Enantioselective N-heterocyclic carbene catalysis by the umpolung of α,β-unsaturated ketones

N-Heterocyclic carbene-catalyzed formation of β-anionic intermediates from enones has been employed in the enantioselective synthesis of 2-aryl propionates. The reaction was achievable using a homochiral 4-MeOC₆H₄ morpholinone catalyst allowing the first example of enantioselective catalysis by umpolung of α,β-unsaturated ketones. The reaction is high yielding, and shows robustness with reasonable generality. A mechanism is proposed in which the enantiodetermining protonation is achieved using either hexafluoroisopropanol or the formed naphthol product.