- C-H and O2Activation at a Pt(II) Center enabled by a novel sulfonated CNN pincer ligand
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A novel sulfonated CNN pincer ligand has been designed to support CH and O2 activation at a Pt(II) center. The derived cycloplatinated aqua complex 7 was found to be one of the most active reported homogeneous Pt catalysts for H/D exchange between studied arenes (benzene, benzene-d6, toluene-d8, p-xylene, and mesitylene) and 2,2,2-trifluoroethanol (TFE) or 2,2,2- trifluoroethanol-d; the TON for C6D6 as a substrate is >250 after 48 h at 80 °C. The reaction is very selective; no benzylic CH bond activation was observed. The per-CH-bond reactivity diminishes in the series benzene (19) > toluene (p-CH:m-CH:o-CH = 1:0.9:0.2) > xylene (2.9) > mesitylene (1.1). The complex 7 reacts slowly in TFE solutions under ambient light but not in the dark with O2 to selectively produce a Pt(IV) trifluoroethoxo derivative. The H/D exchange reaction kinetics and results of the DFT study suggest that complex 7, and not its TFE derivatives, is the major species responsible for the arene CH bond activation. The reaction deuterium kinetic isotope effect, kH/kD = 1.7, the reaction selectivity, and reaction kinetics modeling suggest that the CH bond cleavage step is rate-determining.
- Watts, David,Wang, Daoyong,Adelberg, Mackenzie,Zavalij, Peter Y.,Vedernikov, Andrei N.
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Read Online
- Borenium-Catalyzed Reduction of Pyridines through the Combined Action of Hydrogen and Hydrosilane
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Mesoionic carbene-stabilized borenium ions efficiently reduce substituted pyridines to piperidines in the presence of a hydrosilane and a hydrogen atmosphere. Control experiments and deuterium labeling studies demonstrate reversible hydrosilylation of the pyridine, enabling full reduction of the N-heterocycle under milder conditions. The silane is a critical reaction component to prevent adduct formation between the piperidine product and the borenium catalyst.
- Clarke, Joshua J.,Maekawa, Yuuki,Nambo, Masakazu,Crudden, Cathleen M.
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supporting information
p. 6617 - 6621
(2021/09/02)
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- Bathocuproine-Enabled Nickel-Catalyzed Selective Ullmann Cross-Coupling of Two sp 2-Hybridized Organohalides
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Cross-coupling reactions are essential for the synthesis of complex organic molecules. Here, we report a nickel-catalyzed Ullmann cross-coupling of two sp 2-hybridized organohalides, featuring high cross-selectivity when the two coupling partners are used in a 1:1 ratio. The high chemoselectivity is governed by the bathocuproine ligand. Moreover, the mild reductive reaction conditions allow that a wide range of functional groups are compatible in this Ullmann cross-coupling.
- Li, Yuqiang,Yin, Guoyin
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supporting information
p. 1657 - 1661
(2021/09/13)
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- Ni-catalyzed reductive decyanation of nitriles with ethanol as the reductant
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A nickel-catalyzed reductive decyanation of aromatic nitriles has been developed, in which the readily available and abundant ethanol was applied as the hydride donor. Various functional groups on the aromatic rings, such as alkoxyl, amino, imino and amide, were compatible in this catalytic protocol. Heteroaryl, benzylic and alkenyl nitriles were also tolerated. Mechanistic investigation indicated that ethanol provided hydride efficientlyviaβ-hydride elimination in this reductive decyanation.
- Wu, Ke,Ling, Yichen,Sun, Nan,Hu, Baoxiang,Shen, Zhenlu,Jin, Liqun,Hu, Xinquan
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supporting information
p. 2273 - 2276
(2021/03/09)
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- Meta-dehydrogenative alkylation of arenes with ethers, ketones, and esters catalyzed by ruthenium
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A meta-dehydrogenative alkylation of arenes with cyclic ethers, ketones, and esters catalyzed by ruthenium is achieved in the presence of a di-tert-butyl peroxide (DTBP) oxidant. Interestingly, when quinoline and isoquinoline are employed as the directing group, or a chain ether as alkylation reagent, the system produces Minisci reaction products. Mechanistic study indicates that meta-dehydrogenative alkylation is a radical process initiated by DTBP with the assistance of a CAr-Ru bond ortho/para-directing effect.
- Li, Gang,Gao, Yuan,Jia, Chunqi,Wang, Shichong,Yan, Bingxu,Fang, Yu,Yang, Suling
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supporting information
p. 8758 - 8763
(2020/12/02)
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- A ortho position alkylation method of organic compound containg pyridine
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A process for introducing alkyl at ortho positions of organic compounds containing pyridine. The method is not affected by the kind of substituent bonded to the pyridine and can be alkylated with high positional selectivity and high yield at N-based ortho-position of pyridine without being affected by the kind of substituent introduced to pyridine ortho position (pyridine N-based) can be advantageously used for the preparation of a compound containing an alkyl-introduced pyridine structure.
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Paragraph 0074-0084; 0108-0119
(2020/12/05)
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- A Highly Efficient Monophosphine Ligand for Parts per Million Levels Pd-Catalyzed Suzuki–Miyaura Coupling of (Hetero)Aryl Chlorides
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A new indolylphosphine WK-phos has been synthesized for Pd-catalyzed Suzuki–Miyaura coupling of (hetero)aryl chlorides with (alkyl)arylboronic acids. Comprising this newly developed ligand with palladium(II) acetate, the resulting catalyst system was found to be highly effective in facilitating the reaction even when the catalyst loading reaches parts per million levels (e.g. 10 ppm). These examples represent one of the lowest catalyst loadings reported to date of employing monophosphine (e.g. Ar-PCy2) for Suzuki–Miyaura reactions. The ligand geometry has also been well-characterized by single-crystal X-ray crystallography.
