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Synthesis of Cinchona Urea Polymers and Their Evaluation as Catalyst in the Asymmetric Reactions
Author(s) -
Abdelkawy Mahmoud A.,
Aly ElSaied A.,
ElBadawi Mahmoud A.,
Itsuno Shinichi
Publication year - 2020
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.202001436
Subject(s) - catalysis , cinchona , cinchona alkaloids , chemistry , condensation polymer , organic chemistry , urea , michael reaction , polymer , adduct , coupling reaction , polymer chemistry , combinatorial chemistry , enantioselective synthesis
Chiral polyureas of cinchona alkaloids were synthesized via repetitive Mizoroki‐Heck (MH) coupling reaction. The Pd‐catalyzed polycondensation of cinchona urea dimers 6 and aromatic diiodide 7 afforded the chiral polyureas ( P1 − P4 ). The catalytic activity of the chiral polymers was subsequently investigated. The asymmetric Michael addition of ketoesters to nitroolefins was successfully catalyzed by the polymeric organocatalysts ( P1 − P4 ) to give the corresponding Michael adducts with high catalytic activities and excellent enantionselectivities (up to >99% ee). The polymeric catalysts were insoluble in commonly used organic solvents. They were easily recovered and reused several times without any loss of the catalytic activity.