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Cinchona alkaloid catalyzed enantioselective amination of ?,?-unsaturated ketones: an asymmetric approach to ?2-pyrazolines.

ABSTRACT: ?2-Pyrazolines are of significant medicinal and synthetic interest due to their therapeutic properties and utility in the synthesis of 1,3-diamines, yet few asymmetric methods exist to prepare them. An unprecedented highly enantioselective organocatalytic synthesis of 2-pyrazolines was achieved through an asymmetric conjugate addition catalyzed by 9-epi-amino cinchona alkaloids followed by deprotection-cyclization, which furnished chiral 2-pyrazolines in 46-78% yield and 59-91% ee. This bifunctional catalytic methodology thus provides easy access to considerable range of optically active 3,5-dialkyl 2-pyrazolines.

SUBMITTER: Campbell NR 

PROVIDER: S-EPMC3692356 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Cinchona alkaloid catalyzed enantioselective amination of α,β-unsaturated ketones: an asymmetric approach to Δ<sup>2</sup>-pyrazolines.

Campbell Nathaniel R NR   Sun Bingfeng B   Singh Ravi P RP   Deng Li L  

Advanced synthesis & catalysis 20111101 17

Δ<sup>2</sup>-Pyrazolines are of significant medicinal and synthetic interest due to their therapeutic properties and utility in the synthesis of 1,3-diamines, yet few asymmetric methods exist to prepare them. An unprecedented highly enantioselective organocatalytic synthesis of 2-pyrazolines was achieved through an asymmetric conjugate addition catalyzed by 9-<i>epi</i>-amino cinchona alkaloids followed by deprotection-cyclization, which furnished chiral 2-pyrazolines in 46-78% yield and 59-91%  ...[more]

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