Norihiro Tokitoh, Nobuhiro Takeda, Renji Okazaki,
... First Isolation of Rotational Isomers of ThiobenzaldehydesNorihiro Tokitoh, Nobuhiro Takeda, and Renji OkazakiCite this: J. Am. Chem. Soc. ...
Tópico(s): Oxidative Organic Chemistry Reactions
1994 - American Chemical Society | Journal of the American Chemical Society
Yujia Liu, Mana Kigure, Kyoka Koizumi, Nobuhiro Takeda, Masafumi Unno, Armelle Ouali,
A convenient and scalable (gram-scale) route to unprecedented T8D2-double-decker siloxanes (DDSQs) bearing four chloro (3b) or four azido (5b) groups is reported. Both compounds were characterized and proved to undergo successful nucleophilic substitution for 3b (with iodide or azide) and copper-catalyzed azide-alkyne [3 + 2] cycloaddition for 5b. All of these transformations occurred under mild conditions, and the corresponding DDSQs were prepared in very high yields. Beyond the enhanced multivalency as ...
Tópico(s): Luminescence and Fluorescent Materials
2020 - American Chemical Society | Inorganic Chemistry
Thanawat Chaiprasert, Yujia Liu, Nobuhiro Takeda, Masafumi Unno,
All- cis -tetrasiloxycyclotetrasiloxanes (Janus ring siloxanes) were facilely prepared from all- cis -cyclotetrasiloxanetetraol or sodium cyclotetrasiloxane silanolates.
Tópico(s): Synthetic Organic Chemistry Methods
2020 - Royal Society of Chemistry | Dalton Transactions
Nicha Prigyai, Supphachok Chanmungkalakul, Vuthichai Ervithayasuporn, Nuttapon Yodsin, Siriporn Jungsuttiwong, Nobuhiro Takeda, Masafumi Unno, Jaursup Boonmak, Suda Kiatkamjornwong,
A coordination complex, lithium hepta(i-butyl)silsesquioxane trisilanolate (1; Li-T7), a stable intermediate in silsesquioxane (SQ) syntheses, was successfully isolated in 65% yield and found to be highly soluble in nonpolar solvents such as hexane. The structure of Li-T7 was confirmed by NMR, IR spectroscopy, matrix-assisted laser desorption ionization time-of-flight mass spectrometry, electrospray ionization mass spectrometry, and computational simulation, providing detailed elucidation of the intermolecular ...
Tópico(s): Synthesis and properties of polymers
2019 - American Chemical Society | Inorganic Chemistry
Yujia Liu, Nobuhiro Takeda, Armelle Ouali, Masafumi Unno,
Novel tetravinyl- and tetraallyl-substituted closed double-decker siloxanes (DDSQs) were synthesized and characterized, and their structures were elucidated by X-ray crystallographic analysis. Moreover, it was shown that peripheral olefins could successfully undergo hydrosilylation quantitatively. Such tetrafunctionalizable DDSQs (DDSQ-Vinyl4 and DDSQ-Allyl4) thus constitute promising building blocks for more complex inorganic-organic hybrid materials.
Tópico(s): Supramolecular Chemistry and Complexes
2019 - American Chemical Society | Inorganic Chemistry
Yujia Liu, Kazuki Onodera, Nobuhiro Takeda, Armelle Ouali, Masafumi Unno,
Novel tetravinyl- and tetraallyl-substituted laddersiloxanes were synthesized and characterized. It was shown that peripheral olefins could successfully undergo hydrosilylation quantitatively, possibly leading to tetrahalide ladder structures. All reported functional laddersiloxanes LS (LS-vinyl4, LS-allyl4, LS-Cl4, and LS-I4) thus constitute promising building blocks for more complex inorganic–organic hybrid materials.
Tópico(s): Organoboron and organosilicon chemistry
2019 - American Chemical Society | Organometallics
Toru Tanaka, Yasuharu Hasegawa, Takashi Kawamori, Rungthip Kunthom, Nobuhiro Takeda, Masafumi Unno,
A novel synthetic method for the construction of a double-decker silsesquioxane from fluorosilanes was developed. Phenyl-substituted double-decker silsesquioxane was prepared under mild conditions by coupling difluorodiphenylsilane and a tetrasiloxanolate precursor. A similar reaction was performed using difluorovinylsilane, and a divinyl double-decker silsesquioxane was obtained. The one-step reaction of a functional difluorosilane containing an aminopropyl group afforded a novel double-decker ...
