Co-reporter:Masahiro Hatazawa, Rei Takahashi, Jingyuan Deng, Hirohiko Houjou, and Kyoko Nozaki
Macromolecules October 24, 2017 Volume 50(Issue 20) pp:7895-7895
Publication Date(Web):October 6, 2017
DOI:10.1021/acs.macromol.7b01130
For the copolymerization of cyclohexene oxide (CHO) with phthalic anhydride (PA), cationic complex [Co(III)(dmap)2–Salphen][BF4] (3) showed higher activity than a combination of Co–Salphen–Cl (2) with 1 equiv of DMAP. The catalytic activity was further improved by using a bimetallic complex 5 in which the Co(III)(dmap)2–Salphen moiety was bridged by a 1,2,5,6-substituted naphthalene linker. A similar trend of catalytic activity was detected for the copolymerization of CHO with CO2.
Co-reporter:Ryo Shintani, Nana Misawa, Tomohiro Tsuda, Ryo Iino, Mikiya Fujii, Koichi Yamashita, and Kyoko Nozaki
Journal of the American Chemical Society March 15, 2017 Volume 139(Issue 10) pp:3861-3861
Publication Date(Web):February 22, 2017
DOI:10.1021/jacs.7b00344
New quinoidal fused oligosiloles containing an even number of silole units have been synthesized by a rhodium-catalyzed stitching reaction. Employing [RhCl(tfb)]2 as the catalyst significantly improved the stitching efficiency, and up to six siloles could be fused in quinoidal form. A systematic comparison of the physical properties of Si1–Si6′ confirmed the unique trend in their LUMO levels, which become higher with longer π conjugation. To understand the origin of this unusual trend, theoretical calculations were also carried out using various model compounds, and the results indicated that the terminal indenylidene (cyclopentadienylidene) moieties in Si1–Si6 (Si1a–Si6a) are primarily responsible for this phenomenon through their frontier orbital correlations with the HOMO of the central polyene unit, which becomes higher in energy with longer π conjugation.
Co-reporter:Ryo Takano, Ryo Shintani, Aiko Fukazawa, Shigehiro Yamaguchi, Koji Nakabayashi, Shin-ichi Ohkoshi, and Kyoko Nozaki
Organometallics July 24, 2017 Volume 36(Issue 14) pp:2646-2646
Publication Date(Web):May 18, 2017
DOI:10.1021/acs.organomet.7b00260
Diindenosilole Si1, a silicon-bridged fulvalene derivative, was successfully reduced to its dianions using various alkali metals, and the structures were characterized by X-ray crystallographic analysis. Radical anions of Si1 as well as dianions of π-extended Si3 could also be synthesized, and the structural and physical properties were systematically compared. It was also found that the NMR spectra of dianions Si12– and Si32– show countercation and temperature dependency for their signal broadness, indicating the possible existence of thermal interconversion between closed-shell singlet states and open-shell triplet states.
Co-reporter:Shrinwantu PalShuhei Kusumoto, Kyoko Nozaki
Organometallics 2017 Volume 36(Issue 3) pp:
Publication Date(Web):January 27, 2017
DOI:10.1021/acs.organomet.6b00892
A new 2-(di-tert-butylphosphanyl)benzenesulfonate-supported phenylplatinum(II) complex instantaneously but reversibly binds ethylene at room temperature. Direct and rapid styrene formation at room temperature via insertion of the PtII-bound ethylene into the PtII–Ph fragment followed by β-hydride elimination results in the formation of a solution-stable PtII–H complex. The PtII–H fragment is resistant toward protonolysis by acetic acid. Oxidation of the PtII–H fragment by excess CuII(OTf)2 leads to an inorganic PtII complex incapable of C–H activation.
Co-reporter: Dr. Ryo Shintani;Nana Misawa;Ryo Takano; Dr. Kyoko Nozaki
Chemistry - A European Journal 2017 Volume 23(Issue 11) pp:2660-2665
Publication Date(Web):2017/02/21
DOI:10.1002/chem.201605000
AbstractA convergent and regioselective synthesis of silicon-bridged 4-arylpyridines has been developed through a rhodium-catalyzed [2+2+2] cycloaddition of silicon-containing diynes with nitriles. The absorption and emission properties of these compounds have been examined and could be tuned by varying the substituent on the benzene ring, as well as through the protonation or alkylation of the nitrogen atom on the pyridine ring. A catalytic asymmetric synthesis of silicon-centered axially chiral spirocyclic derivatives has also been achieved with high enantioselectivity by using a newly modified MeO-MOP (MeO-MOP=2-(diphenylphosphino)-2′-methoxy-1,1′-binaphthyl) derivative as the chiral ligand. These spirocyclic compounds were found to be CPL-active (CPL=circularly polarized luminescence), representing the first CPL-active compounds based on the chirality at silicon.
Co-reporter:Yosuke Sato;Chihiro Takagi; Dr. Ryo Shintani; Dr. Kyoko Nozaki
Angewandte Chemie International Edition 2017 Volume 56(Issue 31) pp:9211-9216
Publication Date(Web):2017/07/24
DOI:10.1002/anie.201705500
AbstractA palladium-catalyzed asymmetric synthesis of silicon-stereogenic 5,10-dihydrophenazasilines was developed that proceeds via an unprecedented enantioselective 1,5-palladium migration. High enantioselectivity was achieved by employing 4,4′-bis(trimethylsilyl) (R)-Binap as the chiral ligand, and a series of mechanistic investigations were carried out to probe the catalytic cycle of this process.
Co-reporter:Yuki Tokimaru;Dr. Shingo Ito; Kyoko Nozaki
Angewandte Chemie 2017 Volume 129(Issue 49) pp:15766-15770
Publication Date(Web):2017/12/04
DOI:10.1002/ange.201707087
AbstractIn the long history of corannulene chemistry, the 1,3-dipolar cycloaddition to corannulene is unprecedented. Reported herein is the 1,3-dipolar cycloaddition of a polycyclic aromatic azomethine ylide to corannulene, a reaction which occurs exclusively at the rim bond of corannulene, from the convex side in an exo fashion. The cycloadducts were successfully converted, by successive oxidative dehydrogenation, into pyrrole-fused corannulenes, which exhibited pronounced solvatofluorochromism.
Co-reporter:Yosuke Sato;Chihiro Takagi; Dr. Ryo Shintani; Dr. Kyoko Nozaki
Angewandte Chemie 2017 Volume 129(Issue 31) pp:9339-9344
Publication Date(Web):2017/07/24
DOI:10.1002/ange.201705500
AbstractA palladium-catalyzed asymmetric synthesis of silicon-stereogenic 5,10-dihydrophenazasilines was developed that proceeds via an unprecedented enantioselective 1,5-palladium migration. High enantioselectivity was achieved by employing 4,4′-bis(trimethylsilyl) (R)-Binap as the chiral ligand, and a series of mechanistic investigations were carried out to probe the catalytic cycle of this process.
Co-reporter:Yuki Tokimaru;Dr. Shingo Ito; Kyoko Nozaki
Angewandte Chemie International Edition 2017 Volume 56(Issue 49) pp:15560-15564
Publication Date(Web):2017/12/04
DOI:10.1002/anie.201707087
AbstractIn the long history of corannulene chemistry, the 1,3-dipolar cycloaddition to corannulene is unprecedented. Reported herein is the 1,3-dipolar cycloaddition of a polycyclic aromatic azomethine ylide to corannulene, a reaction which occurs exclusively at the rim bond of corannulene, from the convex side in an exo fashion. The cycloadducts were successfully converted, by successive oxidative dehydrogenation, into pyrrole-fused corannulenes, which exhibited pronounced solvatofluorochromism.
Co-reporter:Keisuke Takahashi;Shingo Ito;Ryo Shintani
Chemical Science (2010-Present) 2017 vol. 8(Issue 1) pp:101-107
Publication Date(Web):2016/12/19
DOI:10.1039/C6SC04560J
A rhodium-catalysed stitching reaction between 2-(silylethynyl)arylboronates and 2-(silylethynyl)aryl bromides has been developed for the synthesis of unsymmetric dibenzo[a,e]pentalenes. The introduction of appropriately sized silyl groups on the starting substrates led to a high crossover selectivity without using an excess amount of either substrate. The present stitching reaction could produce a variety of unsymmetric dibenzo[a,e]pentalene derivatives, including those with electronically different substituents on the fused benzene rings as well as heteroarene fused compounds. Desilylative halogenation was also demonstrated to synthesise the corresponding halogenated dibenzo[a,e]pentalenes, which can be used as building blocks for further chemical transformations.
Co-reporter:Haruki Kisu; Hirotoshi Sakaino; Fumihiro Ito; Makoto Yamashita
Journal of the American Chemical Society 2016 Volume 138(Issue 10) pp:3548-3552
Publication Date(Web):February 23, 2016
DOI:10.1021/jacs.6b00283
A bora-Brook rearrangement, i.e., the migration of boryl group from a carbon to an oxygen atom in an isolated α-boryl-substituted alkoxide, was examined, and decisive factors for the acceleration of this reaction are disclosed. In this rearrangement, the boryl-substituted alkoxide exhibited ambiphilic reactivity toward electrophiles to afford two types of products, which are electrophiles bound either at the oxygen or at the carbon atom. Using polar solvents, a saturated backbone of the boron-containing heterocycle, or larger alkali metal cations resulted in a significantly increased reaction rate of base-catalyzed isomerization of α-borylbenzyl alcohol including the bora-Brook rearrangement.
Co-reporter:Ryo Shintani; Ryo Iino
Journal of the American Chemical Society 2016 Volume 138(Issue 11) pp:3635-3638
Publication Date(Web):March 10, 2016
DOI:10.1021/jacs.6b00082
Quinoidal fused oligosiloles, a new family of silicon-bridged π-conjugated compounds, have been synthesized for the first time based on a new synthetic strategy, a stitching reaction. Multiple carbon–carbon bonds can be formed consecutively between two oligo(silylene-ethynylene)s under rhodium catalysis in a stitching manner, and up to five siloles have been fused in a quinoidal form. Physical properties of these oligosiloles have also been investigated to find a unique trend in their LUMO levels, which become higher with longer π-conjugation.
Co-reporter:Yusuke Mitsushige, Brad P. Carrow, Shingo Ito and Kyoko Nozaki
Chemical Science 2016 vol. 7(Issue 1) pp:737-744
Publication Date(Web):
DOI:10.1039/C5SC03361F
Co-reporter:Ryo Nakano, Lung Wa Chung, Yumiko Watanabe, Yoshishige Okuno, Yoshikuni Okumura, Shingo Ito, Keiji Morokuma, and Kyoko Nozaki
ACS Catalysis 2016 Volume 6(Issue 9) pp:6101
Publication Date(Web):August 12, 2016
DOI:10.1021/acscatal.6b00911
The mechanism of linear polyethylene formation catalyzed by palladium/phosphine−sulfonate and the effect of the ligand structure on the catalytic performance, such as linearity and molecular weight of the polyethylene, were reinvestigated theoretically and experimentally. We used dispersion-corrected density functional theory (DFT-D3) to study the entire mechanism of polyethylene formation from (R2PC6H4SO3)PdMe(2,6-lutidine) (R = Me, t-Bu) and elucidated the key steps that determine the molecular weight and linearity of the polyethylene. The alkylpalladium ethylene complex is the key intermediate for both linear propagation and β-hydride elimination from the growing polymer chain. On the basis of the key species, the effects of substituents on the phosphorus atom (R = t-Bu, i-Pr, Cy, Men, Ph, 2-MeOC6H4, biAr) were further investigated theoretically to explain the experimental results in a comprehensive manner. Thus, the experimental trend of molecular weights of polyethylene could be correlated to the ΔΔG⧧ value between (i) the transition state of linear propagation and (ii) the transition state of the path for ethylene dissociation leading to β-hydride elimination. Moreover, the experimental behavior of the catalysts under varied ethylene pressure was well explained by our computation on the small set of key species elucidated from the entire mechanism. In our additional experimental investigations, [o-Ani2PC6H4SO3]PdH[P(t-Bu)3] catalyzed a hydrogen/deuterium exchange reaction between ethylene and MeOD. The deuterium incorporation from MeOD into the main chain of polyethylene, therefore, can be explained by the incorporation of deuterated ethylene formed by a small amount of Pd–H species. These insights into the palladium/phosphine−sulfonate system provide a comprehensive understanding of how the phosphine−sulfonate ligands function to produce linear polyethylene.Keywords: ethylene polymerization; linearity; molecular weight; palladium catalysts; phosphine sulfonate; suppression of β-hydride elimination
Co-reporter:Ryo Shintani, Ryo Takano and Kyoko Nozaki
Chemical Science 2016 vol. 7(Issue 2) pp:1205-1211
Publication Date(Web):09 Nov 2015
DOI:10.1039/C5SC03767K
A rhodium-catalyzed regio- and enantioselective synthesis of silicon-stereogenic silicon-bridged arylpyridinones has been developed through [2 + 2 + 2] cycloaddition of silicon-containing prochiral triynes with isocyanates. High yields and enantioselectivities have been achieved by employing an axially chiral monophosphine ligand, and this process could be applied to catalytic asymmetric synthesis of silicon-stereogenic chiral polymers for the first time. The reaction mechanism of the present catalysis has also been experimentally investigated to establish a reasonable catalytic cycle, advancing the mechanistic understanding of the rhodium-catalyzed pyridinone synthesis by [2 + 2 + 2] cycloaddition reactions.
