Updated on 2024/06/14

写真a

 
IWAMOTO Hajime
 
Organization
Academic Assembly Institute of Science and Technology Fundamental Sciences Associate Professor
Graduate School of Science and Technology Associate Professor
Faculty of Science Associate Professor
Title
Associate Professor
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Degree

  • 博士(工学) ( 1998.3   東京工業大学 )

  • 修士(工学) ( 1995.3   東京工業大学 )

  • 工学士 ( 1993.3   東京工業大学 )

Research Areas

  • Nanotechnology/Materials / Structural organic chemistry and physical organic chemistry

  • Life Science / Bioorganic chemistry

  • Nanotechnology/Materials / Functional solid state chemistry

Research History

  • Niigata University   Graduate School of Science and Technology   Associate Professor

    2009.2

  • Niigata University   Faculty of Science Department of Chemistry   Associate Professor

    2009.2 - 2017.3

Education

  • Tokyo Institute of Technology   Graduate School, Division of Science and Engineering   Department of Chemical Engineering

    - 1998.3

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    Country: Japan

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  • Tokyo Institute of Technology   Faculty of Engineering   Department of Chemical Engineering

    - 1993.3

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    Country: Japan

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Papers

  • Triarylamine-Substituted Benzimidazoliums as Electron Donor–Acceptor Dyad-Type Photocatalysts for Reductive Organic Transformations

    Ryo Miyajima, Yuuki Ooe, Tomoaki Miura, Tadaaki Ikoma, Hajime Iwamoto, Shin-ya Takizawa, Eietsu Hasegawa

    Journal of the American Chemical Society   145 ( 18 )   10236 - 10248   2023.5

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    Publishing type:Research paper (scientific journal)   Publisher:American Chemical Society (ACS)  

    DOI: 10.1021/jacs.3c01264

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  • Sterically Regulated α-Oxygenation of α-Bromocarbonyl Compounds Promoted Using 2-Aryl-1,3-dimethylbenzimidazolines and Air. International journal

    Eietsu Hasegawa, Naoki Yoshioka, Tsukasa Tanaka, Taisei Nakaminato, Kazuki Oomori, Tadaaki Ikoma, Hajime Iwamoto, Kan Wakamatsu

    ACS omega   5 ( 13 )   7651 - 7665   2020.4

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    A debrominative oxygenation protocol has been developed for the conversion of α-bromo-α,α-dialkyl-substituted carbonyl compounds to their corresponding α-hydroxy analogues. For example, stirring a solution of α-bromoisobutyrophenone and 2-aryl-1,3-dimethylbenzimidazoline (BIH-Ar) at room temperature under an air atmosphere leads to the efficient formation of α-hydroperoxyisobutyrophenone, which can be converted to α-hydroxyisobutyrophenone using Me2S reduction. In contrast, reaction of α-bromoacetophenone under the same conditions produces the α-hydrogenated product acetophenone. α-Keto-alkyl and benzimidazolyl radicals (BI•-Ar), generated via dissociative electron transfer from BIH-Ar to α-bromoketone substrates, serve as key intermediates in the oxidation and reduction processes. The dramatic switch from hydrogenation to oxygenation is attributed to a steric effect of α-alkyl substituents, which causes hydrogen atom abstraction from sterically crowded BIH-Ar to α-keto-alkyl radicals to be slow and enable preferential reaction with molecular oxygen. Generation of the α-keto-alkyl radical and BI•-Ar intermediates in these process and their sterically governed hydrogen atom transfer reactions are supported by results arising from DFT calculations. Moreover, an electron spin resonance study showed that visible light irradiation of phenyl benzimidazoline (BIH-Ph) in the presence of molecular oxygen produces the benzimidazolyl radical (BI•-Ph). The addition of thiophenol into the reaction of α-bromoisobutyrophenone and BIH-Ph predominantly produced α-phenylthiolated isobutyrophenone even if a high concentration of molecular oxygen exists. Furthermore, the developed protocol was applied to other α-bromo-α,α-dialkylated carbonyl compounds.

    DOI: 10.1021/acsomega.0c00509

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  • Protocol for Visible-Light-Promoted Desulfonylation Reactions Utilizing Catalytic Benzimidazolium Aryloxide Betaines and Stoichiometric Hydride Donor Reagents. Reviewed International journal

    Eietsu Hasegawa, Tsukasa Tanaka, Norihiro Izumiya, Takehiro Kiuchi, Yuuki Ooe, Hajime Iwamoto, Shin-Ya Takizawa, Shigeru Murata

    The Journal of organic chemistry   85 ( 6 )   4344 - 4353   2020

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    An unprecedented photocatalytic system consisting of benzimidazolium aryloxide betaines (BI+-ArO-) and stoichiometric hydride reducing reagents was developed for carrying out desulfonylation reactions of N-sulfonyl-indoles, -amides, and -amines, and α-sulfonyl ketones. Measurements of absorption spectra and cyclic voltammograms as well as density functional theory (DFT) calculations were carried out to gain mechanistic information. In the catalytic system, visible-light-activated benzimidazoline aryloxides (BIH-ArO-), generated in situ by hydride reduction of the corresponding betaines BI+-ArO-, donate both an electron and a hydrogen atom to the substrates. A modified protocol was also developed so that a catalytic quantity of more easily prepared hydroxyaryl benzimidazolines (BIH-ArOH) is used along with a stoichiometric hydride donor to promote the photochemical desulfonylation reactions.

    DOI: 10.1021/acs.joc.0c00038

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  • Visible Light and Hydroxynaphthylbenzimidazoline Promoted Transition-Metal-Catalyst-Free Desulfonylation of N-Sulfonylamides and N-Sulfonylamines Reviewed International journal

    Eietsu Hasegawa, Yuto Nagakura, Norihiro Izumiya, Keisuke Matsumoto, Tsukasa Tanaka, Tomoaki Miura, Tadaaki Ikoma, Tadaaki Ikoma, Hajime Iwamoto, Kan Wakamatsu

    Journal of Organic Chemistry   83 ( 18 )   10813 - 10825   2018.9

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    Copyright © 2018 American Chemical Society. A visible light promoted process for desulfonylation of N-sulfonylamides and -amines has been developed, in which 1,3-dimethyl-2-hydroxynaphthylbenzimidazoline (HONap-BIH) serves as a light absorbing, electron and hydrogen atom donor, and a household white light-emitting diode serves as a light source. The process transforms various N-sulfonylamide and -amine substrates to desulfonylated products in moderate to excellent yields. The observation that the fluorescence of 1-methyl-2-naphthoxy anion is efficiently quenched by the substrates suggests that the mechanism for the photoinduced desulfonylation reaction begins with photoexcitation of the naphthoxide chromophore in HONap-BIH, which generates an excited species via intramolecular proton transfer between the HONap and BIH moieties. This process triggers single electron transfer to the substrate, which promotes loss of the sulfonyl group to form the free amide or amine. The results of studies employing radical probe substrates as well as DFT calculations suggest that selective nitrogen-sulfur bond cleavage of the substrate radical anion generates either a pair of an amide or amine anio

    DOI: 10.1021/acs.joc.8b01536

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  • Benzimidazolium Naphthoxide Betaine Is a Visible Light Promoted Organic Photoredox Catalyst Reviewed

    Eietsu Hasegawa, Norihiro Izumiya, Tomoaki Miura, Tadaaki Ikoma, Hajime Iwamoto, Shin-Ya Takizawa, Shigeru Murata

    Journal of Organic Chemistry   83 ( 7 )   3921 - 3927   2018.4

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    Benzimidazolium naphthoxide (-ONap-BI+) was first synthesized and utilized as an unprecedented betaine photoredox catalyst. Photoexcited state of -ONap-BI+ generated by visible light irradiation catalyzes the reductive deiodination as well as desulfonylation reactions in which 1,3-dimethyl-2-phenylbenzimidazoline (Ph-BIH) cooperates with as an electron and hydrogen atom donor. Significant solvent effects on the reaction progress were discovered, and specific solvation toward imidazolium and naphthoxide moieties of -ONap-BI+ was proposed.

