- Non-nanogold catalyzed aerobic oxidation of secondary amines to imines
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Bulk gold powder (~103 nm particle size) is a highly active catalyst for the oxidative dehydrogenation of secondary amines to imines under the mild conditions of 1 atm O2 and 60-100°C. The Royal Society of Chemistry.
- Zhu, Bolin,Angelici, Robert J.
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Read Online
- Aerobic oxidation of methanol by a Ni(II)-O2 reaction
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An unusual oxygen-activating Ni(II)-oximate complex oxidizes two-hydrogen atom donating substrates, including the traditionally inert alcohol, methanol, as well as ethanol, benzyl alcohol, benzylamine, and N-methylbenzylamine.
- Edison, Sara E.,Hotz, Richard P.,Baldwin, Michael J.
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- Precise incorporation of transition metals into organolead oxyhalide crystalline materials for photocatalysis
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Organolead halide crystalline materials are an emerging class of high-performance photocatalysts. However, limited studies have been performed to tune their photoactive properties by precise introduction of transition metals. Herein, we report the success
- Fang, Lei,Fei, Honghan,Ma, Wen,Song, Xueling,Sun, Chen,Zhang, Lu
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Read Online
- Conjugated HCl-doped polyaniline for photocatalytic oxidative coupling of amines under visible light
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HCl-Doped polyaniline (PANI-ES) and PANIs of different oxidation states were prepared by a typical oxidative polymerization and subsequent redox reaction, respectively. The photocatalytic performance of PANIs towards selective benzylamine oxidation reacti
- Kong, Peng,Liu, Pei,Ge, Zhenyu,Tan, Hao,Pei, Linjuan,Wang, Jie,Zhu, Pengqi,Gu, Xianmo,Zheng, Zhanfeng,Li, Zhong
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- Metal-Free Organocatalytic Oxidative Ugi Reaction Promoted by Hypervalent Iodine
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We report here a novel IBX-promoted oxidative coupling of primary amines and its utilization to Ugi reaction. Advantageously, the reaction could be carried out in choline chloride urea as a natural deep eutectic solvent. A range of imines and bisamides fr
- Singh, Karandeep,Kaur, Amanpreet,Mithu, Venus Singh,Sharma, Siddharth
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Read Online
- Visible-Light-Promoted [3 + 2] Cycloaddition of 2H-Azirines with Quinones: Access to Substituted Benzo[f]isoindole-4,9-diones
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A visible-light-promoteded [3 + 2] cycloaddition reaction of 2H-azirines with quinones has been developed under mild reaction conditions. The reaction provides a general and efficient strategy for the synthesis of the benzo[f]isoindole-4,9-diones scaffold
- Wang, Lijia,Liu, Chuang,Li, Lei,Wang, Xin,Sun, Ran,Zhou, Ming-Dong,Wang, He
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supporting information
p. 719 - 724
(2022/01/22)
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- Base-Mediated Generation of Ketenimines from Ynamides: [3+2] Annulation with Azaallyl Anions
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Under basic conditions and heat, ynamides can serve as precursors to ketenimines, whose synthetic potential is often hampered by their difficulty of access. Herein, we report that they can undergo a [3+2] cycloaddition with 2-azaallyl anions, obtained from benzylimines under the same reaction conditions. This reaction between two highly reactive intermediates, both generated in situ from bench stable starting materials, gives access to various nitrogen-rich heterocycles. The reaction usually proceeds with excellent diastereoselectivity, in favor of the cis adduct. Deuteration experiments and DFT calculations helped rationalize the regio- and stereoselectivity of the process as well as the formation of side products. (Figure presented.).
- D'Hollander, Agathe C. A.,Romero, Eugénie,Vijayakumar, Kamsana,Le Houérou, Camille,Retailleau, Pascal,Dodd, Robert H.,Iorga, Bogdan I.,Cariou, Kevin
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supporting information
p. 2903 - 2908
(2021/04/21)
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- C70Fullerene Catalyzed Photoinduced Aerobic Oxidation of Benzylamines to Imines and Aldehydes
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C70 fullerene catalyzed photoinduced oxidation of benzylic amines at ambient conditions has been explored here. The developed strategy's main feature includes the additive/oxidant-free conversion of benzylic amine to corresponding imine and aldehydes. The reaction manifests broad substrate scope with excellent function group leniency and is applicable up to the gram scale. Further, symmetrical secondary amines can also be synthesized from benzylic amine in a one-pot two-step process. Various experiments and density functional theory studies revealed that the current reaction involves the generation of reactive oxygen species, single electron transfer reaction, and benzyl radical formation as key steps under photocatalytic conditions.
- Kumar, Inder,Kumar, Rakesh,Gupta, Shiv Shankar,Sharma, Upendra
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p. 6449 - 6457
(2021/05/29)
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- Copper and N-Heterocyclic Carbene-Catalyzed Oxidative Amidation of Aldehydes with Amines
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A one-pot two-step oxidative process has been developed for the tert-butyl hydroperoxide mediated transformation of aldehydes and amines into amides catalyzed by copper(I) iodide and an N-heterocyclic carbene. The process is additive-free and does not require the amine to be transformed into its hydrochloride salts. The method is simple and practicable, has a broad substrate scope, and uses economical, feasible, and abundant reagents.
- Singh, Ashmita,Narula, Anudeep Kumar
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supporting information
p. 718 - 722
(2021/02/26)
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- Synthesis of chromeno[3,4-b]piperazines by an enol-ugi/reduction/cyclization sequence
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Keto piperazines and aminocoumarins are privileged building blocks for the construction of geometrically constrained peptides and therefore valuable structures in drug discovery. Combining these two heterocycles provides unique rigid polycyclic peptidomimetics with drug-like properties including many points of diversity that could be modulated to interact with different biological receptors. This work describes an efficient multicomponent approach to condensed chromenopiperazines based on the novel enol-Ugi reaction. Importantly, this strategy involves the first reported post-condensation transformation of an enol-Ugi adduct.
