2021/05/15 更新

写真a

ハセガワ エイエツ
長谷川 英悦
HASEGAWA Eietsu
所属
教育研究院 自然科学系 数理物質科学系列 教授
自然科学研究科 数理物質科学専攻 教授
理学部 理学科 教授
職名
教授
外部リンク

学位

  • 理学博士 ( 1985年3月   東北大学 )

研究キーワード

  • グリーンケミストリー

  • 電子移動

  • 有機光化学

  • ラジカルイオン

  • ラジカル

研究分野

  • ナノテク・材料 / 構造有機化学、物理有機化学

  • ライフサイエンス / 生物有機化学

  • ナノテク・材料 / 有機合成化学

経歴(researchmap)

  • 新潟大学 理学部 理学科 化学プログラム   教授

    2017年4月 - 現在

      詳細を見る

  • 新潟大学   自然科学研究科 数理物質科学専攻   教授

    2010年4月 - 現在

      詳細を見る

  • 新潟大学   理学部 化学科   教授

    2006年6月 - 2017年3月

      詳細を見る

  • カナダ国立研究機構ステイシー分子科学研究所   客員研究員(文部省在外研究員)

    1999年3月

      詳細を見る

  • 新潟大学   理学部 化学科   助教授

    1992年4月 - 2006年5月

      詳細を見る

  • 米国ピッツバーグ大学   化学科   客員助教授(文部省在外研究員)

    1992年3月 - 1993年1月

      詳細を見る

  • 新潟大学   理学部 化学科   助手

    1987年10月 - 1992年3月

      詳細を見る

  • 米国メリーランド大学   化学科   博士研究員

    1986年2月 - 1987年9月

      詳細を見る

▶ 全件表示

経歴

  • 新潟大学   理学部 理学科   教授

    2017年4月 - 現在

  • 新潟大学   自然科学研究科 数理物質科学専攻   教授

    2010年4月 - 現在

  • 新潟大学   化学科   教授

    2006年6月 - 2017年3月

  • 新潟大学   化学科   准教授

    1992年4月 - 2006年5月

  • 新潟大学   化学科   助手

    1987年10月 - 1992年3月

学歴

  • 東北大学   Graduate School of Science   Department of Chemistry

    - 1985年3月

      詳細を見る

  • 山形大学   理学部   化学科

    - 1980年3月

      詳細を見る

所属学協会

 

論文

  • Competitive Desulfonylative Reduction and Oxidation of α-Sulfonylketones Promoted by Photoinduced Electron Transfer with 2-Hydroxyaryl-1,3-dimethylbenzimidazolines under Air

    Eietsu Hasegawa, Shyota Nakamura, Kazuki Oomori, Tsukasa Tanaka, Hajime Iwamoto, Kan Wakamatsu

    The Journal of Organic Chemistry   2021年2月

     詳細を見る

    掲載種別:研究論文(学術雑誌)   出版者・発行元:American Chemical Society ({ACS})  

    DOI: 10.1021/acs.joc.0c02666

    researchmap

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

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

    ACS omega5 ( 13 ) 7651 - 7665   2020年4月

     詳細を見る

    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 ({ACS})  

    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

    PubMed

    researchmap

  • Protocol for Visible-Light-Promoted Desulfonylation Reactions Utilizing Catalytic Benzimidazolium Aryloxide Betaines and Stoichiometric Hydride Donor Reagents. 査読 国際誌

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

    The Journal of organic chemistry85 ( 6 ) 4344 - 4353   2020年3月

     詳細を見る

    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 ({ACS})  

    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

    PubMed

    researchmap

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

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

    The Journal of organic chemistry83 ( 18 ) 10813 - 10825   2018年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    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 anion and a sulfonyl radical or that of an amidyl or aminyl radical and sulfinate anion, depending on the nature of the N-substituent on the substrate. An intermolecular version of this protocol, in which 1-methyl-2-naphthol and 1,3-dimethyl-2-phenylbenzimidazoline are used concomitantly, was also examined.

    DOI: 10.1021/acs.joc.8b01536

    PubMed

    researchmap

  • Benzimidazolium Naphthoxide Betaine Is a Visible Light Promoted Organic Photoredox Catalyst. 査読 国際誌

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

    The Journal of organic chemistry83 ( 7 ) 3921 - 3927   2018年4月

     詳細を見る

    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

    Scopus

    PubMed

    researchmap

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

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

    TETRAHEDRON72 ( 48 ) 7805 - 7812   2016年12月

     詳細を見る

    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

    Web of Science

    researchmap

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

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

    The Journal of organic chemistry81 ( 7 ) 2692 - 703   2016年4月

     詳細を見る

    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 cyclopropyl 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

    Web of Science

    PubMed

    researchmap

  • 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

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

    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

     詳細を見る

    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

    Web of Science

    researchmap

  • Metal-free, one-pot, sequential protocol for transforming α,β-epoxy ketones to β-hydroxy ketones and α-methylene ketones. 査読 国際誌

    Eietsu Hasegawa, Saki Arai, Eiji Tayama, Hajime Iwamoto

    The Journal of organic chemistry80 ( 3 ) 1593 - 600   2015年2月

     詳細を見る

    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 β-hydroxy ketones and α-methylene ketones has been developed. Reaction of epoxy ketones with boron trifluoride etherate (BF3·OEt2) 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 β-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 α-methylene ketone products can be carried out in one pot.

    DOI: 10.1021/jo5025249

    Web of Science

    PubMed

    researchmap

  • 2-Aryl-1,3-dimethylbenzimidazolines as Effective Electron and Hydrogen Donors in Photoinduced Electron-Transfer Reactions

    Eietsu Hasegawa, Shin-ya Takizawa

    AUSTRALIAN JOURNAL OF CHEMISTRY68 ( 11 ) 1640 - 1647   2015年

     詳細を見る

    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  

    2-Aryl-1,3-dimethylbenzimidazolines (DMBIHs) have been applied to photoinduced electron-transfer reductions of various organic substrates. Either direct or indirect electron transfer between the substrates and DMBIHs is utilized to promote the desired transformations. Photoexcitation of the substrates using light above 280 nm was carried out in the former protocol whereas a photosensitization method using materials such as substituted pyrenes, ruthenium and iridium complexes that absorb longer-wavelength light was employed in the latter. In these reactions, DMBIHs undergo initial electron transfer and subsequent proton or hydrogen atom transfer.

    DOI: 10.1071/CH15314

    Web of Science

    researchmap

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

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

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

     詳細を見る

    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

    Web of Science

    researchmap

  • A photo-reagent system of benzimidazoline and Ru(bpy)<inf>3</inf>Cl<inf>2</inf>to promote hexenyl radical cyclization and Dowd-Beckwith ring-expansion of α-halomethyl-substituted benzocyclic 1-alkanones

    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

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A combination of 2-aryl substituted 1,3-dimethyl-benzimidazolines (DMBIHs) and tris(2,2′-bipyridine)ruthenium(II) chloride, Ru(bpy)3Cl2was used to promote photoinduced electron-transfer (PET) reactions of α-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. © 2014 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2014.02.078

    Web of Science

    researchmap

  • Copper(II)–acid catalyzed cyclopropanation of 1,3-dienamides by electrophilic activation of α-aryl diazoesters 査読

    Eiji Tayama, Kouki Horikawa, Hajime Iwamoto, Eietsu Hasegawa

    Tetrahedron Letters55 ( 19 ) 3041 - 3044   2014年

     詳細を見る

    出版者・発行元:Elsevier {BV}  

    DOI: 10.1016/j.tetlet.2014.03.115

    researchmap

  • 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

     詳細を見る

    出版者・発行元:Royal Society of Chemistry ({RSC})  

    DOI: 10.1039/c4cc02536a

    researchmap

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

    Tomohito Igarashi, Eiji Tayama, Hajime Iwamoto, Eietsu Hasegawa

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

     詳細を見る

    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

    Web of Science

    researchmap

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

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

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

     詳細を見る

    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

    Web of Science

    researchmap

  • Photoinduced electron-transfer reaction of α-bromomethyl-substituted benzocyclic β-keto esters with amines: Selective reaction pathways depending on the nature of the amine radical cations

    Eietsu Hasegawa, Emi Tosaka, Akira Yoneoka, Yukinobu Tamura, Shin Ya Takizawa, Masaaki Tomura, Yoshiro Yamashita

    Research on Chemical Intermediates39 ( 1 ) 247 - 267   2013年1月

     詳細を見る

    記述言語:英語  

    Photoinduced electron-transfer reaction of α-bromomethyl-substituted benzocyclic β-keto esters with tertiary amines was investigated. Debrominated β-keto esters and ring-expanded γ-keto esters were obtained as major products. On the basis of mechanistic experiments it was concluded that these products are formed via a reaction sequence of selective carbon-bromine bond cleavage and subsequent competitive hydrogen abstraction and Dowd-Beckwith ring-expansion of the resulting primary alkyl radicals. The characteristic product distribution observed for the type of amine used is rationalized on the basis of selective reaction pathways of generated radical intermediates that depend on the nature of the amine radical cations. © 2012 Springer Science+Business Media B.V.

    DOI: 10.1007/s11164-012-0646-2

    Web of Science

    researchmap

  • A Unique and Simple Preparative Method for α-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

     詳細を見る

    出版者・発行元:Japan Institute of Heterocyclic Chemistry  

    DOI: 10.3987/COM-12-12619

    DOI: 10.3987/com-12-12619

    researchmap

  • 1,4-Elimination/Brønsted acid catalyzed aza-Ferrier reaction sequence as an entry to β-amino-β,γ-unsaturated aldehydes 査読

    Eiji Tayama, Kouki Horikawa, Hajime Iwamoto, Eietsu Hasegawa

    Tetrahedron69 ( 13 ) 2745 - 2752   2013年

     詳細を見る

    出版者・発行元:Elsevier {BV}  

    DOI: 10.1016/j.tet.2013.01.088

    researchmap

  • 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

    The Journal of Organic Chemistry78 ( 11 ) 5205 - 5217   2013年

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

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

    HETEROCYCLES86 ( 2 ) 1211 - 1226   2012年12月

     詳細を見る

    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

    Web of Science

    researchmap

  • 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

     詳細を見る

    出版者・発行元:Elsevier {BV}  

    DOI: 10.1016/j.tetlet.2012.07.070

    researchmap

  • Asymmetric α-2-tosylethenylation of N,N-dialkyl-L-amino acid estersvia 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

     詳細を見る

    出版者・発行元:Royal Society of Chemistry ({RSC})  

    DOI: 10.1039/c1ob06074k

    researchmap

  • 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 - 5718   2012年

     詳細を見る

    出版者・発行元:Elsevier {BV}  

    DOI: 10.1016/j.tet.2012.04.015

    researchmap

  • 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

     詳細を見る

    出版者・発行元:Elsevier {BV}  

    DOI: 10.1016/j.tetlet.2012.01.013

    researchmap

  • Asymmetric α-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

     詳細を見る

    出版者・発行元:Elsevier {BV}  

    DOI: 10.1016/j.tetlet.2011.02.040

    researchmap

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

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

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

     詳細を見る

    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.

