- Triarylmethyl Cation-Catalyzed Three-Component Coupling for the Synthesis of Unsymmetrical Bisindolylmethanes
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An efficient synthesis of unsymmetrical bisindolylmethanes has been accomplished using triarylmethyl cations to catalyze the reaction of N-arylimines with two different indoles. Optimization of the organocatalyst by tuning cation stability allows for excellent single addition selectivity when coupled with p-nitrophenyl imines. The optimal catalyst is commercially available, and the reaction minimizes waste and environmental impact by employing a one-to-one ratio of starting materials. The intermediates can be isolated or used in situ in a one-pot two-step reaction to generate unsymmetrical bisindolylmethanes in high yields. The reaction tolerates a broad range of imines with the highest yields observed for electron-poor and neutral imines. A wide range of indole nucleophiles are also successfully employed allowing for the creation of a large variety of unsymmetrical bisindolylmethanes.
- Bardelski, Kevin,Brindle, Cheyenne S.,Chen, Zhenghua,Guarino-Hotz, Melissa,Jones, Vanessa A.,Lucas, Kelly,Patterson, William J.
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supporting information
p. 6737 - 6742
(2021/12/31)
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- Trimethyl Borate-Catalyzed, Solvent-Free Reductive Amination
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Solvent-free reductive amination of aldehydes and ketones with aliphatic and aromatic amines in high-to-excellent yields has been achieved with sub-stoichiometric trimethyl borate as promoter and ammonia borane as reductant.
- Ramachandran, P. Veeraraghavan,Choudhary, Shivani,Singh, Aman
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p. 4274 - 4280
(2021/03/09)
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- Cyclometalated Half-Sandwich Iridium(III) Complexes: Synthesis, Structure, and Diverse Catalytic Activity in Imine Synthesis Using Air as the Oxidant
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Four air-stable cyclometalated half-sandwich iridium complexes 1-4 with C,N-donor Schiff base ligands were prepared through C-H activation in moderate-to-good yields. These complexes have been well characterized, and their exact structure was elaborated on by single-crystal X-ray analysis. The iridium(III) complexes 1-4 showed good catalytic activity in the imine synthesis under open-flask conditions (air as the oxidant) from primary amine oxidative homocoupling, secondary amine dehydrogenation, and the cross-coupling reaction of amine and alcohol. Substituents bonded on the ligands of the iridium complexes displayed little effect on the catalytic efficiency. The stability and good catalytic efficiency of the iridium catalysts, mild reaction conditions, and substrate universality showed their potential application in industrial production.
- Li, Rong-Jian,Ling, Chun,Lv, Wen-Rui,Deng, Wei,Yao, Zi-Jian
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p. 5153 - 5162
(2021/05/04)
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- T3P-promoted synthesis of a series of novel 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones
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A series of 11 novel 3-aryl-2-phenyl-2,3-dihydro-4H-1,3-benzothiazin-4-ones was prepared at room temperature by T3P-mediated cyclization of N-aryl-C-phenyl imines with thiosalicylic acid. This provides simple and ready access to N-aryl compounds in this family, which have been generally difficult to prepare.
- Silverberg, Lee J.,Pacheco, Carlos,Sahu, Debashish,Scholl, Peter,Sobhi, Hany F.,Bachert, Joshua T.,Bandholz, Kaitlyn,Bendinsky, Ryan V.,Bradley, Heather G.,Colburn, Baylee K.,Coyle, David J.,Dahl, Jonathon R.,Felty, Megan,Fox, Ryan F.,Gonzalez, Kyanna M.,Islam, Jasra M.,Koperna, Stacy E.,Moyer, Quentin J.,Noble, Duncan J.,Ramirez, Melissa E.,Yang, Ziwei
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p. 1797 - 1805
(2020/02/05)
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- Cross dehydrogenative coupling strategy for allylation of benzylanilines promoted by DDQ
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A cross dehydrogenative coupling strategy for allylation of benzylanilines promoted by DDQ is reported, which uses nonmetallic quinone DDQ as an oxidant in the allylation of N-benzylanilines under mild conditions. C–C bond with high selectivity and activity was constructed in this reaction and homoallylic amines were obtained with yields of up to 99%.
- Xiong, Ruimei,Hussain, Muhammad Ijaz,Liu, Qing,Xia, Wen,Xiong, Yan
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supporting information
(2019/12/11)
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- Catalyst- And solvent-free efficient access to: N -alkylated amines via reductive amination using HBpin
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A sustainable approach which works under catalyst- and solvent-free conditions for the synthesis of structurally diverse secondary amines has been uncovered. This one-pot protocol works efficiently at room temperature and is compatible with a wide range of sterically and electronically diverse aldehydes and primary amines. Notably, this simple process offers scalability, excellent functional group tolerance, chemoselectivity, and is also effective at the synthesis of biologically relevant molecules. This journal is
- Bauri, Somnath,Pandey, Vipin K.,Rit, Arnab
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supporting information
p. 3853 - 3857
(2020/07/27)
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- Catalytic activity of Mg-Al hydrotalcites and derived mixed oxides for imination reactionsviaan oxidative-dehydrogenation mechanism
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The catalytic activities of Mg-Al hydrotalcites and derived Mg-Al mixed oxides were studied for the imination of benzylic substrates (benzyl amine and benzyl alcohol), with aniline as a model reaction, to establish a green and cost-effective catalytic (precious metal free) process for imination and tandem reactions utilizing alcohols as reagents. The Mg-Al mixed oxide (Mg/Al ratio = 3.0) was found to be an efficient catalyst for imination reactions to synthesize cross-imines with high selectivity as well as for tandem reactions of alcohols. Basic sites of catalysts adsorb benzylic substrates through the hydrogen of their functional groups (-NH2/-OH) and activate (weaken) benzylic C-H bonds for hydride elimination. Thus, basic sites catalyze the reaction by activating benzylic substrates for oxidative-dehydrogenation (i.e., deprotonation followed by hydride elimination with the help of oxygen) to produce reactive imine/carbonyl intermediates, which undergo subsequent nucleophilic reactions with amine.
