- Degradation of lignin with aqueous ammonium-based ionic liquid solutions under milder conditions
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This study investigates the performance of two aqueous ionic liquids (ILs), dimethylbutylammonium acetate ([DMBA][Ac]) and dimethylbutylammonium butanoate ([DMBA][B]), solutions for depolymerizing alkali lignin into valuable phenolic compounds. The favorable operation conditions, including reaction temperature and reaction time, are explored. The extent of depolymerization of the lignin is evaluated by analysis with gel permeation chromatography (GPC). The results show that the average molecular weights of the depolymerized lignin samples can be reduced by as high as 93.8% and 86.8% after treating with the aqueous [DMBA][Ac] and [DMBA][B], respectively. Moreover, the aromatic chemical species in the depolymerized solutions are identified by using gas chromatography?mass spectrophotometry (GC-MS). The confirmation of the chemical species is further made by using a series of spectroscopic techniques, such as FT-IR, and 1H NMR and 13C NMR spectroscopy. Promising results have been achieved for the depolymerization of the lignin into valuable chemicals by using the proposed green media, aqueous solutions of ionic liquids [DMBA][Ac] and [DMBA][B], under milder conditions.
- Gupta, Bhupender S.,Lee, Ming-Jer,Tolesa, Leta Deressa
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- The impact of Novel Process Windows on the Claisen rearrangement
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The impact of Novel Process Windows on the Claisen rearrangement in microflow was investigated. Elevated temperatures (up to 300 °C) were crucial to achieve full conversion of allyl phenyl ether in the Claisen rearrangement. We observed that 1-butanol was the optimal reaction solvent for this transformation in flow. Solvent-free reaction conditions were feasible for the Claisen rearrangement and provided quantitative yields of the target product at 280 °C and 100 bar. Also elevated reaction pressures (up to 300 bar) were investigated in the Claisen rearrangement. We found that thermal expansion and pressure-related compression phenomena cannot be ignored at such harsh reaction conditions. These phenomena lead to large deviations of the desired residence time (as calculated from the nominal flow rate) and have a clear impact on the observed reaction trends. Finally, we also investigated the temperature effect on the Johnson-Claisen rearrangement of cinnamyl alcohol. Quantitative yields were obtained at 200 °C and at 100 bar.
- Kobayashi, Hiroki,Driessen, Brian,Van Osch, Dannie J.G.P.,Talla, Ali,Ookawara, Shinichi,No?l, Timothy,Hessel, Volker
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- A flow reactor with inline analytics: Design and implementation
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A continuous flow system complete with inline analytics is described. Sampling from a high pressure reactor and automated delivery mechanisms are detailed. The ability of the system to maintain critical process parameters (CPP) throughout a reaction process is demonstrated. Setup performance was evaluated using the Claisen rearrangement of allyl phenyl ether (1).
- Somerville, Kristina,Tilley, Michael,Li, Guanlong,Mallik, Debasis,Organ, Michael G.
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- Water-Accelerated Tandem Claisen Rearrangement-Catalytic Asymmetric Carboalumination
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matrix presented The addition of stoichiometric quantities of water accelerates both the trimethylaluminum-mediated aromatic Claisen reaction and the chiral zirconocene-catalyzed asymmetric carboalumination of terminal alkenes. The two reactions occur in a tandem sequence resulting in the selective formation of two new C-C and one C-O bond after oxidative quench of the intermediate trialkylalane.
- Wipf, Peter,Ribe, Seth
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- A continuous-flow microwave reactor for conducting high-temperature and high-pressure chemical reactions
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A continuous-flow microwave reactor with a unique pressure control device is described. The reactor has been designed to withstand extremely high pressure without the involvement of a conventional backpressure-creating device that commonly results in carryover and cross-contamination problems. The reactor efficiency has been evaluated by product conversions using two model reactions, namely, the Claisen rearrangement and the synthesis of benzimidazole.
- Sauks, Jennifer M.,Mallik, Debasis,Lawryshyn, Yuri,Bender, Timothy,Organ, Michael
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- Vibrational Activation. 2.1 Acceleration of Bond-Making Reactions by Solvent Viscosity as a Model for Enzymic Catalysis. The Claisen Rearrangement and the Diels-Alder Reaction
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The vibrational activation theory holds that enzymes catalyze reactions in part by simply immobilizing the reactants.Typical bond-making reactions should then go faster at high viscosities.This prediction has now been verified for two different reactions.At 138 deg C the Claisen rearrangement of phenyl allyl ether goes at relative rates of 1.00, 0.98, 1.13, and 1.36 in n-octane, isooctane, n-octacosane, and Nujol, whose relative viscosities at 100 deg C are 1.00, 0.94, 4.92, and 11.8, respectively.The relationship is linear with slope 0.041.Addition of polyethylene to the Nujol raises the relative viscosity to 48.5 and the relative rate to 1.70.The intramolecular Diels-Alder cyclization of N-propargyl-9-anthroamide at 100 deg C goes at relative rates 1.00, 1.16, 1.25, and 1.38 in mono-, di-, tri- and tetraglyme, whose relative viscosities at 100 deg C are 1.00, 1.28, 1.54, and 1.99, respectively.The relationship is again linear, with slope 0.37.In addition, the following examples from the literature are analyzed in terms of viscosity-induced accelerations: the dimerization of cyclopentadiene, pressure-accelerated reactions where /-ΔV(excit.)/ > /-ΔV/ and liquid/gas rate ratios are > 1.A test of the theory that the liquid/gas phenomenon stems from hyperpolarizability of the transition state was made by measuring Claisen relative rates in five solvents of widely varying refractive indices.No relationship between rate and solvent polarizability was found.
- Firestone, Raymond A.,Vitale, Mark A.
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- Highly-selective and high-speed Claisen rearrangement induced with subcritical water microreaction in the absence of catalyst
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Highly-selective, high-speed aromatic and aliphatic Claisen rearrangement was shown to give the corresponding product in an excellent yield induced by subcritical water microreaction in the absence of catalyst.
- Sato, Masahiro,Otabe, Nobuhiro,Tuji, Tomoya,Matsushima, Keiichiro,Kawanami, Hajime,Chatterjee, Maya,Yokoyama, Toshiro,Ikushima, Yutaka,Suzuki, Toshishige Maro
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- The ene reaction between maleimides and allyl-substituted aromatics
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The products from the 'ene' reaction between allyl-substituted aromatics and maleic anhydride, maleimide, N-phenylmaleimide and N-(4-phenoxyphenyl)maleimide have been isolated and characterised, and a semi-quantitative assessment of ene and enophile reactivities has been made. The reaction between N-phenylmaleimide and allylaromatics bearing a 1,3,5-triazine substituent has been investigated as a model for a proposed cyanate ester-bis-maleimide-allyl cyanate ester ter-polymerisation.
