- Halogen Bond-Catalyzed Friedel?Crafts Reactions of Furans Using a 2,2’-Bipyridine-Based Catalyst
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A halogen bond donor based on a 2,2’-bipyridine framework has been synthesized, and used to catalyze Friedel?Crafts reactions of furans. Electrophiles used successfully in these reactions included various enones, an aldehyde, and a carboxylic acid anhydride. The yields of the reactions were generally good using a moderate catalyst loading (0.025 or 0.1 equiv.) at a relatively low temperature (room temp. or 50 °C) in acetonitrile. The catalyst used was designed with a biaryl scaffold so that if it indeed proved to be an efficient halogen bond donor organocatalyst, an enantioenriched version of it could potentially serve as a stereoselective catalyst. (Figure presented.).
- Zhang, Huimiao,Toy, Patrick H.
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supporting information
p. 215 - 221
(2020/12/01)
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- A New Approach for the Synthesis of Highly Substituted Aromatic Rings: The Alkyne-Mediated Approach
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Pentasubstituted aromatic rings serve as templates for drug design and can be conveniently prepared by the thermolysis of suitably substituted alkynes under microwave conditions. Rings in the microwave! Pentasubstituted aromatic rings serve as templates for drug design and can be conveniently prepared by the thermolysis of suitably substituted alkynes under microwave conditions.
- Parsons, Philip J.,Jones, Daniel R.,Padgham, Alex C.,Allen, Lewis A. T.,Penkett, Clive S.,Green, Robert A.,White, Andrew J. P.
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supporting information
p. 3981 - 3984
(2016/03/16)
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- Photooxygenation of azidoalkyl furans: Catalyst-free triazole and new endoperoxide rearrangement
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Photooxygenation of azidoalkyl furans has revealed both a novel triazole formation method and a unique endoperoxide rearrangement. The key step of this method is a 3 + 2 cycloaddion of the azide to the endoperoxide intermediate. The reduction of the peroxide bond and two subsequent C-C bond cleavages provide a triazole having a newly formed carboxylic acid functionality. The reactions are clean and efficient with yields ranging from 60% to 90%.
- Kazancioglu, Elif Akin,Kazancioglu, Mustafa Zahrittin,Fistikci, Meryem,Secen, Hasan,Altundas, Ramazan
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supporting information
p. 4790 - 4793
(2013/10/08)
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- Photooxidations of 2-(γ,ε-dihydroxyalkyl) furans in water: Synthesis of DE-bicycles of the pectenotoxins
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Photooxygenations of 2-(γ,ε-dihydroxyalkyl) furans in H 2O followed by in situ reduction and ketalization affords, in one synthetic operation, DE-bicyclic ketals of the pectenotoxins.
- Kouridaki, Antonia,Montagnon, Tamsyn,Tofi, Maria,Vassilikogiannakis, Georgios
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supporting information; experimental part
p. 2374 - 2377
(2012/07/01)
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- The condensation of carbonyl compounds with electron-rich arenes: Mercury, thallium, gold or a proton?
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Gold(III) chloride, mercury(II) perchlorate, thallium(III) perchlorate and p-toluenesulfonic acid were found to efficiently catalyze the condensation of two furans with aldehydes or acetone. The olefinic unit of α,β- unsaturated carbonyl compounds reacts faster than the carbonyl group, other olefins do not react selectively. The first (addition) step is rate-limiting, the second (substitution) step is much faster.
- Hashmi, A. Stephen K.,Schwarz, Lothar,Rubenbauer, Philipp,Blanco, M. Carmen
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p. 705 - 708
(2007/10/03)
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- Addition of heterocycles to electron deficient olefins and alkynes catalyzed by gold(III)
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A gold(III)-catalyzed hydroarylation of different olefins is reported here. AuCl3 works as an excellent catalyst to mediate reactions between various heterocycles and electron deficient olefins and alkynes under mild conditions. This gold(III)-based method tolerates different functional groups such as aldehyde, carboxylic acid, nitrile, and is highly efficient. We have shown that some of these reactions complete in minutes at room temperature.