- Choy, Pui Ying,Yuen, On Ying,Leung, Man Pan,Chow, Wing Kin,Kwong, Fuk Yee
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p. 2846 - 2853
(2020/04/09)
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- Palladium-Catalyzed Cascade Reactions of I-Ketonitriles with Arylboronic Acids: Synthesis of Pyridines
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This study presents the first example of the Pd-catalyzed cascade reactions of 5-oxohexanenitrile with arylboronic acids, affording important synthon 2-methylpyridines that can be further translated through C(sp3)-H functionalization to construct pyridine derivatives. Furthermore, this chemistry allows 5-oxo-5-Arylpentanenitrile to react with arylboronic acids to provide unsymmetrical 2,6-diarylpyridines. This protocol paves the way for the practical and atom economical syntheses of valuable pyridines with broad functional groups in moderate to excellent yields under mild conditions.
- Chen, Jiuxi,Hu, Maolin,Li, Renhao,Liu, Jichao,Qi, Linjun,Shao, Yinlin,Yao, Xinrong,Zhao, Zhiwei,Zhen, Qianqian
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supporting information
p. 114 - 119
(2020/03/25)
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- Sustainable synthesis of quinolines (pyridines) catalyzed by a cheap metal Mn(I)-NN complex catalyst
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This study represents the first example of a bidentate phosphine-free manganese(I)-NN complex catalyst for the synthesis of quinolines (pyridines) through acceptorless dehydrogenative condensation of various secondary alcohols with amino alcohols. The coupling reactions occurred at 3 mol% catalyst loading and 110°C, and tolerated diverse functional groups. Moderate to excellent yields ranging from 45% to 89% were achieved after 12 hr of reaction. The present protocol provides a concise and environmentally friendly method for the construction of heterocyclic compounds.
- Chai, Huining,Tan, Weiqiang,Lu, Yuanyuan,Zhang, Guangyao,Ma, Jiping
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- Synthesis of Pyridines, Quinolines, and Pyrimidines via Acceptorless Dehydrogenative Coupling Catalyzed by a Simple Bidentate P^ N Ligand Supported Ru Complex
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A ruthenium hydrido chloride complex (1) supported by a simple, heteroleptic bidentate P^N ligand (L1) containing a diarylphosphine and a benzannulated phenanthridine donor arm is reported. In the presence of base, complex 1 catalyzes multicomponent reactions using alcohol precursors to produce structurally diverse molecules including pyridines, quinolines, and pyrimidines via acceptorless dehydrogenative coupling pathways. Notably, L1 does not bear readily (de)protonated Br?nsted acidic or basic groups common to transition metal catalysts capable of these sorts of transformations, suggesting metal-ligand cooperativity does not play a significant role in the catalytic reactivity of 1. A rare example of an η2-aldehyde adduct of ruthenium was isolated and structurally characterized, and its role in acceptorless dehydrogenative coupling reactions is discussed.
- Mondal, Rajarshi,Herbert, David E.
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supporting information
p. 1310 - 1317
(2020/04/15)
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- METAL COMPLEXES CONTAINING SUBSTITUTED PYRIDINE LIGANDS
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Novel compounds with substituted pyridine ligands are disclosed, which can be used as emitters in an electroluminescent device. These novel complexes can provide highly saturated color and long lifetime, and good device performance. Also disclosed are an electroluminescent device and a formulation.
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Paragraph 0136; 0137
(2019/08/02)
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- N-Heterocarbene Palladium Complexes with Dianisole Backbones: Synthesis, Structure, and Catalysis
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A series of palladium N-heterocyclic carbenes (NHCs), complexes C1-C5, bearing dianisole backbones and substituted N-aryl moieties have been synthesized and characterized. The electronic effect as well as the steric environment of the NHC ligands has been assessed. The synthesized palladium complexes were applied for Suzuki-Miyaura cross-coupling reactions under aerobic conditions. The relationship between the catalytic structure and catalytic performance was then extensively investigated. Upon optimizing the reaction conditions, the C4 was found to be highly efficient to catalyze the cross-coupling of (hetero)aryl chlorides with (hetero)arylboronic acids at a 0.1 mol % palladium loading.
- Li, Dong-Hui,He, Xu-Xian,Xu, Chang,Huang, Fei-Dong,Liu, Ning,Shen, Dong-Sheng,Liu, Feng-Shou
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p. 2539 - 2552
(2019/06/17)
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- Chiral 1,2-dihydropyridine compound as well as preparation method and application thereof
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The invention discloses a synthesis method for preparing chiral polysubstituted 1,2-dihydropyridine as well as polysubstituted pyridine and chiral piperidine derived from chiral polysubstituted 1,2-dihydropyridine by using a "one-pot serial connection method". The method comprises the following step: by taking an imine compound and an aldehyde compound as raw materials, performing an asymmetric Mannich reaction, a Wittig reaction and an intramolecular ring-closing reaction in sequence, so as to synthesize a chiral 1,2-dihydropyridine compound with high three-dimensional selectivity. The product does not need to be purified, and a polysubstituted pyridine compound can be prepared through oxidation aromatization through further "one-pot serial connection", and a polysubstituted chiral piperidine compound can be also prepared through catalytic hydrogenation after separation and purification. The method starts from simple and easily obtained raw materials, separation and purification of anintermediate are avoided, and compounds of 1,2-dihydropyridine, polysubstituted pyridine and chiral piperidine are efficiently synthesized through simples steps of operation. Nitrogenous six-memberedring frameworks which are synthesized by using the method and disclosed by the invention are all common in many natural products and medicine molecules, and have great significances for acceleratingmedicine research and development.
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Paragraph 0200-0202
(2020/01/03)
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- Multicomponent Aromatic and Benzylic Mannich Reactions through C?H Bond Activation
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Multicomponent Mannich reactions through C?H bond activation are described. These transformations allowed for the straightforward generation of densely substituted benzylic and homo-benzylic amines in good yields. The reaction involves a reaction between two transient species: an organometallic species, generated by transition-metal-catalyzed sp2 or sp3 C?H bond activation and an in situ generated imine. The use of an acetal as an aldehyde surrogate was found essential for the reaction to proceed. The process could be successfully applied to RhIII-catalyzed sp2 C?H bond functionalization and extended to CuII-catalyzed sp3 C?H bond functionalization.