    DOI: 10.1016/j.tetlet.2010.10.018

    Web of Science

    researchmap

  • Novel biphasic reaction system of ferric chloride dissolved imidazolium hexafluorophosphate and benzotrifluoride: application to electron transfer reaction of cyclopropyl silyl ethers

    Hiroyuki Tsuchida, Eietsu Hasegawa

    TETRAHEDRON66 ( 19 ) 3447 - 3451   2010年5月

     詳細を見る

    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  

    Ferric chloride (FeCl3) promoted electron transfer oxidation of bicyclic cyclopropyl silyl ethers was performed in biphasic solution system of 1-butyl-3-methylimidazolium hexafluorophosphate (BmimPF(6)) and benzotrifluoride (BTF). The resulting chloro-substituted ring-expanded cycloalkanones were treated with an appropriate base to produce substituted cyclic enones. These two-step reactions were successfully devised to proceed in a simpler manner in which the ordinary work-up operations for the former oxidation step, such as water-quench, extraction, and evaporation, were omitted; imidazole was found to be the most suitable base for the latter elimination step. (C) 2010 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2010.03.029

    Web of Science

    researchmap

  • 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 Chemistry2010 ( 35 ) 6719 - 6721   2010年

     詳細を見る

    出版者・発行元:Wiley  

    DOI: 10.1002/ejoc.201001083

    researchmap

  • 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

     詳細を見る

    出版者・発行元:Elsevier {BV}  

    DOI: 10.1016/j.tet.2010.09.105

    researchmap

  • In situ generated tris(p-bromophenyl)amine radical cation promoted electron transfer reaction of cyclopropyl silyl ethers

    Eietsu Hasegawa, Koji Kakinuma, Tomoyo Yanaki, Shota Komata

    TETRAHEDRON65 ( 52 ) 10876 - 10881   2009年12月

     詳細を見る

    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  

    Tris(p-bromophenyl)aminium hexachloroantimonate and perchlorate were utilized to promote the oxidative ring-opening reaction of cyclopropyl silyl ethers giving ring-expanded ketones. Exploration of salt quantity effect on the reaction allowed us to hypothesize that amine radical cation is regenerated through the oxidation of neutral amine by hexachloroantimonate anion. Based on this hypothesis, amine radical cation was initially generated by the treatment of parent amine with either antimony pentachloride or the mixture of silver perchlorate and molecular iodine, and subsequently reacted with same substrates. The in situ generated amine radical cation was found to promote the reaction, and the expected products were obtained in better yields than via use of the corresponding salt reagents. (C) 2009 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2009.09.108

    Web of Science

    researchmap

  • Cyclization and Ring-Expansion Processes Involving Samarium Diiodide Promoted Reductive Formation and Subsequent Oxidative Ring Opening of Cyclopropanol Derivatives

    Hiroyuki Tsuchida, Mutsuko Tamura, Eietsu Hasegawa

    JOURNAL OF ORGANIC CHEMISTRY74 ( 6 ) 2467 - 2475   2009年3月

     詳細を見る

    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  

    Samarium diiodide promoted reaction of various alpha-bromomethyl cycloalkanones, followed by subsequent treatment with trimethylsilyl chloride, leads to the production of cyclopropyl silyl ethers embedded in bicyclo[m.1.0]alkane frameworks. Treatment of the ethers with oxidative electron-transfer reagents, such as Fe(III), Ce(IV), and Mn(III) salts, generates ring-expanded ketones that convert to cyclic conjugated enones in moderate to good yields. In addition, the reduction-oxidation reaction sequences can be successfully performed in one pot. The regioselectivities of cyclopropane ring opening in the bicyclic Substrates depend on the oxidizing agents used. For example, reactions promoted by FeCl3 with pyridine lead to the expected ring-expansion process involving internal-bond cleavage of bicycloalkane and yielding cyclic enones as final products. In contrast, reactions with Ce(NH4)(2)(NO3)(6) or Mn(OAc)(3) as oxidizing agents proceed by way of external-bond cleavage to give alpha-iodomethyl cycloalkanones.

    DOI: 10.1021/jo802749g

    Web of Science

    researchmap

  • BENZIMIDAZOLINE-DIMETHOXYPYRENE. AN EFFECTIVE PROMOTER SYSTEM FOR PHOTOINDUCED ELECTRON TRANSFER PROMOTED REDUCTIVE TRANSFORMATIONS OF ORGANIC COMPOUNDS

    Eietsu Hasegawa, Harumi Hirose, Kosuke Sasaki, Shinya Takizawa, Takayuki Seida, Naoki Chiba

    HETEROCYCLES77 ( 2 ) 1147 - 1161   2009年2月

     詳細を見る

    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  

    2-(p-Methoxyphenyl)-1,3-dimethylbenzimidazoline (ADMBI) and 2-(o-hydroxyphenyl)-1,3-dimethylbenzimidazoline (HPDMBI) are used as reducing reagents in 1,8-dimethoxypyrene (1,8-DMP) sensitized, photoinduced electron transfer (PET) reactions. This system was effectively used for PET induced, reductive transformations of various organic substrates, including alpha,beta-epoxy ketones, the olefin tethered 2-bromomethyl-1-tetraone, and o-allyloxy-iodobenzene, as well as for the deprotection reactions of dodecyl-2-benzoylbenzoate and N-sulfonylindole. The results of studies show that 1,8-DMP is a more effective sensitizer than the previously used 9-methylcarbazole for deprotection of N-methyl-4-picolinium ester.

    DOI: 10.3987/COM-08-S(F)94

    Web of Science

    researchmap

  • Tris(trimethylsilyl)silane promoted radical reaction and electron-transfer reaction in benzotrifluoride

    Eietsu Hasegawa, Yuki Ogawa, Koji Kakinuma, Hiroyuki Tsuchida, Emi Tosaka, Shinya Takizawa, Hiroyasu Muraoka, Tomoko Saikawa

    TETRAHEDRON64 ( 33 ) 7724 - 7728   2008年8月

     詳細を見る

    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  

    Tris(trimethylsilyl)silane (TTMSS) promoted free radical reaction in benzotrifluoride (BTF) was investigated. Compared to same reaction using environmentally less desirable tri-n-butyltin hydride (TBTH) in benzene, less quantity of BTF than that of benzene can be used because of slower hydrogen atom transfer from TTMSS than that from TBTH toward primary alkyl radicals. Also, electron-transfer reactions promoted by tris(p-bromophenyl)aminium hexachloroantimonate (TBPA) and FeCl(3) were conducted in BTF. Then, TBPA was found to be effective in BTF comparably to that in methylene chloride. In addition, an interesting observation that FeCl(3) promoted reaction was accelerated by the addition of imidazolium salt was made. All the results suggest that BTF is a tolerable solvent for free radical reaction with TTMSS and electron-transfer reactions using TBPA as well as FeCl(3). (C) 2008 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2008.06.012

    Web of Science

    researchmap

  • Electron transfer promoted regioselective ring-opening reaction of cyclopropyl silyl ethers

    Eietsu Hasegawa, Naoto Yamaguchi, Hiroyasu Muraoka, Hiroyuki Tsuchida

    ORGANIC LETTERS9 ( 15 ) 2811 - 2814   2007年7月

     詳細を見る

    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 cyclopropyl silyl ethers incorporated into bicyclo[m.1.0]alkane framework were investigated. The results show that the regioselectivities for ring-opening of intermediate radical cations, formed by single electron transfer, are governed by the nature of the nucleophile as well as oxidizing species.

    DOI: 10.1021/ol0709937

    Web of Science

    PubMed

    researchmap

  • The first example of samarium diiodide-promoted intramolecular ketone-ester coupling of ketones tethering acyloxyalkyl side chains producing 2-hydroxy cyclic hemiacetals

    Eietsu Hasegawa, Kentaro Okamoto, Naoko Tanikawa, Momoe Nakamura, Kazuki Iwaya, Takashi Hoshi, Toshio Suzuki

    TETRAHEDRON LETTERS47 ( 44 ) 7715 - 7718   2006年10月

     詳細を見る

    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 reaction of samarium diiodide with some cyclic and acyclic ketones tethering acyloxyalkyl side chains produced 2-hydroxy cyclic hemiacetals in moderate to good yields, in which an intramolecular addition of samarium ketyl radicals to distant ester carbonyls would be involved. (c) 2006 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tetlet.2006.08.126

    Web of Science

    researchmap

  • Photoinduced electron-transfer systems consisting of electron-donating pyrenes or anthracenes and benzimidazolines for reductive transformation of carbonyl compounds

    E Hasegawa, S Takizawa, T Seida, A Yamaguchi, N Yamaguchi, N Chiba, T Takahashi, H Ikeda, K Akiyama

    TETRAHEDRON62 ( 27 ) 6581 - 6588   2006年7月

     詳細を見る

    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 reactions of several ketone substrates were studied to evaluate the utilities of 1,6-bis(dimethyl-amino)pyrene (BDMAP), 1,6-dimethoxypyrene (DMP), 9,10-bis(dimethlylamino)anthracene (BDMAA), and 9,10-dimethoxyanthracene (DMA) as electron-donating sensitizers cooperating with 2-aryl-13-dimethylbenzimidazolines. BDMAP and DMP generally led higher conversion of ketones and better yield of reduction products compared to BDMAA and DMA. (c) 2006 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tet.2006.03.061

    Web of Science

    researchmap

  • Cyclization and ring-expansion reactions involving reductive formation and oxidative ring-opening of cyclopropanol derivatives

    E Hasegawa, H Tsuchida, M Tamura

    CHEMISTRY LETTERS34 ( 12 ) 1688 - 1689   2005年12月

     詳細を見る

    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  

    FeCl3-promoted regioselective ring-opening reactions of cyc lopropyl trimethylsilyl ethers, obtained by SMI2 reduction c followed by silylation with Me3SiCl of bromoalkyl ketones and acyl chloride, were performed. Eventually, the sequential reduction and oxidation reactions starting from bromoalkyl ketones to give ring-expanded enones were achieved in one-pot.

    DOI: 10.1246/cl.2005.1688

    Web of Science

    researchmap

  • Contrastive photoreduction pathways of benzophenones governed by regiospecific deprotonation of imidazoline radical cations and additive effects

    E Hasegawa, T Seida, N Chiba, T Takahashi, H Ikeda

    JOURNAL OF ORGANIC CHEMISTRY70 ( 23 ) 9632 - 9635   2005年11月

     詳細を見る

    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  

    [GRAPHICS]
    In the photoreaction of benzophenones with 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI), benzhydrols were major products. Addition of H2O accelerated the reaction with no change in the product distribution, while AcOH, PhOH, and metal salts such as LiClO4 and Mg(ClOL4)(2) were effective additives to produce benzpinacols. In contrast, benzpinacols were exclusively formed regardless of the solvent and the additive in the reactions with 2-(o-hydroxyphenyl)-1,3-dimethylbenzimidazoline (o-HPDMBI). These observations are consistent with the hypothesis that DMPBIcenter dot+ donates a proton at the C-2 position to the benzophenone ketyl radicals while o-HPDMBIcenter dot+ donates a phenol proton.

    DOI: 10.1021/jo0514220

    Web of Science

    researchmap

  • 2-Hydroxyphenyl-1,3-dimethylbenzimidazolines. Formal two hydrogen atom-donors for photoinduced electron transfer reactions

    E Hasegawa, N Chiba, T Takahashi, S Takizawa, T Kitayama, T Suzuki

    CHEMISTRY LETTERS33 ( 1 ) 18 - 19   2004年1月

     詳細を見る

    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  

    Both 2-(2-hydroxyphenyl)-1,3-dimethylbenzimidazoline and 2-(4-hydroxyphenyl)-1,3-dimethylbenzimidazoline were found to act as formal two hydrogen atom-donors for photoinduced electron transfer reactions of epoxy ketones and other carbonyl compounds.

