Asymmetric Hydrogenation Of Acetophenone On Chirally Modified Metallic Catalysts

Asymmetric catalytic hydrogenation of prochiral ketones to generate chiral alcohols has received widespread attention in the field of catalysis due to the broad applications of the protocol in the synthesis of pharmaceuticals,pesticides and daily life chemicals.Many efficient asymmetric homogeneous catalysts have been developed for the synthesis of chiral alcohols by this transformation.However,because of some inherent shortcomings of homogeneous catalysis,such as the difficulties exist in the separation and purification of the product,the poor recyclability as well as the high price of the catalyst,it is difficult to apply it in industrial production.However,heterogeneous asymmetric catalysis can overcome these problems on the identical conditions,and it bears obvious advantages rather than that of the homogeneous one.On this point,a series of heterogeneous platinum and ruthenium-containing chiral catalyst were prepared with the functionalized multiple-walled carbon nanotubes（CNTs）as carrier.The as-prepared catalysts were then used in the asymmetric hydrogenation of acetophenone to obtain chiral?-phenethylol alcohol.The thesis consists of these contents as follows:1.Different types of CNTs（OD≥50 nm and 30-50 nm）were used to prepare supported platinum and ruthenium metal nanocatalysts of Pt/CNTs and Ru/CNTs with different loadings（5 wt%,8 wt%,10 wt%,12 wt%,respectively）.And the catalytic asymmetric hydrogenation of acetophenone was investigated with them as the catalysts at the presence of chiral modifiers.It showed that these pristine supported nanocatalysts showed poor chiral inducibility in this reaction.2.The raw CNTs were pretreated to obtain the functionalized supports.The well-known chiral ligand of（R）-2,2’-diphenylphosphony-1,1’-binaphthalene（（R）-BINAP）was chemical modified with through the procedures of oxidation,nitrolation and reduction to obtain the amine-containing（R）-BINAP derivatives of（R）-BINAP-NH₂.Then it was reacted with the functionalized CNTs through a simple coupling reaction to prepare the CNTs supports with chiral phosphorus-containing ligants of CNTs-HN-BINAP.The later was then reacted with different loadings of Pt precursor to give the chiral Pt heterocatalyst of Pt/CNTs-HN-BINAP.The as-prepared heterocatalyst was then applied to the asymmetric hydrogenation of acetophenone.It was found that the conversion of88.1%as well as the enantioselectivity of 65.2%was obtained with the catalysis of10 wt%Pt/CNTs-HN-BINAP.The recyclability of the catalysts was also investigated.It showed that the catalysts could be moderately reused in the reaction.3.Ru/CNTs-HN-BINAP with different loads（5 wt%,8 wt%,10 wt%,12 wt%,respectively）was successfully synthesed using CNTs-HN-BINAP and Ru precursor to obtain Ru/CNTs-HN-BINAP chiral catalysts.It was also used in the asymmetric hydrogenation of acetophenone.It showed that a higher conversion of 91.2%as well as a higher ee value of 78.1%was provided with the catalysis of 8 wt%Ru/CNTs-HN-BINAP than that of 10%Pt/CNTs-HN-BINAP under the same conditions.Furthermore,the catalysts could be reused about 4 run without the obvious activity losing.It was very important for improving the efficiency of chiral ligands and noble metal active sites in asymmetric hydrogenation reactions.