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

Abstract

In the conjugate addition reaction of a a,|3-unsaturated compound, the new stereogenic center is created in the b-position. In contrast, conjugate addition to 1,4-dicarbonyl but-2-enes will generate an astereogenic 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 bicy-clic guanidine can catalyze the addition of 1,3-dicarbonyl compounds to 1,4-di-carbonyl but-2-enes [(E)-4-oxo-4-aryl- butenamides and (E)-4-oxo-4-arylbute-nones] with high regioselectivity and enantioselectivity (ee values up to 97%). © 2009 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.