An investigation into the tether length and substitution pattern of arene-substituted complexes for asymmetric transfer hydrogenation of ketones

A series of Ru(II) catalysts were prepared and tested in the asymmetric transfer hydrogenation of ketones. The catalyst containing a 4-carbon tether gave the fastest rates of ketone reduction. This is due to both increased rate of regeneration of hydride Ru-H and increased rate of ketone reduction. Several classes of ketone were reduced in enantiomeric excesses of up to 97%. Substituents on the arene ring of the catalyst influence the reaction rate and enantioselectivity.