- Cunningham, Ian D.,Brownhill, Andrew,Hamerton, Ian,Howlin, Brendan J.
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- Heteropoly acid encapsulated SBA-15/TiO2 nanocomposites and their unusual performance in acid-catalysed organic transformations
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The preparation of SBA-15/ TiO2 nanocomposites with different loadings of Keggin-type 12-tungstophosphoric acid (TPA) nanocrystals in their mesochannels through a simple and effective vacuum impregnation method is reported for the first time. The catalysts have been characterised by various sophisticated techniques, including XRD, HRSEM, and TEM. It has been found that the acidity and the textural parameters of the nanocomposites can be controlled by simply changing the loadings of TPA and TiO2 or the calcination temperature. TPA and TiO2 loadings of 15 and 22.4 wt%, respectively, and a calcination temperature of 1123 K have proved to be optimal for obtaining mesoporous nanocomposite materials with the highest acidity. Moreover, the activities of these catalysts in promoting hydroamination as well as Mannich and Claisen rearrangement reactions have been extensively investigated. The results show that the amount of TPA has a great influence on the activity of the nanocomposites in all of the reactions studied. The effects of other reaction parameters, such as temperature and reaction time, on the conversion and product selectivity have also been studied in detail. A kinetic analysis of the formation of the products under various reaction conditions is presented. It has been found that the activity of the nanocomposite composed of 15wt% TPA deposited on 22.4 wt of TiO2 on SBA-15 in promoting the studied reaction is remarkably higher than the catalytic activities shown by pure TPA, TiO2-loaded SBA-15, or TPA-loaded SBA-15. The results obtained have indicated that the acidity and the structural control of the nanocomposite materials are highly critical for obtaining excellent catalytic activity, and the presented highly acidic nanocomposites are considered to show great potential for use as catalysts in promoting many acid-catalysed organic transformations.
- Sawant, Dhanashri P.,Justus, Josena,Balasubramanian, Veerappan V.,Ariga, Katsuhiko,Srinivasu, Pavuluri,Velmathi, Sivan,Halligudi, Shivappa B.,Vinu, Ajayan
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- Photochemical electron transfer across a liquid/liquid interface: Methylene Blue-sensitized decarboxylation of substituted carboxylic acids
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Methylene Blue photocatalyzed electron transfer reactions of some substituted carboxylic acids across the water/benzene interface lead to efficient decarboxylation of these acids and the utility of this procedure has been demonstrated by the synthesis of some dihydrobenzopyran and dihydrobenzofuran derivatives.
- Das, Suresh,Thanulingam,Rajesh,George
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- Non-thermal reaction triggered by a stimulated Raman process using 5-fs laser pulses in the electronic ground state: Claisen rearrangement of allyl phenyl ether
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The vibrational populations of allyl phenyl ether were excited by a broadband visible 5-fs laser pulse by the stimulated Raman process to promote a 'non-thermal' Claisen rearrangement reaction in the electronic ground state. Analyses of the time-resolved vibrational spectra observed in the subpicosecond region has shown that the Claisen rearrangement proceeds in the following three-step pathway: (1) weakening of the C3O bond to generate a bis-allyl intermediate, (2) formation of the weak C1C5 bond results in the generation of a six-membered structure, and (3) simultaneous processes of C3O breaking and C1C5 formation leading to the generation of a keto-intermediate.
- Iwakura, Izumi,Yabushita, Atsushi,Kobayashi, Takayoshi
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- Structure effect of imidazolium-based dicationic ionic liquids on claisen rearrangement
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A large group of imidazolium-based dicationic ionic liquids (DILs) has been prepared in good yields. Thermal stability of all DILs has been determined. The effects of the reaction time, cation, imidazolium C2-H acidity, and anion on the Claisen rearrangement of allyl phenyl ether have been investigated. Type of anion and the presence of the acidic C2-H bond in the imidazolium moieties have proven to be essential for this reaction. The simple procedure and the possibility of avoiding the use catalysts and volatile organic solvents make this synthetic method environmentally benign and adaptable for large-scale applications.
- Priede, Elina,Nakurte, Ilva,Zicmanis, Andris
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- Generation of cyclopropanediazonium and its chemical transformations in the presence of phenol
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The reaction of phenol with cyclopropanediazonium ion generated in situ from N-cyclopropyl-N-nitrosourea by the action of K2CO3 or Cs2CO3 was studied. The main reaction pathway is diazo coupling of cyclopropanediazonium with phenol to give 4-(cyclopropyldiazenyl) phenol, and only traces of isomeric 2-(cyclopropyldiazenyl)phenol were formed. The reaction was accompanied by partial denitrogenation of the diazonium ion with formation of cyclopropyl and allyl cations which gave rise to a number of by-products. All transformation products were characterized by the 1H and 13C NMR spectra with detailed signal assignment.
- Klimenko,Korolev,Tomilov,Nefedov
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- Rearrangement of allyl phenyl ether over Al-MCM-41
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Claisen rearrangement of allyl phenyl ether to o-allylphenol and a dihydrobenzofuran derivative was investigated over MCM-41 with different Si/Al ratios. Higher aluminum content, higher reaction temperatures, and longer run duration favor the formation of the ring compound 2,3-dihydro-2-methyl benzofuran. There is a close relationship between acidity and conversion, which suggests that the reaction occurs inside the large pores of MCM-41. The influence of temperature and catalyst Si/Al ratio on the reaction are examined by kinetic analysis, under the assumption of a first-order consecutive reaction.
- Mathew, Nevin T.,Khaire,Mayadevi,Jha,Sivasanker
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- Reinvestigation of the isotope effects for the Claisen and aromatic claisen rearrangements: The nature of the Claisen transition states
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The aliphatic Claisen rearrangement of allyl vinyl ether and the aromatic Claisen rearrangement of allyl phenyl ether are investigated in a combined experimental and calculational study. Theoretically predicted kinetic isotope effects (KIEs) at all levels disagree with about half of the literature experimental heavy-atom isotope effects. New experimental 13C and 2H isotope effects were determined by multisite NMR methodology at natural abundance, and 17O isotope effects were determined by novel NMR methodology. These new experimental isotope effects are inconsistent with the literature values and agree well the high-level predicted KIEs, suggesting that the prior theory/experiment disagreement results from inaccuracy in the experimental KIEs. A one-dimensional tunneling correction is found to improve kinetic isotope effect predictions in a number of reactions and is found to be sufficient to provide differences between predicted and experimental heavy-atom isotope effects on the order of the experimental uncertainty in the reactions studied. The best agreement between experimental and predicted isotope effects is seen for the highest-level calculations. On the basis of the experimentally supported transition state geometries, the nature of the Claisen and aromatic Claisen transition states is discussed.
