Enantioselective 1,2-reductions of beta-trifluoromethylated-alpha,beta-unsaturated ketones to chiral allylic alcohols over organoruthenium-functionalized mesoporous silica nanospheres

摘要

Organoruthenium-functionalized mesoporous silica nanospheres are prepared through the co-assembly of chiral (4-(trimethoxysilyl) ethyl)phenylsulfonyl-1,2-diphenylethylene-diamine and tetraethoxysilane followed by complexation with an organoruthenium complex. Structural analysis and characterization disclose its well-defined single-site organoruthenium active center, and electron microscopy images reveal its uniformly distributive, mesostructured nanospheres. As a heterogeneous catalyst, it displays high catalytic activity and enantioselectivity in the asymmetric 1,2-reductions of beta-trifluoromethylated-alpha,beta-unsaturated ketones to give chiral allylic alcohols, resulting in up to 97% enantioselectivity with a wide scope of substrates. Furthermore, this heterogeneous catalyst can be conveniently recovered and reused for at least eight times without loss of catalytic activity, being particularly attractive in the practice of organic synthesis.