- Xavier, Tania,Rayapin, Corinne,Le Gall, Erwan,Presset, Marc
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supporting information
p. 13824 - 13828
(2019/11/03)
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- Phosphine Ligand-Free Ruthenium Complexes as Efficient Catalysts for the Synthesis of Quinolines and Pyridines by Acceptorless Dehydrogenative Coupling Reactions
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A series of phosphine-free Ru(III)/Ru(II) complexes of NH functionalized N?N?N pincer ligands exhibit excellent activity for acceptorless dehydrogenative coupling (ADC) of secondary alcohols with 2-aminobenzyl or γ-amino alcohols to quinolines and pyridines. Ru(III) complexes [LRuCl3] (L=6-(3-R1,5-R2-1H-pyrazol-1-yl)-N-(pyridin-2-yl)pyridin-2-amine; 1 a: R1=R2=H (L1); 1 b: R1=R2=Me (L2); 1 c: R1=H, R2=CF3 (L3); 1 d: R1=H, R2=Ph (L4); 1bMe: L=6-(3,5-dimethyl-1H-pyrazol-1-yl)-N-methyl-N-(pyridin-2-yl)pyridin-2-amine (L2Me)) were obtained by refluxing RuCl3 ? xH2O with the corresponding ligand in EtOH. Five Ru(II) complexes [LRu(DMSO-κS)Cl2] (2 a: L=L1; 2 b: L=L2; 2 c: L=L3; 2 d: L=L4; 2bMe: L=L2Me) were formed by reducing the corresponding Ru(III) complex in refluxing EtOH. The latter complexes could also be prepared directly by refluxing Ru(DMSO)4Cl2 with the corresponding ligand in EtOH. These Ru(III) and Ru(II) complexes, especially 1 b/2 b, exhibited high catalytic efficiency and broad functional group tolerance in ADC reactions of secondary alcohols with 2-aminobenzyl or γ-amino alcohols to quinolines and pyridines. A detail mechanistic study indicated the Ru(III) complex was reduced into the Ru(II) species, which is the active catalytic center for ADC via a Ru?H/N?H bifunctional outer-sphere mechanism. This protocol provides a reliable, atom-economical and environmentally benign procedure for C?N and C?C bond formation.
- Guo, Bin,Yu, Tian-Qi,Li, Hong-Xi,Zhang, Shi-Qi,Braunstein, Pierre,Young, David J.,Li, Hai-Yan,Lang, Jian-Ping
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p. 2500 - 2510
(2019/05/10)
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- Reductive C2-Alkylation of Pyridine and Quinoline N-Oxides Using Wittig Reagents
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The ability to alkylate pyridines and quinolines is important for their further development as pharmaceuticals and agrochemicals, and for other purposes. Herein we describe the unprecedented reductive alkylation of pyridine and quinoline N-oxides using Wittig reagents. A wide range of pyridine and quinoline N-oxides were converted into C2-alkylated pyridines and quinolines with excellent site selectivity and functional-group compatibility. Sequential C?H functionalization reactions of pyridine and quinoline N-oxides highlight the utility of the developed method. Detailed labeling experiments were performed to elucidate the mechanism of this process.
- Han, Sangil,Chakrasali, Prashant,Park, Jihye,Oh, Hyunjung,Kim, Saegun,Kim, Kyuneun,Pandey, Ashok Kumar,Han, Sang Hoon,Han, Soo Bong,Kim, In Su
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supporting information
p. 12737 - 12740
(2018/09/20)
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- Suzuki-Miyaura cross-coupling for efficient synthesis of aryl-substituted N-heteroarenes catalyzed by recyclable N-phenylpiperazine-Palladium(II) complex
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Polystyrene supported N-phenylpiperazine-Pd(II) complex D was synthesized and characterized by various techniques, including Fourier transform infrared spectroscopy (FTIR), scanning electronmicroscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and thermal analysis (TG-DTA). This heterogeneous Pd(II) complex showed high catalytic efficiency for the Suzuki-Miyaura coupling of arylboronic acids with aryl bromides, aryl chlorides to give the corresponding 2-arylpyridines and heteroarenes. The coupled products were formed in excellent yields at low catalyst loadings under mild reaction conditions. Further, this heterogeneous catalyst showed excellent recyclability and reused for four cycles with no significant decrease in its activity.
- Perumgani, Pullaiah C.,Kodicherla, Balaswamy,Mandapati, Mohan Rao,Parvathaneni, Sai Prathima
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supporting information
p. 227 - 232
(2018/04/02)
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- Accessing Heterobiaryls through Transition-Metal-Free C-H Functionalization
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Herein we report a transition-metal-free synthetic protocol for heterobiaryls, one of the most important pharmacophores in the modern drug industry, employing a new multidonor phenalenyl (PLY)-based ligand. The current procedure offers a wide substrate scope (24 examples) with a low catalyst loading resulting in an excellent product yield (up to 95%). The reaction mechanism involves a single electron transfer (SET) from a phenalenyl-based radical to generate a reactive heteroaryl radical. To establish the mechanism, we have isolated the catalytically active SET initiator, characterizing by a magnetic study.
- Banik, Ananya,Paira, Rupankar,Shaw, Bikash Kumar,Vijaykumar, Gonela,Mandal, Swadhin K.
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p. 3236 - 3244
(2018/03/23)
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- Transition-Metal-Free Decarboxylative Arylation of 2-Picolinic Acids with Arenes under Air Conditions
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A facile, transition-metal-free, and direct decarboxylative arylation of 2-picolinic acids with simple arenes is described. The oxidative decarboxylative arylation of 2-picolinic acids with arenes proceeds readily via N-chloro carbene intermediates to afford 2-arylpyridines in satisfactory to good yields under transition-metal-free conditions. This new type of decarboxylative arylation is operationally simple and scalable and exhibits high functional-group tolerance. Various synthetically useful functional groups, such as halogen atoms, methoxycarbonyl, and nitro, remain intact during the decarboxylative arylation of 2-picolinic acids.