- Meyer, Matthew P.,DelMonte, Albert J.,Singleton, Daniel A.
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- Claisen Rearrangement of Allyl Phenyl Ether. 1-14C and β-14C Kinetic Isotope Effects. A Clearer View of the Transition Structure
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The kinetic isotope effects, k 12C/k 14C, for the rearrangements of allyl phenyl ether and allyl phenyl ether have been measured: 1.0119+/-0.0009 and 1.0148+/-0.0005, respectively.These results, along with those reported earlier for 18O, 2-14C, ?-14C, and γ-14C, represent the first complete kinetic isotope effect (KIE) description of a pericyclic system.Modeling calculations have been applied to the haevy-atom KIE and the previously reported deuterium KIE to define the transition structure of the rearrangement more explicitly.The calculations confirm our earlier description that the Cα-O bond is 50-60percent broken while the Cγ-Cortho bond is 10-20percent formed and now provide significantly more insight to the dynamics of the rearrangement.Coupling between the phenoxy and allyl fragments is stronger, and within the fragments is weaker, than previously supposed.
- Kupczyk-Subotkowska, Lidia,Subotkowski, Witold,Saunders, William H.,Shine, Henry J.
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- Aluminium chloride-potassium iodide-acetonitrile system: A mild reagent system for aromatic claisen rearrangement at ambient temperature
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Claisen rearrangement is used as the standard methods for the generation of complex organic substance. It is one of the well-known methods for the introduction of carbon-carbon bond. We have developed a protocol using allyl aryl ether as a substrate and AlCl3-KI as a mild reagent system and acetonitrile (CH3CN) is taken as solvent at ambient temperature. The reagent system presented in this current work is found to be appropriate for Claisen rearrangement of several aromatic alcohols with excellent yields.
- Bhattacharyya, Nayan Kamal,Dutta, Deepjyoti,Biswas, Joydeep
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- Allylphenols as a new class of human 15-lipoxygenase-1 inhibitors
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In this study, a series of mono- and diallylphenol derivative were designed, synthesized, and evaluated as potential human 15-lipoxygenase-1 (15-hLOX-1) inhibitors. Radical scavenging potency of the synthetic allylphenol derivatives was assessed and the results were in accordance with lipoxygenase (LOX) inhibition potency. It was found that the electronic natures of allyl moiety and para substituents play the main role in radical scavenging activity and subsequently LOX inhibition potency of the synthetic inhibitors. Among the synthetic compounds, 2,6-diallyl-4-(hexyloxy)phenol (42) and 2,6-diallyl-4-aminophenol (47) showed the best results for LOX inhibition (IC50 = 0.88 and 0.80 μM, respectively).
- Alavi, Seyed Jamal,Seyedi, Seyed Mohammad,Saberi, Satar,Safdari, Hadi,Eshghi, Hossein,Sadeghian, Hamid
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p. 259 - 266
(2020/10/12)
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- Novel potent (dihydro)benzofuranyl piperazines as human histamine receptor ligands – Functional characterization and modeling studies on H3 and H4 receptors
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Histamine acts through four different receptors (H1R-H4R), the H3R and H4R being the most explored in the last years as drug targets. The H3R is a potential target to treat narcolepsy, Parkinson's disease, epilepsy, schizophrenia and several other CNS-related conditions, while H4R blockade leads to anti-inflammatory and immunomodulatory effects. Our group has been exploring the dihydrobenzofuranyl-piperazines (LINS01 series) as human H3R/H4R ligands as potential drug candidates. In the present study, a set of 12 compounds were synthesized from adequate (dihydro)benzofuran synthons through simple reactions with corresponding piperazines, giving moderate to high yields. Four compounds (1b, 1f, 1g and 1h) showed high hH3R affinity (pKi > 7), compound 1h being the most potent (pKi 8.4), and compound 1f showed the best efficiency (pKi 8.2, LE 0.53, LLE 5.85). BRET-based assays monitoring Gαi activity indicated that the compounds are potent antagonists. Only one compound (2c, pKi 7.1) presented high affinity for hH4R. In contrast to what was observed for hH3R, it showed partial agonist activity. Docking experiments indicated that bulky substituents occupy a hydrophobic pocket in hH3R, while the N-allyl group forms favorable interactions with hydrophobic residues in the TM2, 3 and 7, increasing the selectivity towards hH3R. Additionally, the importance of the indole NH in the interaction with Glu5.46 from hH4R was confirmed by the modeling results, explaining the affinity and agonistic activity of compound 2c. The data reported in this work represent important findings for the rational design of future compounds for hH3R and hH4R.
- Corrêa, Michelle F.,Balico-Silva, André L.,Kiss, Dóra J.,Fernandes, Gustavo A.B.,Maraschin, Jhonatan C.,Parreiras-e-Silva, Lucas T.,Varela, Marina T.,Sim?es, Sarah C.,Bouvier, Michel,Keser?, Gy?rgy M.,Costa-Neto, Claudio M.,Fernandes, Jo?o Paulo S.
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- Nickel-Catalyzed Negishi-Type Arylation of Trialkylsulfonium Salts
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Negishi-type arylation of trialkylsulfonium salts with arylzinc reagents has been accomplished under nickel catalysis. The use of cyclohexanethiol as an additional ligand was found to be particularly important to promote C-S cleavage. The present reaction accommodates one-pot arylation of dialkyl sulfides by combining with S -methylation with MeOTf. Mechanistic experiments suggest that C-S cleavage would proceed via single-electron transfer (SET) to generate the most stable carbon-centered radical and that the thiolate ligand would promote the C-S cleavage and radical recombination step.
- Minami, Hiroko,Nogi, Keisuke,Yorimitsu, Hideki
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p. 1542 - 1546
(2021/09/06)
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- Investigating the microwave-accelerated Claisen rearrangement of allyl aryl ethers: Scope of the catalysts, solvents, temperatures, and substrates
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The microwave-accelerated Claisen rearrangement of allyl aryl ethers was investigated, in order to gain insight into the scope of the catalysts, solvents, temperatures, and substrates. Among the catalysts examined, phosphomolybdic acid (PMA) was found to greatly accelerate the reaction in NMP, at temperatures ranging from 220 to 300 °C. This method was found to be useful for preparing several intermediates previously reported in the literature using precious metal catalysts such as Au(I), Ag(I), and Pt(II). Additionally, substrates bearing bromo and nitro groups on the aryl portion required careful tailoring of the reaction conditions to avoid complex product profiles.
