1667-01-2Relevant articles and documents
Synthesis and catalytic properties of large-pore Sn-β and Al-free Sn-β molecular sieves
Mal,Ramaswamy
, p. 425 - 426 (1997)
Sn-β and Al-free Sn-β (large pore, 12-membered ring channels) molecular sieves prepared by hydrothermal synthesis and characterised by XRD, FTIR and sorption techniques are distinguished by their acidic and oxidation properties, in the acetylation of 1,3,5-trimethylbenzene (1,3,5-TMB) with acetyl chloride and in the oxidation of m-cresol and 1,3,5-TMB with aqueous H2O2, respectively.
A Novel Friedel-Crafts Reaction of Hindered Ketones
Roberts, Royston M.,El-Khawaga, Ahmed M.,Roengsumran, Sophon
, p. 3180 - 3183 (1984)
Mesitylene has been shown to react with acetyl chloride in the presence of aluminium chloride to form 1,1-dimesitylethene.Acetomesitylene has been demonstrated to be an intermediate in the reaction, which proceeds in the second step by nucleophilic attack by the arene on the carbonyl group of acetomesitylene, which is activated by the formation of a polarized complex with aluminum chloride.Mesitylene reacts similarly with propionyl chloride, forming 1,1-dimesitylpropene; propiomesitylene is an intermediate.Steric and electronic factors responsible for this unique Friedel-Crafts reaction are discussed.
Studies on the Mechanism of Acid-Catalyzed Bromination of a Hindered Alkyl Aryl Ketone: 2,4,6-trimethylacetophenone. Rate Dependence on Bromine Concentration
Pinkus, A. G.,Gopalan, R.
, p. 2630 - 2636 (1984)
According to the generally accepted Lapworth mechanism for halogenation of ketones, where the rate of reaction is independent of halogen concentration, the slow, rate-determining step is the formation of enol or enolate.The rate of reaction of bromine with 2,4,6-trimethylacetophenone (1) was found to depend on bromine concentration at moderately high concentrations.In the proposed mechanism, reaction of bromine with enol is rate determining - the enolization step being faster.A carbocation (4) instead of a bromonium ion is proposed as the intermediate from reaction of enol with bromine.Rates were determined by following the decrease in bromine concentration at 449 nm under these conditions: 50percent acetic acid (v/v), HBr catalysis, and ionic strength adjusted with sodium perchlorate at 25 deg C.With excess ketone, the average pseudo-first-order rate constant was 1.82x10-3 s-1.At a fixed bromine concentration and at varying equal concentrations of both ketone and bromine, k2 values were 4.34x10-2 and 4.39x10-2 L mol-1 s-1, respectively.In studies on the effect of bromide ion on the rate, molecular bromine was found to be the active brominating agent with Br3- contributing to only 0.6percent of the rate constant.Added chloride ion increased the rate; this was explained by Br2/Cl- interchange to form Br-Cl, a more effective brominating agent.Only bromo ketone was isolated in a preparative-scale reaction containing chloride ions.Added acetate ions decreased the rate as a result of a decrease in proton concentration by formation of acetic acid.Perchloric acid increased the rate.From variable-temperature studies, Ea=61.5 kJ mol-1 and ΔH(excit.)=59.0 kJ mol-1.The rate of reaction of bromine with hindered ketone, 1, was nearly 900 times as fast as that with the unhindered analogue, acetophenone, under comparable conditions.
Development of Trifluoromethanesulfonic Acid-Immobilized Nitrogen-Doped Carbon-Incarcerated Niobia Nanoparticle Catalysts for Friedel-Crafts Acylation
Yang, Xi,Yasukawa, Tomohiro,Yamashita, Yasuhiro,Kobayashi, Shū
, p. 15800 - 15806 (2021/10/25)
Heterogeneous trifluoromethanesulfonic acid-immobilized nitrogen-doped carbon-incarcerated niobia nanoparticle catalysts (NCI-Nb-TfOH) that show excellent catalytic performance with low niobium loading (1 mol %) in Friedel-Crafts acylation have been developed. These catalysts exhibit higher activity and higher tolerance to catalytic poisons compared with the previously reported TfOH-treated NCI-Ti catalysts, leading to a broader substrate scope. The catalysts were characterized via spectroscopic and microscopic studies.
