Search results for "Suzuki reaction"
showing 8 items of 48 documents
A highly selective, Hg2+ triggered hydrogelation: modulation of morphology by chemical stimuli
2014
We report the first Hg2+ selective hydrogelation by 4´-[4-(4- aminophenyl)phenyl]-2,2´:6´,2´´-terpyridine. The gel showed remarkable response towards specific chemical agents such as benzo-18-crown-6 ether and K+ which enabled extensive 10 modulation of the gel morphology. peerReviewed
GREEN CONDITIONS FOR THE SUZUKI REACTIONS BY USING MICROWAVE IRRADIATION AND MODIFIED HALLOYSITE/Pd CATALYST
2014
Halloysite nanotube (HNT) is an emerging biocompatible material with appealing perspective for technological applications, such as in catalysis1 and in pharmaceutical research.2 Halloysite is a double-layered aluminosilicate mineral that has a predominantly hollow tubular structure. The functionalization of HNTs is a good strategy to introduce an organic moiety onto the external surface and, therefore, to obtain innovative catalyst supports.3 We have modified the external surface of halloysite nanotube with octylimidazolium moieties (HNT-IL) by microwave irradiation in solvent-free conditions and we have have employed this material as support catalyst of Pd nanoparticles. The new HNT/Pd cat…
SYNTHESIS AND EVALUATION OF CATALYTIC ACTIVITY IN WATER AND MICROWAVE IRRADIATION OF A NEW SUPPORT BASED ON HNT TRIAZOLIUM SALTS
2014
In the last years SILLP (supported ionic liquid-like phase)-based materials prepared by covalent attachment have been synthesized [1]. Recently, we have synthesized a palladium-based catalytic system using halloysite nanotubes modified with octylimidazolium moieties and we have tested it in the Suzuki cross-coupling reaction under traditional heating, microwave irradiation and a very small amount of Pd catalyst [2,3]. It is known that support based on triazole motif showed superior activity to the analogous imidazole molecules [4] so, we have focused our attention to develop a new SILLP system with triazolium moiety. Herein we report the synthesis of an original Pd-dicationic triazolium sup…
Cross-Linked Imidazolium Salts as Scavengers for Palladium.
2014
Five imidazolium-based materials have been synthesised and used for the first time as palladium scavengers. Radical reactions of suitable bis-vinylimidazolium salts led to a series of insoluble materials through homo-polymerisation, immobilisation with a 3-mercaptopropyl-modified silica gel or co-polymerisation with ethylene glycol dimethylacrylate. These materials were screened as palladium scavengers with a set of palladium(0) and palladium(II) compounds in different solvents and at different starting amounts of palladium. In many cases, residual amounts of palladium were lower than 5 ppm, as requested for the manufacture of active pharmaceutical ingredients and fine chemicals. The applic…
First Synthesis of β-Keto Sulfoxides by a Palladium-Catalyzed Carbonylative Suzuki Reaction
2005
[reaction: see text] An unprecedented palladium-catalyzed three-component cross-coupling reaction between alpha-bromo sulfoxide, carbon monoxide, and aromatic boronic acids provides a new and efficient approach to the synthesis of beta-ketosulfoxides. The reaction takes place under mild conditions with a wide range of variously substituted aryl and heteroaryl boronic acids. The carbonylative cross-coupling reaction is strongly favored over competing direct cross-coupling and homocoupling processes, except with boronic acids carrying strong electron-withdrawing substituents.
Unprecedented Palladium-Catalyzed Cross-Coupling Reaction of α-Bromo Sulfoxides with Boronic Acids
2003
[reaction: see text] A new Suzuki-type palladium-catalyzed reaction of boronic acids with alpha-bromo sulfoxides has been developed using a protocol similar to the well-documented reaction of boronic acids with aryl halides. Both cross-coupling and homocoupling processes were observed. The best yields in cross-coupling products were obtained when the presence of oxygen was carefully excluded using degassed solvents. The oxidative addition palladium complex intermediate could be isolated and characterized by X-ray single-crystal diffraction.
Design of PNIPAAM covalently grafted on halloysite nanotubes as a support for metal-based catalysts
2016
A thermo-responsive polymer such as poly(N-isopropylacrylamide) (PNIPAAM) was covalently grafted on the external surface of halloysite nanotubes (HNTs) by means of microwave irradiation. This nanomaterial was used as a support and stabilizer for palladium nanoparticles. The obtained HNT–PNIPAAM/PdNPs was characterized by means of TGA, SEM, EDS and TEM analyses. The palladium content of the catalyst was estimated to be 0.4 wt%. The stability of the catalytic material at different temperatures (below and above the PNIPAAM lower critical solution temperature) was tested in the Suzuki reaction under microwave irradiation. In addition, TEM analysis after five consecutive runs was performed. The …
Green conditions for the Suzuki reaction using microwave irradiation and a new HNT- supported ionic liquid-like phase (HNT-SILLP) catalyst
2014
A new catalytic system based on modified halloysite nanotubes was employed in the Suzuki reaction under microwave irradi- ation. A set of solvents, times and bases was screened and the best experimental conditions were obtained when the reactions were carried out for 10 min in water–ethanol at 120 °C in presence of K2CO3 as base. Good recyclability was observed. The new catalytic system was employed using either 1 mol% or 0.1 mol%. The palladium catalyst displayed good activity, allowing the synthesis of several biphenyl compounds in high yield working with only 0.1 mol% palladium loading. The application of mi- crowave irradiation decreased the reaction time and also improved conversion wi…