Search results for: Kazunari Yoshizawa

Items from 1 to 20 out of 180 results

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

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

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

article

Two Discrete RuCp* (Cp*=Pentamethylcyclopentadienyl) Binding Modes of N‐Confused Porphyrins: Peripheral π Complex and Sitting Atop Ruthenocenophane Complex by Skeletal Transformation

Takaaki Yamamoto, Koki Mitsuno, Shigeki Mori, Shuhei Itoyama, more

Chemistry – A European Journal > 24 > 26 > 6742 - 6746

Complexation of a RuCp* cation with N‐confused tetraarylporphyrins (NCPs) forms directly bound ruthenium(II) pentamethylcyclopentadienyl (Cp*) π‐complex on a specific meso‐aryl group (e.g., phenyl) neighboring peripheral imino nitrogen of NCPs in high yields. In contrast, in the case of NCPs bearing bulky meso‐substituents (e.g., 3,5‐di‐tert‐butylphenyl), new ruthenocenophane‐like complex embedded...

article

Combined theoretical and experimental study on alcoholysis of amides on CeO2 surface: A catalytic interplay between Lewis acid and base sites

Takashi Kamachi, S.M.A. Hakim Siddiki, Yoshitsugu Morita, Md. Nurnobi Rashed, more

Catalysis Today > 2018 > 303 > C > 256-262

Alcoholysis of amides on the CeO₂ surface is investigated from density functional theory (DFT) computations, in situ FT-IR spectroscopy, and catalytic studies. The thermodynamically stable amide bonds are effectively activated by the CeO₂ catalyst under mild conditions in contrast to other metal oxide catalysts. DFT calculations demonstrated that acetamide adsorbed on the CeO₂ surface is attacked...

article

Formation and Isolation of a Four‐Electron‐Reduced Porphyrin Derivative by Reduction of a Stable 20π Isophlorin

Wataru Suzuki, Hiroaki Kotani, Tomoya Ishizuka, Yoshihito Shiota, more

Angewandte Chemie International Edition > 57 > 7 > 1973 - 1977

The two‐electron reduction of a diprotonated dodecaphenylporphyrin derivative by Na₂S₂O₄ gave a corresponding isophlorin (Iph) selectively. Formation of Iph was confirmed by spectroscopic measurements and the isolation of tetramethylated Iph. Further reduction of Iph proceeded to form an unprecedented four‐electron‐reduced porphyrin (IphH₂), which was fully characterized by spectroscopic and X‐ray...

article

Formation and Isolation of a Four‐Electron‐Reduced Porphyrin Derivative by Reduction of a Stable 20π Isophlorin

Wataru Suzuki, Hiroaki Kotani, Tomoya Ishizuka, Yoshihito Shiota, more

Angewandte Chemie > 130 > 7 > 1991 - 1995

article

Efficient 1H NMR chiral discrimination of sulfoxides caused by the dynamic nature of (R,R)-3′,3″-biBINOL

Toshio Kawanami, Kentaro Ishizuka, Hiroshi Furuno, Yoshihito Shiota, more

Tetrahedron: Asymmetry > 2017 > 28 > 11 > 1587-1590

A chiral BINOL dimer, (R,R)-3′,3″-BiBINOL, which possesses both rigid (atropos) and dynamic (tropos) axial chiralities, was found to work as an effective NMR chiral solvating reagent for the determination of the enantiomeric purities of various chiral sulfoxides. The unique chiral discrimination mechanism was also revealed by using DFT calculations and X-ray crystallographic analysis.

article

Rhenium‐Loaded TiO₂: A Highly Versatile and Chemoselective Catalyst for the Hydrogenation of Carboxylic Acid Derivatives and the N‐Methylation of Amines Using H₂ and CO₂

Takashi Toyao, S. M. A. H. Siddiki, Yoshitsugu Morita, Takashi Kamachi, more

Chemistry – A European Journal > 23 > 59 > 14848 - 14859

Herein, we report a heterogeneous TiO₂‐supported Re catalyst (Re/TiO₂) that promotes various selective hydrogenation reactions, which includes the hydrogenation of esters to alcohols, the hydrogenation of amides to amines, and the N‐methylation of amines, by using H₂ and CO₂. Initially, Re/TiO₂ was evaluated in the context of the selective hydrogenation of 3‐phenylpropionic acid methyl ester to afford...

