Asymmetric Transfer Hydrogenation of 1,3-Alkoxy/Aryloxy Propanones Using Tethered Arene/Ru(II)/TsDPEN Complexes.

A series of propanones containing combinations of aryloxy and alkoxy substituents at the 1- and 3-positions were reduced to the alcohols via asymmetric transfer hydrogenation using a tethered Ru(II)/TsDPEN catalyst. The enantioselectivities of the reductions reveal a complex pattern of electronic and steric effects which, when used in a matched combination, can lead to the formation of products of up to 68% ee (84:16 er) from this highly challenging class of substrate.