Abstract
Four kinds of newly synthesized achiral phenylacetylenes bearing a phenylhydrogalvinoxyl residue at 4-position were polymerized by using a chiral rhodium catalyst system, [Rh(nbd)B(C6H5)4] or [Rh(nbd)Cl]2 catalysts in the presence of chiral (R)-(+)- or (S)-(–)-1-phenylethylamine ((R)- or (S)-PEA) cocatalysts. Poly(m-HGDHPA) and poly(m-HGTHPA) in THF showed Cotton signals at the absorption regions of the main chain and hydrogalvinoxyl in the circular dichroism (CD) spectra. It indicated that excess of one-handed helical polyacetylene backbone was induced by helix-sense-selective polymerization (HSSP) under the asymmetric conditions despite the achiral monomer, and the hydrogalvinoxyl moieties were also arranged to form one-handed helical structure. However, there was no Cotton effect for poly(p-HGDHPA) and poly(p-HGTHPA) because the intramolecular hydrogen bonding did not act well to stabilize the helical conformation. The hydrogalvinoxyl units of poly(m-HGDHPA) and poly(m-HGTHPA) were converted to the corresponding galvinoxyl radicals after treatment with PbO2. In the CD spectra of the polyradicals, the Cotton effects decreased depending on their static stability of helical conformation, suggesting that reversal conformation of the polymer chain arose.
Highlights
Polymers with helical conformation possess chirality; i.e., the polymers predominantly folding into either a left- or right-handed helical conformation exhibit optical activity despite the absence of asymmetric carbons
Concerning the synthesis of 3,5-bis(hydroxymethyl)phenylacetylene bonded to galvinoxyl residues paper, we report synthesis of 3,5-bis(hydroxymethyl)phenylacetylenes rigidly bearing a by a rigid hydrogalvinoxyl (p- and m-HGDHPA, and p- and m- HGTHPA) and polymerization of the
In this paper,moiety we report synthesis of 3,5-bis(hydroxymethyl)phenylacetylenes rigidly bearing a monomers under chiral rhodium catalyst system to result in inducing the excess of one-handed helical hydrogalvinoxyl moiety (p- and m-HGDHPA, and p- and m- HGTHPA) and polymerization of the structure ofunder the polyacetylene backbone and galvinoxyl radical chromophores for m-HGDHPA
Summary
Polymers with helical conformation possess chirality; i.e., the polymers predominantly folding into either a left- or right-handed helical conformation exhibit optical activity despite the absence of asymmetric carbons. (DPETHPA)) were synthesized via the Suzuki-Miyaura coupling using the corresponding precursor there triflate are no reports concerning the synthesis of 3,5-bis(hydroxymethyl)phenylacetylene bonded to with and their. Concerning the synthesis of 3,5-bis(hydroxymethyl)phenylacetylene bonded to galvinoxyl residues. Paper, we report synthesis of 3,5-bis(hydroxymethyl)phenylacetylenes rigidly bearing a by a rigid hydrogalvinoxyl (p- and m-HGDHPA, and p- and m- HGTHPA) and polymerization of the. In this paper,moiety we report synthesis of 3,5-bis(hydroxymethyl)phenylacetylenes rigidly bearing a monomers under chiral rhodium catalyst system to result in inducing the excess of one-handed helical hydrogalvinoxyl moiety (p- and m-HGDHPA, and p- and m- HGTHPA) and polymerization of the structure ofunder the polyacetylene backbone and galvinoxyl radical chromophores for m-HGDHPA and monomers chiral rhodium catalyst system to result in inducing the excess of one-handed m-HGTHPA Helical structure of the polyacetylene backbone and galvinoxyl radical chromophores for m-HGDHPA and m-HGTHPA (Scheme 1)
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