- Water oxidation intermediates applied to catalysis: Benzyl alcohol oxidation
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Four distinct intermediates, RuIV=O2+, Ru IV(OH)3+, RuV=O3+, and Ru V(OO)3+, formed by oxidation of the catalyst [Ru(Mebimpy)(4,4′-((HO)2OPCH2)s
- Vannucci, Aaron K.,Hull, Jonathan F.,Chen, Zuofeng,Binstead, Robert A.,Concepcion, Javier J.,Meyer, Thomas J.
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- An iron(II)[1,3-bis(2'-pyridylimino)isoindoline] complex as a catalyst for substrate oxidation with H2O2 - Evidence for a transient peroxidodiiron(III) species
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The complex [Fe(indH)(solvent)3](ClO4)2 (1) has been isolated from the reaction of equimolar amounts of 1,3-bis(2'-pyridylimino)isoindoline (indH) and Fe(ClO4)2 in acetonitrile and characterized by X-ray crystallography and several spectroscopic techniques. It is a suitable catalyst for the oxidation of thioanisoles and benzyl alcohols with H2O2 as the oxidant. Hammett correlations and kinetic isotope effect experiments support the involvement of an electrophilic metalbased oxidant. A metastable green species (2) is observed when 1 is reacted with H2O2 at -40 °C and has a FeIII(μ-O)(μ-O2)FeIII core on the basis of UV/Vis, electron paramagnetic resonance, resonance Raman, and X-ray absorption spectroscopic data.
- Pap, Jozsef S.,Cranswick, Matthew A.,Balogh-Hergovich,Barath, Gabor,Giorgi, Michel,Rohde, Gregory T.,Kaizer, Jozsef,Speier, Gabor,Que Jr., Lawrence
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- Nonheme Diiron Oxygenase Mimic That Generates a Diferric-Peroxo Intermediate Capable of Catalytic Olefin Epoxidation and Alkane Hydroxylation including Cyclohexane
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Herein are described substrate oxidations with H2O2 catalyzed by [FeII(IndH)(CH3CN)3](ClO4)2 [IndH = 1,3-bis(2′-pyridylimino)isoindoline], involving a spectroscopically characterized (μ-oxo)(μ-1,2-peroxo)diiron(III) intermediate (2) that is capable of olefin epoxidation and alkane hydroxylation including cyclohexane. Species 2 also converts ketones to lactones with a decay rate dependent on [ketone], suggesting direct nucleophilic attack of the substrate carbonyl group by the peroxo species. In contrast, peroxo decay is unaffected by the addition of olefins or alkanes, but the label from H218O is incorporated into the the epoxide and alcohol products, implicating a high-valent iron-oxo oxidant that derives from O-O bond cleavage of the peroxo intermediate. These results demonstrate an ambiphilic diferric-peroxo intermediate that mimics the range of oxidative reactivities associated with O2-activating nonheme diiron enzymes.
- Oloo, Williamson N.,Szávuly, Miklós,Kaizer, József,Que, Lawrence
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- Rh(III)-Catalyzed [4+2] Cyclization of 2-Aryl-1H-benzo[d]imidazoles with Maleimides via C-H Activation
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A rhodium-catalyzed formal [4+2]-cyclization of 2-aryl-1H-benzo[d]imidazoles with maleimides through C?H bond activation process is described here. Such an approach enables selectively construct a series of functionalized cis-dihydro-benzimidazo[2,1-a]iso
- Deng, Chen,Li, Changchang,Yao, Jinzhong,Jin, Quanli,Miao, Maozhong,Zhou, Hongwei
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supporting information
p. 3552 - 3558
(2021/07/26)
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- Rh(III)-Catalyzed C-H Olefination Cascades to Divergently Construct Diverse Polyheterocycles by Tuning Manipulations of Directing Groups
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Inspired by the diversity created by nature, organic chemists have been using a divergent strategy to improve the synthetic efficiency of diverse molecules. Transition-metal-catalyzed C-H functionalization has become one of the most straightforward, powerful, and atom-economical methods to construct complex scaffolds. However, C-H activation initiated divergent transformation to prepare diverse molecules is still limited. To address this challenge, we herein developed Rh(III)-catalyzed C-H olefination/annulation reaction cascades to divergently construct diverse polyheterocycles by tuning manipulations of directing groups (DGs). Up to 9 distinct scaffolds were creatively synthesized under simple conditions with good functional group tolerance, chemo-, and regioselectivity. Such a versatile strategy and its extension may encourage researchers to discover more promising manipulations of DGs for transition-metal-catalyzed C-H bond activation, making diverse available targets and materials that would have been previously out of range.
