Catalytic asymmetric synthesis using chirality-switchable helical polymer as a chiral ligand

Suginome, Michinori; Yamamoto, Takeshi; Nagata, Yuuya; Yamada, Tetsuya; Akai, Yuto

doi:10.1351/pac-con-11-08-23

Cited by 86 publications

(43 citation statements)

References 3 publications

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“…Inspired by the sophisticated functions of biological helical polymers and their assemblies, a rich variety of artificial helical polymers has been prepared over the past decades in order to develop advanced chiral materials for the resolution of enantiomers by chromatography, sensing of chiral molecules, and circularly polarized luminescence . The application of optically active helical polymers for asymmetric catalysis has also attracted growing interest, because a one‐handed helical chirality can significantly contribute to the enantioselectivity due to a one‐handed helical arrangement of the catalytically active, chiral/achiral units along the one‐handed helical polymer backbone . Up to now, a variety of helical polymer‐based asymmetric catalysts have been developed mainly by introducing catalytically active, chiral/achiral units as components in or along artificial helical polymers that involve polyacetylenes, poly(methacrylate)s, polyisocyanates, polyisocyanides, and poly(quinoxaline‐2,3‐diyl)s .…”

Section: Introductionmentioning

confidence: 99%

“…The application of optically active helical polymers for asymmetric catalysis has also attracted growing interest, because a one‐handed helical chirality can significantly contribute to the enantioselectivity due to a one‐handed helical arrangement of the catalytically active, chiral/achiral units along the one‐handed helical polymer backbone . Up to now, a variety of helical polymer‐based asymmetric catalysts have been developed mainly by introducing catalytically active, chiral/achiral units as components in or along artificial helical polymers that involve polyacetylenes, poly(methacrylate)s, polyisocyanates, polyisocyanides, and poly(quinoxaline‐2,3‐diyl)s . In these cases, the use of optically active monomers is essential to control their helical handedness except for poly(methacrylate)s with a bulky pendant prepared by helix‐sense‐selective polymerization using chiral catalysts or initiators .…”

Section: Introductionmentioning

confidence: 99%

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Helicity Induction and Its Static Memory of Poly(biphenylylacetylene)s Bearing Pyridine N‐Oxide Groups and Their Use as Asymmetric Organocatalysts

Ando

Ishidate

Ikai

et al. 2019

J. Polym. Sci. Part A: Polym. Chem.

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Novel poly(biphenylylacetylene) derivatives carrying different types of pyridine N‐oxide units with a bulky or less‐bulky substituent at a different position as the functional pendant groups (poly‐2a and poly‐2b) were synthesized by the rhodium‐catalyzed polymerization of the corresponding monomers. The influence of the steric environment around the catalytically active pyridine N‐oxide sites on the helicity induction and its static memory as well as the asymmetric catalytic activities of the resulting helical polymers with a macromolecular helicity memory was investigated. The polyacetylenes formed an excess one‐handed helical conformation upon noncovalent interactions with optically active alcohols and the induced macromolecular helicities of the polyacetylenes were efficiently memorized after the removal of the chiral inducers. Poly‐2b with the macromolecular helicity memory showed an enantioselectivity for the catalytic asymmetric allylation of benzaldehydes, producing optically active allyl alcohols, although their enantioselectivities were low. On the other hand, poly‐2a exhibited a negligible catalytic activity probably due to the bulky substituent at the o‐position of the pyridine N‐oxide residues, while poly‐2a underwent a unique helix‐inversion with the increasing concentration of chiral alcohols and the opposite helicity of poly‐2a was further successfully memorized. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2481–2490

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Helicity Induction and Its Static Memory of Poly(biphenylylacetylene)s Bearing Pyridine N‐Oxide Groups and Their Use as Asymmetric Organocatalysts

Ando

Ishidate

Ikai

et al. 2019

J. Polym. Sci. Part A: Polym. Chem.

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“…Most importantly, the helical sense of the PQXs bearing optically active 2‐butoxymethyl side chains was found to be chirality‐switchable:13a–d The corresponding exclusively left handed helical polymer ligand ( M )‐ 5 was obtained when a solution of ( P )‐ 5 in 1,1,2‐TCE/toluene (3:1 v/v) was heated at 60 °C for 24 h. The left‐handed‐helical polymer ( M )‐ 5 was then used as a ligand in the asymmetric hydrosilylation, and under similar conditions, the R product was obtained with high enantioselectivity (95 % ee ). This result demonstrates that the treatment of ( P )‐ 5 in 1,1,2‐TCE/toluene induced an almost absolute M ‐helical conformation in 5 .…”