- Bornadiego, Ana,Neo, Ana G.,Marcos, Carlos F.
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supporting information
(2021/05/31)
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- Covalent Organic Frameworks toward Diverse Photocatalytic Aerobic Oxidations
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Photoactive two-dimensional covalent organic frameworks (2D-COFs) have become promising heterogenous photocatalysts in visible-light-driven organic transformations. Herein, a visible-light-driven selective aerobic oxidation of various small organic molecules by using 2D-COFs as the photocatalyst was developed. In this protocol, due to the remarkable photocatalytic capability of hydrazone-based 2D-COF-1 on molecular oxygen activation, a wide range of amides, quinolones, heterocyclic compounds, and sulfoxides were obtained with high efficiency and excellent functional group tolerance under very mild reaction conditions. Furthermore, benefiting from the inherent advantage of heterogenous photocatalysis, prominent sustainability and easy photocatalyst recyclability, a drug molecule (modafinil) and an oxidized mustard gas simulant (2-chloroethyl ethyl sulfoxide) were selectively and easily obtained in scale-up reactions. Mechanistic investigations were conducted using radical quenching experiments and in situ ESR spectroscopy, all corroborating the proposed role of 2D-COF-1 in photocatalytic cycle.
- Liu, Shuyang,Tian, Miao,Bu, Xiubin,Tian, Hua,Yang, Xiaobo
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supporting information
p. 7738 - 7744
(2021/05/07)
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- Thiazolo[5,4-d]thiazole-Based Donor–Acceptor Covalent Organic Framework for Sunlight-Driven Hydrogen Evolution
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2D covalent organic frameworks (COFs) could have well-defined arrangements of photo- and electro-active units that serve as electron or hole transport channels for solar energy harvesting and conversion, but their insufficient charge transfer and rapid ch
- Li, Wenqian,Huang, Xiaofeng,Zeng, Tengwu,Liu, Yahu A.,Hu, Weibo,Yang, Hui,Zhang, Yue-Biao,Wen, Ke
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supporting information
p. 1869 - 1874
(2020/12/30)
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- Sulfur-stabilised copper nanoparticles for the aerobic oxidation of amines to imines under ambient conditions
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The stabilisation of metal nanoparticles and control of their oxidation state are crucial factors in nanocatalysis. Elemental sulfur has been found to be a cheap and effective stabilising agent for copper nanoparticles in the form of copper(i) oxide. The
- Martín-García, Iris,Díaz-Reyes, Gloria,Sloan, George,Moglie, Yanina,Alonso, Francisco
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supporting information
p. 11312 - 11322
(2021/05/19)
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- Type I ‘Lighted Metal-free’ Photosensitizing Assemblies of Phenazine for Aerobic Oxidative Transformations
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Highly photostable supramolecular photosensitizing ‘lighted metal-free’ assemblies of DPZ-Th have been developed which show strong absorption in the visible region and excellent electron transportation potential from donor to acceptor units. The as-prepar
- Kaur, Lovjot,Kaur, Harpreet,Kumar, Manoj,Bhalla, Vandana
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supporting information
p. 4179 - 4186
(2021/11/23)
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- A Highly Selective Manganese-Catalyzed Synthesis of Imines under Phosphine-Free Conditions
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An efficient and highly selective phosphine-free NN-manganese(I) complex catalyst system was developed for the acceptorless dehydrogenative coupling of alcohols with amines to form imines. The coupling reactions underwent at 3 mol % catalyst loading, and a large range of alcohols and amines with diverse functional groups was applied, including challenging diol and diamine. The target imine products were obtained in good to excellent yields. The present work provides an alternative method to construct highly active nonprecious metal complex catalysts based on phosphine-free ligands.
- Chai, Huining,Yu, Kun,Liu, Bo,Tan, Weiqiang,Zhang, Guangyao
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p. 217 - 226
(2020/01/31)
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- Non-emissive RuII Polypyridyl Complexes as Efficient and Selective Photosensitizers for the Photooxidation of Benzylamines
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Five new RuII polypyridyl complexes bearing N-(arylsulfonyl)-8-amidoquinolate ligands and three of their biscyclometalated IrIII congeners have been prepared and employed as photocatalysts (PCs) in the photooxidation of benzylamines with O2. In particular, the new RuII complexes do not exhibit photoluminescence, rather they harvest visible light efficiently and are very stable in solution under irradiation with blue light. Their non-emissive behavior has been related to the low electrochemical energy gaps and rationalized on the basis of theoretical calculations (DFT analysis) that predict low S0←T1 energy values. Moreover, the RuII complexes, despite being non-emissive, display excellent activities in the selective photocatalytic transformation of benzylamines into the corresponding imines. The presence of an electron-withdrawing group (-CF3) on the arene ring of the N-(arylsulfonyl)-8-amidoquinolate ligand improves the photocatalytic activity of the corresponding photocatalyst. Furthermore, all the experimental evidence, including transient absorption spectroscopy measurements suggest that singlet oxygen is the actual oxidant. The IrIII analogues are considerably more photosensitive and consequently less efficient photosensitizers (PSs).
