Asymmetric anionic polymerization of maleimides bearing bulky substituents

Oishi, Tsutomu; Onimura, Kenjiro; Isobe, Yukio; Yanagihara, Hiroaki; Tsutsumi, Hiromori

doi:10.1002/(sici)1099-0518(20000115)38:2<310::aid-pola5>3.0.co;2-p

Cited by 39 publications

(16 citation statements)

References 34 publications

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“…(100 mL) in that order. The organic solution was dried over anhydrous MgSO 4 and it was concentrated under reduced pressure. The obtained crude 2-BPMI was purified by column chromatography on silica gel (eluent, benzene), followed by recrystallization from n-hexane-ethyl acetate (1/9, v/v) to obtain pure 2-BPMI as a pale yellow crystal [yield, 1.6 g (56%); mp, 138-140 • C (Lit.…”

Section: N-2-biphenylmaleimide (2-bpmi)mentioning

confidence: 99%

“…[1][2][3][4][5] Main chain carbons of poly(RMI) are chiral because polymerization of RMI proceeds through only trans-opening reaction of double bond in the imide ring. 6 Structures of poly(RMI) produced by trans-addition reactions are displayed in Chart 1.…”

Section: Introductionmentioning

confidence: 99%

“…4,5 Optical activity of poly(RMI) was significantly affected by a structure of N-substituent. The authors investigated the effect of bulkiness of N-substituent on optical activity of poly(RMI) prepared by asymmetric anionic polymerization.…”

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confidence: 99%

“…The authors investigated the effect of bulkiness of N-substituent on optical activity of poly(RMI) prepared by asymmetric anionic polymerization. For example, poly(Ntriphenylmethylmaleimide) 4 (poly(TrMI)) containing a huge N-substituent exhibited small specific rotations ([α] 25 435 = −31.5 • to −2.8 • ). On the other hand, optically active poly(N-phenylmaleimide) 1 (poly(PhMI)) having a small N-substituent showed a higher specific optical rotation ([α] 25 435 = +94.6 • ) than poly(TrMI).…”

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confidence: 99%

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Asymmetric Polymerization of N-ortho- or para-Substituted Phenylmaleimide Using Chiral Anionic Initiators

Oishi

Isobe

Onimura

et al. 2003

Polym J

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ABSTRACT:N-Phenylmaleimide (PhMI) and its derivatives were polymerized using chiral anionic initiators consisting of diethylzinc (Et 2 Zn) and chiral ligands to investigate the effect of the bulkiness, flexibility and polarity of the ortho-or para-substituents on optical activity of the obtained polymer. The optical activity of the polymer was extremely influenced by N-substituents, initiators, and other polymerization conditions. Poly(N-2-biphenylmaleimide) (poly(2-BPMI)) formed with Et 2 Zn-(-)-2,2 -(1-ethylpropylidene)bis(4-benzyl-2-oxazoline) (Bnbox) showed the highest specific rotation ([α] 25 435 ) of +164.7• . From 13 C NMR spectroscopy, optically active poly(2-BPMI) and poly(N-(2-phenoxy)-phenylmaleimide) (poly(2-POPMI)) mainly possessed threo-diisotactic structures in the main chains. Chiral stationary phase prepared from optically active poly(PhMI) optically resolved racemic 1,1 -bi-2-naphthol.KEY WORDS N-Substituted Maleimide / Asymmetric Anionic Polymerization / Chiral Ligand / Optically Active Polymer / N-Substituted maleimide (RMI) is one of the interesting monomers which can form an optically active polymer. [1][2][3][4][5] Main chain carbons of poly(RMI) are chiral because polymerization of RMI proceeds through only trans-opening reaction of double bond in the imide ring. 6 Structures of poly(RMI) produced by trans-addition reactions are displayed in Chart 1. In threo-disyndiotactic structures, stereogenic centers (S , S ) and (R, R) in each monomeric unit equally exist, so that main chain carbons of poly(RMI) do not exhibit optical activity. Threo-diisotactic structures exert optical activity only if either of configurational pairs of (S , S ) or (R, R) predominantly is formed in the trans-main chains. Furthermore, when the same configurational pairs are successively connected in the threo-diisotactic sequences, the polymer main chains can form a helical conformation. If poly(RMI) contains the sequences of helical conformation, the polymer has not only configurational chirality but also conformational one.Systematic research on asymmetric anionic polymerization of achiral RMI bearing aromatic groups has been performed by the authors. 4, 5 Optical activity of poly(RMI) was significantly affected by a structure of N-substituent. The authors investigated the effect of bulkiness of N-substituent on optical activity of poly(RMI) prepared by asymmetric anionic polymerization. = −36.8 • to +762.3 • ) formed by asymmetric anionic method was the highest in all of poly(RMI)s obtained so far. Thus, bulky N-substituents did not always provide high optical activity to the obtained poly(RMI). Therefore, further studies on the effect of N-substituents of RMI on optical activity of the polymer are currently desirable.In this paper, we introduced a substituent into the ortho-or para-position of phenyl group of PhMI, and Chart 1.