    DOI: 10.1021/acs.joc.8b00282

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  • Optimum Conditions for On-tree Ethanol-sticker Treatment for Astringency Removal in 'Taigetsu' and 'Taiten' Persimmons Reviewed

    Atsu Yamasaki, Hiroshi Yakushiji, Hajime Iwamoto, Akifumi Azuma, Hiroyoshi Sugiura

    HORTICULTURE JOURNAL   86 ( 4 )   463 - 469   2017

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:JAPAN SOC HORTICULTURAL SCI  

    Various on-tree ethanol-sticker treatments for 'Taigetsu' and 'Taiten' persimmon (astringent cultivars) were tested to identify optimal treatment conditions for astringency removal and fruit quality. Using aluminum foil coated or polyethylene terephthalate stickers to attach a pad containing 1.5 g of ethanol powder to both sides of the fruit surface in early October removed astringency completely, while the application of treatments to one side of the fruit surface did not. The astringency removal was incomplete in treatments with a cast coating sticker. The aluminum foil-coated sticker with a 1.0 g ethanol pad applied in early October removed flesh astringency completely without fruit skin darkening or the occurrence of large numbers of brown specks in the flesh. It extended fruit shelf life by approximately 7 days compared with postharvest CO2 treatment in November. Conversely, sticker treatments in late September caused many brown specks in the flesh. The sticker treatment with a 0.6 g ethanol pad failed to remove the astringency completely while the sticker treatment with a 1.5 g ethanol pad resulted in heavy fruit skin darkening or the appearance of shallow concentric cracks on the fruit skin. Therefore, we conclude that an on-tree sticker treatment with a 1.0 g ethanol pad on both sides of the fruit surface in early October removes fruit astringency completely and provides high quality 'Taigetsu' and 'Taiten' persimmon fruit.

    DOI: 10.2503/hortj.OKD-039

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  • Visible light-promoted reductive transformations of various organic substances by using hydroxyaryl-substituted benzimidazolines and bases Reviewed

    Eietsu Hasegawa, Norihiro Izumiya, Takuya Fukuda, Kazuki Nemoto, Hajime Iwamoto, Shin-ya Takizawa, Shigeru Murata

    TETRAHEDRON   72 ( 48 )   7805 - 7812   2016.12

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    Visible light promoted reduction reactions of organohalides, sulfonamides, organonitriles and epoxy ketones were performed using 1,3-diinethylbenzimidazolines possessing 2-hydroxynaphthyl or 2-hydroxyphenyl substituents (HOAr-DMBIH) as photo-reductants. Xe or Hg-Xe lamp through an appropriate glass-filter (lambda>390 nm) and a household white light-emitting diode were used as light sources. In these reactions, reductive cleavages of carbon halogen, nitrogen sulfur, carbon carbon (nitrile) and carbon oxygen bonds take place. Bases exert significant effects on the progress of these reactions in a manner that depends on the nature of the substrate. Addition of 1,8-diazabicyclo[5.4.0]undec-7-ene as well as potassium t-butoxide significantly accelerates photo-reduction reactions of organohalides, sulfonamides and organonitriles while the decomposition of formed hydroxy ketones occurs in reactions of epoxy ketones. Single electron transfer from the photo-excited states of benzimidazolines (HOAr-DMBIH) or their deprotonated analogues (-OAr-DMBIH) to the substrates is proposed to initiate these reactions. (C) 2016 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2016.05.078

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  • Solvent-Dependent Reaction Pathways Operating in Copper(II) Tetrafluoroborate Promoted Oxidative Ring-Opening Reactions of Cyclopropyl Silyl Ethers Reviewed

    Eietsu Hasegawa, Kazuki Nemoto, Ryosuke Nagumo, Eiji Tayama, Hajime Iwamoto

    JOURNAL OF ORGANIC CHEMISTRY   81 ( 7 )   2692 - 2703   2016.4

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    Oxidative ring-opening reactions of benzene-fused bicyclic cydopropyl silyl ethers, promoted by copper(II) tetrafluoroborate, were investigated. The regioselectivity of cyclopropane ring-opening as well as product distributions were found to be highly dependent on the nature of the solvent. In alcohols, dimeric substances arising from external bond cleavage are major products. Radical rearrangement products are also formed in solvents such as ether and ethyl acetate. On the contrary, nucleophile addition to carbocation intermediates, generated by internal bond cleavage, occurs mainly in reactions taking place in acetonitrile. It is proposed that the observed solvent effects that govern the reaction pathways followed are a consequence of varying solvation of copper intermediates, which governs their reactivity and redox properties. In addition, the influence of counteranions of the copper salts, organonitriles, cyclic dienes, and substrate structures on the pathways followed in these reactions was also examined.

    DOI: 10.1021/acs.joc.5b02827

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  • Synthesis of linear [5]catenanes via olefin metathesis dimerization of pseudorotaxanes composed of a [2]catenane and a secondary ammonium salt Reviewed

    Hajime Iwamoto, Shinji Tafuku, Yoshihiko Sato, Wataru Takizawa, Wataru Katagiri, Eiji Tayama, Eietsu Hasegawa, Yoshimasa Fukazawa, Takeharu Haino

    CHEMICAL COMMUNICATIONS   52 ( 2 )   319 - 322   2016

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    [5]Catenanes were synthesized by olefin metathesis dimerization. The reaction of pseudorotaxanes, which were derived from a [2]catenane and one equivalent of an ammonium salt bearing two terminal olefins in dichloromethane, with a catalytic amount of Grubbs catalyst afforded linear [5]catenanes in 12% yield. Intermolecular and intramolecular olefin metathesis reactions were controlled by the length of the alkyl chain of the ammonium salts.

    DOI: 10.1039/c5cc07562a

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  • Aryl-substituted dimethylbenzimidazolines as effective reductants of photoinduced electron transfer reactions Reviewed

    Eietsu Hasegawa, Taku Ohta, Shiori Tsuji, Kazuma Mori, Ken Uchida, Tomoaki Miura, Tadaaki Ikoma, Eiji Tayama, Hajime Iwamoto, Shin-ya Takizawa, Shigeru Murata

    TETRAHEDRON   71 ( 34 )   5494 - 5505   2015.8

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    Photoinduced electron transfer (PET) reactions promoted by 2-aryl substituted 1,3-dimethylbenzimidazolines (Ar-DMBIH) were investigated. Excited states of Ar-DMBIH, formed by irradiation using light above 360 initiate PET reductions of various organic substrates, including transformations of epoxy ketones to aldols, free radical rearrangements such as the Dowd-Beckwith ring-expansion and 5-exo hexenyl cyclization, deprotection of N-sulfonyl-indols, and allylation of acyl formates. In these processes, Ar-DMBIH possessing 1-naphthyl, 2-naphthyl, 1-pyrenyl and 9-anthryl substituents formally act as two electron and one proton donors while the hydroxynaphthyl substituted derivative serves as a two electron and two proton donor. On the basis of the results of absorption spectroscopy studies, cyclic voltammetry and DFT calculation, a mechanistic sequence for these reduction reactions is proposed that involves initial photoexcitation of the aryl chromophore of the Ar-DMBIH followed by single electron transfer (SET) to the organic substrate to generate the radical cation of benzimidazoline and the radical anion of the substrate. (C) 2015 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2015.06.071

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  • Metal-Free, One-Pot, Sequential Protocol for-Transforming alpha,beta-Epoxy Ketones to beta-Hydroxy Ketones and alpha-Methylene Ketones Reviewed

    Eietsu Hasegawa, Saki Arai, Eiji Tayama, Hajime Iwamoto

    JOURNAL OF ORGANIC CHEMISTRY   80 ( 3 )   1593 - 1600   2015.2

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    A new sequential, one-pot protocol for transforming 1,3-disubstituted 2,3-epoxy ketones to beta-hydroxy ketones and alpha-methylene ketones has been developed. Reaction of epoxy ketones with boron trifluoride etherate ((BF3OEt2)-O-.) generates the cationic intermediates by regioselective epoxide ring opening and an acyl shift. Then, a treatment of these cations with 2-aryl-1,3-dimethylbenzimidazolines (DMBIH) results in formation of 1,2-disubstituted 3-hydroxy ketones. DMBIH serves as a hydride donor in the second step of this process. Finally, the beta-hydroxy ketones can be converted to 1,2-disubstituted 2-methylene ketones by treatment with methanesulfonic acid or a combination of methanesulfonyl chloride and triethylamine. Importantly, the sequential steps involved in formation of the alpha-methylene ketone products can be carried out in one pot.

