Tsuyoshi Fukuhara
Hokkaido University
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Featured researches published by Tsuyoshi Fukuhara.
Electrochimica Acta | 1997
Sheng-Qi Chen; Tsuyoshi Hatakeyama; Tsuyoshi Fukuhara; Shoji Hara; Norihiko Yoneda
Abstract The first electrochemical oxidative fluorination of aliphatic aldehydes ( 1 ) and cyclic ketones ( 3 ) has been successfully carried out using Base-HF as the supporting electrolyte and fluorine source. The selective displacement of formyl hydrogen by fluorine in aliphatic aldehydes electrochemically took place to give acyl fluorides ( 2 ) in good yields in the presence of the Et 3 N-5HF electrolyte. On the other hand, the selective α-bond cleavage between the carbonyl carbon and substituted α-carbon in cyclic ketones occurred in the presence of the Et 3 N-5HF electrolyte to give fluoroacyl fluorides ( 4 ), which were readily converted in good yields to the corresponding fluorocarboxylic esters ( 5 ) by the subsequent alcoholysis.
Tetrahedron | 1996
Norihiko Yoneda; Tsuyoshi Fukuhara
Abstract One-pot deaminative fluorination of aminoarenes including heteroaromatics, namely, diazotization of aminoarenes followed by in situ fluoro-dediazoniation of the corresponding diazonium ions, was successfully accomplished to produce fluoroarenes in high yields by using hydrogen fluoride combined with base solutions. The diazotization stage has been found to play the most important part in yielding fluoroarenes effectively. It was greatly influenced by the composition of the HF solution and enhanced by employing appropriate amounts of bases such as pyridine under carefully controlled conditions. The fluoro-dediazoniation stage was effectively accelerated photochemically to afford fluoroarenes having polar substituents such as hydroxyl, nitro and so on in high yields.
Journal of Fluorine Chemistry | 2000
Masanori Sawaguchi; Shoji Hara; Tsuyoshi Fukuhara; Norihiko Yoneda
Abstract In the presence of amine-HF complexes, iodotoluene difluoride reacted with unsaturated alcohols and carboxylic acids to give cyclic fluoroethers and fluorolactones, respectively.
Chemical Communications | 1996
Shoji Hara; Manabu Sekiguchi; Akihiro Ohmori; Tsuyoshi Fukuhara; Norihiko Yoneda
β-Ketoesters are selectively fluorinated at the α-position by iodotoluene difluoride and a HF–pyridine complex.
Journal of Fluorine Chemistry | 1988
Tsuyoshi Fukuhara; Norihiko Yoneda; Akira Suzuki
Abstract Fluoropyridines were prepared in high yields by the diazotization of aminopyridines in HF or HF-pyridine solutions, followed by dediazoniation in situ at 20 - 60 °C.
Journal of Fluorine Chemistry | 1998
Shoji Hara; Tsuyoshi Hatakeyama; Sheng-Qi Chen; Kenji Ishi-i; Masanori Yoshida; Masanori Sawaguchi; Tsuyoshi Fukuhara; Norihiko Yoneda
Abstract The selective and direct introduction of the fluorine atom into the α-position of β-dicarbonyl compounds was electrochemically achieved using iodotoluene difluoride as the mediator. The resulting α-fluoro-β-dicarbonyl compounds are important building blocks for biologically active compounds.
Tetrahedron | 2001
Masanori Yoshida; Shuhei Yoshikawa; Tsuyoshi Fukuhara; Norihiko Yoneda; Shoji Hara
Abstract 1-Fluoro-1,3-enynes were stereoselectively prepared by the cross-coupling reaction of 1-alkynes with β-fluoroalkenyliodides obtained from (β-fluoroalkenyl)iodonium salts. As the reaction proceeds under mild conditions, polyfunctionalized 1-fluoro-1,3-enynes could be prepared, and the synthesis of a fluorinated analog of a natural compound was achieved using this method.
Tetrahedron Letters | 1999
Shoji Hara; Kenichi Yamamoto; Masanori Yoshida; Tsuyoshi Fukuhara; Norihiko Yoneda
Abstract ( E )-β-Fluoro-α,β-unsaturated esters were stereoselectively obtained by the palladium-catalyzed carbonylation reaction of ( E )-2-fluoro-1-iodo-1-alkenyliodonium salts obtained by the addition of iodotoluene difluoride to 1-alkynes.
Tetrahedron Letters | 1998
Shoji Hara; Jun Nakahigashi; Kenji Ishi-i; Tsuyoshi Fukuhara; Norihiko Yoneda
Fluorinative ring-contraction of cyclic alkenes is induced by iodotoluene difluoride and Et3N-5HF to give difluoro cycloalkanes selectively.
Tetrahedron Letters | 1996
Shoji Hara; Sheng-Qi Chen; Takuro Hoshio; Tsuyoshi Fukuhara; Norihiko Yoneda
Abstract The electrochemical oxidation of cyclic unsaturated esters (1) was carried out using Et 3 N-5HF as the electrolyte. The ring expansion and fluorination took place to give β,β-difluorocycloalkanecarboxylic esters (2) selectively.