Tópico(s): Synthesis and characterization of novel inorganic/organometallic compounds
2019 - American Chemical Society | Organometallics
Taishi Uchida, Yasunobu Egawa, Takuto Adachi, Naoki Oguri, Masato Kobayashi, Takako Kudo, Nobuhiro Takeda, Masafumi Unno, Ryoji Tanaka,
Abstract Symmetric and asymmetric (Janus‐type) new “lantern cage” siloxanes (PhSiO 1.5 ) 4 (Me 2 SiO) 4 (RSiO 1.5 ) 4 (R=Ph or i Bu) were synthesized through reaction of all‐ cis ‐[PhSi(OSiMe 2 Br)O] 4 with all‐ cis ‐[RSi(OH)O] 4 (R=Ph or i Bu). These precursors were obtained by facile two or three‐step reactions from commercially available compounds. The spectroscopic properties of the resulting products were fully characterized and they showed high thermal stability and sublimation without decomposition. The ...
Tópico(s): Supramolecular Chemistry and Complexes
2018 - Wiley | Chemistry - A European Journal
Naoki Oguri, Yasunobu Egawa, Nobuhiro Takeda, Masafumi Unno,
Abstract A perfect “Janus‐cube” octasilsesquioxane, a nanometer‐scale Janus particle with two different types of substituents, was synthesized through the cross‐coupling of a “half‐cube” cyclic sodium siloxanolate with another half‐cube cyclic fluorosiloxane. The structure was confirmed by X‐ray crystallography to be a Janus cube. The overall synthesis is simple and does not require drastic separation methods compared with previous methods. The synthesis of the Janus cube demonstrates a novel siloxane ...
Tópico(s): Polyoxometalates: Synthesis and Applications
2016 - Wiley | Angewandte Chemie International Edition
Hisayuki Endo, Nobuhiro Takeda, Masanori Takanashi, Takafumi Imai, Masafumi Unno,
Tópico(s): Metal and Thin Film Mechanics
2014 - Springer Science+Business Media | Silicon
Masafumi Unno, Hisayuki Endo, Nobuhiro Takeda,
ABSTRACT The facile synthesis of all‐ cis ‐tetrasiloxycyclotetrasiloxanes (extended cyclic siloxanes) [ i ‐BuSi(OSiHMe 2 )O] 4 1 , [PhSi(OSiHMe 2 )O] 4 2 , and [CH 2 = CHSi(OSiHMe 2 )O] 4 3 was accomplished via sodium or potassium silanolates from respective trialkoxysilanes. The treatment of 1 or 2 with m ‐chloroperoxybenzoic acid afforded respective extended cyclic silanols [ i ‐BuSi(OSiMe 2 OH)O] 4 4 and [PhSi(OSiMe 2 OH)O] 4 5 . The structures of 4 and 5 were unequivocally established by X‐ray crystallography. Among ...
Tópico(s): Advanced ceramic materials synthesis
2014 - Wiley | Heteroatom Chemistry
Hisayuki Endo, Nobuhiro Takeda, Masafumi Unno,
A series of phenyl-substituted silsesquioxanes with ladder and double-decker structures were synthesized, and their structures were determined. Their spectral and physical properties were compared with those of the previously reported cage, cyclic, and acyclic silsesquioxanes. Comparison of the thermal properties clearly showed that the structures strongly affect the thermal stability.
Tópico(s): Synthesis and properties of polymers
2014 - American Chemical Society | Organometallics
Nobuhiro Takeda, Norihiro Tokitoh, Renji Okazaki,
Main group and transition metals form complexes with polysulfido ligands of a remarkable structural variety and complexity. These compounds are of high scientific interest but in addition have the potential for serving as catalysts in important industrial processes. The size of the polysulfido ligands can vary between S2 2− and S9 2− and the complexes may be mononuclear, polynuclear or even cluster-like. The type of compound formed depends not only on the metal and its oxidation number but to a ...
