Papers - HIRASHITA Tsunehisa
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Practical Method for the Synthesis of Mesoionic 1,3-Diaryltetrazolium Derivatives Bearing a para-substituted Phenyl Group at the 1- or 3-Position from Anilines Reviewed International journal
Yuta Matsukawa; Tsunehisa Hirashita
Synlett 2024.03
Authorship：Last author Language：English Publishing type：Research paper (scientific journal) Publisher：Georg Thieme Verlag KG
A simple, economical, and safe method for the synthesis of mesoionic 1,3-diaryltetrazolium derivatives bearing a para-substituted phenyl group at the 1- or 3-position via thiosemicarbazides was established. Such compounds were directly obtained from the corresponding para-substituted anilines instead of aryl isothiocyanates and arylhydrazines. The newly synthesized mesoionic compounds were successfully converted into the corresponding nitrosotetrazolium salts, which were utilized as catalysts for oxidation of an aliphatic alcohol and analyzed by cyclic voltammetry to determine the correlation between the catalytic efficiencies and redox potentials. The proposed method can be widely applied and is valuable for investigating the substituent effects in mesoionic and related compounds.
DOI： 10.1055/a-2283-5749
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Synthesis, Structural Characterization, and Reactions of an Adduct Formed between Mesoionic 1,3-diphenyltetrazolium-5-thiolate and Diiodine Reviewed
Yuta Matsukawa, Mirai Nakata,Tsunehisa Hirashita, and Shuki Araki
Tetrahedron Letters 138 154960 2024.02
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
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Synthesis of stable class 5 mesoionic benzo[c]tetrazolo[2,3-a]cinnolinium thiolate, dicyanomethylide, and amides Reviewed
Mirai Nakata; Tsunehisa Hirashita; Yoshikazu Konishi; Shuki Araki
Organic & Biomolecular Chemistry 2023.04
Authorship：Corresponding author Language：English Publishing type：Research paper (scientific journal)
DOI： 10.1039/D3OB00362K
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Palladium-Catalyzed Selective o-Bromination of Mesoionic 1,3-Diphenyltetrazolium-5-olate: Switching the Directing Group from Nitrogen to Oxygen Reviewed International journal
Tsunehisa Hirashita, Harue Watanabe, Yuki Harada, Hideaki Kurabayashi, Yukinobu, Yamashita, Shiyogo Oizumi, Shuki Araki
ChemistrySelect 6 13414 - 13418 2021.12
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Pd-catalyzed bromination of mesoionic 1,3-diphenyltetrazolium-5-olate (1) was developed. In the presence of palladium acetate (5 mol%), N-bromosuccinimide (110 mol%), and p-toluenesulfonic acid (50 mol%) in 1,2-dichloroethane under reflux, olate 1 underwent bromination to give 1-(2-bromophenyl)-3-phenyltetrazolium-5-olate in a moderate yield as the major product, indicating that the 4-nitrogen atom acts as a directing group rather than the negatively charged oxygen atom. The X-ray-suitable crystals of the corresponding palladacycle were isolated from 1-mesityl-3-phentytetrazolium-5-olate and fully characterized. When both the o-positions of the 3-phenyl group were occupied by bromine atoms, o-bromination then occurred at the 1-phenyl group with the aid of the olate oxygen.
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Preparative Synthesis of 1,3-Dialkyltetrazolium-5-thiolates from 1-Alkyltetrazole-5-thiols Reviewed International journal
Hirashita, Tsunehisa; Murakami, Suguru ; Shoji, Takuo; Kurabayashi, Hideaki ; Araki, Shuki
Bulletin of the Chemical Society of Japan 2021.11
Language：English Publishing type：Research paper (scientific journal)
Mesoionic 1,3-dialkyltetrazolium-5-thiolates can be prepared in good yields by alkylation of 1-alkyltetrazole-5-thiols with secondary alcohols in concentrated sulfuric acid. The thiolates are transformed into the corresponding olates through S-alkylation followed by hydrolysis. The olates were found to be liquid at room temperature and to work effectively as polar solvents. The use of a smaller amount of sulfuric acid led to drastically different products; S-bridged dimers linked by 1,2-dimethylethylene were formed as the major products.
