The Immobilization Research On Organic Hydride Compounds

In recent years, organic hydride compounds attract more attentions which cantransfer hydride in form, nicotinamide coenzyme （NAD（P）H） is a typical example.Due to much effort from various research groups, it is already clear that the activecore of NADH is1,4-dihydropyridine. Based on it, a number of NAD（P）H modelswith this core, such as1-benzyl-1,4-dihydronicotinamide （BNAH）, Hantzsch ester（HEH） and10-methyl-9,10-dihydroacridine （AcrH2） have been successfullysynthesized, and they and their analogues are applied widely.Despite their wide employment, it is very difficult for their separation due to thehomogeneous reaction system. Recently, how to address this problem mainlyfocuses on loading them on some solid supports. Merrifield resin, SiO₂,polysiloxane and PEG are popular solid supports in the immobilization of organichydride compounds in the past few decades. Recently, magnetic nanoparticles（MNPs） have been served as highly promising supports of organocatalysts in someprestigious work. MNPs-supported catalysts have been used to catalyze lots oforganic reactions, such as coupling reaction and redox reaction. However, to thebest of our knowledge, no example of MNPs-supported organic hydride compoundwas discovered.Herein, we synthesized magnetic Fe₃O₄nanoparticles with an average size rangeof10-16nm, and used tetraethyl orthosilicate to coat them getting silica-coatedFe₃O₄nanoparticles, the grey silica shell about8-10nm thick. Later, both of themwere shown to the immobilization of BNAH, as-prepared three kind ofMNPs-BNAH were applied in the catalytic reduction of α,β-epoxy ketones andimines. As a result, all of them showed good activities in the reduction ofα,β-epoxy, MNPs-BNAH II showed higher catalytic activity and it could berecycled at least6times with a little loss in activity. However, none of them couldrealize the direct reduction of imines.