- Zhang, Xitao,Feng, Xiujuan,Zhou, Chuancheng,Yu, Xiaoqiang,Yamamoto, Yoshinori,Bao, Ming
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supporting information
p. 7095 - 7099
(2018/11/23)
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- NNN-Ruthenium Catalysts for the Synthesis of Pyridines, Quinolines, and Pyrroles by Acceptorless Dehydrogenative Condensation
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The bidentate ruthenium complex (HO-C5H3N-CO-C5H3N-C5H4N)Ru(CO)2Cl2 (2) could transform to a tridentate product (HO-C5H3N-CO-C5H3N-C5H4N)Ru(CO)Cl2 (3), which further reacted with CH3ONa in the presence of PPh3 to convert to two complexes [(OC5H3N-CO-C5H3N-C5H4N)Ru(PPh3)2(CO)]Cl- (4) and [(OC5H3N-CO-C5H3N-C5H4N)Ru(PPh3)(CO)Cl] (5), via -OH deprotonation. The catalytic coupling cyclizations of secondary alcohols with amino alcohols were investigated, and complex 3 exhibited the highest activity. The coupling reactions proceeded in air with only 0.2 mol % catalyst loading and had a broad scope for the synthesis of pyridines, quinolones, and pyrroles.
- Deng, Danfeng,Hu, Bowen,Yang, Min,Chen, Dafa
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supporting information
p. 2386 - 2394
(2018/07/31)
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- α-Halo carbonyls enable: Meta selective primary, secondary and tertiary C-H alkylations by ruthenium catalysis
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A catalytic meta selective C-H alkylation of arenes is described using a wide range of α-halo carbonyls as coupling partners. Previously unreported primary alkylations with high meta selectivity have been enabled by this methodology whereas using straight chain alkyl halides affords ortho substituted products. Mechanistic analysis reveals an activation pathway whereby cyclometalation with a ruthenium(ii) complex activates the substrate molecule and is responsible for the meta selectivity observed. A distinct second activation of the coupling partner allows site selective reaction between both components.
- Paterson, Andrew J.,Heron, Callum J.,McMullin, Claire L.,Mahon, Mary F.,Press, Neil J.,Frost, Christopher G.
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supporting information
p. 5993 - 6000
(2017/07/25)
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- Spatially isolated palladium in porous organic polymers by direct knitting for versatile organic transformations
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We report here a direct knitting Method for preparation of highly robust, effective while air- and moisture-tolerant, and readily recyclable three-dimensional (3D) porous polymer-Pd network (PPPd) from the widely used Pd(PPh3)4. Electro-beam induced Pd atom crystallization was observed for the first time in organic polymer and revealed the ultrafine dispersion of palladium atoms. Challenging types of Suzuki-Miyaura couplings, reductive coupling of aryl halides and oxidative coupling of arylboronic acid were successively catalyzed by PPPd in aqueous media. Also catalytically selective C–H functionalization reactions were achieved with orders of magnitude more efficient than conventional Pd homogeneous catalysts. The strategy developed here provides a practical method for easy-to-make yet highly efficient heterogeneous catalysis.
- Wang, Xinbo,Min, Shixiong,Das, Swapan K.,Fan, Wei,Huang, Kuo-Wei,Lai, Zhiping
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p. 101 - 109
(2017/10/06)
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- Phosphine ligand for indole skeleton as well as preparation method and application of phosphine ligand
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The invention provides a phosphine ligand for a 3-(disubstituted phosphino)-1-alkyl-2-substituted phenyl-indole skeleton as well as a preparation method and application of the phosphine ligand. The structure of the phosphine ligand for the 3-(disubstituted phosphino)-1-alkyl-2-substituted phenyl-indole skeleton is shown as the following formula I: (shown in the description), wherein Z is carbon or nitrogen, R is alkyl, substituted alkyl, olefin, aryl or fluorine, R1 is alkyl, substituted alkyl or aryl, R2 is alkyl, substituted alkyl or fluorine, and R3 is alkyl, substituted alkyl or aryl.
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Paragraph 0221-0225; 0227
(2017/12/30)
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- A Zwitterionic Palladium(II) Complex as a Precatalyst for Neat-Water-Mediated Cross-Coupling Reactions of Heteroaryl, Benzyl, and Aryl Acid Chlorides with Organoboron Reagents
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The Suzuki–Miyaura cross-coupling (SMC) reactions of several heteroaryl chlorides, benzyl chlorides, and aryl acid chlorides with (hetero)arylboron reagents have been investigated in the presence of [Pd(HL1)(PPh3)Cl2] (I) [HL1 = 3-[(2,6-diisopropylphenyl)-1-imidazolio]-2-quinoxalinide] as catalyst and K2CO3 as base in neat water. The synthesis of the heterocycle-containing biaryls required the addition of 2 mol-% of a phosphine ligand (PPh3 or X-Phos). A combination of more than 115 substrates were screened and it was found that I is a versatile catalyst that can produce heterocycle-containing biaryls, diarylmethanes, and benzophenones in moderate-to-excellent yields.
- Ramakrishna, Visannagari,Rani, Morla Jhansi,Reddy, Nareddula Dastagiri
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p. 7238 - 7255
(2018/01/01)
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- Cobalt-Catalyzed Cross-Coupling Reactions of Arylboronic Esters and Aryl Halides
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An efficient cobalt catalyst system for the Suzuki-Miyaura cross-coupling reaction of arylboronic esters and aryl halides has been identified. In the presence of cobalt(II)/terpyridine catalyst and potassium methoxide, a diverse array of (hetero)biaryls have been prepared in moderate to excellent yields.
