Enantioselective Michael addition catalyzed by cinchona alkaloids

Enantioselective Michael additions of cyclic β‐ketoesters to methyl vinyl ketone catalyzed by cinchona alkaloids were studied. The results revealed that the induced enantioselectivity was significantly influenced by both the structure of the catalyst and that of the substrate. Interesting difference...

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Bibliographic Details
Published in:Chirality (New York, N.Y.) N.Y.), 2001, Vol.13 (10), p.614-618
Main Authors: Szöllösi, György, Bartók, Mihály
Format: Article
Language:English
Subjects:
Butanones - chemistry
Catalysis
cinchona alkaloids
Cinchona Alkaloids - chemistry
enantioselectivity
Esters - chemical synthesis
Esters - chemistry
Gas Chromatography-Mass Spectrometry
Magnetic Resonance Spectroscopy
Methods
methyl vinyl ketone
Michael addition
Stereoisomerism
β-ketoesters
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Summary:Enantioselective Michael additions of cyclic β‐ketoesters to methyl vinyl ketone catalyzed by cinchona alkaloids were studied. The results revealed that the induced enantioselectivity was significantly influenced by both the structure of the catalyst and that of the substrate. Interesting differences in the effect of the structure of the alkaloid on the enantioselectivity of this reaction in the case of three β‐ketoesters were discovered. High enantioselectivities were obtained in the reaction of ethyl 2‐oxocyclopentanecarboxylate and ethyl 2‐oxocyclohexanecarboxylate (up to 83 and 80%, respectively) at a low cinchona:reactant ratio of 1:500. As the specific rotations of the product enantiomers were unknown, they were determined by optical rotation and chiral GC measurements and verified by NMR experiments. Chirality 13:614–618, 2001. © 2001 Wiley‐Liss, Inc.
ISSN:0899-0042
1520-636X
DOI:10.1002/chir.10000