    DOI: 10.1021/jo5025249

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  • Visible Light-Promoted Metal-Free Reduction of Organohalides by 2-Naphthyl or 2-Hydroxynaphthyl-Substituted 1,3-Dimethylbenzimidazolines Reviewed

    Eietsu Hasegawa, Kazuma Mori, Shiori Tsuji, Kazuki Nemoto, Taku Ohta, Hajime Iwamoto

    AUSTRALIAN JOURNAL OF CHEMISTRY   68 ( 11 )   1648 - 1652   2015

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:CSIRO PUBLISHING  

    The visible light-promoted reduction reactions of some organohalides were investigated using 2-aryl-1,3-dimethylbenzimidazolines (Ar-DMBIH) possessing 2-naphthyl or 2-hydroxynaphthyl substituents. In these reduction reactions, singleelectron transfer from photo-excited Ar-DMBIH, attained by Xe lamp irradiation through an appropriate glass-filter (lambda > 390 nm), to the halide substrates leads to the carbon-halogen bond cleavage, followed by the rearrangements of the formed carbon radicals such as 5-exo hexenyl cyclization and the Dowd-Beckwith ring expansion. Addition of 1,8-diazabicyclo[5.4.0] undec-7-ene was found to enhance the reducing ability of hydroxynaphthyl-substituted DMBIH. A household white light-emitting diode was also used as a light source for these reactions.

    DOI: 10.1071/CH15396

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  • Copper(II)-acid catalyzed cyclopropanation of 1,3-dienamides by electrophilic activation of alpha-aryl diazoesters Reviewed

    Eiji Tayama, Kouki Horikawa, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS   55 ( 19 )   3041 - 3044   2014.5

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    Copper(II)-acid catalyzed cyclopropanation of electron-rich alkenes, such as 1,3-dienamides, with cc-aryl diazoesters are described. The reaction could be performed without rare metal catalysts, excess substrate, or the need for the slow addition of the diazoesters. (C) 2014 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tetlet.2014.03.115

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  • A photo-reagent system of benzimidazoline and Ru(bpy)(3)Cl-2 to promote hexenyl radical cyclization and Dowd-Beckwith ringexpansion of alpha-halomethyl-substituted benzocyclic 1-alkanones Reviewed

    Eietsu Hasegawa, Minami Tateyama, Tsuneaki Hoshi, Taku Ohta, Eiji Tayama, Hajime Iwamoto, Shin-ya Takizawa, Shigeru Murata

    TETRAHEDRON   70 ( 17 )   2776 - 2783   2014.4

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    A combination of 2-aryl substituted 1,3-dimethyl-benzimidazolines (DMBIHs) and tris(2,2'-bipyridine) ruthenium(II) chloride, Ru(bpy)(3)Cl-2 was used to promote photoinduced electron-transfer (PET) reactions of alpha-halomethyl-substituted benzocyclic 1-alkanones. This photo-reagent system stimulates free radical forming, cleavage of both carbon-bromine and carbon-chlorine bonds that are not activated by carbonyl groups. The resulting free radicals undergo 5-exo hexenyl cyclization as well as sequential cyclization and ring-expansion (Dowd-Beckwith) reactions to form radicals that abstract hydrogen atoms from the radical cation of DMBIH to yield the observed products. The results of a study of the effects of substituents located on the 2-aryl ring of DMBIH suggest that steric and hydrogen-bonding interactions influence the nature of the reaction pathways followed by the radical intermediates. PET reactions using an iridium complex and DMBIH were also investigated. (C) 2014 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2014.02.078

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  • Double axial chirality promoted asymmetric [2,3] Stevens rearrangement of N-cinnamyl L-alanine amide-derived ammonium ylides Reviewed

    Eiji Tayama, Noriko Naganuma, Hajime Iwamoto, Eietsu Hasegawa

    CHEMICAL COMMUNICATIONS   50 ( 52 )   6860 - 6862   2014

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    The base-induced asymmetric [2,3] Stevens rearrangement of N-cinnamyl tetraalkylammonium ylides derived from L-alanine amides proceeds via a double axially chiral intermediate to afford the corresponding alpha-substituted alanine derivatives with high enantio-and diastereoselectivities.

    DOI: 10.1039/c4cc02536a

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  • Carbon-carbon bond formation via benzoyl umpolung attained by photoinduced electron-transfer with benzimidazolines Reviewed

    Tomohito Igarashi, Eiji Tayama, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS   54 ( 50 )   6874 - 6877   2013.12

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    A photoreaction between benzoyl compounds, such as benzoylformate derivatives, and 2-(p-anisyl)-1,3-dimethylbenzimidazoline in the presence of allyl bromide was found to give various allylated alcohols. In the reaction of benzoylformates, cc-hydroxy ester enolates, for which the negative charge occurs on the carbonyl carbon of benzoyl (umpolung reactivity), are proposed to be generated as intermediates by electron-transfer from benzimidazolines to the photoexcited benzoylformates; these species react with allyl bromide to produce alpha-allyl-alpha-hydroxy esters. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tetlet.2013.10.028

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  • Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways Reviewed

    Eietsu Hasegawa, Minami Tateyama, Ryosuke Nagumo, Eiji Tayama, Hajime Iwamoto

    BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY   9   1397 - 1406   2013.7

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    Copper(II)-salt-promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives were investigated. The regioselectivities of these processes were found to be influenced by the structure of cyclopropanols as well as the counter anion of the copper(II) salts. A mechanism involving rearrangement reactions of radical intermediates and their competitive trapping by copper ions is proposed.

    DOI: 10.3762/bjoc.9.156

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  • Selective Synthesis of [2]- and [3]Catenane Tuned by Ring Size and Concentration Reviewed

    Hajime Iwamoto, Wataru Takizawa, Koji Itoh, Tatsuya Hagiwara, Eiji Tayama, Eietsu Hasegawa, Takeharu Haino

    JOURNAL OF ORGANIC CHEMISTRY   78 ( 11 )   5205 - 5217   2013.6

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    The syntheses of [2]- and [3]catenanes by olefin metathesis and oxidative acetylide coupling have been studied in detail. Pseudorotaxanes that were obtained by mixing crown ether and ammonium salts containing two terminal reactive end-groups were converted to [2]- and [3]catenane. Their yields were influenced not only by the chain length of the ammonium salts but also by the concentration of the crown ether and the ammonium salts. The strain energies of [2]catenane were responsible for the formation of [2]catenane.

    DOI: 10.1021/jo400239h

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  • 1,4-Elimination/Bronsted acid catalyzed aza-Ferrier reaction sequence as an entry to beta-amino-beta,gamma-unsaturated aldehydes Reviewed

    Eiji Tayama, Kouki Horikawa, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON   69 ( 13 )   2745 - 2752   2013.4

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    The 1,4-elimination reaction of (Z)-N-Boc-2-(4-methoxy-2-alkenyloxy)amines with Bronsted acids catalyzed aza-Ferrier reaction of the 1,4-eliminated product, thus obtained, afforded various beta-amino-beta,gamma-unsaturated aldehydes. The scope and limitation of this sequential reaction are described. (C) 2013 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2013.01.088

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  • A UNIQUE AND SIMPLE PREPARATIVE METHOD FOR alpha-ARYLPIPECOLINIC ACID ESTERS VIA BASE-INDUCED SOMMELET-HAUSER REARRANGEMENT Reviewed

    Eiji Tayama, Ryota Sato, Motoshi Ito, Hajime Iwamoto, Eietsu Hasegawa

    HETEROCYCLES   87 ( 2 )   381 - 388   2013.2

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    A unique and simple preparative method for N-cyano-alpha-arylpipecolinic acid esters via base-induced Sommelet-Hauser rearrangement, the von Braun reaction, and intramolecular alpha-alkylation is reported. The removal of the N-cyano substituent was achieved by hydrogenation and hydride reduction.

    DOI: 10.3987/COM-12-12619

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  • AN EFFECTIVE PROCEDURE TO PROMOTE AZA-PRINS CYCLIZATION REACTIONS EMPLOYING A COMBINATION OF FERRIC CHLORIDE AND AN IMIDAZOLIUM SALT IN BENZOTRIFLUORIDE Reviewed

    Chika Osawa, Minami Tateyama, Kensuke Miura, Eiji Tayama, Hajime Iwamoto, Eietsu Hasegawa

    HETEROCYCLES   86 ( 2 )   1211 - 1226   2012.12

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    Aza-Prins cyclization reactions of N-tosyl-3-butenylamine with p-methoxybenzaldehyde, 1-naphthaldehyde and 2-naphthaldehyde take place efficiently using a combination 1-butyl-3-methylimidazolium of ferric chloride and hexafluorophosphate in benzotrifluoride (Felm-BTF procedure). The new methodology, leading to formation of target N-tosyl-4-chloro-2-substituted piperidines, is superior to the one using 1-butyl-3-methylimidazolium tetrachloroferrate. The Felm-BTF procedure was also applied to aza-Prins cyclization reactions of other aldehydes. Finally, the effects of imidazolium salts on aza-Prins cyclization reaction promoted by boranetrifluoride-diethyl ether complex, leading to formation of fluorinated piperidines, were explored.