    DOI: 10.1246/cl.2004.18

    Web of Science

    researchmap

  • Novel transformation of 2-substituted alkyl 1-indanone-2-acetates to 6-substituted 3,4-benzotropolones through sequential reduction and oxidation processes using Sm(II) and Ce(IV) salts

    K Iwaya, M Tamura, M Nakamura, E Hasegawa

    TETRAHEDRON LETTERS44 ( 52 ) 9317 - 9320   2003年12月

     詳細を見る

    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  

    When 2-substituted alkyl 1-indanone-2-acetates 1 were treated with samarium diiodide, 3-substituted 2-hydroxy-2,3-methano-1-oxo-1,2,3,4-tetrahydronaphthalenes 4 were obtained. The reaction is proposed to proceed through a rearrangement initiated by intramolecular ketone-ester coupling. Oxidation of these products 4 or their silyl ethers 13 by ceric(IV) ammonium nitrate involving regioselective bond cleavage of their bicyclo[4.1.0]-rings produced the corresponding benzotropolone derivatives 10. (C) 2003 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.tetlet.2003.10.083

    Web of Science

    researchmap

  • Samarium diiodide-promoted intramolecular ketone-ester coupling reaction: novel cyclization and ring expansion pathway

    K Iwaya, M Nakamura, E Hasegawa

    TETRAHEDRON LETTERS43 ( 29 ) 5067 - 5070   2002年7月

     詳細を見る

    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  

    When ethyl 2-substituted-1-indanolle-2-carboxylates were treated with samarium diiodide (Sml(2)), ring expansion products such as 3-substituted-1,2-naphthoquillones were isolated. Alcohols were also obtained as the mixture of cis- and trans-isomers of hydroxy and ester substituents. A reaction mechanism involving intranlolecular addition of samarium ketyl radicals to ester substituents followed by ring expansion was proposed for the formation of the one-carbon homologated products. Similarly, reaction of ethyl 1-substituted-2-oxo-1-cyclopentanecarboxylates with Sml(2) produced 3-substituted-2-hydroxy-2-cyclohexenones along with the corresponding alcohols. (C) 2002 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0040-4039(02)01007-9

    Web of Science

    researchmap

  • Changeable reactivity of ketyl radicals derived from 2-bromomethyl-2-(3-butenyl)benzocyclic-1-alkanones depending on electron transfer conditions employed

    E Hasegawa, S Takizawa, K Iwaya, M Kurokawa, N Chiba, K Yamamichi

    CHEMICAL COMMUNICATIONS17 ( 17 ) 1966 - 1967   2002年

     詳細を見る

    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  

    Photoinduced electron transfer reaction of 2-bromomethyl-2-( 3-butenyl)benzocyclic-1-alkanones with amines afforded 5-exo radical cyclization products while electron transfer reaction with samarium diiodide produced cyclopropanols.

    DOI: 10.1039/b205781f

    Web of Science

    PubMed

    researchmap

  • 1,3-Dimethyl-2-phenylbenzimidazoline (DMPBI)-acetic acid: An effective reagent system for photoinduced reductive transformation of α,β-epoxy ketones to β-hydroxy ketones

    E. Hasegawa, N. Chiba, A. Nakajima, K. Suzuki, A. Yoneoka, K. Iwaya

    Synthesis ( 8 ) 1248 - 1252   2001年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    A combination of 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI) and acetic acid has been utilized for photoinduced reductive transformation of α,β-epoxy ketones to β-hydroxy ketones. Study on photoreactions using several proton donors revealed that acetic acid is superior to other proton donors such as HCl, p-TsOH, MeOH, and water. 1,3-Dimethyl-2-phenylbenzimidazolium was produced in the reaction with acetic acid while N-benzoyl-N,N′-dimethyl-o-phenylenediamine was formed in aqueous solvents. When THF solutions containing aryl carbonyl possessing α,β-epoxy ketones and DMPBI and acetic acid were irradiated (λ &gt; 280 nm), β-hydroxy ketones were isolated in good to excellent yields. Photosensitized conditions (λ &gt; 340 nm) were employed for the reactions of alkyl carbonyl possessing α,β-epoxy ketones.

    DOI: 10.1055/s-2001-15055

    Web of Science

    researchmap

  • Reaction of ethyl 2-haloethyl-1-tetralone-2-carboxylate and samarium diiodide: first example of intramolecular O-alkylation of samarium ketyl radical by carbon-halogen bond

    E Hasegawa, K Iwaya, T Iriyama, T Kitazume, M Tomura, Y Yamashita

    TETRAHEDRON LETTERS41 ( 33 ) 6447 - 6450   2000年8月

     詳細を見る

    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  

    Reaction of ethyl 2-haloethyl-1-tetralone-2-carboxylates and SmI2 produced novel dimers possessing cyclic ether structures through intramolecular O-alkylation of samarium ketyl radicals by carbon-halogen bonds. (C) 2000 Elsevier Science Ltd. All rights reserved.

    DOI: 10.1016/S0040-4039(00)01020-0

    Web of Science

    researchmap

  • Photoreactions of 4-(tribromomethyl)-4-methyl-2,5-cyclohexadienone and its derivatives with amines: Radical cyclization and ring expansion reactions promoted through photoinduced electron transfer processes

    E Hasegawa, Y Tamura, K Suzuki, A Yoneoka, T Suzuki

    JOURNAL OF ORGANIC CHEMISTRY64 ( 24 ) 8780 - 8785   1999年11月

     詳細を見る

    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  

    Photoreactions of 4-(tribromomethyl)-4-methyl-2,5-cyclohexadienone (1) and its derivatives with amines were studied. Irradiation of 1 with amine produced 4-bromo-5-methyltropone (2) along with 4-(dibromomethyl)-4-methyl-2,5-cyclohexadienone (3). The effects of solvent, added water, and the structural variation in amine on the product ratio were explored. Isolation of the amine-derived products revealed that oxidative dealkylation of amine proceeded during the photoreaction. On the basis of the results obtained, a reaction mechanism involving fragmentation of the dienone anion-radical and amine cation-radical pair is proposed. Photoreactions of dienone 4 with amine produced the tropones 6 and 7, whereas tropone 9 was produced from 8. Trialkyltin radical-induced reductions of dienones land 4 with tri-n-butyltin hydride demonstrated common features with the photoreactions. It was also found that irradiation of dienone 3 with amine produced 4-methyltropone (10).

    DOI: 10.1021/jo990215v

    Web of Science

    researchmap

  • Reductive transformation of α β-epoxy ketones and other compounds promoted through photoinduced electron transfer processes with 1,3-dimethyl- 2-phenylbenzimidazoline (DMPBI)

    Eietsu Hasegawa, Akira Yoneoka, Kumiko Suzuki, Teru Kato, Takashi Kitazume, Kazuhiro Yanagi

    Tetrahedron55 ( 45 ) 12957 - 12968   1999年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Photoreactions of epoxy ketones, aromatic ketones, haloketones, and aromatic halides with 1,3-dimethyl-2-phenylbenzimidazoline (DMPBI) were studied. Photoinduced single-electron transfer from DMPBI to such substrates initiates the reactions, followed by radical rearrangement and reduction to finally give several reduced products in modest to good yields.

    DOI: 10.1016/S0040-4020(99)00804-2

    Web of Science

    researchmap

  • First example of samarium diiodide-promoted sequential cyclization and ring-expansion reactions of α-bromomethyl cyclic β-keto esters to homologated γ-keto esters

    Eietsu Hasegawa, Takashi Kitazume, Kimiko Suzuki, Emi Tosaka

    Tetrahedron Letters39 ( 23 ) 4059 - 4062   1998年6月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    SmI2reductions of some aromatic as well as aliphatic α-bromomethyl cyclic β-keto esters produced one-carbon homologated γ-keto esters in modest to good yields.

    DOI: 10.1016/S0040-4039(98)00658-3

    Web of Science

    researchmap

  • Photoreaction of halomethyl substituted benzocyclic ketones with amines: Radical cyclization and ring expansion reactions promoted through photoinduced electron transfer processes

    Eietsu Hasegawa, Yukinobu Tamura, Emi Tosaka

    Chemical Communications ( 19 ) 1895 - 1896   1997年

     詳細を見る

    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 Society of Chemistry  

    Photoreaction of ethyl 2-bromomethyl-1-oxo-1,2,3,4-tetrahydronaphthalene-2-carboxylate 1a or other related compounds 1b-d with Me3SiCH2NEt2 in aqueous MeCN afforded ethyl 5-oxo-6,7,8,9-tetrahydrobenzocycloheptene-7-carboxylate 2a or corresponding ring expansion products 2a-d respectively.

    DOI: 10.1039/a703974c

    Scopus

    researchmap

  • Electron-Transfer Reactions of Aromatic α,βEpoxy Ketones: Factors That Govern Selective Conversion to β-Diketones and β-Hydroxy Ketones

    Eietsu Hasegawa, Kenyuki Ishiyama, Takayuki Fujita, Tomoyasu Kato, Toshiaki Abe

    Journal of Organic Chemistry62 ( 8 ) 2396 - 2400   1997年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Photoreaction of trans-1-(4-cyanophenyl)-3-phenyl-2,3-epoxy-1-propanone (trans-4′-cyanochalcone epoxide) with various electron donors was studied. Irradiation of this epoxy ketone with amines produced 1-(4-cyanophenyl)-3-phenyl-1,3-propanedione and 1-(4-cyanophenyl)-3-hydroxy-3-phenyl-1-propanone in various ratios depending on the kinds of amine and solvent used. A reaction mechanism involving an amine cation radical-assisted rearrangement of the epoxy ketone anion radical was proposed to be most consistent with the marked change in the yield of β-diketone. On the other hand, the timing of proton transfer to the anionic intermediates is considered to be a key factor to yield the β-hydroxy ketone. Information obtained from the photochemical study was useful to find the reaction conditions for the conversion of several aromatic epoxy ketones to hydroxy ketones by the use of samarium diiodide. Addition of methanol significantly changed the product distribution. Proper choice of water or methanol as a proton source produced hydroxy ketones in moderate to good yields.

    DOI: 10.1021/jo9622439

    Scopus

    researchmap

  • Pyrylium salt promoted substitution reactions of acetals with various silylated nucleophiles

    M Kamata, S Nagai, M Kato, E Hasegawa

    TETRAHEDRON LETTERS37 ( 43 ) 7779 - 7782   1996年10月

     詳細を見る

    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  

    Catalytic amounts of triarylpyrylium sales photochemically and thermally promoted the substitution reactions of dimethyl acetals with silylated nucleophiles. Copyright (C) 1996 Elsevier Science Ltd.

    DOI: 10.1016/0040-4039(96)01776-5

    Web of Science

    researchmap

  • Photoinduced electron transfer reactions of α,β-epoxy ketones with 2-phenyl-N,N-dimethylbenzimidazoline (PDMBI): Significant water effect on the reaction pathway

    Eietsu Hasegawa, Teru Kato, Takashi Kitazume, Kazuhiro Yanagi, Kazuya Hasegawa, Takaaki Horaguchi

    Tetrahedron Letters37 ( 39 ) 7079 - 7082   1996年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Irradiation of aroyl substituted epoxy ketones with 2-phenyl-N,N-dimethylbenzimidazoline in aqueous tetrahydrofuran or aqueous benzene produced the corresponding aldols in good to excellent yields. Changing the amount of water added significantly influenced the product distribution.

