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Rui Zhang - One of the best experts on this subject based on the ideXlab platform.
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synthetic and mechanistic investigations on manganese corrole catalyzed oxidation of sulfides with iodobenzene diacetate
Inorganica Chimica Acta, 2019Co-Authors: Davis Ranburger, Ben Willis, Benjamin Kash, Haleh Jeddi, Christian Alcantar, Rui ZhangAbstract:Abstract Manganese corrole complexes catalyze the efficient oxidation of organic sulfides to sulfoxides with iodobenzene diacetate [PhI(OAc)2] as a mild Oxygen Source in the presence of small amounts of water. Various substituted thioanisoles can be efficiently oxidized to sulfoxides with quantitative conversions (up to 2500 TONs) and excellent selectivies for sulfoxides. The catalyst effects, including the corrole ligands and oxidation states of the central manganese, were investigated, and showed a significant impact on the catalytic sulfoxidations. The previously known high-valent manganese(V)-oxo corroles were chemically generated and kinetically studied in the oxidation of thioanisole substrates. The competition results suggested the oxidation state of manganese metal is crucial to control the nature of active oxidant forms that significantly affected their catalytic activity.
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highly efficient and chemoselective oxidation of sulfides catalyzed by iron iii corroles with iodobenzene diacetate
Inorganica Chimica Acta, 2016Co-Authors: Tsehong Chen, Davis Ranburger, Ka Wai Kwong, Ngo Fung Lee, Rui ZhangAbstract:Abstract Iron(III) corrole complexes catalyze the highly chemoselective oxidation of sulfides to sulfoxides with iodobenzene diacetate [PhI(OAc)2] as a mild Oxygen Source. Various substituted thioanisoles, vinyl sulfides, and hydroxyl sulfides can be efficiently oxidized to sulfoxides with quantitative conversions (up to 5000 TONs) and excellent selectivities without over-oxidation to sulfones. The remarkably enhanced catalytic activity and stability against degradation is ascribed to the slow and steady-state formation of PhIO from highly soluble PhI(OAc)2 in the presence of a small amount of water. On the basis of Hammett correlation and mixing UV–vis spectral studies, a putative high-valent iron(V)-oxo species is likely generated as a short-lived active intermediate.
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enhanced iron iii corrole catalyzed oxidations with iodobenzene diacetate synthetic and mechanistic investigations
Applied Catalysis A-general, 2015Co-Authors: Tsehong Chen, Aaron Carver, Ka Wai Kwong, Weilong Luo, Rui ZhangAbstract:Abstract The electron-deficient iron(III) corrole complex catalyzes the efficient oxidation of hydrocarbons using PhI(OAc) 2 as an mild Oxygen Source. The catalyst stability against degradation was much enhanced owing to the mild oxidizing ability of PhI(OAc) 2 . Excellent selectivity and high catalytic efficiency (with up to 1400 TON) have been achieved in alkene epoxidations. This promising Oxygen transfer process is mechanistically rationalized in terms of a putative high-valent iron(V)-oxo species as the active oxidant.
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visible light promoted selective oxidation of sulfides to sulfoxides catalyzed by ruthenium porphyrins with iodobenzene diacetate
Applied Catalysis A-general, 2014Co-Authors: Tsehong Chen, Zhibo Yuan, Aaron Carver, Rui ZhangAbstract:Abstract Under visible light irradiation, the carbonyl ruthenium(II) porphyrin complexes efficiently catalyze the selective oxidation of sulfides to sulfoxides with iodobenzene diacetate [PhI(OAc) 2 ] as the Oxygen Source. Various thioanisoles and allylic sulfides were oxidized to the corresponding sulfoxides without overoxidation to sulfones. The high selectivity of this unprecedented Oxygen-transfer process is mechanistically rationalized by a low-reactivity ruthenium(IV)-oxo species which can be detected in the reaction of carbonyl ruthenium(II) porphyrin with iodobenzene diacetate. To the best of our knowledge, this is the first demonstration of a mild and high-yield method for the highly selective sulfoxidations by ruthenium porphyrins and PhI(OAc) 2 .
Markku Leskela - One of the best experts on this subject based on the ideXlab platform.