- Yagüe, Cristina,Echevarría, Igor,Vaquero, Mónica,Fidalgo, Jairo,Carbayo, Arancha,Jalón, Félix A.,Lima, Jo?o C.,Moro, Artur J.,Manzano, Blanca R.,Espino, Gustavo
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supporting information
p. 12219 - 12232
(2020/09/01)
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- The Hofmann reaction involving annulation of: O -(pyridin-2-yl)aryl amides selectively and rapidly leads to potential photocatalytically active 6 H -pyrido[1,2- c] quinazolin-6-one derivatives
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A highly efficient PIFA-mediated Hofmann reaction of o-(pyridin-2-yl)aryl amides has been developed to selectively and rapidly construct various potential photocatalytically active 6H-pyrido[1,2-c]quinazolin-6-one derivatives. The use of a nontoxic and ec
- Gao, Wenjing,Liu, Tongxin,Wan, Yameng,Wu, Hao,Zhang, Guisheng,Zhang, Zhiguo
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supporting information
p. 7955 - 7961
(2020/11/30)
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- Single Atomically Anchored Cobalt on Carbon Quantum Dots as Efficient Photocatalysts for Visible Light-Promoted Oxidation Reactions
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Generation of efficient light-induced charge separation inside the photocatalyst is an essential factor for a high catalytic efficiency. The usual immobilization of metal or metal oxide particles on semiconductor photocatalysts offers an uncontrolled assembly of active sites during the reaction. The introduction of single metal atoms on photocatalysts can lead to extremely high atomic utilization and precise active sites. However, this approach is limited because of the lack of suitable photosensitizers for single atom immobilization. Here, we have designed photocatalytic carbon quantum dots with anchoring sites for single cobalt atoms in a defined Co-N4 structure via facile pyrolysis of vitamin B12. Carbon dots functioned as both light-harvesting antenna and support for the cobalt atom with high atom loadings up to 3.27 wt %. This new photocatalytic material demonstrated enhanced visible light absorption, efficient charge separation, and reduced electrochemical impedance, while single Co atoms acted as the active site with strong oxidative ability. As a result, the photocatalysts showed excellent visible light-promoted photocatalytic efficiency with oxygen evolution rates up to 168 μmol h-1 g-1 via water oxidation, imine formation with high conversion (~90%) and selectivity (>99%), and complete photodegradation of organic dyes.
- Wang, Qin,Li, Jin,Tu, Xianjun,Liu, Hongbo,Shu, Miao,Si, Rui,Ferguson, Calum T. J.,Zhang, Kai. A. I.,Li, Run
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p. 734 - 743
(2020/02/04)
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- Acceptorless dehydrogenative construction of CN and CC bonds through catalytic aza-Wittig and Wittig reactions in the presence of an air-stable ruthenium pincer complex
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The construction of CN bonds was achieved by the dehydrogenative coupling of alcohol and azide via aza-Wittig type reaction. The reaction is catalyzed by an acridine-derived ruthenium pincer complex and does not use any oxidant. The present protocol offers a wide substrate scope, including aliphatic, aryl or heteroaryl alcohol/azides. This expeditious protocol was successfully applied to construct a CC bond directly from alcohol via dehydrogenative Wittig reaction. Furthermore, the synthesis of structurally important pyrrolo[1,4]benzodiazepine derivatives was also achieved by this methodology.
- Biswas, Nandita,Das, Kalicharan,Sardar, Bitan,Srimani, DIpankar
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p. 6501 - 6512
(2019/05/24)
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- Improving C=N bond reductions with (Cyclopentadienone)iron complexes: Scope and limitations
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Herein, we broaden the application scope of (cyclo-pentadienone)iron complexes 1 in C=N bond reduction. The catalytic scope of pre-catalyst 1b, which is more active than the “Kn?lker complex” (1a) and other members of its family, has been expanded to the catalytic transfer hydrogenation (CTH) of a wider range of aldimines and ketimines, either pre-isolated or generated in situ. The kinetics of 1b-promoted CTH of ketimine S1 were assessed, showing a pseudo-first order profile, with TOF = 6.07 h–1 at 50 % conversion. Moreover, the chiral complex 1c and its analog 1d were employed in the enantioselective reduction of ketimines and reductive amination of ketones, giving fair to good yields and moderate enantioselectivity.
- Cettolin, Mattia,Bai, Xishan,Lübken, Dennis,Gatti, Marco,Facchini, Sofia Vailati,Piarulli, Umberto,Pignataro, Luca,Gennari, Cesare
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supporting information
p. 647 - 654
(2018/10/24)
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- Nucleophilic Imines and Electrophilic o-Quinone Methides, a Three-Component Assembly of Assorted 3,4-Dihydro-2 H-1,3-benzoxazines
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A one-pot method for joining three separate components leading to an assortment of N-substituted 3,4-dihydro-2H-1,3-benzoxazines is described. The method involves the addition of a Grignard reagent to an o-OBoc salicylaldehyde in the presence of an imine. With a variety of components, 15 examples are presented, including the diastereoselective incorporation of chiral imines.
- Chen, Peishan Kc,Wong, Yuk Fai,Yang, Derek,Pettus, Thomas R. R.
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supporting information
p. 7746 - 7749
(2019/10/11)
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- Suspending Ion Electrocatalysts in Charged Metal–Organic Frameworks to Improve the Conductivity and Selectivity in Electroorganic Synthesis
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Electroorganic synthesis is an environmentally friendly alternative to traditional synthetic methods; however, the application of this strategy is heavily hindered by low product selectivity. Metal–organic frameworks (MOFs) exhibit high selectivity in numerous catalytic reactions; however, poor conductivity heavily limits the application of MOFs in electroorganic synthesis. To realize the electrocatalytic application of MOFs in selective electroorganic synthesis, a practically applicable strategy by suspending ion electrocatalysts in charged MOFs is herein reported. This approach could markedly improve the product selectivity in electroorganic synthesis. In the electrocatalytic oxidative self-coupling of benzylamine experiments, the imine product selectivity is markedly improved from 61.3 to 94.9 %, when the MOF-based electrocatalyst is used instead of the corresponding homogeneous electrocatalyst under the identical conditions. Therefore, this work opens a new route to improve the product selectivity in electroorganic synthesis.