- Hui, Zi,Jiang, Songwei,Qi, Xiang,Ye, Xiang-Yang,Xie, Tian
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- Subsupercritical Water Generated by Inductive Heating Inside Flow Reactors Facilitates the Claisen Rearrangement
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Claisen rearrangement of electron-deficient O-allylated phenols, including fluorine-modified phenols, is facilitated in aqueous media at high temperatures and pressures under flow conditions, as opposed to organic solvents. The O-allylation of phenols can be coupled with the Claisen rearrangement in an integrated flow system.
- Oltmanns, Mona,Kirschning, Andreas
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supporting information
p. 1942 - 1946
(2020/11/13)
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- Profiling of LINS01 compounds at human dopamine D2 and D3 receptors
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Abstract: Histamine and dopamine neuronal pathways display interesting overlapping in the CNS, especially in the limbic areas, making them very attractive to designing drugs with synergistic and/or additive effects. The roles of these systems to treat schizophrenia, drug addiction, Parkinson’s and Alzheimer’s diseases, among others are widely known. The LINS01 compounds were previously reported as histamine H3 receptor (H3R) antagonists and some of them are under evaluation in rodent memory models. Considering their pharmacological potential and similarities to literature dopamine D2 receptor (D2R) and dopamine D3 receptor (D3R) ligands, this work aimed to evaluate these compounds as ligands these receptors by using [3H]spiperone displacement assays. A set of 11 compounds containing the dihydrobenzofuranyl-piperazine core with substituents at 5-position of dihydrobenzofuran ring and at the piperazine nitrogen was examined. The compounds showed low to moderate affinities at both, D2R and D3R. N-Phenyl compounds LINS01005 (1d), LINS01011 (1h), LINS01012 (1i) and LINS01016 (1k) showed the highest affinities in the set to D3R (Ki 0.3–1.5 μM), indicating that N-phenylpiperazine moiety increases the affinity to this receptor subtype with some selectivity, since they showed lower affinities to D2R (Ki 1.3–5.5 μM). With the LINS01 compounds showing moderate binding affinity, new lead structures for optimization with regards to combined H3R and D2R/D3R-ligands are provided. Graphic abstract: Histamine and dopamine neuronal pathways display interesting overlapping in the CNS, and thus LINS01 compounds previously reported as histamine H3 receptor antagonists were evaluated as dopamine D2R and D3R ligands. The compounds showed micromolar affinities to both receptors[Figure not available: see fulltext.].
- Corrêa, Michelle F,Reiner, David,Fernandes, Gustavo A B,Varela, Marina T,Aranha, Cecília M S Q,Stark, Holger,Fernandes, Jo?o Paulo S
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- Pharmacological and SAR analysis of the LINS01 compounds at the human histamine H1, H2, and H3 receptors
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Histamine is a transmitter that activates the four receptors H1R to H4R. The H3R is found in the nervous system as an autoreceptor and heteroreceptor, and controls the release of neurotransmitters, making it a potential drug target for neuropsychiatric conditions. We have previously reported that the 1-(2,3-dihydro-1-benzofuran-2-yl)methylpiperazines (LINS01 compounds) have the selectivity for the H3R over the H4R. Here, we describe their pharmacological properties at the human H1R and H2R in parallel with the H3R, thus providing a full analysis of these compounds as histamine receptor ligands through reporter gene assays. Eight of the nine LINS01 compounds inhibited H3R-induced histamine responses, but no inhibition of H2R-induced responses was seen. Three compounds were weakly able to inhibit H1R-induced responses. No agonist responses were seen to any of the compounds at any receptor. SAR analysis shows that the N-methyl group improves H3R affinity while the N-phenyl group is detrimental. The methoxy derivative, LINS01009, had the highest affinity.
- Corrêa, Michelle Fidelis,Barbosa, álefe Jhonatas Ramos,Fernandes, Gustavo Ariel Borges,Baker, Jillian G.,Fernandes, Jo?o Paulo dos Santos
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- Quality-In(Process)Line (QuIProLi) process intensification for a micro-flow UV-photo synthesis enabled by online UHPLC analysis
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Process intensification commonly enables reaction acceleration and therefore continuous-flow/PAT is urgently needed. The low volumes typical for micro-flow pose challenges for online sampling operations in analytics. In this paper, a very fast process is combined with a modified ultra-high-performance liquid chromatography (UHPLC) system allowing for very fast sampling and analysis. Low-volume online sampling according to the needs posed by PAT for pharma quality control, is introduced here for UHPLC analysis of the photo-Claisen rearrangement in micro-flow. Chances and challenges are critically reviewed, including the reproducibility and robustness of the sampling. Furthermore, the ability and speed of the chosen set-up in order to capture process changes and adjust the process parameters properly is investigated. With the applied online sampling system, it was possible to perform, almost unattended and spending 12 times less sampling volume, a full factorial analysis of all relevant reaction conditions (243 experiments) in three days. Such quality-in-the-process-line (QuIProLi) online sampling avoided random errors due to automation.
- Escribà-Gelonch, Marc,Shahbazali, Elnaz,Honing, Maarten,Hessel, Volker
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p. 3143 - 3151
(2018/02/19)
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- Palladium-Catalyzed Fluoroalkylative Cyclization of Olefins
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A palladium-catalyzed fluoroalkylative cyclization of olefins with readily available Rf-I reagents to afford the corresponding fluoroalkylated 2,3-dihydrobenzofuran and indolin derivatives with moderate to excellent yields is reported. This novel procedure provides an efficient method for the construction of Csp3-CF2 and C-O/N bonds in one step. A wide range of functional groups are tolerated. It is proposed that a radical/SET (single electron transfer) pathway proceeding via the fluoroalkyl radical may be involved in the catalytic cycle.
- Liao, Jianhua,Fan, Lianfeng,Guo, Wei,Zhang, Zhenming,Li, Jiawei,Zhu, Chuanle,Ren, Yanwei,Wu, Wanqing,Jiang, Huanfeng
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supporting information
p. 1008 - 1011
(2017/03/15)
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- Development and Mechanistic Study of Quinoline-Directed Acyl C-O Bond Activation and Alkene Oxyacylation Reactions
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The intramolecular addition of both an alkoxy and acyl substituent across an alkene, oxyacylation of alkenes, using rhodium catalyzed C-O bond activation of an 8-quinolinyl ester is described. Our unsuccessful attempts at intramolecular carboacylation of ketones via C-C bond activation ultimately informed our choice to pursue and develop the intramolecular oxyacylation of alkenes via quinoline-directed C-O bond activation. We provide a full account of our catalyst discovery, substrate scope, and mechanistic experiments for quinoline-directed alkene oxyacylation.
