Asymmetric transfer hydrogenation reactions of N-sulfonylimines by using alcohols as hydrogen sources.

A palladium/zinc co-catalytic system was established and successfully utilized in the asymmetric transfer hydrogenation reactions of N-sulfonylimines with alcohols as hydrogen sources. Simple alcohols such as methanol, ethanol and benzyl alcohols are all variable hydrogen sources that can reduce various N-sulfonylimines to the corresponding chiral amines with high optical purities in presence of this co-catalytic system. Primary mechanistic study revealed that the reaction may initiate with a Pd-hydride intermediate.