Tópico(s): Carbon dioxide utilization in catalysis
2012 - Springer Science+Business Media | Topics in current chemistry
H. Hamaki, Nobuhiro Takeda, M. Nabika, Norihiro Tokitoh,
β-Diketiminato and 1-aza-1,3-butadienyl–imido complexes [MCl3{TbtNC(Me)CHC(Me)NMes}(thf)n] (1a, 1b, 1c) and [M(═NTbt)Cl2{C(Me)CHC(Me)NMes}Li(tmeda)] (3a, 3b, 3c) (M = Ti, Zr, Hf) bearing an extremely bulky substituent, Tbt group (Tbt = 2,4,6-[(Me3Si)2CH]3C6H2) showed high activities for ethylene polymerization and ethylene/1-hexene copolymerization (up to 1.1 × 107 g of polymer·mol M–1 h–1). Complexes 1a, 1b, 3a, 3b, and 3c could produce ultrahigh molecular weight ethylene/1-hexene copolymers (Mw > 4 × 106) that ...
Tópico(s): Carbon dioxide utilization in catalysis
2012 - American Chemical Society | Macromolecules
Vuthichai Ervithayasuporn, Thapakorn Tomeechai, Nobuhiro Takeda, Masafumi Unno, Arada Chaiyanurakkul, Rangsinee Hamkool, Tanakorn Osotchan,
A novel octakis(3-propyl ethanethioate)octasilsesquioxane was successfully synthesized via nucleophilic substitution on octakis(3-chloropropyl)octasilsesquioxane using potassium thioacetate in aprotic dimethylformamide as a solvent. Complete substitution proceeded at room temperature within a day to produce a crystalline product in high yield. The reaction products were characterized by 1H, 13C, and 29Si NMR spectroscopy; ESI-MS; and single-crystal X-ray diffraction, confirming the structure of ...
Tópico(s): Synthetic Organic Chemistry Methods
2011 - American Chemical Society | Organometallics
Nobuhiro Takeda, Misao Gotoh, Tomofumi Matsuoka,
An efficient LC method was developed for screening the presence of quinolones (QLs)--comprising fluoroquinolones (FQs) and acidic quinolones (AQs)--residues in various livestock and fishery products. Targeted analytes were for nine FQs of marbofloxacin (MAR), ofloxacin (OFL), norfloxacin (NOR), ciprofloxacin (CIP), enrofloxacin (ENR), danofloxacin (DAN), orbifloxacin (ORB), difloxacin (DIF) and sarafloxacin (SAR), and three AQs of oxolinic acid (OXA), nalidixic acid (NAL) and flumequine (FMQ). Samples comprised ...
Tópico(s): Analytical chemistry methods development
2011 - Taylor & Francis | Food Additives & Contaminants Part A
Nobuhiro Takeda, Daisuke Watanabe, Tetsu Nakamura, Masafumi Unno,
Iridium(III) and platinum(II) complexes with a new tripodal tetradentate ligand, tris[2-(tert-butylthiomethyl)phenyl]silyl were synthesized. In addition, reaction of tris(2-((tert-butylthio)methyl)phenyl)silane with [PdCl2(PhCN)2] resulted in the cleavage of the Si−C bond to give [{Pd[2-(t-BuSCH2)C6H4]}2(μ-Cl)2].
Tópico(s): Asymmetric Hydrogenation and Catalysis
2010 - American Chemical Society | Organometallics
T. Kajiwara, Nobuhiro Takeda, Takahiro Sasamori, Norihiro Tokitoh,
The lithium salt of a borylsilyl anion, [Tbt(Mes)SiBpin]–Li+ (11: Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Mes = mesityl, pin = pinacolato), was synthesized by the boron–metal exchange reaction of a diborylsilane, Tbt(Mes)Si(Bpin)2 (8), which was synthesized by the insertion of a highly crowded diarylsilylene, Tbt(Mes)Si: (1), into the B–B bond of a diborane(4) compound, B2pin2. Although a salt of the borylsilyl anion 11 could not be isolated due to its thermal instability, the investigation of ...
