1745-81-9Relevant articles and documents
Degradation of lignin with aqueous ammonium-based ionic liquid solutions under milder conditions
Gupta, Bhupender S.,Lee, Ming-Jer,Tolesa, Leta Deressa
, p. 3357 - 3365 (2019)
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.
The impact of Novel Process Windows on the Claisen rearrangement
Kobayashi, Hiroki,Driessen, Brian,Van Osch, Dannie J.G.P.,Talla, Ali,Ookawara, Shinichi,No?l, Timothy,Hessel, Volker
, p. 2885 - 2890 (2013)
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.
Water-Accelerated Tandem Claisen Rearrangement-Catalytic Asymmetric Carboalumination
Wipf, Peter,Ribe, Seth
, p. 1503 - 1505 (2001)
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.
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
Firestone, Raymond A.,Vitale, Mark A.
, p. 2160 - 2164 (1981)
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.
The ene reaction between maleimides and allyl-substituted aromatics
Cunningham, Ian D.,Brownhill, Andrew,Hamerton, Ian,Howlin, Brendan J.
, p. 13473 - 13494 (1997)
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.
Heteropoly acid encapsulated SBA-15/TiO2 nanocomposites and their unusual performance in acid-catalysed organic transformations
Sawant, Dhanashri P.,Justus, Josena,Balasubramanian, Veerappan V.,Ariga, Katsuhiko,Srinivasu, Pavuluri,Velmathi, Sivan,Halligudi, Shivappa B.,Vinu, Ajayan
, p. 3200 - 3212 (2008)
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.
Photochemical electron transfer across a liquid/liquid interface: Methylene Blue-sensitized decarboxylation of substituted carboxylic acids
Das, Suresh,Thanulingam,Rajesh,George
, p. 1337 - 1340 (1995)
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.
-
Widmer,U. et al.
, p. 2644 - 2648 (1973)
-
Generation of cyclopropanediazonium and its chemical transformations in the presence of phenol
Klimenko,Korolev,Tomilov,Nefedov
, p. 1299 - 1306 (2006)
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.
Reinvestigation of the isotope effects for the Claisen and aromatic claisen rearrangements: The nature of the Claisen transition states
Meyer, Matthew P.,DelMonte, Albert J.,Singleton, Daniel A.
, p. 10865 - 10874 (1999)
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.
Aluminium chloride-potassium iodide-acetonitrile system: A mild reagent system for aromatic claisen rearrangement at ambient temperature
Bhattacharyya, Nayan Kamal,Dutta, Deepjyoti,Biswas, Joydeep
, (2021/06/28)
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.
Novel potent (dihydro)benzofuranyl piperazines as human histamine receptor ligands – Functional characterization and modeling studies on H3 and H4 receptors
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.
, (2020/12/21)
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.
Investigating the microwave-accelerated Claisen rearrangement of allyl aryl ethers: Scope of the catalysts, solvents, temperatures, and substrates
Hui, Zi,Jiang, Songwei,Qi, Xiang,Ye, Xiang-Yang,Xie, Tian
, (2020/05/18)
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.
