A recyclable bifunctional acid–base organocatalyst with ionic liquid character. The role of site separation and spatial configuration on different condensation reactions

Corma, Avelino; Boronat, Mercedes; Climent, María J.; Iborra, Sara; Montón, Raquel; Sabater, Marı́a J.

doi:10.1039/c1cp21986c

Cited by 13 publications

(6 citation statements)

References 34 publications

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“…67 Promising results obtained using these attractive bifunctional acid-base materials, containing ionic liquids in the framework, predict that in the near future novel multifunctional catalytic materials could be obtained following this approach. 68,69 In fact, stable and recoverable hybrid active catalysts based on metallic nanoparticles captured onto spherical silica particles, using pending urea cross-linked imidazolium moieties, have successfully been used for coupling reactions. 70 Promising hybrid catalysts are also being developed by the deposition of metallic nanoparticles onto the pores of pristine PMOs, which are then used as organic-inorganic supports.…”

Section: Organosiliceous Hybrid Materials Without Structural Order: C...mentioning

confidence: 99%

Catalysis using multifunctional organosiliceous hybrid materials

2013

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Organic-inorganic hybrid materials with different levels of structuration and porous hierarchy and one or several types of active sites in the framework can catalyze multistep chemical processes in a one-pot reactor system following a cascade of reaction events. It will show how the different active sites can act in a synergistic or in a consecutive way following a similar functionality model to biological multisite catalysts. Research on this subject for heterogeneous catalysts is still in the beginning stage and very interesting results can be expected if we are able to successfully combine the properties of organic and inorganic catalysts.

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Section: Organosiliceous Hybrid Materials Without Structural Order: C...mentioning

confidence: 99%

Catalysis using multifunctional organosiliceous hybrid materials

2013

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“…However, for the HPA‐paired analogue [PySaIm] 3 PW, the intensity of the corresponding band at 3444 cm −1 was weakened drastically, which indicates that the presence of PW anions has greatly hindered the formation of the intramolecular hydrogen bonding. Alternatively, the extended intermolecular hydrogen‐bonding networks are generated between IL cations and PW anions27 in addition to the strong electrostatic interaction. This is a reason for the solid nature of [PySaIm] 3 PW.…”

Section: Resultsmentioning

confidence: 99%

Schiff Base Structured Acid–Base Cooperative Dual Sites in an Ionic Solid Catalyst Lead to Efficient Heterogeneous Knoevenagel Condensations

Zhang

Zhao

Leng

et al. 2012

Chemistry A European J

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An acid-base bifunctional ionic solid catalyst [PySaIm](3)PW was synthesized by the anion exchange of the ionic-liquid (IL) precursor 1-(2-salicylaldimine)pyridinium bromide ([PySaIm]Br) with the Keggin-structured sodium phosphotungstate (Na(3) PW). The catalyst was characterized by FTIR, UV/Vis, XRD, SEM, Brunauer-Emmett-Teller (BET) theory, thermogravimetric analysis, (1)H NMR spectroscopy, ESI-MS, elemental analysis, and melting points. Together with various counterparts, [PySaIm](3)PW was evaluated in Knoevenagel condensation under solvent and solvent-free conditions. The Schiff base structure attached to the IL cation of [PySaIm](3)PW involves acidic salicyl hydroxyl and basic imine, and provides a controlled nearby position for the acid-base dual sites. The high melting and insoluble properties of [PySaIm](3)PW are relative to the large volume and high valence of PW anions, as well as the intermolecular hydrogen-bonding networks among inorganic anions and IL cations. The ionic solid catalyst [PySaIm](3)PW leads to heterogeneous Knoevenagel condensations. In solvent-free condensation of benzaldehyde with ethyl cyanoacetate, it exhibits a conversion of 95.8 % and a selectivity of 100 %; the conversion is even much higher than that (78.2 %) with ethanol as a solvent. The solid catalyst has a convenient recoverability with only a slight decrease in conversion following subsequent recyclings. Furthermore, the new catalyst is highly applicable to many substrates of aromatic aldehydes with activated methylene compounds. On the basis of the characterization and reaction results, a unique acid-base cooperative mechanism within a Schiff base structure is proposed and discussed, which thoroughly explains not only the highly efficient catalytic performance of [PySaIm](3)PW, but also the lower activities of various control catalysts.

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“…These hybrids showed high activity as base catalysts for the Knoevenagel catalytic process and can be recycled without activity loss (Gianotti et al 2011;Poli et al 2001). The activity of the basic sites in the hybrid catalysts for condensation reactions can be increased if a mild acid is introduced to the adequate distance of the basic site in the organic component (Boronat et al 2010a,b;Corma et al 2011).…”

Section: (B) Pmos Containing Base Single Sitesmentioning

confidence: 99%

Hybrid organic–inorganic structured materials as single-site heterogeneous catalysts

2012

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Catalyst selectivity is associated with well-defined homogeneous active sites. Transition metal complexes and organocatalysts are highly active and selective in the homogeneous phase, and their heterogenization by incorporating them into inorganic solid materials allows combining their excellent catalytic activity with improved separation, recovering and recycling properties. In this article, we present the structural characteristics and catalytic properties of hybrid organic-inorganic materials in which the molecular catalysts are part of the inorganic structure, emphasizing the possibilities of periodic mesoporous hybrid materials and coordination polymers as single-site solid catalysts.

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A recyclable bifunctional acid–base organocatalyst with ionic liquid character. The role of site separation and spatial configuration on different condensation reactions

Cited by 13 publications

References 34 publications

Catalysis using multifunctional organosiliceous hybrid materials

Catalysis using multifunctional organosiliceous hybrid materials

Schiff Base Structured Acid–Base Cooperative Dual Sites in an Ionic Solid Catalyst Lead to Efficient Heterogeneous Knoevenagel Condensations

Hybrid organic–inorganic structured materials as single-site heterogeneous catalysts

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