article

Photochemical Intramolecular C−H Addition of Dimesityl(hetero)arylboranes through a [1,6]‐Sigmatropic Rearrangement

Naoki Ando, Aiko Fukazawa, Tomokatsu Kushida, Yoshihito Shiota, more

Angewandte Chemie International Edition > 56 > 40 > 12210 - 12214

A new reaction mode for triarylboranes under photochemical conditions was discovered. Photoirradiation of dimesitylboryl‐substituted (hetero)arenes produced spirocyclic boraindanes, where one of the C−H bonds in the ortho‐methyl groups of the mesityl substituents was formally added in a syn fashion to a C−C double bond of the (hetero)aryl group. Quantum chemical calculations and laser flash photolysis...

article

Photochemical Intramolecular C−H Addition of Dimesityl(hetero)arylboranes through a [1,6]‐Sigmatropic Rearrangement

Naoki Ando, Aiko Fukazawa, Tomokatsu Kushida, Yoshihito Shiota, more

Angewandte Chemie > 129 > 40 > 12378 - 12382

article

Specific Enhancement of Catalytic Activity by a Dicopper Core: Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide

Tomokazu Tsuji, Antonius Andre Zaoputra, Yutaka Hitomi, Kaoru Mieda, more

Angewandte Chemie International Edition > 56 > 27 > 7779 - 7782

A dicopper(II) complex, stabilized by the bis(tpa) ligand 1,2‐bis[2‐[bis(2‐pyridylmethyl)aminomethyl]‐6‐pyridyl]ethane (6‐hpa), [Cu₂(μ‐OH)(6‐hpa)]³⁺, was synthesized and structurally characterized. This complex catalyzed selective hydroxylation of benzene to phenol using H₂O₂, thus attaining large turnover numbers (TONs) and high H₂O₂ efficiency. The TON after 40 hours for the phenol production exceeded...

article

Specific Enhancement of Catalytic Activity by a Dicopper Core: Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide

Tomokazu Tsuji, Antonius Andre Zaoputra, Yutaka Hitomi, Kaoru Mieda, more

Angewandte Chemie > 129 > 27 > 7887 - 7890

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INFONA - science communication portal

Search results for: Kazunari Yoshizawa

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

Anthranoxides as Highly Reactive Arynophiles for the Synthesis of Triptycenes

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

Two Discrete RuCp* (Cp*=Pentamethylcyclopentadienyl) Binding Modes of N‐Confused Porphyrins: Peripheral π Complex and Sitting Atop Ruthenocenophane Complex by Skeletal Transformation

Combined theoretical and experimental study on alcoholysis of amides on CeO2 surface: A catalytic interplay between Lewis acid and base sites

Formation and Isolation of a Four‐Electron‐Reduced Porphyrin Derivative by Reduction of a Stable 20π Isophlorin

Formation and Isolation of a Four‐Electron‐Reduced Porphyrin Derivative by Reduction of a Stable 20π Isophlorin

Efficient 1H NMR chiral discrimination of sulfoxides caused by the dynamic nature of (R,R)-3′,3″-biBINOL

Rhenium‐Loaded TiO₂: A Highly Versatile and Chemoselective Catalyst for the Hydrogenation of Carboxylic Acid Derivatives and the N‐Methylation of Amines Using H₂ and CO₂

Photochemical Intramolecular C−H Addition of Dimesityl(hetero)arylboranes through a [1,6]‐Sigmatropic Rearrangement

Photochemical Intramolecular C−H Addition of Dimesityl(hetero)arylboranes through a [1,6]‐Sigmatropic Rearrangement

Specific Enhancement of Catalytic Activity by a Dicopper Core: Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide

Specific Enhancement of Catalytic Activity by a Dicopper Core: Selective Hydroxylation of Benzene to Phenol with Hydrogen Peroxide

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