Co-reporter:Hiromi Oyama, Midori Akiyama, Koji Nakano, Masanobu Naito, Kazuyuki Nobusawa, and Kyoko Nozaki
Organic Letters 2016 Volume 18(Issue 15) pp:3654-3657
Publication Date(Web):July 12, 2016
DOI:10.1021/acs.orglett.6b01708
[7]Helicene-like compounds with a fluorene unit were successfully synthesized using a platinum-catalyzed double cyclization reaction. Crystal structures and photophysical properties of these compounds were also studied. In particular, they were found to exhibit a high fluorescence quantum yield and a relatively large g value (dissymmetric factor) of circularly polarized luminescence (CPL) for small molecules.
Co-reporter:Yusuke Ota;Toshiki Murayama
PNAS 2016 113 (11 ) pp:2857-2861
Publication Date(Web):2016-03-15
DOI:10.1073/pnas.1518898113
In nature, many complex structures are assembled from simple molecules by a series of tailored enzyme-catalyzed reactions.
One representative example is the deoxypropionate motif, an alternately methylated alkyl chain containing multiple stereogenic
centers, which is biosynthesized by a series of enzymatic reactions from simple building blocks. In organic synthesis, however,
the majority of the reported routes require the syntheses of complex building blocks. Furthermore, multistep reactions with
individual purifications are required at each elongation. Here we show the construction of the deoxypropionate structure from
propylene in a single step to achieve a three-step synthesis of (2R,4R,6R,8R)-2,4,6,8-tetramethyldecanoic acid, a major acid component of a preen-gland wax of the graylag goose. To realize this strategy,
we focused on the coordinative chain transfer polymerization and optimized the reaction condition to afford a stereo-controlled
oligomer, which is contrastive to the other synthetic strategies developed to date that require 3–6 steps per unit, with unavoidable
byproduct generation. Furthermore, multiple oligomers with different number of deoxypropionate units were isolated from one
batch, showing application to the construction of library. Our strategy opens the door for facile synthetic routes toward
other natural products that share the deoxypropionate motif.
Co-reporter:Ryo Shintani, Hiroki Kurata, and Kyoko Nozaki
The Journal of Organic Chemistry 2016 Volume 81(Issue 8) pp:3065-3069
Publication Date(Web):April 4, 2016
DOI:10.1021/acs.joc.6b00587
An intermolecular three-component arylsilylation of alkynes has been developed under mild palladium/copper cooperative catalysis. The reaction proceeds through syn-addition of an aryl group and a silyl group across the carbon–carbon triple bond of an alkyne. This represents the first transition-metal-catalyzed fully intermolecular arylsilylation of alkynes, and transformations of the resulting products have also been demonstrated.
Co-reporter:Dr. Wen-jie Tao;Ryo Nakano;Dr. Shingo Ito ; Kyoko Nozaki
Angewandte Chemie International Edition 2016 Volume 55( Issue 8) pp:2835-2839
Publication Date(Web):
DOI:10.1002/anie.201510077
Abstract
The replacement of precious metals in catalysis by earth-abundant metals is currently one of the urgent challenges for chemists. Whereas palladium-catalyzed copolymerization of ethylene and polar monomers is a valuable method for the straightforward synthesis of functionalized polyolefins, the corresponding nickel-based catalysts have suffered from poor thermal tolerance and low molecular weight of the polymers formed. Herein, we report a series of neutral nickel complexes bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands. The Ni/IzQO system can catalyze ethylene polymerization at 50–100 °C with reasonable activity in the absence of any cocatalyst, whereas most known nickel-based catalysts are deactivated at this temperature range. The Ni/IzQO catalyst was successfully applied to the copolymerization of ethylene with allyl monomers to obtain the corresponding copolymers with the highest molecular weight reported for a Ni-catalyzed system.
Co-reporter:Dr. Wen-jie Tao;Ryo Nakano;Dr. Shingo Ito ; Kyoko Nozaki
Angewandte Chemie 2016 Volume 128( Issue 8) pp:2885-2889
Publication Date(Web):
DOI:10.1002/ange.201510077
Abstract
The replacement of precious metals in catalysis by earth-abundant metals is currently one of the urgent challenges for chemists. Whereas palladium-catalyzed copolymerization of ethylene and polar monomers is a valuable method for the straightforward synthesis of functionalized polyolefins, the corresponding nickel-based catalysts have suffered from poor thermal tolerance and low molecular weight of the polymers formed. Herein, we report a series of neutral nickel complexes bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands. The Ni/IzQO system can catalyze ethylene polymerization at 50–100 °C with reasonable activity in the absence of any cocatalyst, whereas most known nickel-based catalysts are deactivated at this temperature range. The Ni/IzQO catalyst was successfully applied to the copolymerization of ethylene with allyl monomers to obtain the corresponding copolymers with the highest molecular weight reported for a Ni-catalyzed system.
Co-reporter:Ryo Nakano
Journal of the American Chemical Society 2015 Volume 137(Issue 34) pp:10934-10937
Publication Date(Web):August 10, 2015
DOI:10.1021/jacs.5b06948
Palladium catalysts bearing imidazo[1,5-a]quinolin-9-olate-1-ylidene (IzQO) ligands polymerize α-olefins while incorporating polar monomers. The steric environment provided by N-heterocyclic-carbene (NHC) enables regioselective insertion of α-olefins and polar monomers, yielding polypropylene, propylene/allyl carboxylate copolymers, and propylene/methyl acrylate copolymer. Known polymerization catalysts bearing NHC-based ligands decompose rapidly, whereas the present catalyst is durable because of structural confinement, wherein the NHC-plane is coplanar to the metal square plane. The present catalyst system enables facile access to a new class of functionalized polyolefins and helps conceive a new fundamental principle for designing NHC-based ligands.
Co-reporter:Ryo Shintani, Hiroki Kurata and Kyoko Nozaki
Chemical Communications 2015 vol. 51(Issue 57) pp:11378-11381
Publication Date(Web):04 Jun 2015
DOI:10.1039/C5CC04172D
Rhodium-catalyzed intramolecular alkynylsilylation of alkynes is described. The reaction proceeds through syn-insertion by a cationic rhodium/triarylphosphine catalyst, representing the first alkynylsilylation of alkynes via the cleavage of a C(sp)–Si bond by transition-metal catalysis. A highly enantioselective variant is also described for the creation of a silicon stereogenic center.
Co-reporter:S. Ito, Y. Tokimaru and K. Nozaki
Chemical Communications 2015 vol. 51(Issue 1) pp:221-224
Publication Date(Web):04 Nov 2014
DOI:10.1039/C4CC06643J
The synthesis of the novel azomethine ylide, isoquinolino[4,3,2-de]phenanthridine, and its use in 1,3-dipolar cycloaddition with various alkenes and alkynes to form the corresponding fused pyrrolidines and pyrroles is reported.
Co-reporter:Takafumi Kawakami, Shingo Ito and Kyoko Nozaki
Dalton Transactions 2015 vol. 44(Issue 47) pp:20745-20752
Publication Date(Web):16 Nov 2015
DOI:10.1039/C5DT03551A
A series of iron complexes bearing a bis(imino)pyridine ligand were synthesised and examined as precatalysts for homopolymerisation of propylene. The alkyl substituents attached to the aryl group on the imine nitrogen atoms significantly affected the catalytic activity and molecular weight of the obtained polypropylenes. Copolymerisation of propylene and various allyl comonomers catalysed by iron/bis(imino)pyridine was also investigated.
Co-reporter:Shingo Ito, Wenhan Wang and Kyoko Nozaki
Polymer Journal 2015 47(7) pp:474-480
Publication Date(Web):May 13, 2015
DOI:10.1038/pj.2015.27
As chain-growth polymerization generally forms aliphatic main chains containing units such as alkylene and alkenylene, the method has rarely been applied to the construction of arylene units. Thus, the formation/introduction of arylene groups via chain-growth polymerization remains a challenging subject in polymer chemistry. In this study, we report a formal aryne/ethylene copolymerization using [2.2.1]oxabicyclic alkenes as aryne equivalents. A palladium-catalyzed copolymerization of [2.2.1]oxabicyclic alkenes with ethylene followed by acid-promoted dehydration produced novel aryne/ethylene copolymers. The use of a bulky phosphine–sulfonate ligand was essential to obtain the desired copolymers with high molecular weight.
Co-reporter:Dr. Ryo Shintani;Chihiro Takagi;Tomoaki Ito;Dr. Masanobu Naito;Dr. Kyoko Nozaki
Angewandte Chemie International Edition 2015 Volume 54( Issue 5) pp:1616-1620
Publication Date(Web):
DOI:10.1002/anie.201409733
Abstract
A rhodium-catalyzed asymmetric synthesis of silicon-stereogenic dibenzosiloles has been developed through a [2+2+2] cycloaddition of silicon-containing prochiral triynes with internal alkynes. High yields and enantioselectivities have been achieved by employing an axially chiral monophosphine ligand, and the present catalysis is also applicable to the asymmetric synthesis of a germanium-stereogenic dibenzogermole. Preliminary studies on the optical properties of these compounds are also described.
Co-reporter:Dr. Shuhei Kusumoto;Toshiumi Tatsuki ;Dr. Kyoko Nozaki
Angewandte Chemie 2015 Volume 127( Issue 29) pp:8578-8581
Publication Date(Web):
DOI:10.1002/ange.201503620
Abstract
Hydroformylation, a reaction that adds carbon monoxide and dihydrogen across an unsaturated carbon–carbon multiple bond, has been widely employed in the chemical industry since its discovery in 1938. In contrast, the reverse reaction, retro-hydroformylation, has seldom been studied. The retro-hydroformylation reaction of an aldehyde into an alkene and synthesis gas (a mixture of carbon monoxide and dihydrogen) in the presence of a cyclopentadienyl iridium catalyst is now reported. Aliphatic aldehydes were converted into the corresponding alkenes in up to 91 % yield with concomitant release of carbon monoxide and dihydrogen. Mechanistic control experiments indicated that the reaction proceeds by retro-hydroformylation and not by a sequential decarbonylation–dehydrogenation or dehydrogenation–decarbonylation process.
Co-reporter:Dr. Shuhei Kusumoto;Toshiumi Tatsuki ;Dr. Kyoko Nozaki
Angewandte Chemie 2015 Volume 127( Issue 29) pp:
Publication Date(Web):
DOI:10.1002/ange.201505499
Co-reporter:Dr. Shuhei Kusumoto;Toshiumi Tatsuki ;Dr. Kyoko Nozaki
Angewandte Chemie International Edition 2015 Volume 54( Issue 29) pp:8458-8461
Publication Date(Web):
DOI:10.1002/anie.201503620
Abstract
Hydroformylation, a reaction that adds carbon monoxide and dihydrogen across an unsaturated carbon–carbon multiple bond, has been widely employed in the chemical industry since its discovery in 1938. In contrast, the reverse reaction, retro-hydroformylation, has seldom been studied. The retro-hydroformylation reaction of an aldehyde into an alkene and synthesis gas (a mixture of carbon monoxide and dihydrogen) in the presence of a cyclopentadienyl iridium catalyst is now reported. Aliphatic aldehydes were converted into the corresponding alkenes in up to 91 % yield with concomitant release of carbon monoxide and dihydrogen. Mechanistic control experiments indicated that the reaction proceeds by retro-hydroformylation and not by a sequential decarbonylation–dehydrogenation or dehydrogenation–decarbonylation process.
