Use of Pyridine-Coated Star-Shaped ROMP Polymer As the Supporting Ligand for Ruthenium-Catalyzed Chemoselective Hydrogen Transfer Reduction of Ketones

Abstract

"Soluble" star-shaped polymers containing a pyridine ligand at the chain ends, prepared by adopting sequential living ring-opening metathesis polymerizations (ROMP) of norbornene and a cross-linking reagent using Mo(CHCMe2Ph)(N-2,6-iPr2C6H3)(OtBu)2 via a "core-first" approach, have been employed as ligands for Ru-catalyzed chemoselective hydrogen transfer reductions of various ketones (cyclohexanone, 5-hexen-2-one, 2-allylhexanone, 5-isopropenyl-2-methylcyclohexanone). The activity increased upon addition of the above polymer as the ligand: the prepared catalyst could be recovered quantitatively and reused without decreasing in both activity and selectivity.