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Sadahito Aoshima - One of the best experts on this subject based on the ideXlab platform.
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Metal-Free Living Cationic Polymerization Using Diaryliodonium Salts as Organic Lewis Acid Catalysts
Macromolecules, 2020Co-Authors: Rui Haraguchi, Arihiro Kanazawa, Tsuyoshi Nishikawa, Sadahito AoshimaAbstract:A metal-free initiating system for the living cationic polymerization of alkyl vinyl ethers (VEs) and styrene derivatives was developed using diaryliodonium salts as an organic Lewis Acid Catalyst....
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stereospecific living cationic polymerization of n vinylcarbazole through the design of zncl2 derived counteranions
ACS Macro Letters, 2017Co-Authors: Hironobu Watanabe, Arihiro Kanazawa, Sadahito AoshimaAbstract:Highly stereospecific living polymerization of N-vinylcarbazole (NVC) successfully proceeded via a cationic mechanism as a result of the elaborate design of counteranions using an initiating system consisting of CF3SO3H, nBu4NX (X = Cl, Br, I), and a Lewis Acid Catalyst. The use of ZnCl2 and an appropriate amount of nBu4NCl quantitatively generated highly isotactic polymers (mm = 94%) with narrow molecular weight distributions (Mw/Mn ∼ 1.3) and molecular weights proportional to monomer conversion. In this system, a ZnCl42– species, which was formed as a counteranion of the propagating carbocation, most likely contributed to the stereoregulation of the polymers because the mm value drastically varied depending on the polymerization conditions, such as the Lewis Acid Catalyst and amount of added salt. Isotactic poly(N-vinylcarbazole) (PVK) showed different properties than atactic PVK based on fluorescence and differential scanning calorimetry (DSC) analysis.
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Stereospecific Living Cationic Polymerization of N‑Vinylcarbazole through the Design of ZnCl2‑Derived Counteranions
2017Co-Authors: Hironobu Watanabe, Arihiro Kanazawa, Sadahito AoshimaAbstract:Highly stereospecific living polymerization of N-vinylcarbazole (NVC) successfully proceeded via a cationic mechanism as a result of the elaborate design of counteranions using an initiating system consisting of CF3SO3H, nBu4NX (X = Cl, Br, I), and a Lewis Acid Catalyst. The use of ZnCl2 and an appropriate amount of nBu4NCl quantitatively generated highly isotactic polymers (mm = 94%) with narrow molecular weight distributions (Mw/Mn ∼ 1.3) and molecular weights proportional to monomer conversion. In this system, a ZnCl42– species, which was formed as a counteranion of the propagating carbocation, most likely contributed to the stereoregulation of the polymers because the mm value drastically varied depending on the polymerization conditions, such as the Lewis Acid Catalyst and amount of added salt. Isotactic poly(N-vinylcarbazole) (PVK) showed different properties than atactic PVK based on fluorescence and differential scanning calorimetry (DSC) analysis
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Design of Benign Initiator for Living Cationic Polymerization of Vinyl Ethers: Facile in Situ Generation of Vinyl Ether–Hydrogen Halide Adducts and Subsequent Controlled Polymerization without a Lewis Acid Catalyst
Macromolecules, 2014Co-Authors: Arihiro Kanazawa, Ryo Hashizume, Shokyoku Kanaoka, Sadahito AoshimaAbstract:A Lewis Acid-free initiating system for cationic polymerization of alkyl vinyl ethers (VEs) was developed using CF3SO3H and tetraalkylammonium halides (nBu4NX; X = I, Br, or Cl). The reaction of CF3SO3H, nBu4NX, and an alkyl VE generated a VE–hydrogen halide adduct. The labile carbon–halogen bond, such as a carbon–iodine bond, cleaved without a Lewis Acid Catalyst to induce the living cationic polymerization of VEs. Combining halide anions with suitable nucleophilicities according to monomer reactivity was indispensable for controlled polymerization. Another prerequisite was that the polymerization be conducted at a suitable temperature. After the initiation step, the polymerization probably proceeded via the mechanisms similar to those for the previously reported systems using hydrogen halide and an ammonium salt with a noncoordinating anion. The present system was also useful as a facile method for the synthesis of VE–hydrogen halide adducts without the use of harmful gaseous hydrogen halides. The adduc...