Co-reporter:Dr. Shuhei Kusumoto;Toshiumi Tatsuki ;Dr. Kyoko Nozaki
Angewandte Chemie International Edition 2015 Volume 54( Issue 29) pp:
Publication Date(Web):
DOI:10.1002/anie.201505499
Co-reporter:Motonobu Takahashi, Koji Nakano, and Kyoko Nozaki
The Journal of Organic Chemistry 2015 Volume 80(Issue 8) pp:3790-3797
Publication Date(Web):March 18, 2015
DOI:10.1021/jo502889r
Benzophospholo[3,2-b]benzofuran (BPBF) derivatives were studied as a new family of phosphole-containing π-conjugated organic materials. The versatile reactivity of the trivalent phosphorus center of the parent BPBF offered access to a variety of derivatives by simple chemical modifications. The diversity-oriented synthetic route was also developed to allow facile access to BPBFs with a different substituent on the phosphorus center. Photophysical properties were revealed based on UV–vis and photoluminescence spectroscopies and theoretical calculation. The characteristic property of BPBF derivatives is highly efficient photoluminescence. In particular, phosphole oxide derivatives demonstrated intense blue fluorescence with high quantum yield over 85% even in the solid state.
Co-reporter:Shingo Ito, Wenhan Wang, Katsuyuki Nishimura, and Kyoko Nozaki
Macromolecules 2015 Volume 48(Issue 7) pp:1959-1962
Publication Date(Web):April 3, 2015
DOI:10.1021/acs.macromol.5b00315
A palladium-catalyzed alternating copolymerization of [2.2.1]oxabicyclic alkenes 1 with carbon monoxide afforded isomer mixtures of polyketones 2ktn and polyketals 2ktl. Subsequent acid-induced dehydration of polymer 2 furnished novel aromatic polymers consisting of polyketones 3ktn and polyketals 3ktl units. This formal aryne/carbon monoxide copolymerization thus generated the first example of poly(aryne-alt-carbon monoxide)s, in which o-arylene and carbonyl units are incorporated in an alternating fashion.
Co-reporter:Ryo Shintani ; Ryo Iino
Journal of the American Chemical Society 2014 Volume 136(Issue 22) pp:7849-7852
Publication Date(Web):May 21, 2014
DOI:10.1021/ja5032002
A new mode of metal-catalyzed polymerization reaction has been developed by exploiting the ability of 1,4-rhodium migration of an organorhodium(I) species. Specifically, it has been demonstrated that 3,3-diarylcyclopropenes undergo polymerization through an insertion–1,4-rhodium migration sequence by using an arylrhodium(I) initiator/catalyst to give poly(cyclopropylene-o-phenylene)s, which are difficult to synthesize by conventional polymerization methods.
Co-reporter:Shingo Ito ; Keisuke Takahashi
Journal of the American Chemical Society 2014 Volume 136(Issue 21) pp:7547-7550
Publication Date(Web):May 14, 2014
DOI:10.1021/ja502073k
Despite the high utility of aryne in organic synthesis, its polymerization has long been a significant challenge in polymer chemistry. A critical bottleneck in this process is the intrinsic instability of aryne and consequent short lifetime for polymerization. In order to circumvent the problem, we focus on a synthetic equivalent of aryne, [2.2.1]oxabicyclic alkene, as a monomer for polymerization. Palladium-catalyzed coordination–insertion polymerization of [2.2.1]oxabicyclic alkenes produced the corresponding polymers having an aliphatic main chain. Subsequent acid-promoted dehydration allowed the aliphatic main chain to be converted into an aromatic main chain to form poly(o-arylene)s. These sequential processes represent the first formal aryne polymerization, which offers an efficient method to synthesize a variety of poly(o-arylene)s in a chain-growth polymerization manner.
Co-reporter:Takahiro Ohkawara ; Kohei Suzuki ; Koji Nakano ; Seiji Mori
Journal of the American Chemical Society 2014 Volume 136(Issue 30) pp:10728-10735
Publication Date(Web):July 15, 2014
DOI:10.1021/ja5046814
Mechanistic studies were conducted to estimate (1) catalytic activity for PPC, (2) PPC/CPC selectivity, and (3) PPC/PPO selectivity for the metal-catalyzed copolymerization of propylene oxide with carbon dioxide [PPC: poly(propylene carbonate); CPC = cyclic propylene carbonate; PPO: poly(propylene oxide)]. Density functional theory (DFT) studies demonstrated that the ΔGcrb – ΔGepx value should be an effective indicator for the catalytic activities [ΔGepx: dissociation energy of ethylene oxide from the epoxide-coordinating metal complex; ΔGcrb: dissociation energy of methyl carbonate from the metal–carbonate complex]. In addition, metal complexes with a subthreshold ΔGepx value were found to show low PPC/CPC selectivity. The PPC/PPO selectivity was related to the ΔGalk – ΔGepx value and steric environment around the metal center (ΔGalk: dissociation energy of alkoxide ligand from the metal center). Based on the mechanistic studies, two metal complexes were designed and applied to the copolymerization to support validity of these indicators. The results presented here should be useful for brand-new catalyst candidates since these indicators can be easily calculated by DFT method without computing transition states.
Co-reporter:Yusuke Ota ; Shingo Ito ; Jun-ichi Kuroda ; Yoshikuni Okumura
Journal of the American Chemical Society 2014 Volume 136(Issue 34) pp:11898-11901
Publication Date(Web):August 13, 2014
DOI:10.1021/ja505558e
A series of palladium/alkylphosphine–sulfonate catalysts were synthesized and examined in the homopolymerization of ethylene and the copolymerization of ethylene and polar monomers. Catalysts with alkylphosphine–sulfonate ligands containing sterically demanding alkyl substituents afforded (co)polymers whose molecular weight was increased by up to 2 orders of magnitude relative to polymers obtained from previously reported catalyst systems. The polymer molecular weight was found to be closely correlated to the Sterimol B5 parameter of the alkyl substituents in the alkylphosphine–sulfonate ligands. Thus, the use of bulky alkylphosphine–sulfonate ligands represents an effective and versatile method to prepare high-molecular-weight copolymers of ethylene and various polar monomers, which are difficult to obtain by previously reported methods.
Co-reporter:Kohei Takahashi and Kyoko Nozaki
Organic Letters 2014 Volume 16(Issue 22) pp:5846-5849
Publication Date(Web):November 5, 2014
DOI:10.1021/ol502681y
The hydrogenation of aldehyde utilizing synthesis gas as a dihydrogen source was examined with various ruthenium catalysts, among which Ru–cyclopentadienone complexes (Shvo-type catalysts) exhibited higher activity than others. DFT calculations proved that the exchange of coordinated carbon monoxide by dihydrogen is relatively preferable in Shvo-type catalysts compared to others, which is a pre-equilibrium for the generation of the hydrogenation-active species.
Co-reporter:Dr. Carine Robert;Takahiro Ohkawara;Dr. Kyoko Nozaki
Chemistry - A European Journal 2014 Volume 20( Issue 16) pp:4789-4795
Publication Date(Web):
DOI:10.1002/chem.201303703
Abstract
Manganese-corrole complexes in combination with a co-catalyst [PPN]X ([PPN]+=bis(triphenylphosphoranylidene)iminium) were found to be new versatile catalysts for the polymerization of epoxides, copolymerization of epoxides with CO2, and copolymerization of epoxides with cyclic anhydrides affording a wide range of polymeric materials. This work should allow the synthesis of new types of improved innovative (co)polymers with original properties and would clearly increase the number of applications for polyesters, polycarbonates, and polyethers.
Co-reporter:Brad P. Carrow and Kyoko Nozaki
Macromolecules 2014 Volume 47(Issue 8) pp:2541-2555
Publication Date(Web):March 19, 2014
DOI:10.1021/ma500034g
The incorporation of polar functional groups into polyolefins can significantly alter the adhesion, barrier and surface properties, dyeability, printability, and compatibility of the resulting “functional polyolefin”. Thus, the development of methods for the controlled synthesis of functional polyolefins from industrially relevant monomers holds the potential to expand the range of applications available to this already ubiquitous class of materials. In this Perspective, recent advances in transition-metal-catalyzed functional polyolefin synthesis will be reviewed. A common thread among the innovations discussed here is the perturbation of catalyst function by tailored design of the chelating ancillary ligand, aided in many cases by improved mechanistic understanding. Specific topics discussed here include rare examples of catalyst control over the regio- and stereochemistry of polar monomer insertion by phosphine–sulfonato palladium complexes (Drent-type), rate acceleration of insertion polymerization by binuclear cooperativity using salicylaldiminato nickel complexes (Grubbs-type), and formation of linear copolymers of ethylene and polar vinyl monomers using a cationic palladium catalyst ligated by a bisphosphine monoxide (BPMO) that contrasts the typical polymer microstructures formed by other cationic group 10 catalysts ligated by an α-diimine (Brookhart-type).
Co-reporter:Dr. Ryo Shintani;Ryuhei Fujie;Dr. Momotaro Takeda;Dr. Kyoko Nozaki
Angewandte Chemie International Edition 2014 Volume 53( Issue 25) pp:6546-6549
Publication Date(Web):
DOI:10.1002/anie.201403726
Abstract
A potassium-bis(trimethylsilyl)amide-mediated cyclopropanation of allyl phosphates with silylboronates has been developed. Unlike the reported copper-catalyzed allylic substitution reactions, the nucleophile selectively attacks at the β-position of the allylic substrates under the present reaction conditions. The mechanism of this process has also been investigated, thus indicating the involvement of a silylpotassium species as the active nucleophilic component.
Co-reporter:Yusuke Masuda ; Maki Hasegawa ; Makoto Yamashita ; Kyoko Nozaki ; Naoki Ishida ;Masahiro Murakami
Journal of the American Chemical Society 2013 Volume 135(Issue 19) pp:7142-7145
Publication Date(Web):May 3, 2013
DOI:10.1021/ja403461f
The C–C bond of cyclobutanones undergoes oxidative addition to a T-shape rhodium(I) complex possessing a PBP pincer ligand at room temperature. The remarkable propensity of the rhodium complex for oxidative addition is attributed to the highly electron-donating nature of the boron ligand as well as the unsaturation on the rhodium center.
Co-reporter:Koji Nakano ; Kazuki Kobayashi ; Takahiro Ohkawara ; Hideyuki Imoto
Journal of the American Chemical Society 2013 Volume 135(Issue 23) pp:8456-8459
Publication Date(Web):May 28, 2013
DOI:10.1021/ja4028633
Iron–corrole complexes were found to copolymerize epoxides with CO2. The first iron-catalyzed propylene oxide/CO2 copolymerization has been accomplished. Moreover, the glycidyl phenyl ether (GPE)/CO2 copolymerization with this catalyst provided a crystalline material as a result of the isotactic poly(GPE) moiety.
Co-reporter:Shuhei Kusumoto ; Midori Akiyama
Journal of the American Chemical Society 2013 Volume 135(Issue 50) pp:18726-18729
Publication Date(Web):December 3, 2013
DOI:10.1021/ja409672w
Unprecedented direct acceptorless dehydrogenation of C–C single bonds adjacent to functional groups to form α,β-unsaturated compounds has been accomplished by using a new class of group 9 metal complexes. Metal–ligand cooperation operated by the hydroxycyclopentadienyl ligand was proposed to play a major role in the catalytic transformation.
Co-reporter:Hiromi Oyama, Koji Nakano, Takunori Harada, Reiko Kuroda, Masanobu Naito, Kazuyuki Nobusawa, and Kyoko Nozaki
Organic Letters 2013 Volume 15(Issue 9) pp:2104-2107
Publication Date(Web):April 15, 2013
DOI:10.1021/ol4005036
A facile synthetic route to dimethylsila[7]helicene by using a Lewis acid catalyzed double-cyclization reaction for construction of the twisted two phenanthrene moieties is described. Sila[7]helicene exhibited a high fluorescence quantum yield and a realatively large g value (dissymmetric factor) of circularly polarized luminencence (CPL) for small molecules.
Co-reporter:Koji Nakano, Ryuhei Fujie, Ryo Shintani and Kyoko Nozaki
Chemical Communications 2013 vol. 49(Issue 81) pp:9332-9334
Publication Date(Web):03 Sep 2013
DOI:10.1039/C3CC45622F
A simple and efficient catalyst removal system has been developed in the cobalt–salen-catalyzed copolymerization of propylene oxide with carbon dioxide. The present system requires no prior modification of the catalyst, and the removal is achieved by simple addition of myristic acid, followed by organic liquid–liquid phase separation.