- Huang, Tianle,Wang, Ting,Shi, Yuesen,Chen, Jian,Guo, Xiaoyu,Lai, Ruizhi,Liu, Xuexin,Wu, Zhouping,Peng, Dongxue,Wang, Longyu,Li, Hao,Hai, Li,Wu, Yong
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supporting information
p. 1548 - 1553
(2021/03/08)
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- Divergent Construction of Diverse Scaffolds through Catalyst-Controlled C?H Activation Cascades of Quinazolinones and Cyclopropenones
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A transition-metal-catalyzed C?H activation cascade strategy to rapidly construct diverse quinazolinone derivatives in a one-pot manner is reported. The catalysts play an important role in the different transformations. Additionally, the procedure is scal
- Shi, Yuesen,Huang, Tianle,Wang, Ting,Chen, Jian,Liu, Xuexin,Wu, Zhouping,Huang, Xiaofang,Zheng, Yao,Yang, Zhongzhen,Wu, Yong
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supporting information
p. 13346 - 13351
(2021/08/12)
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- One-Pot Construction of Diverse Products using Versatile Cyclopropenones
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Tunable C?H activation cascade reactions between quinazolinones and cyclopropenones have been developed. Notably, cyclopropenones, acting as multi-functional building blocks, could be assembled to construct up to 10 distinct heterocyclic scaffolds in a one-pot manner. (Figure presented.).
- Huang, Tianle,Yang, Chunyan,Shi, Yuesen,Chen, Jian,Wang, Ting,Guo, Xiaoyu,Liu, Xuexin,Ding, Haosheng,Wu, Zhouping,Hai, Li,Wu, Yong
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supporting information
p. 4899 - 4904
(2021/09/14)
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- Metal- And additive-free C-H oxygenation of alkylarenes by visible-light photoredox catalysis
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A metal- and additive-free methodology for the highly selective, photocatalyzed C-H oxygenation of alkylarenes under air to the corresponding carbonyls is presented. The process is catalyzed by an imide-acridinium that forms an extremely strong photooxidant upon visible light irradiation, which is able to activate inert alkylarenes such as toluene. Hence, this is an easy to perform, sustainable and environmentally friendly oxidation that provides valuable carbonyls from abundant, readily available compounds.
- García Manche?o, Olga,Kuhlmann, Jan H.,Pérez-Aguilar, María Carmen,Piekarski, Dariusz G.,Uygur, Mustafa
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p. 3392 - 3399
(2021/05/21)
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- Photoredox Catalysis of Aromatic β-Ketoesters for in Situ Production of Transient and Persistent Radicals for Organic Transformation
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Radical formation is the initial step for conventional radical chemistry. Reported herein is a unified strategy to generate radicals in situ from aromatic β-ketoesters by using a photocatalyst. Under visible-light irradiation, a small amount of photocatalyst fac-Ir(ppy)3 generates a transient α-carbonyl radical and persistent ketyl radical in situ. In contrast to the well-established approaches, neither stoichiometric external oxidant nor reductant is required for this reaction. The synthetic utility is demonstrated by pinacol coupling of ketyl radicals and benzannulation of α-carbonyl radicals with alkynes to give a series of highly substituted 1-naphthols in good to excellent yields. The readily available photocatalyst, mild reaction conditions, broad substrate scope, and high functional-group tolerance make this reaction a useful synthetic tool.
