Asymmetric Polymerization

Ito, Shingo; Nozaki, Kyoko

doi:10.1002/9780470584248.ch13

Cited by 22 publications

(27 citation statements)

References 484 publications

(290 reference statements)

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“…The origin of life is about chirality because of its existence in biomolecules, such as nucleic acids, proteins, and carbohydrates and its involving in biological mechanism in human beings, animals, and plants on the earth [1][2][3][4][5][6]. Chirality has also become increasingly important in pharmaceutical science and industry on the design, discovery, and development of drugs for enhancing their potency and selectivity [5,6].…”

Section: Introductionmentioning

confidence: 99%

“…In all of above known cases, for Wilkinson's ferrocene, a transition metal is needed to anchor two planes for designing two-layered chiral catalysts. For optically pure [2,2] phanephos ligands, two covalent bonds are necessitated to assemble their two-layer chirality so as to efficiently control catalytic activity and enantioselectivity of asymmetric reactions. For noncovalent imidazoline-based biaryl P,Nligands, the aromatic interaction between the fully fluorinated electron-deficient phenyl ring and the electron-efficient naphthyl ring plays a crucial role in stabilizing chiral planar stacking.…”

Section: Introductionmentioning

confidence: 99%

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Multilayer 3D Chirality and Its Synthetic Assembly

Liu

Yang

et al. 2019

Research

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3D chirality of sandwich type of organic molecules has been discovered. The key element of this chirality is characterized by three layers of structures that are arranged nearly in parallel fashion with one on top and one down from the center plane. Individual enantiomers of these molecules have been fully characterized by spectroscopies with their enantiomeric purity measured by chiral HPLC. The absolute configuration was unambiguously assigned by X-ray diffraction analysis. This is the first multilayer 3D chirality reported and is anticipated to lead to a new research area of asymmetric synthesis and catalysis and to have a broad impact on chemical, medicinal, and material sciences in future.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Multilayer 3D Chirality and Its Synthetic Assembly

Liu

Yang

et al. 2019

Research

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“…Polymerization of racemic propylene oxide with a ZnEt 2 /(+)-borneol or ZnEt 2 /(À)-menthol initiator system gave optically active polymers, and the unreacted monomer was rich in the (S)-isomer (Fig. 27) [16]. The enantiomer selectivity is generally higher in the polymerization of thiiranes than in that of oxiranes.…”

Section: Oxiranes and Thiiranesmentioning

confidence: 97%

“…However, it was recently found that bimetallic complex 15 (Fig. 28) exhibits high enantiomer selectivity for polymerizations of oxiranes, k S /k R up to 370 [16].…”

Section: Oxiranes and Thiiranesmentioning

confidence: 98%

Stereospecific Polymerization

Hirano

Kitaura

2014

Encyclopedia of Polymeric Nanomaterials

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“…[5][6][7][8] As the first artificial helical polymer which undergoes helix-helix transition by light and not by heat, we reported poly(2,7-bis(4-tert-butylphenyl)fluoren-9-ylacrylate) [poly(BBPFA)]. 4,9 A polystyrene derivative bearing a terphenyl structure in the side chain, poly(2,5-bis[4-((S)-2-methylbutyloxy)phenyl]styrene) [poly(BMBPSt)] (Chart 1) and its derivatives were synthesized by radical polymerization, and its preferred-handed helicity was evidenced.…”

Section: Poly(25-bis[4-((s)-2-methylbutyloxy)phenyl]styrene)mentioning

confidence: 99%

Photo-induced helix–helix transition of a polystyrene derivative

et al. 2014

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Poly(2,5-bis[4-((S)-2-methylbutyloxy)phenyl]styrene)having a helical conformation underwent helix-helix transition on photo irradiation. Conformational transition can significantly alter polymer properties, and so far thermal stereomutaion have been studied. However, as for photo-induced mutation, only helix-helix transition (irreversible CD-active to CD-silent helix transition) of a polyacrylate has been explored. Here, we present mutation of the polystyrene derivative. Chiroptical, viscometric, and vibrational spectroscopic analyses indicated the polymer mutated from an optically active helix to another, optically inactive helix with a different shape.Functions and properties of natural 1 and artificial 2 macromolecules are sensitive to chain conformation. For example, denaturation, mutation from a functional shape to a disordered one, of proteins makes them lose their precise functions.2 Some artificial polymers undergo helix-helix transition governed by chemical, thermal and photo stimuli.2-4 Such polymers revert their helix sense, showing a broad range of applications. [5][6][7][8] As the first artificial helical polymer which undergoes helix-helix transition by light and not by heat, we reported poly(2,7-bis(4-tert-butylphenyl)fluoren-9-ylacrylate) [poly(BBPFA)]. 4,9 A polystyrene derivative bearing a terphenyl structure in the side chain, poly(2,5-bis[4-((S)-2-methylbutyloxy)phenyl]styrene) [poly(BMBPSt)] (Chart 1) and its derivatives were synthesized by radical polymerization, and its preferred-handed helicity was evidenced. [10][11][12] This series of polymers contain terphenyl group in the side-chain. Since the main-chain stereomutaion of poly(BBPFA) has been proposed to be triggered by twist-coplanar mutation 13 on excitation, we expected some main-chain mutation also on excitation of poly(BMBPSt). However, this polymer exhibited responses to light distinctive to those of poly(BBPFA). An optically active helix turned into an optically inactive, racemic helix where the shape helical chain remarkably changed, i.e., apparent chain length decreased and width of helix increased; the original slim helix became stocky by light. Chart 1 Structure of poly(BMBPSt).The polymer sample (M n 79,320, M w /M n 2.01 vs. polystyrene) was prepared by radical polymerization in benzene at 60 o C according to the literature.11 Photo irradiation to the sample was conducted using a 500 W Hg-Xe lamp without polarization. The sample was a solution in either tetrahydrofuran (THF) containing 2,2,6,6-tetramethyl-4-piperidinol 14 as an achiral radical scavenger. The scavenger was used to avoid any side reaction that could be caused by a radical species generated by irradiation.14 The polymer solution in THF indicated intense Cotton effects in circular dichroism (CD) spectra attributable. The spectra are ascribed not to monomeric unit chirality but to a main-chain helix, because BMBPSt monomer shows CD spectra with much lower intensity and a completely different spectral shape from that of the polymer. The spectral intensity was no...

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Asymmetric Polymerization

Cited by 22 publications

References 484 publications

Multilayer 3D Chirality and Its Synthetic Assembly

Multilayer 3D Chirality and Its Synthetic Assembly

Stereospecific Polymerization

Photo-induced helix–helix transition of a polystyrene derivative

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