    DOI: 10.3987/COM-12-S(N)78

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  • Copper(II)-acid co-catalyzed intermolecular substitution of electron-rich aromatics with diazoesters Reviewed

    Eiji Tayama, Moe Ishikawa, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS   53 ( 38 )   5159 - 5161   2012.9

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    The intermolecular aromatic substitution of N,N-dialkylanilines and alkoxybenzenes with diazoesters is shown to proceed in the presence of catalytic amounts of both copper(II) salt and acid (Lewis or Bronsted). This method is a mild and rare metal-free C-C bond formation reaction between aromatic (sp(2)) and aliphatic (sp(3)) carbons. (C) 2012 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tetlet.2012.07.070

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  • A formal method for the de-N,N-dialkylation of Sommelet-Hauser rearrangement products Reviewed

    Eiji Tayama, Ryota Sato, Keisuke Takedachi, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON   68 ( 24 )   4710 - 4718   2012.6

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    Selective amine de-alkylation enables the conversion of Sommelet-Hauser rearrangement products into 2-aryl-2-bromoacetic acid derivatives. These compounds are valuable synthetic intermediates in the synthesis of alpha-aryl-alpha-amino or alpha-aryl-beta-amino acid derivatives. The method presented herein is a formal de-N,N-dialkylation of Sommelet-Hauser rearrangement products. (C) 2012 Elsevier Ltd. All rights reserved.

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  • 1,2-Dimethoxy-4,5-dimethylene: a new protecting group for acyclic amino acid derivatives prepared by Stevens rearrangement Reviewed

    Eiji Tayama, Keisuke Takedachi, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS   53 ( 11 )   1373 - 1375   2012.3

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    A new protecting group, 1,2-dimethoxy-4,5-dimethylene, for acyclic amino acid derivatives could be introduced by N,N-dialkylation with 1,2-bis(bromomethyl)-4,5-dimethoxybenzene (1) and removed via amine de-alkylation with acyl chlorides. The method can be used with base-induced [2,3] and [1,2] Stevens rearrangement products. (C) 2012 Elsevier Ltd. All rights reserved.

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  • Asymmetric alpha-2-tosylethenylation of N,N-dialkyl-L-amino acid esters via the formation of non-racemic ammonium enolates Reviewed

    Eiji Tayama, Tomohito Igarashi, Hajime Iwamoto, Eietsu Hasegawa

    ORGANIC & BIOMOLECULAR CHEMISTRY   10 ( 2 )   339 - 345   2012

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    Asymmetric alpha-2-tosylethenylation of (S)-2-(pyrrolidin-1-yl)propanoic acid esters was shown to produce good yields with high enantioselectivities. The reaction proceeds via the formation of a non-racemic ammonium enolate without an external source of chirality.

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  • Asymmetric alpha-2-tosylvinylation of in situ-generated N-2-tosylvinyl proline-derived ammonium ylides Reviewed

    Tomohito Igarashi, Eiji Tayama, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS   52 ( 15 )   1819 - 1821   2011.4

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    Asymmetric alpha-2-tosylvinylation of N-substituted proline esters using ethynyl tolyl sulfone as an electrophile was shown to proceed in good yield with high enantioselectivities without the addition of any bases. The reaction proceeds via the formation of N-2-tosylvinyl ammonium ylides. (C) 2011 Elsevier Ltd. All rights reserved.

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  • Highly shape-selective guest encapsulation in the precisely defined cavity of a calix[4] arene-capped metalloporphyrin Reviewed

    Hajime Iwamoto, Saori Nishi, Takeharu Haino

    CHEMICAL COMMUNICATIONS   47 ( 47 )   12670 - 12672   2011

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    We developed a metalloporphyrin-based molecular container capped with a calix[4] arene, and its rigid cavity distinguished the slight structural differences in the aromatic guests.

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  • Application of biphasic reaction procedure using ferric chloride dissolved in an imidazolium salt and benzotrifluoride (FeIm-BTF procedure) to aza-Prins cyclization reaction Reviewed

    Eietsu Hasegawa, Nohara Hiroi, Chika Osawa, Eiji Tayama, Hajime Iwamoto

    TETRAHEDRON LETTERS   51 ( 50 )   6535 - 6538   2010.12

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    Aza-Prins cyclization reaction of N-tosyl-3-butenylamine with aliphatic and aromatic aldehydes was performed using a combination of FeCl3 and 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF(6)) or 1-butyl-3-methylimidazolium tetrachloroferrate (BmimFeCl(4)) in benzotrifluoride (BTF). The desired N-tosyl-4-chloro-2-substituted piperidines were obtained from aliphatic aldehydes in comparable yields to those for the previously reported reactions in which FeCl3 was used in CH2Cl2. On the other hand, significant progress for the piperidine synthesis from aromatic aldehydes has been achieved, particularly when BmimFeCl(4) was used with FeCl3 in BTF. (C) 2010 Elsevier Ltd. All rights reserved.

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  • Copper(II) Triflate Catalyzed Intermolecular Aromatic Substitution of N,N-Disubstituted Anilines with Diazo Esters Reviewed

    Eiji Tayama, Tomoyo Yanaki, Hajime Iwamoto, Eietsu Hasegawa

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY   ( 35 )   6719 - 6721   2010.12

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    The intermolecular aromatic substitution of N,N-disubstituted anilines with diazo esters is achieved under mild conditions in the presence of a catalytic amount of copper(II) triflate (up to 89% yield). The scope and limitations regarding substrates, diazo esters, and ligands in this reaction are described.

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  • Remarkable enhancement effect of potassium tert-butoxide/THF solution in base-induced Sommelet-Hauser rearrangements Reviewed

    Eiji Tayama, Keisuke Takedachi, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON   66 ( 48 )   9389 - 9395   2010.11

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    A solution of potassium tert-butoxide in THF was shown to remarkably enhance the base-induced Sommelet-Hauser rearrangement of N-benzylic amino acid-derived ammonium ylides. (C) 2010 Elsevier Ltd. All rights reserved.

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  • Tether-assisted Synthesis of [3]Rotaxane by Olefin Metathesis Reviewed

    Hajime Iwamoto, Yukimi Yawata, Yoshimasa Fukazawa, Takeharu Haino

    CHEMISTRY LETTERS   39 ( 1 )   24 - 25   2010.1

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    The tether-assisted synthesis of [3]rotaxane by olefin metathesis is described. The bis(crown ether)s, in which two crown ethers are connected by a linker, were converted to tethered rotaxanes, followed by removal of the linkers to produce [3]rotaxane. The biscrown structures promoted the formation of the tethered rotaxane, resulting in a notable improvement in the yield of the [3]rotaxane.

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  • Highly efficient synthesis of [3]rotaxane assisted by preorganisation of pseudorotaxane using bis(crown ether)s Reviewed

    Hajime Iwamoto, Yukimi Yawata, Yoshimasa Fukazawa, Takeharu Haino

    SUPRAMOLECULAR CHEMISTRY   22 ( 11-12 )   815 - 826   2010

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    The tether-assisted synthesis of [3]rotaxane by olefin metathesis has been studied in detail. Bis(crown ether)s, in which two crown ethers are connected by a linker, were threaded onto ammonium salts bearing a terminal olefin to form pseudorotaxanes. The pseudorotaxanes were converted into tethered rotaxanes in the presence of Grubbs catalyst, followed by removal of the linkers to produce [3]rotaxanes in excellent yields. Preorganisation of the two reactive ends has led to a great improvement in the yield of [3]rotaxanes. The ring strain of the tethered rotaxanes and the flexibility of the pseudorotaxanes were responsible for the formation of the tethered rotaxanes.

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  • Shape-Selective Molecular Recognition in Confined Space Provided by Calixarene-Capped Porphirin

    Hajime Iwamoto, Saori Nishi, Takeharu Haino

    IUPAC 5th International Symposium on Novel Materials and Synthesis (NMS-V)   2009.10

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  • Energetics of guest binding to calix[4]arene molecular containers Reviewed

    Hajime Iwamoto, Kahoru Niimi, Takeharu Haino, Yoshimasa Fukazawa

    TETRAHEDRON   65 ( 35 )   7259 - 7267   2009.8

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    The synthesis of calix[4]arene-based molecular containers I and 2 along with the thermodynamic behaviors of cation binding are reported. The containers encapsulated N-methylpicolinium salts to form 1:1 host-guest complexes in chloroform. The thermodynamic investigations of the containers provide contrastive pictures for the process of their guest encapsulations. The encapsulation of I with the N-methylpicolinium cations, bearing a series of counter anions, was primarily enthalpy-driven. The enthalpic difference among the host-guest complexes of the salts was directly related to the total electrostatic stability of the ion-pairs. When 2 encapsulated a series of the N-methylpicolinium cations within its cavity, negative heat capacity changes were observed. This suggests that the changes in the solvation spheres of the container and its guest before and after the formation of the host-guest complex depend on temperature. (C) 2009 Elsevier Ltd. All rights reserved.

