Search results for "Catalysis"

Supported ionic liquids. New recyclable materials for L-proline-catalyzed aldol reaction

The effect of the cation p-surface area on the 3D organization and catalytic ability of imidazolium-based ionic liquids

2011

The dichotomic nature of ionic liquids (ILs, simple solvents or supramolecular fluids) induced us to carry out a structural investigation of some mono-and dicationic ionic liquids using 1D and 2D NMR, resonance light scattering, and UV/Vis spectroscopy. Ionic liquids with different cation π-surface areas were used, namely [bmim][NTf2], [Bzmim][NTf 2], [Bzbim][NTf2], [p-Xyl-(bim)2][NTf 2]2, and [m-Xyl-(bim)2][NTf2] 2 [bmim = 1-butyl-3-methylimidazolium, Bzmim = 1-benzyl-3- methylimidazolium, Bzbim = 1-benzyl-3-butylimidazolium, NTf2 = bis(trifluoromethansulfonyl)imide]. In order to verify to what extent the structural investigation, coupled with the determination of solvent parameters, could…

Ionic Liquids as Homogeneous Catalysts for Glycerol Oligomerization

2022

Ionic liquids (ILs) were used for the first time as catalysts for the glycerin condensation reaction. A series of imidazolium and ammonium ionic liquids differing in the length of the alkyl substituent (C2, C12, and C14) and the type of anion (Br−, CH3COO−, and NaHPO4−) were synthesized using a typical two-step method. The structure of the obtained ILs was confirmed by nuclear magnetic resonance 13C NMR, and their base power was determined on the basis of the Hammett function. The oligomerization of glycerin with the participation of the obtained ionic liquids and, for comparison, in the presence of a homogeneous basic catalyst Na2CO3, was carried out for 3 h at 180 °C, under a pressure of …

Eco-friendly cavity-containing iron oxides prepared by mild routes as very efficient catalysts for the total oxidation of VOCs

2018

Iron oxides (FeOx) are non-toxic, non-expensive and environmentally friendly compounds, which makes them good candidates for many industrial applications, among them catalysis. In the present article five catalysts based on FeOx were synthesized by mild routes: hydrothermal in subcritical and supercritical conditions (Fe-HT, Few200, Few450) and solvothermal (Fe-ST1 and Fe-ST2). The catalytic activity of these catalysts was studied for the total oxidation of toluene using very demanding conditions with high space velocities and including water and CO2 in the feed. The samples were characterized by X-ray diffraction (XRD), scanning and high-resolution transmission electron microscopy (SEM and…

Experimental Confirmation of a Topological Isomer of the Ubiquitous Au25(SR)18 Cluster in the Gas Phase

2021

High-resolution electrospray ionization ion mobility mass spectrometry has revealed a gas-phase isomer of the ubiquitous, extremely well-studied Au25(SR)18 cluster both in anionic and cationic form. The relative abundance of the isomeric structures can be controlled by in-source activation. The measured collision cross section of the new isomer agrees extremely well with a recent theoretical prediction (Matus, M. F.; et al. Chem. Commun. 2020, 56, 8087) corresponding to a Au25(SR)18– isomer that is energetically close and topologically connected to the known ground-state structure via a simple rotation of the gold core without breaking any Au–S bonds. The results imply that the structural d…

Charge-Assisted Halogen Bonding in an Ionic Cavity of a Coordination Cage Based on a Copper(I) Iodide Cluster.

2023

The design of molecular containers capable of selective binding of specific guest molecules presents an interesting synthetic challenge in supramolecular chemistry. Here, we report the synthesis and structure of a coordination cage assembled from Cu3I4– clusters and tripodal cationic N-donor ligands. Owing to the localized permanent charges in the ligand core the cage binds iodide anions in specific regions within the cage by ionic interactions. This allows the selective binding of bromomethanes as secondary guest species within cage promoted by halogen bonding, which was confirmed by single crystal X-ray diffraction. peerReviewed

Effect of different co-solvents on biodiesel production from various low-cost feedstocks using Sr–Al double oxides

2020

The main objective of the present paper comprises the investigation of biodiesel production from low-cost feedstock such as lard oil and waste cooking oil (WCO) using Sr-Al double oxides. Nanocatalyst was characterised FTIR, XRD, SEM, TEM, BET and XPS. The Sr:Al with 3:1 molar ratio showed the best catalytic activity in the conversion of both oils to fatty acid methyl ester. The effect of acetone and tetrahydrofuran (THF) as a co-solvent for transesterification were compared and the best result was obtained with 5 % THF. The mutual effect of the nanocatalyst and co-solvent on biodiesel production was investigated. The characterisation of biodiesel synthesised from lard oil and WCO was perfo…

Dioxidomolybdenum(VI) and –tungsten(VI) complexes with tetradentate amino bisphenolates as catalysts for epoxidation

2017

Sixteen molybdenum and tungsten complexes with tripodal or linear tetradentate amino bisphenol ligands were studied as catalysts for the epoxidation of cis-cyclooctene, 1-octene, styrene, limonene and α-terpineol. These complexes can be divided into different categories upon key features, i.e. central metal (Mo versus W), side-arm donor (O versus N), hybridization of the N-donor (pyridine versus amine), ligand geometry (tripodal versus linear diamine) and sterical hindrance (Me versus tert-Bu substituents in the phenol part). All complexes can catalyse selectively the epoxidation of cis-cyclooctene by tert-butylhydroperoxide whereas the activities and selectivities towards other olefins (1-…

Stereoselective Synthesis of Spiro-Decalin Oxindole Derivatives via Sequential Organocatalytic Michael-Domino Michael/Aldol Reaction.

2022

A highly stereoselective procedure for the synthesis of spiro-polycyclic oxindoles bearing five contiguous stereogenic centers including two tetrasubstituted carbons has been developed. Under sequential organocatalysis performed by a pyrrolidine-based organocatalyst and DBU, a highly atom-economical Michael–domino Michael/aldol reaction sequence was optimized, yielding variously functionalized spiro-decalin oxindoles with excellent stereoselectivity (>99:1 dr, up to 92% ee). peerReviewed

Cyclic Sulfoximine and Sulfonimidamide Derivatives by Copper‐Catalyzed Cross‐Coupling Reactions with Elemental Sulfur

2023

Copper-catalyzed cross-coupling reactions of α-bromoaryl NH-sulfoximines with elemental sulfur lead to benzo[d][1,3,2]dithiazole-1-oxides, which represent a new class of three-dimensional heterocycles. The reactions proceed under mild conditions showing good functional group and heterocycle tolerance. By imination/oxidation, the initial cross-coupling products can be converted to unprecedented cyclic sulfonimidamides derivatives. Furthermore, a seven-membered heterocycle was obtained by a ruthenium-catalyzed ring-expansion with ethyl propiolate. peerReviewed