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Bae, Han Yong
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Unprecedented Hydrophobic Amplification in Noncovalent Organocatalysis "on Water": Hydrophobic Chiral Squaramide Catalyzed Michael Addition of Malonates to Nitroalkenes

Author(s)
Bae, Han YongSong, Choong Eui
Issued Date
2015-06
DOI
10.1021/acscatal.5b00685
URI
https://scholarworks.unist.ac.kr/handle/201301/25871
Fulltext
https://pubs.acs.org/doi/10.1021/acscatal.5b00685
Citation
ACS CATALYSIS, v.5, no.6, pp.3613 - 3619
Abstract
In this study, water was demonstrated to be an exceptionally efficient reaction medium for the noncovalent, hydrogen-bonding-promoted enantioselective Michael addition of malonates to diverse nitroolefins using cinchona-based squaramide catalysts. A significant increase in the reaction rate was observed when the reaction was performed "on water" rather than in the conventional organic solvents, because of the hydrophobic hydration effect. This hydrophobic amplification was significantly dependent upon the hydrophobicity of the C3-substituent (vinyl or ethyl) of cinchona-based catalysts. Thus, the use of more hydrophobic catalyst with an ethyl group at the C3-position, even a highly challenging Michael donor such as dimethyl methylmalonate was also smoothly converted to the desired adduct. Furthermore, because of the remarkable rate acceleration under "on water" conditions, the catalyst loading also significantly decreased. Thus, in the case of beta-ketoesters, even 0.01 mol % of catalyst loading was enough to complete the reaction at room temperature, affording the corresponding Michael adducts with perfect diastereo- and enantioselectivity (up to >99:1 d.r., up to 99% ee). The developed "on water" protocol was successfully applied for the scalable syntheses of an antidepressant (S)-rolipram and an anticonvulsant (S)-pregabalin
Publisher
AMER CHEMICAL SOC
ISSN
2155-5435
Keyword (Author)
noncovalent organocatalysis "on water"malonates as Michael donorshydrophobic hydrationhydrophobic substituent effectLog P
Keyword
ASYMMETRIC ALDOL REACTIONSENANTIOSELECTIVE MICHAEL1,3-DICARBONYL COMPOUNDSAQUEOUS-MEDIAHIGHLY EFFICIENTORGANIC-REACTIONSBIFUNCTIONAL ORGANOCATALYSTSCONJUGATED NITROALKENESAMINO-ACIDSDERIVATIVES

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