Iridium-Catalyzed Asymmetric Hydrogenation of Unfunctionalized Exocyclic C=C Bonds.

An iridium-catalyzed asymmetric hydrogenation of unfunctionalized exocyclic C=C bonds was performed by using an axially flexible chiral phosphine-oxazoline ligand, providing the desired chiral 1-benzyl-2,3-dihydro-1H-indene products with up to 98 % ee (enantiomeric excess). This represents the first general hydrogenation of unfunctionalized exocyclic olefins with high selectivity reported thus far. The additive acetate ion plays an important role in the reaction's high enantioselectivity. The chiral product can be further transformed into key intermediates required for the synthesis of an important insecticide and a drug compound.