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heteroleptic cyclopentadienyl amidinate precursors for atomic layer deposition ald of y pr gd and dy oxide thin films
Chemistry of Materials, 2016Co-Authors: Sanni Seppala, Jaakko Niinisto, Mikko Ritala, Timothee Blanquart, Mikko Kaipio, Kenichiro Mizohata, J Raisanen, Clement Lansalotmatras, Wontae Noh, Markku LeskelaAbstract:Thin films of rare-earth (RE) oxides (Y2O3, PrOx, Gd2O3, and Dy2O3) were deposited by atomic layer deposition from liquid heteroleptic RE(iPrCp)2(iPr-amd) precursors with either water or ozone as the Oxygen Source. Film thickness, crystallinity, morphology, and composition were studied. Saturation was achieved with Gd2O3 when O3 was used as the Oxygen Source at 225 °C and with Y2O3 with both Oxygen Sources at as high temperature as 350 °C. The growth rates were 0.90–1.3 A/cycle for these processes. PrOx was challenging to deposit with both Oxygen Sources but with long, 20 s purges after the water pulses uniform films could be deposited. However, saturation was not achieved. With Dy2O3, uniform films could be deposited and the Dy(iPrCp)2(iPr-amd)/O3 process was close to saturation at 300 °C. The different Oxygen Sources had an effect on the crystallinity and impurity contents of the films in all the studied processes. Whether ozone or water was better choice for Oxygen Source depended on the metal oxide ma...
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structural and dielectric properties of thin zro2 films on silicon grown by atomic layer deposition from cyclopentadienyl precursor
Journal of Applied Physics, 2004Co-Authors: Jaakko Niinisto, Matti Putkonen, Kaupo Kukli, Mikko Ritala, Lauri Niinisto, Markku LeskelaAbstract:ZrO2 thin films with thicknesses below 20 nm were deposited by the atomic layer deposition process on Si(100) substrates at 350 °C. An organometallic precursor, Cp2Zr(CH3)2 (Cp=cyclopentadienyl, C5H5) was used as the zirconium Source and water or ozone as Oxygen Source. The influence of Oxygen Source and substrate pretreatment on the dielectric properties of ZrO2 films was investigated. Structural characterization with high-resolution transmission electron microscopy was performed to films grown onto HF-etched or native oxide covered silicon. Strong inhibition of ZrO2 film growth was observed with the water process on HF-etched Si. Ozone process on HF-etched Si resulted in interfacial SiO2 formation between the dense and uniform film and the substrate while water process produced interfacial layer with intermixing of SiO2 and ZrO2. The effective permittivity of ZrO2 in Al/ZrO2/Si/Al capacitor structures was dependent on the ZrO2 layer thickness and Oxygen Source used. The interfacial layer formation incre...
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atomic layer deposition and chemical vapor deposition of tantalum oxide by successive and simultaneous pulsing of tantalum ethoxide and tantalum chloride
Chemistry of Materials, 2000Co-Authors: Kaupo Kukli, Mikko Ritala, Markku LeskelaAbstract:Amorphous Ta2O5 films were grown by atomic layer deposition (ALD) or pulsed chemical vapor deposition (CVD) processes as a result of reactions between Ta(OC2H5)5 and TaCl5. Pulses of evaporized Ta precursors were led into the reactor successively or simultaneously. H2O could be applied as a supplementary Oxygen Source, but the films could be grown also in a water-free process. Films were grown in the temperature range of 275−450 °C. The growth rate of the films obtained by CVD using simultaneous pulsing of precursors exceeded 2.5 times that of the films obtained in the ALD process, where only one metal precursor was applied at a time. The refractive index and permittivity of the films increased with the growth temperature and frequency of Ta precursor pulses, approaching the values characteristic of the films obtained in the conventional ALD or CVD processes.
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atomic layer deposition of oxide thin films with metal alkoxides as Oxygen Sources
Science, 2000Co-Authors: Mikko Ritala, Kaupo Kukli, Markku Leskela, Antti Rahtu, Petri Raisanen, Timo Sajavaara, J KeinonenAbstract:A chemical approach to atomic layer deposition (ALD) of oxide thin films is reported here. Instead of using water or other compounds for an Oxygen Source, Oxygen is obtained from a metal alkoxide, which serves as both an Oxygen and a metal Source when it reacts with another metal compound such as a metal chloride or a metal alkyl. These reactions generally enable deposition of oxides of many metals. With this approach, an alumina film has been deposited on silicon without creating an interfacial silicon oxide layer that otherwise forms easily. This finding adds to the other benefits of the ALD method, especially the atomic-level thickness control and excellent uniformity, and takes a major step toward the scientifically challenging and technologically important task of replacing silica as the gate dielectric in the future generations of metal oxide semiconductor field effect transistors.
