2021/05/16 更新

写真a

イワモト ハジメ
岩本 啓
IWAMOTO Hajime
所属
教育研究院 自然科学系 数理物質科学系列 准教授
自然科学研究科 准教授
理学部 准教授
職名
准教授
外部リンク

学位

  • 博士(工学) ( 1998年3月   東京工業大学 )

  • 修士(工学) ( 1995年3月   東京工業大学 )

  • 工学士 ( 1993年3月   東京工業大学 )

研究分野

  • ライフサイエンス / 生物有機化学

  • ナノテク・材料 / 機能物性化学

  • ナノテク・材料 / 構造有機化学、物理有機化学

経歴

  • 新潟大学   自然科学研究科   准教授

    2009年2月 - 現在

  • 新潟大学   化学科   准教授

    2009年2月 - 2017年3月

学歴

  • 東京工業大学   理工学研究科   化学工学専攻

    - 1998年3月

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    国名: 日本国

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  • 東京工業大学   工学部   化学工学科

    - 1993年3月

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    国名: 日本国

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論文

  • Protocol for visible-light-promoted desulfonylation reactions utilizing catalytic benzimidazolium aryloxide betaines and stoichiometric hydride donor reagents 査読

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

    J. Org. Chem.85   4344 - 4353   2020年

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    掲載種別:研究論文(学術雑誌)  

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

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

    Journal of Organic Chemistry83 ( 18 ) 10813 - 10825   2018年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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 査読

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

    Journal of Organic Chemistry83 ( 7 ) 3921 - 3927   2018年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society  

    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 査読

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

    HORTICULTURE JOURNAL86 ( 4 ) 463 - 469   2017年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元: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 査読

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

    TETRAHEDRON72 ( 48 ) 7805 - 7812   2016年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

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

    JOURNAL OF ORGANIC CHEMISTRY81 ( 7 ) 2692 - 2703   2016年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    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 査読

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

    CHEMICAL COMMUNICATIONS52 ( 2 ) 319 - 322   2016年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    [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 査読

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

    TETRAHEDRON71 ( 34 ) 5494 - 5505   2015年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

    Eietsu Hasegawa, Saki Arai, Eiji Tayama, Hajime Iwamoto

    JOURNAL OF ORGANIC CHEMISTRY80 ( 3 ) 1593 - 1600   2015年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    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 査読

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

    AUSTRALIAN JOURNAL OF CHEMISTRY68 ( 11 ) 1648 - 1652   2015年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元: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 査読

    Eiji Tayama, Kouki Horikawa, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS55 ( 19 ) 3041 - 3044   2014年5月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

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

    TETRAHEDRON70 ( 17 ) 2776 - 2783   2014年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

    Eiji Tayama, Noriko Naganuma, Hajime Iwamoto, Eietsu Hasegawa

    CHEMICAL COMMUNICATIONS50 ( 52 ) 6860 - 6862   2014年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    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 査読

    Tomohito Igarashi, Eiji Tayama, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS54 ( 50 ) 6874 - 6877   2013年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

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

    BEILSTEIN JOURNAL OF ORGANIC CHEMISTRY9   1397 - 1406   2013年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:BEILSTEIN-INSTITUT  

    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 査読

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

    JOURNAL OF ORGANIC CHEMISTRY78 ( 11 ) 5205 - 5217   2013年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    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 査読

    Eiji Tayama, Kouki Horikawa, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON69 ( 13 ) 2745 - 2752   2013年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

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

    HETEROCYCLES87 ( 2 ) 381 - 388   2013年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

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

    HETEROCYCLES86 ( 2 ) 1211 - 1226   2012年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

    Eiji Tayama, Moe Ishikawa, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS53 ( 38 ) 5159 - 5161   2012年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

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

    TETRAHEDRON68 ( 24 ) 4710 - 4718   2012年6月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

    Eiji Tayama, Keisuke Takedachi, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS53 ( 11 ) 1373 - 1375   2012年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

    Eiji Tayama, Tomohito Igarashi, Hajime Iwamoto, Eietsu Hasegawa

    ORGANIC & BIOMOLECULAR CHEMISTRY10 ( 2 ) 339 - 345   2012年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    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 査読

    Tomohito Igarashi, Eiji Tayama, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON LETTERS52 ( 15 ) 1819 - 1821   2011年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

    Hajime Iwamoto, Saori Nishi, Takeharu Haino

    CHEMICAL COMMUNICATIONS47 ( 47 ) 12670 - 12672   2011年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:ROYAL SOC CHEMISTRY  

    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 査読

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

    TETRAHEDRON LETTERS51 ( 50 ) 6535 - 6538   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

    Eiji Tayama, Tomoyo Yanaki, Hajime Iwamoto, Eietsu Hasegawa

    EUROPEAN JOURNAL OF ORGANIC CHEMISTRY ( 35 ) 6719 - 6721   2010年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-BLACKWELL  

    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.

    DOI: 10.1002/ejoc.201001083

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

    Eiji Tayama, Keisuke Takedachi, Hajime Iwamoto, Eietsu Hasegawa

    TETRAHEDRON66 ( 48 ) 9389 - 9395   2010年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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.

    DOI: 10.1016/j.tet.2010.09.125

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

    Hajime Iwamoto, Yukimi Yawata, Yoshimasa Fukazawa, Takeharu Haino

    CHEMISTRY LETTERS39 ( 1 ) 24 - 25   2010年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    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.

    DOI: 10.1246/cl.2010.24

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

    Hajime Iwamoto, Yukimi Yawata, Yoshimasa Fukazawa, Takeharu Haino

    SUPRAMOLECULAR CHEMISTRY22 ( 11-12 ) 815 - 826   2010年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TAYLOR & FRANCIS LTD  

    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.