- Guo, Wei-Wei,Zhang, Chi,Ye, Ji-Jie,Liu, Zi-Kun,Chen, Kai,Wu, Chuan-De
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p. 3627 - 3634
(2019/07/31)
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- Photoorganocatalytic Aerobic Oxidative Amine Dehydrogenation/Super Acid-Mediated Pictet-Spengler Cyclization: Synthesis of cis-1,3-Diaryl Tetrahydroisoquinolines
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Aerobic oxidative dehydrogenation reactions of benzylamines to imines were studied and the efficiencies of various ground- and excited state quinone organocatalysts were compared. Long wave-absorbing anthraquinones readily catalyze the aerobic photodehydr
- Unkel, Lisa-Natascha,Malcherek, Simon,Schendera, Eva,Hoffmann, Frank,Rehbein, Julia,Brasholz, Malte
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supporting information
p. 2870 - 2876
(2019/05/01)
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- Aerobic Oxidation of Primary Amines to Imines in Water using a Cobalt Complex as Recyclable Catalyst under Mild Conditions
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Oxidative coupling of primary amines to imines has been achieved by using a water soluble cobalt complex as catalyst and air as the oxidant at near ambient conditions. Aromatic, heteroaromatic and aliphatic amines were successfully converted to the corresponding imines with yields of up to 96 %. A 20 gram scale reaction for the synthesis of imine from benzylamine in good yield is also demonstrated with this method. The catalyst has been found to be reusable with up to five cycles. It is highly efficient, gives a turnover number (TON) of up to 128, and shows chemoselectivity with the only byproducts being water and ammonia. Control experiments and mechanistic studies indicate that the CoII/CoIII catalytic cycle is responsible for these oxidative transformations. Some of the reactive intermediates of this reaction have also been isolated and structurally characterized.
- Hazra, Susanta,Pilania, Priti,Deb, Mayukh,Kushawaha, Ajay Kishor,Elias, Anil J.
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p. 15766 - 15771
(2018/10/09)
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- Method for Selective Oxidation of Amines Using Two Dimensional Heterogeneous Nano-catalysts with Ruthenium Dispersed on Exfoliated Sheets of Molybdenum Disulfide
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Disclosed is a method for selectively oxidizing an amine-based compound to convert the same into compounds such as nitrile using a two-dimensional heterogeneous nanocatalyst containing ruthenium supported, at high dispersion rate, on an exfoliated layer of molybdenum disulfide which is a layered transition metal dichalcogenide (LTMD).COPYRIGHT KIPO 2019
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Paragraph 0114; 0115; 0133; 0134; 0135
(2019/03/13)
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- Aerobic Oxidative Homo- and Cross-Coupling of Amines Catalyzed by Phenazine Radical Cations
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Phenazine radical cations (PhRCs) were used for the first time as efficient metal-free catalysts for the oxidative homo- and cross-coupling of a variety of different amines. A series of functional PhRCs were prepared, characterized with X-ray diffraction, and their radical character was investigated with DFT calculations. They were tested as catalysts under neat conditions with low oxygen pressure to prepare homo- and cross-coupled aliphatic and aromatic imines in high yields. Although all synthesized phenazines were catalytically active, the highest reaction rates and the best selectivity were achieved using the 5,10-dihydro-5,10-dimethylphenazine radical cation. By means of fluorescence, UV-vis and EPR spectroscopy, a mechanism of the oxidative amine coupling, catalyzed by PhRCs, is proposed.
- Bri?ar, Rok,Unglaube, Felix,Hollmann, Dirk,Jiao, Haijun,Mejía, Esteban
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p. 13481 - 13490
(2018/11/02)
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- Main-Group-Catalyzed Reductive Alkylation of Multiply Substituted Amines with Aldehydes Using H2
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Given the growing demand for green and sustainable chemical processes, the catalytic reductive alkylation of amines with main-group catalysts of low toxicity and molecular hydrogen as the reductant would be an ideal method to functionalize amines. However, such a process remains challenging. Herein, a novel reductive alkylation system using H2 is presented, which proceeds via a tandem reaction that involves the B(2,6-Cl2C6H3)(p-HC6F4)2-catalyzed formation of an imine and the subsequent hydrogenation of this imine catalyzed by a frustrated Lewis pair (FLP). This reductive alkylation reaction generates H2O as the sole byproduct and directly functionalizes amines that bear a remarkably wide range of substituents including carboxyl, hydroxyl, additional amino, primary amide, and primary sulfonamide groups. The synthesis of isoindolinones and aminophthalic anhydrides has also been achieved by a one-pot process that consists of a combination of the present reductive alkylation with an intramolecular amidation and intramolecular dehydration reactions, respectively. The reaction showed a zeroth-order and a first-order dependence on the concentration of an imine intermediate and B(2,6-Cl2C6H3)(p-HC6F4)2, respectively. In addition, the reaction progress was significantly affected by the concentration of H2. These results suggest a possible mechanism in which the heterolysis of H2 is facilitated by the FLP comprising THF and B(2,6-Cl2C6H3)(p-HC6F4)2.
