Magnetically recoverable chiral catalysts immobilized on magnetite nanoparticles for asymmetric hydrogenation of aromatic ketones.

Novel heterogenized asymmetric catalysts were synthesized by immobilizing preformed Ru catalysts on magnetite nanoparticles via the phosphonate functionality and were characterized by a variety of techniques, including TEM, magnetization, and XRD. These nanoparticle-supported chiral catalysts were used for enantioselective heterogeneous asymmetric hydrogenation of aromatic ketones with very high enantiomeric excess values of up to 98.0%. The immobilized catalysts were easily recycled by magnetic decantation and reused for up to 14 times without loss of activity and enantioselectivity. Orthogonal nature of the present catalyst immobilization approach should allow the design of other superparamagnetic nanoparticle-supported asymmetric catalysts for a wide range of organic transformations.