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An Acid/Base‐Regulated Recyclable Strategy for Homogeneous Cinchona Alkaloid‐Derived Primary Amine Organocatalysts in Aldol, Vinylogous Michael and Double‐Michael Cascade Reactions
Author(s) -
Wan Jingwei,
Zhao Zhiwei,
Wang Falu,
Ma Xuebing
Publication year - 2015
Publication title -
european journal of organic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.825
H-Index - 155
eISSN - 1099-0690
pISSN - 1434-193X
DOI - 10.1002/ejoc.201500566
Subject(s) - chemistry , cinchona , organocatalysis , michael reaction , aldol reaction , protonation , deprotonation , organic chemistry , cinchona alkaloids , amine gas treating , catalysis , enantioselective synthesis , combinatorial chemistry , ion
A practical, recyclable strategy for homogeneous cinchona alkaloid‐derived primary amine organocatalysts was developed by controlling the solubilities in an aqueous/organic biphasic system through regulating the pH of the aqueous phase, effecting the protonation and deprotonation of primary amino, tertiary amino and pyridyl groups. By means of model aldol, vinylogous Michael and double‐Michael cascade reactions, the reusability of the organocatalysts epi ‐CDNH 2 , DeMe‐QNNH 2 and H‐CDNH 2 over three cycles was investigated in detail. It was found that the organocatalysts were highly effective with respect to catalytic performance, including the yields and stereoselectivities. Furthermore, the recovered organocatalysts in the tenth cycle retained similar excellent enantioselectivities to fresh organocatalysts. However, the formation of inactive intermediates between organocatalyst and reactants resulted in decreased yields.