- Chen, Bin,Feng, Ke,Guo, Jia-Dong,Tung, Chen-Ho,Wu, Li-Zhu,Xiao, Hongyan,Yang, Xiu-Long
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supporting information
p. 5365 - 5370
(2020/02/28)
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- An alternative pathway for the formation of aromatic aroma compounds derived from L-phenylalanine via phenylpyruvic acid in tea (Camellia sinensis (L.) O. Kuntze) leaves
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Aromatic aroma compounds contribute to flavor of tea (Camellia sinensis (L.) O. Kuntze) and they are mostly derived from L-phenylalanine via trans-cinnamic acid or directly from L-phenylalanine. The objective of this study was to investigate whether an alternative pathway derived from L-phenylalanine via phenylpyruvic acid is involved in formation of aroma compounds in tea. Enzyme reaction with phenylpyruvic acid showed that benzaldehyde, benzyl alcohol, and methyl benzoate were derived from phenylpyruvic acid in tea leaves. Feeding experiments using [2H8]L-phenylalanine indicated that phenylpyruvic acid was derived from L-phenylalanine in a reaction catalyzed by aromatic amino acid aminotransferases (AAATs). CsAAAT1 showed higher catalytic efficiency towards L-phenylalanine (p ≤ 0.001) while CsAAAT2 showed higher catalytic efficiency towards L-tyrosine (p ≤ 0.001). Both CsAAATs were localized in the cytoplasm of leaf cells. In conclusion, an alternative pathway for the formation of aromatic aroma compounds derived from L-phenylalanine via phenylpyruvic acid occurred in tea leaves.
- Wang, Xiaoqin,Zeng, Lanting,Liao, Yinyin,Zhou, Ying,Xu, Xinlan,Dong, Fang,Yang, Ziyin
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- Stable isotope labeled leucomalachite green and synthesis method thereof
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The invention discloses stable isotope labeled leucomalachite green and a synthesis method thereof. The method comprises the following steps: (a), oxidizing stable isotope labeled methylbenzene in a mixed solvent of acetic acid, acetic anhydride and conce
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- A hydrogen-atom transfer mechanism in the oxidation of alcohols by [FeO4]2- in aqueous solution
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The ferrate(vi) ion, [FeO4]2-, has attracted much interest in recent years because of its potential use as a green oxidant in organic synthesis and water treatment. Although there have been several reports on the use of ferrate(vi) for the oxidation of alcohols to the corresponding carbonyl compounds, the mechanism remains unclear. In this work, the kinetics of the oxidation of a series of alcohols with α-C-H bond dissociation energies ranging from 81 to 95 kcal mol-1 have been studied by UV/Vis spectrophotometry. The reactions are first-order in both [FeO4]2- and [alcohol]. The deuterium isotope effects for the oxidation of methanol/d4-methanol, ethanol/d6-ethanol and benzyl alcohol/d7-benzyl alcohol are 18.0 ± 0.1, 4.1 ± 0.1 and 11.2 ± 0.1, respectively. A linear correlation is found between the second-order rate constants and the α-C-H bond dissociation energies (BDEs) of the alcohols, consistent with a hydrogen atom transfer (HAT) mechanism. The proposed HAT mechanism is supported by DFT calculations.
