Enantioselective Iridium-Catalyzed α-Allylation with Aqueous Solutions of Acetaldehyde.

The enantioselective α-allylation of aqueous solutions of acetaldehyde using iridium- and amine-catalyzed substitution of racemic allylic alcohols is described. The method utilizes a readily available, safely handled aqueous solution of acetaldehyde and furnishes γ,δ-unsaturated aldehydes in good yields and greater than 99% enantiomeric excess. The synthetic potential of the method is demonstrated with the enantioselective formal syntheses of heliannuols C and E as well as heliespirones A and C.