- Pr2O3 Supported Nano-layered Ruthenium Catalyzed Acceptorless Dehydrogenative Synthesis of 2-Substituted Quinolines and 1,8-Naphthyridines from 2-Aminoaryl Alcohols and Ketones
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Pr2O3 supported Ru nanolayers and Ru nanoparticles catalysts were examined for the synthesis of quinolines. The Ru nanolayer was most active catalyst and showed a broad substrate scope. Structure-activity relationship demonstrated that the metallic state and morphology of Ru as well as the basic site of Pr2O3 were indispensable factors of this catalytic system.
- Chaudhari, Chandan,Sato, Katsutoshi,Ogura, Yuta,Miayahara, Shin-Ichiro,Nagaoka, Katsutoshi
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- Consecutive isomerization and cyclization of 3-(2-Aminophenyl)-1-arylprop- 2-yn-1-ols leading to 2-arylquinolines in the presence of potassium hydroxide
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3-(2-Aminophenyl)-1-arylprop-2-yn-1-ols are readily converted to 2-arylquinolines in good yields in ethanol at 80° in the presence of potassium hydroxide via domino isomerization and cyclization.
- Cho, Chan Sik,Lee, Na Young,Kim, Tae-Jeong,Shim, Sang Chul
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- A copper(II)-catalyzed protocol for modified Friedl?nder quinoline synthesis
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2-Aminobenzyl alcohol reacts with an array of ketones in dioxane at 100 °C in the presence of a catalytic amount of CuCl2 along with KOH under O2 atmosphere to afford the corresponding quinolines in good yields. 2-Aminobenzyl alcohol is also oxidatively coupled and cyclized with various aldehydes by step-by-step procedure, an initial treatment of 2-aminobenzyl alcohol in the presence of CuCl2 and KOH in dioxane under O2 atmosphere and subsequent addition of aldehyde to the mixture followed by stirring under argon atmosphere, to give 3-substituted quinolines in moderate to good yields.
- Cho, Chan Sik,Ren, Wen Xiu,Shim, Sang Chul
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- Ruthenium-catalysed oxidative cyclisation of 2-aminobenzyl alcohol with ketones: modified Friedlaender quinoline synthesis
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2-Aminobenzyl alcohol is oxidatively cyclised with an array of ketones in dioxane at 80 deg C in the presence of a catalytic amount of a ruthenium catalyst and KOH to afford the corresponding quinolines in high yields.
- Cho, Chan Sik,Kim, Bok Tae,Kim, Tae-Jeong,Shim, Sang Chul
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- The Diverse One-Pot Reactions of 2-Quinolylzincates: Homologation, Electrophilic Trapping, Hydroxylation, and Arylation Reactions
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2-Quinolylzincates were efficiently produced from the regioselective metalation reactions of quinoline with various organozincates as key intermediates. The four different types of title reactions of these intermediates under the presented reaction conditions allowed for the facile formation of the corresponding C-2 functionalized quinolines, which are not successfully accessed through typical zincation methods.
- Jeong, Hye Jin,Chae, Suyeon,Jeong, Keunhong,Namgoong, Sung Keon
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- Facile synthesis of 2-substituted quinolines and 3-alkynyl-2-aryl-2H-Indazole via SnCl2-mediated reductive cyclization
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A rapid and efficient SnCl2·2H2O mediated synthesis of quinolines and indazoles has been developed using A3-coupling followed by reductive cyclization. The key highlights are the formation of quinoline in a one-pot fashion and indazole through N-N bond formation.
- Sudhapriya, Narayanasamy,Nandakumar, Avanashiappan,Perumal, Paramasivan Thirumalai
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- Samarium diiodide mediated reductive coupling of 2-nitro-1,3-diphenyl-2-propen-1-one: Synthesis of quinolines
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The intramolecular reductive cyclization of 2-nitro-1,3-diphenyl-2-propen-1-ones (1) induced by SmI2 was investigated and 2-arylquinolines (2) were obtained in moderate to good yields at room temperature under neutral conditions.
- Wang, Xiaoxia,Zhang, Yongmin
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- Ruthenium-catalyzed oxidative coupling and cyclization between 2-aminobenzyl alcohol and secondary alcohols leading to quinolines
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2-Aminobenzyl alcohol is oxidatively coupled and cyclized with secondary alcohols in dioxane at 80°C in the presence of a catalytic amount of RuCl2(PPh3)3 and KOH along with 1-dodecene as a sacrificial hydrogen acceptor to give the corresponding quinolines in good yields. The cyclization is applicable to a wide range of alkyl(aryl) and alkyl(alkyl) carbinols. The catalytic pathway seems to be proceeded via a sequence involving initial oxidation of both substrates to carbonyl compounds, cross aldol reaction, and cyclodehydration.
- Cho, Chan Sik,Kim, Bok Tae,Choi, Heung-Jin,Kim, Tae-Jeong,Shim, Sang Chul
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- Multifunctional catalysis of a ruthenium-grafted hydrotalcite: One-pot synthesis of quinolines from 2-aminobenzyl alcohol and various carbonyl compounds via aerobic oxidation and aldol reaction
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The Ru-grafted hydrotalcite was found to be an excellent multifunctional catalyst for one-pot synthesis of quinolines from 2-aminobenzyl alcohol and various carbonyl compounds. These quinolines were obtained through aerobic oxidation by the Ru species, followed by aldol reaction on base sites of the hydrotalcite.
- Motokura, Ken,Mizugaki, Tomoo,Ebitani, Kohki,Kaneda, Kiyotomi
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- Palladium-catalyzed Sonogashira coupling reaction followed by isomerization and cyclization
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2-Iodoaniline reacts with terminal acetylenic carbinols in THF at 80 °C in the presence of a catalytic amount of PdCl2(PPh3) 2 and CuI along with aqueous tetrabutylammonium hydroxide to afford the corresponding 2-arylquinolines in good yields. The catalytic pathway seems to be proceeded via a sequence involving initial Sonogashira coupling between 2-iodoaniline and terminal acetylenic carbinols to form coupled acetylenic carbinols, isomerization of coupled acetylenic carbinols to α,β- unsaturated ketones, and cyclodehydration.
- Cho, Chan Sik
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- Large-Scale Cobalt-Catalyzed Cross-Couplings of Functionalized Bench-Stable Arylzinc Pivalates with (Hetero)Aryl and Alkenyl Halides
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A robust and scalable CoCl 2 -catalyzed cross-coupling between functionalized arylzinc pivalates and various electron-poor (hetero)aryl and alkenyl halides is reported.
- Hofmayer, Maximilian S.,Hammann, Jeffrey M.,Lutter, Ferdinand H.,Knochel, Paul
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- A Novel Approach to 2-Arylated Quinolines: Electrocyclization of Alkynyl Imines via Vinylidene Complexes
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(Matrix presented) Alkynyl imines underwent [4 + 2] electrocyclization in the presence of 20 mol % W(CO)5(THF) to give 2-arylated quinolines in good yields. A deuterium labeling study suggests that the reaction proceeds via a tungsten vinylidene complex.