- Vala, Naresh,Joshi, Pradyuman A.,Mishra, Manish
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p. 8859 - 8868
(2020/06/08)
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- Air-Stable Half-Sandwich Iridium Complexes as Aerobic Oxidation Catalysts for Imine Synthesis
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Several N,O-coordinate half-sandwich iridium complexes, 1-5, containing constrained bulky β-enaminoketonato ligands were prepared and clearly characterized. Single-crystal X-ray diffraction characterization of these complexes indicates that the iridium center adopts a distorted octahedral geometry. Complexes 1-5 showed good catalytic efficiency in the oxidative homocoupling of primary amines, dehydrogenation of secondary amines, and the oxidative cross-coupling of amines and alcohols, which furnished various types of imines in good yields and high selectivities using O2 as an oxidant under mild conditions. No distinctive substituent effects of the iridium catalysts were observed in these reactions. The diverse catalytic activity, broad substrate scope, mild reaction conditions, and high yields of the products made this catalytic system attractive in industrial processes.
- Deng, Wei,Fan, Xiao-Nan,Ou, Hui-Dan,Yao, Zi-Jian
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supporting information
(2020/04/02)
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- Polyoxometalate catalyzed imine synthesis: Investigation of mechanistic pathways
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The syntheses of imines by oxidative coupling of primary alcohols and amines were achieved by using 2 molpercent polyoxometalate (POM) Na12[WZn3(H2O)2(ZnW9O34)2] (Zn–WZn3) catalyst in the presence of t-BuOK and di-oxygen with excellent conversion (up to 100percent) and selectivity (up to 100percent). Non-noble metal-based POM catalyst in the presence of base represents a new reaction protocol for the selective synthesis of imine from both aromatic and aliphatic primary amines with functional group tolerance. Control experiment shows the formation of di-oxygen bind Zn–WZn3 activated species. The electron-density of POM is mostly situated on the surface oxygen atoms of W–O–W bonds which can engage the alcoholic OH group and helps for the imine selectivity in the second step of imine synthesis.
- Adhikary, Subhasis D.,Mandal, Debaprasad
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supporting information
(2020/05/25)
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- Heterogeneous Catalysis with Basic Compounds to Achieve the Synthesis and C-N Cleavage of Azetidin-2-ones under Microwave Irradiation
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The synthesis of azetidin-2-ones with a completely heterogeneous catalysis is reported. The use of basic compounds as solid catalysts allowed for the synthesis of azetidin-2-ones under microwave irradiation without organic additives such as triethylamine. An excellent catalyst for this transformation was Mg-Al hydroxide (MAH). The present methodology offers the advantages of non-hazardous reaction conditions, short reaction times, high yields, and catalyst reusability. Different substitution groups were tested on the imines and acyl chlorides to explore the scope of the reaction. Unconventional N-C4 bond cleavage was detected in azetidin-2-ones. MAH was characterized by N 2 adsorption-desorption, X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HR-TEM).
- Alcaraz, Yolanda,Cruz, Francisco,De La Cruz, Fabiola N.,Delgado, Francisco,Domínguez, José Manuel,Galván, Adriana,Gomez, Clarisa Villegas,Martínez, Merced,Vázquez, Miguel A.
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supporting information
p. 3625 - 3637
(2019/09/30)
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- 1,4-Dihydropyridine/BF3OEt2 for the reduction of imines: Influences of the amount of added BF3OEt2 and the substitution at N-1 and C-4 of the dihydropyridine ring
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We have evaluated four 1,4-dihydropyridines (DHPs 1a, 1b, 1c and 1d) as reducing agents, which presented free (hydrogenated) or phenyl-substituted N-1 and C-4 positions of the DHP ring. Reactions combining each of the DHP and different amounts of BF3OEt2 were evaluated for the reduction of imine 2a (N-benzylideneaniline). DHP simultaneously substituted at N-1 and C-4 (1a), and DHP substituted at C-4 (1b) gave lower yields for reduction of 2a in comparison with DHPs 1c and 1d (both unsubstituted at the C-4 position). By evaluating the amount of added BF3OEt2 to the reaction mixture, we have found that DHP 1c (substituted at N-1) provided its best yield for amine 3a (82%) when associated with stoichiometric amounts BF3OEt2, while DHP 1d (N-1- and C-4-unsubstituted derivative) was more effective (90% yield) with catalytic quantities of the Lewis acid. The reaction system using DHP 1c under stoichiometric BF3OEt2 could also be successfully applied with additional imine examples and under reductive amination conditions.
- Zattoni, Ingrid F.,Guanaes, Lais D.,Cerqueira, Letícia B.,Pontarolo, Roberto,Ducatti, Diogo R.B.,Duarte, M. Eugênia R.,Noseda, Miguel D.,Trindade, Angela C.L.B.,Gon?alves, Alan G.
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supporting information
(2019/09/12)
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- Facile route for green synthesis of N-benzylideneaniline over bimetallic reduced graphene oxide: chemical reactivity of 2,3,4-substituted derivatives of aniline
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Mn–Co-decorated reduced graphene oxide (Mn–Co–rGO) was prepared by modified condensation method and characterized through XRD, SEM, EDX, FTIR and BET surface area analysis. The prepared sample was explored for its activity in the synthesis of N-benzylideneaniline (N-BA) using benzyl alcohol and PhNH2 as precursors. The catalyst has been used efficiently with high activity and selectivity for oxidation of benzyl alcohol to benzaldehyde in the presence of molecular oxygen, which further react with aniline to produced N-BA with sustainable catalytic activity up to five cycles. Furthermore, the effect of the nature and position of the substituent on aniline on the chemical reactivity of the nucleophile was studied theoretically using density functional calculations.