- Hoshimoto, Yoichi,Kinoshita, Takuya,Hazra, Sunit,Ohashi, Masato,Ogoshi, Sensuke
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supporting information
p. 7292 - 7300
(2018/06/01)
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- Carbazole-triazine based donor-acceptor porous organic frameworks for efficient visible-light photocatalytic aerobic oxidation reactions
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We report the synthesis of a series of carbazole-triazine based donor-acceptor (D-A) POFs and their photocatalytic activities for aerobic oxidation reactions. The simultaneous introduction of a carbazole-based electron donor and a triazine-based electron acceptor in D-A POFs stabilizes the charge transfer state and enables an efficient triplet-triplet energy transfer to generate 1O2. Meanwhile, systematic variation of the D-A distance results in the tunable photoredox properties and consequently the efficiency for generation of reactive oxygen species (ROSs). Upon visible light excitation, all three D-A POFs exhibit excellent capability to promote three aerobic oxidations: sulfide oxidation, oxidative amine coupling, and Mannich reactions. This systematic study validates the design principle of D-A POFs as high-performance photo-oxidation catalysts with wide substrate scope and excellent stability and recyclability.
- Luo, Jian,Lu, Jingzhi,Zhang, Jian
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supporting information
p. 15154 - 15161
(2018/08/17)
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- Efficient and recyclable Ir(i)-catalysts with the involvement of π-acceptor phosphines for N-alkylation of aryl amines with alcohols
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Mono-phosphines (L1 and L2) and diphosphines (L3 and L4) with typical π-acceptor character were prepared and applied in Ir(i)-catalyzed N-alkylation of amines with alcohols. It was found that the π-acceptor character of the applied phosphines is closely c
- Liu, Huan,Wang, Dong-Liang,Chen, Xia,Lu, Yong,Zhao, Xiao-Li,Liu, Ye
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p. 1109 - 1116
(2017/08/18)
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- A metallopeptoid as an efficient bioinspired cooperative catalyst for the aerobic oxidative synthesis of imines
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Enzymatic catalysis is largely based on intramolecular cooperativity between a metal center and functional organic molecules located on one scaffold. Inspired by this concept we have designed the metallopeptoid trimer BT, which is a unique intramolecular cooperative oxidation catalyst incorporating two catalytic centers, phenanthroline-copper and TEMPO, as well as one non-catalytic benzyl group. Herein we explore the capability of BT to act as an efficient catalyst for the oxidative synthesis of imines, which are versatile intermediates in the fine chemicals and pharmaceutical industries. We demonstrate that BT, combined with CuI, can catalyze the production of benzyl, aryl, heteroaryl, allylic and aliphatic imines from various alcohols and amines with a turn-over-number up to 45 times higher than this achieved when phenanthroline, copper and TEMPO are mixed in solution. Moreover, in low catalyst(s) loading, BT enables transformations that are not possible when a mixture of the individual catalysts is employed.
- Chandra Mohan, Darapanani,Sadhukha, Arghya,Maayan, Galia
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p. 139 - 144
(2017/10/16)
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- Tris(2,4,6-trifluorophenyl)borane: An Efficient Hydroboration Catalyst
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The metal-free catalyst tris(2,4,6-trifluorophenyl)borane has demonstrated its extensive applications in the 1,2-hydroboration of numerous unsaturated reagents, namely alkynes, aldehydes and imines, consisting of a wide array of electron-withdrawing and donating functionalities. A range of over 50 borylated products are reported, with many reactions proceeding with low catalyst loading under ambient conditions. These pinacol boronate esters, in the case of aldehydes and imines, can be readily hydrolyzed to leave the respective alcohol and amine, whereas alkynyl substrates result in vinyl boranes. This is of great synthetic use to the organic chemist.
- Lawson, James R.,Wilkins, Lewis C.,Melen, Rebecca L.
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supporting information
p. 10997 - 11000
(2017/08/22)
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- O-Naphthoquinone-Catalyzed Aerobic Oxidation of Amines to (Ket)imines: A Modular Catalyst Approach
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A modular aerobic oxidation of amines to imines has been achieved using an ortho-naphthoquinone (o-NQ) catalyst. The cooperative catalyst system of o-NQ and Cu(OAc)2 enabled the formation of homocoupled imines from benzylamines, while the presence of TFA helped the formation of cross-coupled imines in excellent yields. The current mild aerobic oxidation protocol could also be applied to the oxidation of secondary amines to imines or ketimines with the help of cocatalyst, Ag2CO3, with excellent yields.
- Goriya, Yogesh,Kim, Hun Young,Oh, Kyungsoo
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supporting information
p. 5174 - 5177
(2016/10/14)
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- Trans-Symmetric Dynamic Covalent Systems: Connected Transamination and Transimination Reactions
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The development of chemical transaminations as a new type of dynamic covalent reaction is described. The key 1,3-proton shift is under complete catalytic control and can be conducted orthogonally to, or simultaneous with, transimination in the presence of an amine to rapidly yield two-dimensional dynamic systems with a high degree of complexity evolution. The transamination-transimination systems are proven to be fully reversible, stable over several days, compatible with a range of functional groups, and highly tunable. Kinetic studies show transamination to be the rate-limiting reaction in the network. Furthermore, it was discovered that readily available quinuclidine is a highly potent catalyst for aldimine transaminations. This study demonstrates how connected dynamic reactions give rise to significantly larger systems than the unconnected counterparts, and shows how reversible isomerizations can be utilized as an effective diversity-generating element. Constant exchange: The development of chemical transaminations as a new type of dynamic covalent reactions is described (see figure). This study demonstrates how connected dynamic reactions give rise to significantly larger systems than the unconnected counterparts, and shows how reversible isomerizations can be utilized as an effective diversity-generating element.