Co-reporter:Shuhei Kusumoto;Dr. Shingo Ito ;Dr. Kyoko Nozaki
Asian Journal of Organic Chemistry 2013 Volume 2( Issue 11) pp:977-982
Publication Date(Web):
DOI:10.1002/ajoc.201300134
Abstract
The direct aldol polymerization of acetaldehyde, a new approach for the synthesis of poly(vinyl alcohol)- and poly(vinyl alcohol-co-ethylene)-type oligomers, cooperatively catalyzed by organocatalysts and Brønsted acids was investigated. Thus, we successfully obtained oligomers that contain a substantial amount of 1,3-hydroxy groups in the main chain. This conceptually new approach is an important step towards realizing the one-step synthesis of poly(vinyl alcohol)s from acetaldehyde with perfect atom economy.
Co-reporter:Ryo Shintani and Kyoko Nozaki
Organometallics 2013 Volume 32(Issue 8) pp:2459-2462
Publication Date(Web):April 3, 2013
DOI:10.1021/om400175h
A copper/N-heterocyclic carbene catalyzed hydroboration of carbon dioxide has been developed to give a formic acid derivative selectively under mild conditions. Investigations directed toward understanding the catalytic cycle of this process have been carried out, and the hydroboration product can be directly used as a formylation reagent for various amines.
Co-reporter:Brad P. Carrow
Journal of the American Chemical Society 2012 Volume 134(Issue 21) pp:8802-8805
Publication Date(Web):May 16, 2012
DOI:10.1021/ja303507t
The copolymerization of ethylene with polar vinyl monomers, such as vinyl acetate, acrylonitrile, vinyl ethers, and allyl monomers, was accomplished using cationic palladium complexes ligated by a bisphosphine monoxide (BPMO). The copolymers formed by these catalysts have highly linear microstructures and a random distribution of polar functional groups throughout the polymer chain. Our data demonstrate that cationic palladium complexes can exhibit good activity for polymerizations of polar monomers, in contrast to cationic α-diimine palladium complexes (Brookhart-type) that are not applicable to industrially relevant polar monomers beyond acrylates. Additionally, the studies reported here point out that phosphine-sulfonate ligated palladium complexes are no longer the singular family of catalysts that can promote the reaction of ethylene with many polar vinyl monomers to form linear functional polyolefins.
Co-reporter:Kohei Takahashi, Makoto Yamashita, and Kyoko Nozaki
Journal of the American Chemical Society 2012 Volume 134(Issue 45) pp:18746-18757
Publication Date(Web):November 1, 2012
DOI:10.1021/ja307998h
The catalyst system for tandem hydroformylation/hydrogenation of terminal alkenes to the corresponding homologated normal alcohol was developed. The reaction mechanism for the Rh/Ru dual catalyst was investigated by real-time IR monitoring experiments and 31P NMR spectroscopy, which proved the mutual orthogonality of Rh-catalyzed hydroformylation and Ru-catalyzed hydrogenation. Detailed investigation about Ru-catalyzed hydrogenation of undecanal under H2/CO pressure clarified different kinetics from the hydrogenation under H2 and gave a clue to design more active hydrogenation catalysts under H2/CO atmosphere. The solely Ru-catalyzed normal selective hydroformylation/hydrogenation is also reported.
Co-reporter:Yoshitaka Aramaki ; Hideki Omiya ; Makoto Yamashita ; Koji Nakabayashi ; Shin-ichi Ohkoshi
Journal of the American Chemical Society 2012 Volume 134(Issue 49) pp:19989-19992
Publication Date(Web):December 3, 2012
DOI:10.1021/ja3094372
The first isolation and full characterization of the stable, persistent diazaboracyclic neutral radical 3 is reported. Reduction of base-stabilized difluororoborane 2 provided radical 3 as a neutral molecule having a planar sp2 boron atom attached to one fluorine and two nitrogen atoms. ESR spectroscopy and DFT calculations indicated that the unpaired electron is delocalized over the six-membered ring. Because of an electronic transition related to the singly occupied molecular orbital, 3 has a characteristic red color, as UV–vis spectroscopy showed an absorption maximum at 498 nm. Although DFT calculations suggested that radical 3 has relatively low spin density on the boron atom in comparison with the nitrogen and carbon atoms in the six-membered ring, 3 reacted as a base-stabilized boryl radical when treated with benzoquinone or benzoyl peroxide.
Co-reporter:Akifumi Nakamura ; Takeharu Kageyama ; Hiroki Goto ; Brad P. Carrow ; Shingo Ito
Journal of the American Chemical Society 2012 Volume 134(Issue 30) pp:12366-12369
Publication Date(Web):July 23, 2012
DOI:10.1021/ja3044344
Utilization of palladium catalysts bearing a P-chiral phosphine–sulfonate ligand enabled asymmetric copolymerization of vinyl acetate with carbon monoxide. The obtained γ-polyketones have head-to-tail and isotactic polymer structures. The origin of the regio- and stereoregularities was elucidated by stoichiometric reactions of acylpalladium complexes with vinyl acetate. The present report for the first time demonstrates successful asymmetric coordination–insertion (co)polymerization of vinyl acetate.
Co-reporter:Shingo Ito, Masaki Noguchi and Kyoko Nozaki
Chemical Communications 2012 vol. 48(Issue 85) pp:10481-10483
Publication Date(Web):24 Aug 2012
DOI:10.1039/C2CC34980A
Inspired by the enzymatic ping-pong mechanism, we designed a novel “ping-pong polymerization”, which employs allylation and hydroformylation in an iterative and alternating manner. Thus, alternating and regioregular vinyl alcohol–vinyl monomer copolymers possessing multiple hydroxy groups in a periodical manner were successfully synthesized.
Co-reporter:Shingo Ito, Yusuke Ota and Kyoko Nozaki
Dalton Transactions 2012 vol. 41(Issue 45) pp:13807-13809
Publication Date(Web):11 Oct 2012
DOI:10.1039/C2DT31771K
Nickel(II) complexes bearing a phosphine–sulfonate ligand, [(R2PC6H4SO3)NiMe(2,6-lutidine)] (R = cyclohexyl, 2-MeOC6H4, and 2-[2′,6′-(MeO)2C6H3]C6H4, were synthesized and applied as catalysts for the cooligomerizations of ethylene and allyl monomers.
Co-reporter:Kohei Takahashi;Dr. Makoto Yamashita;Dr. Yoshiyuki Tanaka;Dr. Kyoko Nozaki
Angewandte Chemie 2012 Volume 124( Issue 18) pp:4459-4463
Publication Date(Web):
DOI:10.1002/ange.201108396
Co-reporter:Maki Hasegawa;Dr. Yasutomo Segawa;Dr. Makoto Yamashita;Dr. Kyoko Nozaki
Angewandte Chemie International Edition 2012 Volume 51( Issue 28) pp:6956-6960
Publication Date(Web):
DOI:10.1002/anie.201201916
Co-reporter:Yumi Hayashi, Shinji Wada, Makoto Yamashita, and Kyoko Nozaki
Organometallics 2012 Volume 31(Issue 3) pp:1073-1081
Publication Date(Web):February 1, 2012
DOI:10.1021/om201142s
The decomposition of arylpalladium hydroxide complexes gave the corresponding phenolic products, which may form through a C(sp2)–OH bond-forming reductive elimination either by treatment of arylpalladium halide complexes with cesium hydroxide or by heating arylpalladium hydroxide complexes. Treatment of a p-nitrophenylpalladium iodide complex possessing a tBuXPhos ligand with cesium hydroxide formed a mixture of p-nitrophenol and 4,4′-di-p-nitrobiphenyl. The reaction of a DtBPP-ligated p-nitrophenylpalladium iodide complex with cesium hydroxide gave a mixture of p-nitrophenylpalladium hydroxide complex, cesium p-nitrophenoxide, and DtBPP-bridged dinuclear Pd(0) complex. Gradual decomposition of p-nitrophenylpalladium hydroxide complex to cesium p-nitorophenoxide and a DtBPP-bridged dinuclear Pd(0) complex suggested that the C(sp2)–OH bond-forming reductive elimination took place. While an isolated p-tolylpalladium hydroxide complex gave no phenolic product upon heating, thermolysis of an isolated trifluoromethyl-substituted arylpalladium hydroxide complex enabled us to observe p-trifluoromethylphenol directly. Although an ester-substituted hydroxide complex did not form free p-methoxycarbonylphenol, its invisibility enabled us to handle the kinetic equation to estimate the rate constant k1 for reductive elimination. Polar solvents such as THF and DMF accelerated the reductive elimination with a large negative entropy of activation. Comparison of these results with those in the literature suggested direct C(sp2)–OH bond-forming reductive elimination with a concerted three-centered pathway. DFT calculations also predicted the hydrogen bond between the hydroxo ligand and the solvent molecule to stabilize the transition state.
Co-reporter:Kohei Takahashi;Dr. Makoto Yamashita;Dr. Yoshiyuki Tanaka;Dr. Kyoko Nozaki
Angewandte Chemie International Edition 2012 Volume 51( Issue 18) pp:4383-4387
Publication Date(Web):
DOI:10.1002/anie.201108396
Co-reporter:Shingo Ito ; Masafumi Kanazawa ; Kagehiro Munakata ; Jun-ichi Kuroda ; Yoshikuni Okumura
Journal of the American Chemical Society 2011 Volume 133(Issue 5) pp:1232-1235
Publication Date(Web):January 4, 2011
DOI:10.1021/ja1092216
Coordination−insertion copolymerization of allyl monomers with ethylene was developed by using a palladium/phosphine−sulfonate catalyst. A variety of allyl monomers, including allyl acetate, allyl alcohol, protected allylamines, and allyl halides, were copolymerized with ethylene to form highly linear copolymers that possess in-chain −CH2CH(CH2FG)− units.
Co-reporter:Akifumi Nakamura ; Kagehiro Munakata ; Shingo Ito ; Takuya Kochi ; Lung Wa Chung ; Keiji Morokuma
Journal of the American Chemical Society 2011 Volume 133(Issue 17) pp:6761-6779
Publication Date(Web):April 11, 2011
DOI:10.1021/ja2003268
Full details are provided for the alternating copolymerization of acrylic esters with carbon monoxide (CO) catalyzed by palladium species bearing a phosphine−sulfonate bidentate ligand. The copolymer of methyl acrylate (MA) and CO had complete regioregularity with stereocenters that slowly epimerize in the presence of methanol. In the presence of ethylene, terpolymers of MA/ethylene/CO were also prepared. The glass transition temperatures of the co- and terpolymers were higher than that of the ethylene/CO copolymer. Both experimental and theoretical investigations were performed to clarify the superior nature of the palladium phosphine−sulfonate system compared to an unsuccessful conventional palladium diphosphine system: (i) The reversible insertion of CO was directly observed with the isolated alkylpalladium complexes, [{o-((o-MeOC6H4)2P)C6H4SO3}PdCH(CO2Me)CH2COMe], whereas it was not observed with the corresponding complex bearing 1,2-bis(diphenylphosphino)ethane (DPPE). (ii) The transition state of the subsequent MA insertion, the rate-determining step of the catalytic cycle, was lower in energy in the phosphine−sulfonate system than in the DPPE system. This stabilization could be attributed to the less hindered sulfonate moiety as well as the stronger back-donation from palladium to the electron-deficient olefin, which is located trans to the sulfonate.
Co-reporter:Koji Nakano ; Kazuki Kobayashi
Journal of the American Chemical Society 2011 Volume 133(Issue 28) pp:10720-10723
Publication Date(Web):June 21, 2011
DOI:10.1021/ja203382q
New tetravalent metal complexes with a trianionic [ONNO]-tetradentate ligand and an ancillary chloride ligand were synthesized as catalysts for the copolymerization of epoxides with carbon dioxide (CO2). All of the titanium, zirconium, germanium, and tin complexes were found to copolymerize epoxides with CO2. In particular, the copolymerization of propylene oxide with CO2 gave the almost-completely alternating copolymers by using titanium or germanium complexes. These results are the first example of the copolymerization using tetravalent metal complexes as a main component of catalysts.