- Aman, Razia,Sadiq, Saima,Ali, Muhammad,Sadiq, Muhammad,Gul, Jehan,Saeed, Khalid,Khan, Adnan Ali,Shah, Sagheer Hussain
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p. 2947 - 2961
(2019/02/28)
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- Metal-Free Ring Opening Cyclization of Cyclopropane Carbaldehydes and N-Benzyl Anilines: An Eco-Friendly Access to Functionalized Benzo[b]azepine Derivatives
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Herein, we report a p-toluenesulfonic acid (PTSA) initiated mild and user-friendly ring opening/domino ring opening cyclization reaction (depends on substituent present in N-benzyl aniline) of cyclopropane carbaldehyde and N-benzyl aniline towards the formation of substituted 4-amino butanal/2,3-dihydro-1H-benzo[b]azepine. The product dihydro-1H-benzo[b]azepine was also converted into the corresponding tetrahydro-1H-benzo[b]azepine. (Figure presented.).
- Dey, Raghunath,Banerjee, Prabal
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supporting information
p. 2849 - 2854
(2019/04/26)
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- Synthesis of Imines via Reactions of Benzyl Alcohol with Amines Using Half-Sandwich (η6-p-cymene) Ruthenium(II) Complexes Stabilised by 2-aminofluorene Derivatives
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A new class of half-sandwich (η6-p-cymene) ruthenium(II) complexes supported by 2-aminofluorene derivatives [Ru(η6-p-cymene)(Cl)(L)] (L?=?2-(((9H-fluoren-2-yl)imino)methyl)phenol (L1), 2-(((9H-fluoren-2-yl)imino)methyl)-3-methoxyphenol (L2), 1-(((9H-fluoren-2-yl)imino)methyl)naphthalene-2-ol (L3) and N-((1H-pyrrol-2-yl)methylene)-9H-fluorene-2-amine (L4)) were synthesized. All compounds were fully characterized by analytical and spectroscopic techniques (IR, UV–Vis, NMR) and also by mass spectrometry. The solid state molecular structures of the complexes [Ru(η6-p-cymene)(Cl)(L2)], [Ru(η6-p-cymene)(Cl)(L3)] and [Ru(η6-p-cymene)(Cl)(L4)] revealed that the 2-aminofluorene and p-cymene moieties coordinate to ruthenium(II) in a three-legged piano-stool geometry. The synthesized complexes were used as catalysts for the dehydrogenative coupling of benzyl alcohol with a range of amines (aliphatic, aromatic and heterocyclic). The reactions were carried out under thermal heating, ultrasound and microwave assistance, using solvent or solvent free conditions, and the catalytic performance was optimized regarding the solvent, the type of base, the catalyst loading and the temperature. Moderately high to very high isolated yields were obtained using [Ru(η6-p-cymene)(Cl)(L4)] at 1?mol%. In general, microwave irradiation produced better yields than the other two techniques irrespective of the nature of the substituents.
- Vinoth, Govindasamy,Indira, Sekar,Bharathi, Madheswaran,Durgadevi, Anandhan,Abinaya, Ravikumar,Alves, Luis G.,Martins, Ana Margarida,Bharathi, Kuppannan Shanmuga
-
-
- Formic acid catalyzed one-pot synthesis of α-aminophosphonates: an efficient, inexpensive and environmental friendly organocatalyst
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Abstract: Aqueous formic acid is used for the synthesis of α-aminophosphonates through Kabachnik–Fields reaction applying aromatic amine, phosphite, and carbonyl compounds. Using formic acid as an efficient and low-cost organocatalyst provides environmental friendly, high yields, low reaction time and mild reaction condition. The isolated products were analyzed by IR, NMR, and mass techniques. Graphical abstract: [Figure not available: see fulltext.].
- Azarnia Mehraban, Jamshid,Jalali, Mahsa Sadat,Heydari, Akbar
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p. 2215 - 2223
(2018/08/04)
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- PdAu@MIL-100(Fe) cooperatively catalyze tandem reactions between amines and alcohols for efficient N-alkyl amines syntheses under visible light
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PdAu@MIL-100(Fe), with PdAu alloy nanoparticles of ca. 1.7 nm encapsulated inside MIL-100(Fe) cavities, were prepared via a double-solvent impregnation followed by photoreduction. As compared with bare Pd@MIL-100(Fe), bimetallic PdAu@MIL-100(Fe) showed superior activities for the tandem reactions between amines and alcohols to produce N-alkyl amines under visible-light irradiation, ascribed to the promoting effect of metallic Au in the photocatalytic alcohol-to-aldehyde dehydrogenation. A Pd/Au ratio dependent N-alkylation activity was observed over PdAu@MIL-100(Fe), implying the possibility of synchronizing the reaction rates of two consecutive steps in the N-alkylation reaction, i.e., photocatalytic alcohol-to-aldehyde dehydrogenation and imines hydrogenation, to optimize the whole reaction. This study provides a highly efficient and stable catalytic system for the realization of alkylation of amines via a successful coupling of MOF-based photocatalysis and metal nanoparticle-based hydrogenation. This work also demonstrates that the reaction rates of different catalytic steps in a cascade/tandem reaction can be synchronized for an efficient overall reaction via a rational design of the multifunctional catalysts.
- Wang, Dengke,Pan, Yating,Xu, Lizhi,Li, Zhaohui
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p. 248 - 254
(2018/04/02)
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- CO2-Catalyzed Efficient Dehydrogenation of Amines with Detailed Mechanistic and Kinetic Studies
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CO2-catalyzed dehydrogenation of amines has been achieved under photocatalytic conditions. With this concept, various amines have been selectively dehydrogenated to the corresponding imines in the presence of different functional groups such as nitrile, nitro, ester, halogen, ether, thioether, and carbonyl or carboxylic acid moieties. At the end, the CO2-catalyzed synthesis of pharmaceutical drugs has been achieved. The CO2 radical has been detected by EPR spectroscopy using DMPO, and the mechanism of this reaction is proposed on the basis of DFT calculations and experimental evidence.
