title: Majority-Rules-Type Helical Poly(quinoxaline-2,3-diyl)s as Highly Efficient Chirality-Amplification Systems for Asymmetric Catalysis.
abstract: 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 ΔG(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 PPh2 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.
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan).
authors.forename: Yuan-Zhen
authors.initials: YZ
authors.lastname: Ke
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan).
authors.forename: Yuuya
authors.initials: Y
authors.lastname: Nagata
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan).
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Yamada
authors.affiliation: Department of Synthetic Chemistry and Biological Chemistry, Graduate School of Engineering, Kyoto University, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan). suginome@sbchem.kyoto-u.ac.jp.|JST, CREST, Katsura, Nishikyo-ku, Kyoto 615-8510 (Japan). suginome@sbchem.kyoto-u.ac.jp.
authors.forename: Michinori
authors.initials: M
authors.lastname: Suginome
keywords: asymmetric amplification; asymmetric synthesis; helical structures; ligand design; polymer catalysts