- Hoang, Giang T.,Walsh, Dylan J.,McGarry, Kathryn A.,Anderson, Constance B.,Douglas, Christopher J.
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p. 2972 - 2983
(2017/03/23)
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- Green Organocatalytic Synthesis of Dihydrobenzofurans by Oxidation-Cyclization of Allylphenols
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A green and cheap protocol for the synthesis of dihydrobenzofurans via an organocatalytic oxidation of o -allylphenols is presented. The use of 2,2,2-trifluoroacetophenone and H 2 O 2 as the oxidation system, leads to a highly useful synthetic method, where a variety of substituted o -allylphenols were cyclized in high yields..
- Triandafillidi, Ierasia,Sideri, Ioanna K.,Tzaras, Dimitrios Ioannis,Spiliopoulou, Nikoleta,Kokotos, Christoforos G.
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supporting information
p. 4254 - 4260
(2017/09/12)
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- Ether bond breakage method for phenylalkyl ethers
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The invention discloses an ether bond breakage method for phenylalkyl ethers. The method comprises the step: subjecting the phenylalkyl ethers to an ether bond breakage reaction at the temperature of -20 DEG C to reflux temperature in an organic solvent in the presence of aluminum triiodide and carbodiimide, so as to produce phenols and derivatives thereof. The method is moderate in conditions, simple and convenient in operation, high in yield and wide in applicable phenylalkyl ether range.
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Paragraph 0204; 0208
(2017/07/19)
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- The "chaperone" effect in microwave-driven reactions
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Chemically reactive molecules that are poor absorbers of microwave radiation can be selectively heated by the microwave and can experience chemical-rate enhancement if they are associated (agglomerated) in solution with non-reactive polar molecules that are strong microwave absorbers.
- Wu, Yu,Gagnier, Josh,Dudley, Gregory B.,Stiegman
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supporting information
p. 11281 - 11283
(2016/09/21)
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- Tandem Claisen Rearrangement/6-endo Cyclization Approach to Allylated and Prenylated Chromones
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Allyl, dimethylallyl and prenyl ethers derived from o-acylphenols reacted upon microwave irradiation to form C-allylated or -prenylated chromone derivatives, depending on the substitution pattern of the arene and the allyl substituent. The reaction proceeds through a tandem Claisen rearrangement and 6-endo-trig or 6-endo-dig cyclization sequence. For prenyl ethers, the tandem sequence can be extended by a Cope rearrangement to furnish 6-prenylchromones. The method is potentially useful for the synthesis of natural products and drugs.
- Schmidt, Bernd,Riemer, Martin,Schilde, Uwe
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supporting information
p. 7602 - 7611
(2016/01/25)
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- Investigation on Claisen rearrangement of allyl phenyl ethers in near-critical water
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Catalyst-free Clasien rearrangement of allyl phenyl ethers were investigated in near-critical water. The effects on the reaction in near-critical water and conventional conditions were compared. The results demonstrate that near-critical water could greatly accelerate the Claisen rearrangement of allyl phenyl ethers. This process is simple, fast, efficient and environmentally benign.
- Xiao, Shangyou,He, Yi,Xu, Guang,Liu, Qi
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p. 3299 - 3305
(2015/06/08)
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- Asymmetric Pd-Catalyzed Alkene Carboamination Reactions for the Synthesis of 2-Aminoindane Derivatives
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A new type of Pd-catalyzed alkene carboamination reaction that provides direct access to enantioenriched 2-aminoindanes from 2-allylphenyltriflate derivatives and aliphatic amines is described. A catalyst generated in situ from Pd(OAc)2 and (S)-tert-butylPHOX provides the functionalized carbocycles in good yield with up to >99:1 er. The transformations occur via a key anti-aminopalladation that involves intermolecular attack of an amine nucleophile on an arylpalladium alkene complex.
- White, Derick R.,Hutt, Johnathon T.,Wolfe, John P.
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supporting information
p. 11246 - 11249
(2015/09/21)
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- Microwave-assisted organic syntheses: Microwave effect on intramolecular reactions-the Claisen rearrangement of allylphenyl ether and 1-allyloxy-4-methoxybenzene
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This article examined how and the possible effect microwaves may have on intramolecular reactions such as those of the Claisen-type rearrangement carried out in dimethyl sulfoxide (DMSO) solvent and in solvent-free, microwave irradiation conditions. For comparison, the reaction was also performed by conventional heating using an oil bath. 2-Allylphenol was synthesized from allylphenyl ether in DMSO solvent under stirring conditions as a model intramolecular reaction taking place via the Claisen rearrangement using a commercial microwave chemical apparatus together with conventional heating; no enhancement of the reaction occurred. To further examine the influence of microwave irradiation on Claisen rearrangement reactions, we also investigated the transformation of 1-allyloxy-4-methoxybenzene to 2-allyl-4-methoxyphenol under both solvent-free conditions (no stirring) and in DMSO medium; here also no reaction enhancement was observed. This notwithstanding, microwaves did impact the formation of a by-product formed in the latter reaction, which was identified by GC and GC/MS as 4-methoxyphenol, the yield of which was nearly fourfold greater (ca. 6%) under microwave irradiation than under oil-bath heating (ca. 1.5%). The latter suggests that under solvent-free conditions a microwave non-thermal effect influenced the formation of this by-product during the Claisen rearrangement process, contrary to the case where the reaction was performed in DMSO medium for which the yields were identical (ca. 2.5%), regardless of whether the reactant was microwave or oil-bath heated.
- Horikoshi, Satoshi,Watanabe, Tomoki,Kamata, Momoko,Suzuki, Yumiko,Serpone, Nick
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p. 90272 - 90280
(2015/11/11)
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- Synthesis of phosphorus containing medium ring heterocycles by sequential Claisen rearrangement and ring closing metathesis
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An efficient method for the synthesis of novel medium ring phosphorus containing heterocycles starting from phenol derivatives by ruthenium catalyzed ring closing metathesis is described. This work deals with a sequential aromatic Claisen-rearrangement, coupling of an allyl/vinyl phosphonate, and ring closing metathesis reaction. All of these reactions were carried out at ambient temperature to afford the medium-sized phosphorus heterocycles in excellent yields.