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  • Noncovalent Isotope Effect for Guest Encapsulation in Self-Assembled Molecular Capsules Reviewed

    Takeharu Haino, Katsunori Fukuta, Hajime Iwamoto, Suehiro Iwata

    CHEMISTRY-A EUROPEAN JOURNAL   15 ( 48 )   13286 - 13290   2009

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    DOI: 10.1002/chem.200902526

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  • Ring current models of porphyrin and conformational analysis of the dicarboxylate complex of Sn(IV) porphyrin Reviewed

    Hajime Iwamoto, Yoshimasa Fukazawa

    HETEROCYCLES   75 ( 7 )   1711 - 1723   2008.7

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    Several models for the porphyrin ring current effect are constructed based on a classical line current approximation and their performances in reproducing the observed induced shifts of ligand protons in Sn(IV)(porphyrin) dicarboxylate complexes are compared. A new model is selected and it is found that the diamagnetic ring current running on the inner 16 pi-electron circuit of the porphyrin is the main contributor together with a minor paratropic ring Current oil the outer 20 pi-electron circuit. Conformational analyses of bis(biplienyl carboxylate) complexes of Sn(IV) (tetrapherylporphyrin) in solution were carried out with this porphyrin ring current effect model.

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  • Synthesis of a molecular container having an open door that closes on guest binding Reviewed

    Takeharu Haino, Masaki Hirakata, Kahoru Niimi, Mitsuru Kouchi, Hajime Iwamoto, Yoshimasa Fukazawa

    CHEMISTRY LETTERS   37 ( 4 )   394 - 395   2008.4

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    A molecular container composed of monodeoxy-calix[4]arene and calix[4]arene is synthesized. The host binds planar cationic guests. The deoxy-aromatic ring acts as an open door when the guest is absent and closes on guest binding.

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  • Conformational control of molecular tweezers containing a disulfide bond by redox reactions Reviewed

    Hajime Iwamoto, Yusuke Hidaka, Yoshimasa Fukazawa

    TETRAHEDRON LETTERS   49 ( 2 )   277 - 280   2008.1

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    Molecular tweezers 1b having two alkyl thiol chains were prepared. Intramolecular cyclization of the thiols under oxidative conditions afforded tweezers 2b containing a disulfide bond. X-ray crystal analysis and temperature dependent H-1 NMR spectra analysis revealed that the structure of 1b has a stepped anti arrangement of the three aromatic rings, although that of 2b adopted a cleft conformation because of the intramolecular interaction between the alkyl chain and the terminal naphthalene rings. The thioldisulfide redox reaction proceeded smoothly and reversibly to control the conformation of the tweezers. (c) 2007 Elsevier Ltd. All rights reserved.

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  • Synthesis and enantioselective recognition of a calix[5]arene-based chiral receptor Reviewed

    Takeharu Haino, Hiroyuki Fukuoka, Hajime Iwamoto, Yoshimasa Fukazawa

    SUPRAMOLECULAR CHEMISTRY   20 ( 1-2 )   51 - 57   2008

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    Calix[5]arene-based artificial receptor 1 capped with chiral macrocycle 6 was synthesized and showed strong binding towards ethyltrimethylammonium derivatives via cation/pi and/or hydrogen bonding interactions. The calix[5]arene cavity provided the dissymmetric guest-binding environment in which chiral guests 9-19 were encapsulated in an enantioselective fashion. Thermodynamic studies for this chiral recognition gave an insight into the binding manner of the receptor: the enantioselective recognition is enthalpy favoured. Probably, the attractive interactions between the host and the guest gives rise to the enthalpy difference in enantioselection; however, the enthalpy gains of one of the enantiomers are compensated by entropy costs, reducing the enantioselectivity of the receptor.

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  • Two new halogenated briarane diterpenes from the Papuan gorgonian coral Junceella fragilis Reviewed

    Natsuki K. Kubota, Yuka Kobayashi, Hajime Iwamoto, Yoshimasa Fukazawa, Yasuto Uchio

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   79 ( 4 )   634 - 636   2006.4

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    Two new halogenated briarane diterpenes, (-)-2-deacetyljunceellin (1) and (-)-3-deacetyljunceellin (2), and five known diterpenoids, junceellin, praelolide, junceellolide A, B, and D were isolated from the Papuan gorgonian coral Junceella fragilis. The structures of the new metabolites were determined by extensive 2D NMR experiments and by chemical conversion. The absolute configuration of 2 was determined through the H-1 NMR study of the corresponding ester with a newly developed chiral auxiliary 3a.

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  • Two new halogenated briarane diterpenes from the Papuan gorgonian coral Junceella fragilis Reviewed

    Natsuki K. Kubota, Yuka Kobayashi, Hajime Iwamoto, Yoshimasa Fukazawa, Yasuto Uchio

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   79 ( 4 )   634 - 636   2006.4

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    Two new halogenated briarane diterpenes, (-)-2-deacetyljunceellin (1) and (-)-3-deacetyljunceellin (2), and five known diterpenoids, junceellin, praelolide, junceellolide A, B, and D were isolated from the Papuan gorgonian coral Junceella fragilis. The structures of the new metabolites were determined by extensive 2D NMR experiments and by chemical conversion. The absolute configuration of 2 was determined through the H-1 NMR study of the corresponding ester with a newly developed chiral auxiliary 3a.

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  • Structure elucidation of dicarboxylate complex of SnIV porphyrin with a ring current effect model Reviewed

    Hajime Iwamoto, Kenji Hori, Yoshimasa Fukazawa

    Tetrahedron   62 ( 12 )   2789 - 2798   2006.3

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    A new simple model of porphyrin ring current effect was proposed based on a line current approximation. It can reproduce the porphyrin-induced shifts for several Sn(IV)(tpp) and Sn(IV)(oep) dicarboxylate complexes quite satisfactorily. Perpendicular arrangement of the aromatic rings in the diaromatic-carboxylate complexes of Sn(IV)(tpp) and Sn(IV)(oep) was clarified with this porphyrin ring current effect model. There are two structures, exo and endo, in solution in dinaphthalene-1- and 2- carboxylate complexes of Sn(IV)(tpp) and Sn(IV)(oep). The exo conformer is in dynamic equilibrium with the endo form in solution. Thermodynamic data of these conformational equilibria are given. © 2006 Elsevier Ltd. All rights reserved.

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  • Structure elucidation of dicarboxylate complex of Sn-IV porphyrin with a ring current effect model

    H Iwamoto, K Hori, Y Fukazawa

    TETRAHEDRON   62 ( 12 )   2789 - 2798   2006.3

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    new simple model of porphyrin ring current effect was proposed based on a line current approximation. It can reproduce the porphyrin-induced shifts for several Sn(IV)(tpp) and Sn(IV)(oep) dicarboxylate complexes quite satisfactorily. Perpendicular arrangement of the aromatic rings in the diaromatic-carboxylate complexes of Sn(TV)(tpp) and Sn(IV)(oep) was clarified with this porphyrin ring current effect model. There are two structures, exo and endo, in solution in dinaphthalene-1- and 2-carboxylate complexes of Sn(IV)(tpp) and Sn(IV)(oep). The exo conformer is in dynamic equilibrium with the endo form in solution. Thermodynamic data of these conformational equilibria are given. (c) 2006 Elsevier Ltd. All rights reserved.

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  • Determination of absolute configuration of secondary alcohols using new chiral auxiliary and chemical shift calculation

    H Iwamoto, Y Kobayashi, T Kawatani, M Suzuki, Y Fukazawa

    TETRAHEDRON LETTERS   47 ( 10 )   1519 - 1523   2006.3

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    A new chiral carboxylic acid 1 was synthesized for determination of absolute configuration of secondary alcohols. Several chiral alcohols were converted to esters with 1. Their experimental esterification shift changes were successfully reproduced by the chemical shift simulation method combined with molecular dynamic simulation. (c) 2006 Elsevier Ltd. All rights reserved.

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  • Five new sulfur-containing polybrominated bisindoles from the red alga Laurencia brongniartii Reviewed

    NK Kubota, H Iwamoto, Y Fukazawa, Y Uchio

    HETEROCYCLES   65 ( 11 )   2675 - 2682   2005.11

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    Five new sulfur-containing polybrominated bisindole (1 similar to 5) were isolated from the red alga, Laurencia brongniartii, in addition to six related compounds (6 similar to 11), which have been previously found in the Okinawan alga. The structures of these new bisindole metabolites were elucidated on the basis of spectroscopic studies, as well as X-Ray crystallographic analysis of 1.