- Sangu, Kenichiro,Fuchibe, Kohei,Akiyama, Takahiko
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- Synthesis of Quinolines Through Acceptorless Dehydrogenative Coupling Catalyzed by Rhenium PN(H)P Complexes
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A practical and sustainable synthesis of substituted quinolines was achieved through the annulation of 2-aminobenzyl alcohol with various secondary alcohols, ketones, aldehydes, or nitriles, under hydrogen-borrowing conditions. Under the catalysis of well-defined rhenium complexes bearing tridentate diphosphinoamino ligands, the reaction proceeded efficiently (31 examples were isolated with yields up to 96 %) affording a variety of quinoline derivatives.
- Wei, Duo,Dorcet, Vincent,Darcel, Christophe,Sortais, Jean-Baptiste
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- Decarbonylative Pd-Catalyzed Suzuki Cross-Coupling for the Synthesis of Structurally Diverse Heterobiaryls
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Heteroaromatic biaryls are core scaffolds found in a plethora of pharmaceuticals; however, their direct synthesis by the Suzuki cross-coupling is limited to heteroaromatic halide starting materials. Here, we report a direct synthesis of diverse nitrogen-containing heteroaromatic biaryls by Pd-catalyzed decarbonylative Suzuki cross-coupling of widely available heterocyclic carboxylic acids with arylboronic acids. The practical and modular nature of this cross-coupling enabled the straightforward preparation of >45 heterobiaryl products using pyridines, pyrimidines, pyrazines, and quinolines in excellent yields. We anticipate that the modular nature of this protocol will find broad application in medicinal chemistry and drug discovery research.
- Blakemore, David C.,Cervantes-Reyes, Alejandro,Chinigo, Gary M.,Smith, Aaron C.,Szostak, Michal
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supporting information
p. 1678 - 1683
(2022/03/14)
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- A Domino Heck Coupling-Cyclization-Dehydrogenative Strategy for the One-Pot Synthesis of Quinolines
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An efficient, one-pot, domino synthesis of quinolines via the coupling of iodoanilines with allylic alcohols facilitated by palladium catalysis is described. The overall synthetic process involves an intermolecular Heck coupling between 2-iodoanilines and allylic alcohols, intramolecular condensation of in situ generated ketones with an internal amine functional group, and a dehydrogenation sequence. Notably, this protocol occurs in water as a green solvent. Significantly, the method exhibits broad substrate scope and is applied for the synthesis of deuterated quinolines through a deuterium-exchange process.
- Ghora, Santanu,Sreenivasulu, Chinnabattigalla,Satyanarayana, Gedu
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p. 393 - 402
(2021/10/21)
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- Synthesis, structures, and photophysical properties of three-coordinate copper(I) complexes bearing bidentate bis[(2-diphenylphosphino)phenyl]ether (POP) ligand and monodentate substituted-quinoline ligand
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The three-coordinate Cu(I) complexes [Cu(POP)(X)]PF6, X = quinoline (P1), 2-(4-methoxyphenyl)quinoline (P2), 2-(4-(trifluoromethyl)phenyl)quinoline (P3), POP = bis[(2-diphenylphosphino)phenyl] ether were synthesized and characterized. The photo
- Huang, Huade,Wang, Jinglan,Wang, Rou,Wang, Yibo,Wu, Yaqian,Xu, Shengxian,Zhao, Feng
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- Iron catalyzed metal-ligand cooperative approaches towards sustainable synthesis of quinolines and quinazolin-4(3H)-ones
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Herein we report simple, efficient, and economically affordable metal-ligand cooperative strategies for synthesizing quinolines and quinazolin-4(3H)-ones via dehydrogenative functionalization of alcohols. Various polysubstituted quinolines and quinazolin-4(3H)-ones were prepared in good yields via dehydrogenative coupling of readily available alcohols with ketones and 2-aminobenzamides, respectively under air using a well-defined Fe(II)-catalyst, ([FeL1Cl2] (1)) bearing a redox-active azo-aromatic pincer 2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline) (L1). Control experiments and mechanistic investigation disclose that the one-electron reduced mono-anionic species [1]? bearing an iron-stabilized azo-anion radical ligand catalyzes these reactions. Both iron and the redox-active arylazo ligand participate synergistically during the different steps of these catalytic reactions.
- Mondal, Rakesh,Chakraborty, Gargi,Guin, Amit Kumar,Pal, Subhasree,Paul, Nanda D.
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- Designed pincer ligand supported Co(ii)-based catalysts for dehydrogenative activation of alcohols: Studies onN-alkylation of amines, α-alkylation of ketones and synthesis of quinolines
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Base-metal catalystsCo1,Co2andCo3were synthesized from designed pincer ligandsL1,L2andL3having NNN donor atoms respectively.Co1,Co2andCo3were characterized by IR, UV-Vis. and ESI-MS spectroscopic studies. Single crystal X-ray diffraction studies were investigated to authenticate the molecular structures ofCo1andCo3. CatalystsCo1,Co2andCo3were utilized to study the dehydrogenative activation of alcohols forN-alkylation of amines, α-alkylation of ketones and synthesis of quinolines. Under optimized reaction conditions, a broad range of substrates including alcohols, anilines and ketones were exploited. A series of control experiments forN-alkylation of amines, α-alkylation of ketones and synthesis of quinolines were examined to understand the reaction pathway. ESI-MS spectral studies were investigated to characterize cobalt-alkoxide and cobalt-hydride intermediates. Reduction of styrene by evolved hydrogen gas during the reaction was investigated to authenticate the dehydrogenative nature of the catalysts. Probable reaction pathways were proposed forN-alkylation of amines, α-alkylation of ketones and synthesis of quinolines on the basis of control experiments and detection of reaction intermediates.
- Singh, Anshu,Maji, Ankur,Joshi, Mayank,Choudhury, Angshuman R.,Ghosh, Kaushik
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p. 8567 - 8587
(2021/06/30)
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- Ruthenium complex and preparation method thereof and catalytic application
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The invention discloses a ruthenium complex and a preparation method thereof and catalytic application. The ruthenium complex is reported for the first time. Research finds that the ruthenium complexhas the activity of catalytically synthesizing quinazoline and derivatives thereof or catalytically synthesizing quinoline and derivatives thereof. When the ruthenium complex provided by the inventionis used for catalytic synthesis of quinazoline and derivatives thereof or quinoline and derivatives thereof, the ruthenium complex has the advantages of mild reaction conditions, wide substrate range, high catalytic product yield and good functional group tolerance, and is significantly superior to the prior art.