Co-reporter:Yumi Hayashi, Yasutomo Segawa, Makoto Yamashita and Kyoko Nozaki
Chemical Communications 2011 vol. 47(Issue 20) pp:5888-5890
Publication Date(Web):08 Apr 2011
DOI:10.1039/C1CC11334H
The present communication reports the chemistry of three linear triborane(5) compounds possessing bulky diamino substituents on the terminal boron atoms. Fluorotriborane 2 was synthesized by a reaction of boryllithium and BF3·OEt2. Halogen exchange reaction of 2 took place by a treatment with ClSiMe3 to give the corresponding chlorotriborane(5) 3. Addition of silver tetraarylborate to 3 in ether afforded a hydroxylated triborane(5) compound 5 probably via an unstable cationic boron intermediate 4.
Co-reporter:Makoto Yamashita, Yoshiki Moroe, Toshiyuki Yano, Kyoko Nozaki
Inorganica Chimica Acta 2011 Volume 369(Issue 1) pp:15-18
Publication Date(Web):15 April 2011
DOI:10.1016/j.ica.2010.08.034
A combination of neopentyl-substituted PNP–iridium complex 2 and NaH could catalyze dimerization of alkylamines to form dialkylamines with the highest activity ever reported. Primary and secondary alkylamines were applicable to the present catalytic reaction. Several mechanistic studies suggested a plausible catalytic cycle. The high activity of catalyst 2 may come from the role of neopentyl groups to make a space around the metal center.A combination of neopentyl-substituted PNP–iridium complex 2 and NaH could catalyze dimerization of alkylamines to form dialkylamine with the highest activity ever reported. The high activity of catalyst 2 may come from the role of neopentyl groups to make a space around the metal center.
Co-reporter:Ryo Tanaka, Makoto Yamashita, Lung Wa Chung, Keiji Morokuma, and Kyoko Nozaki
Organometallics 2011 Volume 30(Issue 24) pp:6742-6750
Publication Date(Web):November 30, 2011
DOI:10.1021/om2010172
The PNP-ligated iridium(III) trihydride complex 1 exhibited the highest catalytic activity for hydrogenation of carbon dioxide in aqueous KOH. The catalytic hydrogenation can be tuned to be a reversible process with the same catalyst at the expense of the activity, when triethanolamine was used as a base. Theoretical studies on the hydrogenation of carbon dioxide using DFT calculations suggested two competing reaction pathways: either the deprotonative dearomatization step or the hydrogenolysis step as the rate-determining step. The results nicely explain our experimental observations that the catalytic cycle is dependent on both the strength of the base and hydrogen pressure.
Co-reporter:Dr. Koji Nakano;Shinichi Hashimoto;Mitsuru Nakamura;Toshihiro Kamada ; Kyoko Nozaki
Angewandte Chemie International Edition 2011 Volume 50( Issue 21) pp:4868-4871
Publication Date(Web):
DOI:10.1002/anie.201007958
Co-reporter:Yuri Okuno;Dr. Makoto Yamashita;Dr. Kyoko Nozaki
Angewandte Chemie International Edition 2011 Volume 50( Issue 4) pp:920-923
Publication Date(Web):
DOI:10.1002/anie.201005667
Co-reporter:Masafumi Kanazawa, Shingo Ito, and Kyoko Nozaki
Organometallics 2011 Volume 30(Issue 21) pp:6049-6052
Publication Date(Web):October 10, 2011
DOI:10.1021/om2004207
Ethylene polymerization catalyzed by palladium(II)/phosphine–sulfonate complexes was performed in the presence and absence of CH3OH or CH3OD. The addition of the protic solvents resulted in a significant decrease of molecular weight and a slight increase of internal alkene chain ends, suggesting that β-H elimination from alkylpalladium intermediates was accelerated, which led to the following alkene dissociation from the Pd center or alkene isomerization. In the presence of CH3OD, linear polyethylenes possessing deuteriums in the main chain were obtained presumably via a β-H elimination, H/D exchange, and reinsertion sequence.
Co-reporter:Takeharu Kageyama;Dr. Shingo Ito ;Dr. Kyoko Nozaki
Chemistry – An Asian Journal 2011 Volume 6( Issue 2) pp:690-697
Publication Date(Web):
DOI:10.1002/asia.201000668
Abstract
Palladium/phosphine-sulfonate complexes were effective for the alternating copolymerization of vinylarenes with carbon monoxide (CO). The obtained copolymers had iso-enriched microstructures with ll selectivity of up to circa 60 %. The catalytic system was successfully applied to the terpolymerization of vinylarene and polar vinyl monomers with CO to produce novel terpolymers, which could not be obtained by using previously developed catalysts. NMR and DSC analyses suggested that vinylarene/CO units and polar vinyl monomer/CO units were randomly distributed in the terpolymer main chains.
Co-reporter:Dr. Koji Nakano;Shinichi Hashimoto;Mitsuru Nakamura;Toshihiro Kamada ; Kyoko Nozaki
Angewandte Chemie 2011 Volume 123( Issue 21) pp:4970-4973
Publication Date(Web):
DOI:10.1002/ange.201007958
Co-reporter:Kyoko Nozaki ; Shuhei Kusumoto ; Shusuke Noda ; Takuya Kochi ; Lung Wa Chung ;Keiji Morokuma
Journal of the American Chemical Society 2010 Volume 132(Issue 45) pp:16030-16042
Publication Date(Web):October 25, 2010
DOI:10.1021/ja104837h
Palladium-catalyzed coordination−insertion copolymerization of ethylene with acrylonitrile (AN) proceeded only by using phosphine−sulfonate (P−SO3) as a ligand among the neutral and anionic ligands we examined, those are phosphine−sulfonate (P−SO3), diphosphine (P−P), and imine−phenolate (N−O). In order to answer a question that is unique for P−SO3, theoretical and experimental studies were carried out for the three catalyst systems. By comparing P−SO3 and P−P, it was elucidated that (i) the π-acrylonitrile complex [(L−L′)PdPr(π-AN)] is less stable than the corresponding σ-complex [(L−L′)PdPr(σ-AN)] in both the phosphine−sulfonato complex (L−L′ = P−SO3) and the diphosphine complex (L−L′ = P−P) and (ii) the energetic difference between the π-complex and the σ-complex is smaller in the P−SO3 complexes than in the P−P complexes. Thus, the energies of the transition states for both AN insertion and its subsequent ethylene insertion relative to the most stable species [(L−L′)PdPr(σ-AN)] are lower for P−SO3 than for P−P. The results nicely explain the difference between these two types of ligands. That is, ethylene insertion subsequent to AN insertion was detected for P−SO3, while aggregate formation was reported for cationic [(L−L)Pd(CHCNCH2CH3)] complex. Aggregate formation with the cationic complex can be considered as a result of the retarded ethylene insertion to [(L−L)Pd(CHCNCH2CH3)]. In contrast, theoretical comparison between P−SO3 and N−O did not show a significant energetic difference in both AN insertion and its subsequent ethylene insertion, implying that ethylene/AN copolymerization might be possible. However, our experiment using [(N−O)PdMe(lutidine)] complex revealed that β-hydride elimination terminated the ethylene oligomerization and, more importantly, that the resulting Pd−H species lead to formation of free N−OH and Pd(0) particles. The β-hydride elimination process was further studied theoretically to clarify the difference between the two anionic ligands, P−SO3 and N−O.
Co-reporter:Kyoko Nozaki ; Yoshitaka Aramaki ; Makoto Yamashita ; Shau-Hua Ueng ; Max Malacria ; Emmanuel Lacôte ;Dennis P. Curran
Journal of the American Chemical Society 2010 Volume 132(Issue 33) pp:11449-11451
Publication Date(Web):August 2, 2010
DOI:10.1021/ja105277u
Reaction of lithium 1,3-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaborol-2-ide with borane·THF provides the first boryl-substituted borohydride: lithium [1,3-bis(2,6-diisopropylphenyl)-2,3-dihydro-1H-1,3,2-diazaborol-2-yl]trihydroborate. The compound is fully characterized by 11B, 1H, and 7Li NMR spectra and other means, and these data are compared to neutral and anionic benchmark compounds. The compound crystallizes as a dimer complexed to four THF molecules. The dimer lacks the bridging B−H bonds seen in neutral boranes and is instead held together by ionic Li---HB interactions. A preliminary scan of reactions with several iodides shows that the compound participates in an ionic reduction (with a primary-alkyl iodide), an organometallic reduction (Pd-catalyzed with an aryl iodide), and a radical reduction (AIBN-initiated with a sugar-derived iodide). Accordingly the new borylborohydride class may share properties of both traditional borohydrides and isoelectronic N-heterocyclic carbene boranes.
Co-reporter:Koji Nakano, Shinichi Hashimoto and Kyoko Nozaki
Chemical Science 2010 vol. 1(Issue 3) pp:369-373
Publication Date(Web):15 Jun 2010
DOI:10.1039/C0SC00220H
Dinuclear Co–salen complexes (R,R)-(S,S)-1–4 were synthesized and compared with their mononuclear counterpart rac-5 to suggest that a bimetallic mechanism is in charge for the alternating copolymerization of propylene oxide with CO2 in the absence of onium salt while a monometallic mechanism is more probable in its presence.
Co-reporter:Makoto Yamashita, Yoshitaka Aramaki and Kyoko Nozaki
New Journal of Chemistry 2010 vol. 34(Issue 8) pp:1774-1782
Publication Date(Web):09 Jul 2010
DOI:10.1039/C0NJ00363H
Lewis base-stabilized difluoroboranes 2, 4-pyr and 4-iPr, having an oxazoline- or amine-tethered amide ligand, were synthesized and fully characterized. The treatment of 2 with KC8 led to its complete consumption, and the rearranged product 5-H, probably originating from C–O bond cleavage and B–O bond formation, could be isolated as a major Dip-containing product in 18% yield. From deuterium labelling experiments and diffusion control reactions, the formation of 5-H could be explained by a radical mechanism. The reduction of 4-pyr and 4-iPr using one-electron reducing agents also gave the rearranged products 13-pyr and 13-iPr in 21 and 19% yields, respectively, via C–N bond cleavage and B–N bond formation. The mechanism for the formation of 13-pyr and 13-iPr is suggested to contain a benzylic radical intermediate.
Co-reporter:Kohei Takahashi;Makoto Yamashita Dr.;Takeo Ichihara;Koji Nakano Dr. Dr.
Angewandte Chemie 2010 Volume 122( Issue 26) pp:
Publication Date(Web):
DOI:10.1002/ange.201002254
Co-reporter:Shingo Ito
The Chemical Record 2010 Volume 10( Issue 5) pp:315-325
Publication Date(Web):
DOI:10.1002/tcr.201000032
Abstract
Random incorporation of polar functional groups into polyolefins and polyketones along with the precise control of incorporation ratios and polymer microstructures is one of the most significant challenges in polymer chemistry. For such a purpose, late-transition-metal complexes are often employed as a catalyst for the copolymerization of polar vinyl monomers, because of their high functional group compatibility. This acount describes our contribution to the development of coordination–insertion copolymerization of polar vinyl monomers by palladium catalysts. In particular, the use of palladium/phosphine–sulfonate catalysts enables to incorporate various polar vinyl monomers into polyolefins and polyketones. © 2010 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 10: 315–325; 2010: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.201000032
Co-reporter:Kohei Takahashi;Makoto Yamashita Dr.;Takeo Ichihara;Koji Nakano Dr. Dr.
Angewandte Chemie International Edition 2010 Volume 49( Issue 26) pp:
Publication Date(Web):
DOI:10.1002/anie.201002254
Co-reporter:Kohei Takahashi;Makoto Yamashita Dr.;Takeo Ichihara;Koji Nakano Dr. Dr.
Angewandte Chemie 2010 Volume 122( Issue 26) pp:4590-4592
Publication Date(Web):
DOI:10.1002/ange.201001327
Co-reporter:Kohei Takahashi;Makoto Yamashita Dr.;Takeo Ichihara;Koji Nakano Dr. Dr.
Angewandte Chemie International Edition 2010 Volume 49( Issue 26) pp:4488-4490
Publication Date(Web):
DOI:10.1002/anie.201001327
Co-reporter:Akifumi Nakamura, Shingo Ito and Kyoko Nozaki
Chemical Reviews 2009 Volume 109(Issue 11) pp:5215
Publication Date(Web):October 6, 2009
DOI:10.1021/cr900079r
Co-reporter:Yasutomo Segawa ; Makoto Yamashita
Journal of the American Chemical Society 2009 Volume 131(Issue 26) pp:9201-9203
Publication Date(Web):June 12, 2009
DOI:10.1021/ja9037092
We synthesized a PBP pincer ligand precursor 2 and demonstrated its complexation with iridium(I) to afford the coordinatively unsaturated [PBP](hydrido)chloroiridium complex 3 via B−H oxidative addition. The reaction of 3 with carbon monoxide produced [PBP](hydrido)chloro(carbonyl)iridium 7. The longer Ir−Cl bond length of 7 than that of 8 revealed a stronger σ-donor ability of the PBP ligand than that of PCP. Complex 3 was also converted to [PBP](ethylene)iridium(I) complex 9 by the reaction with LiTMP under an ethylene atmosphere.