    DOI: 10.1016/0040-4039(96)01578-X

    Web of Science

    researchmap

  • Aminium salt promoted catalytic substitution reactions of acetals with silylated nucleophiles

    M Kamata, Y Yokoyama, N Karasawa, M Kato, E Hasegawa

    TETRAHEDRON LETTERS37 ( 20 ) 3483 - 3486   1996年5月

     詳細を見る

    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 catalytic amount of tris(p-bromophenyl)aminium hexachloroantimonate promoted the substitution reactions of dimethylacetals with various silylated nucleophiles through an election transfer mechanism. Silyl compounds include silyl enol ether, ketene silyl acetal, and allylsilane. One methoxy group of the substrates was effectively substituted by nucleophiles to form carbon-carbon bonds. Copyright (C) 1996 Elsevier Science Ltd

    DOI: 10.1016/0040-4039(96)00596-5

    Web of Science

    researchmap

  • ELECTRON-TRANSFER-INDUCED STEREOSELECTIVE CYCLIZATION OF 2,2-DISUBSTITUTED DIBENZOYLMETHANE TO ANTI-1,2-CYCLOPROPANEDIOL

    E HASEGAWA, H KATAGI, D NAKAGAWA, T HORAGUCHI

    TETRAHEDRON LETTERS36 ( 38 ) 6915 - 6918   1995年9月

     詳細を見る

    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  

    Irradiation of 2,2-dimethyl-13-diphenyl-13-propanedione in the presence of triethylamine gave anti-2,2-dimethyl-13-diphenyl-13-cyclopropanediol as a major product. On the basis of the results obtained, the mechanism involving single electron transfer between the excited diketone and the ground state amine followed by the anion radical rearrangement was proposed. The same cyclized product was also obtained for the reaction with samarium diiodide.

    DOI: 10.1016/00404-0399(50)1429L-

    Web of Science

    researchmap

  • ELECTRON-TRANSFER-INDUCED STEREOSELECTIVE CYCLIZATION OF 2,2-DISUBSTITUTED DIBENZOYLMETHANE TO ANTI-1,2-CYCLOPROPANEDIOL

    E HASEGAWA, H KATAGI, D NAKAGAWA, T HORAGUCHI

    TETRAHEDRON LETTERS36 ( 38 ) 6915 - 6918   1995年9月

     詳細を見る

    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  

    Irradiation of 2,2-dimethyl-13-diphenyl-13-propanedione in the presence of triethylamine gave anti-2,2-dimethyl-13-diphenyl-13-cyclopropanediol as a major product. On the basis of the results obtained, the mechanism involving single electron transfer between the excited diketone and the ground state amine followed by the anion radical rearrangement was proposed. The same cyclized product was also obtained for the reaction with samarium diiodide.

    DOI: 10.1016/00404-0399(50)1429L-

    Web of Science

    researchmap

  • Reactions of 1-bromo-2,3-epoxypropane with samarium diiodide: First observation of carbon-carbon bond cleavage of oxiranylmethyl radical under the single electron transfer conditions

    Eietsu Hasegawa, Masanori Takahashi, Takaaki Horaguchi

    Tetrahedron Letters36   5215 - 5218   1995年8月

     詳細を見る

    Reaction of 1-bromo-1-phenyl-3-(1-naphthyl)-23-epoxypropane 1 with samarium diiodide afforded 1-phenyl-2-(1-naphthylmethoxy)ethene 3 as well as 1-(1-naphthyl)-3-phenylprop-2-enol 2. The product distributions were influenced by various factors, such as additives, concentrations, and reaction temperature.

    DOI: 10.1016/0040-4039(95)00975-I

    researchmap

  • REACTIONS OF 1-BROMO-2,3-EPOXYPROPANE WITH SAMARIUM DIIODIDE - FIRST OBSERVATION OF CARBON-CARBON BOND-CLEAVAGE OF OXIRANYLMETHYL RADICAL UNDER THE SINGLE-ELECTRON TRANSFER CONDITIONS

    E HASEGAWA, M TAKAHASHI, T HORAGUCHI

    TETRAHEDRON LETTERS36 ( 29 ) 5215 - 5218   1995年7月

     詳細を見る

    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  

    Reaction of 1-bromo-1-phenyl-3-(1-naphthyl)-2,3-epoxypropane 1 with samarium diiodide afforded 1-phenyl 2-(1-naphlhylmethoxy)ethene 3 well as 1-(1-naphthyl)-3-phenylprop-2-enol 2. The product distributions were influenced by various factors, such as additives, concentrations, and reaction temperature.

    DOI: 10.1016/00404-0399(50)0975I-

    Web of Science

    researchmap

  • NOVEL PHOTOREACTION OF 4-TRIBROMOMETHYL-4-METHYL-2,5-CYCLOHEXADIENONE WITH AMINE

    E HASEGAWA, Y TAMURA, T HORAGUCHI, K ISOGAI, T SUZUKI

    TETRAHEDRON LETTERS35 ( 46 ) 8643 - 8646   1994年11月

     詳細を見る

    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  

    Irradiation of 4-tribromomethyl-4-methyl-2,5-cyclohexadienone in the presence of amines gave 4-bromo-5-methyltropone as a major product. On the basis of the results obtained, the mechanism involving single electron transfer from the amine ground state to the dienone excited state was proposed.

    DOI: 10.1016/S0040-4039(00)78459-0

    Web of Science

    researchmap

  • Pyrylium salt sensitized photochemical deprotections of dithioacetals and ketals

    Masaki Kamata, Yukiko Murakami, Yasuko Tamagawa, Mitsuaki Kato, Eietsu Hasegawa

    Tetrahedron50 ( 45 ) 12821 - 12828   1994年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Photoreactions of various dithioacetals and ketals using tris(p-chlorophenyl)pyrylium perchlorate as a sensitizer were studied. Irradiation (λ&amp
    &gt
    360 nm) of dichloromethane solutions containing dithioacetals or ketals and pyrylium salt afforded the corresponding carbonyl compounds in good to excellent yields in the presence of molecular oxygen. © 1994.

    DOI: 10.1016/S0040-4020(01)81203-5

    Scopus

    researchmap

  • RATE CONSTANTS FOR THE REACTIONS OF PRIMARY ALKYL RADICALS WITH SMI2 IN THF/HMPA

    E HASEGAWA, DP CURRAN

    TETRAHEDRON LETTERS34 ( 11 ) 1717 - 1720   1993年3月

     詳細を見る

    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 first bimolecular rate constants for the reduction of a primary alkyl radical by SmI2 were obtained by using a competitive hexenyl radical clock. Rate constants varied from 5 x 10(5) to 7 x 10(6) M-1 s-1, depending on the amount of HMPA present.

    DOI: 10.1016/S0040-4039(00)60760-8

    Web of Science

    researchmap

  • Additive and Solvent Effects on SmI<inf>2</inf> Reductions: The Effects of Water and DMPU

    Eietsu Hasegawa, Dennis P. Curran

    Journal of Organic Chemistry58   5008 - 5010   1993年1月

     詳細を見る

  • The Rearrangement of α-(Phenoxy)pheny!acetic Acids and Benzyl phenyl Ethers with Polyphosphoric Acid

    Kaoru Hanaya, Takashi Muramatsu, Osamu Izawa, Akira Yokouchi, Eietsu Hasegawa

    Nippon Kagaku Kaishi1993 ( 4 ) 363 - 369   1993年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    It was confirmed that the cyclization product of α-(phenoxy)phenylacetic acid (1 a) with polyphosphoric acid is 3-phenyl-2(3 H)-benzofuranone (3 a) instead of 2-phenyl-3(2 H)-benzofuranone (2 a). Some mechanistic studies including crossover experiments by use of la and α-(p~methylphenoxy)-p-tolylacetic acid (1 d) demonstrated that the rearrangement occurs intramolecularly. The rearrangement of benzyl phenyl ethers with polyphosphoric acid was also investigated. © 1993, The Chemical Society of Japan. All rights reserved.

    DOI: 10.1246/nikkashi.1993.363

    Scopus

    researchmap

  • PHOTOINDUCED ELECTRON-TRANSFER REACTIONS OF 1-SUBSTITUTED 2,3-DIPHENYLAZIRIDINES WITH 9,10-DICYANOANTHRACENE AND CHLORANIL

    E HASEGAWA, S KOSHII, T HORAGUCHI, T SHIMIZU

    JOURNAL OF ORGANIC CHEMISTRY57 ( 23 ) 6342 - 6344   1992年11月

     詳細を見る

    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/jo00049a054

    Web of Science

    researchmap

  • Photochemically and Thermally Induced Free-Radical Reactions of α,β-Epoxy Ketones with Tributyltin Hydride: Selective C<inf>α</inf>-O Bond Cleavage of Oxiranylmethyl Radicals Derived from α,β-Epoxy Ketones

    Eietsu Hasegawa, Kenyuki Ishiyama, Tomoyasu Hato, Takaaki Horaguchi, Takahachi Shimizu, Shoji Tanaka, Yoshiro Yamashita

    Journal of Organic Chemistry57 ( 20 ) 5352 - 5359   1992年9月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Free-radical reactions of α,β-epoxy ketones with tributyltin hydride have been studied. These substances were selectively converted to β-hydroxy ketones under both photochemical and thermal conditions. The photoreaction is initiated by hydrogen abstraction of an epoxy ketone triplet from tributyltin hydride, while azoisobutyronitrile is used as an initiator for the thermal reaction. In general, the photoreaction conditions are particularly useful for aroyl-substituted epoxy ketones while the thermal conditions are applicable to a variety of epoxy ketones. It was also found that the epoxy esters and epoxy alcohols did not undergo the ring-opening reaction under the similar conditions. Tributyltin radical attack on the carbonyl of epoxy ketones is a key process for both the photoreaction and the thermal reaction. Regioselective ring opening of the resulting oxiranylmethyl radical finally produces β-hydroxy ketones. In order to capture the free-radical intermediates, the reaction of epoxy ketones with allyltributyltin was conducted. The isolation of α-allylated β-hydroxy ketones is interpreted by the involvement of a novel 1,5-tributyltin transfer. © 1992, American Chemical Soc

    DOI: 10.1021/jo00046a016

    Web of Science

    researchmap

  • PHOTOSENSITIZED OXYGENATION REACTIONS OF 1,3-DITHIANES THROUGH COOPERATIVE SINGLE ELECTRON-TRANSFER PATHWAY AND SINGLET OXYGEN PATHWAY

    M KAMATA, M SATO, E HASEGAWA

    TETRAHEDRON LETTERS33 ( 35 ) 5085 - 5088   1992年8月

     詳細を見る

    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  

    Photosensitized oxygenation reactions of 2-(p-methylphenyl)-1,3-dithiane 1a, and 2,2-di-(p-methylphenyl)-1,3-dithiane 1b afforded carbony compounds, sulfoxides, and sulfones at the various ratios through cooperative single electron transfer (SET) pathway and singlet oxygen pathway.

    DOI: 10.1016/S0040-4039(00)61196-6

    Web of Science

    researchmap

  • Furan derivatives. Part 13 . Synthesis of thiopyrano[4,3,2‐cd]benzofuran 査読

    Takaaki Horaguchi, Kohei Hasegawa, Eietsu Hasegawa, Takahachi Shimizu, Kiyoshi Tanemura, Tsuneo Suzuki

    Journal of Heterocyclic Chemistry29 ( 2 ) 503 - 509   1992年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Thiopyrano[4,3,2‐cd]benzofuran 9 possessing benzofuran and methylenethiopyran structures in the molecule was synthesized starting from 1‐chloro‐4‐methoxy‐2‐nitrobenzene 11. Some reactions (formylation, protonation and catalytic hydrogenation) on 9 were examined. The 2‐position of 9 was highly reactive toward electrophilic reagents and the furan ring was readily reduced by catalytic hydrogenation with palladium‐charcoal. Thiopyrano[4,3,2‐cd]benzofuran 9 has both properties of methylenethiopyran and benzofuran. Copyright © 1992 Journal of Heterocyclic Chemistry

    DOI: 10.1002/jhet.5570290236

    Scopus

    researchmap

  • DEPROTECTION OF 1,3-DITHIANES BY ANTIMONY PENTACHLORIDE VIA SINGLE ELECTRON-TRANSFER PROCESSES

    M KAMATA, H OTOGAWA, E HASEGAWA

    TETRAHEDRON LETTERS32 ( 50 ) 7421 - 7424   1991年12月

     詳細を見る

    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 variety of 1,3-dithianes was converted to the corresponding carbonyl compounds in good yields when those substances were treated with antimony pentachloride in methylene chloride. Single electron transfer from dithianes to antimony pentachloride was proposed as an initiation step of the reaction.