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Paragraph 0104-0106; 0111-0112
(2021/01/24)
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- A cobalt-catalyzed method for synthesizing quinoline and quinazoline compounds
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The present invention discloses a cobalt-catalyzed synthesis of quinoline and quinazoline compounds, by a benzene compound with amino and hydroxyl groups or benzonitrile compounds as raw materials, in the presence of a catalyst and a base by a receptor-fr
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Paragraph 0011; 0037
(2022/01/10)
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- A Proton-Responsive Pyridyl(benzamide)-Functionalized NHC Ligand on Ir Complex for Alkylation of Ketones and Secondary Alcohols
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A Cp*Ir(III) complex (1) of a newly designed ligand L1 featuring a proton-responsive pyridyl(benzamide) appended on N-heterocyclic carbene (NHC) has been synthesized. The molecular structure of 1 reveals a dearomatized form of the ligand. The protonation of 1 with HBF4 in tetrahydrofuran gives the corresponding aromatized complex [Cp*Ir(L1H)Cl]BF4 (2). Both compounds are characterized spectroscopically and by X-ray crystallography. The protonation of 1 with acid is examined by 1H NMR and UV-vis spectra. The proton-responsive character of 1 is exploited for catalyzing α-alkylation of ketones and β-alkylation of secondary alcohols using primary alcohols as alkylating agents through hydrogen-borrowing methodology. Compound 1 is an effective catalyst for these reactions and exhibits a superior activity in comparison to a structurally similar iridium complex [Cp*Ir(L2)Cl]PF6 (3) lacking a proton-responsive pendant amide moiety. The catalytic alkylation is characterized by a wide substrate scope, low catalyst and base loadings, and a short reaction time. The catalytic efficacy of 1 is also demonstrated for the syntheses of quinoline and lactone derivatives via acceptorless dehydrogenation, and selective alkylation of two steroids, pregnenolone and testosterone. Detailed mechanistic investigations and DFT calculations substantiate the role of the proton-responsive ligand in the hydrogen-borrowing process.
- Kaur, Mandeep,U Din Reshi, Noor,Patra, Kamaless,Bhattacherya, Arindom,Kunnikuruvan, Sooraj,Bera, Jitendra K.
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supporting information
p. 10737 - 10748
(2021/06/15)
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- Zinc Stabilized Azo-anion Radical in Dehydrogenative Synthesis of N-Heterocycles. An Exclusively Ligand Centered Redox Controlled Approach
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Herein we report an exclusively ligand-centered redox controlled approach for the dehydrogenation of a variety of N-heterocycles using a Zn(II)-stabilized azo-anion radical complex as the catalyst. A simple, easy-to-prepare, and bench-stable Zn(II)-complex (1b) featuring the tridentate arylazo pincer, 2-((4-chlorophenyl)diazenyl)-1,10-phenanthroline, in the presence of zinc-dust, undergoes reduction to form the azo-anion radical species [1b]- which efficiently dehydrogenates various saturated N-heterocycles such as 1,2,3,4-tetrahydro-2-methylquinoline, 1,2,3,4-tetrahydro-isoquinoline, indoline, 2-phenyl-2,3-dihydro-1H-benzoimidazole, 2,3-dihydro-2-phenylquinazolin-4(1H)-one, and 1,2,3,4-tetrahydro-2-phenylquinazolines, among others, under air. The catalyst has further been found to be compatible with the cascade synthesis of these N-heterocycles via dehydrogenative coupling of alcohols with other suitable coupling partners under air. Mechanistic investigation reveals that the dehydrogenation reactions proceed via a one-electron hydrogen atom transfer (HAT) pathway where the zinc-stabilized azo-anion radical ligand abstracts the hydrogen atom from the organic substrate(s), and the whole catalytic cycle proceeds via the exclusive involvement of the ligand-centered redox events where the zinc acts only as the template.
- Das, Siuli,Mondal, Rakesh,Chakraborty, Gargi,Guin, Amit Kumar,Das, Abhishek,Paul, Nanda D.
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p. 7498 - 7512
(2021/06/30)
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- Porous FeO(OH) Dispersed on Mg-Al Hydrotalcite Surface for One-Pot Synthesis of Quinoline Derivatives
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The use of ubiquities elements such as iron instead of expensive precious metals as catalysts is one goal toward realizing environmentally benign synthetic chemistry. Here, we report that porous FeO(OH) dispersed on Mg?Al hydrotalcite acts as a bifunctional heterogeneous catalyst in the one-pot synthesis of 2-substituted quinoline derivatives through dehydrogenative oxidation-cyclization reactions. The catalyst was prepared by a simple grafting method using FeCl3 and Mg?Al hydrotalcite. The prepared porous FeO(OH) possesses a higher surface area than those previously reported for α-FeO(OH) particles. The one-pot quinoline synthesis proceeded effectively under non-noble-metal catalysis in air without requiring additional homogeneous bases or solvents.
- Motokura, Ken,Ozawa, Nao,Sato, Risako,Manaka, Yuichi,Chun, Wang-Jae
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p. 2915 - 2921
(2021/05/27)
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- Ruthenium-catalyzed acceptorless dehydrogenative coupling of o-aminobenzyl alcohols with ketones to quinolines in the presence of carbonate salt
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A ruthenium complex bearing a functional 2,2′-bibenzimidazole ligand [(p-cymene)Ru(BiBzImH2)Cl][Cl] was designed, synthesized and found to be a general and highly efficient catalyst for the synthesis of quinolines via acceptorless dehydrogenative coupling of o-aminobenzyl alcohols with ketones in the presence of carbonate salt. It was confirmed that NH units in the ligand are crucial for catalytic activity. The application of this catalytic system for the scale-gram synthesis of biologically active molecular was also undertaken. Notably, this research exhibits new potential of metal–ligand bifuctional catalysts for acceptorless dehydrogenative reactions.
- Xu, Xiangchao,Ai, Yao,Wang, Rongzhou,Liu, Liping,Yang, Jiazhi,Li, Feng
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p. 340 - 349
(2021/02/27)
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- The preparation of a Co@C3N4catalyst and applications in the synthesis of quinolines from 2-aminobenzyl alcohols with ketones
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An unsymmetrical diphenylphosphino-pyridinyl-triazole ligand was synthesized and characterized through IR, NMR and MS and the corresponding earth-abundant metal complex (cobalt) was prepared. Considering energy consumption and environmental friendliness, it is necessary to turn this diphenylphosphino-pyridinyl-triazole cobalt complex into a recyclable catalyst, which could easily be reused. Therefore, a heterogeneous catalyst was synthesized through Co-doping of C3N4, and the Co-nanoparticles on C3N4revealed high catalytic activity for the synthesis of quinolines with good recovery performance.
- Cao, Fei,Mao, Anruo,Yang, Bobin,Ge, Chenyang,Wang, Dawei
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supporting information
p. 6768 - 6772
(2021/04/22)
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- [(PPh3)2NiCl2]-Catalyzed C-N bond formation reaction via borrowing hydrogen strategy: Access to diverse secondary amines and quinolines
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Commercially available [(PPh3)2NiCl2] was found to be an efficient catalyst for the mono-N-alkylation of (hetero)- A romatic amines, employing alcohols to deliver diverse secondary amines, including the drug intermediates chloropyramine (5b) and mepyramine (5c), in excellent yields (up to 97%) via the borrowing hydrogen strategy. This method shows a superior activity (TON up to 10000) with a broad substrate scope at a low catalyst loading of 1 mol % and a short reaction time. Further, this strategy is also successful in accessing various quinoline derivatives following the acceptorless dehydrogenation pathway.
