A new chiral C1-symmetric NHC-catalyzed addition to α-aryl substituted α,β-disubstituted enals: enantioselective synthesis of fully functionalized dihydropyranones.

The first enantioselective NHC-catalyzed activation of α-aryl substituted α,β-disubstituted unsaturated aldehyde is successfully developed via a highly-active acyl azolium intermediate. The new C1-symmetric biaryl-saturated imidazolium exhibits a superior ability to enable previously unavailable transformation, and the corresponding fully functionalized dihydropyranones are efficiently synthesized in high yields with excellent enantioselectivities.