    DOI: 10.1016/0040-4039(91)80123-N

    Web of Science

    researchmap

  • Free radical trapping of α-keto radicals derived from α,β-epoxy ketones via photoinduced single electron transfer process

    Eietsu Hasegawa, Kenyuki Ishiyama, Takaaki Horaguchi, Takahachi Shimizu

    Tetrahedron Letters32 ( 18 ) 2029 - 2032   1991年4月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Irradiation of aromatic α,β-epoxy ketones in the presence of allyltributyltin afforded α-allyl-β-hydroxy ketones by a single electron transfer mechanism. © 1991.

    DOI: 10.1016/S0040-4039(00)78899-X

    Web of Science

    researchmap

  • PHOTOSENSITIZED [2+2] CYCLOREVERSION REACTIONS OF ARYLATED CAGE COMPOUNDS IN NONPOLAR-SOLVENTS - HIGHLY EFFICIENT ADIABATIC EXCIPLEX ISOMERIZATION

    E HASEGAWA, K OKADA, H IKEDA, Y YAMASHITA, T MUKAI

    JOURNAL OF ORGANIC CHEMISTRY56 ( 6 ) 2170 - 2178   1991年3月

     詳細を見る

    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  

    Photosensitized [2+2] cycloreversion reactions of arylated cage compounds 1 to dienes 2 using several cyanoaromatics as sensitizers are reported. In acetonitrile, 1a isomerized to 2a via an efficient cation-radical chain process. In contrast, the isomerization of 1a to 2a proceeded via an exciplex in benzene. Interestingly, the exciplex emission maximum observed in the fluorescence quenching by 1a was the same as that by 2a. Such a coincidence was also observed in a series of arylated cage compounds 1a-d and dienes 2a-d in various solvents. These observations together with the results obtained from reaction and exciplex emission quenching experiments clearly demonstrated the occurrence of adiabatic exciplex isomerization of 1 to 2. Efficiencies (A(e)) of the adiabatic process obtained by comparing the intensities of the observed exciplex emissions with those of diene exciplex emissions were quite high and became almost quantitative in some cases. A(e) values were found to increase as (1) the oxidation potentials (E1/2ox) of cage compounds 1a-d decreased, (2) the reduction potentials (E1/2red) of sensitizers increased, and (3) the solvent polarity (E(T)) increased.

    DOI: 10.1021/jo00006a039

    Web of Science

    researchmap

  • Exploratory Study on Photoinduced Single Electron Transfer Reactions of α,β-Epoxy Ketones with Amines

    Eietsu Hasegawa, Kenyuki Ishiyama, Takaaki Horaguchi, Takahachi Shimizu

    Journal of Organic Chemistry56 ( 4 ) 1631 - 1635   1991年2月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Photoinduced single electron transfer (SET) reactions of α,β-epoxy ketones have been studied using alkylamine electron donors. Irradiation of chalcone epoxide 1 with triethylamine (TEA) afforded β-diketone 2 and β-hydroxy ketone 3. Photoreaction of 1 with TEA in MeOH resulted in a slightly increased product ratio (3/2) compared with that in MeCN. When 1,4-diazabicyclo[2.2.2]octane (DABCO) was used instead of TEA, a decrease in the yield of 3 was observed. Only 2 was obtained on irradiation of a solution of 1 in TEA and MeCN containing LiClO4. Studies of photoreactions of dypnone epoxide 9, benzoylisopropylethylene epoxide 12, and acrylophenone epoxide 15 indicate that the nature of β-substituent also influences the product distribution. It was also found that 1,6-bis(dimethylamino)pyrene (BDMAP) sensitizes the photoreaction of 1 in the presence of TEA to produce 2. Based on the results obtained, a reaction mechanism involving selective Cα–O bond cleavage of intermediate α,β-epoxy ketone anion radicals is proposed. © 1991, American Chemical Society. All rights reserved.

    DOI: 10.1021/jo00004a052

    Web of Science

    researchmap

  • Photoinduced single electron transfer reactions of 1,3-dithianes and 1,3-dithiolanes sensitized by triphenylpyrylium salt in the presence of molecular oxygen

    Masaki Kamata, Yoshihiro Kato, Eietsu Hasegawa

    Tetrahedron Letters32 ( 34 ) 4349 - 4352   1991年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Triphenylpyrylium salt sensitized photoreactions of several dithianes and dithiolanes produced carbonyl compounds in good yields in the presence of molecular oxygen. Molecular oxygen trapping of carbon radical intermediates generated through selective CS bond cleavage of dithiane and dithiolane cation radicals is proposed. © 1991.

    DOI: 10.1016/S0040-4039(00)92167-1

    Scopus

    researchmap

  • Conformational effects in photocyclization of six and seven-membered ring alkoxyketones 査読

    Takaaki Horaguchi, Haruki Iwanami, Takakazu Tanaka, Eietsu Hasegawa, Takahachi Shimizu

    Journal of the Chemical Society, Chemical Communications ( 1 ) 44 - 46   1991年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Irradiation of 8-alkoxytetrahydro-1-naphthalenones 5 gave rearranged naphthyl alcohols 11 as major products and in contrast, 4- alkoxytetrahydrobenzocyclohepten-5-ones 6 afforded tetrahydrocyclohepta[cd] benzofurans 14 in good yields
    the difference in reactivities is attributed to the conformation of six- and seven-membered rings.

    DOI: 10.1039/C39910000044

    Scopus

    researchmap

  • Selective C<sup>α</sup>-O bond cleavage of α,β-epoxy ketones to aldols induced by free radical processes

    Eietsu Hasegawa, Kenyuki Ishiyama, Takaaki Horaguchi, Takahachi Shimizu

    Journal of the Chemical Society, Chemical Communications ( 7 ) 550 - 552   1990年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Several α,β-epoxy ketones were converted to aldols in good yields upon irradiation or heating with azoisobutyronitrile in the presence of tributyltin hydride in benzene; the reactions involve selective C α-O bond cleavage of the oxiranylmethyl radicals derived from these substances.

    DOI: 10.1039/C39900000550

    Scopus

    researchmap

  • Selective Cα-O bond cleavage of chalcone epoxides induced by pyrylium salt sensitized photoreactions and dark reactions with cerium(iv) salts

    Eietsu Hasegawa, Kenyuki Ishiyama, Hiroki Kashiwazaki, Takaaki Horaguchi, Takahachi Shimizu

    Tetrahedron Letters31 ( 28 ) 4045 - 4048   1990年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The Cβ-O bonds of chalcone epoxides (1a, 1b) were selectively cleaved by pyrylium salt sensitized photoreactions, affording β-ketoaldehydes (2a, 2b) in CH2Cl2and MeOH-adducts (3a, 3b) in MeOH. Similarly. cerium(IV) salts catalyzed the MeOH-adduct formations of 1a and 1b in the dark. On the other hand, nitrate ester (4b) was obtained on treatment of 1b with a cerium(IV) salt in MeCN. © 1990.

    DOI: 10.1016/S0040-4039(00)94495-2

    Web of Science

    researchmap

  • Furan derivatives. part 11 [1]. on substituent effects in the synthesis of 3,4,5,6‐tetrahydrocyclohepta[cd]benzofurans 査読

    Takaaki Horaguchi, Hiroto Kobayashi, Kazuhiro Miyazawa, Eietsu Hasegawa, Takahachi Shimizu, Tsuneo Suzuki, Kiyoshi Tanemura

    Journal of Heterocyclic Chemistry27 ( 4 ) 935 - 940   1990年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Tetrahydrocyclohepta[cd]benzofurans 7a‐e were synthesized by the treatment of (5‐oxo‐tetrahydro‐5H‐benzocyclohepten‐4‐yloxy)acetic acids 5a‐e with sodium acetate in acetic anhydride or by heating of their esters 6a‐e with sodium hydroxide or sodium hydride in dioxane. The yield of furans 7 decreased as a substituent R of acids 5 or esters 6 was changed from hydrogen to a methyl, ethyl, or isopropyl group. When R was a phenyl group furan 7e was always prepared in good yield. Sodium hydride was a useful base for synthesis of tetrahydrocyclohepta[cd]benzofurans. Copyright © 1990 Journal of Heterocyclic Chemistry

    DOI: 10.1002/jhet.5570270421

    Scopus

    researchmap

  • ELECTRON-TRANSFER-INDUCED REARRANGEMENTS OF PHENYLATED TRICYCLO[4.2.0.0/2,5]OCTANE AND 1,5-CYCLOOCTADIENE

    E HASEGAWA, T MUKAI, K YANAGI

    JOURNAL OF ORGANIC CHEMISTRY54 ( 9 ) 2053 - 2058   1989年4月

     詳細を見る

    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 hitherto unknown examples of cation radical isomerizations of tricyclo[4.2.0.02,5]octane and 1,5-cyclooctadiene derivatives are reported. Photoreaction of l,2,5,6-tetraphenyltricyclo[4.2.0.02,6]octane (1) with 9,10-dicyanoanthracene (DCA) afforded 1,2,5,6-tetraphenyl-1,5-cyclooctadiene (2) and 1,2,5,6-tetrapheny1tricyc1o[3.3.0.02,6(3). Upon a similar irradiation, 2 was converted to 3. Likewise, other electron acceptors, such as tetracyanoethylene (TCNE), 1,2,4,5-tetracyanobenzene (TCNB), and tris(p-bromophenyl)aminium hexachloroantimonate, catalyzed these reactions. Quenching experiments using 1,2,4,5-tetramethoxybenzene (TMB) and naphthalene (NAP) supported the occurrence of cation radical isomerizations among 1, 2, and 3. © 1989, American Chemical Society. All rights reserved.

