The Experts below are selected from a list of 159 Experts worldwide ranked by ideXlab platform
Pakhing Leung - One of the best experts on this subject based on the ideXlab platform.
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palladium promoted asymmetric cycloaddition reaction of Arsole via an unusual exo endo stereochemically controlled method
Journal of Organometallic Chemistry, 2014Co-Authors: Zhijuan Yu, Sumod A Pullarkat, Pakhing LeungAbstract:Asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylArsole and ethyl vinyl ketone was promoted by the palladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary. The keto group in the resulting arsanorbornene cycloadducts could be located stereospecifically in the endo or exo position by controlling the electronic properties of the organopalladium promoter. In the intermolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 2:1. In the intramolecular process, however, only one As–O bidentate arsanorbornene palladium complex was produced stereoselectively. The arsenic-elimination reaction was readily observed on the corresponding endo- and exo-ketoarsine ligands. The absolute configuration and the coordination property of the enantiomerically pure endo-cycloadduct had been established by single-crystal X-ray analysis.
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Palladium-promoted asymmetric cycloaddition reaction of Arsole via an unusual exo–endo stereochemically controlled method
Journal of Organometallic Chemistry, 2014Co-Authors: Mengtao Ma, Zhijuan Yu, Sumod A Pullarkat, Pakhing LeungAbstract:Asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylArsole and ethyl vinyl ketone was promoted by the palladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary. The keto group in the resulting arsanorbornene cycloadducts could be located stereospecifically in the endo or exo position by controlling the electronic properties of the organopalladium promoter. In the intermolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 2:1. In the intramolecular process, however, only one As–O bidentate arsanorbornene palladium complex was produced stereoselectively. The arsenic-elimination reaction was readily observed on the corresponding endo- and exo-ketoarsine ligands. The absolute configuration and the coordination property of the enantiomerically pure endo-cycloadduct had been established by single-crystal X-ray analysis.
Kensuke Naka - One of the best experts on this subject based on the ideXlab platform.
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highly efficient singlet oxygen generation and high oxidation resistance enhanced by Arsole polymer based photosensitizer application as a recyclable photooxidation catalyst
Macromolecules, 2020Co-Authors: Susumu Tanaka, Hiroaki Imoto, Takuji Kato, Toshiaki Enoki, Yousuke Ooyama, Joji Ohshita, Kensuke NakaAbstract:Photosensitizers have attracted considerable attention in various fields such as organic synthesis and medical care. For the development of high-performance photosensitizers, highly efficient and p...
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The Dawn of Functional Organoarsenic Chemistry.
Chemistry: A European Journal, 2018Co-Authors: Hiroaki Imoto, Kensuke NakaAbstract:: Organoarsenic chemistry was actively studied until the middle of 20th century. Although various properties of organoarsenic compounds have been computationally predicted, for example, frontier orbital levels, aromaticity, and inversion energies, serious concern to the danger of their synthetic processes has restricted experimental studies. Conventional synthetic routes require volatile and toxic arsenic precursors. Recently, nonvolatile intermediate transformation (NIT) methods have been developed to safely access functional organoarsenic compounds. Important intermediates in the NIT methods are cyclooligoarsines, which are prepared from nonvolatile inorganic precursors. In particular, the new approach has realized experimental studies on conjugated arsenic compounds: Arsole derivatives. The elucidation of their intrinsic properties has triggered studies on functional organoarsenic chemistry. As a result, various kinds of arsenic-containing π-conjugated molecules and polymers have been reported for the last few years. In this minireview, progress of this recently invigorated field is overviewed.
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Peraryl Arsoles: Practical Synthesis, Electronic Structures, and Solid-State Emission Behaviors.
Chemistry: A European Journal, 2018Co-Authors: Hiroaki Imoto, Aya Urushizaki, Ikuo Kawashima, Kensuke NakaAbstract:: 2,3,4,5-Tetraaryl-1-phenylArsoles were synthesized by utilizing safely generated diiodophenylarsine and zirconacyclopentadienes. The obtained peraryl Arsoles showed aggregation-induced emission (AIE), where intense emission was observed in the solid states (quantum yields up to 0.61), whereas the corresponding solutions were very weakly emissive. The optical and electronic properties were examined by experimental and computational methods. It was elucidated that the aryl groups at the 2,5-positions affected the frontier orbitals and the aromaticity of the Arsole core. On the other hand, those at the 1,3,5-positions were perpendicular to the luminophore and effective for a restriction of aggregation-caused quenching. Because the lone pair of the arsenic atom has a sufficient coordination ability due to the low aromaticity of the Arsole moiety, a gold(I) chloride complex of 1,2,3,4,5-pentaphenylArsole was synthesized. The complex formation caused a blue shift of the emission from the bare ligand. Interestingly, the complex showed luminescent mechanochromism; grinding the crystals with a blue emission (λem =445 nm) gave amorphous samples with a greenish-blue emission (λem =496 nm).
