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Majority‐Rules‐Type Helical Poly(quinoxaline‐2,3‐diyl)s as Highly Efficient Chirality‐Amplification Systems for Asymmetric Catalysis
Author(s) -
Ke YuanZhen,
Nagata Yuuya,
Yamada Tetsuya,
Suginome Michinori
Publication year - 2015
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201502209
Subject(s) - quinoxaline , enantioselective synthesis , chirality (physics) , monomer , chemistry , catalysis , copolymer , solvent , stereochemistry , crystallography , polymer chemistry , polymer , organic chemistry , physics , chiral symmetry breaking , quantum mechanics , nambu–jona lasinio model , quark
A highly efficient majority‐rules effect of poly(quinoxaline‐2,3‐diyl)s (PQXs) bearing 2‐butoxymethyl chiral side chains at the 6‐ and 7‐positions was established and attributed to large Δ G h values (0.22–0.41 kJ mol −1 ), which are defined as the energy difference between P ‐ and M ‐helical conformations per chiral unit. A PQX copolymer prepared from a monomer derived from ( R )‐2‐octanol (23 % ee ) and a monomer bearing a PPh 2 group adopted a single‐handed helical structure (>99 %) and could be used as a highly enantioselective chiral ligand in palladium‐catalyzed asymmetric reactions (products formed with up to 94 % ee ), in which the enantioselectivity could be switched by solvent‐dependent inversion of the helical PQX backbone.