heterogeneous Au???catalyst exhibited high catalytic activity and could be recycled for 8 times without obvious decrease in activity,providing a new,simple and practical route to N-vinylindoles.?7?The annulation of 2-alkynylbenzamides with NH₄ OAc was investigated by using Fe₃O₄@SiO₂-bipy-AuCl₃/AgSbF₆ as catalysts.The results showed that this heterogeneous Au???-catalyzed annulation of 2-alkynylbenzamides with NH₄ OAc proceeded smoothly at 85 oC,yielding a variety of 1-aminoisoquinoline derivatives in good yields.Moreover,the gold???catalyst can be recycled for at least 8 times without significant loss of activity.