Synthesis of bis-spiro piperidines using nano γ-alumina supported Sb(v) under ultrasonic irradiation at room temperature conditions

Group VA metalloid ion Lewis acids, Sb(v) was identified as a highly potent catalyst for the one-pot three-component synthesis of bis-spiro piperidine derivatives. The reaction was performed using amines, formaldehyde, and dimedone under ultrasonic irradiation at room temperature. The strong acidic property of the nano γ-alumina supported antimony(v) chloride plays a key role in accelerating the rate of the reaction and initiates the reaction smoothly. The heterogeneous nanocatalyst was fully characterized by FT-IR spectroscopy, XRD, EDS, TGA, FESEM, TEM, and BET techniques. Also, the structures of the prepared compounds were characterized by ¹H NMR and FT-IR spectroscopies.

Heterogeneous catalysis for the tandem cyclisation of unsaturated alcohols

A methodology for the tandem cycloisomerisation of doubly unsaturated alcohols using Amberlyst-15 was developed.

Cage and linear structured polysiloxane/epoxy hybrids for coatings: Surface property and film permeability

Three polysiloxane/epoxy hybrids obtained by evolving cage- or linear-structured polysiloxane into poly glycidyl methacrylate (PGMA) matrix are compared used as coatings. One is the cage-structured hybrid of P(GMA/MA-POSS) copolymer obtained by GMA and methacrylisobutyl polyhedral oligomeric silsesquioxane (MA-POSS) via free radical polymerization, the other two are PGMA/NH₂-POSS and PGMA/NH₂-PDMS hybrids by cage-structured aminopropyllsobutyl POSS (NH₂-POSS) or linear-structured diamino terminated poly(dimethylsiloxane) (NH₂-PDMS) to cure PGMA. The effect of MA-POSS, NH₂-POSS and NH₂-PDMS on polysiloxane/epoxy hybrid films is characterized according to their surface morphology, transparency, permeability, adhesive strength and thermo-mechanical properties. Due to caged POSS tending to agglomerate onto the film surface, P(GMA/MA-POSS) and PGMA/NH₂-POSS films exhibit much more heterogeneous surfaces than PGMA/NH₂-PDMS film, but the well-compatibility between epoxy matrix and MA-POSS has provided P(GMA/MA-POSS) film with much higher transmittance (98%) than PGMA/NH₂-POSS film (24%), PGMA/NH₂-PDMS film (27%) and traditional epoxy resin film (5%). The introduction of polysiloxane into epoxy matrix is confirmed to create hybrids with strong adhesive strength (526-1113N) and high thermos-stability (T_g=262-282°C), especially the cage-structured P(GMA/MA-POSS) hybrid (1113N and 282°C), but the flexible PDMS improves PGMA/NH₂-PDMS hybrid with much higher storage modulus (519MPa) than PGMA/NH₂-POSS (271MPa), which suggests that PDMS is advantage in improving the film stiffness than POSS cages. However, cage-structured P(GMA/MA-POSS) and PGMA/NH₂-POSS indicate higher permeability than PGMA/NH₂-PDMS and traditional epoxy resin. Comparatively, the cage-structured P(GMA/MA-POSS) hybrid is the best coating in transparency, permeability, adhesive strength and thermostability, but linear-structured PGMA/NH₂-PDMS hybrid behaviors the best coating in mechanical property.

Efficient nickel(ii) naringenin-oxime complex catalyzed Mizoroki–Heck cross-coupling reaction in the presence of hydrazine hydrate

A novel nickel(ii) naringenin-oxime complex was designed, synthesized and characterized.

Diazoresin modified monodisperse porous poly(glycidylmethacrylate-co-divinylbenzene) microspheres as the stationary phase for high performance liquid chromatography

Diazoresin modified monodisperse porous PGMA–DVB microspheres were used as a novel tool for the separation and purification of the N-vinyl-1,2,4-triazole product from its by-product was developed.

In situ generated and stabilized Pd nanoparticles by N2,N4,N6-tridodecyl-1,3,5-triazine-2,4,6-triamine (TDTAT) as a reactive and efficient catalyst for the Suzuki–Miyaura reaction in water

The Suzuki–Miyaura coupling reaction was efficiently catalyzed by the in situ generated and stabilized Pd nanoparticles employing TDTAT in water.

Pd(0) encapsulated nanocatalysts as superior catalytic systems for Pd-catalyzed organic transformations

In the last decade, Pd(0) nanoparticles have attracted increasing attention due to their outstanding utility as nanocatalysts in a wide variety of key chemical reactions.

Linkage of the PAMAM type dendrimer with the gel type resin based on glycidyl methacrylate terpolymer as a method of preparation of the polymer support for the recyclable palladium catalyst for Suzuki–Miyaura cross-coupling reactions

Poly(amidoamine) PAMAM type hyperbranched systems were immobilized on an epoxy functionalized polymer based on glycidyl methacrylate (the GMA resin).

Bridging homogeneous and heterogeneous catalysis with CAN·SiO2as a solid catalyst for four-component reactions for the synthesis of tetrasubstituted pyrroles

The attractive features of this methodology are newer and greener methods, simple procedures, reusability and high efficiency of the catalyst and easy workability.

Molybdate sulfuric acid (MSA): an efficient solid acid catalyst for the synthesis of diversely functionalized fused imidazo[1,2-a]pyrimidines under solvent-free conditions

Synthesis of imidazo[1,2-a]pyrimidines has been accomplished for the first time under solvent-free conditions using molybdate sulfuric acid (MSA) as a heterogeneous catalyst. The present protocol is operationally simple, green and offers several advantages over the existing methods.

Suzuki coupling reactions in neat water as the solvent: where in the biphasic reaction mixture do the catalytic reaction steps occur?

Many reports on water-compatible palladium catalysts have appeared in the recent literature. For hydrophobic substrates, mixtures with pure water are biphasic, and it is widely not regarded that the elusive locality of the catalytic process (in water, the organic layer, or at the phase boundary) has an important impact on the mechanism and efficiency of the reaction. In the present work, for the first time systematic variation of reaction parameters has been performed for Suzuki coupling experiments with chloro- and bromoarenes in pure water. The investigations are not only aimed at the factors influencing the catalytic activity, but also at the effects that may occur particularly in water/organic biphasic media, and on the question as to in which of the two liquid phases the reaction takes place. These investigations have revealed that dilution of the base (in the aqueous layer) and the Pd species (in the organic layer) are detrimental to the reaction, and that phase-transfer processes play a major role in the overall mechanism. A series of experiments with variation of parameters like precatalyst hydrophilicity, organic and water phase volume, additives, stirring rate, base concentration, and so forth, indicate that for the systems under study the reaction occurs in the organic layer. The water phase needs to be present to dissolve and provide polar reactants, and re-absorb side products. The results encourage to pay more regard to the question of phase locality of coupling reactions in water in general.