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Organocatalytic Asymmetric Nitroaldol Reaction: Cooperative Effects of Guanidine and Thiourea Functional Groups
Author(s) -
Sohtome Yoshihiro,
Takemura Nobuko,
Takada Keisuke,
Takagi Rika,
Iguchi Toshitsugu,
Nagasawa Kazuo
Publication year - 2007
Publication title -
chemistry – an asian journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.18
H-Index - 106
eISSN - 1861-471X
pISSN - 1861-4728
DOI - 10.1002/asia.200700145
Subject(s) - thiourea , guanidine , catalysis , nitroaldol reaction , chemistry , bifunctional , enantioselective synthesis , substituent , combinatorial chemistry , organic chemistry
Catalytic enantio‐ and diastereoselective nitroaldol reactions were explored by using designed guanidine–thiourea bifunctional organocatalysts under mild and operationally simple biphasic conditions. These catalytic asymmetric reactions have a broad substrate generality with respect to the variety of aldehydes and nitroalkanes. Based on this catalytic nitroaldol process, straightforward syntheses of cytoxazone and 4 ‐epi‐ cytoxazone were achieved. These catalytic nitroaldol reactions require KI as an additive for highly asymmetric induction; it operates by inhibiting the retro mode of the reaction. On the basis of studies of structure and catalytic‐activity relationships, a plausible guanidine–thiourea cooperative mechanism and a transition state of the catalytic reactions are proposed. Drastic substituent effects on the catalytic properties of this catalyst may lead to the development of new chiral surfactants.