- Li, Zigang,Shi, Zhangjie,He, Chuan
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p. 5049 - 5054
(2007/10/03)
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- INTRAMOLECULAR DIELS-ALDER REACTION OF FURANS WITH ALLENYL ETHERS : HIGH EFFECT OF THE CHAIN LENGTH ON THE STRUCTURE AND REACTIVITY OF THE CYCLOADDUCTS
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The structure and reactivity of the cycloadducts of the title reaction were found to be highly dependent on the chain length between the furan diene and the allenyl ether dienophile.Reaction of the propargyl ether (2) with t-BuOK in the t-BuOH at 85 deg C for 3 h gave a mixture of the cycloadducts (3) and (4) in 90percent yield, which were transferred to the benzo derivatives (5), (6) and (7).Treatment of the propargyl ether (8) with t-BuOK in t-BuOH at 85 deg C for 5 h gave the products (9) and (10) in a ratio of 8:1 in 65 percent yield, no detectable amount of the cycloadduct (8b) was obtained.Refluxing of the propargyl ether (13) with t-BuOK in t-BuOH at 85 deg C for 4 h gave the allenyl ether (14).Heating 14 in DMSO at 150 deg C for 12 h still did not give 15.
- Wu, Hsien-Jen,Lin, Shie-Hsiung,Lin, Chu-Chung
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p. 1507 - 1518
(2007/10/02)
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- 2,9-DIOXABICYCLONONAN-DARSTELLUNG, MASSENSPEKTROSKOPIE UND UMLAGERUNG EINES NEUEN HETEROCYCLISCHEN SYSTEMS
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Nine different methyl-substituted compounds of a new acetal system 5 are synthesized from 4-(5-methyl-2-furyl)alkanoles 1 and are rearranged to ketones 6; mass spectroscopic fragmentation patterns are described.
- Francke, Wittko,Reith, Wolfgang
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p. 2029 - 2032
(2007/10/02)
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- Influence de la pression sur les reactions de substitution electrophile du furanne et de methyl-2 furanne
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We previously investigated the (4+2) cycloaddition reactions of 2-methylfuran, which are known to be very difficult, even impossible, under the usual conditions for Diels-Alder reactions.We found that the adducts are generated only at low temperatures (20-40 deg C) and high pressures (ca. 10 kbar)(Bull.Soc.Chim., 1978, p.461).However, by increasing the temperature, we have observed the alternative reaction consisting in the α-substitution of furan when furan compounds are allowed to react with α,β-unsaturated carbonyl compounds at temperatures above 100 deg C.We found that this reaction, which proceeds slowly (or not at all) at atmospheric pressure, is noticeably faster at high pressures.Having in mind a simple method for facile synthesis of mono- and disubstituted furans, we thought that pressure could be an interesting parameter in producing such compounds in high yield.Additionally, since the reaction was found some time ago to be very sensitive to acidic media (electrophilic substitution of the Friedel-Crafts type), we imagined that a possible pressure induced creation of charges in the transition state would give rise to an electrostriction contribution to the reaction rate.We first investigated the thermal synthesis without catalyst and found that only unsaturated carbonyl compounds show some reactivity, while unsaturated nitriles or esters do not react.However, the substitution reaction is considerably perturbed by the polymerisation reaction, which is also positively influenced by pressure and thus reduces drastically the yield of substituted products, except in some rare cases.The use of a suitable catalyst (AcOH-H2O) combined with pressure (3 000 bar) allows satisfactory yields of substituted furans with little formation of polymer.The pressure kinetics of two selected reactions reveals a strong pressure acceleration with activation volumes in the range (-45 to -50 cm3/mol) independent of the solvent.We suggest that starting from a neutral initial state, during the activation process there is a development of electrostriction with the possible appearance of strongly polarized species, the polarization being enhanced by pressure.However, in this case we would normally anticipate a solvent dependence of the activation volume ΔV(excit.); in fact this effect is not observed.Nevertheless, the hypothesis of electrostriction is quite plausible by the fact that, when the reaction is carried out in the presence of the catalyst (AcOH-H2O), the value ΔV(excit.) is reduced to half the former value (-24.5 cm3/mol), because the initial state is no longer neutral and charges are present along the activation process.
- Jenner, Gerard,Rimmelin, Jean,Antoni, Francois,Libs, Suzanne,Schleiffer, Elisabeth
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- PHARMACOLOGICALLY ACTIVE TRIAZINONES
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The compounds are substituted 1,2,4-triazin-5-ones which are histamine H 2-antagonists. Two specific compounds of the present invention are 3-2-(5-methyl-4-imidazolylmethylthio)ethylamino!-6-(3-methoxybenzyl)-1,2, 4-tr iazin-5-one and 3-2-(5-methyl-4-imidazolylmethylthio)ethylamino!-6-(3-pyridylmethyl)-1,2,4-tr iazin-5-one.
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