- Schaufelberger, Fredrik,Hu, Lei,Ramstr?m, Olof
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supporting information
p. 9776 - 9783
(2015/06/30)
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- Photoredox-Catalyzed Reductive Coupling of Aldehydes, Ketones, and Imines with Visible Light
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Ketyl radical and amino radical anions, valuable reactive intermediates for C-C bond-forming reactions, are accessible through a C=O/C=NR umpolung. However, their utilization in catalysis remains largely underdeveloped owing to the high reduction potential of carbonyl compounds and imines. In the context of photoredox catalysis, tertiary amines are commonly employed as sacrificial co-reducing agents. Herein, an additional role of the amine is proposed, in which it is essential for the organocatalytic substrate activation. The combination of photoredox catalysis and carbonyl/imine activation enables the reductive coupling of aldehydes, ketones, and imines under mild reaction conditions.
- Nakajima, Masaki,Fava, Eleonora,Loescher, Sebastian,Jiang, Zhen,Rueping, Magnus
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supporting information
p. 8828 - 8832
(2015/11/27)
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- Bioinspired organocatalytic aerobic C-H oxidation of amines with an ortho -quinone catalyst
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A simple bioinspired ortho-quinone catalyst for the aerobic oxidative dehydrogenation of amines to imines is reported. Without any metal cocatalysts, the identified optimal ortho-quinone catalyst enables the oxidations of α-branched primary amines and cyclic secondary amines. Mechanistic studies have disclosed the origins of different performances of ortho-quinone vs para-quinone in biomimetic amine oxidations.
- Qin, Yan,Zhang, Long,Lv, Jian,Luo, Sanzhong,Cheng, Jin-Pei
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supporting information
p. 1469 - 1472
(2015/03/30)
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- Organocatalyzed and uncatalyzed C=C/C=C and C=C/C=N exchange processes between knoevenagel and imine compounds in dynamic covalent chemistry
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Molecular diversity generation through reversible component exchange has acquired great importance in the last decade with the development of dynamic covalent chemistry. We explore here the recombination of components linked by C=C and C=N bonds through reversible double-bond formation, and cleavage in C=C/C=C and C=C/C=N exchange processes. The reversibility of the Knoevenagel reaction has been explored, and C=C/C=C C/C exchanges have been achieved among different benzylidenes, under organocatalysis by secondary amines such as L-proline. The substituents of these benzylidenes were shown to play a very important role in the kinetics of the exchange reactions. L-Proline is also used to catalyze the reversible C=C/C=C exchange between Knoevenagel derivatives of barbituric acid and malononitrile. Finally, the interconversion between Knoevenagel derivatives of dimethylbarbituric acid and imines (C=C/C=N exchange) has been studied and was found to occur rapidly in the absence of catalyst. The results of this study pave the way for the extension of dynamic combinatorial chemistry based on C=C/C=C and C=C/C=N exchange systems.
- Kulchat, Sirinan,Meguellati, Kamel,Lehn, Jean-Marie
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p. 1219 - 1236
(2015/04/14)
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- Ionic-liquid-assisted metal-free oxidative coupling of amines to give imines
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An oxidative coupling of amines to give imines in ionic liquids (ILs) under metal-free aerobic conditions has been developed. The high efficiency achievable in ILs is mechanistically explained in terms of activation of the starting materials (benzylamine and molecular oxygen) by an initial electron transfer, promoted by the ionic nature of the solvent. Reactivity data of variously p-substituted benzylamines show a general deactivating effect, which would imply a change in the rate-determining step in the reaction mechanism.
- Monopoli, Antonio,Cotugno, Pietro,Iannone, Francesco,Ciminale, Francesco,Dell'Anna, Maria Michela,Mastrorilli, Piero,Nacci, Angelo
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supporting information
p. 5925 - 5931
(2015/03/30)
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- A Ru-catalyzed one-pot synthesis of homopropargylic amines from alkyl azides under photolytic conditions
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A new synthetic method for homopropargylic amines from alkyl azides is presented. A salient feature of this reaction is the involvement of N-unsubstituted imines as the key intermediates, which are generated from alkyl azides by Ru catalysis under photoly
- Jeong, Wook,Lee, Ji Hyung,Kim, Jungjoon,Lee, Won Jong,Seong, Ju-Hwa,Park, Jaiwook,Rhee, Young Ho
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p. 20632 - 20635
(2014/06/09)
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- Consecutive oxygen-based oxidations convert amines to α-cyanoepoxides
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Tri- or tetrasubstituted α-cyanoepoxides can be rapidly prepared from unactivated amines and malononitrile or methyl cyanoacetate when singlet oxygen, produced in a continuous-flow photoreactor, serves as an oxidant and in situ peroxide source. The hydrogen peroxide generated in amine oxidation epoxidizes an electron deficient olefin intermediate, formed by deaminative Mannich coupling. The corresponding α,α-dicyano- or α-cyano-α-esterepoxides were obtained in good yields (43-82%). This journal is
- Ushakov, Dmitry B.,Gilmore, Kerry,Seeberger, Peter H.
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supporting information
p. 12649 - 12651
(2015/05/20)
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- Access to 1,2-dihydroisoquinolines through gold-catalyzed formal [4+2] cycloaddition
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A new synthetic route to the privileged 1,2-dihydroisoquinolines is reported. This method, which relies on a gold-catalyzed formal [4+2] cycloaddition between ynamides and imines, provides a new retrosynthetic disconnection of the 1,2-dihydroisoquinoline core by installing the 1,8a C-C and 2,3 C-N bonds in one step. Both aldimines and ketimines can be used as substrates. In addition, one example of dihydrofuropyridine synthesis is also demonstrated. Heterocycles: A new synthetic route to the privileged 1,2-dihydroisoquinolines is reported. This method, which relies on a gold-catalyzed formal [4+2] cycloaddition between ynamides and imines, provides a new retrosynthetic disconnection of the 1,2-dihydroisoquinoline core by installing the 1,8a C-C and 2,3 C-N bonds in one step. Both aldimines and ketimines can be used as substrates. In addition, one example of dihydrofuropyridine synthesis is also demonstrated (see scheme).