- Xie, Jianhui,Lo, Po-Kam,Lam, Chow-Shing,Lau, Kai-Chung,Lau, Tai-Chu
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p. 240 - 245
(2017/12/27)
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- Catalytic Aerobic Oxidation of Alcohols by Copper Complexes Bearing Redox-Active Ligands with Tunable H-Bonding Groups
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In this research article, we describe the structure, spectroscopy, and reactivity of a family of copper complexes bearing bidentate redox-active ligands that contain H-bonding donor groups. Single-crystal X-ray crystallography shows that these tetracoordi
- Rajabimoghadam, Khashayar,Darwish, Yousef,Bashir, Umyeena,Pitman, Dylan,Eichelberger, Sidney,Siegler, Maxime A.,Swart, Marcel,Garcia-Bosch, Isaac
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p. 16625 - 16634
(2018/12/11)
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- Associative Covalent Relay: An Oxadiazolone Strategy for Rhodium(III)-Catalyzed Synthesis of Primary Pyridinylamines
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A relay formalism is proposed herein for categorizing the interplay among reactants, target product, and catalytic center in transition-metal catalysis, an important factor that can dictate overall catalysis viability and efficiency. In this formalism, transition-metal catalysis can proceed by dissociative relay, associative covalent relay, and associative dative relay modes. An intriguing associative covalent relay process operates in rhodium(III)-catalyzed oxadiazolone-directed alkenyl C?H coupling with alkynes and allows efficient access to primary pyridinylamines. Although the primary pyridinylamine synthesis mechanism is posteriori rationalized, the relay formalism formulated herein can provide an important mechanistic conceptual framework for future catalyst design and reaction development.
- Yu, Xiaolong,Chen, Kehao,Wang, Qi,Guo, Shan,Zha, Shanke,Zhu, Jin
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supporting information
p. 5222 - 5226
(2017/04/27)
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- Rh(III)-Catalyzed bilateral cyclization of aldehydes with nitrosos toward unsymmetrical acridines proceeding with C-H functionalization enabled by a transient directing group
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A Rh(iii)-catalyzed bilateral cyclization was developed for the efficient construction of acridines proceeding with C-H functionalization whereby in situ formation and removal of an imino transient directing group in the presence of catalytic amount of BnNH2 are achieved. In this transformation, a sequential Rh(iii)-catalyzed C-H amination, cyclization, and aromatization process was involved.
- Hu, Weiming,Zheng, Qingheng,Sun, Song,Cheng, Jiang
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supporting information
p. 6263 - 6266
(2017/07/07)
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- Direct access to cobaltacycles via C-H activation: N-chloroamide- enabled room-temperature synthesis of heterocycles
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Cobaltacycle synthesis via C-H activation has been achieved for the first time, providing key mechanistic insight into cobalt catalytic chemistry. NChloroamides are used as a directing synthon for cobalt-catalyzed roomtemperature C-H activation and construction of heterocycles. Alkynes as coupling partners allow convenient access to isoquinolones, a class of synthetically and pharmaceutically important compounds. The broad substrate scope enables a diverse range of substitution patterns to be incorporated into the heterocyclic scaffold.
- Yu, Xiaolong,Chen, Kehao,Guo, Shan,Shi, Pengfei,Song, Chao,Zhu, Jin
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supporting information
p. 5348 - 5351
(2017/11/07)
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- Rhodium(III)-catalyzed oxadiazole-directed alkenyl C-H activation for synthetic access to 2-acylamino and 2-amino pyridines
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We report herein a Rh(III)-catalyzed alkenyl C-H activation protocol for the coupling of oxadiazoles with alkynes and synthesis of 2- acylamino and 2-amino pyridines, an important heterocyclic scaffold for various naturals products and synthetic pharmaceuticals bearing a readily reacting functional group. The selective protection/deprotection of amino groups through simple solvent switching, good functional group compatibility, superior product yield, and high regioselectivity are some of the notable synthetic features witnessed in this reaction protocol.