- Donthireddy,Pandey, Vipin K.,Rit, Arnab
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p. 6994 - 7001
(2021/06/09)
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- Efficient access to quinolines and quinazolines by ruthenium complexes catalyzed acceptorless dehydrogenative coupling of 2-aminoarylmethanols with ketones and nitriles
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Treatment of N,N,O-tridentate pyrazolyl-pyridinyl-alcohol ligands, 2-(CR1R2OH)-6-[3,5-(R3)2C3HN2]C5H3N (R1 = R2 = Me, R3 = H (L1H); R1 = Me, R2 = Ph, R3 = H (L2H); R1 = R2 = Ph, R3 = H (L3H); R1 = R2 = R3 = Me (L4H)) with RuCl3?xH2O in refluxing EtOH afforded the corresponding Ru(III) complexes L2RuCl (1a-1d), which were well characterized by IR, HR-MS and X-ray single crystal structural determination. These Ru complexes showed similarly high catalytic performance for both dehydrogenative couplings of 2-aminoarylmethanols with ketones and nitriles, giving the quinolines and quinazolines in good to excellent yields. This protocol provides an atom-economical and sustainable route to access various structurally important quinoline and quinazoline derivatives by using phosphine-free ligand based Ru catalysts.
- Feng, Qi,Han, Zhangang,Hao, Zhiqiang,Huo, Shuaicong,Kong, Siqi,Lin, Jin,Lu, Guo-Liang,Zeng, Guang
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- Direct C-H Arylation and Alkylation of Electron-Deficient Heteroaromatic Compounds with Organozinc Reagents
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A direct and convenient method for the C-H arylation and alkylation of electron-deficient N-heteroarenes with readily available organozinc reagents has been developed. This transformation could be readily performed in the absence of a transition-metal catalyst and external oxidants, affording a wide range of substituted heteroarenes with good functional group tolerance in good to excellent yields. The developed simple protocol is scalable to the gram level and suitable for late-stage modification of bioactive molecules and drugs.
- Peng, Zhihua,Yu, Chuanman,Wang, Yilei,Wei, Dongyue,Jiang, Cuiyu
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supporting information
p. 3678 - 3688
(2021/11/16)
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- NiH-Catalyzed Hydroamination/Cyclization Cascade: Rapid Access to Quinolines
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Despite the significant success of metal-H-catalyzed hydroamination methodologies, considerable limitations still exist in the selective hydroamination of alkynes, especially for terminal alkynes. Herein, we develop a highly efficient NiH catalytic system that activates readily available alkynes for a cascade hydroamination/cyclization reaction with anthranils. This mild, operationally simple protocol is amenable to a wide array of alkynes including terminal and internal, aryl and alkyl, electron-deficient and electron-rich ones, delivering structurally diverse quinolines in useful to excellent yields (>80 examples, up to 93% yield). The utility of this procedure is exhibited in the late-stage functionalization of several natural products and in the concise synthesis of an antitumor molecule graveolinine and a triplex DNA intercalator. Preliminary mechanistic experiments suggest an alkenylnickel-mediated alkyne hydroamination and an intramolecular cyclization/aromatization of putative enamine intermediates.
- Chen, Qian,Gao, Yang,Hu, Xiao-Qiang,Huo, Yanping,Li, Xianwei,Yang, Simin
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p. 7772 - 7779
(2021/06/30)
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- Mild and efficient copper-catalyzed oxidative cyclization of oximes with 2-aminobenzyl alcohols at room temperature: synthesis of polysubstituted quinolines
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A simple and efficient ligand-free Cu-catalyzed protocol for the synthesis of polysubstituted quinolinesviaoxidative cyclization of oxime acetates with 2-aminobenzyl alcohols at room temperature has been developed. The presented approach provides a new synthetic pathway leading to polysubstituted quinolines with good functional group tolerance under mild conditions. Moreover, this transformation can be applied for the preparation of quinolines on a gram scale. Oxime acetates serve as the internal oxidants in the reactions, thus making this method very attractive.
- Liu, Yan-Yun,Wei, Yang,Huang, Zhi-Hui,Liu, Yilin
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supporting information
p. 659 - 666
(2021/02/06)
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- Formate-Mediated Cross-Electrophile Reductive Coupling of Aryl Iodides and Bromopyridines
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Two catalytic systems for the formate-mediated cross-electrophile reductive coupling of aryl iodides with 6-bromopyridines are described. Using homogenous rhodium or heterogeneous palladium catalysts, the products of reductive biaryl cross-coupling could
- Schwartz, Leyah A.,Spielmann, Kim,Swyka, Robert A.,Xiang, Ming,Krische, Michael J.
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p. 298 - 301
(2020/10/19)
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- Kinetic Resolution of 2,2-Disubstituted Dihydroquinolines through Chiral Phosphoric Acid-Catalyzed C6-Selective Asymmetric Halogenations
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A novel kinetic resolution of 2,2-disubstituted dihydroquinolines was achieved by regioselective asymmetric halogenations enabled by chiral phosphoric acid catalysis. A series of dihydroquinolines bearing 2,2-disubstitutions were well-tolerated in these reactions, generating both the recovered dihydroquinolines and C-6-brominated products with high enantioselectivities, with s-factors up to 149. In addition, this kinetic resolution protocol is also applicable for 2,2-disubstituted tetrahydroquinoline and asymmetric iodonation reaction.
- Chen, Yunrong,He, Yu-Peng,Liu, Wei,Tao, Houchao,Yang, Xiaoyu,Zhao, Fei,Zhu, Chaofan
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supporting information
p. 4104 - 4108
(2021/06/27)
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- Visible-Light-Mediated Oxidative Cyclization of 2-Aminobenzyl Alcohols and Secondary Alcohols Enabled by an Organic Photocatalyst
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This paper describes a visible-light-mediated oxidative cyclization of 2-aminobenzyl alcohols and secondary alcohols to produce quinolines at room temperature. This photocatalytic method employed anthraquinone as an organic small-molecule catalyst and DMSO as an oxidant. According to this present procedure, a series of quinolines were prepared in satisfactory yields.
- Xu, Jing-Xiu,Pan, Nan-Lian,Chen, Jia-Xi,Zhao, Jin-Wu
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p. 10747 - 10754
(2021/08/16)
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- Bioinspired Radical-Mediated Transition-Metal-Free Synthesis of N-Heterocycles under Visible Light
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A redox-active iminoquinone motif connected with π-delocalized pyrene core has been reported that can perform efficient two-electron oxidation of a class of substrates. The design of the molecule was inspired by the organic redox cofactor topaquinone (TPQ), which executes amine oxidation in the enzyme, copper amine oxidase. Easy oxidation of both primary and secondary alcohols happened in the presence of catalytic KOtBu, which could reduce the ligand backbone to its iminosemiquinonate form under photoinduced conditions. Moreover, this easy oxidation of alcohols under aerobic condition could be elegantly extended to multi-component, one-pot coupling for the synthesis of quinoline and pyrimidine. This organocatalytic approach is very mild (70 °C, 8 h) compared to a multitude of transition-metal catalysts that have been used to prepare these heterocycles. A detailed mechanistic study proves the intermediacy of the iminosemiquinonate-type radical and a critical hydrogen atom transfer step to be involved in the dehydrogenation reaction.
