In situ cross-linked chitosan Cu(I) or Pd(II) complexes as a versatile, eco-friendly recyclable solid catalyst

Martina, Katia; Leonhardt, Silke E. S.; Ondruschka, Bernd; Curini, Massimo; Binello, Arianna; Cravotto, Giancarlo

doi:10.1016/j.molcata.2010.10.024

Cited by 86 publications

(49 citation statements)

References 31 publications

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“…In addition to classical palladium salts, we used a palladium-loaded cross-linked chitosan, [38] which gave the best results using both 3- [a] Reaction conditions: see Table 2.…”

Section: Scheme 2 Suzuki Cross-coupling Reaction In Glycerolmentioning

confidence: 99%

Efficient Synthetic Protocols in Glycerol under Heterogeneous Catalysis

et al. 2011

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The massive increase in glycerol production from the transesterification of vegetable oils has stimulated a large effort to find novel uses for this compound. Hence, the use of glycerol as a solvent for organic synthesis has drawn particular interest. Drawbacks of this green and renewable solvent are a low solubility of highly hydrophobic molecules and a high viscosity, which often requires the use of a fluidifying co-solvent. These limitations can be easily overcome by performing reactions under high-intensity ultrasound and microwaves in a standalone or combined manner. These non-conventional techniques facilitate and widen the use of glycerol as a solvent in organic synthesis. Glycerol allows excellent acoustic cavitation even at high temperatures (70-100 °C), which is otherwise negligible in water.Herein, we describe three different types of applications: 1) the catalytic transfer hydrogenation of benzaldehyde to benzyl alcohol in which glycerol plays the dual role of the solvent and hydrogen donor ; 2) the palladium-catalyzed Suzuki cross-coupling; and (3) the Barbier reaction. In all cases glycerol proved to be a greener, less expensive, and safer alter-native to the classic volatile organic solvents.

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“…In addition to classical palladium salts, we used a palladium-loaded cross-linked chitosan, [38] which gave the best results using both 3- [a] Reaction conditions: see Table 2.…”

Section: Scheme 2 Suzuki Cross-coupling Reaction In Glycerolmentioning

confidence: 99%

Efficient Synthetic Protocols in Glycerol under Heterogeneous Catalysis

et al. 2011

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“…To increase the affinity of Pd onto chitosan, Martina et al [37] incorporated ultrasound to assist the cross-link of Pd(II) ions onto chitosan by interacting with hexamethylene diisocyanate. The sonication from ultrasound helped the removal of air bubbles in the bulk of chitosan derivatives and the breakdown of aggregated nanospheres [38].…”

Section: Metal Catalystsmentioning

confidence: 99%

Chitosan as a Natural Polymer for Heterogeneous Catalysts Support: A Short Review on Its Applications

2015

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Chitosan, a bio-based polymer which has similar characteristics to those of cellulose, exhibits cationic behavior in acidic solutions and strong affinity for metals ions. Thus, it has received increased attention for the preparation of heterogeneous catalysts. Recent studies demonstrated that chitosan-based catalysts had high sorption capacities, chelating activities, stability and versatility, which could be potentially applied as green reactants in various scientific and engineering applications. This study intends to review the recent development of chitosan-based catalysts, particularly in the aspects of the main mechanisms for preparing the materials and their applications in environmental green chemistry. Studies on the preparation of catalyst nanoparticles/nanospheres supported on chitosan were also reviewed.

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“…An alternative solid catalyst preparation method can be found in the simple physical mixture of the metal salt and the polyurethane-bridged CDs in a planetary ball mill. A similar approach has recently been described for chitosan based Pd-catalysts in which the simple physical mixture [12] was compared to metal-loaded cross-linked chitosan [13] . In addition, when used in MW-assisted reactions, this catalyst is strongly activated by ball milling [14] , which allows the solid-state Suzuki cross-coupling of poorly reactive (hetero) aryl chlorides with phenylboronic acid to be performed [15] .…”

Section: Introductionmentioning

confidence: 99%

“…Simple metal salts, metals supported on active charcoal or metal-loaded polymers have been effi ciently used under ultrasound [20] and MW irradiation [12,13] , and even under simultaneous irradiation [21 -23] , which tends to give better results. Although high turnover numbers (TONs) have been attained using heterogeneous catalysts coupled with sophisticated recycling strategies, it would be enormously simpler to use catalysts that are effective at such low levels that, in principle, they may not need to be recovered and recycled.…”

Section: Introductionmentioning

confidence: 99%

A green approach to heterogeneous catalysis using ligand-free, metal-loaded cross-linked cyclodextrins

Cravotto

Gaudino

Tagliapietra

et al. 2012

Green Processing and Synthesis

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In this work, we describe the application of a new series of solid cross-linked cyclodextrin ( α -, β -, and γ -CD) based catalysts that are obtained by reticulation with hexamethylene diisocyanate (HDI) in solutions containing Pd (II) or Cu (I) cations. Diisocyanates are effi cient cross-linking agents for CDs because of their high reactivity towards hydroxyl groups. Metal content in the polyurethane-bridged CD polymers has been analyzed using ICP-MS. Pd (II) based catalysts have been successfully used in C-C couplings (Heck and Suzuki reactions), and a Cu (I) based system has been used in alkyne/ azide [3 + 2] cycloadditions. Because metal leaching is negligible, which allows it to be recycled, and preparation is facile, this protocol is truly sustainable. As confi rmed by ICP-MS analysis, the crude products do not require further purifi cation for metal contamination. This versatile catalyst, due to its polar structure, is particularly suitable for microwave (MW)-assisted reactions that, in this study, gave the best yields in shorter reaction times. Due to their polar structure, both native CDs and cross-linked derivatives are very sensitive to dielectric heating; this effect is enhanced by the embedded cations. The design of sustainable synthetic protocols can be effi ciently accomplished using a multi-faceted strategy that combines innovative solid catalysts and suitable enabling technologies.

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In situ cross-linked chitosan Cu(I) or Pd(II) complexes as a versatile, eco-friendly recyclable solid catalyst

Cited by 86 publications

References 31 publications

Efficient Synthetic Protocols in Glycerol under Heterogeneous Catalysis

Efficient Synthetic Protocols in Glycerol under Heterogeneous Catalysis

Chitosan as a Natural Polymer for Heterogeneous Catalysts Support: A Short Review on Its Applications

A green approach to heterogeneous catalysis using ligand-free, metal-loaded cross-linked cyclodextrins

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