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  • Conformational control of flexible molecular tweezers by intramolecular CH/pi interaction

    H Iwamoto, N Takahashi, T Maeda, Y Hidaka, Y Fukazawa

    TETRAHEDRON LETTERS   46 ( 40 )   6839 - 6842   2005.10

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    The synthesis of new flexible molecular tweezers based on 3,4,8,10,11,13-hexahydro-1H,6H-2,5,9,12-tetraoxabenzo[1,2:4,5]dicyclooctene bearing two naphthalenes is presented. Intratnolecular CH/pi interaction between the alkyl ring and the two terminal naphthalenes controls the conformation to give a self-quenched cleft form. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Shielding effect of thioether C-S bond from proton chemical shifts of 4-thia-5 alpha- and 4-thia-5 beta-androstane-17-ones

    H Iwamoto, T Kawatani, Y Fukazawa

    TETRAHEDRON   61 ( 15 )   3691 - 3696   2005.4

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    4-Thia-5 alpha- and 4-thia-5 beta-androstan-17-ones (1a and 1b) were synthesized in order to obtain the NMR shielding parameters for the thioether C-S bond. The complete NMR assignment of both the proton and carbon atoms for these compounds and substituent-induced shifts (SIS) from the corresponding androstanones (2a and 2b) are presented. A combination of the electric field effect and the anisotropy of the magnetic susceptibility of the C-S bond can successfully reproduced the observed SIS values for these androstanones. (c) 2005 Elsevier Ltd. All rights reserved.

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  • Conformational analysis of dinaphthalene-1-carboxylate complex of Sn<sub>IV</sub>(tetraphenylporphyrin) Reviewed

    H. Iwamoto, Y. Fukazawa

    Heterocycles   65 ( 3 )   523 - 529   2005.3

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  • Conformal analysis of dinaphthalene-1-carboxylate complex of SNIV(tetraphenylporphyrin)

    H Iwamoto, Y Fukazawa

    HETEROCYCLES   65 ( 3 )   523 - 529   2005.3

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    Conformational analysis of dinaphthalene-1-carboxylate complex of Sn-IV(tpp) (1) in solution was carried out using temperature dependent H-1 NMR spectra and chemical shift simulation method. It was found that two vertical conformers are in equilibrium in solution for 1.

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  • A model of porphyrin ring current effect

    Hajime Iwamoto, Kenji Hori, Yoshimasa Fukazawa

    Tetrahedron Letters   46   731 - 734   2005.1

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    A new simple model of porphyrin ring current effect was proposed based on a line current approximation. It can reproduce the porphyrin-induced shifts for some Sn(IV)(tpp) dicarboxylate complexes quite satisfactorily. © 2004 Elsevier Ltd. All rights reserved.

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  • A model of porphyrin ring current effect Reviewed

    H Iwamoto, K Hori, Y Fukazawa

    TETRAHEDRON LETTERS   46 ( 5 )   731 - 734   2005.1

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    A new simple model of porphyrin ring current effect was proposed based on a line current approximation. It can reproduce the porphyrin-induced shifts for some Sn(IV)(tpp) dicarboxylate complexes quite satisfactorily. (C) 2004 Elsevier Ltd. All rights reserved.

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  • Conformational analysis of flexible compounds with chemical shift simulation

    Hajime Iwamoto, Yoshimasa Fukazawa

    Yuki Gosei Kagaku Kyokaishi/Journal of Synthetic Organic Chemistry   63 ( 11 )   1080 - 1089   2005

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    Conformational analyses of flexible compounds with a chemical shift simulation method are described. It is known that NMR chemical shifts reflect the molecular structure, and hence, our method of analysis utilizes chemical shifts. Our newly developed chemical shift simulation method together with molecular dynamic calculation succeeded in the conformational analysis of the flexible compounds
    cyclophanes, dicarboxylate complexes of Sn(IV) porphyrins and supramolecular complexes.

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  • Synthesis of molecular tweezers bearing two porphyrins and its complexation toward electron acceptors

    H Iwamoto, M Yamaguchi, S Hiura, Y Fukazawa

    HETEROCYCLES   63 ( 9 )   2005 - 2011   2004.9

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    Synthesis of new flexible molecular tweezers 1.M-2 (M = 2H, Co, Zn, Cu, Ni) based on bis-dioxa[2.2]orthocyclophane bearing two porphyrins is presented. The molecular tweezers (1.(2H)(2)) can bind not only planar pi-electron acceptors, such as tetracyanoquinodimethane (TCNQ) and tetracyanobenzene (TCNB) but also a spherical guest C-60.

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  • Magnetic shielding effect of amine and ammonium groups obtained from proton chemical shifts of androstane derivatives

    H Iwamoto, Y Kondo, T Kawatani, T Haino, Y Fukazawa

    TETRAHEDRON LETTERS   44 ( 32 )   5975 - 5978   2003.8

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    4-Aza-5alpha-androstanone(1alpha) and 4-aza-5beta-androstanone(1beta) were synthesized in order to obtain the NMR shielding parameters for the secondary amine group. A combination of the electric field effect and the anisotropy of the magnetic susceptibility of the C-N bond can successfully reproduce the observed SIS values for these androstanes. Drastic chemical shift change of protons near-by nitrogen atom of ammonium salt was observed and shielding parameter for the secondary ammonium group was also obtained. (C) 2003 Elsevier Ltd. All rights reserved.

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  • Convenient synthesis of [3]catenane by olefin metathesis dimerizations

    H Iwamoto, K Itoh, H Nagamiya, Y Fukazawa

    TETRAHEDRON LETTERS   44 ( 31 )   5773 - 5776   2003.7

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    [3]Catenane 5a and 5b were synthesized conveniently by olefin metathesis dimerization of pseudorotaxanes 3a and 3b. The yields of 5a and 5b were influenced by concentrations of 3a and 3b, and a ring size of a center wheel of [3]catenane. (C) 2003 Elsevier Ltd. All rights reserved.

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  • Synthesis and binding behavior of a Zn(II)-porphyrin having calix[5]arene cap

    H Iwamoto, Y Yukimasa, Y Fukazawa

    TETRAHEDRON LETTERS   43 ( 45 )   8191 - 8194   2002.11

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    The synthesis and binding behavior of a Zn(II)-porphyrin having a calix[5]arene cap are presented. In order to synthesize such a bridged porphyrin, 5,15-bis(7-carboxy-1-naphthyl)-10,20-diphenylporphyrin having the syn arrangement of two naphthalene rings has been prepared. Amidation of the porphyrin and calix[5]arene having two amino functions and subsequent treatment of Zn(OAc)(2) gave a calix[5]arene capped Zn-porphyrin. Calix[5]arene-Zn-porphyrin was found to bind 4-methylpyridine much stronger than TPP-Zn. (C) 2002 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0040-4039(02)01655-6

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  • Dynamic structure of inclusion complexes of monodeoxycalix[4]arene with small organic guests in solution

    H Iwamoto, M Hirakata, S Usui, T Haino, Y Fukazawa

    TETRAHEDRON LETTERS   43 ( 1 )   85 - 87   2002.1

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    Structure elucidation of the inclusion complexes of monodeoxycalix[4]arene with small organic guests was carried out by X-ray crystallographic analysis and molecular dynamic simulation. Although the guest moves rapidly in the host cavity, the time averaged structure resembles the one obtained by the X-ray crystallography. Chemical shift simulation succeeded to reproduce the observed complexation induced shift. (C) 2001 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0040-4039(01)02062-7

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  • Estimation of magnetic anisotropy in polycyclic aromatics

    H Iwamoto, T Kawatani, Y Fukazawa

    TETRAHEDRON LETTERS   42 ( 8 )   1551 - 1553   2001.2

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    Dihydro-dibenzophenanthrene derivatives 1a (1b) were synthesised in order to obtain the NMR shielding parameters for naphthalene ring. The H-1 NMR assignment of 1a and substituent-induced shifts (SIS) from the corresponding androstanone ethylene ketal (2) are presented. A simple sum of the magnetic shielding of benzene rings can satisfactorily reproduced the observed SIS values due to the naphthalene ring of 1. (C) 2001 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0040-4039(00)02283-8

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  • Conformational analysis by chemical shift simulation: structure of 1,4,11,14-tetraoxa[4.4]metacyclophane