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design of benign initiator for living cationic polymerization of vinyl ethers facile in situ generation of vinyl ether hydrogen halide adducts and subsequent controlled polymerization without a Lewis Acid Catalyst
Macromolecules, 2014Co-Authors: Arihiro Kanazawa, Ryo Hashizume, Shokyoku Kanaoka, Sadahito AoshimaAbstract:A Lewis Acid-free initiating system for cationic polymerization of alkyl vinyl ethers (VEs) was developed using CF3SO3H and tetraalkylammonium halides (nBu4NX; X = I, Br, or Cl). The reaction of CF3SO3H, nBu4NX, and an alkyl VE generated a VE–hydrogen halide adduct. The labile carbon–halogen bond, such as a carbon–iodine bond, cleaved without a Lewis Acid Catalyst to induce the living cationic polymerization of VEs. Combining halide anions with suitable nucleophilicities according to monomer reactivity was indispensable for controlled polymerization. Another prerequisite was that the polymerization be conducted at a suitable temperature. After the initiation step, the polymerization probably proceeded via the mechanisms similar to those for the previously reported systems using hydrogen halide and an ammonium salt with a noncoordinating anion. The present system was also useful as a facile method for the synthesis of VE–hydrogen halide adducts without the use of harmful gaseous hydrogen halides. The adduc...
Arihiro Kanazawa - One of the best experts on this subject based on the ideXlab platform.
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Metal-Free Living Cationic Polymerization Using Diaryliodonium Salts as Organic Lewis Acid Catalysts
Macromolecules, 2020Co-Authors: Rui Haraguchi, Arihiro Kanazawa, Tsuyoshi Nishikawa, Sadahito AoshimaAbstract:A metal-free initiating system for the living cationic polymerization of alkyl vinyl ethers (VEs) and styrene derivatives was developed using diaryliodonium salts as an organic Lewis Acid Catalyst....
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stereospecific living cationic polymerization of n vinylcarbazole through the design of zncl2 derived counteranions
ACS Macro Letters, 2017Co-Authors: Hironobu Watanabe, Arihiro Kanazawa, Sadahito AoshimaAbstract:Highly stereospecific living polymerization of N-vinylcarbazole (NVC) successfully proceeded via a cationic mechanism as a result of the elaborate design of counteranions using an initiating system consisting of CF3SO3H, nBu4NX (X = Cl, Br, I), and a Lewis Acid Catalyst. The use of ZnCl2 and an appropriate amount of nBu4NCl quantitatively generated highly isotactic polymers (mm = 94%) with narrow molecular weight distributions (Mw/Mn ∼ 1.3) and molecular weights proportional to monomer conversion. In this system, a ZnCl42– species, which was formed as a counteranion of the propagating carbocation, most likely contributed to the stereoregulation of the polymers because the mm value drastically varied depending on the polymerization conditions, such as the Lewis Acid Catalyst and amount of added salt. Isotactic poly(N-vinylcarbazole) (PVK) showed different properties than atactic PVK based on fluorescence and differential scanning calorimetry (DSC) analysis.
