- by Enantioselective Conjugate Addition of 1,4‐Dicarbonyl But‐2‐enes
Zhiyong Jiang Dr., Yuanyong Yang, Yuanhang Pan, Yujun Zhao, Hongjun Liu, Choon‐Hong Tan Prof. Dr.
Chemistry - An European Journal, 2009, 15, 4925–4930.
Abstract: Constructing α‐stereogenic amides and ketones: The highly regioselective and enantioselective conjugate addition of 1,3‐dicarbonyl compounds to 1,4‐dicarbonyl but‐2‐enes has been developed with the chiral bicyclic guanidine as catalyst (ee values up to 97 %; see scheme).
In the conjugate addition reaction of a α,β‐unsaturated compound, the new stereogenic center is created in the β‐position. In contrast, conjugate addition to 1,4‐dicarbonyl but‐2‐enes will generate an α‐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 %).
Paper download: https://doi.org/10.1002/chem.200802601