3 research outputs found

    Optically Active Helical Polyacetylene Bearing Ferrocenyl Amino-Acid Derivative in Pendants. Preparation and Application as Chiral Organocatalyst for Asymmetric Aldol Reaction

    No full text
    The article reports a novel type of helical polymer-based chiral catalyst for catalyzing asymmetric aldol reactions. Chiral acetylenic monomers containing ferrocenyl amino-acid derivative substituent were synthesized for the first time and structurally identified. The investigated amino acids include alanine and threonine enantiomers. The obtained monomers separately underwent solution homopolymerization and copolymerization with an achirally substituted acetylene monomer in the presence of [Rh­(nbd)­Cl]<sub>2</sub> and Et<sub>3</sub>N. Circular dichroism and UV–vis absorption spectra demonstrated that the copolymer chains adopted predominantly one-handed helices, endowing the copolymers with optical activity. The resulting (co)­polymers were further used to catalyze aldol reaction between cyclohexanone and <i>p</i>-nitrobenzaldehyde. Only threonine-derived copolymers efficiently catalyzed the aldol reaction. A remarkable yield (up to 90%) and enantiomeric excess (up to 93%) were obtained. A synergic effect between the helical structures in the copolymer main chains and the pendent catalytic moieties was found to play a crucial role in the asymmetric catalysis

    Optically Active Helical Polyacetylene Self-Assembled into Chiral Micelles Used As Nanoreactor for Helix-Sense-Selective Polymerization

    No full text
    Chiral micelles have been drawing ever-increasing attention because of their potentials in mimicking the unique stereochemical effects of enzymes. This article reports on the first success in preparing chiral micelles through self-assembly of helical polyacetylene bearing cholic acid pendants. The micelles were further used as chiral nanoreactor, in which achiral acetylenic monomer smoothly underwent helix-sense-selective polymerization (HSSP). The HSSPs directly established optically active core/shell nanoparticles whose shell and core both were constructed by helical polymers. The shells (or micelles) provided a protective effect for the preferably induced one-handed helical polymer chains in the cores. The present work provides insights into the self-assembly of chiral helical polymers, and also provides a powerful strategy for constructing novel chiral polymer nanoarchitectures
    corecore