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Section: N-2-biphenylmaleimide (2-bpmi)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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confidence: 99%

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Asymmetric Polymerization of N-ortho- or para-Substituted Phenylmaleimide Using Chiral Anionic Initiators

Oishi

Isobe

Onimura

et al. 2003

Polym J

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“…6,[8][9][10][11][12][13][14][15][16][17] Among the optically active poly(RMI)s, the RMI with an achiral 1-naphthyl or a chiral (S)-methylbenzyl group as an N-substituent showed the highest specific optical rotation in chloroform ([a] 435 ¼+762.31, +551.71). [10][11][12] Recently, we reported on the asymmetric polymerizations of achiral maleimide bearing an achiral benzo crown ether and additional effects of the chiral amine on the achiral polymers.…”

Section: Introductionmentioning

confidence: 99%

Synthesis and asymmetric polymerization of chiral maleimides bearing an aza crown ether

Azechi

Iwai

Yamabuki

et al. 2011

Polym J

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Chiral N-substituted maleimide derivatives bearing L-phenylalanine-or L-leucine-introduced aza crown ether ((S)-A15C5PAMI, (S)-A15C5LMI) were synthesized from maleic anhydride, corresponding amino acids and aza crown ether, and polymerized with an organometal/chiral ligand. The number-average-molecular weights and the specific optical rotations of the polymers were 700-5600 and À105.81 to À38.31, respectively. The specific optical rotations of all polymers tended to a positive direction, Keywords: amino acid; anionic polymerization; asymmetric polymerization; aza crown ether; maleimide INTRODUCTIONThe synthesis of optically active polymers is interesting from the standpoints of the formation process, stereoregularity and asymmetric functionality. The optical activity of these polymers is dependent on the main chain forming a one-handed helical structure. The main chain structure of these optically active polymers is very important for special functions such as molecular recognition and asymmetric catalysis. To artificially form a one-handed helical structure, it is necessary to synthesize an optically active polymer by asymmetric polymerization. For example, Okamoto and coworkers [1][2][3][4] reported that the polymers obtained from the asymmetric polymerization of methacrylate derivatives bearing bulky substituents showed substantial optical activity on the basis of one-handed helical conformations.N-Substituted maleimides (RMIs) have been well known as a type of attractive monomer that provides optically active polymers through asymmetric anionic polymerization. 5,6 Because the RMI has a 1,2-disubstituted structure, poly(RMI) can be presumed to produce four types of structures: threo-diisotactic, threo-disyndiotactic, erythrodiisotactic and erythro-disyndiotactic. Erythro-diisotactic and erythro-disyndiotactic structures cannot be formed with cis-additional reactions because of steric hindrance among monomeric units due to carbonyl groups in the imide rings. 7 Trans-additional structures, that is, threo-diisotactic and threo-disyndiotactic structures, can be formed during the polymerization of RMI. Threo-disyndiotactic structures show no optical activity because the (S, S)-and (R, R)-configurational pairs exist at equivalent levels in the polymer main chains. Poly(RMI) with a threo-diisotactic structure can show optical activity when one of the asymmetric carbon pairs in the monomer unit exists in excess. Furthermore, the high continuity of the same configurational pair

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Chirale Modifizierung vonn-Butyllithium: Steuerung von Stöchiometrie, Struktur und Enantioselektivität durch modulare Fencholat-Einheiten

2000

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Professor Dr. Günter Helmchen zum 60. Geburtstag gewidmet Chiral modifizierte lithiumorganische Reagentien haben für enantioselektive Synthesen [1] sowie als Initiatoren in asymmetrischen anionischen Polymerisationen [2] eine herausragende Bedeutung. Die Kontrolle von Reaktivitäten und Selektivitäten durch geeignete chirale Moderatoren ist entscheidend für deren erfolgreichen Einsatz. [3] Untersuchungen in Lösung [4] und im Festkörper [1a,g,h, 5] geben wertvolle Hinweise auf die Natur der chiralen Organolithiumsysteme [6] und eröffnen Möglichkeiten für ein rationales Design neuartiger Reagentien. [7] Obwohl n-Butyllithium (nBuLi) zu den meistverwendeten Lithiumorganylen zählt und einige Röntgenstrukturanalysen achiraler nBuLi-Komplexe bekannt sind, [8] liegen bisher nur sehr wenige Strukturuntersuchungen von chiral modifizierten nBuLi-Systemen vor. [5b,c, 9] Vor kurzem berichteten wir über die Synthese und die Struktur des enantiomerenreinen nBuLi-Lithiumfencholat-Komplexes 1. [9] Er entsteht nach Mischen von o-Anisylfenchol 2 und nBuLi in Hexan als farbloser Niederschlag und enthält

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Asymmetric anionic polymerization of maleimides bearing bulky substituents

Cited by 39 publications

References 34 publications

Asymmetric Polymerization of N-ortho- or para-Substituted Phenylmaleimide Using Chiral Anionic Initiators

Asymmetric Polymerization of N-ortho- or para-Substituted Phenylmaleimide Using Chiral Anionic Initiators

Synthesis and asymmetric polymerization of chiral maleimides bearing an aza crown ether

Chirale Modifizierung vonn-Butyllithium: Steuerung von Stöchiometrie, Struktur und Enantioselektivität durch modulare Fencholat-Einheiten

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