Preparation Of Supported Chiral Catalysts And Study On Asymmetric Series Reactions

Organic transformations in one-pot catalytic process, as an important aspect of green chemistry, have attracted a great deal of interest due to atomic economy and minimum workup. However, intrinsic disadvantages, such as reuse of expensive organometallic complexes and product contamination from leaching, do still hinder practical applications in industrial process. Thus, development of an immobilized strategy overcomes these barriers is of considerable importance. Silica-based mesoporous materials as supports to immobilize organometallic complexes have exhibited some attracting features in catalysis. And the yolk-shell-structured nano materials, has a removable functional core and outer cladding functional shell, gives it the unique characteristics of nano material, which makes the shell structure of nano material has been widely applied in the field of catalysis. This thesis mainly divided into the following two parts(1) Preparation of supported metal bifunctional catalysts in Sonogashira coupling- the application of asymmetric hydrogen transfer reaction: Herein, we utilize a yolk-shell- structured material and assemble a site- isolated of bifunctional heterogeneous catalyst, overcoming the incompatible nature of Pd/Ru-bimetallic complexes and realizing a tandem reaction from Pd-catalyzed Sonogashira coupling to Ru-catalyzed asymmetric transfer hydrogenatio n in one-pot process. Feature of this yolk-shell- structured bifunctional heterogeneous catalyst possesses site- isolated function, where organopalladium- functionality is anchored within silica shell while chiral organoruthenium- functionality is entrapped onto silicate yolk. It promote cooperatively tandem coupling–asymmetric transfer hydrogenation of haloacetophenones and arylacetylenes to various chiral conjugated alkynols with up to 99% enantioselectivity. Furthermore, the heterogeneous catalyst is also conveniently recovered and reused repeatedly for at least eight times without loss of its catalytic activity, presenting a practical organic transformation in one-pot manner.(2) Preparation of supported metal bifunctional catalysts in Suzuki- Miyaura coupling- the application of asymmetric hydrogen transfer reaction:We synthesize successfully a bifunctional heterogeneous catalyst which loaded Pd nanoparticles and chirality ruthenium catalyst in a simple way and realizing a tandem reaction from Pd-catalyzed Suzuki cross-coupling to Ru-catalyzed asymmetric transfer hydrogenation in one-pot process.Realized for the bimetallic "one-pot" synthesis of chiral biaryl alcohols with up to 97% enantioselectivity, Furthermore, the heterogeneous catalyst is also conveniently recovered and reused repeatedly for several times without loss of its catalytic activity, presenting a practical organic transformation in one-pot manner. catalyst showed higher catalytic performance.