Catalytic Enantioselective Addition of Cyclic β-Keto Esters with Activated Olefins and N-Boc Imines Using Chiral <i>C</i><sub>2</sub>-Symmetric Cationic Pd<sup>2+</sup> N-Heterocyclic Carbene (NHC) Diaqua Complexes
作者:Zhen Liu、Min Shi
DOI:10.1021/om100331z
日期:2010.6.28
The asymmetric addition of cyclic β-keto esters to activated olefins and N-Boc imines was realized by using chiral cationic C2-symmetric N-heterocyclic carbene (NHC) Pd2+ diaqua complexes 1a,b as the catalysts, producing the corresponding adducts in moderate to high yields (up to 95%) and with good to high enantioselectivities (up to 96% ee). Nevertheless, the most significant observation is that when
Asymmetric Michael reactions of ß-ketoesters with enones were effectively catalyzed by complexes of silver salts and BINAP derivatives in water. The reactions have proved to give Michael adducts in high yields with high enantioselectivities. These reactions are the first example of Lewis acid-catalyzed asymmetric Michael reactions in water.
Direct Generation of Nucleophilic Chiral Palladium Enolate from 1,3-Dicarbonyl Compounds: Catalytic Enantioselective Michael Reaction with Enones
作者:Yoshitaka Hamashima、Daido Hotta、Mikiko Sodeoka
DOI:10.1021/ja027075i
日期:2002.9.1
Generation of chiral palladium enolates from 1,3-dicarbonyl compounds with the palladium aqua complex and its application to the highly efficient catalytic enantioselective Michael reaction with enones are described. The palladium aqua complexes are likely to supply Brønsted base and Brønsted acid successively during the reaction. The former activates the carbonyl compounds to give chiral palladium enolates, and the latter cooperatively activates enones. Using a catalytic amount (2-10 mol %) of the palladium complexes, the various 1,3-dicarbonyl compounds including diketones and beta-ketoesters were converted to the desired Michael adducts in good yields (69-92%) with excellent enantiomeric excesses (89-99% ee).