Synthesis of alpha-stereogenic amides and ketones by enantioselective conjugate addition of 1,4-dicarbonyl but-2-enes.

In the conjugate addition reaction of a alpha,beta-unsaturated compound, the new stereogenic center is created in the beta-position. In contrast, conjugate addition to 1,4-dicarbonyl but-2-enes will generate an alpha-stereogenic center with respect to one of the carbonyl groups, which informally, can be considered as an inversion of normal reactivity patterns or Umpolung. In this paper, we demonstrate that chiral bicyclic guanidine can catalyze the addition of 1,3-dicarbonyl compounds to 1,4-dicarbonyl but-2-enes [(E)-4-oxo-4-arylbutenamides and (E)-4-oxo-4-arylbutenones] with high regioselectivity and enantioselectivity (ee values up to 97%).