1746-11-8Relevant articles and documents
Enhanced reactivity in OH/NH/π polyfunctional systems through coupled proton/electron transfer in the excited state: The photocyclisation of 2-allyl-3-aminophenol
Leo, Edgar A.,Tormos, Rosa,Miranda, Miguel A.
, p. 1203 - 1205 (2005)
The photocyclisation rate of 2-allyl-3-(or 5-)aminophenols (1, 4 and 8) is dramatically enhanced, when compared with reference compounds, as a consequence of a coupled proton/electron transfer process. The Royal Society of Chemistry 2005.
Intramolecular hydroalkoxylation of non-activated C=C bonds catalysed by zeolites: An experimental and theoretical study
Perez-Mayoral, Elena,Matos, Ines,Nachtigall, Petr,Polozij, Miroslav,Fonseca, Isabel,Vitvarova-Prochazkova, Dana,Cejka, Jiri
, p. 1021 - 1030 (2013)
The high activity and selectivity of zeolites in the cyclisation of unsaturated alcohols is reported for the first time; the details of a reaction mechanism based on quantum chemical calculations are also provided. The high efficiency of zeolites MFI, BEA and FAU in the cyclisation of unsaturated alcohols (cis-decen-1-ol, 6-methylhept-5-en-2-ol and 2-allylphenol) to afford oxygen-containing heterocyclic rings is demonstrated. The best catalytic performance is found for zeolites with the optimum concentration of Bronsted acid sites (ca. 0.2 mmol g-1) and the minimum number of Lewis acid sites. It is proposed that the efficiency of the catalysts is reduced by the existence of the so-called dual site, at which a molecule of unsaturated alcohol can simultaneously interact with two acid sites (an OH group with one and the double bond with the other Bronsted site), which increases the interaction strength. The formation of such adsorption complexes leads to a decrease in the catalyst activity because of (i) an increase in the reaction barrier, (ii) an unfavourable conformation and (iii) diffusion limitations. A new procedure for the preparation of tetrahydrofurans and pyrans over zeolite catalysts provides important oxygen-containing heterocycles with numerous applications. The zeolite fantastic: The high efficiency of zeolites MFI, BEA and FAU in the cyclisation of unsaturated alcohols to afford oxygen-containing heterocyclic rings is demonstrated. It is proposed that the efficiency of the catalysts depends on the existence of the so-called dual site, at which a molecule of an unsaturated alcohol can simultaneously interact with two acid sites. Copyright
Intramolecular cyclization of phenol derivatives with C{double bond, long}C double bond in a side chain
Ito, Yoshihiko,Kato, Risa,Hamashima, Kentaro,Kataoka, Yohei,Oe, Yohei,Ohta, Tetsuo,Furukawa, Isao
, p. 691 - 697 (2007)
Intramolecular cyclization of phenol derivatives with C{double bond, long}C double bond on a side chain was examined using copper and silver catalyst. For example, 2-allylphenol (1a) was converted to 2,3-dihydro-2-methylbenzofuran (2a) in 70% yield using Cu(OTf)2 or in 90% yield using AgClO4. This catalysis was applied to cyclization of 2-allylphenol derivatives, 2-(3-butenyl)phenol, benzoic acids with C{double bond, long}C double bond, 2-allyl-N-tosylaniline, and 2-(3-butenyloxy)phenol. Furthermore, allyl phenyl ether was converted to 2a via Claisen rearrangement and cyclization.
Aluminium(III) trifluoromethanesulfonate as an efficient catalyst for the intramolecular hydroalkoxylation of unactivated olefins: Experimental and theoretical approaches
Coulombel, Lydie,Rajzmann, Michel,Pons, Jean-Marc,Olivero, Sandra,Dunach, Elisabet
, p. 6356 - 6365 (2006)
The Al(OTf)3-catalyzed cycloisomerization of unactivated unsaturated alcohols was studied from experimental and theoretical points of view. A series of cyclic ethers was obtained in excellent yields and regioselectivities. This catalyst system provides one of the most straightforward routes to cyclic ethers with Markovnikov-type regioselectivity under mild conditions. Theoretical and NMR studies were carried out in order to better determine the mechanism of this reaction. The NMR studies were in agreement with preferential complexation of Al(OTf)3 to the oxygen atom of the unsaturated alcohol, but did not exclude complexation to the double bond of the alcohol. Theoretical calculations indicated strong acidification of the hydroxyl proton when Al(OTf)3 was complexed to the alcohol oxygen atom. A plausible catalytic cycle for the Al(OTf)3-catalyzed intramolecular hydroalkoxylation of unactivated olefins is proposed.
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Karakhanov et al.
, (1975)
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STRONGLY LEWIS ACIDIC METAL-ORGANIC FRAMEWORKS FOR CONTINUOUS FLOW CATALYSIS
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Paragraph 0230-0233; 0239; 0255, (2021/02/26)
Lewis acidic metal-organic framework (MOF) materials comprising triflate-coordinated metal nodes are described. The materials can be used as heterogenous catalysts in a wide range of organic group transformations, including Diels-Alder reactions, epoxide-ring opening reactions, Friedel-Crafts acylation reactions and alkene hydroalkoxylation reactions. The MOFs can also be prepared with metallated organic bridging ligands to provide heterogenous catalysts for tandem reactions and/or prepared as composites with support particles for use in columns of continuous flow reactor systems. Methods of preparing and using the MOF materials and their composites are also described.
Selective Hydrogenation of Benzofurans Using Ruthenium Nanoparticles in Lewis Acid-Modified Ruthenium-Supported Ionic Liquid Phases
Bordet, Alexis,El Sayed, Sami,Hetaba, Walid,Leitner, Walter,Luska, Kylie L.,Weidenthaler, Claudia
, p. 2124 - 2130 (2020/02/11)
Ruthenium nanoparticles immobilized on a Lewis-acid-functionalized supported ionic liquid phase (Ru?SILP-LA) act as effective catalysts for the selective hydrogenation of benzofuran derivatives to dihydrobenzofurans. The individual components (nanoparticles, chlorozincate-based Lewis-acid, ionic liquid, support) of the catalytic system are assembled using a molecular approach to bring metal and acid sites in close contact on the support material, allowing the hydrogenation of O-containing heteroaromatic rings while keeping the aromaticity of C6-rings intact. The chlorozincate species were identified to be predominantly [ZnCl4]2- anions using X-ray photoelectron spectroscopy and are in close interaction with the metal nanoparticles. The Ru?SILP-[ZnCl4]2- catalyst exhibited high activity, selectivity, and stability for the catalytic hydrogenation of a variety of substituted benzofurans, providing easy access to biologically relevant dihydrobenzofuran motifs under continuous flow conditions.
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.