Section: Methodsmentioning

confidence: 99%

Majority‐Rules‐Type Helical Poly(quinoxaline‐2,3‐diyl)s as Highly Efficient Chirality‐Amplification Systems for Asymmetric Catalysis

Nagata

Yamada

et al. 2015

Angewandte Chemie

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Ahighly 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 DG h values (0.22-0.41 kJ mol À1 ), which are defined as the energy difference between P-and M-helical conformations per chiral unit. APQX copolymer prepared from amonomer derived from (R)-2-octanol (23 %ee) and amonomer bearing aP Ph 2 group adopted as ingle-handed helical structure (> 99 %) and could be used as ah ighly 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.Helical majority-rules-type polymers, [1,2] which are derived from chiral monomers with low ee values and adopt nonlinearly enhanced single-handed helical conformations,a re among the most promising platforms for the development of new asymmetric-amplification systems.[3] Thec oncept of the enantioselective synthesis of chiral compounds through asymmetric amplification [4] has attracted considerable interest, as it may afford useful model systems for the elucidation of the origin of natural homochirality [5] as well as practical methods for the generation of optically active molecules. [6] Although an umber of helical polymers [7] with efficient asymmetric amplification in terms of helix-sense induction have been developed, the highly enantioselective production of chiral compounds on the basis of asymmetric amplification by majority-rules-type helical polymers has not been reported. According to the theory developed by Green and co-workers for polymers containing helix-sense-reversal conformations (Green theory,c ase 3), [8] them aximum value of the screw-sense excess (se)ofahelical polymer,whose degree of polymerization (DP) is sufficiently large,islimited by DG h (the energy difference between P-a nd M-helical conformations) and DG r (the energy difference of the helix-sensereversal conformation relative to the helical conformation). Formost helical polymers,the DG h and/or DG r values are too small to induce ap urely single handed screw sense.Acistransoidal poly(aryl acetylene) bearing (R)-(1-phenylethyl)-carbamate side chains (DG h = 0.0048 kJ mol À1, DG r = 15.5 kJ mol À1 ), for example,exhibits even at very high degrees of polymerization merely 49.5 % se at room temperature. [9] Forthe enantioselective generation of chiral compounds from am ajority-rules-type helical polymer,t he use of ap olymer backbone exhibiting large DG h and DG r values is therefore of critical importance.Recently,w er eported sergeants-and-soldiers-type [10] poly(quinoxaline-2,3-diyl)s (PQXs) containing (R)-2-butoxymethyl and propoxymethyl groups in arandom manner.[11] A DG h value of 0.59 kJ mol À1 was estimated for the chiral unit of this polymer system, thus indicating that 22 chiral units are required for as crew-sense induction of 99.0 % se.W eh ave also reported that single-handed helically chiral PQ...

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“…This catalyst also demonstrated catalytic abilities in promoting atroposelective Suzuki-Miyaura crosscouplings, affording the biaryl products as the opposite enantiomers in similar levels of enantioselectivity. The optical properties of this chirality-switchable polymeric ligand were subsequently studied in detail [36]. …”

Section: Applications To the Synthesis Of Enantioenriched Atropisomersmentioning

confidence: 99%

At the Forefront of the Suzuki–Miyaura Reaction: Advances in Stereoselective Cross-Couplings

Sun

Hall

2015

Topics in Organometallic Chemistry

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Catalytic asymmetric synthesis using chirality-switchable helical polymer as a chiral ligand

Cited by 86 publications

References 3 publications

Helicity Induction and Its Static Memory of Poly(biphenylylacetylene)s Bearing Pyridine N‐Oxide Groups and Their Use as Asymmetric Organocatalysts

Helicity Induction and Its Static Memory of Poly(biphenylylacetylene)s Bearing Pyridine N‐Oxide Groups and Their Use as Asymmetric Organocatalysts

Majority‐Rules‐Type Helical Poly(quinoxaline‐2,3‐diyl)s as Highly Efficient Chirality‐Amplification Systems for Asymmetric Catalysis

At the Forefront of the Suzuki–Miyaura Reaction: Advances in Stereoselective Cross-Couplings

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