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The Mizoroki-Heck Reaction in Mesoionic 1-Butyl-3-methyltetrazolium-5-olate Reviewed International journal
Hideaki Kurabayashi, Tsunehisa Hirashita, Shuki Araki
Tetrahedron 99 132450 2021.10
Language：English Publishing type：Research paper (scientific journal)
1-Butyl-3-methyltetrazolium-5-olate (1), a mesoionic compound, exists as a liquid at room temperature and can be used as a polar solvent for the Mizoroki-Heck reaction, wherein it has been proven to be a superior solvent to other solvents. The reaction of iodobenzene with ethyl acrylate in the presence of palladium acetate in mesoionic liquid 1 at 40 C for 24 h gave ethyl cinnamate in 78% yield in the absence of ligands, while the use of other solvents, such as [bmim][BF4], [bmim][PF6], and DMF gave lower yields (43%, 37%, and 17%, respectively) under the same conditions. Heck-type coupling reactions of electron-deficient or electron-rich aryl iodides and bromobenzenes with olefins (15 examples, 7%–97%) were performed in 1. When a phosphine ligand was added to the reaction mixture, aryl bromides could be used, and the mesoionic liquid containing the catalysts could be reused at least five times.
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Reactions between 5-Nitroso-1,3-diphenyltetrazolium Salts and Electron-rich Arenes, Reviewed International journal
Matsukawa, Yuta; Hirashita, Tsunehisa; Araki, Shuki
Bulletin of the Chemical Society of Japan 92 540 - 544 2019.01
Language：English Publishing type：Research paper (scientific journal)
A series of reactions between 5-nitroso-1,3-diphenyltetrazolium tetrafluoroborate and methoxybenzenes, amines, thiols, sulfoxides, and sulfides, most of which are generally accepted asbeing inert to nitroso groups, is reported here. The tetrazoliumactivated nitroso functionality is capable of oxidizing the aforementioned substrates to give the corresponding oxidized products, and the nitroso tetrazolium itself is transformed into the corresponding amide or hydroxyamide, depending on the nature of the reaction partners. In the case of thioanisole, an addition product was obtained.
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Copper(I)- and Mesoionic-Hydroxyamide-Catalyzed Chemoselective Aerobic Oxidation of Primary Benzylic Alcohols Reviewed International journal
Matsukawa, Yuta; Hirashita, Tsunehisa
Synlett 30 315 - 318 2019.01
Language：English Publishing type：Research paper (scientific journal)
A new aerobic oxidation system consisting of Cu(I)I, 2,2'-bipyridine, N-methyl imidazole, and a mesoionic hydroxyamide was developed, with which selective oxidation of a broad range of benzylic alcohols was achieved.
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Tsunehisa Hirashita, Yuto Sugihara, Shota Ishikawa, Yohei Naito, Yuta Matsukawa,Shuki Araki
Synlett 29 2404 - 2407 2018.10
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
Sodium hypochlorite pentahydrate (NaOCl·5H2O) is capable of oxidizing alcohols in acetonitrile at 20 °C without the use of catalysts. The oxidation is selective to allylic, benzylic, and secondary alcohols. Aliphatic primary alcohols are not oxidized.
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Indium-Mediated Allylation of Carbonyl Compounds in Ionic Liquids: Effect of Salts in Ionic Liquids Invited Reviewed International journal
Tsunehisa Hirashita, Fusako Takahashi, Takayuki Noda, Yuji Takagi, Shuki Araki
Molecules 2018.07
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
The In-mediated allylation of carbonyl compounds can be performed in various types of solvents including ionic liquids. However, we have found that in [bmim][BF4] (where bmim = 1-butyl-3-methylimidazolium), the In-mediated coupling of crotyl bromide with benzaldehyde gives a complex mixture, and some additives, such as halides and amines, are crucial for the successful conversion to the corresponding γ-adduct. Instead, the addition of alcohols or water promotes the formation of the α-adduct. An asymmetric induction with up to 62% enantiomeric excess (ee) was observed employing cinchonidine as an additive in a binary solvent consisting of an ionic liquid and dichloromethane.