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Stereospecific Living Cationic Polymerization of N‑Vinylcarbazole through the Design of ZnCl2‑Derived Counteranions
2017Co-Authors: Hironobu Watanabe, Arihiro Kanazawa, Sadahito AoshimaAbstract:Highly stereospecific living polymerization of N-vinylcarbazole (NVC) successfully proceeded via a cationic mechanism as a result of the elaborate design of counteranions using an initiating system consisting of CF3SO3H, nBu4NX (X = Cl, Br, I), and a Lewis Acid Catalyst. The use of ZnCl2 and an appropriate amount of nBu4NCl quantitatively generated highly isotactic polymers (mm = 94%) with narrow molecular weight distributions (Mw/Mn ∼ 1.3) and molecular weights proportional to monomer conversion. In this system, a ZnCl42– species, which was formed as a counteranion of the propagating carbocation, most likely contributed to the stereoregulation of the polymers because the mm value drastically varied depending on the polymerization conditions, such as the Lewis Acid Catalyst and amount of added salt. Isotactic poly(N-vinylcarbazole) (PVK) showed different properties than atactic PVK based on fluorescence and differential scanning calorimetry (DSC) analysis
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Design of Benign Initiator for Living Cationic Polymerization of Vinyl Ethers: Facile in Situ Generation of Vinyl Ether–Hydrogen Halide Adducts and Subsequent Controlled Polymerization without a Lewis Acid Catalyst
Macromolecules, 2014Co-Authors: Arihiro Kanazawa, Ryo Hashizume, Shokyoku Kanaoka, Sadahito AoshimaAbstract:A Lewis Acid-free initiating system for cationic polymerization of alkyl vinyl ethers (VEs) was developed using CF3SO3H and tetraalkylammonium halides (nBu4NX; X = I, Br, or Cl). The reaction of CF3SO3H, nBu4NX, and an alkyl VE generated a VE–hydrogen halide adduct. The labile carbon–halogen bond, such as a carbon–iodine bond, cleaved without a Lewis Acid Catalyst to induce the living cationic polymerization of VEs. Combining halide anions with suitable nucleophilicities according to monomer reactivity was indispensable for controlled polymerization. Another prerequisite was that the polymerization be conducted at a suitable temperature. After the initiation step, the polymerization probably proceeded via the mechanisms similar to those for the previously reported systems using hydrogen halide and an ammonium salt with a noncoordinating anion. The present system was also useful as a facile method for the synthesis of VE–hydrogen halide adducts without the use of harmful gaseous hydrogen halides. The adduc...
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design of benign initiator for living cationic polymerization of vinyl ethers facile in situ generation of vinyl ether hydrogen halide adducts and subsequent controlled polymerization without a Lewis Acid Catalyst
Macromolecules, 2014Co-Authors: Arihiro Kanazawa, Ryo Hashizume, Shokyoku Kanaoka, Sadahito AoshimaAbstract:A Lewis Acid-free initiating system for cationic polymerization of alkyl vinyl ethers (VEs) was developed using CF3SO3H and tetraalkylammonium halides (nBu4NX; X = I, Br, or Cl). The reaction of CF3SO3H, nBu4NX, and an alkyl VE generated a VE–hydrogen halide adduct. The labile carbon–halogen bond, such as a carbon–iodine bond, cleaved without a Lewis Acid Catalyst to induce the living cationic polymerization of VEs. Combining halide anions with suitable nucleophilicities according to monomer reactivity was indispensable for controlled polymerization. Another prerequisite was that the polymerization be conducted at a suitable temperature. After the initiation step, the polymerization probably proceeded via the mechanisms similar to those for the previously reported systems using hydrogen halide and an ammonium salt with a noncoordinating anion. The present system was also useful as a facile method for the synthesis of VE–hydrogen halide adducts without the use of harmful gaseous hydrogen halides. The adduc...
Hisashi Yamamoto - One of the best experts on this subject based on the ideXlab platform.
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New bulky chiral Lewis Acid Catalyst: 3,3′‐di(2‐mesitylethynyl)binaphthol–titanium(iv) complex
Chirality, 2003Co-Authors: Kazuaki Ishihara, Jun Kobayashi, Kazuhiko Nakano, Hideaki Ishibashi, Hisashi YamamotoAbstract:A new chiral Lewis Acid Catalyst 9 was prepared in situ from a 1:2 molar mixture of (R)-3,3'-di(2-mesitylethynyl)binaphthol (6) and titanium(IV) isopropoxide at ambient temperature. The 3- and 3'-substituents on 6 were effective for preventing undesired aggregation between Ti(IV) complexes and increasing the enantioselectivity (up to 82% ee) in the Diels-Alder reaction of methacrolein with cyclopentadiene.
