Search results for "Bifunctional catalyst"
showing 10 items of 11 documents
Carbon nanotube supported aluminum porphyrin-imidazolium bromide crosslinked copolymer
2022
The increased awareness of the catastrophic consequences caused by the accumulation of greenhouse gases into the atmosphere has generated a large mobilization aimed at CO2 mitigation. Herein, in the spirit of the transformation of a waste as CO2 into value added products, we propose an efficient preparation of two different hybrid systems based on aluminum chloride tetrastyrylporphyrin (TSP-Al-Cl) and 1,4-butanediyl-3,3′-bis-1-vinylimidazolium dibromide copolymerized in the presence (MWCNT-TSP-AlCl-imi) and in absence (TSP-AlCl-imi) of multi-walled carbon nanotubes (MWCNTs) for the CO2 utilization in the synthesis of cyclic carbonates. The so-prepared materials have been thoroughly characte…
ChemInform Abstract: Enantioselective Mannich Reaction of β-Keto Esters with Aromatic and Aliphatic Imines Using a Cooperatively Assisted Bifunctiona…
2015
The title reaction tolerates aliphatic and aromatic substituents on both reaction partners, affording products (III) as a mixture of inseparable diastereomers with low or without any diastereoselectivity.
POSS-Al-porphyrin-imidazolium cross-linked network as catalytic bifunctional platform for the conversion of CO2 with epoxides
2023
Two heterogeneous catalysts were prepared with the aim of following the promising path of CO2 fixation into epoxides. The synthetic procedure involves a radical copolymerization of an octavinylsilsesquioxane as inorganic core building block and tetrastyrylporphyrin aluminum chloride monomer (TSP-AlCl) in presence (POSS-TSP-AlCl-imiBr) or in absence (POSS-TSP-AlCl) of a bis-vinylimidazolium bromide salt (bis-imiBr), in order to investigate if the bifunctional heterogeneous material can display better catalytic performance than the separate species. All the solids were fully characterized and tested in the synthesis of cyclic carbonates starting from CO2 and several epoxides. The synergic coo…
POSS-based 3D functional networks as catalysts for the conversion of carbon dioxide
2023
Oggi lo sviluppo di processi sostenibili è al centro dell'attenzione a causa delle emergenze climatiche. La Chimica Verde, con i suoi dodici principi sviluppati da Paul Anastas, si concentra sullo sviluppo di processi alternativi e più rispettosi dell'ambiente. Questa branca della chimica mostra come concetti quali la prevenzione dei rifiuti, l'uso di materie prime rinnovabili e la catalisi siano di grande importanza per rendere un processo più sostenibile. In questo contesto, l'anidride carbonica (CO2) rappresenta una delle materie prime più abbondanti, non tossiche e rinnovabili. La possibilità di riutilizzare la CO2 e di trasformare questa molecola in prodotti a valore aggiunto come i ca…
Organocatalytic Enantioselective Friedel–Crafts Aminoalkylation of Indoles in the Carbocyclic Ring
2016
The first general catalytic method for the, so far elusive, enantioselective Friedel−Crafts functionalization of indoles in the carbocyclic ring is presented. This transformation contrasts with the usual tendency of these heterocycles to react at the azole ring. For this purpose, the four regioisomeric hydroxy carbocyclic-substituted indoles were reacted with several isatinderived ketimines, using a Cinchona alkaloid-based squaramide, in a low 0.5−5 mol % catalyst loading, as a bifunctional catalyst. This methodology allows the functionalization of indoles in every position of the carbocyclic ring in a regio- and enantioselective fashion, by switching only the position of the hydroxy group …
Enantioselective Mannich reaction of β-keto esters with aromatic and aliphatic imines using a cooperatively assisted bifunctional catalyst
2014
An efficient urea-enhanced thiourea catalyst enables the enantioselective Mannich reaction between β-keto esters and N-Boc-protected imines under mild conditions and minimal catalyst loading (1–3 mol %). Aliphatic and aromatic substituents are tolerated on both reaction partners, affording the products in good enantiomeric purity. The corresponding β-amino ketones can readily be accessed via decarboxylation without loss of enantiomeric purity.
First Evidence of Proline Acting as a Bifunctional Catalyst in the Baylis–Hillman Reaction Between Alkyl Vinyl Ketones and Aryl Aldehydes
2008
Proline in the presence of sodium hydrogen carbonate has been found to be an effective catalyst for the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and aryl aldehydes. Screening of several amine catalysts showed that an ionizable carboxylic function directly linked to the secondary amine catalyst plays an important role in the synthesis of the desired product in good yield. The data obtained has allowed us to suggest, for the first time, that proline, sarcosine, pipecolinic acid and homoproline may act as bifunctional catalysts via a bicyclic enaminolactone species as intermediate. Quantum-mechanical calculations (PM3/COSMO and ab initio 3-21G/COSMO) support this mechanism …
ChemInform Abstract: First Evidence of Proline Acting as a Bifunctional Catalyst in the Baylis-Hillman Reaction Between Alkyl Vinyl Ketones and Aryl …
2008
Proline in the presence of sodium hydrogen carbonate has been found to be an effective catalyst for the Baylis–Hillman reaction between methyl or ethyl vinyl ketone and aryl aldehydes. Screening of several amine catalysts showed that an ionizable carboxylic function directly linked to the secondary amine catalyst plays an important role in the synthesis of the desired product in good yield. The data obtained has allowed us to suggest, for the first time, that proline, sarcosine, pipecolinic acid and homoproline may act as bifunctional catalysts via a bicyclic enaminolactone species as intermediate. Quantum-mechanical calculations (PM3/COSMO and ab initio 3-21G/COSMO) support this mechanism …
Organocatalytic enantioselective aza-Friedel–Crafts reaction of 2-naphthols with benzoxathiazine 2,2-dioxides
2015
An organocatalytic enantioselective aza-Friedel–Crafts addition of 2-naphthols to benzoxathiazine 2,2-dioxides is described using a quinine-derived bifunctional catalyst. The method allows the use of a wide range of aromatic compounds as nucleophiles, including 1-naphthol and sesamol, and benzoxathiazines 2,2-dioxides, expanding the existing state of the art enantioselective synthesis of aminomethylnaphthol derivatives.
ChemInform Abstract: Organocatalytic Enantioselective Aza-Friedel-Crafts Reaction of 2-Naphthols with Benzoxathiazine 2,2-Dioxides.
2015
An organocatalytic enantioselective aza-Friedel–Crafts addition of 2-naphthols to benzoxathiazine 2,2-dioxides is described using a quinine-derived bifunctional catalyst. The method allows the use of a wide range of aromatic compounds as nucleophiles, including 1-naphthol and sesamol, and benzoxathiazines 2,2-dioxides, expanding the existing state of the art enantioselective synthesis of aminomethylnaphthol derivatives.