    DOI: 10.1021/jo00270a013

    Web of Science

    researchmap

  • Novel electron-transfer photocyclization reactions of α-silyl amine α,β-unsaturated ketone and ester systems

    Wei Xu, Yoon T. Jeon, Eietsu Hasegawa, Ung C. Yoon, Patrick S. Mariano

    Journal of the American Chemical Society111 ( 1 ) 406 - 408   1989年1月

     詳細を見る

  • Furan derivatives. Part 10. Synthesis of cyclohepta[cd]benzofuran 査読

    Takaaki Horaguchi, Eietsu Hasegawa, Takahachi Shimizu, Kiyoshi Tanemura, Tsuneo Suzuki

    Journal of Heterocyclic Chemistry26 ( 2 ) 365 - 369   1989年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Cyclohepta[cd]benzofuran 2 was synthesized by heating (5‐oxo‐5H‐benzocyclohepten‐4‐yloxy)acetic acid 16 with sodium acetate in acetic anhydride or by photocyclization of 16 in acetonitrile. Several reactions of cyclohepta[cd]benzofuran 2 were examined. Protonation of 2 with trifluoroacetic acid occurred at the 2‐position to give a tropylium ion 17. Catalytic hydrogenation of 2 with palladium on charcoal proceeded smoothly to give tetrahydrocyclohepta[cd]benzofuran 18. The Diels‐Alder reaction of 2 with tetracyano‐ethylene produced an adduct 19. Formylation of 2 with phosphorus oxychloride and dimethylformamide occurred easily at the 2‐position to afford compound 20. Cyclohepta[cd]benzofuran 2 has both properties of heptafulvene and benzofuran. Copyright © 1989 Journal of Heterocyclic Chemistry

    DOI: 10.1002/jhet.5570260218

    Scopus

    researchmap

  • PHOTOADDITIONS OF ETHERS, THIOETHERS, AND AMINES TO 9,10-DICYANOANTHRACENE BY ELECTRON-TRANSFER PATHWAYS

    E HASEGAWA, MA BRUMFIELD, PS MARIANO, UC YOON

    JOURNAL OF ORGANIC CHEMISTRY53 ( 23 ) 5435 - 5442   1988年11月

     詳細を見る

    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  

    Studies were conducted to explore single electron transfer (SET) induced photoaddition reactions of 9,10-dicyanoanthracene (DCA) with a variety of n-electron donors including silicon-containing substrates (EtOCH2TMS, EtSCH2TMS, and Et2NCH2TMS). Photoadditions of EtOCH2TMS and EtSCH2TMS to DCA in MeCN occur in high yields to produce 10-substituted 9,10-dicyano-9,10-dihydroanthracenes in which the anthracenyl unit is bonded to the ether or thioether in place of the TMS substituent. The photoadducts undergo base-induced dehydrocyanation and oxidation to generate the respective 10-substituted 9-cyanoanthracenes and 10-substituted 10-cyano-9-anthrones. Photoaddition of Et2NCH2TMS to DCA in MeCN produces the corresponding dihydroanthracene adduct, which spontaneously dehydrocyanates under the reaction conditions to yield the corresponding 10-substituted 9-cyanoanthracene. This process is inefficient as compared to the O and S analogues; other products from this reaction include 9-cyano-10-aminoanthracene, 9-cyanoanthracene, and 9-cyano-10-methylanthracene. The latter product is shown to arise by secondary photoreaction of the Et2NCH2TMS-DCA anthracene adduct. Mechanisms for these photoad

    DOI: 10.1021/jo00258a007

    Web of Science

    researchmap

  • Electron-Transfer-Induced Photoadditions of the Silyl Amine Et<inf>2</inf>NCH<inf>2</inf>TMS to α,β-Unsaturated Cyclohexenones. Dual Reaction Pathways Based on Ion-Pair-Selective Cation-Radical Chemistry

    Eietsu Hasegawa, Wei Xu, Patrick S. Mariano, Ung Chan Yoon, Jin Uk Kim

    Journal of the American Chemical Society110 ( 24 ) 8099 - 8111   1988年11月

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    The photoaddition reactions of a series of conjugated cyclohexenones with the tertiary α-silyl amine Et2NCH2TMS have been subjected to exploratory and mechanistic investigation. In general, photoadditions in these systems occur to generate in modest to good yields adducts resulting from carbon-carbon bonding between the enone α-carbons and amine silicon-substituted α-carbon. These processes lead to formation of TMS and non-TMS adducts corresponding to substitution by the enone grouping for hydrogen or the trimethylsilyl grouping in the amine. The polarity and protic nature of solvents used for these photoreactions appear to control the TMS to non-TMS adduct ratios, with the former being favored in low-polarity aprotic media (MeCN) and the latter in polar protic media (MeOH). A more detailed investigation of this phenomenon by using the photoadditions of 4,4-dimethylcyclohex-2-en-1-one with Et2NCH2TMS has uncovered the source of this control. Accordingly the non-TMS to TMS adduct ratio in this system is found to be directly dependent upon the solvent polarity (Eτor AN values) and protic nature. Likewise, this ratio increases when the salts LiClO4and n-Bu4NClO4are present in the

    DOI: 10.1021/ja00232a023

    Web of Science

    researchmap

  • Synthesis and Photoisomerization Reactions of Norbornadienes Possessing Chalcone Chromophore and Reactions of the Formed Quadricyclane Derivatives

    Eietsu Hasegawa, Toshio Mukai, Takashi Toda

    NIPPON KAGAKU KAISHI1988 ( 8 ) 1215 - 1221   1988年

     詳細を見る

    記述言語:英語   掲載種別:研究論文(学術雑誌)  

    Norbornadiene-quadricyclane photo-thermal isomerization system is one of the most important and popular solar energy storage system. However, norbornadiene itself does not possess any absorption band in visible light region where the solar light energy is the most dense-region. For efficient utilization of solar light energy, norbornadienes [1] which possess a chalcone chromophore were synthesized by Diels-Alder reaction of cyclopentadiene with dehydrochalco-nes. Photoisomerization reactions of [1] gave corresponding quadricyclane derivatives [2] in good yields. The quantum yields of the isomerizations are 0.06~0.60. The properties of [1] and [2], and the results of the reactions are shown in Table 1. Solvent effects and wavelength dependency of the isomerizations are also presented. Isomerizations of [2] to [1] were carried out by contact with silver perchlorate, with trifluoroacetic acid, and even with silica gel. All the isomerizations proceeded under very mild conditions. © 1988, The Chemical Society of Japan. All rights reserved.

    DOI: 10.1246/nikkashi.1988.1215

    Scopus

    researchmap

  • Electron-transfer Photochemistry of α-silylamine-cyclohexenone Systems: Medium Effects On Reaction Pathways Followed

    Ung chan Yoon, Jin uk Kim, Eietsu Hasegawa, Patrick S. Mariano

    Journal of the American Chemical Society109 ( 14 ) 4421 - 4423   1987年7月

     詳細を見る

  • ORGANIC THERMAL-REACTIONS .63. CYCLOREVERSION REACTION OF CAGE COMPOUNDS INITIATED BY AMINIUM CATION RADICAL SALTS

    E HASEGAWA, T MUKAI

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN58 ( 11 ) 3391 - 3392   1985年

     詳細を見る

    記述言語:英語   出版者・発行元:CHEMICAL SOC JAPAN  

    DOI: 10.1246/bcsj.58.3391

    Web of Science

    researchmap

  • EXCIPLEX ISOMERIZATION IN PHOTOSENSITIZED CYCLOREVERSION REACTIONS OF CAGE COMPOUNDS

    E HASEGAWA, K OKADA, T MUKAI

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY106 ( 22 ) 6852 - 6854   1984年

     詳細を見る

    記述言語:英語   出版者・発行元:AMER CHEMICAL SOC  

    DOI: 10.1021/ja00334a070

    Web of Science

    researchmap

▶ 全件表示

MISC

  • Cyclization and ring-expansion reactions involving reductive formation and oxidative ring-opening of cyclopropanol derivatives (vol 34, pg 1688, 2005)

    Eietsu Hasegawa, Hiroyuki Tsuchida, Mutsuko Tamura

    CHEMISTRY LETTERS36 ( 8 ) 1080 - 1080   2007年8月

     詳細を見る

    記述言語:英語   出版者・発行元:CHEMICAL SOC JAPAN  

    DOI: 10.1246/cl.2007.1080

    Web of Science

    researchmap

講演・口頭発表等

  • A photo-catalytic system of benzimidazolium aryloxide catalysts and TEMPO to promote -oxyamination reaction of carbonyl compounds 招待 国際会議

    田中 司, 大江 裕貴, 木内 雄大, 長谷川 英悦

    The 14th International Symposium on Organic Reactions  2020年4月25日 

     詳細を見る

    開催年月日: 2020年4月24日 - 2020年4月26日

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Benzimidazolium aryloxides: These betaine molecules act as visible light promoted organic photoredox catalysts 招待 国際会議

    田中 司, 泉谷 徳廣, 長谷川 英悦

    The 13th International Symposium on Organic Reactions  2018年11月21日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Significant solvent effects on copper(II) tetrafluoroborate promoted oxidative ring-opening reactions of bicyclic cyclopropyl silyl ethers 招待 国際会議

    長谷川 英悦, 根本 一輝, 南雲 涼介

    The 12th International Symposium on Organic Reactions  2016年4月22日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Visible light promoted reductive transformation of various organic functional groups by using hydroxyaryl substituted benzimidazoline derivatives 招待 国際会議

    長谷川 英悦, 泉谷 徳廣, 福田 拓也, 根本 一輝

    The 2016 Korea-Japan Symposium on Frontier Photoscience held at the 26th IUPAC Symposium on Photochemistry  2016年4月3日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • ベンズイミダゾリンのマルチキャラクタードナー特性に基づく有機分子変換 招待

    長谷川 英悦

    第39回有機電子移動化学討論会  2015年6月25日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Benzimidazolines as effective reagents for photoinduced reductive transformation of organic molecules 招待 国際会議

    長谷川, 英悦, 太田 拓, 舘山みな美, 星 恒光

    The 2013 Korea-Japan Symposium on Frontier Photoscience  2013年11月24日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Electron-transfer promoted oxidative ring-opening reactions of bicyclic cyclopropanol derivatives via radical pathways 招待 国際会議

    長谷川 英悦, 南雲 涼介, 舘山みな美

    The 11th International Symposium on Organic Reactions  2013年11月19日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Single electron transfer as a key process to control radical reaction pathways 招待 国際会議

    長谷川, 英悦, 星 恒光, 舘山みな美

    The 10th International Symposium on Organic Reactions  2011年11月21日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • In situ generated amine radical cation promoted electron transfer reaction 招待 国際会議

    長谷川 英悦

    The 4th Pacific Symposium on Radical Chemistry  2009年11月19日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • 電子移動に基づくラジカル反応経路の制御 招待

    長谷川 英悦

    第3回日本化学会関東支部大会  2009年9月4日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Cyclization and ring-expansion processes involving samarium diiodide promoted reductive formation and subsequent oxidative ring-opening of cyclopropanol derivatives 招待 国際会議

    土田 裕之, 長谷川 英悦

    The 9th International Symposium on Organic Reactions  2008年11月20日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • 電子移動に基づくラジカル反応制御と環境調和型電子移動反応系の開発 招待

    長谷川 英悦

    第53回有機化学研究会(白鷺セミナー)  2008年10月22日 

     詳細を見る

    記述言語:日本語   会議種別:公開講演,セミナー,チュートリアル,講習,講義等  

    researchmap

  • Photoinduced electron-transfer promoted regioselective ring-opening reaction of cyclopropanol derivatives 招待 国際会議

    長谷川 英悦

    The 2007 Korea-Japan Symposium on Frontier Photoscience  2007年11月22日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Electron-transfer promoted regioselective ring-opening reaction of cyclopropyl silyl ethers 招待 国際会議

    長谷川 英悦

    The 14th Annual Meeting of the Korean Society of Photoscience  2007年6月7日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Photoinduced electron-transfer reaction of cyclopropyl silyl ethers, mechanistic and synthetic aspects 招待 国際会議

    長谷川 英悦

    The 2nd International Symposium on Organic Electron Transfer  2007年1月7日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Photoinduced electron transfer reaction of ketones and amines, machanistic and synthetic aspects 招待 国際会議

    長谷川 英悦

    The 8th International Symposium on Biotechnology, Metal Complexes and Catalysis  2006年11月6日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Samarium diiodide promoted intramolecular ketone–ester coupling reaction 招待 国際会議

    長谷川 英悦

    The 8th International Symposium on Organic Reactions  2006年4月23日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Contrastive behaviors of 1,3-dimethyl-2-phenylbenzimidazoline and 2-(2’-hydroxyphenyl)-1.3-dimethylbenzimidazoline in photoinduced electron-transfer reactions with benzophenones 招待 国際会議

