Search results for: Kazunari Yoshizawa

Items from 1 to 20 out of 190 results

article

Quadruple Role of Pd Catalyst in Domino Reaction Involving Aryl to Alkyl 1,5‐Pd Migration to Access 1,9‐Bridged Triptycenes

Takayuki Iwata, Satoru Kumagai, Tatsuro Yoshinaga, Masato Hanada, more

Chemistry – A European Journal > 27 > 45 > 11548 - 11553

A Pd‐catalyzed domino reaction of 1,8,13‐tribromo‐9‐methoxytriptycenes is reported. Under conventional Suzuki coupling conditions, the triptycenes underwent multiple transformations to give 1,9‐bridged triptycenes. Based on mechanistic investigations, a single Pd catalyst functions as Pd⁰, Pd^II and Pd^IV species to catalyze four distinct processes: (1) aryl to alkyl 1,5‐Pd migration, (2) intramolecular...

article

Cover Feature: Quadruple Role of Pd Catalyst in Domino Reaction Involving Aryl to Alkyl 1,5‐Pd Migration to Access 1,9‐Bridged Triptycenes (Chem. Eur. J. 45/2021)

Takayuki Iwata, Satoru Kumagai, Tatsuro Yoshinaga, Masato Hanada, more

Chemistry – A European Journal > 27 > 45 > 11478 - 11478

A Pd‐catalyzed domino reaction of 1,8,13‐tribromo‐9‐methoxytriptycenes is reported. Under conventional Suzuki coupling conditions, the triptycenes underwent multiple transformations to give 1,9‐bridged triptycenes. Based on mechanistic investigations, a single Pd catalyst functions as Pd⁰, Pd^II and Pd^IV species to catalyze four distinct processes: 1) aryl‐to‐alkyl 1,5‐Pd migration, 2) intramolecular...

article

Ammonia Formation Catalyzed by a Dinitrogen‐Bridged Dirhenium Complex Bearing PNP‐Pincer Ligands under Mild Reaction Conditions**

Fanqiang Meng, Shogo Kuriyama, Hiromasa Tanaka, Akihito Egi, more

Angewandte Chemie > 133 > 25 > 14025 - 14031

A series of rhenium complexes bearing a pyridine‐based PNP‐type pincer ligand are synthesized from rhenium phosphine complexes as precursors. A dinitrogen‐bridged dirhenium complex bearing the PNP‐type pincer ligands catalytically converts dinitrogen into ammonia during the reaction with KC₈ as a reductant and [HPCy₃]BAr^F₄ (Cy=cyclohexyl, Ar^F=3,5‐(CF₃)₂C₆H₃) as a proton source at −78 °C to afford...

article

Ammonia Formation Catalyzed by a Dinitrogen‐Bridged Dirhenium Complex Bearing PNP‐Pincer Ligands under Mild Reaction Conditions**

Fanqiang Meng, Shogo Kuriyama, Hiromasa Tanaka, Akihito Egi, more

Angewandte Chemie International Edition > 60 > 25 > 13906 - 13912

article

Synthesis, spectral characterization, density functional theory studies, and biological screening of some transition metal complexes of a novel hydrazide–hydrazone ligand of isonicotinic acid

Dina A. Tolan, Tahani I. Kashar, Kazunari Yoshizawa, Ahmed M. El‐Nahas

Applied Organometallic Chemistry > 35 > 6 > n/a - n/a

Novel Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II) complexes (1–7) of hydrazide–hydrazone ligand (H₂L) derived from the condensation of isonicotinic acid hydrazide with (Z)‐N′‐(2‐nitrobenzylidene)‐3‐oxobutanehydrazide have been prepared. The ligand and its chelates were characterized based on elemental analysis, spectral, thermal analysis, molar conductance, and magnetic moment measurements...

article

Cycling between Molybdenum‐Dinitrogen and ‐Nitride Complexes to Support the Reaction Pathway for Catalytic Formation of Ammonia from Dinitrogen