- K. Bains, Amreen,Ankit, Yadav,Adhikari, Debashis
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p. 324 - 329
(2020/11/30)
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- Ionic-Liquid-Catalyzed Synthesis of Imines, Benzimidazoles, Benzothiazoles, Quinoxalines and Quinolines through C?N, C?S, and C?C Bond Formation
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We report the tetramethyl ammonium hydroxide catalyzed oxidative coupling of amines and alcohols for the synthesis of imines under metal-free conditions by utilizing oxygen from air as the terminal oxidant. Under the same conditions, with ortho-phenylene diamines and 2-aminobenzenethiols the corresponding benzimidazoles and benzothiazoles were obtained. Quinoxalines were obtained from ortho-phenylene diamines and 1-phenylethane-1,2-diol, the conditions were then extended to the synthesis of quinoline building blocks by reaction of 2-amino benzyl alcohols either with 1-phenylethan-1-ol or acetophenone derivatives. The formation of C?N, C?S and C?C bonds was achieved under metal-free conditions. A broad range of amines (aromatic, aliphatic, cyclic and heteroaromatic) as well as benzylic alcohols including heteroaryl alcohols reacted smoothly and provided the desired products. The mild reaction conditions, commercially available catalyst, metal-free, good functional-group tolerance, broad range of products (imines, benzimidazoles, benzothiazoles, quinoxalines and quinolines) and applicability at gram scale reactions are the advantages of the present strategy.
- Adimurthy, Subbarayappa,Badhani, Gaurav,Joshi, Abhisek
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p. 6705 - 6716
(2021/12/31)
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- Continuous Flow Synthesis of Quinolines via a Scalable Tandem Photoisomerization-Cyclization Process
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A continuous photochemical process is presented that renders a series of quinoline products via an alkene isomerization and cyclocondensation cascade. It is demonstrated that a high-power LED lamp generates the desired targets with higher productivity and efficiency than a medium-pressure Hg-lamp. The scope of this tandem process is established and allows for the generation of various substituted quinolines in high yields and with throughputs of greater than one gram per hour. Finally, this effective flow process is coupled with a telescoped hydrogenation reaction to render a series of tetrahydroquinolines including the antimalarial natural product galipinine.
- Di Filippo, Mara,Baumann, Marcus
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p. 6199 - 6211
(2020/08/26)
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- Enantioselective Synthesis of Tetrahydroquinolines via One-Pot Cascade Biomimetic Reduction?
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A novel and efficient protocol for the synthesis of chiral tetrahydroquinoline derivatives with excellent enantioselectivities and high yields has been developed through one-pot cascade biomimetic reduction. The detailed reaction pathway includes the acid-catalyzed and ruthenium-catalyzed formation of aromatic quinoline intermediates and biomimetic asymmetric reduction.
- Zhao, Zi-Biao,Li, Xiang,Chen, Mu-Wang,Wu, Bo,Zhou, Yong-Gui
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p. 1691 - 1695
(2020/11/03)
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- Efficient Organoruthenium Catalysts for α-Alkylation of Ketones and Amide with Alcohols: Synthesis of Quinolines via Hydrogen Borrowing Strategy and their Mechanistic Studies
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A new family of phosphine free organometallic ruthenium(II) catalysts (Ru1–Ru4) supported by bidentate NN Schiff base ligands (L1–L4 where L1=N,N-dimethyl-4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazineylidene)methyl) aniline, L2=N,N-diethyl-4-((2-phenyl-2-(pyridin-2-ylmethyl)hydrazineylidene)methyl)aniline, L3=N,N-dimethyl-4-((2-phenyl-2-(pyridin-2-yl)hydrazineylidene)methyl)- aniline and L4=N,N-diethyl-4-((2-phenyl-2-(pyridin-2-yl)hydrazineylidene)methyl) aniline) was prepared and characterized. These half-sandwich complexes acted as catalysts for C?C bond formation and exhibited excellent performance in the dehydrogenative coupling of ketones and amides. In the synthesis of C–C bonds, alcohols were utilized as the alkylating agent. A broad range of substrates, including sterically hindered ketones and alcohols, were well tolerated under the optimized conditions (TON up to 47000 and TOF up to 11750 h?1). This ruthenium (II) catalysts were also active towards the dehydrogenative cyclization of o-amino benzyl alcohol for the formation of quinolines derivatives. Various polysubstituted quinolines were synthesized in moderate to excellent yields (TON up to 71000 and TOF up to 11830 h?1). Control experiments were carried out and the ruthenium hydride intermediate was characterized to support the reaction mechanism and a probable reaction pathway of dehydrogenative coupling for the C?C bond formation has been proposed.
- Maji, Ankur,Singh, Anshu,Singh, Neetu,Ghosh, Kaushik
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p. 3108 - 3125
(2020/05/18)
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- Half-Sandwich Ruthenium Complexes for One-Pot Synthesis of Quinolines and Tetrahydroquinolines: Diverse Catalytic Activity in the Coupled Cyclization and Hydrogenation Process
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Four types of half-sandwich ruthenium complexes with an N,O-coordinate mode based on hydroxyindanone-imine ligands have been prepared in good yields. These stable ruthenium complexes exhibited high activity in the catalytic synthesis of quinolines from the reactions of amino alcohols with different types of ketones or secondary alcohols under very mild conditions. Moreover, the methodology for the direct one-pot synthesis of tetrahydroquinoline derivatives from amino alcohols and ketones has been also developed on the basis of the continuous catalytic activity of this ruthenium catalyst in the selective hydrogenation of the obtained quinoline derivatives with a low catalyst loading. The corresponding products, quinolines and tetrahydroquinoline derivatives, were afforded in good to excellent yields. The efficient and diverse catalytic activity of these ruthenium complexes suggested their potential large-scale application. All of the ruthenium complexes were characterized by various spectroscopies to confirm their structures.
- Yun, Xue-Jing,Zhu, Jing-Wei,Jin, Yan,Deng, Wei,Yao, Zi-Jian
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supporting information
p. 7841 - 7851
(2020/06/04)
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- Superbase-Mediated Indirect Friedl?nder Reaction: A Transition Metal-Free Oxidative Annulation toward Functionalized Quinolines
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A superbase mediated indirect Friedl?nder reaction towards functionalized quinolines has been realized. The reaction was performed with o-aminobenzyl alcohol and ketones having an active methylene moiety in the presence of KOH and in DMSO. The reaction proceeds predominantly via initial formation of an imine intermediate and subsequent oxidation of the benzyl alcohol functionality and condensation to afford substituted quinolines. We could also demonstrate that a minor fraction of the reaction proceeds via a chalcone intermediate. The transition metal-free oxidative annulation was found to be general affording 2-substituted, 2,3-disubstituted/fused or multi-substituted quinolines. The reaction was extended towards the functionalization of natural products and the applicability of the reaction for gram-scale synthesis of quinolines was also demonstrated.