    H Iwamoto, YY Yang, S Usui, Y Fukazawa

    TETRAHEDRON LETTERS   42 ( 1 )   49 - 51   2001.1

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    Conformational analysis of 1,4,11,14-tetraoxa[4.4]metacyclophane was carried out using a combination of the molecular mechanics calculation, analysis of the temperature dependent H-1 NMR signal change and the chemical shift simulation method. The molecular mechanics calculation with Amber* force-field gave the two structures, one is highly symmetric C-2v and the other is C-i symmetric. The latter is identical to the structure found in the crystal. Both of the structures were confirmed by the chemical shift simulation. (C) 2000 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0040-4039(00)01876-1

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  • Thermodynamic study on supramolecular complex formation of fullerene with calix[5]arenes in organic solvents

    M Yanase, M Matsuoka, Y Tatsumi, M Suzuki, H Iwamoto, T Haino, Y Fukazawa

    TETRAHEDRON LETTERS   41 ( 4 )   493 - 497   2000.1

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    Thermodynamic parameters for the supramolecular complex formation of fullerene C-60 With calix[5]arene receptors are reported. The entropy change in chloroform is negative, but in toluene is positive, suggesting the tight solvation around the guest in toluene. Desolvation of the guest plays an important role in the supramolecular complex formation in toluene. (C) 2000 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0040-4039(99)02099-7

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  • A synthetic approach towards the identification of periplaneta sex pheromones

    Hajime Iwamoto, Takeo Harada, Takashi Takahashi, Shozo Takahashi

    Heterocycles   47   139 - 142   1998.12

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    Syntheses of the proposed structure of periplanone J (3) and its diastereomer (4), and the discussion on the true structure of PJ based on spectral analysis of 3,4 and the natural PJ are described.

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  • Synthesis of the chiral CD rings of paclitaxel from 2-deoxy-D-ribose: Novel 1,2-addition of a dienolate to a chiral ketone

    T Takahashi, Y Hirose, H Iwamoto, T Doi

    JOURNAL OF ORGANIC CHEMISTRY   63 ( 17 )   5742 - 5743   1998.8

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    DOI: 10.1021/jo9810563

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  • Construction of A and C ring intermediates for taxol by using (3+2)-cycloaddition of nitrile oxide

    T Takahashi, H Iwamoto

    TETRAHEDRON LETTERS   38 ( 14 )   2483 - 2486   1997.4

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    Syntheses of the A-ring and the chiral C-ring model of taxol by using the intramolecular nitrile oxide cycloaddition and its diastereoselectivity based on MM2 transition state model are described. (C) 1997 Elsevier Science Ltd.

    DOI: 10.1016/S0040-4039(97)00372-9

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  • Synthesis of taxoid ring systems: AC -> ABC approach by way of intramolecular alkylation Reviewed

    T. Takahashi, H. Iwamoto, K. Nagashima, T. Okabe, T. Doi

    Angewandte Chemie, International Edition in English   36 ( 12 )   1319 - 1321   1997.1

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  • A biomimetic approach to taxol: Stereoselective synthesis of a 12-membered ring ene-epoxide

    T Takahashi, T Okabe, H Iwamoto, Y Hirose, H Yamada, T Doi, S Usui, Y Fukazawa

    ISRAEL JOURNAL OF CHEMISTRY   37 ( 1 )   31 - 37   1997

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    The stereoselective synthesis of a taxol intermediate via a biomimetic route is described. Aldol condensation of gamma-butyrolactone and citral derivatives generated three stereogenic centers at positions C1, C2, and C11 corresponding to taxol. Intramolecular alkylation of the cyanohydrin ether efficiently formed the 12-membered ring system in which stereoselective reduction, followed by directed epoxidation, afforded the key intermediate epoxide.

    DOI: 10.1002/ijch.199700006

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MISC

  • Noncovalent Isotope Effect for Guest Encapsulation in Self-Assembled Molecular Capsules (vol 15, pg 13286, 2009)

    T. Haino, K. Fukuta, H. Iwamoto, S. Iwata

    CHEMISTRY-A EUROPEAN JOURNAL   16 ( 4 )   1100 - 1100   2010

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    DOI: 10.1002/chem.200902526

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Research Projects

  • Construction of a catenan library using fluorous tags to explore the functional search of catenane molecules

    Grant number:16K05690

    2016.4 - 2019.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    Iwamoto Hajime

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    Grant amount:\4940000 ( Direct Cost: \3800000 、 Indirect Cost:\1140000 )

    Synthesis of catenanes was carried out by olefin metathesis, oxidative homo-coupling reaction of terminal alkynes, and Husigen reaction between alkyne with azide. Reaction conditions to introduce fluorous tags into nitrogen atoms of catenanes was investigated. Thus, trifluoromethanesulfonyl- and pentafluorobenzenesulfonyl-groups were introduced to catenanes to obtain the corresponding fluorous-tagged catenanes in good yields. Due to the steric hindrance of sulfonyl groups, rotation of the rings of the catenanes was blocked to give topological isomers.

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  • Evaluation of intermolecular interaction within artificial receptors showing highly shape-selective guest encapslation

    Grant number:24550043

    2012.4 - 2015.3

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (C)

    Awarding organization:Japan Society for the Promotion of Science

    IWAMOTO Hajime

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    Grant amount:\5590000 ( Direct Cost: \4300000 、 Indirect Cost:\1290000 )

    We synthesized artificial receptors which have a cavity formed from a calixarene and a metal porphyrin. We examined their guest binding behavior by means of variable-temperature proton NMR spectroscopy and UV-Vis spectroscopy. We have found that our synthetic receptors distinguish the slight structural differences in their guests due to stabilized H2O molecules in their cavities. Their complex structures were determined by assistance of our developed chemical shift calculation program. CH-π interaction have played a major role in the complexation.

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  • Creation of Chromic[3] catenane controlled by its unique motion

    Grant number:22750035

    2010 - 2011

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Young Scientists (B)

    Awarding organization:Japan Society for the Promotion of Science

    IWAMOTO Hajime

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    Grant amount:\4160000 ( Direct Cost: \3200000 、 Indirect Cost:\960000 )

    [3] Catenanes, which change their color according to external stimuli such as temperature and metal ions, were investigated.[3] Catenanes having chromophores were synthesized. On addition of diamine to their solution, UV spectra changes of their solution were observed with a couple of isosbestic points. Variable-temperature fluorescence spectra showed red shift of emission maximum with increasing temperature.

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  • Creation of self-duplicated system on rotaxane synthesis

    Grant number:19750035

    2007 - 2008

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Young Scientists (B)

    Awarding organization:Japan Society for the Promotion of Science

    IWAMOTO Hajime

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    Grant amount:\2040000 ( Direct Cost: \1800000 、 Indirect Cost:\240000 )

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  • ロタキサンの運動性により、平面π電子化合物包接能を制御するクレフト分子の創製

    Grant number:16750036

    2004 - 2005

    System name:科学研究費助成事業

    Research category:若手研究(B)

    Awarding organization:日本学術振興会

    岩本 啓

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    Grant amount:\2100000 ( Direct Cost: \2100000 )

    カテナン、ロタキサンのような機械的な結合を持ち、複雑な構造を有する分子は、新規な材料としての応用、ナノスケールの分子デバイスや分子スイッチとしての可能性から、超分子化学の分野で非常に注目を集めている。カテナンやロタキサンの持つ機械的な結合によって生じる、回転運動、往復運動、ねじれ運動、伸縮運動といった様々な運動性は、外部からの化学的、電気的、光化学的な刺激によって制御することが可能である。以前ジオキサ[2.2]-オルトシクロファン骨格を持つクレフト分子が、π-π相互作用により電子受容能を有する平面π電子化合物を包接することを見いだした。そこで、このクレフト分子にロタキサンの運動性、および運動の制御能を導入し、平面π電子化合物選択的捕捉能などの新規な機能発現を検討した。
    ジオキサ[2.2]-オルトシクロファン骨格を持つクレフト分子の両末端に、環状分子部位となるクラウンエーテルを導入した分子を合成した。得られたクレフト分子と平面π電子化合物との包接能を検討したところ、テトラシアノキノジメタン、テトラシアノベンゼンを二枚のナフタレン環で挟むようにして包接することを明らかにした。次にクレフト分子とクラウンエーテルと相互作用するアンモニウムカチオンを2個有する軸分子との会合挙動をNMRを用いて観測した。その結果、クラウンエーテルとアンモニウムカチオンの相互作用により、クレフト分子は擬ロタキサンを形成することが明らかとなった。またこの擬ロタキサンは、テトラシアノキノジメタン、テトラシアノベンゼンを包接することが明らかとなった。

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  • ANALYSIS OF DYNAMIC STRUCTURE WITH CHEMICAL SHIFT SIMULATION METHOD