Co-reporter:Shusuke Noda ; Akifumi Nakamura ; Takuya Kochi ; Lung Wa Chung ; Keiji Morokuma
Journal of the American Chemical Society 2009 Volume 131(Issue 39) pp:14088-14100
Publication Date(Web):September 11, 2009
DOI:10.1021/ja9047398
Linear polyethylene propagation starting from Pd phosphine−sulfonate complexes, Pd(CH3)(L)(Ar2PC6H4SO3) (L = 2,6-lutidine, Ar = o-MeOC6H4 (2a) and L = pyridine, Ar = Ph (2b)), was studied both experimentally and theoretically. Experimentally, highly linear polyethylene was obtained with Pd(CH3)(L)(Ar2PC6H4SO3) complexes 2a and 2b. Formation of a long alkyl-substituted palladium complex (3) was detected as a result of ethylene oligomerization on a palladium center starting from methylpalladium complex. Additionally, well-defined ethyl and propyl complexes (6Et and 6Pr) were synthesized as stable n-alkyl palladium complexes. In spite of the existence of β-hydrogens, the β-hydride elimination to give 1-alkenes was very slow or negligible in all cases. On the other hand, isomerization of 1-hexene in the presence of a methylpalladium/phosphine−sulfonate complex 2a indicated that this catalyst system actually undergoes β-hydride elimination and reinsertion to release internal alkenes. On the theoretical side, the relative energies were calculated for intermediates and transition states for chain-growth, chain-walking, and chain-transfer on the basis of the starting model complex Pd(n-C3H7)(pyridine)(o-Me2PC6H4SO3) (8). First, cis/trans isomerization process via the Berry’s pseudorotation was proposed for the Pd/phosphine−sulfonate system. The second oxygen atom of sulfonate group is involved in the isomerization process as the associative ligand, which is one of the most unique natures of the sulfonate group. Chain propagation was suggested to take place from the less stable alkylPd(ethylene) complex 10′ with the TS of 27.4/27.7 ((E+ZPC)/G) kcal/mol. Possible β-hydride elimination was suggested to occur under low concentration of ethylene: the highest-energy transition state to override for β-hydride elimination was either >37.4/25.3 kcal/mol (TS(9-12)) or 29.1/27.4 kcal/mol (TS(8′-9′) to reach 12′). The ethylene insertion to the iso-alkylpalladium species (14′) is allowed via a TS of 28.6/29.1 kcal/mol (TS(14′-15′)), slightly higher in energy than that for the normal-alkylpalladium species (TS(10′-11′)). Easy chain transfer was suggested to proceed from the more stable PdH(olefin) complex 12′ if β-hydride elimination to 12′ does take place. Thus, the production of linear polyethylene with high molecular weight under ethylene pressure suggests that the cis and trans PdH(alkene)(phosphine−sulfonate) complexes (12 and 12′) are merely accessible in the presence of excess amount of ethylene.
Co-reporter:Ryo Tanaka ; Makoto Yamashita
Journal of the American Chemical Society 2009 Volume 131(Issue 40) pp:14168-14169
Publication Date(Web):September 23, 2009
DOI:10.1021/ja903574e
Catalytic hydrogenation of carbon dioxide in aqueous potassium hydroxide was performed using a newly synthesized isopropyl-substituted PNP-pincer iridium trihydride complex as a catalyst. Potassium formate was obtained with turnover numbers up to 3 500 000 and a turnover frequency of 150 000 h−1, both of which are the highest values reported to date.
Co-reporter:Shingo Ito ; Kagehiro Munakata ; Akifumi Nakamura
Journal of the American Chemical Society 2009 Volume 131(Issue 41) pp:14606-14607
Publication Date(Web):September 28, 2009
DOI:10.1021/ja9050839
Coordination copolymerization of vinyl acetate (VAc) with ethylene, leading to linear copolymers that possess in-chain −CH2CH(OAc)− units, has been accomplished using novel palladium complexes bearing alkylphosphine−sulfonate ligands.
Co-reporter:Tomomi Terabayashi, Takashi Kajiwara, Makoto Yamashita and Kyoko Nozaki
Journal of the American Chemical Society 2009 131(40) pp: 14162-14163
Publication Date(Web):September 23, 2009
DOI:10.1021/ja905950g
Two group-4 boryl complexes, boryltitanium 2 and borylhafnium 3, were synthesized via nucleophilic borylation using boryllithium 1. Complexes 2 and 3 are the first examples of group-4 borylmetals. Theoretical calculations on model molecules 5 and 6 indicated that the boron−metal bond in both complexes has a covalent character. Complex 3 has activity for polymerization of ethylene or hex-1-ene.
Co-reporter:Koji Nakano, Shunsuke Kodama, Yessi Permana and Kyoko Nozaki
Chemical Communications 2009 (Issue 45) pp:6970-6972
Publication Date(Web):16 Oct 2009
DOI:10.1039/B912907C
Regioselective synthesis of halohydrin esters was achieved by (1) the reaction of acyl halides with epoxides and (2) the rhodium-catalyzed three-component coupling reaction of alkyl halides, carbon monoxide, and epoxides.
Co-reporter:Ken Sakakibara and Kyoko Nozaki
Organic & Biomolecular Chemistry 2009 vol. 7(Issue 3) pp:502-507
Publication Date(Web):2008/11/25
DOI:10.1039/B814413C
The scope and limitation of the ring-opening reaction of sulfonyl-activated aziridines using lithiated dithianes was investigated. Nucleophilic attack of lithiated dithianes on aziridines containing tert-butylsulfonyl (Bus) and 2-(trimethylsilyl)ethylsulfonyl (SES) demonstrated efficient ring cleavage to yield β-amino carbonyl equivalents, γ-lactam and syn- and anti-1,5-aminoalcohols. The first example of a ring-opening reaction of di-substituted aziridine using dithiane is also reported. Finally, the Bus and SES-possessing dithianes obtained were deprotected to demonstrate their synthetic usefulness.
Co-reporter:Koji Nakano, Motonobu Takahashi, Keiko Kawaguchi, Kyoko Nozaki
Synthetic Metals 2009 Volume 159(9–10) pp:939-942
Publication Date(Web):May 2009
DOI:10.1016/j.synthmet.2009.02.001
New π-conjugated polymers with dibenzo[d,d′]benzo[1,2-b:4,5-b′]difuran (DBBDF) unit in the main chains were synthesized. Copolymerization of 6,12-diiodo-DBBDF with p-diethynylbenzene or 2,7-diethynylfluorene derivative under Sonogashira–Hagiwara coupling-reaction condition gave the corresponding copolymer. The resulting copolymers were soluble in organic solvents such as tetrahydrofuran and chloroform. In UV–vis absorption spectra, both copolymers showed red-shifted spectra compared to their monomer units. In the chloroform solutions, the copolymer with DBBDF and p-diethynylbenzene units showed yellowish-green emission, while the copolymer with DBBDF and 2,7-diethynylfluorene units did greenish-blue emission.
Co-reporter:Yusuke Nagai, Takuya Kochi and Kyoko Nozaki
Organometallics 2009 Volume 28(Issue 20) pp:6131-6134
Publication Date(Web):September 29, 2009
DOI:10.1021/om9004252
Syntheses of new NHC-sulfonate palladium complexes [N-(2,6-diisopropylphenyl)-N′-sulfomethylNHC]Pd(2,6-lutidine) (7a) and [N-(2,6-diisopropylphenyl)-N′-sulfomethylNHC]Pd(PPh3) (7b) are reported. The structure of complexes 7a and 7b were determined by single-crystal X-ray analysis as the first examples of bidentate coordination of imidazolium-sulfonate to a metal center.
Co-reporter:Koji Nakano, Mitsuru Nakamura and Kyoko Nozaki
Macromolecules 2009 Volume 42(Issue 18) pp:6972-6980
Publication Date(Web):August 21, 2009
DOI:10.1021/ma9012626
Copolymerization of cyclohexene oxide with carbon dioxide was investigated by using chromium complexes with salalen ligands which are reduced analogues of salen ones (salen-H2 = N,N′-disalicylidene-1,2-ethylenediamine). Although the use of (salalen)CrCl complexes alone without additives was not effective for the copolymerization, a mixture of (salalen)CrCl complexes and onium salts catalyzed the copolymerization with relatively high catalytic activity. Particularly, the present catalyst system showed the highest catalytic activity under atmospheric pressure of CO2 among those ever reported. In general, the obtained copolymers consisted of almost perfectly alternating structure. Structural analysis of the copolymers by MALDI-TOF mass spectrometry revealed that chloride initiated the copolymerization. In addition, concomitant water was found to work as a chain transfer reagent and a bifunctional initiator.
Co-reporter:Shusuke Noda, Takuya Kochi and Kyoko Nozaki
Organometallics 2009 Volume 28(Issue 2) pp:656-658
Publication Date(Web):December 18, 2008
DOI:10.1021/om800781b
Phosphine sulfonate nickel complexes [(o-Ar2PC6H4SO3)Ni(allyl)] (Ar = Ph, o-MeOC6H4) are prepared and used as catalysts for ethylene polymerization. The products were low molecular weight polyethylenes possessing only methyl branches. The activity for ethylene polymerization with the phenyl-substituted complex was comparable to that of o-methoxyphenyl-substituted complex in the absence of activator. Comparison with the corresponding allylpalladium complex revealed that the nickel catalysts produced polyethylenes with lower molecular weight and more branches than the palladium catalyst.
Co-reporter:Yasutomo Segawa, Makoto Yamashita and Kyoko Nozaki
Organometallics 2009 Volume 28(Issue 21) pp:6234-6242
Publication Date(Web):October 8, 2009
DOI:10.1021/om9006455
Two hydroborane precursors (1b,c) for PBP pincer ligands bearing phenyl or cyclohexyl groups on phosphorus atoms were synthesized, and their complexation reactions with iridium were investigated. Reaction of hydroborane 1b, bearing phenyl groups, with Ir[P(p-tol)3]2(CO)Cl afforded an 18-electron complex, [PhPBP]Ir(H)(CO)Cl (3b), but reactions with other iridium(I) sources gave complicated mixtures. The characteristic IR peaks in 3b compared with the previously reported tBu-PBP derivative 3a were discussed on the basis of theoretical calculations. Complexation of cyclohexyl-substituted hydroborane 1c with [Ir(C2H4)2Cl]2 afforded a 16-electron complex, [CyPBP]Ir(H)Cl (2c). X-ray structure and computational studies on 2c revealed that the hydride ligand is close [B−H = 1.90(5) Å] to the boron atom. Reaction of 2c with LiTMP (TMP = 2,2,6,6-tetramethylpipyridide) under ethylene atmosphere gave monovalent iridium complex [CyPBP]Ir(C2H4) (4c) by a similar procedure to the previously reported [tBuPBP] system. Exposure of a CD2Cl2 solution of 2c to ethylene without additional base resulted in a quantitative formation of the intermediate [CyPBP]Ir(H)(C2H4)Cl (8c), as was characterized by NMR spectroscopy. In contrast, no spectral change was observed in the same procedure using [tBuPBP]Ir(H)Cl (2a) probably due to a difference in steric bulk. The observation of 8c is a rare example of a spectroscopically identified boryl(hydrido)olefin metal complex.
Co-reporter:Ikuko Takamiya, Makoto Yamashita and Kyoko Nozaki
Organometallics 2008 Volume 27(Issue 20) pp:5347-5352
Publication Date(Web):September 26, 2008
DOI:10.1021/om800566j
Exo- and endo-isomers of an ester-substituted norbornene derivative [5-norbornene carboxylic acid methyl ester (NBE)] are compared in the addition polymerization using tBu3P-ligated palladium complex 1. The polymerization rate of endo-NBE is slower than that of the corresponding exo-NBE. Each of exo- and endo-NBE inserted complexes was synthesized and the insertion rate constant was determined for exo-NBE and endo-NBE. These experiments revealed that the consecutive exo-NBE insertion was faster than the consecutive endo-NBE insertion by 2-fold. On the other hand, in polymerization of an exo-NBE/endo-NBE (1:1) mixture, consumption rates of exo-NBE and endo-NBE were almost equal and the production rate of the poly-NBE from this mixture was almost the same as that of homopolymerization of exo-NBE.
