Asymmetric Organocatalytic Transfer Hydrogenation of Cyclic Enones

Significance

The authors describe a highly enantioselective organocatalytic transfer hydro­genation of cyclic α,β-unsaturated ketones 1. The reaction is mediated by imidazolidinone catalyst 3, which has previously been used in iminium catalytic Diels-Alder reactions of α,β-unsaturated ketones with dienes. Valuable chiral cyclic ketones 4 are obtained in moderate to good yields and good to excellent enantioselectivities in the presence of tert-butyl Hantzsch ester 2 as hydrogen source. This process was successfully applied to five-, six-, and seven-membered ring systems.