- Majumdar,Nandi, Raj Kumar,Ganai, Sintu
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p. 1247 - 1250
(2014/02/14)
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- ANTHELMINTIC COMPOUNDS AND COMPOSITIONS AND METHOD OF USING THEREOF
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The present invention relates to novel anthelmintic compounds of formula (I) below: wherein Y and Z are independently a bicyclic carbocyclic or a bicyclic heterocyclic group, or one of Y or Z is a bicyclic carbocyclic or a bicyclic heterocyclic group and the other of Y or Z is alkyl, alkenyl, alkynyl, cycloalkyl, phenyl, heterocyclyl or heteroaryl, and variables X1, X2, X3, X4, X5, X6, X7 and X8 are as defined herein. The invention also provides for veterinary compositions comprising the anthelmintic compounds of the invention, and their uses for the treatment and prevention of parasitic infections in animals.
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Paragraph 0484; 0485
(2014/05/25)
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- Whole ceramic-like microreactors from inorganic polymers for high temperature or/and high pressure chemical syntheses
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Two types of whole ceramic-like microreactors were fabricated from inorganic polymers, polysilsesquioxane (POSS) and polyvinylsilazane (PVSZ), that were embedded with either perfluoroalkoxy (PFA) tube or polystyrene (PS) film templates, and subsequently the templates were removed by physical removal (PFA tube) or thermal decomposition (PS). A POSS derived ceramic-like microreactor with a 10 cm long serpentine channel was obtained by an additional "selective blocking of microchannel" step and subsequent annealing at 300 °C for 1 h, while a PVSZ derived ceramic-like microreactor with a 14 cm long channel was yielded by a co-firing process of the PVSZ-PS composite at 500°C for 2 h that led to complete decomposition of the film template leaving a microchannel behind. The obtained whole ceramic-like microfluidic devices revealed excellent chemical and thermal stabilities in various solvents, and they were able to demonstrate unique chemical performance at high temperature or/and high pressure conditions such as Michaelis-Arbuzov rearrangement at 150-170°C, Wolff-Kishner reduction at 200°C, synthesis of super-paramagnetic Fe3O4 nanoparticles at 320°C and isomerisation of allyloxybenzene to 2-allylphenol (250°C and 400 psi). These economic ceramic-like microreactors fabricated by a facile non-lithographic method displayed excellent utility under challenging conditions that is superior to any plastic microreactors and comparable to glass and metal microreactors with high cost.
- Ren, Wurong,Perumal, Jayakumar,Wang, Jun,Wang, Hao,Sharma, Siddharth,Kim, Dong-Pyo
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p. 779 - 786
(2014/02/14)
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- Chroman-4-ones via microwave-promoted domino Claisen rearrangement-oxa-michael addition: Synthesis of tabchromones A and B
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Allyl phenyl ethers with a pendant enone substituent undergo, upon microwave irradiation, a domino sequence of Claisen rearrangement and 6-endo-trig-cyclization to furnish functionalized chroman-4-ones. The natural products tabchromones A and B were synthesized via this method.
- Schmidt, Bernd,Riemer, Martin,Schilde, Uwe
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p. 2943 - 2946
(2015/02/05)
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- Enantioselective synthesis of benzofurans and benzoxazines via an olefin cross-metathesis-intramolecular oxo-Michael reaction
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Chiral phosphoric acid and Hoveyda-Grubbs II were found to catalyze an olefin cross-metathesis-intramolecular oxo-Michael cascade reaction of the ortho-allylphenols and enones to provide a variety of benzofuran and benzoxazine derivatives in moderate to good yields and enantioselectivity.
- Zhang, Jun-Wei,Cai, Quan,Gu, Qing,Shi, Xiao-Xin,You, Shu-Li
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supporting information
p. 7750 - 7752
(2013/09/02)
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- SUBSTITUTED HYDRAZIDE COMPOUNDS AND USE THEREOF
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The invention relates to substituted hydrazide compounds as shown by general formula I, including geometrical isomers, pharmaceutically acceptable salts, hydrates, solvates or prodrugs thereof, and use of the same, wherein the substitutents Ar and R have the same meanings as given in the Description. The invention further relates to the use of compounds of general formula I in the preparation of medicament for the treatment and/or prevention of cancer and other proliferative diseases.
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Page/Page column 13
(2012/06/16)
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- SUBSTITUTED HYDRAZIDE COMPOUNDS AND APPLICATION THEREOF
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The invention relates to substituted hydrazide compounds as shown by general formula I, including geometrical isomers, pharmaceutically acceptable salts, hydrates, solvates or prodrugs thereof, and use of the same, wherein the substitutents Ar and R having the same meanings as given in the Description. T The invention further relates to the use of compounds of general formula I in the preparation of medicament for the treatment and/or prevention of cancer and other proliferative diseases.
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Page/Page column 14
(2012/07/03)
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- Synthesis of novel H-shaped chromophores
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A series of H-shaped chromophores with two parallel and non-conjugated D-π-A units have been synthesized, in which a 9,10-dihydroanthracene was employed as molecular backbone. The synthesis of these H-shaped chromophores 9a-11a was accomplished via an eight-step reaction, including double Claisen rearrangement, hydroboration-oxidation, Rieche formylation reaction, Knoevenagel condensation and Corey-Fuchs reaction, with a total yield about 12.5%. The corresponding mono-D-π-A unit compounds 9b-11b were also prepared in a similar procedure for the purpose of comparison. Crystal structures of three intermediates 5a, 7a and 8a were measured, which demonstrate that the two D-π-A units in a single H-shaped chromophore molecule are nearly arranged at the same direction. The studies of UV-vis spectra and the solvatochromic method indicate that the molecular second-order polarizabilities values (μβ) of H-shaped chromophores are remarkably increased compared with the corresponding mono-D-π-A unit reference compounds, without causing a large shift of the absorption band to longer wavelength.
- Shi, Jie-Ping,Wu, De-Lin,Ding, Yong,Wu, Dong-Hua,Hu, Hong-Wen,Lu, Guo-Yuan
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scheme or table
p. 2770 - 2777
(2012/04/23)
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- Preparation, characterization and use of 1,3-disulfonic acid imidazolium hydrogen sulfate as an efficient, halogen-free and reusable ionic liquid catalyst for the trimethylsilyl protection of hydroxyl groups and deprotection of the obtained trimethylsilanes
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Novel 1,3-disulfonic acid imidazolium hydrogen sulfate, a halogen-free ionic liquid, is a recyclable and eco-benign catalyst for the trimethylsilyl protection of hydroxyl groups at room temperature under solvent free conditions to afford trimethylsilanes in excellent yields (92-100%) and in very short reaction times (1-5 min). Deprotection of the resulting trimethylsilanes can also be achieved using the same catalyst in methanol. The catalyst was characterized by IR, 1H NMR, 13C NMR and MS studies. All the products were extensively characterized by IR, 1H NMR, MS, and elemental and melting point analyses. This new method consistently has the advantages of excellent yields and short reaction times. Further, the catalyst can be recovered and reused for several times without loss of activity. The work-up of the reaction consists of a simple separation, followed by concentration of the crude product and purification.