Tópico(s): Catalytic Cross-Coupling Reactions
2008 - American Chemical Society | Organometallics
Hongzhi Liu, Shinichi Kondo, Nobuhiro Takeda, Masafumi Unno,
A feasible new preparation was reported for an octacarboxylphenyl functionalized spherosilicate, octakis[(pcarboxyphenyl) dimethylsilyl]silicate, which was a versatile monomer leading to other functional spherosilicate derivatives. The synthesis was started from octakis[dimethyl(p-methylphenyl)silyl]silicate. Octakis[dimethyl(pmethylphenyl) silyl]silicate was brominated by NBS to produce octakis[dimethyl(4-tribromomethylphenyl)silyl]silicate. Finally, octakis[dimethyl(4-tribromomethylphenyl)silyl] ...
Tópico(s): Porphyrin and Phthalocyanine Chemistry
2008 - American Chemical Society | Journal of the American Chemical Society
Takahiro Sasamori, Teruyuki Matsumoto, Nobuhiro Takeda, Norihiro Tokitoh,
The first stable rhodium complex having a β-ketophosphenato ligand, which is a heavier congener of a β-ketoiminato ligand, has been synthesized and characterized. Comparison of properties between rhodium β-ketophosphenates 2 and rhodium β-ketoiminate 4 revealed the unique character of the β-ketophosphenato ligand, where the trans influence of the phosphorus atom should be stronger than the nitrogen atom of the β-ketoiminato ligand.
Tópico(s): Synthesis and characterization of novel inorganic/organometallic compounds
2007 - American Chemical Society | Organometallics
Norihiro Tokitoh, A. Shinohara, Takeshi Matsumoto, Takahiro Sasamori, Nobuhiro Takeda, Yukio Furukawa,
Reaction of 9-bromo-9,10-dihydro-9-silaphenanthrene (6) with lithium diisopropylamide (LDA) in THF at room temperature afforded kinetically stabilized 9-silaphenanthrene 1a bearing an efficient steric protection group, 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl (Tbt). 9-Silaphenanthrene 1a was isolated as pale yellow crystals, and the structure of 1a was completely determined by spectroscopic and X-ray crystallographic analyses. The 1H and 13C NMR chemical shifts corresponding to the 9-silaphenanthrene ...
Tópico(s): Organoboron and organosilicon chemistry
2007 - American Chemical Society | Organometallics
Taro Tanabe, Nobuhiro Takeda, Norihiro Tokitoh,
Abstract In this paper, we report the synthesis and the structural characterization of stable examples of silanedithiol [Tbt(Mes)Si(SH) 2 ( 1 )], hydroxysilanethiol [Tbt(Mes)Si(OH)(SH) ( 3 )], and hydroxysilaneselenol [Tbt(Mes)Si(OH)(SeH) ( 7 )], which are kinetically stabilized by an effective combination of steric protection groups, Tbt (2,4,6‐tris[bis(trimethylsilyl)methyl]phenyl) and Mes (2,4,6‐trimethylphenyl). Silanedichalcogenols 1 , 3 , and 7 are suggested to exist as a monomer without any intermolecular contact such ...
Tópico(s): Organometallic Compounds Synthesis and Characterization
2007 - Wiley | European Journal of Inorganic Chemistry
Yoshiyuki Mizuhata, Takahiro Sasamori, Nobuhiro Takeda, Norihiro Tokitoh,
A kinetically stabilized 2-stannanaphthalene, the first example of a stable, neutral aromatic compound containing a tin atom, has been synthesized and fully characterized. The results of spectroscopic and crystallographic structural analyses of the compound and theoretical calculations using model compounds strongly suggest that it has a delocalized 10pi-electron ring system as does naphthalene. In addition, it was found to behave as an eta6-arene ligand in the ligand exchange reaction with [Cr(CH3CN) ...