Bhalchandra M. Bhanage - One of the best experts on this subject based on the ideXlab platform.
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tert-Butyl Nitrite-Mediated Synthesis of N-Nitrosoamides, Carboxylic Acids, Benzocoumarins, and Isocoumarins from Amides
The Journal of organic chemistry, 2017Co-Authors: Subhash L. Yedage, Bhalchandra M. BhanageAbstract:This work reports tert-butyl nitrite (TBN) as a multitask reagent for (1) the controlled synthesis of N-nitrosoamide from N-alkyl amides, (2) hydrolysis of N-methoxyamides to carboxylic acids, (3) metal- and oxidant-free benzocoumarin synthesis from ortho-aryl-N-methoxyamides via N-H, C-N, and C-H bond activation, and (4) isocoumarin synthesis using Ru(II)/PEG as a recyclable catalytic system via ortho-C-H activation and TBN as an Oxygen Source. The sequential functional group interconversion of amide to acid has also been examined using IR spectroscopic analysis. Additionally, this methodology is highly advantageous due to short reaction time, gram scale synthesis, and broad substrate scope.
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tert-Butyl Nitrite-Mediated Synthesis of N‑Nitrosoamides, Carboxylic Acids, Benzocoumarins, and Isocoumarins from Amides
2017Co-Authors: Subhash L. Yedage, Bhalchandra M. BhanageAbstract:This work reports tert-butyl nitrite (TBN) as a multitask reagent for (1) the controlled synthesis of N-nitrosoamide from N-alkyl amides, (2) hydrolysis of N-methoxyamides to carboxylic acids, (3) metal- and oxidant-free benzocoumarin synthesis from ortho-aryl-N-methoxyamides via N–H, C–N, and C–H bond activation, and (4) isocoumarin synthesis using Ru(II)/PEG as a recyclable catalytic system via ortho-C–H activation and TBN as an Oxygen Source. The sequential functional group interconversion of amide to acid has also been examined using IR spectroscopic analysis. Additionally, this methodology is highly advantageous due to short reaction time, gram scale synthesis, and broad substrate scope
Cubillos Lobo, Jairo Antonio - One of the best experts on this subject based on the ideXlab platform.
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Catalizador de Jacobsen inmovilizado en Al-MCM-41 y en Si-MCM-41 modificada con grupos amino y su actividad en la epoxidación enantioselectiva heterogénea utilizando dimetildioxirano generado in situ como oxidante
Universidad de Antioquia Facultad de Ingeniería, 2007Co-Authors: Cubillos Lobo, Jairo Antonio, Holderich WolfgangAbstract:En este trabajo se investigó la actividad catalítica del catalizador de Jacobsen inmovilizado en Al-MCMC-41 y en NH2-Si-MCM-41 en la epoxidación enantioselectiva de tres olefinas proquirales, utilizando dimetildioxirano generado in situ como agente oxidante. Con este agente oxidante, el catalizador no sufrió cambios significativos en su estructura química. El catalizador se reutilizó exitosamente, cuando se inmovilizó por enlace químico covalente a través del ligando de salen.The enantioselective epoxidation of three prochiral olefins over Jacobsen's catalyst immobilized on Al-MCM-41 and NH2-Si-MCM-41 in the presence of in situ generated DMD as the Oxygen Source was investigated. Experimental results indicate that the catalyst did not significantly suffer any change in its chemical structure. Therefore, the reusability of catalyst could be successfully achieved when it was immobilized by chemical bonding of the salen ligand
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Heterogeneous asymmetric epoxidation of cis-ethyl cinnamte over Jacobsen's catalyst immobilized in inorganic porous materials
Publikationsserver der RWTH Aachen University, 2005Co-Authors: Cubillos Lobo, Jairo AntonioAbstract:(2R,3R)-cis-ethyl phenylglycidate obtained from cis-ethyl cinnamate enantioselective epoxidation is a very important intermediate for the synthesis of taxol and taxotère, drugs used for the treatment of breast, lung, and ovarian cancer. Among several catalytic methods, the homogeneous asymmetric epoxidation reported by Jacobsen and his colleagues is one of the most relevant methods. However the chiral catalyst, a Manganese(lll) salen complex coexists with the reaction products in one unique phase. This makes it difficult to separate the reaction products and catalyst reusability, two key features in the drive to develop an industrial process. Therefore