Kazuya Arashiba, Hiromasa Tanaka, Kazunari Yoshizawa, Yoshiaki Nishibayashi

Chemistry – A European Journal > 26 > 59 > 13383 - 13389

Cycling between molybdenum(I)‐dinitrogen and molybdenum(IV)‐nitride complexes was investigated under ambient reaction conditions. A kinetic study of the second‐order reaction rate for the conversion of the molybdenum‐dinitrogen complex into the molybdenum‐nitride complex indicates that the formation of the dinitrogen‐bridged dimolybdenum complex is involved in the rate‐determining step. DFT calculations...

article

Cycling between Molybdenum‐Dinitrogen and ‐Nitride Complexes to Support the Reaction Pathway for Catalytic Formation of Ammonia from Dinitrogen

Kazuya Arashiba, Hiromasa Tanaka, Kazunari Yoshizawa, Yoshiaki Nishibayashi

Chemistry – A European Journal > 26 > 59 > 13321 - 13321

Invited for the featured front cover of Kazuya Arashiba, Hiromasa Tanaka, Kazunari Yoshizawa, and Yoshiaki Nishibayashi at The University of Tokyo, Daido University, and Kyushu University. The image depicts a roulette wheel to represent the cycling reaction used in this work. Read the full text of the article at 10.1002/chem.202002200.

article

Front Cover: Cycling between Molybdenum‐Dinitrogen and ‐Nitride Complexes to Support the Reaction Pathway for Catalytic Formation of Ammonia from Dinitrogen (Chem. Eur. J. 59/2020)

Kazuya Arashiba, Hiromasa Tanaka, Kazunari Yoshizawa, Yoshiaki Nishibayashi

Chemistry – A European Journal > 26 > 59 > 13317 - 13317

Cycling between molybdenum(I)–dinitrogen and molybdenum(IV)–nitride complexes was investigated under ambient reaction conditions. Here, a new modified reaction pathway has been proposed based on the findings of experimental and theoretical results. The molecular dinitrogen (ball) on the roulette fixes as dinitrogen and nitride ligand on molybdenum complexes. The ball thrown into the roulette smoothly...

article

Three‐Step Spin State Transition and Hysteretic Proton Transfer in the Crystal of an Iron(II) Hydrazone Complex

Takumi Nakanishi, Yuta Hori, Shuqi Wu, Hiroyasu Sato, more

Angewandte Chemie > 132 > 35 > 14891 - 14897

A proton–electron coupling system, exhibiting unique bistability or multistability of the protonated state, is an attractive target for developing new switchable materials based on proton dynamics. Herein, we present an iron(II) hydrazone crystalline compound, which displays the stepwise transition and bistability of proton transfer at the crystal level. These phenomena are realized through the coupling...

article

Three‐Step Spin State Transition and Hysteretic Proton Transfer in the Crystal of an Iron(II) Hydrazone Complex

Takumi Nakanishi, Yuta Hori, Shuqi Wu, Hiroyasu Sato, more

Angewandte Chemie International Edition > 59 > 35 > 14781 - 14787

article

Anthranoxides as Highly Reactive Arynophiles for the Synthesis of Triptycenes

Takayuki Iwata, Mizuki Hyodo, Takuto Fukami, Yoshihito Shiota, more

Chemistry – A European Journal > 26 > 39 > 8506 - 8510

We report herein an efficient method to synthesize triptycenes by the reaction of benzynes and anthranoxides, which are electron‐rich and readily prepared from the corresponding anthrones. Using this method, 1,9‐syn‐substituted triptycenes were regioselectively obtained employing 3‐methoxybenzynes. This method was also applied to synthesize pentiptycenes. A DFT study revealed that the cycloaddition...

article

Cover Feature: Anthranoxides as Highly Reactive Arynophiles for the Synthesis of Triptycenes (Chem. Eur. J. 39/2020)

Takayuki Iwata, Mizuki Hyodo, Takuto Fukami, Yoshihito Shiota, more

Chemistry – A European Journal > 26 > 39 > 8479 - 8479

An efficient method to synthesize triptycenes through the reaction of benzynes and anthranoxides, which are electron‐rich and readily prepared from the corresponding anthrones, is reported. Using this method, 1,9‐syn‐substituted triptycenes were regioselectively obtained employing 3‐methoxybenzynes. This method was also applied to synthesize pentiptycenes. A DFT study revealed that the cycloaddition...