- Riemer, Daniel,Schilling, Waldemar,Goetz, Anne,Zhang, Yu,Gehrke, Sascha,Tkach, Igor,Hollóczki, Oldamur,Das, Shoubhik
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p. 11679 - 11687
(2018/11/23)
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- Photochemically Promoted Aza-Diels-Alder-Type Reaction: High Catalytic Activity of the Cr(III)/Bipyridine Complex Enhanced by Visible Light Irradiation
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Aza-Diels-Alder-type cycloaddition reactions between a range of N-arylimines and functionalized alkenes were effectively catalyzed by the Cr(III)/bipyridine complex under irradiation of blue light, to give the corresponding 1,2,3,4-tetrahydroquinoline derivatives in high yields with excellent diastereoselectivity. Typically, the reaction of benzylideneaniline with 1-vinyl-2-pyrrolidinone proceeded smoothly with a substrate-to-catalyst molar ratio (S/C) of 1000 and completed within 4 h at room temperature (20-25 °C), affording the cycloaddition product in 97% yield.
- Arai, Noriyoshi,Ohkuma, Takeshi
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p. 7628 - 7636
(2017/07/26)
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- Preparation method for imine compounds
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The invention relates to a preparation method for imine compounds. The preparation method comprises the following concrete steps: with toluene or derivatives thereof and aminated compounds as reaction substrates, adding an oxygen source under the action of a catalyst; putting the above-mentioned substances into a pressure container, enclosing the pressure container and carrying out a stirring reaction at 50 to 150 DEG C for 6 to 24 h; and carrying out oxidative condensation so as to prepare the imine compounds. The method is characterized in that a metal oxide is used as the catalyst. According to the method, raw materials are cheap and easily available; the prepared imine compounds are easily separable from the catalyst; the catalyst can be cyclically used; reaction process is simple, controllable and easy to operate; and the yield of the imine compounds is as high as 90%.
- -
-
Paragraph 0076; 0077
(2017/10/25)
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- Dual Heterogeneous Catalyst Pd-Au@Mn(II)-MOF for One-Pot Tandem Synthesis of Imines from Alcohols and Amines
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A new Mn(II) metal-organic framework (MOF) 1 was synthesized by the combination of 4,4,4-trifluoro-1-(4-(pyridin-4-yl)phenyl)butane-1,3-dione (L) and Mn(OAc)2 in solution. 1 features a threefold-interpenetrating NbO net containing honeycomb-like channels, in which the opposite Mn(II)···Mn(II) distance is 23.5075(10) ?. Furthermore, 1 can be an ideal platform to support Pd-Au bimetallic alloy nanoparticles to generate a composite catalytic system of Pd-Au@Mn(II)-MOF (2). 2 can be a highly active bifunctional heterogeneous catalyst for the one-pot tandem synthesis of imines from benzyl alcohols and anilines and from benzyl alcohols and benzylamines.
- Chen, Gong-Jun,Ma, Hui-Chao,Xin, Wen-Ling,Li, Xiao-Bo,Jin, Fa-Zheng,Wang, Jing-Si,Liu, Ming-Yang,Dong, Yu-Bin
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p. 654 - 660
(2017/01/13)
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- A novel straightforward synthesis of α-aminophosphonates: one-pot three-component condensation of alcohols, amines, and diethylphosphite in the presence of CuO@Fe3O4 nanoparticles as a catalyst
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We report here a novel and straightforward synthesis method for the preparation of α-aminophosphonates in relatively good yield. The method involves the one-pot three-component condensation of alcohols, amines, and diethylphosphite in the presence of CuO@Fe3O4 nanoparticles as a recyclable catalyst. CuO@Fe3O4 nanoparticles were prepared and their structures were confirmed by the FT-IR, TGA, VSM, TEM and X-ray diffraction patterns analyses.
- Kaboudin, Babak,Kazemi, Foad,Hosseini, Narges Kadkhoda
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p. 4475 - 4486
(2017/07/22)
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- Reaction of nitroanilines with aldehydes. Refinement of the Doebner–Miller reaction mechanism
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Due to intramolecular hydrogen bonding between the amino and nitro groups, o-nitroaniline is incapable of forming Schiff bases in the reactions with acetaldehyde and crotonaldehyde but is converted to quinoline derivative under Doebner–Miller reaction conditions via addition to the C=C double bond of the α,β-unsaturated aldehyde. Under analogous conditions, p-nitroaniline possessing a free amino group gives rise to the product of Doebner–Miller quinoline synthesis through intermediate formation of Schiff base dimer. The reaction of p-nitroaniline with benzaldehyde also yields the corresponding Schiff base, whereas o-nitroaniline is converted to N-benzyl derivative.
- Denisov, V. Ya.,Grishchenkova,Tkachenko,Luzgarev
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p. 1797 - 1803
(2017/02/19)
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- Reactivity of Me-pma RhI and IrI Complexes upon Deprotonation and Their Application in Catalytic Carbene Carbonylation Reactions
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Dehydrogenative oxidation of amines is a relevant process in metal-mediated catalysis, with the amines being either substrates or ligands. Transformation of amine- into imine-type ligands in the coordination sphere of a transition metal can be an important catalyst activation process. The behaviour of secondary pyridin-2-ylmethanamine (pma) ligands in the corresponding rhodium and iridium complexes upon NH deprotonation varies, depending on a number of factors. In this paper the behaviour of the Me-pma ligand [Me-pma = N-methyl-1-(pyridin-2-yl)methanamine] bound to [Rh(cod)]+ and [Ir(cod)]+ was studied. Whereas the iridium amido complex could be obtained upon NH deprotonation, the rhodium complex instantaneously disproportionated into a free pma ligand and an unusual dinuclear complex, adopting a structure with two RhI metal centres hosted by a dianionic (pma-2H)2- ligand, and with the ligand coordinating to Rh2 as an "aza-allyl" fragment. The study gives further proof for the effect of pyridine ligation on the previously observed charge-transfer from the ligand to the metal. Furthermore, the catalytic activity of both the Ir and the Rh species with Me-pma in carbene carbonylation reactions to generate ketenes was studied.