- Shirini, Farhad,Khaligh, Nader Ghaffari,Akbari-Dadamahaleh, Somayeh
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- Nanocrystalline TiO2-HClO4 as a new, efficient and recyclable catalyst for the chemoselective trimethylsilylation of alcohols, phenols and deprotection of silyl ethers
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TiO2-HClO4, as a new solid acid, was found to be an efficient catalyst for the chemoselective trimethylsilylation of alcohols and phenols. Deprotection of the resulting trimethylsilylethers was achieved using the same catalyst in methanol solvent. The synthesized catalyst was characterized by FT-IR, SEM, TEM, BET and XRD analyses. Our novel synthetic method has the advantages of high yields, short reaction times, low cost and recyclability of the catalyst, simplicity and easy work-up compared to the conventional methods reported in the literature.
- Shirini, Farhad,Atghia, Seyyed Vahid,Jirdehi, Mojtaba Ghazi
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- Gas-phase generation and cyclisation reactions of imidoyl radicals
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Some 1,2-diarylimidoyl radicals were generated in the gas-phase by intramolecular radical translocation from ortho-imino-aryloxyl radicals, in turn generated under flash vacuum pyrolysis (FVP) conditions. The imidoyls reacted with XR ortho′-substituents in the N-aryl group to give (in most cases) modest yields of cyclisation products. Depending on the nature of the bridging atom (X), the formation of these products was initiated either by a further hydrogen atom translocation (X = CH2), or by ipso-attack onto the aryl group (R = Ph), or by direct substitution at the heteroatom (X = S). With XR = N(Me)Ph, the major reaction product was probably the result of a competing pathway not involving the corresponding imidoyl.
- Leardini, Rino,McNab, Hamish,Nanni, Daniele,Tenan, Anton G.,Thomson, Andrew
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experimental part
p. 623 - 630
(2012/02/05)
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- Design, synthesis and cytotoxic activities of novel hybrid compounds between dihydrobenzofuran and imidazole
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A series of novel hybrid compounds between dihydrobenzofuran and imidazole has been prepared and evaluated in vitro against a panel of human tumor cell lines. The results suggest that substitution of the imidazolyl-1-position with an electron-donating dihydrobenzofuran, and the imidazolyl-3-position with a naphthylacyl or electron-rich phenacyl group, were vital for modulating cytotoxic activity.
- Chen, Wen,Yang, Xiao-Dong,Li, Yan,Yang, Li-Juan,Wang, Xue-Quan,Zhang, Gao-Lan,Zhang, Hong-Bin
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supporting information; experimental part
p. 4250 - 4255
(2011/07/29)
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- Insertion of an Alkene into an ester: Intramolecular oxyacylation reaction of alkenes through acyl C-O bond activation
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Atom economy and esters: compatible now! The first catalytic insertion of a C-C bond into an acyl C-O bond was achieved using rhodium catalysts (see scheme). The products are β-alkoxy ketones with a fully substituted carbon center. Quinoline chelating groups were employed to stabilize the Rh-alkoxide intermediate.
- Hoang, Giang T.,Reddy, Venkata Jaganmohan,Nguyen, Huy H. K.,Douglas, Christopher J.
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supporting information; scheme or table
p. 1882 - 1884
(2011/04/16)
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- Hydroxy- and aminophenyl radicals from arenediazonium salts
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Arenediazonium salts are well-known sources of aryl radicals; however, the hydroxy- and amino-substituted derivatives 1, 2, and 3, which lead to the respective formation of radicals 4, 5, and 6, have rarely been employed in synthetic organic chemistry so far. New synthetic applications of these species have been found, and the properties that may have previously hindered their successful use have been investigated. Copyright
- Pratsch, Gerald,Anger, Christian A.,Ritter, Katharina,Heinrich, Markus R.
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experimental part
p. 4104 - 4108
(2011/05/12)
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- Imidazolium and pyridinium salts - Solvents influencing the rate and direction of the fries, beckmann, and claisen rearrangements
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The Fries, Beckmann, and Claisen rearrangements have been investigated in ionic liquid media. The effect of the structural elements of the latter on the direction of these rearrangements and the product yields has been studied.
- Katkevica,Zicmanis,Mekss
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experimental part
p. 158 - 169
(2011/08/05)
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- Microwave-assisted zeolite catalyzed claisen rearrangement of allyl aryl ethers under solvent-free conditions
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Claisen rearrangement of allyl aryl ethers has been studied extensively over various zeolites under microwave activation and solvent free conditions at 80°C. Hβ-zeolite is found to be an efficient catalyst for the rearrangement. The reaction gives ω-rearranged product selectively instead of expected further cyclized dihydrobenzofuran derivative.
- Deodhar, Deepak K.,Tipnis, Amol S.,Samant, Shriniwas D
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experimental part
p. 1552 - 1555
(2011/02/23)
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- Sintered silicon carbide: A new ceramic vessel material for microwave chemistry in single-mode reactors
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Silicon carbide (SiC) is a strongly microwave absorbing chemically inert ceramic material that can be utilized at extremely high temperatures due to its high melting point and very low thermal expansion coefficient. Microwave irradiation induces a flow of electrons in the semiconducting ceramic that heats the material very efficiently through resistance heating mechanisms. The use of SiC carbide reaction vessels in combination with a single-mode microwave reactor provides an almost complete shielding of the contents inside from the electromagnetic field. Therefore, such experiments do not involve electromagnetic field effects on the chemistry, since the semiconducting ceramic vial effectively prevents microwave irradiation from penetrating the reaction mixture. The involvement of electromagnetic field effects (specific/nonthermal microwave effects) on 21 selected chemical transformations was evaluated by comparing the results obtained in microwave-transparent Pyrex vials with experiments performed in SiC vials at the same reaction temperature. For most of the 21 reactions, the outcome in terms of conversion/purity/product yields using the two different vial types was virtually identical, indicating that the electromagnetic field had no direct influence on the reaction pathway. Due to the high chemical resistance of SiC, reactions involving corrosive reagents can be performed without degradation of the vessel material. Examples include high-temperature fluorine-chlorine exchange reactions using triethylamine trihydrofluoride, and the hydrolysis of nitriles with aqueous potassium hydroxide. The unique combination of high microwave absorptivity, thermal conductivity, and effusivity on the one hand, and excellent temperature, pressure and corrosion resistance on the other hand, makes this material ideal for the fabrication of reaction vessels for use in microwave reactors. Simulating conductive heat transfer in a microwave: Using reaction vials made out of strongly microwave-absorbing silicon carbide (SiC) in a microwave reactor simulates a conductively heated autoclave experiment due to efficient shielding of the electromagnetic field by the SiC vial. Advantages of SiC vials for microwave processing include their excellent corrosion resistance, thermal stability, and high thermal effusivity and conductivity.
