Eietsu Hasegawa

Niigata University

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ChemInform Abstract: A Convenient Synthesis of 2-Phenyl-3-benzo(b)furanone (III) and 3- Phenyl-2-benzo(b)furanones (V).

ChemInform (1991)

Kaoru Hanaya T. Muramatsu Eietsu Hasegawa

Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

10.1002/chin.199122130

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ChemInform Abstract: Selective Cβ‐O Bond Cleavage of Chalcone Epoxides Induced by Pyrylium Salt‐Sensitized Photoreactions and Dark Reactions with Cerium( IV) Salts.

ChemInform (1991)

Eietsu Hasegawa Kenyuki Ishiyama Hiroki Kashiwazaki Takaaki Horaguchi T. Shimizu

Chalcone

Bond cleavage

Cleavage (geology)

10.1002/chin.199137131

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Citations (3)

Synthesis and photoisomerization reactions of norbornadienes possessing chalcone chromophore and reactions of the formed quadricyclane derivatives.

NIPPON KAGAKU KAISHI (1988)

Eietsu Hasegawa Toshio Mukai Takashi Toda

太陽光の有効利用のために, より長波長部に吸収を有するカルコン発色団を有する-アロイル-3-アリールノルボルナジエン誘導体 [1] を合成し, それらの光異性化反応を検討した。[1] は導入した置換基の種類によっては可視部におよぶ吸収帯をもつ。光異性化反応の量子収率は置換基によって異なるが, O.06～O.60 の値で進行し, クアドリシクラン誘導体 [2] を生成した。[2] は加熱により容易に [1] にもどるが, 過塩素酸銀, トリフルオロ酢酸またはシリカゲルとの処理によっても収率よくに異牲化する。また [2] はエタノール中室温で放置すると,高収率でエタノールを付加したトリシクラン誘導体 [7] を与えた。[1] の光異性化反応の溶媒効果や波長効果についても述べる。

Quadricyclane

Chalcone

Chromophore

10.1246/nikkashi.1988.1215

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Citations (3)

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

Journal of Heterocyclic Chemistry (1990)

Takaaki Horaguchi Hiroto Kobayashi Kazuhiro Miyazawa Eietsu Hasegawa Takahachi Shimizu

Abstract Tetrahydrocyclohepta[ cd ]benzofurans 7a‐e were synthesized by the treatment of ( 5 ‐oxo‐tetrahydro‐5 H ‐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.

Sodium hydride

Furan

Sodium hydroxide

Isopropyl

10.1002/jhet.5570270421

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Citations (18)

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

The Journal of Organic Chemistry (1999)

Eietsu Hasegawa Yukinobu Tamura Kimiko Z. Suzuki Akira Yoneoka Toshio Suzuki

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 1 and 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).

Tropone

Radical ion

Fragmentation

10.1021/jo990215v

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Citations (17)

ChemInform Abstract: Aryl‐Substituted Dimethylbenzimidazolines as Effective Reductants of Photoinduced Electron Transfer Reactions.

ChemInform (2015)

Eietsu Hasegawa et al

Abstract 2‐Aryl substituted 1,3‐dimethylbenzimidazolines are demonstrated to be effective reductants to promote a variety of photoinduced electron transfer reactions.

Photoinduced electron transfer

10.1002/chin.201547033

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

Chemical Communications (1997)

Eietsu Hasegawa

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.

Photoinduced electron transfer

Radical cyclization

10.1039/a703974c

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Citations (28)

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

Tetrahedron Letters (2014)

Eiji Tayama Kouki Horikawa Hajime Iwamoto Eietsu Hasegawa

10.1016/j.tetlet.2014.03.115

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Citations (10)

Electron Transfer Induced Stereoselective Cyclization of 2,2-Disubstituted Dibenzoylmethane to anti-1,2-Cyclopropanediol

Tetrahedron Letters (1995)

Eietsu Hasegawa

Dibenzoylmethane

Triethylamine

Diketone

Photoinduced electron transfer

10.1016/00404-0399(50)1429l-

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Citations (8)

ChemInform Abstract: Application of Biphasic Reaction Procedure Using Ferric Chloride Dissolved in an Imidazolium Salt and Benzotrifluoride (FeIm‐BTF Procedure) to Aza‐Prins Cyclization Reaction.

ChemInform (2011)

Eietsu Hasegawa Nohara Hiroi Chika Osawa Eiji Tayama Hajime Iwamoto

Abstract A combination of FeCl 3 and [bmim]FeCl 4 (or [bmim]PF 6 ) promotes the cyclization of homoallylic N‐tosylamine (I) with aldehydes using benzotrifluoride as the solvent.

Prins reaction

10.1002/chin.201113136

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Citations (0)