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scandium trifluoromethanesulfonate as an extremely active Lewis Acid Catalyst in acylation of alcohols with Acid anhydrides and mixed anhydrides
Journal of Organic Chemistry, 1996Co-Authors: Kazuaki Ishihara, Manabu Kubota, Hideki Kurihara, Hisashi YamamotoAbstract:Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis Acid Catalyst for acylation of alcohols with Acid anhydrides or the esterification of alcohols by carboxylic Acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by Acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of ω-hydroxy carboxylic Acids.
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TRIS-PENTAFLUOROPHENYL)BORON AS AN EFFICIENT, AIR STABLE, AND WATER TOLERANT Lewis Acid Catalyst
Bulletin of the Chemical Society of Japan, 1995Co-Authors: Kazuaki Ishihara, N. Hanaki, M. Funahashi, M. Miyata, Hisashi YamamotoAbstract:Tris(pentafluorophenyl)boron is an efficient, air stable, and water tolerant Lewis Acid Catalyst for the aldol-type and Michael reactions of silyl enol ethers with carbonyl compounds or other electrophiles (trimethyl orthoformate, dimethyl acetal, and chloromethyl methyl ether), the allylation reaction of allylsilanes with aldehydes, and the Diels–Alder reaction of dienes with α,β-unsaturated aldehydes. A solution of formaldehyde in water is applicable as an electrophile. Also, the aldol-type reaction of ketene silyl acetals with aromatic or aliphatic imines is successfully carried out using the same Catalyst.
Kazuaki Ishihara - One of the best experts on this subject based on the ideXlab platform.
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New bulky chiral Lewis Acid Catalyst: 3,3′‐di(2‐mesitylethynyl)binaphthol–titanium(iv) complex
Chirality, 2003Co-Authors: Kazuaki Ishihara, Jun Kobayashi, Kazuhiko Nakano, Hideaki Ishibashi, Hisashi YamamotoAbstract:A new chiral Lewis Acid Catalyst 9 was prepared in situ from a 1:2 molar mixture of (R)-3,3'-di(2-mesitylethynyl)binaphthol (6) and titanium(IV) isopropoxide at ambient temperature. The 3- and 3'-substituents on 6 were effective for preventing undesired aggregation between Ti(IV) complexes and increasing the enantioselectivity (up to 82% ee) in the Diels-Alder reaction of methacrolein with cyclopentadiene.
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scandium trifluoromethanesulfonate as an extremely active Lewis Acid Catalyst in acylation of alcohols with Acid anhydrides and mixed anhydrides
Journal of Organic Chemistry, 1996Co-Authors: Kazuaki Ishihara, Manabu Kubota, Hideki Kurihara, Hisashi YamamotoAbstract:Scandium trifluoromethanesulfonate (triflate), which is commercially available, is a practical and useful Lewis Acid Catalyst for acylation of alcohols with Acid anhydrides or the esterification of alcohols by carboxylic Acids in the presence of p-nitrobenzoic anhydrides. The remarkably high catalytic activity of scandium triflate can be used for assisting the acylation by Acid anhydrides of not only primary alcohols but also sterically-hindered secondary or tertiary alcohols. The method presented is especially effective for selective macrolactonization of ω-hydroxy carboxylic Acids.