    長谷川 英悦

    The 2005 Korea-Japan Symposium on Frontier Photoscience-Photochemistry and Nanotechnology  2005年10月7日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Novel cyclization and ring expansion processes promoted by samarium diiodide reduction and following oxidation 招待 国際会議

    長谷川 英悦

    The 1st International Symposium on Organic Electron Transfer Chemistry directed toward Organic Synthesis  2005年3月19日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • Characteristic reactivities of radical cations of 2-substituted-1,3-dimethylbenz-imidazolines with some carbonyl radical anions generated through photoinduced electron transfer processes 招待 国際会議

    長谷川 英悦

    The CREST International Symposium on Radical Ion Reactivity  2004年6月20日 

     詳細を見る

    記述言語:英語   会議種別:口頭発表(招待・特別)  

    researchmap

  • カルボニル化合物とアミン類の光誘起電子移動反応の合成化学 招待

    長谷川 英悦

    第83日本化学会春季年会  2003年8月4日 

     詳細を見る

    記述言語:日本語   会議種別:口頭発表(招待・特別)  

    researchmap

  • アミン類との光誘起電子移動過程を経由するカルボニル化合物のアニオンラジカル転位反応 招待

    長谷川 英悦

    日本化学会東北支部第18回有機化学コロキウム  1996年8月4日 

     詳細を見る

    記述言語:日本語   会議種別:シンポジウム・ワークショップ パネル(指名)  

    researchmap

  • ヨウ化サマリウム(II)による還元反応の新展開 招待

    長谷川 英悦

    新潟薬科大学化学系セミナー  1993年6月5日 

     詳細を見る

    記述言語:日本語   会議種別:公開講演,セミナー,チュートリアル,講習,講義等  

    researchmap

▶ 全件表示

共同研究・競争的資金等の研究

  • 電子移動とプロトン・水素原子移動ではたらく新規な有機光試薬と有機光触媒の開発

    研究課題/領域番号:19K05435  2019年04月 - 2022年03月

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    長谷川 英悦

      詳細を見る

    配分額:4420000円 ( 直接経費:3400000円 、 間接経費:1020000円 )

    今,光を用いる有機合成が大きな注目を集めている。一方,グリーンケミストリーの立場から希少・高価な遷移金属を用いないメタルフリー光試薬と光触媒の開発が強く求められている。還元型ベンズイミダゾリン(BIH)と酸化型ベンズイミダゾリウム(BI+)は,補酵素NADHとNAD+に類似の人工の酸化還元(レドックス)対である。本研究では,BIHとBI+のレドックス特性を生かして,還元反応に適用可能な新規有機光試薬(電子・プロトン・水素原子ドナー)と有機光触媒(電子ドナー)の開発を目的とする。推進方針として,種々の置換基Rを有するBIH-RとBI+-Rを光試薬と光触媒として多様な基質に適用して作用機構の解明を行い,それらの特性を明らかにして性能向上に繋げる。これらの還元反応系で発生する有機ラジカルアニオンの新たな反応制御法を開発する。また,無機物質の還元にも適用して,酸素分子還元による新規過酸化水素発生法の開発および金属イオンの還元を試みる。さらに,BIH-RとBI+-Rの新たな物性探索を行い新機能開拓にも取り組む。R元年度の実績概要は次の通りである。まず,ベタインBI+-ArO-とヒドリド還元剤との協働光触媒系の開発を達成し,さらにBI+-ArO-とニトロキシルラジカルとの新規協働光触媒系の開発に取り組んだ。次に,ヒドロキシ基置換BIH-ArOHによる光脱スルホニル化で生じるラジカル中間体の競争的な水素化と酸素化を見出し,機構解明に取り組んだ。また,BIH-Rと酸素分子が協働するラジカル中間体の高選択的酸素化を見出し,推定されたラジカルBI・-RのESR検出を試みた。当初はR2年度実施予定であったアミノアレーン置換体BIH-PhNR2の光試薬能とBI+-PhNR2の光触媒能を調査した。また,硫酸イオン構造を有するBIH-PhOSO3-とBI+-PhOSO3-を新たに合成した。

    researchmap

  • 遷移状態制御による三重項ハーベスト

    研究課題/領域番号:16KT0049  2016年07月 - 2019年03月

    日本学術振興会  科学研究費助成事業 基盤研究(B)  基盤研究(B)

    生駒 忠昭, 長谷川 英悦, 矢後 友暁

      詳細を見る

    配分額:18330000円 ( 直接経費:14100000円 、 間接経費:4230000円 )

    元素戦略に基づいたグリーンイノベーションを希求する社会的要請を背景に、有機材料を用いた次世代の光電エネルギー変換デバイスに対する期待が著しく高まっている。しかしながら、有機電界発光ダイオードや有機太陽電池の変換効率は著しく低いため、本格的実用化には至っていない。有機電子デバイスの超高効率化を実現するためには、三重項励起子の有効利用(三重項ハーベスト)が鍵を握っている。本研究課題では、三重項ハーベストである三重項融合の遷移状態におけるスピン角運動量制御によって、反応効率を上げることに成功した。

    researchmap

  • 光活性化に基づく新規スーパー有機ドナー試薬の開発と触媒化

    研究課題/領域番号:16K05689  2016年04月 - 2019年03月

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    長谷川 英悦, 生駒 忠昭, 三浦 智明, 岩本 啓, 滝沢 進也, 村田 滋, 若松 寛

      詳細を見る

    配分額:4940000円 ( 直接経費:3800000円 、 間接経費:1140000円 )

    新規な高性能電子・水素ドナー光試薬の開発とその触媒化を目指して, 光捕集置換基(R)を有するベンズイミダゾリン(BIH-R)の光誘起電子移動反応について研究した。まず,ナフトール置換BIH(BIH-NapOH)の光励起により生じる強力電子ドナーのナフトキシド励起状態を活用してスルホンアミドの脱スルホニル化を達成した。BIH-NapOHの酸化体(BI+-NapO-)をベタイン分子として初めて光触媒として用い,BIH-Phとの電子移動を触媒再生に利用する手法(電子移動法)とヒドリド還元剤により強力電子・水素ドナーのBIH-NapO-を系内発生させる手法(ヒドリド法)の新規触媒法の開発に成功した。

    researchmap

  • プロトンおよび金属イオンとの酸塩基相互作用によるケチルラジカルの反応性制御

    研究課題/領域番号:15550028  2003年 - 2005年

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    長谷川 英悦

      詳細を見る

    配分額:3800000円 ( 直接経費:3800000円 )

    光誘起電子移動(PET)反応に関する課題では,ベンゾフェノンの光還元をプローブ反応として1,3-ジメチル-2-フェニルベンズイミダゾリン(DMPBI)および2-(2'-ヒドロキシフェニル)-1,3-ジメチルベンズイミダゾリン(σ-HPDMBI)のPET反応性について調査し,DMPBIラジカルカチオンでは2位の炭素上の脱プロトン化が,O-HPDMBIラジカルカチオンではフェノール部位の脱プロトン化が優先することが示された。また,電子供与性置換基を有するピレンおよびアントラセンを増感剤とし,ベンズイミダゾリン誘導体を還元剤とする複合光増感系の比較評価を行い,ピレンがアントラセンよりも優れた増感剤であることを明らかにした。また,2-ハロメチル-2-(3-ブテニル)置換芳香族環状ケトンのPET反応を検討し,"PET反応で生成するケチルラジカルは分子内炭素-ハロゲン結合に対して求核置換ではなく一電子移動を起こす"という結論を導いた。一方,金属酸化還元剤を用いる反応に関する課題では,ヨウ化サマリウム(II)とアシルオキシ置換ケトン,ケト炭酸エステルとの反応を検討し,分子内ケトン-エステルカップリング反応が進行することを見出した。また,γ-ケトエステル構造を有するインダノンとヨウ化サマリウム(II)の反応で生成したシクロプロパノール誘導体を酸化剤と反応させベンゾトロポロンへと導いた。次いで,ハロケトンのサマリウムバルビエ反応で得られるシクロプロパノール誘導体の酸化反応を行ない,そのワンポット反応化にも成功した。最後に,電子移動条件に依存するシクロプロピルシリルエーテルの位置選択的開環反応を見出し,その支配因子を明らかにした。今後は,これらの電子移動反応系の詳細機構解明による精密制御とその情報に基づく新規電子移動型機能性物質の創製へと展開する。

    researchmap

  • シグマトロピー転位の不斉転写能を活用する効率的不斉合成法

    研究課題/領域番号:14550821  2002年 - 2003年

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    中井 武, 長谷川 英悦, 岡村 睦雄

      詳細を見る

    配分額:4000000円 ( 直接経費:4000000円 )

    2年間の本研究でえられた主な研究成果は以下の通りである。
    (1)「[2,3]-Witing転位による不斉転写のメカニズム解明」に関しては、キラルなカルボアニオン末端を光学活性有機スズ化合物から発生させた一連の実験を行い、不斉転写が動的速度論的光学分割機構で進行することを支持する結果をえた。
    (2)「[1,4]-Wittig転位の不斉転写能の評価」は本研究において最も力を入れたテーマである。まず、アリルボルニルエーテル(endo体とexo体)のカルボアニオン転位では、めずらしい[1,4]-Wittig転位(エノラート種を生成する)が50%前後の比率で、非立体特異的に進行することを見い出した。一方、アリルcis-カルベニルエーテルやアリル-trans-ピペリチルエーテリのカルボアニオン転位では、低温でも[1,4]-転位が40〜85%の比率で、ほぼ完壁に立体特異的(立体保持)で進行することを明らかにした。これらの結果から、[1,2]-Wittig転位と競争する[1,4]-転位はラジカル開裂-再結合機構で進行するのに対して、[2,3]-Wittig転位と競争する[1,4]-転位(比較的で起こる)は協奏(pericyclic)機構で進行することが明らかとなった。さらに、アリルシリルエーテル系のカルボアニオン転位のおける[1,4]-転位(retro-Brook転位)の可能性をも検討し、これまで知られていた[1,2]-retro-Brook転位は全く起こさず、[1,4]-retro-Brook転位のみを効率的に起こす3つの反応条件を見い出した。この手法は、新しい高立体選択的エノールシリルエーテルの合成法となるので、今後の発展が期待できる。
    (3)「連続的シグマトロピー転位による不斉転写」については、アリルシクロペンテニルエーテルの系において連続的[2,3]-Wittig/[3,3]-siloxy-oxy-Cope転位([1,4]-Wittig転位と同じ生成物を与える)を検討したが、不斉転写能を検討するにはいたらなかった。

    researchmap

  • 電子移動反応のための多機能含窒素複素環化合物の開発

    研究課題/領域番号:14044030  2002年 - 2003年

    日本学術振興会  科学研究費助成事業 特定領域研究  特定領域研究

    長谷川 英悦

      詳細を見る

    配分額:3600000円 ( 直接経費:3600000円 )