- Yang, Fan,Yu, Jiaojiao,Liu, Yun,Zhu, Jin
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p. 9978 - 9987
(2018/05/31)
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- Tunable Triazole-Phosphine-Copper Catalysts for the Synthesis of 2-Aryl-1H-benzo[d]imidazoles from Benzyl Alcohols and Diamines by Acceptorless Dehydrogenation and Borrowing Hydrogen Reactions
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Triazole-phosphine-copper complexes (TAP?Cu) have been synthesized and applied as tunable and efficient catalysts for the selective synthesis of fluoro-substituted 2-aryl-1H-benzo[d]imidazole and 1-benzyl-2-aryl-1H-benzo[d]imidazole derivatives from simple alcohols in only one step. TAP?Cu exhibited excellent and tunable catalytic activity for both dehydrogenation and borrowing hydrogen reactions with more than 80 examples being demonstrated for the first time. It was observed that the ligand played a critical role in catalyst activity. Mechanistic studies and deuterium labeling experiments indicated that the reactions proceeded by an initial and reversible alcohol dehydrogenation resulting in a copper hydride intermediate. This was also supported by the direct observation of a diagnostic copper hydride signal by solid-state infrared spectroscopy. The TAP?Cu-H complex showed absorptions at 912 cm?1 that could be assigned to copper?hydride stretches. Furthermore, the direct trapping of an intermediate bisimine was also successfully performed. (Figure presented.).
- Xu, Zhaojun,Wang, Duo-Sheng,Yu, Xiaoli,Yang, Yongchun,Wang, Dawei
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p. 3332 - 3340
(2017/10/06)
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- Nonheme iron complex-catalyzed efficient alcohol oxidation by t-BuOOH with N-hydroxyphthalimide (NHPI) as co-catalyst: Implication of high valent iron-oxo species
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Two iron catalysts ([Fe(bpc)Cl2][Et4N] (1a) and [Fe(Me2bpb)Cl2][Et3NH] (1b)) displayed efficient catalysis in oxidation of various alcohols to the corresponding carbonyl products using t-BuOOH as an oxidant in the presence of N-hydroxyphthalimide (NHPI) under mild conditions. 1a having an electron-withdrawing group showed a little better catalytic activity than that of 1b with an electron-donating group. The mechanistic studies through Hammett plot, deuterium isotope effect, and the use of 2-methyl-1-phenylprop-2-yl hydroperoxide (MPPH) as a mechanistic probe suggested that the reactive oxidants responsible for the alcohol oxidation possibly involved FeIV[Formula presented]), and phthalimide N-oxyl radical [Formula presented]. On the other hand, the presence of imidazole increased the heterolytic cleavage of Fe-OOR intermediate to form FeV[Formula presented] species and accelerated its [Formula presented] bond cleavage rate. In particular, the formation of FeV[Formula presented] intermediate via the heterolytic cleavage of Fe-OOR species in the presence of imidazole in the catalytic oxidation systems of nonheme iron complexes with t-BuOOH was substantialized, for the first time, to the best of our knowledge.
- Bae, Jeong Mi,Lee, Myoung Mi,Lee, Seul Ah,Lee, Sun Young,Bok, Kwon Hee,Kim, Jinheung,Kim, Cheal
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- Oxygenation of Methylarenes to Benzaldehyde Derivatives by a Polyoxometalate Mediated Electron Transfer-Oxygen Transfer Reaction in Aqueous Sulfuric Acid
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The synthesis of benzaldehyde derivatives by oxygenation of methylarenes is of significant conceptual and practical interest because these compounds are important chemical intermediates whose synthesis is still carried out by nonsustainable methods with very low atom economy and formation of copious amounts of waste. Now an oxygenation reaction with a 100% theoretical atom economy using a polyoxometalate oxygen donor has been found. The product yield is typically above 95% with no "overoxidation" to benzoic acids; H2 is released by electrolysis, enabling additional reaction cycles. An electrocatalytic cycle is also feasible. This reaction is possible through the use of an aqueous sulfuric acid solvent, in an aqueous biphasic reaction mode that also allows simple catalyst recycling and recovery. The solvent plays a key role in the reaction mechanism by protonating the polyoxometalate thereby enabling the activation of the methylarenes by an electron transfer process. After additional proton transfer and oxygen transfer steps, benzylic alcohols are formed that further react by an electron transfer-proton transfer sequence forming benzaldehyde derivatives. (Chemical Equation Presented).
