- (PPh4)2: A Copper Hydride Nanocluster with a Bisquare Antiprismatic Core
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Atomically precise coinage metal (Au, Ag, and Cu) nanoclusters (NCs) have been the subject of immense interest for their intriguing structural, photophysical, and catalytic properties. However, the synthesis of Cu NCs is highly challenging because of low reduction potential and high reactivity of copper, demonstrating the need for new synthetic methods using appropriate ligand combinations. By designing a diamine-assisted synthetic strategy, here we report the synthesis and total structure characterization of a box-like dianionic Cu NC [Cu32(PET)24H8Cl2](PPh4)2 coprotected by 2-phenylethanethiolate (PET), hydride, and chloride ligands. Its crystal structure comprises a rare bisquare antiprismatic Cu14H8 core, assembled by two square antiprisms by edge sharing, followed by hydride binding. The rod-shaped Cu14H8 core is clamped by two complex Cu7(PET)11Cl and two simple Cu2PET metal ligand frameworks, constructing the complete structure of Cu32 NC. The presence, number, and location of hydrides are established by combined experimental and density functional theory results. The electronic structure calculations show the cluster as a zero-free-electron system, reproduce well the measured optical absorption spectrum, and explain the main absorption features. Furthermore, the Cu32 cluster is found to be a highly active homogeneous catalyst for C-N bond formation in aniline carbonylation reactions at room temperature. We hope that new findings in this work will stimulate and expand the research on Cu and other active metal NCs.
- Baek, Woonhyuk,Bootharaju, Megalamane S.,Deng, Guocheng,H?kkinen, Hannu,Hyeon, Taeghwan,Lee, Sanghwa,Malola, Sami,Zheng, Nanfeng
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p. 13974 - 13981
(2020/09/18)
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- METHOD FOR PRODUCING CARBAMATE
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PROBLEM TO BE SOLVED: To provide a method for producing carbamate in which a high yield can be obtained and the amount of by-products produced can be reduced. SOLUTION: In the method, carbamate is synthesized using at least one member selected from the group consisting of amine and derivative thereof, alcohol having 3 or more carbon atoms and carbon dioxide as a raw material, cerium oxide as a catalyst, and 2-cyanopyridine as a dehydrating agent. By using an alcohol having 3 or more carbon atoms, a high yield can be obtained and the amount of by-products produced can be reduced. In addition, the pressure of carbon dioxide can be lowered and the production can be of ease. SELECTED DRAWING: Figure 1 COPYRIGHT: (C)2018,JPO&INPIT
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Paragraph 0048; 0049
(2018/10/16)
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- Efficient preparation of carbamates by Rh-catalysed oxidative carbonylation: unveiling the role of the oxidant
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The synthesis of a wide variety of carbamates from amines, alcohols and carbon monoxide has been achieved by means of a Rh-catalysed oxidative carbonylation reaction that uses Oxone as a stoichiometric oxidant. In-depth studies on the reaction mechanism shed light on the intimate role of Oxone in the catalytic cycle.
- Iturmendi, Amaia,Iglesias, Manuel,Munárriz, Julen,Polo, Victor,Pérez-Torrente, Jesús J.,Oro, Luis A.
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supporting information
p. 404 - 407
(2017/01/03)
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- Copper-catalyzed carbonylation of anilines by diisopropyl azodicarboxylate for the synthesis of carbamates
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A Cu-catalyzed efficient methodology for the direct carbonylation of anilines has been developed. The N-H bond cleavage and N-C bond formation were notably achieved under solvent-free conditions and a variety of carbamates were synthesized from readily available anilines using diisopropyl azodicarboxylate (DIAD) as the carbonylating source.