Co-reporter:Takashi Kajiwara Dr.;Tomomi Terabayashi;Makoto Yamashita Dr. Dr.
Angewandte Chemie International Edition 2008 Volume 47( Issue 35) pp:6606-6610
Publication Date(Web):
DOI:10.1002/anie.200801728
Co-reporter:Yessi Permana;Koji Nakano Dr.;Makoto Yamashita Dr.;Daisuke Watanabe Dr.
Chemistry – An Asian Journal 2008 Volume 3( Issue 4) pp:710-718
Publication Date(Web):
DOI:10.1002/asia.200700339
Abstract
Four acetyl cobalt complexes, [AcCo(CO)3P(p-tolyl)3] (1; p-tolyl=4-Me-C6H4), [AcCo(CO)3P(OPh)3] (2), [AcCo(CO)3P(NMe2)3] (3), and [AcCo(CO)2(dppp)] (4; dppp=1,3-bis(diphenylphosphanyl)propane), were synthesized, characterized, and examined as catalysts for the unprecedented carbonylative polymerization of oxetanes. Copolymers containing ester (4-hydroxyalkanoate) and/or ether units were obtained with complexes 1 and 2, but not with complexes 3 and 4 either in the presence or absence of additional phosphorus ligands. The ester unit/ether unit ratio varied in the range 21:79–63:37, and the highest ester/ether ratio of 63:37 was achieved by using complex 1 in the presence of a further 5 equivalents of P(OPh)3. Although direct carbonylative polymerization is possible, preformation and ring opening of the γ-lactone is also suggested as an alternative pathway.
Metoda sintesa baru bagi poliester rantai lurus yang ramah lingkungan ditemukan melalui polimerisasi oksetan dan gas karbon monoksida menggunakan katalis logam kobal 1 dan 2. Penggunaan katalis kobal 1 yang ditambahkan ligan P(OPh)3 sebanyak lima ekivalen mampu menghasilkan polimer dengan unit ester sampai dengan 63 %.
Co-reporter:Takeo Ichihara;Koji Nakano Dr.;Masaya Katayama Dr.
Chemistry – An Asian Journal 2008 Volume 3( Issue 8-9) pp:1722-1728
Publication Date(Web):
DOI:10.1002/asia.200800163
Abstract
A series of 2,2′-bis[(dialkylphosphino)methyl]biphenyls (alkyl-BISBIs) were synthesized and applied to the tandem hydroformylation–hydrogenation of 1-decene. The alkyl-BISBI ligands with “small” primary alkyl groups such as methyl or n-hexyl groups on the phosphorus atoms provided 1-alkanols selectively, whereas those with larger alkyl groups such as isopropyl or neopentyl groups showed much lower conversion from alkanals to alkanols. Observation of rhodium complexes of the BISBI-type ligands under H2/CO atmosphere revealed that the presence of a stable [RhH(CO)2(ligand)] species seems to be less favorable for the second step, the hydrogenation of aldehydes.
Co-reporter:Ikuko Takamiya;Makoto Yamashita;Eisuke Murotani;Yoshitomi Morizawa
Journal of Polymer Science Part A: Polymer Chemistry 2008 Volume 46( Issue 15) pp:5133-5141
Publication Date(Web):
DOI:10.1002/pola.22841
Abstract
The combination of palladium complex (tBu3P)Pd(Me)Cl (1) and NaB[3,5-(CF3)2C6H3]4 (NaBAr4) catalyzed homopolymerization of a novel monomer, norbornene (NB) with a pendent 2-fluorosulfonyltetrafluoroethoxymethyl chain (NBSF). Catalytic activities of 1/NaBAr4 were higher than those of previously reported palladium or nickel catalysts, probably, because the palladium center with electron donative tBu3P ligand was barely poisoned by the sulfonyl fluoride coordination. Thus, 1/NaBAr4 is the current best catalyst system for NBSF polymerization. The catalyst system also gave copolymers of NB with NBSF. The obtained copolymers have high sulfonyl-fluoride incorporation and a narrow molecular weight distribution. Present catalyst system could control incorporation ratio of NBSF by changing a feed monomer ratio with slow addition of NB solution. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5133–5141, 2008
Co-reporter:Yasutomo Segawa;Makoto Yamashita Dr. Dr.
Angewandte Chemie 2007 Volume 119(Issue 35) pp:
Publication Date(Web):30 JUL 2007
DOI:10.1002/ange.200702369
Nucleophile Borylierung: Die Transmetallierung von Boryllithium-Verbindungen mit Gruppe-11-Übergangsmetallchloriden ergibt die entsprechenden Borylkomplexe (siehe Schema). Borylsilber- und Borylgoldkomplexe mit Drei-Zentren-zwei-Elektronen-M-B-Bindungen wurden erstmals vollständig charakterisiert. Dabei ergab sich, dass der Borylligand einer der stärksten bekannten σ-Donorliganden ist.
Co-reporter:Yasutomo Segawa;Makoto Yamashita Dr. Dr.
Angewandte Chemie International Edition 2007 Volume 46(Issue 35) pp:
Publication Date(Web):30 JUL 2007
DOI:10.1002/anie.200702369
Nucleophilic borylation: Transmetalation from boryllithium compounds to Group 11 transition-metal chlorides gives the corresponding boryl complexes (see scheme). Borylsilver and borylgold complexes that have three-center-two-electron MB bonds are fully characterized for the first time. The NMR spectra and solid-state structures of the resulting boryl complexes reveal that the boryl ligand is one of the strongest known σ-donor ligands.
Co-reporter:Yasutomo Segawa;Makoto Yamashita
Science 2006 Vol 314(5796) pp:113-115
Publication Date(Web):06 Oct 2006
DOI:10.1126/science.1131914
Abstract
Nucleophilic, anionic boryl compounds are long-sought but elusive species. We report that reductive cleavage of the boron-bromine bond in N,N′-bis(2,6-diisopropylphenyl)-2-bromo-2,3-dihydro-1H-1,3,2-diazaborole by lithium naphthalenide afforded the corresponding boryllithium, which is isoelectronic with an N-heterocyclic carbene. The structure of the boryllithium determined by x-ray crystallography was consistent with sp2 boron hybridization and revealed a boron-lithium bond length of 2.291 ± 0.006 angstroms. The structural similarity between this compound and the calculated free boryl anion suggests that the boron atom has an anionic charge. The 11B nuclear magnetic resonance spectrum also supports the boryl anion character. Moreover, the compound behaves as an efficient base and nucleophile in its reactions with electrophiles such as water, methyl trifluoromethanesulfonate, 1-chlorobutane, and benzaldehyde.
Co-reporter:Ken Sakakibara, Koji Nakano and Kyoko Nozaki
Chemical Communications 2006 (Issue 31) pp:3334-3336
Publication Date(Web):30 Jun 2006
DOI:10.1039/B606693C
Highly fluorinated epoxides were polymerized under mild conditions regioregularly, which gave easy access to isotactic polymers by using optically pure epoxides.
Co-reporter:Takuya Kochi, Kenji Yoshimura and Kyoko Nozaki
Dalton Transactions 2006 (Issue 1) pp:25-27
Publication Date(Web):14 Nov 2005
DOI:10.1039/B512452M
Reaction of diarylphosphinobenzene-2-sulfonic acids with tertially amines, followed by addition of [PdMeCl(cod)], provided anionic methylpalladium(II) complexes with bidentate phosphine–sulfonate ligands, which show high activity for copolymerization of ethylene with methyl acrylate.
Co-reporter:Ryo Tanaka;Koji Nakano
Helvetica Chimica Acta 2006 Volume 89(Issue 8) pp:1681-1686
Publication Date(Web):30 AUG 2006
DOI:10.1002/hlca.200690166
The asymmetric hydroformylation of 2- and 3-vinylfurans (2a and 2b, resp.) was investigated by using [Rh{(R,S)-binaphos}] complexes as catalysts ((R,S)-binaphos = (11bS)-4-{[1R)-2′-phosphino[1,1′-binaphthalen]-2-yl]oxy}dinaphtho[2,1-d:1′,2′-f][1,3,2]dioxaphosphepin; 1). Hydroformylation of 2 gave isoaldehydes 3 in high regio- and enantioselectivities (Scheme 2 and Table). Reduction of the aldehydes 3 with NaBH4 successfully afforded the corresponding alcohols 5 without loss of enantiomeric purity (Scheme 3).
Co-reporter:Koji Nakano Dr.;Toshihiro Kamada Dr.
Angewandte Chemie International Edition 2006 Volume 45(Issue 43) pp:
Publication Date(Web):6 OCT 2006
DOI:10.1002/anie.200603132
Sidestepping a cyclic side product: Copolymerization of terminal epoxides with CO2 was investigated by using a cobalt(III) complex bearing a piperidinium end-capping arm and a piperidinyl arm (see scheme; DME=1,2-dimethoxyethane). The catalyst system can selectively produce copolymers without contaminant formation of cyclic carbonates even at high conversion of the epoxide (>99 %).
Co-reporter:Shinsuke Kinoshita, Fumitoshi Shibahara and Kyoko Nozaki
Green Chemistry 2005 vol. 7(Issue 5) pp:256-258
Publication Date(Web):21 Mar 2005
DOI:10.1039/B418264B
The difference between two methods for the synthesis of polystyrene-supported (R,S)-BINAPHOS-Rh(I) complex, namely (1) copolymerization of the monomeric ligand with divinylbenzene–ethylstyrene and then Rh-complex formation with the polymer-supported ligand, and (2) Rh-complex formation with the monomeric ligand and then immobilization of the Rh complex to polystyrene by copolymerization with divinylbenzene–ethylstyrene, is investigated by comparison of their catalytic performance, by surface analysis and particle-size measurement.
Co-reporter:Koji Nakano, Tamejiro Hiyama and Kyoko Nozaki
Chemical Communications 2005 (Issue 14) pp:1871-1873
Publication Date(Web):17 Feb 2005
DOI:10.1039/B417973K
Asymmetric amplification in the copolymerization of cyclohexene oxide and carbon dioxide was demonstrated using chiral zinc complexes, prepared from diethylzinc, diphenyl(pyrrolidin-2-yl)methanol, and ethanol.
Co-reporter:Kyoko Nozaki
The Chemical Record 2005 Volume 5(Issue 6) pp:
Publication Date(Web):8 NOV 2005
DOI:10.1002/tcr.20046
Characteristic features of unsymmetric bidentate ligands, in which the two coordination atoms are not equivalent, are reviewed with a focus on their use in metal-catalyzed olefin carbonylations. High enantioselectivity for a variety of substrates was achieved using ligand 9 in Rh-catalyzed hydroformylation. Unsymmetric ligand 21e shows high productivity accompanied by high regio- and enantioselectivities in the Pd-catalyzed alternating copolymerization of 1-alkene with CO. The advantages of electronic unsymmetry are demonstrated especially in the spectroscopic observation of single steps involved in catalytic cycles. © 2005 The Japan Chemical Journal Forum and Wiley Periodicals, Inc. Chem Rec 5: 376–384; 2005: Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/tcr.20046
Co-reporter:Koji Nakano Dr.;Yuko Hidehira;Keita Takahashi;Tamejiro Hiyama Dr. Dr.
Angewandte Chemie 2005 Volume 117(Issue 43) pp:
Publication Date(Web):6 OCT 2005
DOI:10.1002/ange.200502855
Enantiomerenangereicherte Aza- und Oxa[7]helicene wurden ausgehend von einem enantiomerenreinen Biphenanthryldiol hoch stereoselektiv synthetisiert. Ein N-Phenylaza[7]helicen ist durch palladiumkatalysierte doppelte N-Arylierung von Anilin mit den entsprechenden Disulfonaten zugänglich (siehe Schema, rechts), ein Oxa[7]helicen entsteht bei der palladiumkatalysierten intramolekularen O-Arylierung der Monosulfonate (links).