- Duong, Hung A.,Wu, Wenqin,Teo, Yu-Yuan
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supporting information
p. 4363 - 4366
(2017/12/05)
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- Non-transition metal-catalyzed 2-phenylpyridine compound synthesis method
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The invention relates to a pharmaceutical and chemical intermediate preparation method, in particular to a non-transition metal-catalyzed 2-phenylpyridine compound synthesis method. A 2-phenylpyridine compound serves as an important component of a plurality of pharmacologically active molecules and bioactive molecules, has important application value in the fields of organic synthesis, pharmaceutical chemistry and the like, and is broad in market prospect. According to the non-transition metal-catalyzed 2-phenylpyridine compound synthesis method, namely a non-transition metal-catalyzed 2-phenylpyridine derivative synthesis method, pyridine-2-formic acid and benzene are adopted as raw materials; and under the presence of one or more alkalis and free radical initiators, the 2-phenylpyridine compound is synthesized in the mild condition. The non-transition metal-catalyzed 2-phenylpyridine compound synthesis method provided by the invention has the advantages that the steps are simple, the raw materials are easy to obtain, the reaction condition is mild, as well as the use value and the social and economic benefits are relatively great.
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Paragraph 0052; 0053; 0054
(2017/07/04)
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- A Versatile Ru(II)-NNP Complex Catalyst for the Synthesis of Multisubstituted Pyrroles and Pyridines
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A pincer-type Ru(II)-NNP complex bearing a pyrazolyl-(NH-PtBu2)-pyridine ligand was synthesized and structurally characterized by NMR, IR, elemental analysis, and X-ray single-crystal crystallographic determinations, which efficiently catalyzed the synthesis of multisubstituted pyrroles and pyridines by means of the reactions of secondary alcohols and β- or γ-amino alcohols through deoxygenation and selective C-N and C-C bond formation. The coupling reactions took place with 0.3 mol % catalyst loading and tolerated diverse functional groups. The present work provides an alternative method to construct highly active transition-metal complex catalysts from readily available ligands.
- Chai, Huining,Wang, Liandi,Liu, Tingting,Yu, Zhengkun
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supporting information
p. 4936 - 4942
(2018/02/07)
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- The photochemical alkylation and reduction of heteroarenes
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The functionalization of heteroarenes has been integral to the structural diversification of medicinally active molecules such as quinolines, pyridines, and phenanthridines. Electron-deficient heteroarenes are electronically compatible to react with relatively nucleophilic free radicals such as hydroxyalkyl. However, the radical functionalization of such heteroarenes has been marked by the use of transition-metal catalyzed processes that require initiators and stoichiometric oxidants. Herein, we describe the photochemical alkylation of quinolines, pyridines and phenanthridines, where through direct excitation of the protonated heterocycle, alcohols and ethers, such as methanol and THF, can serve as alkylating agents. We also report the discovery of a photochemical reduction of these heteroarenes using only iPrOH and HCl. Mechanistic studies to elucidate the underlying mechanism of these transformations, and preliminary results on catalytic methylations are also reported.
- McCallum,Pitre,Morin,Scaiano,Barriault
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p. 7412 - 7418
(2017/10/31)
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- Direct C(sp3)-H Cross Coupling Enabled by Catalytic Generation of Chlorine Radicals
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Here we report the development of a C(sp3)-H cross-coupling platform enabled by the catalytic generation of chlorine radicals by nickel and photoredox catalysis. Aryl chlorides serve as both cross-coupling partners and the chlorine radical source for the α-oxy C(sp3)-H arylation of cyclic and acyclic ethers. Mechanistic studies suggest that photolysis of a Ni(III) aryl chloride intermediate, generated by photoredox-mediated single-electron oxidation, leads to elimination of a chlorine radical in what amounts to the sequential capture of two photons. Arylations of a benzylic C(sp3)-H bond of toluene and a completely unactivated C(sp3)-H bond of cyclohexane demonstrate the broad implications of this manifold for accomplishing numerous C(sp3)-H bond functionalizations under exceptionally mild conditions.
- Shields, Benjamin J.,Doyle, Abigail G.
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supporting information
p. 12719 - 12722
(2016/10/13)
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- Carboxyamido/carbene ligated palladium (II) complex: A versatile catalyst for the synthesis of aryl-substituted heteroarenes
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Carboxy amido/carbene ligated Pd-complex catalyzed Suzuki-Miyaura cross-coupling of aryl-boronic acids with heteroaryl bromides is described. The protocol has a broad substrate scope that includes electron-rich, electron-deficient and sterically hindered arylboronic acids and heteroaryl bromides. The catalytic activity of the catalyst has been further investigated in the coupling of 2,6-dibromopyridine with arylboronic acids.
- Vishnuvardhan Reddy, Police,Parsharamulu, Thupakula,Annapurna, Manne,Likhar, Pravin R.,Kantam, Mannepalli Lakshmi,Bhargava, Suresh
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supporting information
p. 150 - 153
(2016/12/06)
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- Transition-Metal-Free Regioselective Alkylation of Pyridine N-Oxides Using 1,1-Diborylalkanes as Alkylating Reagents
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Reported herein is an unprecedented base-promoted deborylative alkylation of pyridine N-oxides using 1,1-diborylalkanes as alkyl sources. The reaction proceeds efficiently for a wide range of pyridine N-oxides and 1,1-diborylalkanes with excellent regioselectivity. The utility of the developed method is demonstrated by the sequential C?H arylation and methylation of pyridine N-oxides. The reaction also can be applied for the direct introduction of a methyl group to 9-O-methylquinine N-oxide, thus it can serve as a powerful method for late-stage functionalization.