Well-Dispersed Trifluoromethanesulfonic Acid-Treated Metal Oxide Nanoparticles Immobilized on Nitrogen-Doped Carbon as Catalysts for Friedel–Crafts Acylation
Yang, Xi,Yasukawa, Tomohiro,Maki, Tei,Yamashita, Yasuhiro,Kobayashi, Shū
supporting information, p. 232 - 236 (2020/12/30)
Although strong acid-treated metal oxides are useful heterogeneous superacid catalysts for various organic transformations, they usually have a limited density of acidic sites due to their low surface areas. Herein, heterogeneous trifluoromethanesulfonic acid immobilized nitrogen-doped carbon-incarcerated titanium nanoparticle (NP) catalysts have been developed that are composed of well-dispersed, small Ti NPs (ca 7 nm) that are otherwise difficult to achieve using acid-treated metal oxides. The catalysts showed high activity for Friedel–Crafts acylation with low titanium loading (2 mol%, 1 mg of metal for 1 mmol of substrate). A range of microscopic, spectroscopic and physicochemical studies revealed that the nitrogen-doped carbon immobilized the trifluoromethanesulfonic acid and that the addition of metals further changed the nature of the acidic species and enhanced catalytic activity.
Synthesis and Catalytic Applications of Multinuclear Gold(I)-1,2,3-Triazolylidene Complexes
Rendón-Nava, David,álvarez-Hernández, Alejandro,Mendoza-Espinosa, Daniel
supporting information, p. 840 - 847 (2021/02/26)
A series of mono- to trinuclear gold(I) complexes (1–3) supported by oxo-functionalized 1,2,3-triazolylidenes have been prepared. All new compounds were fully characterized by means of 1H and 13C NMR spectroscopy, elemental analyses, and in the case of complexes 1 and 2 by x-ray diffraction. The catalytic performance of the new triazolylidene gold complexes was tested in several hydroelementation and cyclization processes employing a variety of alkynes as starting materials. According to the overall results, the trinuclear complex 3 displayed the highest catalytic activity in all processes, providing good to excellent yields under mild reaction conditions.
MnO2as a terminal oxidant in Wacker oxidation of homoallyl alcohols and terminal olefins
Fernandes, Rodney A.,Ramakrishna, Gujjula V.,Bethi, Venkati
, p. 6115 - 6125 (2020/10/27)
Efficient and mild reaction conditions for Wacker-type oxidation of terminal olefins of less explored homoallyl alcohols to β-hydroxy-methyl ketones have been developed by using a Pd(ii) catalyst and MnO2 as a co-oxidant. The method involves mild reaction conditions and shows good functional group compatibility along with high regio- and chemoselectivity. While our earlier system of PdCl2/CrO3/HCl produced α,β-unsaturated ketones from homoallyl alcohols, the present method provided orthogonally the β-hydroxy-methyl ketones. No overoxidation or elimination of benzylic and/or β-hydroxy groups was observed. The method could be extended to the oxidation of simple terminal olefins as well, to methyl ketones, displaying its versatility. An application to the regioselective synthesis of gingerol is demonstrated.