- Tang, Zhou,Tejel, Cristina,Martinez De Sarasa Buchaca, Marc,Lutz, Martin,Van Der Vlugt, Jarl Ivar,De Bruin, Bas
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p. 963 - 974
(2016/03/15)
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- Coupling MOF-based photocatalysis with Pd catalysis over Pd@MIL-100(Fe) for efficient N-alkylation of amines with alcohols under visible light
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Pd nanoparticles with an average size of 1.7 nm confined inside a MIL-100(Fe) cavity (Pd@MIL-100(Fe)) were prepared via double-solvent impregnation combined with a photoreduction process. Due to efficient coupling of photocatalytic dehydrogenation and Pd-based hydrogenation, the resultant Pd@MIL-100(Fe) showed significantly superior performance in light-induced N-alkylation of amines with alcohols over Pd/MIL-100(Fe), in which larger Pd nanoparticles (6–12 nm) deposited on the external surface of MIL-100(Fe) were prepared via a conventional single-solvent impregnation followed by a similar photoreduction process. Kinetic studies and controlled experiments revealed that the whole N-alkylation reaction is limited by the photocatalytic alcohol-to-aldehyde dehydrogenation reaction. This is the first demonstration of light-induced N-alkylation of amines by alcohols over M/MOFs nanocomposites and also highlights the great potential of using M/MOFs nanocomposites as multifunctional catalysts for light-induced organic syntheses.
- Wang, Dengke,Li, Zhaohui
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p. 151 - 157
(2018/03/29)
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- Metal-free reductive amination of aldehydes for the synthesis of secondary and tertiary amines
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Reductive amination of aldehydes to produce secondary amines at room-temperature by in situ generated benzimidazoline is discussed. The bonus of the reaction is the formation of pharmaceutically important benzimidazole as a by-product in good yield, which can be recovered from the reaction mixture by simple filtration. The product, secondary amine, is transformed to tertiary amine in the same pot.
- Ambica,Khajuria, Rajni,Saini, Yeshwinder,Kapoor, Kamal K
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p. 1252 - 1259
(2015/11/25)
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- Oxidation of aromatic anils in aniline moiety by meta-chloroperbenzoic acid in aqueous acitic medium
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The kinetics of oxidation of aromatic anils in aniline moiety by meta-chloroperbenzoic acid (m-CPBA) has been studied in aqueous acitic medium. The order of reaction was found to be second order with respect to aromatic anil and first order with respect to m-chloroperbenzoic acid. The increase of [H+] in this oxidation retards the rate of reaction. The effects of substituents on the oxidation rate were studied with 3 meta- and 5 para-substituted anils at five different temperatures. Thermodynamic parameters for the oxidation have been determined and discussed. meta-Chloroperbenzoic acid oxidation with substituted anils fulfills the isokinetic relationship and Exner relationship but not to any of the linear free energy relationships. The deviation of Hammett plot was noted and a concave downward curve was obtained for the anils with substituents in aniline moiety.
- Venkatesh,Karunakaran
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p. 2851 - 2855
(2015/12/12)
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- Recyclable hydrotalcite catalysts for alcohol imination via acceptorless dehydrogenation
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Here we report that hydrotalcite-like materials (HTs) are active heterogeneous catalysts for alcohol imination, which proceeds through acceptorless alcohol dehydrogenation. The catalytic activity of a series of Mg-Al hydrotalcites doped with Fe3+, Zn2+, Ni2+, Cr3+ and Cu2+ is dependent on their composition, and Fe : Mg : Al HT yields up to 92% imine under mild conditions. Impregnation of Fe : Mg : Al HT with Pd0 resulted in an enhancement of activity for acceptorless dehydrogenation, but a decrease in the isolated yield of imine in a loading-dependent manner. This is attributed to the Pd loading-dependent retention of imine and aldehyde on the catalysts. The substrate scope for alcohol imination and recyclability of the catalysts is discussed.
- Bain, John,Cho, Philip,Voutchkova-Kostal, Adelina
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p. 2271 - 2280
(2015/04/22)
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- Synthesis of anti-2,3-dihydro-1,2,3-trisubstituted-1H-naphth [1,2-e][1,3]oxazine derivatives via multicomponent approach
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A series of anti-2,3-dihydro-1,2,3-trisubstituted-1H-naphth [1,2-e][1,3]oxazine derivatives 6 were exclusively obtained in high yields for the first time through multicomponent reactions (MCRs) of 2-naphthol, aromatic aldehydes and electron rich primary amines in ethanol at room temperature using CCl3COOH as catalyst. The same reaction could be conducted effectively in solvent-free medium at 100 °C. The stereochemistry of the two hydrogens connected to C-2 and C-4 (1,3) positions of the oxazine ring are identified as anti-orientation by single crystal XRD, COSY and NOESY analysis.
- Borah, Ruli,Dutta, Arup Kumar,Sarma, Parishmita,Dutta, Champak,Sarma, Bipul
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p. 10912 - 10917
(2014/03/21)
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- Silver-catalyzed alkyne activation: The surprising ligand effect
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An unexpected ligand effect was discovered in the silver(I)-catalyzed alkyne activation. For both aldehyde-alkyne-amine (A3) condensation and intermolecular alkyne hydroamination, the type B complex (P:Ag=1:1) effectively promoted the reaction, while no reaction occurred with either no ligand or excess ligands under the identical conditions.
- Su, Yijin,Lu, Mei,Dong, Boliang,Chen, Hao,Shi, Xiaodong
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supporting information
p. 692 - 696
(2014/04/03)
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- Oxidation of aromatic anils by sodium perborate in aqueous acetic Acid Medium
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The kinetics of oxidation of 9 meta- and 15 para- substituted aromatic anils by sodium perborate were investigated in aqueous acetic acid medium. The reaction was second order with respect to aromatic anil and first order with respect to the sodium perborate. The increase of [H+] in this oxidation retards the rate of the reaction. The observed rate constant for the substituents were plotted against the Hammett constant, δ and a non-linear concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus δwas attributed to the transition state whereas the non-linear concave upward curve was observed for the substituents in the benzaldehyde moiety and a non-linear concave upward curve was observed for the substituents in the combination of aniline and benzaldehyde moiety. The electron withdrawing substituents fall on one side of the curve, having a negative ρvalue and the electron releasing substituents fall on the other side, with a positive ρvalue and a suitable mechanism was proposed.