article

Mechanistic Study on Catalytic Disproportionation of Hydrazine by a Protic Pincer‐Type Iron Complex through Proton‐Coupled Electron Transfer

Hiromasa Tanaka, Seiji Hitaoka, Kazuki Umehara, Kazunari Yoshizawa, more

European Journal of Inorganic Chemistry > 2020 > 15-16 > 1472 - 1482

Density functional theory calculations have been performed for the proposal of a plausible reaction pathway for disproportionation of hydrazine catalyzed by an iron complex bearing a multiproton‐responsive pincer‐type bis(pyrazole) ligand. The pyrazole arms in this ligand are capable of serving as both Brønsted acid and base. At the first stage of the catalytic cycle, a hydrazine molecule bound to...

article

Nitrogen Fixation Catalyzed by Dinitrogen‐Bridged Dimolybdenum Complexes Bearing PCP‐ and PNP‐Type Pincer Ligands: A Shortcut Pathway Deduced from Free Energy Profiles

Akihito Egi, Hiromasa Tanaka, Asuka Konomi, Yoshiaki Nishibayashi, more

European Journal of Inorganic Chemistry > 2020 > 15-16 > 1490 - 1498

Density‐functional‐theory (DFT) calculations are carried out for the proposal of a theoretically‐plausible reaction pathway for nitrogen fixation catalyzed by dinitrogen‐bridged dimolybdenum complexes bearing pincer‐type PCP and PNP ligands. The free energy profiles of the entire reaction pathway calculated with a dispersion‐corrected functional provide a catalytic mechanism energetically more efficient...

article

Mechanistic Study on Ring‐Contracting Skeletal Rearrangement from Porphycene to Isocorrole by Experimental and Theoretical Methods

Taro Koide, Takafumi Maeda, Tsukasa Abe, Yoshihito Shiota, more

European Journal of Organic Chemistry > 2020 > 12 > 1811 - 1816

In this study, the ring contracting skeletal rearrangement reaction in one‐pot under basic conditions from octaethylporphycene to two types of isocorroles, i.e., the meso‐formyl and meso‐free forms, was confirmed and the reaction mechanism was proposed by the comparative analyses of the experimental and theoretical studies. The electron accepting nature of the porphycene and imine‐amine conversion...

article

Cover Feature: Mechanistic Study on Ring‐Contracting Skeletal Rearrangement from Porphycene to Isocorrole by Experimental and Theoretical Methods (Eur. J. Org. Chem. 12/2020)

Taro Koide, Takafumi Maeda, Tsukasa Abe, Yoshihito Shiota, more

European Journal of Organic Chemistry > 2020 > 12 > 1783 - 1783

The Cover Feature shows the rings as the background since this study is on the ring contraction of macrocyclic porphyrinoid. The color change from porphycene to isocorrole is from blue to green and purple, indicated by the background colors. The background design and color also implies that the reaction proceeded in one‐pot and the three compounds are co‐existing in the reaction system. The structures...

article

Molecular understanding of the adhesive interactions between silica surface and epoxy resin: Effects of interfacial water

Chisa Higuchi, Hiromasa Tanaka, Kazunari Yoshizawa

Journal of Computational Chemistry > 40 > 1 > 164 - 171

The molecular mechanism of the adhesion between silica surface and epoxy resin under atmospheric conditions is investigated by periodic density‐functional‐theory (DFT) calculations. Slab models of the adhesion interface were built by integrating a fragment of epoxy resin and hydroxylated (0 0 1) surface of α‐cristobalite in the presence of adsorbed water molecules. Effects of adsorbed water on the...

article

Aerobic oxidation of alkanes on icosahedron gold nanoparticle Au55

Aleksandar Staykov, Tetsuya Miwa, Kazunari Yoshizawa

Journal of Catalysis > 2018 > 364 > C > 141-153

Aerobic oxidation of cyclohexane, propane, ethane, and methane to the corresponding alcohols was investigated over an Au55 gold nanoparticle with icosahedron symmetry using density functional theory. Reaction mechanisms were elucidated and activation barriers for catalytic CH bond cleavage and corresponding alcohols’ formation were estimated. Furthermore, on the basis of the reaction rate constants...