    DOI: 10.1080/10610278.2010.514611

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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年10月

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    記述言語:英語   掲載種別:研究論文(国際会議プロシーディングス)  

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

    Hajime Iwamoto, Kahoru Niimi, Takeharu Haino, Yoshimasa Fukazawa

    TETRAHEDRON65 ( 35 ) 7259 - 7267   2009年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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.

    DOI: 10.1016/j.tet.2009.01.021

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

    Takeharu Haino, Katsunori Fukuta, Hajime Iwamoto, Suehiro Iwata

    CHEMISTRY-A EUROPEAN JOURNAL15 ( 48 ) 13286 - 13290   2009年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:WILEY-V C H VERLAG GMBH  

    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 査読

    Hajime Iwamoto, Yoshimasa Fukazawa

    HETEROCYCLES75 ( 7 ) 1711 - 1723   2008年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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.

    DOI: 10.3987/COM-08-11361

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

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

    CHEMISTRY LETTERS37 ( 4 ) 394 - 395   2008年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    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.

    DOI: 10.1246/cl.2008.394

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

    Hajime Iwamoto, Yusuke Hidaka, Yoshimasa Fukazawa

    TETRAHEDRON LETTERS49 ( 2 ) 277 - 280   2008年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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.

    DOI: 10.1016/j.tetlet.2007.11.056

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

    Takeharu Haino, Hiroyuki Fukuoka, Hajime Iwamoto, Yoshimasa Fukazawa

    SUPRAMOLECULAR CHEMISTRY20 ( 1-2 ) 51 - 57   2008年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:TAYLOR & FRANCIS LTD  

    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.

    DOI: 10.1080/10610270701742553

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

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

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN79 ( 4 ) 634 - 636   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    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.

    DOI: 10.1246/bcsj.79.634

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

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

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN79 ( 4 ) 634 - 636   2006年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:CHEMICAL SOC JAPAN  

    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 査読

    Hajime Iwamoto, Kenji Hori, Yoshimasa Fukazawa

    Tetrahedron62 ( 12 ) 2789 - 2798   2006年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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.

    DOI: 10.1016/j.tet.2006.01.020

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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

    TETRAHEDRON62 ( 12 ) 2789 - 2798   2006年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 LETTERS47 ( 10 ) 1519 - 1523   2006年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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.

    DOI: 10.1016/j.tetlet.2006.01.011

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

    NK Kubota, H Iwamoto, Y Fukazawa, Y Uchio

    HETEROCYCLES65 ( 11 ) 2675 - 2682   2005年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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/π interaction

    Hajime Iwamoto, Nobuaki Takahashi, Takuma Maeda, Yusuke Hidaka, Yoshimasa Fukazawa

    Tetrahedron Letters46 ( 40 ) 6839 - 6842   2005年10月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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

    DOI: 10.1016/j.tetlet.2005.08.016

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

    Hajime Iwamoto, Takefumi Kawatani, Yoshimasa Fukazawa

    Tetrahedron61 ( 15 ) 3691 - 3696   2005年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    4-Thia-5α- and 4-thia-5β-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. © 2005 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2005.02.015

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

    H. Iwamoto, Y. Fukazawa

    Heterocycles65 ( 3 ) 523 - 529   2005年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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

    H Iwamoto, Y Fukazawa

    HETEROCYCLES65 ( 3 ) 523 - 529   2005年3月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 Letters46   731 - 734   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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.

    DOI: 10.1016/j.tetlet.2004.12.028

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  • A model of porphyrin ring current effect 査読

    H Iwamoto, K Hori, Y Fukazawa

    TETRAHEDRON LETTERS46 ( 5 ) 731 - 734   2005年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 Chemistry63 ( 11 ) 1080 - 1089   2005年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:Society of Synthetic Organic Chemistry  

    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.

    DOI: 10.5059/yukigoseikyokaishi.63.1080

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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

    HETEROCYCLES63 ( 9 ) 2005 - 2011   2004年9月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 LETTERS44 ( 32 ) 5975 - 5978   2003年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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.

    DOI: 10.1016/S0040-4039(03)01486-2

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

    H Iwamoto, K Itoh, H Nagamiya, Y Fukazawa

    TETRAHEDRON LETTERS44 ( 31 ) 5773 - 5776   2003年7月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    [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.

    DOI: 10.1016/S0040-4039(03)01424-2

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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 LETTERS43 ( 45 ) 8191 - 8194   2002年11月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 LETTERS43 ( 1 ) 85 - 87   2002年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 LETTERS42 ( 8 ) 1551 - 1553   2001年2月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 LETTERS42 ( 1 ) 49 - 51   2001年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 LETTERS41 ( 4 ) 493 - 497   2000年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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

    Heterocycles47   139 - 142   1998年12月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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 CHEMISTRY63 ( 17 ) 5742 - 5743   1998年8月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:AMER CHEMICAL SOC  

    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 LETTERS38 ( 14 ) 2483 - 2486   1997年4月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:PERGAMON-ELSEVIER SCIENCE LTD  

    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 査読

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

    Angewandte Chemie, International Edition in English36 ( 12 ) 1319 - 1321   1997年1月

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    記述言語:英語   掲載種別:研究論文(学術雑誌)  

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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 CHEMISTRY37 ( 1 ) 31 - 37   1997年

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    記述言語:英語   掲載種別:研究論文(学術雑誌)   出版者・発行元:LASER PAGES PUBL LTD  

    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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