- Rahul,Nitha,Omanakuttan, Vishnu K.,Babu, Sheba Ann,Sasikumar,Praveen, Vakayil K.,Hopf, Henning,John, Jubi
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p. 3081 - 3089
(2020/05/08)
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- Pyridine mediated transition-metal-free direct alkylation of anilines using alcohols: via borrowing hydrogen conditions
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Herein, we report pyridine and other similar azaaromatics as efficient biomimetic hydrogen shuttles for a transition-metal-free direct N-alkylation of aryl and heteroaryl amines using a variety of benzylic and straight chain alcohols. Mechanistic studies including deuterium labeling and the isolation of dihydro-intermediates of the benzannulated pyridine confirmed the role of pyridine and a borrowing hydrogen process operating in these reactions. In addition, we have extended this methodology for the development of dehydrogenative synthesis of quinolines and indoles, as well as the transfer hydrogenation of ketones. This journal is
- Pothikumar, Rajagopal,Bhat, Venugopal T,Namitharan, Kayambu
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supporting information
p. 13607 - 13610
(2020/11/17)
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- Synthesis of Acyl Fluorides via DAST-Mediated Fluorinative C-C Bond Cleavage of Activated Ketones
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A new protocol for preparation of acyl fluorides was developed by recognizing activated ketones as starting materials. The method provides a different scope compared with previously reported methods that employ carboxylic acids as substrates. A working hypothesis of pull-and-push-driven fluorinative C-C bond cleavage was successfully demonstrated by the simple addition of diethylaminosulfur trifluoride (DAST) derivatives to α-oximinoketones. The designed reaction system led to a highly efficient and chemoselective reaction. The wide availability of the ketones allowed for a range of synthetically useful aryloyl and aliphatic acyl fluorides including those containing chiral skeletons. The method is mild, fast, scalable, and potentially one-pot operative.
- Kim, Danhee,Lim, Hee Nam
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p. 7465 - 7469
(2020/10/09)
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- Organometal-Free Arylation and Arylation/Trifluoroacetylation of Quinolines by Their Reaction with CF3-ynones and Base-Induced Rearrangement
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The reaction of quinolines with CF3-ynones resulted in the formation of 1,3-oxazinoquinolines. Subsequent treatment of the reaction mixture with a base initiated deep structural transformation of primary products. Both steps proceed in very high yield. As a result, unusual rearrangement of 1,3-oxazinoquinolines to form either 2-arylquinolines or 2-aryl-3-trifluoroacetylquinolines was discovered. The decisive role of the base in the reaction direction was shown. Using these reactions, highly efficient pathways to 2-arylquinolines and 2-aryl-3-trifluoroacetylquinolines were elaborated to provide the corresponding compounds in high yields using a simple one-pot procedure. The possible mechanism of rearrangement is discussed.
- Muzalevskiy, Vasiliy M.,Belyaeva, Kseniya V.,Trofimov, Boris A.,Nenajdenko, Valentine G.
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p. 9993 - 10006
(2020/09/09)
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- Preparation of 2-Arylquinolines from 2-Arylethyl Bromides and Aromatic Nitriles with Magnesium and N -Iodosuccinimide
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Treatment of 2-arylethylmagnesium bromides, prepared from 2-arylethyl bromides and magnesium, with aromatic nitriles, followed by reaction with water and then with N -iodosuccinimide under irradiation with a tungsten lamp, gave the corresponding 2-arylquinolines in good to moderate yields under transition-metal-free conditions. 2-Alkylquinolines could be also obtained in moderate yields by the same procedure with 2-arylethyl bromides, magnesium, aliphatic nitriles bearing a secondary alkyl group, and N -iodosuccinimide.
- Naruto, Hiroki,Togo, Hideo
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p. 1122 - 1130
(2020/04/01)
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- Visible-light-induced photoxidation-Povarov cascade reaction: synthesis of 2-arylquinoline through alcohol andN-benzylanilines under mild conditionsviaAg/g-C3N4nanometric semiconductor catalyst
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With a Ag/g-C3N4nanometric semiconductor as the photocatalyst, 2-arylquinolines were synthesized through a photoxidation-Povarov cascade reaction ofN-benzylanilines and alcohols under visible light irradiation. Under the blue light of a 3 W LED, good yields were achieved for various substrates in oxygen at room temperature. This methodology provides a green and mild alternative for the formation of 2-arylquinoline derivatives. Remarkably, the Ag/g-C3N4nanocomposite can be conveniently recovered and reused several times with satisfying yields.
- Wang, Peng,Wang, Xiaowen,Niu, Xiyu,Zhu, Li,Yao, Xiaoquan
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supporting information
p. 4840 - 4843
(2020/05/13)
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- σ-Bond initiated generation of aryl radicals from aryl diazonium salts
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σ-Bond nucleophiles and molecular oxygen transform aryl diazonium salts into aryl radicals. Experimental and computational studies show that Hantzsch esters transfer hydride to aryl diazonium species, and that oxygen initiates radical fragmentation of the diazene intermediate to produce aryl radicals. The operational simplicity of this addition-fragmentation process for the generation of aryl radicals, by a polar-radical crossover mechanism, has been illustrated in a variety of bond-forming reactions.
- Chan, Bun,McErlean, Christopher S. P.,Nashar, Philippe E.,Tatunashvili, Elene
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supporting information
p. 1812 - 1819
(2020/03/17)
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- Regiodivergent C-H Alkylation of Quinolines with Alkenes by Half-Sandwich Rare-Earth Catalysts
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The regiodivergent catalysis of C-H alkylation with alkenes is of great interest and importance but has remained hardly explored to date. We report herein the first regiodivergent C-H alkylation of quinolines with alkenes by half-sandwich rare-earth catal
- Lou, Shao-Jie,Zhang, Liang,Luo, Yong,Nishiura, Masayoshi,Luo, Gen,Luo, Yi,Hou, Zhaomin
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supporting information
p. 18128 - 18137
(2020/12/02)
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- Fe2O3@[proline]–CuMgAl–LDH: A magnetic bifunctional copper and organocatalyst system for one-pot synthesis of quinolines and 2H-indazoles in green media
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A novel magnetic core–shell Fe2O3@[proline]–CuMgAl–L(ayered)D(ouble)H(ydroxide) was designed as an efficient bifunctional catalytic system. To this end, Cu (II) was combined with Mg and Al in the LDH structure and l-proline was intercalated between LDH layers in order to perform a straightforward synthesis of quinolines and 2H-indazoles as two important pharmaceutical N-aryl-substituted heterocyclic compounds. In this regard, a facile method was employed through consecutive condensation under a mild conditions in choline azide media, which played the role of a reagent and a solvent to avoid toxic solvents and hazardous azidation reagents. These techniques provided considerable improvement in terms of using green media, reducing starting materials, reaching higher yields and offering a shorter reaction time and lower temperature. In conclusion, it was found that the catalyst could be reused five times with no significant loss of activity.