- Sarma, Bidyut Bikash,Efremenko, Irena,Neumann, Ronny
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supporting information
p. 5916 - 5922
(2015/05/27)
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- Chlorine-radical-mediated photocatalytic activation of C-H bonds with visible light
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Going green on the cheap: A highly effective photocatalytic reaction mode involving chlorine radicals generated on chlorinated BiOBr/TiO2 upon irradiation with visible light enabled selective transformations of alkanes into functionalized products through the formation of C-O and C-C bonds (see scheme). This process provides a sustainable strategy for direct C-H functionalization under mild conditions. Copyright
- Yuan, Rusheng,Fan, Shaolong,Zhou, Huaxi,Ding, Zhengxin,Lin, Sen,Li, Zhaohui,Zhang, Zizhong,Xu, Chao,Wu, Ling,Wang, Xuxu,Fu, Xianzhi
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supporting information
p. 1035 - 1039
(2013/03/13)
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- Development of a general non-noble metal catalyst for the benign amination of alcohols with amines and ammonia
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The N-alkylation of amines or ammonia with alcohols is a valuable route for the synthesis of N-alkyl amines. However, as a potentially clean and economic choice for N-alkyl amine synthesis, non-noble metal catalysts with high activity and good selectivity are rarely reported. Normally, they are severely limited due to low activity and poor generality. Herein, a simple NiCuFeOx catalyst was designed and prepared for the N-alkylation of ammonia or amines with alcohol or primary amines. N-alkyl amines with various structures were successfully synthesized in moderate to excellent yields in the absence of organic ligands and bases. Typically, primary amines could be efficiently transformed into secondary amines and N-heterocyclic compounds, and secondary amines could be N-alkylated to synthesize tertiary amines. Note that primary and secondary amines could be produced through a one-pot reaction of ammonia and alcohols. In addition to excellent catalytic performance, the catalyst itself possesses outstanding superiority, that is, it is air and moisture stable. Moreover, the magnetic property of this catalyst makes it easily separable from the reaction mixture and it could be recovered and reused for several runs without obvious deactivation. Copyright
- Cui, Xinjiang,Dai, Xingchao,Deng, Youquan,Shi, Feng
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supporting information
p. 3665 - 3675
(2013/03/29)
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- Fe2O3-supported nano-gold catalyzed one-pot synthesis of N-alkylated anilines from nitroarenes and alcohols
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Here, we show the one-step synthesis of N-alkylated anilines from nitrobenzenes and alcohols catalyzed by nano-gold catalyst. The yields to N-alkylated anilines were ~90% under mild conditions. The mechanism of this reaction was explored. It shows promise for clean and simple synthesis of N-alkylated anilines.
- Peng, Qiling,Zhang, Yan,Shi, Feng,Deng, Youquan
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supporting information; experimental part
p. 6476 - 6478
(2011/06/28)
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- Fe(II)-catalyzed N-alkylation of sulfonamides with benzylic alcohols
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The FeCl2/K2CO3 catalyst system was developed successfully for the N-alkylation of sulfonamides with benzylic alcohols via borrowing hydrogen method. XPS analysis suggested a possible catalyst cycle between Fe(II) and Fe(0). Under the optimized condition, the scope of the protocol was demonstrated in 21 different alkylation reactions. High yields, in general >90%, are achieved in most cases.
- Cui, Xinjiang,Shi, Feng,Zhang, Yan,Deng, Youquan
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supporting information; scheme or table
p. 2048 - 2051
(2010/06/16)
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- Copper-catalyzed N-alkylation of sulfonamides with benzylic alcohols: Catalysis and mechanistic studies
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The N-alkylation of sulfonamides with alcohols is efficiently performed in the presence of easily available copper catalysts via hydrogen borrowing methodology. Applying a copper acetate/potassium carbonate system the reaction of sulfonamides and alcohols gave the corresponding secondary amines in excellent yield. In situ HR-MS analysis indicated that bissulfonylated amines are formed under air atmosphere, which act as self-stabilizing Iigands for the catalytic system. UV-visible measurements suggest the interaction between the copper centre and the bissulfonylated amine. Reactions of benzyl alcohol-d 7 with p-toluenesulfonamide, Nbenzyl-p-toluenesulfonamide or N-benzylidenetoluenesulfonamide revealed that the reaction proceeds via a transfer hydrogenation mechanism and the whole process is micro-reversible. Competitive reactions of benzyl alcohol and benzyl alconol-d7 with ptoluenesulfonamide revealed a kinetic isotope effect (kH/kD) of 3.287 (0.192) for the dehydrogenation of benzyl alcohol and 0.611 (0.033) for the hydrogenation of the N-benzylidene-p-toluenesulfonamide intermediate, which suggests that dehydrogenation of the alcohol is the rate-determining step.