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Multi-mode emission color tuning of dithieno[3,2-b:2′,3′-d]Arsoles
Journal of Materials Chemistry C, 2017Co-Authors: Hiroaki Imoto, Ikuo Kawashima, Susumu Tanaka, Chieko Yamazawa, Kensuke NakaAbstract:The electronic structures of dithienoArsoles, which were prepared through a facile and safe synthetic procedure, were tuned in multiple ways: structural modification of the π-conjugated system and reactions of the arsenic atom. Suzuki–Miyaura coupling reaction proceeded without coordination to the catalyst or oxidation during the reaction, though the lone pair of the arsenic atom was not protected. As a result, the emission color was successfully controlled. Moreover, oxidation and coordination of the arsenic atom effectively changed the electronic structures, resulting in emission color change. Theoretical calculations revealed that the LUMO levels were significantly lowered by oxidation and coordination. High air-stability and moderate coordination ability of a trivalent arsenic atom enabled various such transformations for emission color tuning.
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Arsole containing π conjugated polymer by the post element transformation technique
Angewandte Chemie, 2016Co-Authors: Yoshimasa Matsumura, Hiroaki Imoto, Kensuke Naka, Makoto Ishidoshiro, Yasuyuki Irie, Kazuyoshi Tanaka, Shinsuke Inagi, Ikuyoshi TomitaAbstract:A synthetic method to obtain an Arsole-containing π-conjugated polymer by the post-transformation of the organotitanium polymer titanacyclopentadiene-2,5-diyl unit with an arsenic-containing building block is described. The UV/Vis absorption maximum and onset of the polymer were observed at 517 nm and 612 nm, respectively. The polymer exhibits orange photoluminescence with an emission maximum (Emax) of 600 nm and the quantum yield (Φ) of 0.05. The polymer proved to exhibit a quasi-reversible redox behavior in its cyclic voltammetric (CV) analysis. The energy levels of the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) were estimated to be −5.43 and −3.24 eV, respectively, from the onsets for oxidation and reduction signals in the CV analysis. Further chemical modification of the Arsole unit in the π-conjugated polymer by complexation of gold(I) chloride occurred smoothly resulting in the bathochromic shift of the UV/Vis absorption and lowering of the LUMO energy level.
Zhijuan Yu - One of the best experts on this subject based on the ideXlab platform.
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palladium promoted asymmetric cycloaddition reaction of Arsole via an unusual exo endo stereochemically controlled method
Journal of Organometallic Chemistry, 2014Co-Authors: Zhijuan Yu, Sumod A Pullarkat, Pakhing LeungAbstract:Asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylArsole and ethyl vinyl ketone was promoted by the palladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary. The keto group in the resulting arsanorbornene cycloadducts could be located stereospecifically in the endo or exo position by controlling the electronic properties of the organopalladium promoter. In the intermolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 2:1. In the intramolecular process, however, only one As–O bidentate arsanorbornene palladium complex was produced stereoselectively. The arsenic-elimination reaction was readily observed on the corresponding endo- and exo-ketoarsine ligands. The absolute configuration and the coordination property of the enantiomerically pure endo-cycloadduct had been established by single-crystal X-ray analysis.
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Palladium-promoted asymmetric cycloaddition reaction of Arsole via an unusual exo–endo stereochemically controlled method
Journal of Organometallic Chemistry, 2014Co-Authors: Mengtao Ma, Zhijuan Yu, Sumod A Pullarkat, Pakhing LeungAbstract:Asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylArsole and ethyl vinyl ketone was promoted by the palladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary. The keto group in the resulting arsanorbornene cycloadducts could be located stereospecifically in the endo or exo position by controlling the electronic properties of the organopalladium promoter. In the intermolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 2:1. In the intramolecular process, however, only one As–O bidentate arsanorbornene palladium complex was produced stereoselectively. The arsenic-elimination reaction was readily observed on the corresponding endo- and exo-ketoarsine ligands. The absolute configuration and the coordination property of the enantiomerically pure endo-cycloadduct had been established by single-crystal X-ray analysis.
Rebecca L. Melen - One of the best experts on this subject based on the ideXlab platform.
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arsenic catalysis hydroboration of aldehydes using a benzo fused diaza benzyloxy Arsole
Chemistry: A European Journal, 2018Co-Authors: Darren M. C. Ould, Rebecca L. MelenAbstract:The first example of a homogenous As(III) catalyst for hydroboration has been established. The reaction of N,N'‐diisopropylbenzene diamine or toluene‐3,4‐dithiol with AsCl3 yielded the chloroArsoles (1 and 2) which upon reaction with benzyl alcohol led to the the benzyloxy benzo‐1,3,2‐diazaArsole (3) and benzo‐1,3,2‐dithiaArsole (4) respectively. 3 was found to be an excellent catalyst for the hydroboration of aldehyde substrates.