- Esfandiary, Naghmeh,Heydari, Akbar
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- Ruthenium(II) Complexes of Heteroditopic N-Heterocyclic Carbene Ligands: Efficient Catalysts for C-N Bond Formation via a Hydrogen-Borrowing Strategy under Solvent-Free Conditions
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Both imidazol-2-ylidene (ImNHC) and 1,2,3-triazol-5-ylidene (tzNHC) have evolved to be elite groups of N-heterocyclic carbene (NHC) ligands for homogeneous catalysis. To develop efficient ruthenium(II)-based catalysts incorporating these ligands for C-N bond-forming reactions via hydrogen-borrowing methodology, we utilized chelating ligands integrated with ImNHC and mesoionic tzNHC donors connected via a CH2 spacer with a diverse triazole backbone. The synthesized ruthenium(II) complexes 3 are found to be highly efficient for C-N bond formation across a wide range of primary amine and alcohol substrates under solvent-free conditions, and among all of the complexes studied here, catalyst 3a with a mesityl substituent displayed maximum activity. To our delight, catalyst 3a is also effective for the selective mono-N-methylation of various anilines utilizing methanol as a coupling partner, known to be relatively more difficult than other alcohols. Furthermore, complex 3a also delivers various substituted quinolines successfully via the reaction of 2-aminobenzyl alcohol with several secondary alcohols. Importantly, catalyst 3a exhibited the highest activity among the reported ruthenium(II) complexes for both the N-benzylation of aniline [achieving a turnover number (TON) of 50000] and the realization of quinoline 8a by reacting 2-aminobenzyl alcohol with 2-phenylethanol (attaining a TON of 30000).
- Donthireddy,Mathoor Illam, Praseetha,Rit, Arnab
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p. 1835 - 1847
(2020/01/31)
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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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- Homogeneous Nickel-Catalyzed Sustainable Synthesis of Quinoline and Quinoxaline under Aerobic Conditions
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Dehydrogenative coupling-based reactions have emerged as an efficient route toward the synthesis of a plethora of heterocyclic rings. Herein, we report an efficacious, nickel-catalyzed synthesis of two important heterocycles such as quinoline and quinoxaline. The catalyst is molecularly defined, is phosphine-free, and can operate at a mild reaction temperature of 80 °C. Both the heterocycles can be easily assembled via double dehydrogenative coupling, starting from 2-aminobenzyl alcohol/1-phenylethanol and diamine/diol, respectively, in a shorter span of reaction time. This environmentally benign synthetic protocol employing an inexpensive catalyst can rival many other transition-metal systems that have been developed for the fabrication of two putative heterocycles. Mechanistically, the dehydrogenation of secondary alcohol follows clean pseudo-first-order kinetics and exhibits a sizable kinetic isotope effect. Intriguingly, this catalyst provides an example of storing the trapped hydrogen in the ligand backbone, avoiding metal-hydride formation. Easy regeneration of the oxidized form of the catalyst under aerobic/O2 oxidation makes this protocol eco-friendly and easy to handle.
- Bains, Amreen K.,Singh, Vikramjeet,Adhikari, Debashis
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p. 14971 - 14979
(2020/11/30)
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- Photoarylation of Pyridines Using Aryldiazonium Salts and Visible Light: An EDA Approach
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A metal-free methodology for the photoarylation of pyridines, in water, is described giving 2 and 4-arylated-pyridines in yields up to 96percent. The scope of the aryldiazonium salts is presented showing important results depending on the nature and position of the substituent group in the diazonium salt, that is, electron-donating or electron-withdrawing in the ortho, meta, or para positions. Further heteroaromatics were also successfully photoarylated. Mechanistic studies and comparison between our methodology and similar metal-catalyzed procedures are presented, suggesting the occurrence of a visible-light EDA complex which generates the aryl radical with no need for an additional photocatalyst.
- Bartolomeu, Aloisio De A.,Brocksom, Timothy J.,De Oliveira, Kleber T.,No?l, Timothy,Silva, Rodrigo C.
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- Transition-Metal-Free Desulfinative Cross-Coupling of Heteroaryl Sulfinates with Grignard Reagents
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A mild cross-coupling reaction of heteroaryl sulfinates with Grignard reagents has been developed under transition-metal-free conditions. This study provides an example of the SO22- as a leaving group in an aromatic system and an effective methodology for the construction of C-C bond.
- Wei, Jun,Liang, Huamin,Ni, Chuanfa,Sheng, Rong,Hu, Jinbo
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supporting information
(2019/02/05)
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- Sustainable synthesis of N-heterocycles in water using alcohols following the double dehydrogenation strategy
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The present study describes the first example of synthesis of pharmaceutically relevant N-heterocycles like substituted quinolines, acridines and 1,8-naphthyridines in water under air using alcohols in presence of a new water soluble Ir-complex. The viability and efficiency of this approach was demonstrated by the efficient synthesis of biologically active natural product (±)-galipinine and gram scale synthesis of various N-heteroaromatics. Several kinetic experiments and DFT calculations were carried out to support the plausible reaction mechanism which disclosed that this system followed a concerted outer sphere mechanism for the dehydrogenation of alcohols.
- Maji, Milan,Chakrabarti, Kaushik,Panja, Dibyajyoti,Kundu, Sabuj
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- A nanoscale iron catalyst for heterogeneous direct: N - And C -alkylations of anilines and ketones using alcohols under hydrogen autotransfer conditions
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Here, we report a commercially available nanoscale Fe catalyst for heterogeneous direct N- and C-alkylation reactions of anilines and methyl ketones with alcohols. A hydrogen autotransfer mechanism has been found to operate in these reactions by deuterium labelling studies. In addition, dehydrogenative quinoline synthesis has been demonstrated from amino benzyl alcohols and acetophenones.
- Nallagangula, Madhu,Sujatha, Chandragiri,Bhat, Venugopal T.,Namitharan, Kayambu
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supporting information
p. 8490 - 8493
(2019/07/22)
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- N-Heterocyclic carbene copper catalyzed quinoline synthesis from 2-aminobenzyl alcohols and ketones using DMSO as an oxidant at room temperature
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A facile and practical process for the synthesis of quinolines through an N-heterocyclic carbene copper catalyzed indirect Friedl?nder reaction from 2-aminobenzyl alcohol and aryl ketones using DMSO as an oxidant at room temperature is reported. A series of quinolines were synthesized in acceptable yields.
- Xu, Jingxiu,Chen, Qingmao,Luo, Zhigao,Tang, Xiaodong,Zhao, Jinwu
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p. 28764 - 28767
(2019/09/30)
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- Synthesis and Structures of Arene Ruthenium (II)–NHC Complexes: Efficient Catalytic α-alkylation of ketones via Hydrogen Auto Transfer Reaction
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A panel of six new arene Ru (II)-NHC complexes 2a-f, (NHC?=?1,3-diethyl-(5,6-dimethyl)benzimidazolin-2-ylidene 1a, 1,3-dicyclohexylmethyl-(5,6-dimethyl)benzimidazolin-2-ylidene 1b and 1,3-dibenzyl-(5,6-dimethyl)benzimidazolin-2-ylidene 1c) were synthesized from the transmetallation reaction of Ag-NHC with [(η6-arene)RuCl2]2 and characterized. The ruthenium (II)-NHC complexes 2a-f were developed as effective catalysts for α-alkylation of ketones and synthesis of bioactive quinoline using primary/amino alcohols as coupling partners respectively. The reactions were performed with 0.5?mol% catalyst load in 8?h under aerobic condition and the maximum yield was up to 96%. Besides, the different alkyl wingtips on NHC and arene moieties were studied to differentiate the catalytic robustness of the complexes in the transformations.