- Xin, Zhuo,Kramer, Soren,Overgaard, Jacob,Skrydstrup, Troels
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supporting information
p. 7926 - 7930
(2014/07/07)
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- Synthesis of azetidines and pyrrolidines via iodocyclisation of homoallyl amines and exploration of activity in a zebrafish embryo assay
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Room temperature iodocyclisation of homoallylamines stereoselectively delivers functionalised 2-(iodomethyl)azetidine derivatives in high yield. Increasing reaction temperature from 20 °C to 50°C switches the reaction outcome to realise the stereoselectiv
- Feula, Antonio,Dhillon, Sundeep S.,Byravan, Rama,Sangha, Mandeep,Ebanks, Ronald,Hama Salih, Mariwan A.,Spencer, Neil,Male, Louise,Magyary, Istvan,Deng, Wei-Ping,Müller, Ferenc,Fossey, John S.
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supporting information
p. 5083 - 5093
(2013/08/23)
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- Organocatalysis of c?£/c?£N and C?£C/ C?£N exchange in dynamic covalent chemistry
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The reversibly formed C?£N bond plays a very important role in dynamic covalent chemistry and the C?£N/C?£N exchange of components between different imine constituents to create dynamic covalent libraries has been extensively used. To facilitate diversity generation, we have investigated an organocatalyzed approach, using L-proline as catalyst, to accelerate the formation of dynamic libraries of [n×n] imine components. The organocatalysis methodology has also been extended, under somewhat modified conditions, to reversible C?£C/C?£N exchange processes between Knoevenagel derivatives of barbituric acid and imines, allowing for the generation of increased diversity. Copyright
- Wilhelms, Nadine,Kulchat, Sirinan,Lehn, Jean-Marie
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p. 2635 - 2651
(2013/03/13)
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- Straightforward synthesis of aromatic imines from alcohols and amines or nitroarenes using an impregnated copper catalyst
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The impregnated copper on magnetite catalyst is a versatile system for the synthesis of imines starting from alcohols and amines. This catalyst does not require any type of expensive and difficult to handle organic ligand or typical transition metals, and provides excellent yields achievable under mild reaction conditions. Moreover, the catalyst is very easy to remove from the reaction medium by simply using a magnet. The one-pot process of dehydrogenation of alcohols in the presence of aniline followed by aqueous hydrolysis gave pure alcohols in excellent yields. In addition to amines, nitroarenes could be used as the nitrogen-containing reagent. In the case of primary amines the expected imines were successfully prepared under similar reaction conditions. The impregnated copper on magnetite catalyst is a versatile system for the synthesis of imines starting from alcohols and amines or nitroarenes. A similar synthesis of imines was accomplished using only primary amines. This catalyst avoids the use of expensive organic ligands and other transition metals while enabling excellent yields under mild reaction conditions. Copyright
- Perez, Juana M.,Cano, Rafael,Yus, Miguel,Ramon, Diego J.
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p. 4548 - 4554
(2012/11/07)
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- Copper-catalyzed aerobic oxidation of amines to imines under neat conditions with low catalyst loading
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The copper (I)-catalyzed direct synthesis of imines from amines under mild aerobic conditions is described. The method is applicable for the synthesis of various imines from corresponding amines such as benzylic, aliphatic, cyclic secondary, heteroaromatic species and the oxidative condensation of benzylamines with anilines extends the scope of the CuCl catalytic system. Noteworthy, solvent-free procedure, air as a benign oxidant, and the cheap and easy availability of the catalyst are the vital advantages of the method. Copyright
- Patil, Rajendra D.,Adimurthy, Subbarayappa
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supporting information; experimental part
p. 1695 - 1700
(2011/09/14)
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- An effective method to prepare imines from aldehyde, bromide/epoxide, and aqueous ammonia
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A three-component reaction of aldehydes, alkyl bromides, and ammonia to form imines was studied. Aqueous ammonia was applied as the nitrogen source and solvent in the reaction. For the aromatic aldehyde, the product yields are good to excellent and the reaction conditions are mild to be compatible with a range of functional groups. The reaction of aldehydes and aqueous ammonia with epoxides was also studied and imines bearing a vicinal hydroxyl group can be obtained efficiently and regioselectively. And studies showed that this method allows the synthesis of primary amines and especially 1,2-amino alcohol selectively in high yield. It is proposed that the reaction pathway might involve a key intermediate of hydrobenzamide.
- Huang, Jing-Mei,Zhang, Jue-Fei,Dong, Yi,Gong, Wen
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p. 3511 - 3514
(2011/06/22)
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- Activation of the Si-B Linkage: Copper-Catalyzed addition of nucleophilic silicon to imines
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Activation of the Si-B bond through copper-catalyzed transmetalation quickly developed into a practical method to generate Cu-Si reagents These silicon nucleophiles cleanly add to aldehyde-derived imine electrophiles to form R-silylated amines in protic media, and no carbon-tonitrogen Brook-type rearrangement of the intermediate anion is observed. Aside from electron-withdrawing groups at the imine nitrogen atom, for example, SO2Tol and P(O)Ph2, previously delicate nitrogen substituents such as phenyl or benzhydryl are tolerated. The same protocol also allows the unprecedented addition to representative ketone-derived imines.