    Grant number:15350025

    2003 - 2005

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (B)

    Awarding organization:Japan Society for the Promotion of Science

    FUKAZAWA Yoshimasa, IWAMOTO Hajime

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    Grant amount:\15000000 ( Direct Cost: \15000000 )

    Determination of significantly populated conformers in extremely flexible molecules is a matter of long-standing interest. It is desirable to develop an efficient method for the conformational analysis of the flexible compounds. NMR chemical shifts reflect molecular structure. Hence, variation in the local environment affects chemical shieldings, and the change in chemical shifts of nuclei caused by adjacent substituents provides valuable information about the relative arrangement of the nuclei under study with respect to these nearby substituents. The chemical shift changes caused by the nearby substituents can thus be applicable for conformational analysis. From this point of view, we have developed an efficient method for conformational analysis of flexible organic compounds by using chemical shift simulation technique. The followings are the results of the project.
    (1) Magnetic shielding effects of polar functional groups were successfully estimated and were applied for the conformational analysis of the flexible compounds, including cyclophanes, molecular tweezers, and their supramolecular complexes.
    (2) A very useful model of porphyrin ring current effect was developed by using a classical line current approximation. It was found that the model can successfully elucidate the structures of several dicarboxylate complexes of Sn^<(IV)> porphyrins in solution.
    (3) The newly developed method for the conformational analysis by using chemical shift simulation technique was found to be highly efficient for the structure elucidation of flexible organic compounds.

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  • 固相合成法による、ダイオキシン類レセプターライブラリーの構築

    Grant number:12740349

    2000 - 2001

    System name:科学研究費助成事業

    Research category:奨励研究(A)

    Awarding organization:日本学術振興会

    岩本 啓

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    Grant amount:\2000000 ( Direct Cost: \2000000 )

    ポリクロロダイベンゾ-p-ダイオキシン(通称ダイオキシン)類や、ポリクロロダイベンゾフラン類は、現在の環境レベルの汚染で、人体に生殖障害や免疫抑制などの影響を及ぼす可能性があるために世界各国で汚染軽減対策が進められている。そこで、ダイオキシン類が有している平面π電子とπ-πスタッキングするクレフト型分子を合成し、ホスト分子の包接によってダイオキシン類の捕捉、回収が可能と考えた。またクレフト型分子の合成に、固相合成法を用いることでダイオキシンレセプターライブラリーの構築ができると考えた。
    固相でクレフト型分子を合成するため、5置換ベンゼン、および6置換ベンゼンからリンカーをのばしたテトラキスブロモメチルベンゼン化合物の合成を行った。液相反応において、テトラキスブロモメチルベンゼン誘導体とカテコール誘導体との反応を行い、クレフト型分子の合成、反応条件の最適化を行った。その結果6置換ベンゼンでは効果的に平面π電子化合物を取り込む構造になりにくいことがわかった。そこで5置換ベンゼンから誘導されるテトラキスブロモメチルベンゼン誘導体と4-ブロモカテコールとのエーテル化、続く4-アミノカテコール誘導体とのエーテルル化を行い、スキャホールドとなるクレフト型分子の合成を行った。Wang樹脂に、得られたクレフト型分子をエステル結合で導入した。現在、固相担持クレフト型分子上におけるハロゲン化アリールに対する一酸化炭素挿入反応によるアミドの合成と、アミノ基へのカルボニル化合物の導入を検討している。また液相反応によって得られた、ポルフィリン環を導入したクレフト型分子が、ダイオキシンの骨格に含まれるジオキサン部位を効率よく包接することを見いだした。

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  • Construction of supramolecular system toward the investigation of biological events

    Grant number:10304053

    1998 - 2000

    System name:Grants-in-Aid for Scientific Research

    Research category:Grant-in-Aid for Scientific Research (A).

    Awarding organization:Japan Society for the Promotion of Science

    FUKAZAWA Yoshimasa, IWAMOTO Hajime, HAINO Takeharu

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    Grant amount:\37400000 ( Direct Cost: \37400000 )

    Molecular recognition based on the formation of host-guest complex is a fundamental chemical process. Enzymes, antibodies, receptors, and carriers all use the molecular recognition events. For the purpose of understanding and mimicking molecular recognition processes, host-guest chemistry playing a very important roll and simplified artificial receptors are useful to understand the nature of the binding on a molecular level. We have succeeded in synthesizing several artificial receptors for binding apolar organic guests such as fullerenes and several heterocycles. Calixarenes were employed as the cavity carrying unit. It was found that the calix[5]arene is a useful receptor for fullerene and connecting the two units of the receptor by covalent or non-covalent bonds resulted in the strong binding of the fullerenes. Both the uptake and release of the fullerene can be easily controlled with or without the protic acid in organic media using a self-assembling calixarene host having urea functionality. Several calixarene hosts having polar functionalities were also synthesized to examine the cooperative role of the hydrogen bonding and other non-directional forces (van del Waals and CH-π interactions and so on) for the effective binding of the polar guest such as cyclic ureas and diketopiperazines. The freedom of movement of the bound guests was analyzed by both the molecular dynamic simulation and nmr chemical shift simulation procedure. Molecular tweezers type hosts were also synthesized in order to study the effective binding the planar guests with charge transfer type interaction in organic media. Both donor-acceptor-donor and donor-acceptor-acceptor sandwich type layered arrangements were observed in the supramolecular complexes.

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Teaching Experience

  • 大型機器分析技術

    2023
    Institution name:新潟大学

  • 領域概説 B (理学)

    2023
    Institution name:新潟大学

  • 統合化学入門

    2023
    Institution name:新潟大学

  • 化学特論II

    2023
    Institution name:新潟大学

  • 化学コロキウム

    2022
    Institution name:新潟大学

  • 理学スタディ・スキルズ

    2022
    Institution name:新潟大学

  • 課題研究

    2021
    Institution name:新潟大学

  • 構造活性相関論

    2021
    Institution name:新潟大学

  • 構造有機化学特論

    2021
    Institution name:新潟大学

  • 課題研究 a

    2020
    Institution name:新潟大学

  • 課題研究 b

    2020
    Institution name:新潟大学

  • 数理物質科学の最前線

    2020
    Institution name:新潟大学

  • 化学コロキウム

    2018
    Institution name:新潟大学

  • 有機化学Ⅳ

    2017
    Institution name:新潟大学

  • 化学基礎実習a

    2017
    Institution name:新潟大学

  • 化学基礎実習b

    2017
    Institution name:新潟大学

  • 理学スタディ・スキルズ

    2017
    -
    2022
    Institution name:新潟大学

  • 化学特論Ⅰ

    2017
    Institution name:新潟大学

  • Advances in Physics and Chemistry

    2017
    Institution name:新潟大学

  • Basic Chemistry Ⅱ

    2016
    Institution name:新潟大学

  • 自然科学総論Ⅰ

    2015
    Institution name:新潟大学

  • 科学技術英語

    2013
    -
    2019
    Institution name:新潟大学

  • コミュニケーション演習

    2013
    -
    2019
    Institution name:新潟大学

  • 化学実験I

    2013
    -
    2016
    Institution name:新潟大学

  • 課題研究(化学科)

    2013
    -
    2016
    Institution name:新潟大学

  • 数理物質科学特定研究ⅡB(化学)

    2013
    -
    2015
    Institution name:新潟大学

  • 数理物質科学特定研究Ⅰ(化学)

    2013
    -
    2015
    Institution name:新潟大学

  • 数理物質科学演習Ⅰ(化学)

    2013
    -
    2015
    Institution name:新潟大学

  • 数理物質科学特定研究ⅡA(化学)

    2013
    -
    2015
    Institution name:新潟大学

  • 化学コロキュウム

    2012
    Institution name:新潟大学

  • 有機化学特論

    2012
    Institution name:新潟大学

  • 有機化学演習

    2010
    Institution name:新潟大学

  • 化学基礎C

    2010
    -
    2022
    Institution name:新潟大学

  • 構造有機化学

    2010
    -
    2016
    Institution name:新潟大学

  • 基礎化学Ⅰ

    2010
    Institution name:新潟大学

  • 構造有機化学特論

    2009
    -
    2021
    Institution name:新潟大学

  • 構造活性相関論

    2009
    -
    2021
    Institution name:新潟大学

  • 課題研究

    2009
    -
    2019
    Institution name:新潟大学

  • 化学実験

    2009
    -
    2016
    Institution name:新潟大学

  • 安全教育

    2009
    -
    2010
    Institution name:新潟大学

  • 化学基礎A

    2009
    Institution name:新潟大学

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