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TRIS-PENTAFLUOROPHENYL)BORON AS AN EFFICIENT, AIR STABLE, AND WATER TOLERANT Lewis Acid Catalyst
Bulletin of the Chemical Society of Japan, 1995Co-Authors: Kazuaki Ishihara, N. Hanaki, M. Funahashi, M. Miyata, Hisashi YamamotoAbstract:Tris(pentafluorophenyl)boron is an efficient, air stable, and water tolerant Lewis Acid Catalyst for the aldol-type and Michael reactions of silyl enol ethers with carbonyl compounds or other electrophiles (trimethyl orthoformate, dimethyl acetal, and chloromethyl methyl ether), the allylation reaction of allylsilanes with aldehydes, and the Diels–Alder reaction of dienes with α,β-unsaturated aldehydes. A solution of formaldehyde in water is applicable as an electrophile. Also, the aldol-type reaction of ketene silyl acetals with aromatic or aliphatic imines is successfully carried out using the same Catalyst.
Ali Rahmatpour - One of the best experts on this subject based on the ideXlab platform.
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polystyrene supported gacl3 as a highly efficient and reusable heterogeneous Lewis Acid Catalyst for the three component synthesis of benzoxanthene derivatives
Monatshefte Fur Chemie, 2013Co-Authors: Ali RahmatpourAbstract:Naphthoquinone-based xanthenes, specifically 14-aryl-13H-dibenzo[a,i]xanthene-8,13(14H)-diones and 12-aryl-2,3,4,12-tetrahydro-1H-benzo[b]xanthene-1,6,11-triones, were obtained in good to excellent yields by a simple, mild, and efficient three-component coupling procedure utilizing polystyrene-supported gallium trichloride as a highly active and eco-friendly heterogeneous Lewis Acid Catalyst. This reaction was also extended to the preparation of 14-aryl-2-hydroxy-13H-dibenzo[a,i]xanthene-8,13(14H)-diones. The experimental and work-up procedure is very simple and the Catalyst can be easily separated from the reaction mixture and reused several times in subsequent reactions.
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Polystyrene‐supported AlCl3 as a highly active and reusable heterogeneous Lewis Acid Catalyst for the one‐pot synthesis of quinoxalines
Heteroatom Chemistry, 2012Co-Authors: Ali RahmatpourAbstract:A new and environmentally benign protocol for the synthesis of quinoxaline derivatives through the condensation reactions of 1,2-diketones and 1,2-phenylenediamines using cross-linked polystyrene-supported aluminum chloride (PS/AlCl3) as a highly active and reusable heterogeneous Lewis Acid Catalyst is described. This polymeric Catalyst is stable and can be easily recovered and reused without appreciable change in its efficiency. © 2012 Wiley Periodicals, Inc. Heteroatom Chem 23:472–477, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.21039
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Polystyrene-supported GaCl3 as a highly efficient and recyclable heterogeneous Lewis Acid Catalyst for one-pot synthesis of N-substituted pyrroles
Journal of Organometallic Chemistry, 2012Co-Authors: Ali RahmatpourAbstract:Abstract A new and environmentally benign method for the preparation of N-substituted pyrroles from one-pot condensation reaction of 2,5-hexanedione with amines and diamines in the presence of polystyrene-supported gallium trichloride (PS/GaCl 3 ) as a highly active and reusable heterogeneous Lewis Acid Catalyst is presented. This new protocol has the advantages of easy availability, stability, reusability and eco-friendly of the Catalyst, high to excellent yields, simple experimental and work-up procedure.
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zrocl2 8h2o as a highly efficient eco friendly and recyclable Lewis Acid Catalyst for one pot synthesis of n substituted pyrroles under solvent free conditions at room temperature
Applied Organometallic Chemistry, 2011Co-Authors: Ali RahmatpourAbstract:A new and efficient method for the synthesis of a variety of N-substituted pyrroles from condensation reactions of 2,5-hexanedione with amines or diamines using ZrOCl2·8H2O as a water-tolerant Lewis Acid Catalyst at room temperature is described.The use of nontoxic, inexpensive, easily available and reusable Catalyst under solvent-free conditions make this protocol practical, environmentally friendly and economically attractive. Copyright © 2011 John Wiley & Sons, Ltd.