- Jo, Woohyun,Kim, Junghoon,Choi, Seoyoung,Cho, Seung Hwan
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supporting information
p. 9690 - 9694
(2016/08/10)
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- A General Palladium-Catalyzed Hiyama Cross-Coupling Reaction of Aryl and Heteroaryl Chlorides
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A general palladium-catalyzed Hiyama cross-coupling reaction of aryl and heteroaryl chlorides with aryl and heteroaryl trialkoxysilanes by a Pd(OAc)2/L2 catalytic system is presented. A newly developed water addition protocol can dramatically improve the product yields. The conjugation of the Pd/L2 system and the water addition protocol can efficiently catalyze a broad range of electron-rich, -neutral, -deficient, and sterically hindered aryl chlorides and heteroaryl chlorides with excellent yields within three hours and the catalyst loading can be down to 0.05 mol % Pd for the first time. Hiyama coupling of heteroaryl chlorides with heteroaryl silanes is also reported for the first time. The reaction can be easily scaled up 200 times (100 mmol) without any degasification and purification of reactants; this facilitates the practical application in routine synthesis.
- Yuen, On Ying,So, Chau Ming,Man, Ho Wing,Kwong, Fuk Yee
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supporting information
p. 6471 - 6476
(2016/05/09)
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- Chemoselective Synthesis of Polysubstituted Pyridines from Heteroaryl Fluorosulfates
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A selection of heteroaryl fluorosulfates were readily synthesized using commercial SO2F2 gas. These substrates are highly efficient coupling partners in the Suzuki reaction. Through judicious selection of Pd catalysts the fluorosulfate functionality is differentiated from bromide and chloride; the order of reactivity being: -Br> -OSO2F> -Cl. Exploiting this trend allowed the stepwise chemoselective synthesis of a number of polysubstituted pyridines, including the drug Etoricoxib. A selection of heteroaryl fluorosulfates were readily synthesized using commercial SO2F2 gas. These substrates are highly efficient coupling partners in the Suzuki reaction. Through judicious selection of Pd catalysts the fluorosulfate functionality is differentiated from bromide and chloride; the order of reactivity being: -Br> -OSO2F> -Cl. Exploiting this trend allowed the stepwise chemoselective synthesis of a number of polysubstituted pyridines, including the drug Etoricoxib.
- Zhang, Enxuan,Tang, Jiaze,Li, Suhua,Wu, Peng,Moses, John E.,Sharpless, K. Barry
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supporting information
p. 5692 - 5697
(2016/04/20)
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- A Ruthenium Catalyst with Unprecedented Effectiveness for the Coupling Cyclization of - Amino Alcohols and Secondary Alcohols
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The ruthenium complex (8-(2-diphenylphosphinoethyl)aminotrihydroquinolinyl)(carbonyl)(hydrido)ruthenium chloride exhibited extremely high efficiency toward the coupling cyclization of -amino alcohols with secondary alcohols. The corresponding products, pyridine or quinoline derivatives, are obtained in good to high isolated yields. On comparison with literature catalysts whose noble-metal loading with respect to -amino alcohols reached 0.5-1.0 mol % for Ru and a record lowest of 0.04 mol % for Ir, the current catalyst achieves the same efficiency with a loading of 0.025 mol % for Ru. The mechanism of acceptorless dehydrogenative condensation (ADC) was proposed on the basis of DFT calculations; in addition, the reactive intermediates were determined by GC-MS, NMR, and single-crystal X-ray diffraction. The catalytic process is potentially suitable for industrial applications.
- Pan, Bing,Liu, Bo,Yue, Erlin,Liu, Qingbin,Yang, Xinzheng,Wang, Zheng,Sun, Wen-Hua
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p. 1247 - 1253
(2016/02/18)
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- Comparative Catalytic Activity of Group 9 [CpMIII] Complexes: Cobalt-Catalyzed C-H Amidation of Arenes with Dioxazolones as Amidating Reagents
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A procedure for the [CpCoIII]-catalyzed direct C-H amidation of arenes with dioxazolone has been developed. This reaction proceeds under straightforward and mild conditions with a broad range of substrates, including anilides. A comparative study on the catalytic activity of Group 9 [{CpMCl2}2] complexes revealed the unique efficiency of the cobalt catalyst. Pick of the bunch: A variety of arenes, including anilides, underwent direct C-H amidation with dioxazolones in the presence of a cobalt catalyst with a Cp? ligand under mild and straightforward reaction conditions (see scheme; Piv=pivaloyl). A comparative study of Group 9 [CpMIII] complexes revealed the unique ability of the cobalt catalyst to promote this transformation efficiently.
- Park, Juhyeon,Chang, Sukbok
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supporting information
p. 14103 - 14107
(2016/01/25)
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- Directed meta-Selective Bromination of Arenes with Ruthenium Catalysts
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A Ru-catalyzed direct C?H activation/meta-bromination of arenes bearing pyridyl, pyrimidyl, and pyrazolyl directing groups has been developed. A series of bromo aryl pyridines and pyrimidines have been synthesized, and further coupling reactions have also been demonstrated for a number of representative functionalized arenes. Preliminary mechanistic studies have revealed that this reaction may proceed through radical-mediated bromination when NBS is utilized as the bromine source. This type of transformation has opened up a new direction for the radical non-ipso functionalization of metal with regard to future C?H activation development that would allow the remote functionalization of aromatic systems.
- Yu, Qingzhen,Hu, Le'An,Wang, Yue,Zheng, Shasha,Huang, Jianhui
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supporting information
p. 15284 - 15288
(2016/01/25)
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- A Polymer-Bound Monodentate-P-Ligated Palladium Complex as a Recyclable Catalyst for the Suzuki-Miyaura Coupling Reaction of Aryl Chlorides
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A three-fold cross-linked polymer-bound phosphine (POL-Ph3P) with high phosphorus content has been prepared. The phosphorus-containing polymer forms a monodentate-P-ligated palladium complex, which shows excellent activity in Suzuki-Miyaura cross-coupling reactions of aryl chlorides. Importantly, the catalyst Pd/POL-Ph3P is highly stable and can be reused for at least 10 times without losing reactivity.
