The Design,Synthesis, And Application Of Supported Proline Organocatalysts And Gold Catalysts

There are two part of work in our article. The first part is about the design and synthesis of the supported proline catalysts and their applications in the asymmetric aldol reaction; the second part is about the preparation of the catalysts gold loaded on the fibrous nano-silica material KCC-1 and their catalytic activities for the reduction of 4-nitrophenol.In the first part of work, two kind of organocatalysts Fe3O4@SiO2-Pro and SB A-16-Pro were successfully prepared using core-shell silica magnetic microspheres Fe3O4@SiO2 and cage-like mesoporous material SBA-16 as supports,respectively. After being comfirmed by corresponding characterizations, their catalytic activities, stereoselectivities and reusabilities were tested in the asymmetric aldol reaction.?1? The chiral immobilized organocatalyst based on proline as active sites and silica magnetic nanoparticles as supports has been successfully prepared and applied to the asymmetric aldol reaction between aromatic aldehydes and ketones. Good yields ?92%?, diastereoselectivities ?85:15? and enantioselectivities ?80%? were shown in the activity evaluation experiments. This synthesized catalyst had excellent magnetic separation ability, mechanical strength and recyclability, evidenced by being extensively reused for five times without any substantial loss of activity.?2? The chiral metal-free organocatalyst based on proline as active sites and mesoporous cage-like material SBA-16 as support has been successfully prepared and used in the asymmetric aldol reaction between aromatic aldehydes and ketones. Good yields ?91%?, diastereoselectivities ?97:3? and enantioselectivities ?85%? exhibited in the activity evaluation experiments. This synthesized catalyst avoided heavy metal pollution during the preparing and using process, and had excellent mechanical strength and reusability, evidenced by being extensively reused without any substantial loss of activity.In the second part of work, fibrous nano-silica material KCC-1 was firstly synthesized,then functionalized by thiol groups and ionic liquids and loaded with gold nanoparticles. Their catalytic activities were tested in the reduction of 4-nitrophenol.?3? The Au nanoparticles on the surface of thiol-functionalized fibrous nano-silica material KCC-1 had a good dispersion and uniform particle size distribution. The catalyst KCC-1-SH/Au exhibited high catalytic activity in the reduction of 4-nitrophenol by NaBH4, which was mainly attributed to the synergistic effect between the Au nanoparticles and the thiol groups onto the surface of KCC-1 nanospheres. The thiol groups grafted onto the surface of KCC-1 nanospheres could avoid Au NPs leaching from the support, which made the KCC-1-SH/Au have an excellent recyclability, evidenced by being extensively reused for ten times without any substantial loss of activity.?4? The new type of nano-catalyst KCC-1-IL/Au based on ionic liquid-modified fibrous nano-silica material KCC-1 as support and Au particles as active sites has been successfully prepared and exhibited high catalytic activity in the reduction of 4-nitrophenol by NaBH4 because of the unique dendritic fibrous morphology of the support, which made the active sites accessible, and the synergistic effect between the KCC-1-IL and the small-size Au NPs. The KCC₁-IL/Au had a good recyclability,mainly attributed to the IL groups grafted onto the surface of KCC-1 nanospheres,which acted as robust anchors to avoid Au NPs leaching from the support.