Tópico(s): Synthesis and characterization of novel inorganic/organometallic compounds
2006 - American Chemical Society | Journal of the American Chemical Society
H. Hamaki, Nobuhiro Takeda, Norihiro Tokitoh,
Reductions of tetravalent group 4 metal β-diketiminates, [MIVCl3(nacnac)(thf)n] (2a, M = Ti; 3b, M = Zr; 3c, M = Hf; nacnac = {N(Tbt)C(Me)CHC(Me)N(Mes)}-, Tbt = 2,4,6-tris[bis(trimethylsilyl)methyl]phenyl, Mes = 2,4,6-trimethylphenyl, n = 0, 1), with 2 equiv of KC8 in the presence of LiCl and tmeda afforded the metal-imido complexes [MNTbt{C(Me)CHC(Me)N(Mes)}(μ-Cl)2Li(tmeda)] (4a, M = Ti; 4b, M = Zr; 4c, M = Hf; tmeda = Me2NCH2CH2NMe2). The formation of imido complexes 4a−c can be explained in terms of the generation of the ...
Tópico(s): Synthetic Organic Chemistry Methods
2006 - American Chemical Society | Organometallics
H. Hamaki, Nobuhiro Takeda, Takayuki Yamasaki, Takahiro Sasamori, Norihiro Tokitoh,
Tópico(s): Organometallic Complex Synthesis and Catalysis
2006 - Elsevier BV | Journal of Organometallic Chemistry
Norihiro Tokitoh, Norio Nakata, A. Shinohara, Nobuhiro Takeda, Takahiro Sasamori,
The first stable eta6-germabenzene complexes, that is, [M(CO)3(eta6-C5H5GeTbt)] {M=Cr (2), Mo (3), and W (4); Tbt=2,4,6-tris[bis(trimethylsilyl)methyl]phenyl}, have been synthesized by ligand-exchange reactions between [M(CO)3(CH3CN)3] (M=Cr, Mo, and W) and the kinetically stabilized germabenzene 1 and characterized by 1H and 13C NMR, IR, and UV/Vis spectroscopy. In the 1H and 13C NMR spectra of 2-4, all of the signals for the germabenzene rings were shifted upfield relative to their counterparts in the ...
Tópico(s): Organometallic Complex Synthesis and Catalysis
2006 - Wiley | Chemistry - A European Journal
Tomoyuki Tajima, Nobuhiro Takeda, Takahiro Sasamori, Norihiro Tokitoh,
A kinetically stabilized stannanetellone was synthesized by the telluration of an extremely hindered stannylene with (n-Bu)3PTe. The structure of the stannanetellone was determined by X-ray crystallographic analysis.
Tópico(s): Organometallic Complex Synthesis and Catalysis
2006 - American Chemical Society | Organometallics
Takahiro Sasamori, E. Mieda, Nobuhiro Takeda, Norihiro Tokitoh,
Metal triangles: The first stable telluradistibirane and telluradibismirane derivatives (see structure) have been successfully synthesized by the reaction of an overcrowded distibene (BbtSbSbBbt) and dibismuthene (BbtBiBiBbt) with nBu3PTe, respectively. (C cyan, Si red).
Tópico(s): Organometallic Compounds Synthesis and Characterization
2005 - Wiley | Angewandte Chemie International Edition
Yuji Hatada, Nobuhiro Takeda, Kazumichi Hirasawa, Yukari Ohta, Ron Usami, Yasuhiko Yoshida, William D. Grant, Susumu Ito, Koki Horikoshi,
Tópico(s): Plant Gene Expression Analysis
2005 - Springer Science+Business Media | Extremophiles
Takahiro Sasamori, Yusuke Sugiyama, Nobuhiro Takeda, Norihiro Tokitoh,
A 1,2-dibromodigermene having Bbt groups (Bbt = 2,6-bis[bis(trimethylsilyl)methyl]-4-[tris(trimethylsilyl)methyl]phenyl) was synthesized by the reaction of BbtLi with GeBr2·dioxane. X-ray crystallographic analysis revealed that it retains the GeGe double bond in the solid state, while the equilibrium between the 1,2-dibromodigermene and the corresponding bromogermylenes in solution was evidenced by the UV−vis spectroscopic studies and the chemical reactions. The reactions of the 1,2-dibromodigermene ...
Tópico(s): Organoboron and organosilicon chemistry
2005 - American Chemical Society | Organometallics