article

Catalytic Reduction of Molecular Dinitrogen to Ammonia and Hydrazine Using Vanadium Complexes

Yoshiya Sekiguchi, Kazuya Arashiba, Hiromasa Tanaka, Aya Eizawa, more

Angewandte Chemie > 130 > 29 > 9202 - 9206

Newly designed and prepared vanadium complexes bearing anionic pyrrole‐based PNP‐type pincer and aryloxy ligands were found to work as effective catalysts for the direct conversion of molecular dinitrogen into ammonia and hydrazine under mild reaction conditions. This is the first successful example of vanadium‐catalyzed dinitrogen reduction under mild reaction conditions.

article

Catalytic Reduction of Molecular Dinitrogen to Ammonia and Hydrazine Using Vanadium Complexes

Yoshiya Sekiguchi, Kazuya Arashiba, Hiromasa Tanaka, Aya Eizawa, more

Angewandte Chemie International Edition > 57 > 29 > 9064 - 9068

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INFONA - science communication portal

Search results for: Kazunari Yoshizawa

Quadruple Role of Pd Catalyst in Domino Reaction Involving Aryl to Alkyl 1,5‐Pd Migration to Access 1,9‐Bridged Triptycenes

Cover Feature: Quadruple Role of Pd Catalyst in Domino Reaction Involving Aryl to Alkyl 1,5‐Pd Migration to Access 1,9‐Bridged Triptycenes (Chem. Eur. J. 45/2021)

Ammonia Formation Catalyzed by a Dinitrogen‐Bridged Dirhenium Complex Bearing PNP‐Pincer Ligands under Mild Reaction Conditions**

Ammonia Formation Catalyzed by a Dinitrogen‐Bridged Dirhenium Complex Bearing PNP‐Pincer Ligands under Mild Reaction Conditions**

Synthesis, spectral characterization, density functional theory studies, and biological screening of some transition metal complexes of a novel hydrazide–hydrazone ligand of isonicotinic acid

Cycling between Molybdenum‐Dinitrogen and ‐Nitride Complexes to Support the Reaction Pathway for Catalytic Formation of Ammonia from Dinitrogen

Cycling between Molybdenum‐Dinitrogen and ‐Nitride Complexes to Support the Reaction Pathway for Catalytic Formation of Ammonia from Dinitrogen

Front Cover: Cycling between Molybdenum‐Dinitrogen and ‐Nitride Complexes to Support the Reaction Pathway for Catalytic Formation of Ammonia from Dinitrogen (Chem. Eur. J. 59/2020)

Three‐Step Spin State Transition and Hysteretic Proton Transfer in the Crystal of an Iron(II) Hydrazone Complex

Three‐Step Spin State Transition and Hysteretic Proton Transfer in the Crystal of an Iron(II) Hydrazone Complex

Anthranoxides as Highly Reactive Arynophiles for the Synthesis of Triptycenes

Cover Feature: Anthranoxides as Highly Reactive Arynophiles for the Synthesis of Triptycenes (Chem. Eur. J. 39/2020)

Mechanistic Study on Catalytic Disproportionation of Hydrazine by a Protic Pincer‐Type Iron Complex through Proton‐Coupled Electron Transfer

Nitrogen Fixation Catalyzed by Dinitrogen‐Bridged Dimolybdenum Complexes Bearing PCP‐ and PNP‐Type Pincer Ligands: A Shortcut Pathway Deduced from Free Energy Profiles

Mechanistic Study on Ring‐Contracting Skeletal Rearrangement from Porphycene to Isocorrole by Experimental and Theoretical Methods

Cover Feature: Mechanistic Study on Ring‐Contracting Skeletal Rearrangement from Porphycene to Isocorrole by Experimental and Theoretical Methods (Eur. J. Org. Chem. 12/2020)

Molecular understanding of the adhesive interactions between silica surface and epoxy resin: Effects of interfacial water

Aerobic oxidation of alkanes on icosahedron gold nanoparticle Au55

Catalytic Reduction of Molecular Dinitrogen to Ammonia and Hydrazine Using Vanadium Complexes

Catalytic Reduction of Molecular Dinitrogen to Ammonia and Hydrazine Using Vanadium Complexes

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