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Arsenic Catalysis: Hydroboration of Aldehydes Using a Benzo‐Fused Diaza‐benzyloxy‐Arsole
Chemistry: A European Journal, 2018Co-Authors: Darren M. C. Ould, Rebecca L. MelenAbstract:The first example of a homogenous As(III) catalyst for hydroboration has been established. The reaction of N,N'‐diisopropylbenzene diamine or toluene‐3,4‐dithiol with AsCl3 yielded the chloroArsoles (1 and 2) which upon reaction with benzyl alcohol led to the the benzyloxy benzo‐1,3,2‐diazaArsole (3) and benzo‐1,3,2‐dithiaArsole (4) respectively. 3 was found to be an excellent catalyst for the hydroboration of aldehyde substrates.
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Investigations into the Photophysical and Electronic Properties of Pnictoles and Their Pnictenium Counterparts
Organometallics, 2017Co-Authors: Darren M. C. Ould, Lewis C. Wilkins, Alex C. Rigby, Samuel J. Adams, James Alexis Platts, Simon J. A. Pope, Emma Richards, Rebecca L. MelenAbstract:The reaction of phosphole/Arsole starting materials with a series of halide abstraction reagents afforded their respective phosphenium/arsenium complexes. UV–vis absorption and luminescence studies on these cations showed interesting emission profiles, which were found to be dependent upon counterion choice. The addition of a reductant to the phosphole reagent garnered a dimeric species with a central P–P bond, which when heated was found to undergo homolytic bond cleavage to produce an 11π radical complex. Electron paramagnetic resonance (EPR), supported by density functional theory (DFT) calculations, was used to characterize this radical species.
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Supramolecular aggregation in dithia-Arsoles: chlorides, cations and N-centred paddlewheels
CrystEngComm, 2017Co-Authors: Thao T. P. Tran, Darren M. C. Ould, Lewis C. Wilkins, Dominic S. Wright, Rebecca L. Melen, Jeremy M. RawsonAbstract:The benzo-fused dithia-chloro-Arsole derivative C6H4S2AsCl (1) is found to crystallise in the triclinic space group P with 17 molecules in the asymmetric unit whereas the tolyl derivative, MeC6H3S2AsCl (2) is polymorphic with the α-phase crystallising in the monoclinic space group P21/c with a single molecule in the asymmetric unit and the β-phase adopting a triclinic structure with two molecules in the asymmetric unit. Reaction of these dithia-chloro-Arsole derivatives with LiN(SiMe3)2 in a 3 : 1 mole ratio afforded the unique paddlewheel structure (MeC6H4S2As)3N (4).
Sumod A Pullarkat - One of the best experts on this subject based on the ideXlab platform.
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palladium promoted asymmetric cycloaddition reaction of Arsole via an unusual exo endo stereochemically controlled method
Journal of Organometallic Chemistry, 2014Co-Authors: Zhijuan Yu, Sumod A Pullarkat, Pakhing LeungAbstract:Asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylArsole and ethyl vinyl ketone was promoted by the palladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary. The keto group in the resulting arsanorbornene cycloadducts could be located stereospecifically in the endo or exo position by controlling the electronic properties of the organopalladium promoter. In the intermolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 2:1. In the intramolecular process, however, only one As–O bidentate arsanorbornene palladium complex was produced stereoselectively. The arsenic-elimination reaction was readily observed on the corresponding endo- and exo-ketoarsine ligands. The absolute configuration and the coordination property of the enantiomerically pure endo-cycloadduct had been established by single-crystal X-ray analysis.
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Palladium-promoted asymmetric cycloaddition reaction of Arsole via an unusual exo–endo stereochemically controlled method
Journal of Organometallic Chemistry, 2014Co-Authors: Mengtao Ma, Zhijuan Yu, Sumod A Pullarkat, Pakhing LeungAbstract:Asymmetric cycloaddition reaction between 3,4-dimethyl-1-phenylArsole and ethyl vinyl ketone was promoted by the palladium complex containing ortho-metalated (S)-[1-(dimethylamino)ethyl]naphthalene as the chiral auxiliary. The keto group in the resulting arsanorbornene cycloadducts could be located stereospecifically in the endo or exo position by controlling the electronic properties of the organopalladium promoter. In the intermolecular cycloaddition reaction, a pair of separable diastereomeric palladium complexes was obtained in the ratio of 2:1. In the intramolecular process, however, only one As–O bidentate arsanorbornene palladium complex was produced stereoselectively. The arsenic-elimination reaction was readily observed on the corresponding endo- and exo-ketoarsine ligands. The absolute configuration and the coordination property of the enantiomerically pure endo-cycloadduct had been established by single-crystal X-ray analysis.
