1268603-75-3Relevant academic research and scientific papers
Recoverable Cinchona ammonium salts as organocatalysts in the enantioselective Michael addition of β-keto esters
Tari, Silvia,Chinchilla, Rafael,Najera, Carmen
experimental part, p. 2872 - 2878 (2011/03/18)
Several dimeric Cinchona-alkaloid anthracenyldimethyl-derived ammonium salts, are used as organocatalysts in the enantioselective Michael addition reaction of cyclic β-keto esters to α,β-unsaturated carbonyl compounds, in the presence of diisopropylethylamine as a base (30 mol %), for the generation of enantiomerically enriched adducts bearing quaternary stereocenters. Quinine and quinidine-derived dimeric ammonium salts (1-10 mol %) afford the opposite and higher enantioselectivities of the corresponding adducts (up to 94% ee) in good yields (up to 98%). Substituted 2-alkoxycarbonyl-1-indanones are used as nucleophile precursors, as well as ethyl 2-oxocyclopentanecarboxylate and tert-butyl 2,5-dioxo-1-phenylpyrrolidine- 3-carboxylate. These organocatalysts can be recovered at the end of the reaction by precipitation in ether and reused without any loss of activity.