- Zhou, Yun-Bing,Li, Cun-Yao,Lin, Min,Ding, Yun-Jie,Zhan, Zhuang-Ping
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supporting information
p. 2503 - 2508
(2015/08/18)
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- Synthesis of 1H-azadienes and application to one-pot organic transformations
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1H-Azadienes were synthesized from allyl azides by ruthenium catalysis under mild and neutral conditions. Applications of the 1H-azadienes were demonstrated for the one-pot synthesis of N-benzyl-1-azadienes, hydrazones, tertiary carbinamines, dieneamide, and N-cyclohexenylacetamides. Two 1H-azatrienes were also synthesized, which were transformed to pyridine derivatives.
- Kwon, Yearang,Jeon, Mina,Park, Jin Yong,Rhee, Young Ho,Park, Jaiwook
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p. 661 - 668
(2016/01/09)
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- Alcohols as alkylating agents in heteroarene C-H functionalization
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Redox processes and radical intermediates are found in many biochemical processes, including deoxyribonucleotide synthesis and oxidative DNA damage. One of the core principles underlying DNA biosynthesis is the radical-mediated elimination of H2O to deoxygenate ribonucleotides, an example of 'spin-centre shift', during which an alcohol C-O bond is cleaved, resulting in a carbon-centred radical intermediate. Although spin-centre shift is a well-understood biochemical process, it is underused by the synthetic organic chemistry community. We wondered whether it would be possible to take advantage of this naturally occurring process to accomplish mild, non-traditional alkylation reactions using alcohols as radical precursors. Because conventional radical-based alkylation methods require the use of stoichiometric oxidants, increased temperatures or peroxides, a mild protocol using simple and abundant alkylating agents would have considerable use in the synthesis of diversely functionalized pharmacophores. Here we describe the development of a dual catalytic alkylation of heteroarenes, using alcohols as mild alkylating reagents. This method represents the first, to our knowledge, broadly applicable use of unactivated alcohols as latent alkylating reagents, achieved via the successful merger of photoredox and hydrogen atom transfer catalysis. The value of this multi-catalytic protocol has been demonstrated through the late-stage functionalization of the medicinal agents, fasudil and milrinone.
- Jin, Jian,MacMillan, David W. C.
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- Palladium-catalyzed trifluoromethylthiolation of aryl C-H bonds
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A method for monotrifluoromethylthiolation of arenes via palladium-catalyzed directed C-H bond activation was described. The reaction was compatible with a variety of functional groups. Initial mechanistic studies disclosed that the turnover limiting step of the catalytic cycle did not involve C-H activation.
- Xu, Chunfa,Shen, Qilong
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supporting information
p. 2046 - 2049
(2014/05/06)
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- Synthesis and characterization of hydrophilic theophylline base compounds and their use as ligands in the microwave assisted Suzuki-Miyaura couplings of halopyridines in water Dedicated to the memory of Prof. Dr. Armando Cabrera Ortiz pioneer of Catalysis in Mexico. Great Researcher but above all a Great Human Being
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Xanthine derivatives, caffeine (L1), theobromine (L2), theophylline (L3), 7-(β-hydroxyethyltheophylline) (L4), (7-(2,3-dihydroxypropyl)theophylline) (L5), and theophylline 7-acetic acid (L6) and the acetylated derivatives of the later three (L7-L9) were employed as ligands for the in situ palladium catalyzed Suzuki-Miyaura cross couplings of a series of halogenated pyridines. Optimized conditions were found where the diacetylated ligand (L8) was determined to be the best for this process, producing good to excellent yields in the couplings of halogenated anilines with phenylboronic acid under mild reaction conditions in water using microwave irradiation.
- Conelly-Espinosa, Patricia,Toscano, Ruben A.,Morales-Morales, David
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p. 5841 - 5845
(2015/01/09)
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- Iridium-catalyzed asymmetric hydrogenation of pyridinium salts for constructing multiple stereogenic centers on piperidines
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A salt formation strategy for asymmetric hydrogenation of pyridines is described. Poly-substituted pyridinium salts were successfully hydrogenated using chiral iridium dinuclear complexes to afford substituted piperidines with multiple stereogenic centers after a simple basic workup.
- Kita, Yusuke,Iimuro, Atsuhiro,Hida, Shoji,Mashima, Kazushi
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supporting information
p. 284 - 286
(2014/03/21)
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- Direct, catalytic, and regioselective synthesis of 2-alkyl-, aryl-, and alkenyl-substituted N -Heterocycles from n -oxides
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A one-step transformation of heterocyclic N-oxides to 2-alkyl-, aryl-, and alkenyl-substituted N-heterocycles is described. The success of this broad-scope methodology hinges on the combination of copper catalysis and activation by lithium fluoride or magnesium chloride. The utility of this method for the late-stage modification of complex N-heterocycles is exemplified by facile syntheses of new structural analogues of several antimalarial, antimicrobial, and fungicidal agents.
- Larionov, Oleg V.,Stephens, David,Mfuh, Adelphe,Chavez, Gabriel
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supporting information
p. 864 - 867
(2014/03/21)
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- Palladium-catalyzed cross-coupling reaction of functionalized aryl- and heteroarylbismuthanes with 2-halo(or 2-Triflyl)azines and -diazines
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The palladium-catalyzed cross-coupling of highly functionalized organobismuthanes with 2-halo(or 2-triflyl)pyridines, -pyrimidines, -pyrazines, and -pyridazines is reported. The reaction tolerates numerous functional groups, including aldehydes. The synthesis of a shelf-stable (formylphenyl)bismuth reagent and its use in a cross-coupling reaction is also described. The palladium-catalyzed cross-coupling of highly functionalized organobismuthanes with 2-halo(or 2-triflyl)pyridines, -pyrimidines, -pyrazines, and -pyridazines is reported. The reaction tolerates numerous functional groups, including aldehydes. The synthesis of a shelf-stable (formylphenyl)bismuth reagent and its use in cross-coupling reactions is also described. Copyright
- Petiot, Pauline,Gagnon, Alexandre
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supporting information
p. 5282 - 5289
(2013/09/02)
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- An efficient class of P,N-type "phMezole-phos" ligands: Applications in palladium-catalyzed Suzuki coupling of aryl chlorides
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This study describes an efficient class of hemilabile benzimidazolyl- phosphane ligands that can be easily accessed from commercially available and inexpensive starting materials. The application of this ligand array in the palladium-catalyzed Suzuki-Miyaura coupling reaction of aryl chlorides with arylboronic acids is described. The palladium catalyst generated from this hemilabile phosphane is highly effective in the Suzuki-Miyaura coupling of unactivated aryl chlorides, and catalyst loadings as low as 1 ppm can be achieved. An efficient class of hemilabile benzimidazolyl-phosphane ligands were synthesized. The palladium catalyst generated from this hemilabile phosphane is highly effective in the Suzuki-Miyaura coupling of unactivated aryl chlorides, and catalyst loadings as low as 1 ppm can be achieved.