- Cui, Xinjiang,Shi, Feng,Tse, Man Kin,Goerdes, Dirk,Thurow, Kerstin,Beller, Matthias,Deng, Youquan
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scheme or table
p. 2949 - 2958
(2010/03/24)
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- Copper-catalyzed alkylation of sulfonamides with alcohols
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Water is the only by-product in an efficient and atom-economical Cu(OAc)2-catalyzed coupling of alcohols with sulfonamides (see proposed mechanism; Ts= p-toluenesulfonyl). It was discovered that bissulfonylated amidines formed as intermediates when the transhydrogenative C-N bond-forming reaction is carried out in air act as novel ligands to stabilize the catalyst.
- Shi, Feng,Tse, Man Kin,Cui, Xinjiang,Goerdes, Dirk,Michalik, Dirk,Thurow, Kerstin,Deng, Youquan,Beller, Matthias
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supporting information; experimental part
p. 5912 - 5915
(2009/12/08)
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- The synthesis and structures of deuterium-labeled 5-substituted 1H-tetrazoles
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The synthesis and crystal structures of deuterium-labeled 5-substituted 1H-tetrazoles, 5-[2H5]phenyl-1H-tetrazole (I), 5-[ 2H7]tolyl-1H-tetrazole (II), and 5-[2H 7]benzyl-1H-tetrazole (III)
- Zhao, Hong
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p. 293 - 296
(2008/12/22)
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- Supported ruthenium catalyst for the heterogeneous oxidation of alcohols with molecular oxygen
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Round and round it goes! A supported ruthenium catalyst, easily prepared by treatment of RuCl3 with γ-Al2O3, is an efficient heterogeneous catalyst for the oxidations of alcohols with 1 atm of molecular oxygen or air without any additives (see scheme). The spent catalyst was recyclable without an appreciable loss of the catalytic activity and selectivity for the oxidation.
- Yamaguchi, Kazuya,Mizuno, Noritaka
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p. 4538 - 4542
(2007/10/03)
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- Biosynthesis of defensive allomones in leaf beetle larvae: Stereochemistry of salicylalcohol oxidation in Phratora vitellinae and comparison of enzyme substrate and stereospecificity with alcohol oxidases from several iridoid producing leaf beetles
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(7S)-[2H5]-Salicylalcohol (3) and (7R)-[2H1]-salicylalcohol (5) have been synthesized in order to examine the stereospecificity of salicylalcohol oxidase from the defensive secretion of the salicylaldehyde-producing leaf beetle Phratora vitellinae. Oxidation was found to proceed by selective removal of the C(7)-H(R) hydrogen atom (Re-specificity) to yield salicylaldehyde. (7S)-[2H6]-Benzylalcohol (9) was also oxidized Re-specifically to benzaldehyde, but in much lower yield, indicating the importance of the orthohydroxy group of salicylalcohol in substrate enzyme binding. The stereospecificities of terpenoid oxidases from six species of iridoid-producing leaf beetle were examined using (1R,8R)-[2H2]-8-hydroxygeraniol (10), and were all found to oxidize the substrate Re-specifically. Cross-activity of oxidation was found in a number of species, with P. vitellinae able to oxidize terpenoid (10) and two of the iridoid-producing species able to oxidize salicylalcohol analogue (3), again with Re-specificity. However, when the two substrate analogs were presented together, in equal concentrations, preferential oxidation of the natural analog was observed in each case. The kinetics of oxidation for a number of terpenoid and aromatic alcohols by the defensive secretion of the iridoid-producing leaf beetle Phaedon armoraciae have been studied, revealing a large difference between the rate of (primary, allylic) terpenoid alcohol oxidation and the rate of salicylalcohol oxidation, thus accounting for the observed selectivity.
