Bis(binaphthylcyclopentadienyl)-derived metallocene peroxide complexes: Catalysts for the enantioselective epoxidation of unfunctionalized alkenes

The enantioselective catalytic epoxidation of unfunctionalized alkyl and aryl olefins was conducted using titanocene and niobocene peroxide complexes incorporating a C 2 -symmetrical binaphthylcyclopentadienyl ligand (BpDMCp). Enantiomeric excesses up to 20% and activities up to 55 turnovers were obtained with the application of our chiral bis(binaphthylcyclopentadienyl)-derived metallocenes. A significant decrease in the enantioselectivity for the epoxidation of trans -3-hexene was observed when the metal was changed from titanium to niobium in these binaphthyl-derived C 2 -symmetrical complexes. The preparation of the bis(binaphthylcyclopentadienyl)-chloroniobium peroxide complexes and bis(indenyl)chloroniobium peroxide is described.