- Wong, Shun Man,So, Chau Ming,Chung, Kin Ho,Lau, Chak Po,Kwong, Fuk Yee
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supporting information; experimental part
p. 4172 - 4177
(2012/09/21)
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- Three-component coupling sequence for the regiospecific synthesis of substituted pyridines
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A de novo synthesis of substituted pyridines is described that proceeds through nucleophilic addition of a dithiane anion to an α,β- unsaturated carbonyl followed by metallacycle-mediated union of the resulting allylic alcohol with preformed trimethylsilane-imines (generated in situ by the low-temperature reaction of lithium hexamethyldisilazide with an aldehyde) and Ag(I)- or Hg(II)-mediated ring closure. The process is useful for the convergent assembly of di- through penta-substituted pyridines with complete regiochemical control.
- Chen, Ming Z.,Micalizio, Glenn C.
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p. 1352 - 1356
(2012/03/11)
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- Inhibition of 1-deoxy-d-xylulose-5-phosphate reductoisomerase by lipophilic phosphonates: SAR, QSAR, and crystallographic studies
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1-Deoxy-d-xylulose-5-phosphate reductoisomerase (DXR) is a novel target for developing new antibacterial (including antituberculosis) and antimalaria drugs. Forty-one lipophilic phosphonates, representing a new class of DXR inhibitors, were synthesized, among which 5-phenylpyridin-2-ylmethylphosphonic acid possesses the most activity against E. coli DXR (EcDXR) with a K i of 420 nM. Structure-activity relationships (SAR) are discussed, which can be rationalized using our EcDXR:inhibitor structures, and a predictive quantitative SAR (QSAR) model is also developed. Since inhibition studies of DXR from Mycobacterium tuberculosis (MtDXR) have not been performed well, 48 EcDXR inhibitors with a broad chemical diversity were found, however, to generally exhibit considerably reduced activity against MtDXR. The crystal structure of a MtDXR:inhibitor complex reveals the flexible loop containing the residues 198-208 has no strong interactions with the 3,4-dichlorophenyl group of the inhibitor, representing a structural basis for the reduced activity. Overall, these results provide implications in the future design and development of potent DXR inhibitors.
- Deng, Lisheng,Diao, Jiasheng,Chen, Pinhong,Pujari, Venugopal,Yao, Yuan,Cheng, Gang,Crick, Dean C.,Prasad, B. V. Venkataram,Song, Yongcheng
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scheme or table
p. 4721 - 4734
(2011/09/19)
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- Nickel-catalyzed dehydrogenative [4 + 2] cycloaddition of 1,3-dienes with nitriles
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Pyridines, which comprise one of the most important classes of the six-membered heterocyclic compounds, are widely distributed in nature, and the transition-metal-catalyzed [2 + 2 + 2] cycloaddition reaction of two alkynes and a nitrile is one of the most powerful methods for preparing versatile, highly substituted pyridine derivatives. However, the lack of chemo- and regioselectivity is still a crucial issue associated with fully intermolecular [2 + 2 + 2] cycloaddition. The present study developed the Ni(0)-catalyzed intermolecular dehydrogenative [4 + 2] cycloaddition reaction of 1,3-butadienes with nitriles to give a variety of pyridines regioselectively.
- Ohashi, Masato,Takeda, Ippei,Ikawa, Masashi,Ogoshi, Sensuke
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supporting information; experimental part
p. 18018 - 18021
(2011/12/13)
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- Heteroaromatic synthesis via olefin cross-metathesis: Entry to polysubstituted pyridines
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The olefin cross-metathesis reaction provides a rapid and efficient method for the synthesis of α,β-unsaturated 1,5-dicarbonyl derivatives which then serve as effective precursors to mono-tetrasubstituted pyridines. Manipulation of the key 1,5-dicarbonyl intermediate allows access to pyridines with a wide range of substitution patterns. An extension of this methodology facilitates the preparation of pyridines embedded within macrocycles, as exemplified by an efficient synthesis of (R)-(+)-muscopyridine. High levels of regiocontrol, short reaction sequences, and facile substituent variation are all notable aspects of this methodology.(Figure Presented)
- Donohoe, Timothy J.,Basutto, Jose A.,Bower, John F.,Rathi, Akshat
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supporting information; experimental part
p. 1036 - 1039
(2011/04/27)
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- A general and highly efficient method for the construction of aryl-substituted N-heteroarenes
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A general, simple and highly efficient method has been developed for the Pd(OAc)2-catalyzed ligand-free and aerobic Suzuki reaction of N-heteroaryl halides, which is strongly dependent on the molecular structure of solvent. A general, simple and highly efficient method has been developed for the Pd(OAc)2-catalyzed ligand-free and aerobic Suzuki reaction of N-heteroaryl halides including 2-pyridyl bromides, 3-pyridyl bromides, 3-quinolyl bromides, 5-pyrimidyl bromides and 2-pyrazyl chloride, which is strongly dependent on the molecular structure of solvent.
- Liu, Chun,Han, Na,Song, Xiaoxiao,Qiu, Jieshan
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supporting information; experimental part
p. 5548 - 5551
(2011/02/19)
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