- Venkatesh,Karunakaran
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p. 739 - 744
(2014/06/09)
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- One pot photoredox decarboxylation reaction of N-cyano(α-bromo- α-phenyl)methylanilines leading to synthesis of four-membered cyclic carbamates
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A new four-membered cyclic carbamates have been synthesized through solar irradiation of N-cyano(α-bromo-α-phenyl)methylanilines in their aqueous methanolic solution using iodide salt in basic medium. These compounds have been characterized as 3,4-diphenyl-1,3oxazetidin-2-one through their elemental analysis, IR, 1H-NMR, 13C-NMR, and mass spectral studies.
- Kaur, Manpreet,Singh, Baldev
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p. 850 - 853
(2014/06/10)
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- Solvent free acid catalysed direct N-alkylation of amines with alcohols using Al grafted MCM-41
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The catalytic activity of Al grafted MCM-41 (Al-MS) was explored for solvent free acid catalysed direct N-alkylation of amines using alcohols as green alkylating agent to establish a clean method for synthesis of N-alkylated amines. The study revealed that acidity of Al-MS catalyst, reaction conditions and substrate's (amines and alcohols) nature are important factors influencing the N-alkylation reaction. The Al grafted MCM-41 with Si/Al molar ratio of 5 showed excellent activity for N-alkylation of amines with alcohols. The reusability of spent catalyst regenerated by simple washing with acetone was demonstrated for subsequent four reaction cycles.
- Tayade, Kamlesh N.,Mishra, Manish,Munusamy,Somani, Rajesh S.
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- Synthesis of 1,6-dihydropyrimidines via copper-catalyzed multistep cascade reactions between O-propargylic aldoximes and isocyanates
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Multi-step cascade reactions of O-propargylic oximes with isocyanates were carried out in the presence of copper catalysts to afford the corresponding 1,6-dihydropyrimidines in good yields. The multi-step reactions consisted of a 2,3-rearrangement, a [3+2] cycloaddition, decarboxylative ring opening involving a 1,4-hydrogen shift, and a 6π-electrocyclization.
- Nakamura, Itaru,Onuma, Toshiki,Zhang, Dong,Terada, Masahiro
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p. 1178 - 1182
(2014/02/14)
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- Catalytic activity of MCM-41 and Al grafted MCM-41 for oxidative self and cross coupling of amines
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The catalytic activity of MCM-41 mesoporous silica (MS) and Al grafted MCM-41 (Al-MS) with varied amount of Al were studied for oxidative self and cross coupling of benzyl amines to imines. The role of Al, its amount, acidity of the catalyst, effect of reaction conditions (especially presence of solvent and excess air) and amines nature on the oxidative coupling reactions were investigated. Surface OH groups play an effective role in amine activation by hydrogen bonding, whereas the acid sites generated by incorporation of optimum amount of Al further improve the activity. The Al in optimum amount (Si/Al: 20) showed good catalytic activity in self coupling of benzyl amine as compared to MS and Al-MS with high Al loading. A suitable polar solvent and presence of excess air significantly promote the activity of MS and Al-MS for amine coupling reactions. The MS without Al was also found to be efficient catalyst for oxidative self and cross coupling of amines. The presence of Al in Al-MS (in optimum amount, i.e., Si/Al: 20) made the self coupling of benzyl amine faster than MS, whereas the cross coupling reactions with Al-MS were observed to be slightly slower than MS, which is probably due to competitive adsorption of amine substrate and amine nucleophile over acidic sites. The activity of MS and Al-MS catalysts for self and cross coupling reactions was also dependent of the amines nature (basicity and nucleophilicity).
- Tayade, Kamlesh N.,Mishra, Manish
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p. 114 - 125
(2014/01/06)
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- Selective aerobic oxidation of alcohols to aldehydes, carboxylic acids, and imines catalyzed by a Ag-NHC complex
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Silver NHC catalysts have been developed for the selective oxidation of alcohols to aldehydes or carboxylic acids in the presence of BnMe3NOH or KOH under dry air. The aerobic oxidation conditions are mild, and the yield is excellent. Further tandem catalysis enables the one-pot synthesis of imines in excellent yield. Only 0.1 mol % of the catalyst is required.
- Han, Lei,Xing, Ping,Jiang, Biao
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supporting information
p. 3428 - 3431
(2014/07/21)
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- Dehydrogenation and oxidative coupling of alcohol and amines catalyzed by organosilicon-supported TiO2@PMHSIPN
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The catalytic dehydrogenation and tandem transformation of aromatic alcohols, including oxidative coupling of alcohols and amines, were achieved successfully using a catalytic amount of organosilicon-supported titania (TiO2@PMHSIPN), which enables the efficient synthesis of aromatic aldehydes, imines, and benzimidazoles in good to excellent yields. This journal is the Partner Organisations 2014.
- Wang, Hu,Zhang, Jin,Cui, Yu-Ming,Yang, Ke-Fang,Zheng, Zhan-Jiang,Xu, Li-Wen
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p. 34681 - 34686
(2014/11/08)
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- Grinding synthesis of schiff bases combined with infrared irradiation
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Solid-phase synthesis combined with infrared irradiation promoted the formation of a series of Schiff bases in the condensation reaction between substituted benzaldehydes and anilines, in the solvent free. Benzaldehydes and anilines, containing either electron withdrawing or electron-releasing groups, were evaluated their substituent effect on the formation of the Schiff bases. Moreover, this new procedure is environmentally benign because no solvent was employed in the transformations.