many efforts have been made for the heterogenization of Jacobsen type catalysts either by using an inorganic or organic matrix as support material. Although, various heterogeneous systems have proved to be stable to leaching, catalyst degradation under prolonged oxidation conditions has limited the catalyst re-use. In this PhD work, the Jacobsen's catalyst has been immobilized on highly dealuminated zeolites X and Y, AI-MCM-41 and Si-MCM-41 using different methods. Mesopores completely surrounded by micropores were created inside the crystallites of zeolite X and Y. AI-MCM-41 and Si-MCM-41 were prepared by conventional methods. Using in situ generated DMD as Oxygen Source for the enantioselective epoxidation of olefins more reactive than c/s-ethyl cinnamate, the oxidative degradation of the catalyst could be prevented. Also, the un-immobilized catalyst proved to be partially recoverable. Here, the catalyst reuse gave an activity loss, although the initial enantioselectivity could be maintained through three cycles. The activity loss is associated with incomplete recovery of the catalyst rather than catalyst degradation. These results suggest that milder reaction conditions can be obtained with substrates easy to oxidize and with Oxygen Source prepared in situ. In this way, the reusability of the catalyst can be achieved powerfully
Tsehong Chen - One of the best experts on this subject based on the ideXlab platform.
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highly efficient and chemoselective oxidation of sulfides catalyzed by iron iii corroles with iodobenzene diacetate
Inorganica Chimica Acta, 2016Co-Authors: Tsehong Chen, Davis Ranburger, Ka Wai Kwong, Ngo Fung Lee, Rui ZhangAbstract:Abstract Iron(III) corrole complexes catalyze the highly chemoselective oxidation of sulfides to sulfoxides with iodobenzene diacetate [PhI(OAc)2] as a mild Oxygen Source. Various substituted thioanisoles, vinyl sulfides, and hydroxyl sulfides can be efficiently oxidized to sulfoxides with quantitative conversions (up to 5000 TONs) and excellent selectivities without over-oxidation to sulfones. The remarkably enhanced catalytic activity and stability against degradation is ascribed to the slow and steady-state formation of PhIO from highly soluble PhI(OAc)2 in the presence of a small amount of water. On the basis of Hammett correlation and mixing UV–vis spectral studies, a putative high-valent iron(V)-oxo species is likely generated as a short-lived active intermediate.
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enhanced iron iii corrole catalyzed oxidations with iodobenzene diacetate synthetic and mechanistic investigations
Applied Catalysis A-general, 2015Co-Authors: Tsehong Chen, Aaron Carver, Ka Wai Kwong, Weilong Luo, Rui ZhangAbstract:Abstract The electron-deficient iron(III) corrole complex catalyzes the efficient oxidation of hydrocarbons using PhI(OAc) 2 as an mild Oxygen Source. The catalyst stability against degradation was much enhanced owing to the mild oxidizing ability of PhI(OAc) 2 . Excellent selectivity and high catalytic efficiency (with up to 1400 TON) have been achieved in alkene epoxidations. This promising Oxygen transfer process is mechanistically rationalized in terms of a putative high-valent iron(V)-oxo species as the active oxidant.
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visible light promoted selective oxidation of sulfides to sulfoxides catalyzed by ruthenium porphyrins with iodobenzene diacetate
Applied Catalysis A-general, 2014Co-Authors: Tsehong Chen, Zhibo Yuan, Aaron Carver, Rui ZhangAbstract:Abstract Under visible light irradiation, the carbonyl ruthenium(II) porphyrin complexes efficiently catalyze the selective oxidation of sulfides to sulfoxides with iodobenzene diacetate [PhI(OAc) 2 ] as the Oxygen Source. Various thioanisoles and allylic sulfides were oxidized to the corresponding sulfoxides without overoxidation to sulfones. The high selectivity of this unprecedented Oxygen-transfer process is mechanistically rationalized by a low-reactivity ruthenium(IV)-oxo species which can be detected in the reaction of carbonyl ruthenium(II) porphyrin with iodobenzene diacetate. To the best of our knowledge, this is the first demonstration of a mild and high-yield method for the highly selective sulfoxidations by ruthenium porphyrins and PhI(OAc) 2 .
