Cross‐Linked Polyamine from Imidazolium‐Based Materials: A Simple Route to Useful Catalytic Materials

Abstract

Cross‐linked polyamine‐based materials were easily prepared by reduction of the corresponding cross‐linked imidazolium‐based materials with sodium borohydride in hot ethanol. Overall, the synthetic procedure is based on the polymerization of a suitable bis‐vinylimidazolium salt with or without a suitable support, such as silica or silica‐coated magnetic nanoparticles (γ‐Fe2O3@SiO2), followed by reduction. This simple approach allows the synthesis of materials based on a network of secondary and tertiary amines. Materials were characterized by 13C cross‐polarization magic angle spinning NMR (13C CPMAS NMR), proton spin‐lattice relaxation times in the rotating frame (T1ρH) and thermogravimetric analysis (TGA). Cross‐linked polyamine‐based materials were used as recoverable catalyst for Knoevenagel reaction. High yields of the condensation products were obtained and up to 11 cycles were carried out.

Is a Catalyst Always Needed? The Case of the Knoevenagel Reaction with Malononitrile

“…[23] Even us reported a cross-linked polyamine-based material 9 that was used in two examples. The less reactive 4-methoxy derivative was obtained in 99 % yield in 1 h (entry 12) [24] whereas after the same time the non-catalysed reaction gave the product in 85 % yield in EtOH/H 2 O at 75 °C. [12] The use of other solvents can be also questionable.…”

Straightforward preparation of highly loaded MWCNT–polyamine hybrids and their application in catalysis

“…In another study we showed that it was possible to easily obtain cross-linked polyamines, containing secondary and tertiary amines, by means of the reduction of the corresponding cross-linked imidazolium-based material with sodium borohydride. 83 Given the extremely high versatility of aminofunctionalised carbon-based materials, and in the context of the current interest aroused by the production of heterogeneous base catalysts, which can nd application in the catalysis of some relevant C-C bond forming reactions such as Knoevenagel condensation and Henry reaction, [84][85][86] herein we propose a new method for obtaining highly loaded cross-linked polyamine-MWCNT materials through the reduction of the corresponding easily accessible cross-linked polyimidazolium salt-MWCNT hybrids. More in detail, one of the prepared materials was not only tested as a heterogeneous base catalyst in the abovementioned Knoevenagel and Henry reactions, but its use in two examples concerning a sequential one-pot approach involving two consecutive reactions, namely Knoevenagel and Michael reactions, is also reported.…”

Palladium Acetate and Pd Nanoparticles Loaded Hexamethylenetetramine Anchored Magnetically Retrievable Assemblies for Catalyzing Mizoroki‐Heck Type Mono and Gem‐Dicoupling Reactions

“…However, the kinetics and catalytic activity of the catalysts immobilized in bulk heterogeneous matrices are the bottlenecks in their wide range uses unlike homogeneous catalysts. The intermediates of the homogeneous and heterogeneous catalysts are the magnetic retrievable nanocatalysts which possess high surface area and can be separated from the solvent using the external magnetic field . In this regard, one of the major challenges associated with catalysis chemistry is to anchor an efficient and reusable moiety on the magnetic nanoparticles (NPs) that can not only preferentially bind to Pd but also provides stability for the successive recycling.…”