- Balamurugan, Gunasekaran,Balaji, Sundarraman,Ramesh, Rengan,Bhuvanesh, Nattamai S.P.
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- Iridium(I)-Catalyzed C-C and C-N Bond Formation Reactions via the Borrowing Hydrogen Strategy
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Iridium(I) complexes having an imidazol-2-ylidene ligand with benzylic wingtips efficiently catalyzed the β-alkylation of secondary alcohols with primary alcohols and acceptorless dehydrogenative cyclization of 2-aminobenzyl alcohol with ketones through a borrowing hydrogen pathway. The β-alkylated alcohols, including cholesterol derivatives, and substituted quinolines were obtained in good yields by using a minute amount of the catalyst with a catalytic amount of NaOH or KOH under the air atmosphere, liberating water (and H2 in the case of quinoline synthesis) as the sole byproduct. Notably, this system demonstrated turnover numbers of 940 000 (for β-alkylation of secondary alcohols with primary alcohols by using down to 0.0001 mol % = 1 ppm of the catalyst) and 9200 (acceptorless dehydrogenative cyclization of 2-aminobenzyl alcohol with ketones).
- Gen?, Serta?,Arslan, Burcu,Gülcemal, Süleyman,Günnaz, Salih,?etinkaya, Bekir,Gülcemal, Derya
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supporting information
p. 6286 - 6297
(2019/05/17)
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- Dehydrogenative Synthesis of Quinolines, 2-Aminoquinolines, and Quinazolines Using Singlet Diradical Ni(II)-Catalysts
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Simple, straightforward, and atom economic methods for the synthesis of quinolines, 2-aminoquinolines, and quinazolines via biomimetic dehydrogenative condensation/coupling reactions, catalyzed by well-defined inexpensive and easy to prepare singlet diradical Ni(II)-catalysts featuring two antiferromagnetically coupled singlet diradical diamine type ligands are described. Various polysubstituted quinolines, 2-aminoquinolines, and quinazolines were synthesized in moderate to good yields from different low-cost and readily accessible starting materials. Several control experiments were carried out to get insight into the reaction mechanism which shows that the nickel and the coordinated diamine ligands participate in a synergistic way during the dehydrogenation of alcohols.
- Chakraborty, Gargi,Sikari, Rina,Das, Siuli,Mondal, Rakesh,Sinha, Suman,Banerjee, Seemika,Paul, Nanda D.
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p. 2626 - 2641
(2019/02/26)
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- An Efficient Mesoporous Cu-Organic Nanorod for Friedl?nder Synthesis of Quinoline and Click Reactions
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Within the green chemistry context, heterogeneous catalysis for the synthesis of N-heterocycles from renewable resources using non-precious metals has garnered great interest in terms of economic and environmental perspectives. Herein, we present a triazine functional hierarchical mesoporous organic polymer (HMOP) with nanorod morphology together with large BET surface area ～1218 m2 g?1, huge pore volumeγτ“;6 mL g?1 and dual micro/mesopore architectures. Subsequent Cu-coordination with nitrogen atoms of the HMOP provides a robust catalyst (Cu-HMOP) to accomplish multi-step cascade reactions for preparation of N-heterocycles by different routes. For instance, the Cu-HMOP efficiently catalyzes one-pot sequential multi-step oxidative dehydrogenative coupling of 2-aminobenzyl alcohol with diverse aromatic ketones to afford corresponding quinolines in excellent isolated yields (up to 97 %). Secondly, the present catalyst exhibits good aerobic oxidative dehydrogenation activity of amines to imines. Thirdly, for “click” reaction involving azides-alkynes, the Cu-HMOP produced quantitative yield for 1,4-disubstituted 1,2,3-triazole derivatives at room temperature using water as solvent. Verification of active metal leaching by a hot filtration test as well as reusability of the retrieved Cu-HMOP catalysts shows a consistent activity in the multi-component quinoline synthesis as model reaction.
- Elavarasan, Samaraj,Bhaumik, Asim,Sasidharan, Manickam
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p. 4340 - 4350
(2019/08/12)
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- Synthesis of 2-Arylisoindoline Derivatives Catalyzed by Reusable 1,2,4-Triazole Iridium on Mesoporous Silica through a Cascade Borrowing Hydrogen Strategy
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Covalent attachment of a 1,2,4-triazole iridium complex to mesoporous MCM-41 generated a heterogeneous catalyst that was found to be effective in the synthesis of 2-aryl isoindolines, quinolines, cyclic amines, and symmetrical secondary amines through a cascade borrowing hydrogen strategy. Interestingly, the supported heterogeneous iridium catalyst prepared from the 1,2,4-triazole iridium complex and mesoporous MCM-41 exhibited high catalytic activity in the preparation of 2-aryl isoindoline derivatives and symmetrical secondary amines. The catalyst system is highly recyclable for at least five times. Besides the important effect of the triazole, iridium sites grafted on siliceous supports can act as multifunctional catalytic centers and thus greatly enhance the catalytic activity of the catalysts. Furthermore, mechanistic experiments revealed that the reaction is initiated by an initial alcohol dehydrogenation and promoted by an iridium hydride intermediate. Importantly, the direct detection of a diagnostic iridium hydride signal confirmed that the synthesis of 2-aryl isoindolines occurs by a borrowing hydrogen process. This work provides an efficient example of isoindolines synthesis through a borrowing hydrogen strategy.
- Yao, Wei,Ge, Chenyang,Zhang, Yilin,Xia, Xiao-Feng,Wang, Long,Wang, Dawei
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supporting information
p. 16099 - 16105
(2019/11/26)
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- Metal-Ligand Cooperative Approach to Achieve Dehydrogenative Functionalization of Alcohols to Quinolines and Quinazolin-4(3 H)-ones under Mild Aerobic Conditions
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A simple metal-ligand cooperative approach for the dehydrogenative functionalization of alcohols to various substituted quinolines and quinazolin-4(3H)-ones under relatively mild reaction conditions (≤90 °C) is reported. Simple and easy-to-prepare air-stable Cu(II) complexes featuring redox-active azo-aromatic scaffolds, 2-arylazo-(1,10-phenanthroline) (L1,2), are used as catalyst. A wide variety of substituted quinolines and quinazolin-4(3H)-ones were synthesized in moderate to good isolated yields via dehydrogenative coupling reactions of various inexpensive and easily available starting materials under aerobic conditions. A few control experiments and deuterium labeling studies were carried out to understand the mechanism of the dehydrogenative coupling reactions, which indicate that both copper and the coordinated azo-aromatic ligand participate in a cooperative manner during the catalytic cycle.
- Das, Siuli,Sinha, Suman,Samanta, Deepannita,Mondal, Rakesh,Chakraborty, Gargi,Branda?, Paula,Paul, Nanda D.
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p. 10160 - 10171
(2019/08/20)
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