- Tong, Jian-Ying,Sun, Na-Bo,Wu, Hong-Ke
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p. 5399 - 5401
(2013/07/26)
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- Green oxidative synthesis of primary amides from primary alcohols or aldehydes catalyzed by a cryptomelane-type manganese oxide-based octahedral molecular sieve, OMS-2
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In this study, a new green synthetic route to primary amides, that is, aerobic oxidative amidation of primary alcohols or aldehydes with ammonia, has been developed. In the presence of a cryptomelane-type manganese oxide-based octahedral molecular sieve (OMS-2), various kinds of structurally diverse primary alcohols or aldehydes including aromatic, olefinic, heteroaromatic, and aliphatic ones can be converted into the corresponding primary amides in moderate to high yields (20 examples from primary alcohols and 11 examples from aldehydes). Furthermore, gram-scale amidation is also effective, and the analytically pure primary amides can easily be isolated. The present catalysis by OMS-2 is truly heterogeneous in nature, and the retrieved OMS-2 catalyst can be reused several times (at least 12 times for the amidation of 2-pyridinemethanol). Though the formation rates of the corresponding primary amide are gradually decreased by repeating reuse experiments, OMS-2 can be regenerated by calcination. The present OMS-2-catalyzed amidation of primary alcohols is composed of four relay steps: (i) oxidative dehydrogenation of primary alcohols, (ii) dehydrative condensation of aldehydes with ammonia, (iii) oxidative dehydrogenation of aldimines, and (iv) hydration of nitriles to form the corresponding primary amides. All steps (i)-(iv) can be promoted by the presence of OMS-2. The Royal Society of Chemistry 2013.
- Yamaguchi, Kazuya,Kobayashi, Hiroaki,Wang, Ye,Oishi, Takamichi,Ogasawara, Yoshiyuki,Mizuno, Noritaka
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p. 318 - 327
(2013/03/14)
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- Tetrahydroquinolines and benzazepines through catalytic diastereoselective formal [4 + 2]-cycloaddition reactions between donor-acceptor cyclopropenes and imines
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Regio- and diastereoselective Lewis acid catalyzed cycloaddition reactions between imines and donor-acceptor cyclopropenes generated from silyl-protected enoldiazoacetates provide direct access to stable cyclopropane-fused tetrahydroquinolines and, with cyclopropane ring opening under mild conditions, to 1H-benzazipine derivatives.
- Truong, Phong M.,Mandler, Michael D.,Zavalij, Peter Y.,Doyle, Michael P.
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supporting information
p. 3278 - 3281
(2013/07/26)
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- Kinetic investigation of oxidation of aromatic anils by potassium peroxymonosulfate in aqueous acidic medium
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The kinetics of oxidation of aromatic anils to benzaldehyde and azobenzene by potassium peroxymonosulfate has been studied in aqueous acetic acid medium. The low dielectric constant of the medium facilitates the reactivity. It has been found that the variation in the ionic strength of the reaction has a negligible effect on the rate. Similarly, polymerization was not observed when acrylonitrile was added to the reaction mixture. This observation rules out the formation of any free radical in the reaction. The added Mn(II) increases the rate of the reaction, which indicates the involvement of two-electron transfer. Highly negative ΔS# values indicate a structured transition state. The deviation of the Hammett plot was noted, and a concave downward curve was obtained for the anils with substituents in the aniline moiety. The observed break in the log kobs versus σ is attributed to the transition state whereas the concave upward curve was observed for the substituents in the benzaldehyde moiety and in the combination of aniline and benzaldehyde moieties, and a suitable mechanism was proposed.
- Venkatesh,Karunakaran
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p. 542 - 550
(2013/07/26)
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- Highly efficient iron phthalocyanine catalyzed oxidative synthesis of imines from alcohols and amines
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An efficient iron phthalocyanine catalyzed method was developed for direct oxidative coupling of alcohols with amines to afford corresponding imines. The present protocol is applicable to various substituted aromatic and aliphatic alcohols and amines. The reaction is believed to proceed via activation of alcohols by iron phthalocyanines through Lewis acid-base interaction to form aldehydes, which by nucleophilic attack of amines are converted into the corresponding imines.
- Bala, Manju,Verma, Praveen Kumar,Kumar, Neeraj,Sharma, Upendra,Singh, Bikram
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supporting information
p. 732 - 737
(2013/08/23)
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- Montmorillonite as a heterogeneous catalyst in the efficient, mild and one pot synthesis of Schiff bases under solvent-free conditions
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A mild and efficient method has been reported for preparation of Schiff base ligands through condensation reaction of various aromatic aldehydes and ketones with different aromatic amines in the presence of montmorillonite as a heterogeneous catalyst under solvent free conditions. The advantages of this friendly, economically, environmentally and mild method are such as; simplicity of the reaction procedure, reusability of catalyst, simple work-up, high product yields and very short reaction times.
- Naeimi, Hossein,Rabiei, Khadijeh
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experimental part
p. 208 - 212
(2012/07/03)
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- An efficient three-component synthesis of homoallylic amines catalysed by MgI2 etherate
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A three-component reaction of aldehydes, amines and allyltributylstannane was efficiently carried out to afford the corresponding homoallylic amine derivatives in the presence of 20 mol% of MgI2 etherate [(MgI 2?(OEt2)n] under mild and neutral reaction conditions in good to excellent yields.
- Wang, Yanping,Liu, Yingshuai,Hu, Shenghui,Zhang, Xingxian
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experimental part
p. 21 - 24
(2012/03/27)
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- Chiral phosphoric acid catalyzed inverse-electron-demand aza-Diels-Alder reaction of isoeugenol derivatives
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Highly enantio- and diastereoselective three-component inverse electron-demand aza-Diels-Alder reaction of aldehydes, anilines, and isoeugenol derivatives catalyzed by a chiral phosphoric acid catalyst are reported. A wide variety of 2,3,4-trisubstituted tetrahydroquinolines containing an aryl group at the 4-position were obtained in a one-pot process with good to high yields and excellent stereoselectivities (>95:5 dr and up to >99% ee).