- Gutmann, Bernhard,Obermayer, David,Reichart, Benedikt,Prekodravac, Bojana,Irfan, Muhammad,Kremsner, Jennifer M.,Kappe, C. Oliver
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supporting information; experimental part
p. 12182 - 12194
(2011/02/23)
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- Continuous-Flow microreactor Chemistry under High-Temperature/pressure
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High-temperature organic synthesis can be performed under continuous-flow conditions in a stainless steel microtubular flow reactor capable of achieving temperatures of 350 °C and 200 bar. Under these extreme experimental environments transformations normally performed in a high-boiling solvent at reflux temperature - or under sealed-vessel microwave conditions - can be readily converted to a flow regime by using lower boiling solvents in or near their supercritical state. Wiley-VCH Verlag GmbH & Co, KGaA.
- Razzaq, Tahseen,Glasnov, Toma N.,Kappe, C. Oliver
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supporting information; experimental part
p. 1321 - 1325
(2009/07/26)
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- Microwave chemistry in silicon carbide reaction vials: Separating thermal from nonthermal effects
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Running oil-bath chemistry in a microwave! Using reaction vials made out of strongly microwave-absorbing silicon carbide (SiC) in a microwave reactor simulates experiments conducted in an autoclave with conductive heating because of the efficient shielding of the electromagnetic field by the SiC vial. This technology makes it possible to study the significance of microwave effects.
- Obermayer, David,Gutmann, Bernhard,Oliver Kappe
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supporting information; scheme or table
p. 8321 - 8324
(2010/01/06)
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- Synthesis of 6,6-bisbenzannulated spiroketals related to the rubromycins using a double intramolecular hetero-Michael addition (DIHMA)
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The synthesis of a series of 6,6-bisbenzannulated spiroketals using a novel microwave-assisted DIHMA approach is reported. Coupling of an aryl acetylene and an aryl aldehyde via acetylide anion addition resulted in the formation of an alkynol which was followed by oxidation to the desired ynone. Spirocyclization using the DIHMA protocol afforded the desired bisbenzannulated spiroketal in good yield.
- Choi, Peter J.,Rathwell, Dominea C.K.,Brimble, Margaret A.
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scheme or table
p. 3245 - 3248
(2009/08/17)
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- Identification of a boron-containing intermediate in the boron tribromide mediated aryl propargyl ether cleavage reaction
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An alternate reaction mechanism for the boron tribromide mediated deprotection of aryl propargyl ethers based on the isolation of a key boron-containing byproduct is proposed. On the basis of the new mechanistic insight, we discovered that HBBr2 · SMe2 can also be used for cleaving aryl propargyl ethers.
- Yao, Min-Liang,Reddy, Marepally Srinivasa,Zeng, Wenbin,Hall, Kelly,Walflsh, Ingrid,Kabalka, George W.
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supporting information; experimental part
p. 1385 - 1387
(2009/07/04)
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- Biological Polysiloxanes
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The present invention relates to a macromonomer having a polydimethylsiloxane backbone that has a mol % dimethyl siloxanes, b mol % siloxanes substituted with -K-RIM, c mol % siloxanes substituted with -K-RIM-Z and d mol % siloxanes substituted with -L-Z, and in which the terminal siloxane groups are tri-substituted with R, wherein RIM is a refractive index modifying group; Z is a free radically polymerisable group; K is a spacer group; L is optional and is a spacer group; each R is independently selected from an RIM, a lower alkyl group, hydrogen or Z; and a is a molar percentage of the macromonomer which is in the range of from 0 to 95 mol %; b is a molar percentage of the macromonomer which is in the range of from 5 to 99 mol %; c is a molar percentage of the macromonomer which is in the range of from 0 to 2 mol %; and d is a molar percentage of the macromonomer which is in the range of from 0 to 2 mol %; with the proviso that c and d are not both 0 mol %.
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- Investigating the existence of nonthermal/specific microwave effects using silicon carbide heating elements as power modulators
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(Chemical Equation Presented) The use of passive heating elements made out of chemically inert sintered silicon carbide (SiC) allows microwave transparent or poorly absorbing reaction mixtures to be heated under microwave conditions. The cylindrical heating inserts efficiently absorb microwave energy and subsequently transfer the generated thermal energy via conduction phenomena to the reaction mixture. In the case of low to medium microwave absorbing reaction mixtures, the addition of SiC heating elements results in significant reductions (30-70%) in the required microwave power as compared to experiments performed without heating element at the same temperature. The method has been used to probe the influence of microwave power (electromagnetic field strength) on chemical reactions. Six diverse types of chemical transformations were performed in the presence or absence of a SiC heating element at the same reaction temperature but at different microwave power levels. In all six cases, the measured conversions/yields were similar regardless of whether a heating element was used or not. The applied microwave power had no influence on the reaction rate, and only the attained temperature governed the outcome of a specific chemical process under microwave conditions.
- Razzaq, Tahseen,Kremsner, Jennifer M.,Kappe, C. Oliver
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p. 6321 - 6329
(2008/12/22)
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- Synthesis of 3-aryl-2,5-dihydro-1-benzoxepines from phenol via ring-closing metathesis
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In this paper, the synthesis of 3-aryl-2,5-dihydro-1-benzoxepines is described. While the reaction was started from phenol and based on the sequential reactions such as Claisen rearrangement, O-alkylation, Wittig reaction, and ring-closing metathesis (RCM), a series of new 3-aryl-1-benzoxepines were prepared in good overall yields.
- Tsai, Jui-Chi,Li, Sie-Rong,Chen, Liang-Yeu,Chen, Po-Yuan,Joung, Jia-Ying,Shu, Chung-Jung,Lo, Yu-Fuan,Lin, Chun-Nan,Wang, Eng-Chi
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experimental part
p. 1317 - 1321
(2009/12/03)
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- Scale-up of microwave-promoted reactions to the multigram level using a sealed-vessel microwave apparatus
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A range of synthetic transformations have been scaled up successfully using a sealed-vessel multimode microwave unit. These include metal-catalyzed couplings, synthesis of heterocycles, reactions under an atmosphere of reactive gas and two-step one-pot procedures. Also, observations have been made along the way that are of use to chemists addressing scale-up of microwave-promoted reactions.
- Bowman, Matthew D.,Schmink, Jason R.,McGowan, Cynthia M.,Kormos, Chad M.,Leadbeater, Nicholas E.
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p. 1078 - 1088
(2013/01/03)
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