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Cinchona Alkaloid‐Catalyzed Enantioselective Amination of α,β‐Unsaturated Ketones: An Asymmetric Approach to Δ 2 ‐Pyrazolines
Author(s) -
Campbell Nathaniel R.,
Sun Bingfeng,
Singh Ravi P.,
Deng Li
Publication year - 2011
Publication title -
advanced synthesis and catalysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.541
H-Index - 155
eISSN - 1615-4169
pISSN - 1615-4150
DOI - 10.1002/adsc.201100447
Subject(s) - enantioselective synthesis , chemistry , cinchona , amination , bifunctional , catalysis , organic chemistry , organocatalysis , conjugate , yield (engineering) , alkaloid , combinatorial chemistry , mathematics , mathematical analysis , materials science , metallurgy
Δ 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 and 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 a considerable range of optically active 3,5‐dialkyl 2‐pyrazolines.