- Veith,Oldham,Dettner,Pasteels,Boland
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p. 429 - 443
(2007/10/03)
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- Photocatalytic Oxidation of Toluene to Benzaldehyde by Molecular Oxygen
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The visible light irradiation of aqueous solutions containing toluene, uranyl(VI) ions, and O2 results in the formation of benzaldehyde as a major product.Small amounts of PhCH2OH are also formed.The yields of benzaldehyde are 3 times greater for toluene-h8 than for toluene-d8, but the kinetic isotope effect for the quenching of the excited state *UO2(2+) by toluene is negligible (ktoluene-h8/ktoluene-d8 = 1.2).This and other evidence indicate that the quenching takes place in two parallel pathways.The major one involves the aromatic portion of toluene and leads to the recovery of the reactants.The minor, productive path takes place by hydrogen atom abstraction from the methyl group, followed by the oxidation of PhCH2(.).Cumene, benzyl alcohol, and benzaldehyde react similarly.
- Mao, Yun,Bakac, Andreja
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p. 4219 - 4223
(2007/10/03)
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- SELECTIVE MONO- OR DIMETALATION OF ARENES BY MEANS OF SUPERBASIC REAGENTS
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If employed in tetrahydrofuran, stoichiometric amounts of butyllithium and potassium tert-butoxide react with benzene under clean monometalation.In hexane suspension, however, considerable amounts of meta- and para-disubstituted by-products are obtained (approx. 10percent).They become preponderant if a three-fold excess of the metalating agent is used.Naphthalene leads under the same conditions to a mixture of two mono- and ten di-substituted derivatives. - Alkyl groups, as present in tert-butylbenzene, retard the metalation at both m- and p-positions, while trialkylsilyl groups deactivate only m-position.In either case exclusive monosubstitution occurs. - Perdeuterobenzene undergoes metalation and subsequent electrophilic mono- or disubstitution to afford isotope labeled compounds with moderate, though synthetically attractive yields.The kinetic isotope effects and product ratios can be taken as evidence for aggregate formation at the level of both the superbasic metalating reagent and the organometallic intermediates.
- Schlosser, Manfred,Choi, Jung Hoon,Takagishi, Sadahito
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p. 5633 - 5648
(2007/10/02)
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- Solution Characterization of Copper(II) and Silver(II) Porphyrins and the One-Electron Oxidation Products by Nuclear Magnetic Resonance Spectroscopy
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The Cu(II) and Ag(II) complexes of tetraphenylporphyrin, octaethylporphyrin, etioporphyrin I, and the one-electron oxidation products of these metalloporphyrin species have been examined by nuclear magnetic resonance (NMR) spectroscopy.Deuterium NMR spect
- Godziela, Gregory M.,Goff, Harold M.
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p. 2237 - 2243
(2007/10/02)
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- Heterocycles from α-Nitroolefins, VII . - 4,5-Dihydro-2-methyl-5-methyleneamino-3-furancarboxylates from α-Nitroolefins, Acetoacetates, and Compounds with an Active Methylene Group
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4,5-Dihydro-2-methyl-5-methyleneamino-3-furancarboxylates 5 are prepared by three preparative methods from α-nitroolefins 1, acetoacetates 2, and compounds with an active methylene group 4 . - For 1H NMR investigations which prove the homoallylic system o
- Boberg, Friedrich,Garburg, Karl-Heinz,Goerlich, Karl-Joachim,Pipereit, Eberhard,Ruhr, Maria
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p. 911 - 919
(2007/10/02)
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