- He, Long,Bekkaye, Mathieu,Retailleau, Pascal,Masson, Géraldine
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supporting information; experimental part
p. 3158 - 3161
(2012/08/07)
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- Copper(II) triflate-sodium dodecyl sulfate catalyzed preparation of 1,2-diphenyl-2,3-dihydro-4-pyridones in aqueous acidic medium
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The reactions between N-benzylideneanilines and Danishefsky's diene proceed smoothly in acidic aqueous medium in the presence of a catalytic amount of copper(II) triflate-sodium dodecyl sulfate [Cu(OTf)2-SDS] to afford the corresponding 1,2-diphenyl-2,3-dihydro-4-pyridones in excellent yields of 84-95%. The aqueous solution containing the catalyst is recovered and reused without any loss in efficiency. Georg Thieme Verlag Stuttgart New York.
- Lanari, Daniela,Piermatti, Oriana,Pizzo, Ferdinando,Vaccaro, Luigi
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experimental part
p. 2181 - 2184
(2012/09/22)
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- Oxidative imination of toluenes catalyzed by Pd-Au/silica gel under mild reaction conditions
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A Pd-Au/SiO2 catalyst was prepared for the oxidative imination of toluenes with up to 99% yields in the absence of dehydrating agents under mild conditions. Nanoparticles with a PdO layer and PdO-Au core may be the active structure for the reaction.
- Cui, Xinjiang,Shi, Feng,Deng, Youquan
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supporting information; experimental part
p. 7586 - 7588
(2012/10/07)
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- Reductive amination of carbonyl compounds over silica supported palladium exchanged molybdophosphoric acid catalysts
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Palladium exchanged molybdophosphoric acid supported on silica is reported as a highly effective catalyst for direct reductive amination of carbonyl compounds. The catalysts are characterized by X-ray diffraction and FT-infrared spectroscopy. The characterization results support the existence of Keggin ion of heteropoly molybdate on silica. The catalyst is facile, water tolerable and environmentally benign for reductive amination. A variety of secondary and tertiary amines can be synthesized over this catalyst in excellent yields under mild reaction conditions. A plausible reaction mechanism is proposed for the reductive amination of carbonyl compounds over this catalyst.
- Srivani,Prasad, P. S. Sai,Lingaiah
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experimental part
p. 389 - 396
(2012/06/18)
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- Chiral phosphoric acid-catalyzed enantioselective three-component Povarov reaction using enecarbamates as dienophiles: Highly diastereo- and enantioselective synthesis of substituted 4-aminotetrahydroquinolines
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A chiral phosphoric acid (5)-catalyzed three-component Povarov reaction of aldehydes 2, anilines 3, and enecarbamates 4 afforded cis-4-amino-2-aryl(alkyl)- 1,2,3,4-tetrahydroquinolines 1 in high yields with excellent diastereoselectivities (>95%) and almost complete enantioselectivities (up to >99% ee). The reaction was applicable to a wide range of anilines bearing electron-donating (OMe) and electron-withdrawing groups (e.g., Cl, CF 3, NO2) and allowed, for the first time, aliphatic aldehydes to be employed in the enantioselective Povarov reaction. With β-substituted acyclic enecarbamates, 2,3,4-trisubstituted 1,2,3,4-tetrahydroquinolines with three contiguous stereogenic centers were produced in excellent diastereo- and enantioselectivities (87 to >99% ee). A detailed study of the active catalytic species allowed us to reduce the catalyst loading from 10% to 0.5% with no deterioration of enantiomeric excess. In addition, mechanistic studies allowed us to conclude unequivocally that the Povarov reaction involving enecarbamate as dienophile proceeded via a stepwise mechanism. The key role of the free NH function of the enecarbamate in the success of this transformation was demonstrated. NMR experiments indicating the catalyst-substrate interaction as well as a linear correlation between catalyst and product ee's were also documented.
- Dagousset, Guillaume,Zhu, Jieping,Masson, Geraldine
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supporting information; experimental part
p. 14804 - 14813
(2011/11/04)
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- Catalytic intermolecular hetero-dehydro-diels-alder cycloadditions: Regioand diasteroselective synthesis of 5,6-dihydropyridin-2-ones
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A novel catalyzed intermolecular heterodehydro-Diels-Alder reaction between push-pull 1,3-dien-5-ynes and aldimines or silylaldimines is reported. The sequence is promoted both by gold(I) or silver(I) catalysts and leads to the diastereo- and regioselective formation of 5,6- dihydropyridin-2-ones.
- Fernandez-Garcia, Jesus Manuel,Fernandez-Rodriguez, Manuel A.,Aguilar, Enrique
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supporting information; experimental part
p. 5172 - 5175
(2011/12/04)
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- 2,3-dihydro-1,2-diphenyl-substituted 4H-pyridinone derivatives as new anti flaviviridae inhibitors
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With the aim of identifying novel lead compounds active against emergent human infectious diseases, a series of 2,3-dihydro-4H-pyridinone derivatives has been prepared and evaluated for antiviral activity. Compounds were evaluated in vitro in cell-based assays for cytotoxicity and against a wide spectrum of viruses. In the antiviral screening, several compounds showed to be fairly active against viruses belonging to the Flaviviridae family. The Pestiviruses (bovine viral diarrhoea virus) were inhibited by 4acis (CC50>100μm; EC50 = 14μm), compounds 4ccis and 6a showed a significant activity against Flaviviruses (Yellow Fever Virus) (CC50>100μm; EC50=18μm, CC50>100μm; EC50=10μm). Among these, compound 6a displayed great inhibitory activity against Hepaciviruses (hepatitis C virus) in replicon assay [CC50 > 100μm; EC50(1b)=4μm]. In vitro inhibitory activity against the HCV RNA-dependent RNA polymerase (NS5B) of title compounds is discussed. The antiviral screening of viral strains indicated that compound 6a can be selected as promising tool in novel anti-flaviviruses development.
- Peduto, Antonella,Massa, Antonio,Di Mola, Antonia,de Caprariis, Paolo,La Colla, Paolo,Loddo, Roberta,Altamura, Sergio,Maga, Giovanni,Filosa, Rosanna
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experimental part
p. 441 - 449
(2012/01/13)
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