- Usman, Muhammad,Ren, Zhi-Hui,Wang, Yao-Yu,Guan, Zheng-Hui
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p. 107542 - 107546
(2016/11/29)
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- (Tosylimino)phenyl-λ3-iodane as a reagent for the synthesis of methyl carbamates via hofmann rearrangement of aromatic and aliphatic carboxamides
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A new, mild procedure for the Hofmann rearrangement of aromatic and aliphatic carboxamides using (tosylimino)phenyl-λ3-iodane, PhINTs, as a reagent is reported. Because of the mild reaction conditions, this method is particularly useful for the Hofmann rearrangement of substituted benzamides, which usually afford complex reaction mixtures with other hypervalent iodine oxidants. The mild reaction conditions and high selectivity in the reaction of carboxamides with PhINTs allow the isolation of the initially formed labile isocyanates or their subsequent conversion to stable carbamates by treatment with alcohols.
- Yoshimura, Akira,Luedtke, Matthew W.,Zhdankin, Viktor V.
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p. 2087 - 2091
(2012/05/05)
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- Palladium-catalyzed carbonylation of amines: Switchable approaches to carbamates and N,N′-disubstituted ureas
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Switchable access to carbamates and ureas has been developed by solvent control palladium-catalyzed carbonylation of aromatic amines under an atmosphere of carbon monoxide. A variety of N-phenylcarbamates and N,N′- diphenylureas was easily synthesized in good to excellent yields from readily available aromatic amines under mild conditions. Copyright
- Guan, Zheng-Hui,Lei, Hao,Chen, Ming,Ren, Zhi-Hui,Bai, Yinjuan,Wang, Yao-Yu
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supporting information; experimental part
p. 489 - 496
(2012/04/04)
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- Catalytic metathesis of carbon dioxide with heterocumulenes mediated by titanium isopropoxide
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The insertion of an isopropoxide ligand of titanium isopropoxide into heterocumulenes gives a product that carries out metathesis at elevated temperatures by undergoing insertion of a second heterocumulene in a head to head fashion, followed by an extrusion reaction. The Royal Society of Chemistry 2005.
- Ghosh, Rajshekhar,Samuelson, Ashoka G.
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p. 2017 - 2019
(2007/10/03)
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- Reversible double insertion of aryl isocyanates into the Ti-O bond of titanium(IV) isopropoxide
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The insertion of phenyl isocyanate into titanium isopropoxide leads to the formation of a dimeric complex [Ti(OiPr)2(μ-O iPr){C6H5N(OiPr)CO}]2 (1) which has been structurally characterized. Reaction of titanium isopropoxide with two and more than 2 equiv. of phenyl isocyanate is complicated by competitive, reversible insertion between the titanium carbamate and titanium isopropoxide. The ligand formed by insertion of phenyl isocyanate into the titanium carbamate has been structurally characterized in its protonated form C6H5N{C(OiPr)O}C(O)N(H)C6H 5 (3aH). Insertion into the carbamate is kinetically favored whereas insertion into isopropoxide gives the thermodynamically favored product.
- Ghosh, Rajshekhar,Nethaji, Munirathinam,Samuelson, Ashoka G.
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p. 1282 - 1293
(2007/10/03)
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- Multilevel selectivity in the mild and high-yielding chlorosilane- induced cleavage of carbamates to isocyanates
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The silane-induced cleavage of a series of N-p-tolylcarbamates and N- phenethylcarbamates to isocyanates has been investigated as a function of chlorosilane, carbamate substituent, and reaction conditions. Reaction yields were determined from the isolated ureas, which were formed by trapping the corresponding isocyanates with isobutylamine. Under room-temperature conditions, multilevel selectivity in carbamate activation has been demonstrated. This selectivity together with the generality of the methodology enhances the utility of carbamates as synthetic intermediates and protecting groups. To demonstrate the effectiveness of this selectivity, a series of biscarbamates were selectively monoactivated to isocyanates in excellent yields.
- Chong, Pek Y.,Janicki, Slawomir Z.,Petillo, Peter A.
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p. 8515 - 8521
(2007/10/03)
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