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Nitrosotetrazolium-Catalyzed Aerobic Oxidation of Alcohols to the Corresponding Carbonyl Compounds Reviewed International journal
Yuta Matsukawa, Tsunehisa Hirashita, Shuki Araki
European Journal of Organic Chemistry 1359 - 1363 2018.02
Language：English Publishing type：Research paper (scientific journal)
A mesoionic‐nitrosotetrazolium‐catalyzed aerobic oxidation of alcohols is reported. In the presence of catalytic amounts of 5‐nitroso‐1,3‐diphenyltetrazolium tetrafluoroborate (5 mol‐%) and nitric acid (20 mol‐%), a wide range of alcohols are oxidized to the corresponding aldehydes and ketones in yields of 53–100 % at room temperature under ambient air or oxygen conditions. This oxidation shows a strong preference for secondary alcohols over primary alcohols; sterically hindered alcohols are also smoothly oxidized. A mechanism involving a nitroso/NOx catalytic cycle is proposed. -
5-Nitroso-1,3-diphenyltetrazolium salt as a mediator for the oxidation of alcohols Reviewed
Yuta Matsukawa, Tsunehisa Hirashita, Shuki Araki
Tetrahdron 73 ( 42 ) 6052 - 6056 2017.10
Language：English Publishing type：Research paper (scientific journal) Publisher：Elsevier
We describe the synthesis of a mesoion-derived nitroso compound, 5-nitroso-1,3-diphenyltetrazolium tetrafluoroborate (1), and its application in the oxidation of alcohols. The structure of 1 was fully characterized by X-ray analysis, showing that it exists as a monomer in the solid state. In the cyclic voltammetric analysis of 1, a reversible redox peak was observed at 0.43 V (vs. Ag/Ag+ in MeCN) under acidic conditions. It was subsequently shown that the nitrosotetrazolium salt 1 is capable of stoichiometrically oxidizing alcohols to the corresponding carbonyl compounds effectively. This nitroso heterocycle and its reduced form, i.e., the corresponding mesoionic hydroxyamide, participate in a redox cycle involving the catalytic oxidation of alcohols by the aid of HNO3 under mild condition
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Enantioselective Barbier-type allylation of ketones using allyl halide and indium in water Reviewed
Shuichi Nakamura, Yoshichika Hara, Takashi Furukawa,Tsunehisa Hirashitaa
RSC Advances 7 15582 - 15585 2017.03
Language：English Publishing type：Research paper (scientific journal) Publisher：Royal Society of Chemistry
DOI： 10.1039/C7RA01038A
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Ionic TEMPO in Ionic Liquids: Specific Promotion of the Aerobic Oxidation of Alcohols Reviewed
Tsunehisa Hirashita,*[a] Makoto Nakanishi,[a] Tomoya Uchida,[a] Masakazu Yamamoto,[a]
ChemCatChem 8 2704 - 2709 2016.08
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
The main objective of this study was to design a recyclable
TEMPO (2,2,6,6-tetramethylpiperidinyl-N-oxyl) derivative that
could be used as a catalyst in an ionic liquid solvent for the
aerobic oxidation of alcohols by using NaNO2 and HCl as cocatalysts.
To this end, a TEMPO derivative bearing a quaternary
ammonium group, [4-Bu2MeN-TEMPO][PF6] (1), was prepared.
It was subsequently shown that this ionic TEMPO derivative is
an efficient catalyst for the aerobic oxidation of a variety of primary
and secondary alcohols. It exhibits a synergistic effect
with ionic liquid solvents and readily outperforms analogous
oxidations in methylene chloride. Moreover, the ionic TEMPO
could be recycled five times with no loss of activity. -
Analysis of Pigments in the Printing Inks of the First Japanese Postage Stamps, the Hand-Engraved Issues Reviewed International journal
2016.02
Language：English Publishing type：Research paper (scientific journal)
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Condensation of indoles and aldehydes in subcritical water without the addition of catalysts Reviewed International journal
88 1760 - 1764 2015.09
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
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Nickel-catalyzed indium(I)-mediated syn-selective propargylation of aldehydes Reviewed
Hirashita, Tsunehisa; Suzuki, Yuuki; Tsuji, Hiromitsu; Sato, Yoshiki; Naito, Kojiro; Araki, Shuki
European Journal of Organic Chemistry 2012 ( 29 ) 5668 - 5672 2012.09
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
DOI： 10.1002/ejoc.201201
Other Link： http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1099-0690
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Ionic liquid-accelerated allylation of carbonyl compounds with a catalytic amount of indium generated from in situ reduction of InCl3 with aluminium Reviewed
Hirashita, Tsunehisa; Sato, Yuki; Yamada, Dai; Takahashi, Fusako; Araki, Shuki
Chemistry Letters 40 506 - 507 2011.05
Authorship：Lead author Language：English Publishing type：Research paper (scientific journal)
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Direct benzylation and allylic alkylation in high-temperature water without added catalysts Reviewed
Hirashita, Tsunehisa; Kuwahara, Sho; Okochi, Sota; Tsuji, Makoto; Araki, Shuki
Tetrahedron Letters 51 1847 - 1851 2010.04
Language：English Publishing type：Research paper (scientific journal)
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Cyclopropanation of Electron-Deficient Alkenes with Activated Dibromomethylene Compounds Mediated by Lithium Iodide or Tetrabutylammonium Salts Reviewed
Tetrahedron 65 10390 - 10394 2009.04
Language：English Publishing type：Research paper (scientific journal)
DOI： 10.1016/j.tet.2009.10.049
Other Link： http://www.elsevier.com/locate/tet
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