- Vyas, Devendra J.,Froehlich, Roland,Oestreich, Martin
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supporting information; experimental part
p. 2094 - 2097
(2011/06/22)
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- N -(2-Pyridylmethyl)imines as azomethine precursors in catalytic asymmetric [3 + 2] cycloadditions
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An efficient Cu(I)-catalyzed asymmetric [3 + 2] cycloaddition of N-(2-pyridylmethyl) imines has been developed. In the presence of a Cu(CH 3CN)4PF6/bisoxazoline catalyst system, high levels of enantioselectivity (up to 97% ee) and moderate to high exo selectivity were achieved with a wide variety of substituted dipolarophiles, including maleimides, fumarates, fumarodinitrile, enones, and nitroalkenes. The reaction with unsymmetrically substituted dipolarophiles is completely regioselective.
- Padilla, Silvia,Tejero, Ruben,Adrio, Javier,Carretero, Juan C.
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supporting information; experimental part
p. 5608 - 5611
(2011/03/20)
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- Dynamic kinetic asymmetric synthesis of substituted pyrrolidines from racemic cyclopropanes and aldimines: Reaction development and mechanistic insights
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An enantioselective preparation of 2,5-cis-disubstituted pyrrolidines has been achieved via a dynamic kinetic asymmetric transformation (DyKAT) of racemic donor-acceptor cyclopropanes and (E)-aldimines. Mechanistic studies suggest that isomerization of the aldimine or resultant iminium to the Z geometry is not a pathway that furnishes the observed 2,5-cis-disubstituted products.
- Parsons, Andrew T.,Smith, Austin G.,Neel, Andrew J.,Johnson, Jeffrey S.
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supporting information; experimental part
p. 9688 - 9692
(2010/09/06)
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- Organometallic chemistry and catalysis on gold metal surfaces
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As in transition metal complexes, C{triple bond, long}N-R ligands adsorbed on powdered gold undergo attack by amines to give putative diaminocarbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of C{triple bond, long}N-R, primary amines (R′NH2) and O2 to give carbodiimides (R′-N{double bond, long}C{double bond, long}N-R). An analogous reaction of C{triple bond, long}O, RNH2, and O2 gives isocyanates (R-N{double bond, long}C{double bond, long}O), which react with additional amine to give urea (RNH)2C{double bond, long}O products. The gold-catalyzed reaction of C{triple bond, long}N-R with secondary amines (HNR′2) and O2 gives mixed ureas RNH(C{double bond, long}O)NR′2. In another type of gold-catalyzed reaction, secondary amines HN(CH2R)2 react with O2 to undergo dehydrogenation to the imine product, RCH{double bond, long}N(CH2R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.
- Angelici, Robert J.
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p. 847 - 856
(2008/03/30)
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- Environmentally friendly chemoselective oxidation of primary aliphatic amines by using a biomimetic eiectrocatalytic system
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Environmentally friendly oxidation of primary aliphatic amines to imines has been successfully achieved, under metal-free conditions, by the use of diverse electrogenerated o-azaqui-none mediators. High catalytic performance, together with high chemoselec
- Largeron, Martine,Chiaroni, Angele,Fleury, Maurice-Bernard
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p. 996 - 1003
(2008/09/21)
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- Aerobic ruthenium-catalyzed oxidative transformation of secondary amines to imines
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Aerobic, catalytic oxidation of secondary amines is performed efficiently in the presence of a diruthenium complex catalyst Ru2(OAc) 4Cl to give the corresponding imines. The catalytic system is characterized by its high selectivity, activity, and operational simplicity. Georg Thieme Verlag Stuttgart.
- Murahashi, Shun-Ichi,Okano, Yuriko,Sato, Hideomi,Nakae, Takahiro,Komiya, Naruyoshi
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p. 1675 - 1678
(2007/12/29)
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- Regulation of orthogonal functions in a dual catalyst system. Subservient role of a nonchiral lewis acid in an asymmetric catalytic heteroatom Diels-Alder reaction
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A catalytic asymmetric heteroatom Diels-Alder reaction of unactivated imines with Danishefsky's diene is described which gives high asymmetric induction for N-benzhydryl imines derived from a variety of aldehydes. The catalyst is derived from B(OPh)3 and the VAPOL ligand and gives good induction, but the reaction stalls and does not give high conversion (~50%). It was found that in the presence of both the chiral catalyst and excess amounts of B(OPh)3 the reaction proceeds to completion and gives high yields of the dihydropiperidinone product. Despite the presence of large quantities of the nonchiral Lewis acid B(OPh)3, the asymmetric induction of the product remains constant (90% ee) as the amount of B(OPh)3 is steadily increased and does not drop off until the ratio of B(OPh)3 to VAPOL is 100:1 (82% ee). These observations are interpreted as involving highly separated and different activities for the chiral and nonchiral Lewis acids present in the reaction. Specifically, the excess B(OPh)3 serves to bind to the product and release the chiral catalyst to turnover more starting material. The B(OPh)3 does not compete in turning over the starting material, and a series of binding studies reveal that this is likely due to a combination of two factors. The binding studies reveal that the chiral catalyst binds to the starting imine 7 times more strongly than does B(OPh)3. However, in order to explain the constant asymmetric induction observed despite the addition of increasing amounts of B(OPh)3, the rate of the reaction of the imine complexed with the chiral catalyst must be at least 10 times faster than the reaction of the imine complexed with B(OPh)3. Finally, a catalyst generated from BINOL and B(OPh)3 does not show this phenomenon. Copyright
- Newman, Cory A.,Antilla, Jon C.,Chen, Pei,Predeus, Alexander V.,Fielding, Lee,Wulff, William D.
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p. 7216 - 7217
(2008/02/06)
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