Co-reporter:Koji Nakano, Yuko Hidehira, Keita Takahashi, Tamejiro Hiyama,Kyoko Nozaki
Angewandte Chemie International Edition 2005 44(43) pp:7136-7138
Publication Date(Web):
DOI:10.1002/anie.200502855
Co-reporter:Kyoko Nozaki
Journal of Polymer Science Part A: Polymer Chemistry 2004 Volume 42(Issue 2) pp:215-221
Publication Date(Web):3 DEC 2003
DOI:10.1002/pola.11025
Two examples of asymmetric alternating copolymerization, (1) the alternating copolymerization of α-olefins (monosubstituted ethenes) with carbon monoxide and (2) the alternating copolymerization of meso-epoxide with carbon dioxide, are described, and the meaning of chirality in polymer synthesis is emphasized. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 215–221, 2004
Co-reporter:Koji Nakano;Kondo Fumitaka
Journal of Polymer Science Part A: Polymer Chemistry 2004 Volume 42(Issue 18) pp:4666-4670
Publication Date(Web):12 AUG 2004
DOI:10.1002/pola.20383
The alternating copolymerization of propylene oxide and carbon monoxide was investigated with cobalt complexes. The NaCo(CO)4/amine catalyst system selectively yielded oligo(3-hydroxybutyrate)s bearing a polymerizable crotonate end group, whereas the use of Co2(CO)8 as a cobalt source resulted in a smaller concentration of the crotonate end group and a high degree of polymerization. The high selectivity for the oligoesters with the crotonate end group with the NaCo(CO)4/amine system was attributed to its more basic reaction condition. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 4666–4670, 2004
Co-reporter:Kyoko Nozaki Dr.;Keita Takahashi;Koji Nakano;Tamejiro Hiyama Dr.;Hong-Zhi Tang Dr.;Michiya Fujiki Dr.;Shigehiro Yamaguchi Dr.;Kohei Tamao Dr.
Angewandte Chemie 2003 Volume 115(Issue 18) pp:
Publication Date(Web):8 MAY 2003
DOI:10.1002/ange.200250648
Leistungsfähige Methode: Eine Reihe sterisch überfrachteter Carbazole wurde ausgehend von Anilin- und Biphenylderivaten hergestellt (siehe Schema). Werden 2,2′-Diaminobiphenyle als Anilinsubstrate eingesetzt, gelingt die Synthese von 2,2′-Dicarbazolyl-1,1′-biarylen, die Excimer- (oder Exciplex-)emission mit starker Solvensabhängigkeit zeigen.
Co-reporter:Kyoko Nozaki Dr.;Keita Takahashi;Koji Nakano;Tamejiro Hiyama Dr.;Hong-Zhi Tang Dr.;Michiya Fujiki Dr.;Shigehiro Yamaguchi Dr.;Kohei Tamao Dr.
Angewandte Chemie International Edition 2003 Volume 42(Issue 18) pp:
Publication Date(Web):8 MAY 2003
DOI:10.1002/anie.200250648
A powerful method: A variety of sterically crowded, substituted carbazoles have been prepared from anilines and biphenyl compounds (see scheme). The method enabled the preparation of 2,2′-dicarbazolyl-1,1′-biaryl compounds, which show excimer (or exciplex) emissions with significant solvent dependency.
Co-reporter:Yasutoyo Kawashima;Tamejiro Hiyama;Masafumi Yoshio;Kiyoshi Kanie;Takashi Kato
Journal of Polymer Science Part A: Polymer Chemistry 2003 Volume 41(Issue 22) pp:3556-3563
Publication Date(Web):8 OCT 2003
DOI:10.1002/pola.10843
Isotactic and syndiotactic polyketones were synthesized by the alternating copolymerizations of a mesogenic vinylarene, 4-cyano-4′-[8-(4-vinylphenyl)octyl-1-oxy]biphenyl, with carbon monoxide, and this revealed the influence of backbone tacticity on their thermal properties. The isotactic polyketone was an amorphous polymer that did not show any mesophase, whereas the syndiotactic polyketone exhibited liquid crystallinity. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3556–3563, 2003
Co-reporter:Fumitoshi Shibahara, Kyoko Nozaki, Takeshi Matsuo, Tamejiro Hiyama
Bioorganic & Medicinal Chemistry Letters 2002 Volume 12(Issue 14) pp:1825-1827
Publication Date(Web):22 July 2002
DOI:10.1016/S0960-894X(02)00267-6
A new class of polymer-supported (R,S)-BINAPHOS 1e in which the parent BINAPHOS has two alkoxy-substituents at the 3-positions of the phenyls, has been synthesised. Using its Rh(I) complex, asymmetric hydroformylation of olefins proceeded with higher enantioselectivity in some cases compared to the conventional polymer-supported 1c.A new class of polymer-supported (R,S)-BINAPHOS 1e has been synthesised and asymmetric hydroformylation of olefins using its Rh(I) complex was examined.
Co-reporter:Yusuke Mitsushige, Brad P. Carrow, Shingo Ito and Kyoko Nozaki
Chemical Science (2010-Present) 2016 - vol. 7(Issue 1) pp:
Publication Date(Web):
DOI:10.1039/C5SC03361F
Co-reporter:Takafumi Kawakami, Shingo Ito and Kyoko Nozaki
Dalton Transactions 2015 - vol. 44(Issue 47) pp:NaN20752-20752
Publication Date(Web):2015/11/16
DOI:10.1039/C5DT03551A
A series of iron complexes bearing a bis(imino)pyridine ligand were synthesised and examined as precatalysts for homopolymerisation of propylene. The alkyl substituents attached to the aryl group on the imine nitrogen atoms significantly affected the catalytic activity and molecular weight of the obtained polypropylenes. Copolymerisation of propylene and various allyl comonomers catalysed by iron/bis(imino)pyridine was also investigated.
Co-reporter:Yumi Hayashi, Yasutomo Segawa, Makoto Yamashita and Kyoko Nozaki
Chemical Communications 2011 - vol. 47(Issue 20) pp:NaN5890-5890
Publication Date(Web):2011/04/08
DOI:10.1039/C1CC11334H
The present communication reports the chemistry of three linear triborane(5) compounds possessing bulky diamino substituents on the terminal boron atoms. Fluorotriborane 2 was synthesized by a reaction of boryllithium and BF3·OEt2. Halogen exchange reaction of 2 took place by a treatment with ClSiMe3 to give the corresponding chlorotriborane(5) 3. Addition of silver tetraarylborate to 3 in ether afforded a hydroxylated triborane(5) compound 5 probably via an unstable cationic boron intermediate 4.
Co-reporter:Shingo Ito, Masaki Noguchi and Kyoko Nozaki
Chemical Communications 2012 - vol. 48(Issue 85) pp:NaN10483-10483
Publication Date(Web):2012/08/24
DOI:10.1039/C2CC34980A
Inspired by the enzymatic ping-pong mechanism, we designed a novel “ping-pong polymerization”, which employs allylation and hydroformylation in an iterative and alternating manner. Thus, alternating and regioregular vinyl alcohol–vinyl monomer copolymers possessing multiple hydroxy groups in a periodical manner were successfully synthesized.
Co-reporter:Shingo Ito, Yusuke Ota and Kyoko Nozaki
Dalton Transactions 2012 - vol. 41(Issue 45) pp:NaN13809-13809
Publication Date(Web):2012/10/11
DOI:10.1039/C2DT31771K
Nickel(II) complexes bearing a phosphine–sulfonate ligand, [(R2PC6H4SO3)NiMe(2,6-lutidine)] (R = cyclohexyl, 2-MeOC6H4, and 2-[2′,6′-(MeO)2C6H3]C6H4, were synthesized and applied as catalysts for the cooligomerizations of ethylene and allyl monomers.
Co-reporter:Keisuke Takahashi, Shingo Ito, Ryo Shintani and Kyoko Nozaki
Chemical Science (2010-Present) 2017 - vol. 8(Issue 1) pp:NaN107-107
Publication Date(Web):2016/11/14
DOI:10.1039/C6SC04560J
A rhodium-catalysed stitching reaction between 2-(silylethynyl)arylboronates and 2-(silylethynyl)aryl bromides has been developed for the synthesis of unsymmetric dibenzo[a,e]pentalenes. The introduction of appropriately sized silyl groups on the starting substrates led to a high crossover selectivity without using an excess amount of either substrate. The present stitching reaction could produce a variety of unsymmetric dibenzo[a,e]pentalene derivatives, including those with electronically different substituents on the fused benzene rings as well as heteroarene fused compounds. Desilylative halogenation was also demonstrated to synthesise the corresponding halogenated dibenzo[a,e]pentalenes, which can be used as building blocks for further chemical transformations.
Co-reporter:Ken Sakakibara and Kyoko Nozaki
Organic & Biomolecular Chemistry 2009 - vol. 7(Issue 3) pp:NaN507-507
Publication Date(Web):2008/11/25
DOI:10.1039/B814413C
The scope and limitation of the ring-opening reaction of sulfonyl-activated aziridines using lithiated dithianes was investigated. Nucleophilic attack of lithiated dithianes on aziridines containing tert-butylsulfonyl (Bus) and 2-(trimethylsilyl)ethylsulfonyl (SES) demonstrated efficient ring cleavage to yield β-amino carbonyl equivalents, γ-lactam and syn- and anti-1,5-aminoalcohols. The first example of a ring-opening reaction of di-substituted aziridine using dithiane is also reported. Finally, the Bus and SES-possessing dithianes obtained were deprotected to demonstrate their synthetic usefulness.
Co-reporter:Koji Nakano, Shinichi Hashimoto and Kyoko Nozaki
Chemical Science (2010-Present) 2010 - vol. 1(Issue 3) pp:NaN373-373
Publication Date(Web):2010/06/15
DOI:10.1039/C0SC00220H
Dinuclear Co–salen complexes (R,R)-(S,S)-1–4 were synthesized and compared with their mononuclear counterpart rac-5 to suggest that a bimetallic mechanism is in charge for the alternating copolymerization of propylene oxide with CO2 in the absence of onium salt while a monometallic mechanism is more probable in its presence.
Co-reporter:Ryo Shintani, Ryo Takano and Kyoko Nozaki
Chemical Science (2010-Present) 2016 - vol. 7(Issue 2) pp:
Publication Date(Web):
DOI:10.1039/C5SC03767K
Co-reporter:Koji Nakano, Ryuhei Fujie, Ryo Shintani and Kyoko Nozaki
Chemical Communications 2013 - vol. 49(Issue 81) pp:NaN9334-9334
Publication Date(Web):2013/09/03
DOI:10.1039/C3CC45622F
A simple and efficient catalyst removal system has been developed in the cobalt–salen-catalyzed copolymerization of propylene oxide with carbon dioxide. The present system requires no prior modification of the catalyst, and the removal is achieved by simple addition of myristic acid, followed by organic liquid–liquid phase separation.
Co-reporter:Koji Nakano, Shunsuke Kodama, Yessi Permana and Kyoko Nozaki
Chemical Communications 2009(Issue 45) pp:NaN6972-6972
Publication Date(Web):2009/10/16
DOI:10.1039/B912907C
Regioselective synthesis of halohydrin esters was achieved by (1) the reaction of acyl halides with epoxides and (2) the rhodium-catalyzed three-component coupling reaction of alkyl halides, carbon monoxide, and epoxides.
Co-reporter:Ryo Shintani, Hiroki Kurata and Kyoko Nozaki
Chemical Communications 2015 - vol. 51(Issue 57) pp:NaN11381-11381
Publication Date(Web):2015/06/04
DOI:10.1039/C5CC04172D
Rhodium-catalyzed intramolecular alkynylsilylation of alkynes is described. The reaction proceeds through syn-insertion by a cationic rhodium/triarylphosphine catalyst, representing the first alkynylsilylation of alkynes via the cleavage of a C(sp)–Si bond by transition-metal catalysis. A highly enantioselective variant is also described for the creation of a silicon stereogenic center.
Co-reporter:S. Ito, Y. Tokimaru and K. Nozaki
Chemical Communications 2015 - vol. 51(Issue 1) pp:NaN224-224
Publication Date(Web):2014/11/04
DOI:10.1039/C4CC06643J
The synthesis of the novel azomethine ylide, isoquinolino[4,3,2-de]phenanthridine, and its use in 1,3-dipolar cycloaddition with various alkenes and alkynes to form the corresponding fused pyrrolidines and pyrroles is reported.
![2,6-Bis[1-(2,6-di-i-propylphenylimino)ethyl]pyridine](/data/chemimg/6300/204203-14-5.png)
![2,6-Bis[1-(2,6-di-i-propylphenylimino)ethyl]pyridine](/data/chemimg/6300/204203-14-5_b.png)
