Mesoporous helical silica immobilizing manganese(III)-salen complex for oxidative kinetic resolution of secondary alcohols
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Mesoporous helical silica were prepared by doping of chiral diammoniumcyclohexane mono-tartrate salt in a sol–gel process, then functionalized to immobilize Mn(III)-salen complexes for oxidative kinetic resolution of secondary alcohols. Characterization revealed the doped silica significantly changed chiral recognition, porosity and hydrolysis resistance compared with blank-doped one. In catalysis, helical silica-supported Mn(III)-salen showed satisfactory conversion, enantioselectivity and selectivity factor, while major configuration of resolution products was determined by configuration of silica supports more than Mn(III)-salen. Furthermore, linkage of (S,S)-diammonium salt-doped silica with Mn(III)-(R,R)salen showed better enantioselectivity than other combinations. At last, in addition to iodobenzene diacetate, hydrogen peroxide (30 wt%) was another effective terminal oxidant. This work not only provided new chiral silica materials, but also explored their application in catalytic resolution.
KeywordsMesoporous helical silica Mn(III)-salen Oxidative kinetic resolution Secondary alcohol Enantioselectivity
This work was supported by Shaanxi Higher Education Teaching Reform Project (No. 13BY02, Cultivation of Creative Ability of Scientific Research for the Undergraduate), and the Fundamental Research Funds for the Central Universities (No. xjj2014005, Application of Porous Helical Support in Catalytic Asymmetric Reactions).