The sulfone group as a versatile and removable directing group for the asymmetric transfer hydrogenation of ketones

The sulfone functional group has a strong capacity to direct the asymmetric transfer hydrogenation (ATH) of ketones by [(arene)Ru(TsDPEN)H] complexes by adopting a position distal to the η 6 -arene ring. This preference provides a means for the prediction of the sense of asymmetric reduction. The sulfone group also facilitates the formation of a range of reduction substrates and its ready removal provides a route to enantiomerically-enriched alcohols which would otherwise be extremely difficult to prepare by direct ATH of the corresponding ketones.