Selective monoacylation of mesitylene using hierarchical nanocrystalline ZSM-5 catalyst
Selva Roselin,Selvin, Rosilda
, p. 1315 - 1319 (2020/01/21)
Monoacylated mesitylene is an important precursor used in fine chemical industries In the present work, acylation of mesitylene was carried out using hierarchical ZSM-5 catalyst to prepare 2′,4′,6′-trimethyl acetophenone (monoacylated Mesitylene). The catalyst hierarchical ZSM-5 possessing three generations of micro-, meso-, and macroporosities was fabricated through a dual-template approach using tetrapropylammonium hydroxide (TPAOH) and poly(methyl methacrylate) (PMMA) latex particles as micropore and macropore templates, respectively. The catalyst is well characterized by XRD, FTIR and SEM. The liquid phase reactions were carried out in the temperature range of 30-50 °C. The effect of various parameters such as mole ratio of reactants, catalyst loading, and temperature on the rates of reaction has been investigated. The result shows that the present process gives 100% selective towards the desired product, that is, 2′,4′,6′-trimethyl acetophenone, because hierarchical ZSM-5 allows faster diffusion of the products out of the catalyst provide an important increase in the activity and selectivity.
Manganese complex-catalysed α-alkylation of ketones with secondary alcohols enables the synthesis of β-branched carbonyl compounds
Waiba, Satyadeep,Jana, Sayan K.,Jati, Ayan,Jana, Akash,Maji, Biplab
supporting information, p. 8376 - 8379 (2020/08/13)
Herein, β-branched carbonyl compounds were synthesised via the α-alkylation of ketones with secondary alcohols under "borrowing hydrogen"catalysis. A wide range of secondary alcohols, including various cyclic, acyclic, symmetrical, and unsymmetrical alcohols, have been successfully applied under the developed reaction conditions. A manganese(i) complex bearing a phosphine-free multifunctional ligand catalysed the reaction and produced water as the sole byproduct.
Strongly Lewis Acidic Metal-Organic Frameworks for Continuous Flow Catalysis
Ji, Pengfei,Feng, Xuanyu,Oliveres, Pau,Li, Zhe,Murakami, Akiko,Wang, Cheng,Lin, Wenbin
supporting information, p. 14878 - 14888 (2019/10/02)
The synthesis of highly acidic metal-organic frameworks (MOFs) has attracted significant research interest in recent years. We report here the design of a strongly Lewis acidic MOF, ZrOTf-BTC, through two-step transformation of MOF-808 (Zr-BTC) secondary building units (SBUs). Zr-BTC was first treated with 1 M hydrochloric acid solution to afford ZrOH-BTC by replacing each bridging formate group with a pair of hydroxide and water groups. The resultant ZrOH-BTC was further treated with trimethylsilyl triflate (Me3SiOTf) to afford ZrOTf-BTC by taking advantage of the oxophilicity of the Me3Si group. Electron paramagnetic resonance spectra of Zr-bound superoxide and fluorescence spectra of Zr-bound N-methylacridone provided a quantitative measurement of Lewis acidity of ZrOTf-BTC with an energy splitting (?E) of 0.99 eV between the ?x? and ?y? orbitals, which is competitive to the homogeneous benchmark Sc(OTf)3. ZrOTf-BTC was shown to be a highly active solid Lewis acid catalyst for a broad range of important organic transformations under mild conditions, including Diels-Alder reaction, epoxide ring-opening reaction, Friedel-Crafts acylation, and alkene hydroalkoxylation reaction. The MOF catalyst outperformed Sc(OTf)3 in terms of both catalytic activity and catalyst lifetime. Moreover, we developed a ZrOTf-BTC?SiO2 composite as an efficient solid Lewis acid catalyst for continuous flow catalysis. The Zr centers in ZrOTf-BTC?SiO2 feature identical coordination environment to ZrOTf-BTC based on spectroscopic evidence. ZrOTf-BTC?SiO2 displayed exceptionally high turnover numbers (TONs) of 1700 for Diels-Alder reaction, 2700 for epoxide ring-opening reaction, and 326 for Friedel-Crafts acylation under flow conditions. We have thus created strongly Lewis acidic sites in MOFs via triflation and constructed the MOF?SiO2 composite for continuous flow catalysis of important organic transformations.