    平成14年度の本特定領域研究により新規開発された2-(o-ヒドロキシフェニル)-1,3-ジメチルベンズイミダゾリン(o-HPDMBI)を用いる還元的光誘起分子変換反応に関して,平成15年度はo-HPDMBIとカルボニル化合物の光誘起電子移動反応機構の解明およびo-HPDMBIを用いる光還元法の適用反応基質の拡張の検討を行った。はじめに,o-HPDMBIとカルボニル化合物の光反応において,2位を重水素化したo-HPDMBI-dを用いた反応の検討から,まずo-HPDMBIラジカルカチオンの2位の水素がプロトンとして脱離し,その後の酸化を経てフェノール部位からのプロトンの脱離が起こる反応過程が示唆された。生成するo-HPDMBIの酸化体はベンズイミダゾリウムとフェノキシドの双極イオン構造を有すること,またこの酸化体は水素化ホウ素ナトリウムによる還元でo-HPDMBIへ変換できることが分かった。次に,長波長光を吸収する増感剤の1,6-ビスジメチルアミノピレン(BDMAP)とo-HPDMBIを用いる方法(複合光増感法)を用いて脂肪族エポキシケトンのアルドールへの変換を行ったところ,従来の1,3-ジメチル-2-フェニルベンズイミダゾリン(DMPBI)-酢酸系を用いた場合よりも良好な結果が得られた。これに対して,既知の二水素供与体であるHantzschジヒドロピリジン(HDHP)を用いたBDMAP光増感反応ではアルドールの収率は顕著に低かった。さらに,この複合光増感法をシクロプロピルケトンの開環反応およびアルケニルケトンの環化反応に適用したところ,いずれも対応する目的物が比較的良好な収率で得られた。この複合光増感法は短波長部にしか光吸収帯をもたない脂肪族反応基質の変換に特に有効であり,今後はさらに他の官能基の変換に適用して行く。

    researchmap

  • 含窒素複素環化合物を用いる可視光利用環元反応系の開発

    研究課題/領域番号:13029037  2001年

    日本学術振興会  科学研究費助成事業 特定領域研究(A)  特定領域研究(A)

    長谷川 英悦

      詳細を見る

    配分額:2200000円 ( 直接経費:2200000円 )

    本研究では,基質の光吸収特性に依存しない可視光を利用する還元的分子変換法の開発を目標とした。具体的方針として,1)可視光吸収光増感剤と1,3-ジメチル-2-フェニルベンズイミダゾリン(DMPBI)の複合系の利用,2)可視光吸収DMPBI類縁体の利用,を考えた。そして,1,6-ビスジメチルアミノピレン(BDMAP)とDMPBIの系が,ケトンのアルコールへの還元やピナコールカップリングおよびエポキシケトンのアルドールへの変換に有効であることが明かとなった。また,DMPBIの2位のフェニル基上の置換基の違いにより反応効率に顕著な差がみられた。例えばイソホロンエポキシドの反応では,メトキシ置換DMPBIの場合はアルドールの収率は80%程度であったのに対して,クロロ置換DMPBIの場合は基質の変換率とアルドールの収率ともに顕著に低かった。次いで,可視部に光吸収を有する2-アントリル体(DMABI)を用いる光還元反応を検討したところ,光増感反応に比べて基質の適用範囲の点で問題が見られた。またDMABIの光励起状態の調査(発光スペクトル,EPRスペクトル)から,励起エネルギーはアントラセン部位に非局在化していること,DMABIの蛍光強度がその酸化体に比べ顕著に弱いという事実を発見した。この現象はベンズイミダゾリン部位による2位のアントラセン環の励起一重項状態の分子内電子移動消光過程(励起エネルギー消費過程)の存在を示唆しており,還元剤として利用する場合の問題点を示している。
    以上の点から,DMPBIの分子修飾による長波長化よりも,増感剤のさらなる検討および増感剤と協同するDMPBI類縁体の新規開発を今後の研究方針としたい。

    researchmap

  • アミン類との選択的相互作用を利用する光誘起カルボニル化合物変換

    研究課題/領域番号:10640575  1998年 - 2000年

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    長谷川 英悦

      詳細を見る

    配分額:3400000円 ( 直接経費:3400000円 )

    本研究では,はじめにカルボニル化合物とアミン類との光反応により生成するイオンラジカル対の相互作用の実体を調査し,反応経路選択性制御の可能性を検討した。それに基づき種々の反応基質の変換,さらに新規電子供与体の設計・合成・反応へと展開した。その結果,以下のことが明らかとなった。ブロモメチル置換芳香族環状ケトンを反応基質として,種々のアミンとの光反応を検討したところ,アミンカチオンラジカルの性質に依存して介在する基質ラジカル中間体の反応経路選択性が顕著な影響を受けるという結果を得た。さらに,1,3-ジメチル-2-フェニルベンズイミダゾリン(DMPBl)を用いる光反応では,基質炭素ラジカル中間体はDMPBlカチオンラジカルからの水素引き抜きを起こすが,塩基を添加すると生じたDMPBlラジカルにより炭素アニオン中間体へ還元されプロトン化を経て生成物へ至ることが判明した。これらの結果を踏まえ,DMPBlおよび類縁体を用いる高効率・高選択的光誘起分子変換法の開発を目指し種々の検討を行った。DMPBl-酢酸系の利用によりエポキシケトンからヒドロキシケトンへの好収率の変換が達成され,従来の反応条件では不可能であったDMPBl酸化体塩の単離にも成功した。さらに,長波長光の利用を目指しDMPBlの2位のフェニル基を縮合芳香族炭化水素(ナフタレン,アントラセン)に置換した化合物を合成し反応に用いたところ、カルボニル化合物の光還元反応がスムーズに進行した。さらに,本光反応系へ適用可能な新規反応基質の探索を目的に,ヨウ化サマリウム(ll)を用いる種々化合物の還元反応を行ったところ、カルボニル基の一電子還元で生じるケチルラジカルの新規な分子内求核反応性が見出された。今後は,DMPBlおよびその類縁体を用いて,より精密な反応制御が可能な新規光誘起電子移動反応系の構築を目指したい。

    researchmap

  • 含窒素複素環化合物を利用する新規光還元反応系の開発

    研究課題/領域番号:08640676  1996年

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    長谷川 英悦

      詳細を見る

    配分額:2200000円 ( 直接経費:2200000円 )

    本研究課題は"含窒素複素還元化合物を利用する新規光還元反応系の開発"であり、合成が容易で手軽に使える新規光還元剤の開発を目指した。そこで、1,3-ジメチル-2-フェニルベンズイミダゾリン(DMPBI)を最初の検討化合物とした。同化合物は、一電子放出後に生成するラジカルカチオンからの効率の良い脱プロトン化と一電子放出が期待される化合物であった。具体的には、DMPBIによるα,β-エポキシケトンの光還元反応を検討し、以下の点が明らかとなった。芳香族カルボニル構造を有する反応気質とDMPBIとの光反応では、対応するβ-ヒドロキシケトンが好収率で得られた。一方、従来の光還元系で汎用されてきたトリエチルアミンと同基質の反応では極めて効率・選択性が低かった。詳細な反応条件の検討から、反応系への適量の水の添加が必須であるという興味深い事実が見い出された。本光反応の生成物収率は、申請者が別途開発した水素化トリブチルスズを用いるラジカル反応条件下での生成物収率と比べ遜色のないものである。さらに有機スズ化合物の高い毒性を考慮すると本光還元反応系の今後の発展には大きな期待が持たれる。その一方で、新たな問題点も見い出された。例えば、長波長吸収を持たない脂肪族反応基質に対する低反応性である。これらの化合物の光還元には、より長波長吸収を有する新規光還元剤の開発が望まれる。以上の結果は、本申請研究計画と実施方法の妥当性を実証したものと考える。しかしながら本研究はまだ初期段階にあり、今後さらに多様な光還元剤の設計・合成と種々の反応系への適用を検討して行かなければならない。光誘起電子移動過程の特徴を生かした真に有効な有機化合物変換法の開発研究分野はまだ新しく、今後さらに多彩な方向への展開が期待される。

    researchmap

  • 光誘起電子移動過程を利用する高効率,高選択的還元反応の開発

    研究課題/領域番号:07640713  1995年

    日本学術振興会  科学研究費助成事業 一般研究(C)  一般研究(C)

    長谷川 英悦

      詳細を見る

    配分額:2200000円 ( 直接経費:2200000円 )

    本研究課題は"光誘起電子移動過程を利用する高効率、高選択的還元反応の開発"であり、電子供与体としてアミン類を選定し、種々のカルボニル化合物の光誘起還元反応を検討した。2-置換-1,3-ジケトンのトリエチルアミンとの光反応では,2位の置換様式の違いにより顕著に異なる生成物が得られることを発見した。すなわち無置換体では、エノール形の寄与によりピナコールを、一置換体ではヒドロキシケトンを、二置換体ではシクロプロパンジオールを与えた。また、エポキシケトンと1,3-ジメル-2,3-ジフェニルベンズイミダゾリンの光反応では、好収率でヒドロキシケトンが得られた。これは従来の光反応法をはるかに凌ぐ結果で、ラジカル中間体経由の方法としては水素化トリブチルスズによる方法(本報告者の開発)にも匹敵する。一方、分子内にアニオン性脱離基としてブロモアルキル基を有する環状カルボニル化合物のN-トリメチルシリルメチル-N,N-ジエチルアミンとの光反応では好収率で環拡大生成物が得られることを発見した。さらに、光誘起電子移動反応との比較を目的に金属還元剤とブロモメチル置換オキシランの反応を検討し、この基質のアニオンラジカル反応プローブとして有用性を明らかにした。以上の結果は、本申請研究計画と実施方法の妥当性を立証したものと考えられる。しかしながら本研究はまだ初期段階にあり、今後さらに多様な反応系を用いて反応基質と電子供与体との構造-反応相関を明らかにして行かなければならない。光誘起電子移動過程の特徴を生かした真に有効な有機化合物変換法の開発研究分野はまだ新しく、今後さらに多彩な方向への展開が期待される。報告者の今後の研究も、この分野へのさらなる貢献を目指すものである。

    researchmap

  • 新規有機イオンラジカル反応プローブの開発

    研究課題/領域番号:05740388  1993年

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    長谷川 英悦

      詳細を見る

    配分額:1000000円 ( 直接経費:1000000円 )

    電子移動条反応条件下において発生する有機ラジカル種の転位反応過程と電子移動過程を経て異なる生成物を与える反応基質は電子移動反応プローブとして有望と考えられる。この考えに基づき、申請者は1-ハロ--2、3-エポキシ-3-アリールプロパンの一電子移動還元反応に検討を計画した。これらの基質の-電子還元と引き続いて起こる炭素-ハロゲン結合開裂により生成するオキシラニルメチルラジカルは選択的な炭素-炭素結合開裂を起こしビニルエーテルを与えるか、あるいは競争的に一電子還元されアニオンとなり炭素-酸素結合開裂を起こしアリルアルコールを与えるものと考えられた。反応剤としては、その適用範囲の広さから有機合成化学の分野で現在最も注目されている一電子還元剤のひとつであるヨウ化サマリウム(II)を採用することとした。上記反応基質をヘキサメチルホスホリックトリアミド(HMPA)存在下、乾燥テトラヒドロフラン中でヨウ化サマリウム(II)と反応させたところ、二つの予想生成物が共に得られた。この結果は、これらの基質の電子移動還元反応において炭素-炭素結合開裂生成物が得られた初めての例である。現在、本反応の一般性を調べるために種々の反応条件の検討と種々の誘導体の反応を行っている。今後さらに他の電子移動還元条件(光誘起電子移動および他の一電子還元剤などの利用)における上記基質の反応挙動を検討することにより、反応経路の選択性と電子移動還元条件との相関関係について明らかにして行きたい。

    researchmap

  • 光電子移動過程を利用する炭素-炭素結合形成反応に関する研究

    研究課題/領域番号:01740302  1989年

    日本学術振興会  科学研究費助成事業 奨励研究(A)  奨励研究(A)

    長谷川 英悦

      詳細を見る

    配分額:900000円 ( 直接経費:900000円 )

    researchmap

▶ 全件表示