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In this work, for the first time, naphthalene (NA)-based polymers were synthesized by one-stage Friedel-Crafts crosslinking. The influence of NA functionalization by -OH, -SO 3 H, and -NO 2 groups on the polymers' porosity and distribution of the catalytically active phase (Pd) was studied. Synthesized catalytic systems containing 1 wt.% of Pd either in the form of Pd(II) species or Pd(0) nanoparticles supported on NA-based polymers were tested in a model reaction of Suzuki cross-coupling between 4-bromoanisole and phenylboronic acid under mild reaction conditions (60 °C, ethanol-water mixture as a solvent). These novel catalysts demonstrated high efficiency with more than 95% of 4-bromoanisole conversion and high selectivity (>97%) for the target 4-methoxybiphenyl.

During the last decades, palladium nanoparticles (Pd(0) NPs) and Pd(II) compounds were shown to be attractive catalysts for fine organic synthesis. Nanostructured Pd(0) or Pd(II) catalysts have a relatively low environmental impact, but, at the same time, they are indispensable for such processes as Suzuki cross-coupling. This paper describes the preparation of Pd(0) or Pd(II) supported/embedded in hyper-cross-linked polystyrene (HPS) and compares their activity in Suzuki cross-coupling between phenylboronic acid and 4-bromoanisole. Obviously, the palladium charge (Pd(0) ↔ Pd(II)) changes continuously during the reaction catalytic cycle. It would seem that the use of the starting palladium in the form of Pd(0) or Pd(II) should not affect the reaction's kinetic laws for both catalysts, but their special individuality is manifested between them. Nanoparticulate Pd(0) catalysts are stable during the reaction. In contrast, catalysts based on Pd(II) are extremely active in the initial period of the reaction, but then the "hot form" of the catalyst is rapidly converted into the form of Pd(0), whose activity is identical to that of the preliminarily reduced catalyst. This work discusses the possible nature of this phenomenon. A mathematical model for Suzuki cross-coupling reaction was suggested that was able to adequately describe experimental data. The level of reliability (R2) of the correlation between the experimental and calculated data was R2 = 0.97–0.99. [ABSTRACT FROM AUTHOR]

Alkane production from fatty acids and their derivatives can be considered one of the most‐studied processes. Such reactions as hydrogenation, hydrodeoxygenation, decarboxylation, and decarbonylation are the main routes for this process. The reaction pathway depends on the nature of the catalyst, the presence of hydrogen, and the hydrogen source. In this work, a mixture of unsaturated fatty acids (oleic and linoleic acids) was converted to alkanes (mainly heptadecane) in a hydrogen‐free atmosphere by using 2‐propanol as hydrogen donor. Transition metal doped Pd catalysts embedded on a porous organic support (hypercrosslinked polystyrene) were used as catalysts. A Pd‐Cu catalyst showed the highest effectiveness, allowing up to 99.9 mol % selectivity to heptadecane to be obtained. The process proceeds through fatty acid esterification, further hydrogenation of double bonds, and decarboxylation to form n‐heptadecane as main product. [ABSTRACT FROM AUTHOR]

This work addresses the Suzuki cross-coupling between 4-bromoanisole (BrAn) and phenylboronic acid (PBA) in an environmentally benign ethanol–water solvent catalysed by mono- (Pd) and bimetallic (PdAu, PdCu, PdZn) nanoparticles (NPs) stabilised within hyper-cross-linked polystyrene (HPS) bearing tertiary amino groups. Small Pd NPs of about 2 nm in diameters were formed and stabilized by HPS independently in the presence of other metals. High catalytic activity and complete conversion of BrAn was attained at low Pd loading. Introduction of Zn to the catalyst composition resulted in the formation of Pd/Zn/ZnO NPs, which demonstrated nearly double activity as compared to Pd/HPS. Bimetallic core-shell PdAu/HPS samples were 3-fold more active as compared to Pd/HPS. Both Pd/HPS and PdAu/HPS samples revealed promising stability confirmed by catalyst recycling in repeated reaction runs. [ABSTRACT FROM AUTHOR]

Carbon-carbon cross-coupling reactions are among the most important synthetic tools for the preparation of pharmaceuticals and bioactive compounds. However, these reactions are normally carried out using copper, phosphines, and/or amines, which are poisonous for pharmaceuticals. The use of nanocomposite catalysts holds promise for facilitating these reactions and making them more environmentally friendly. In the present work, the PEGylated (PEG stands for poly(ethylene glycol) pyridylphenylene dendrons immobilized on silica loaded with magnetic nanoparticles have been successfully employed for the stabilization of Pd2+ complexes and Pd nanoparticles. The catalyst developed showed excellent catalytic activity in copper-free Sonogashira and Heck cross-coupling reactions. The reactions proceeded smoothly in green solvents at low palladium loading, resulting in high yields of cross-coupling products (from 80% to 97%) within short reaction times. The presence of magnetic nanoparticles allows easy magnetic separation for repeated use without a noticeable decrease of catalytic activity due to the strong stabilization of Pd species by rigid and bulky dendritic ligands. The PEG dendron periphery makes the catalyst hydrophilic and better suited for green solvents. The minor drop in activity upon the catalyst reuse is explained by the formation of Pd nanoparticles from the Pd2+ species during the catalytic reaction. The magnetic separation and reuse of the nanocomposite catalyst reduces the cost of target products as well as energy and material consumption and diminishes residual contamination by the catalyst. These factors as well as the absence of copper in the catalyst makeup pave the way for future applications of such catalysts in cross-coupling reactions. [ABSTRACT FROM AUTHOR]

Influence of heterogenization on catalytic properties of block copolymer micellar catalysts derived from polystyrene-block-poly-4-vinylpyridine and containing Pd monometallic and bimetallic PdAu, PdPt, and PdZn nanoparticles has been studied in selective hydrogenation of the triple bond of 3,7-dimethyloctaen-6-yne-1-ol-3 (dehydrolinalool). We demonstrate that the heterogenization can both increase and decrease catalytic activity depending on the type of NPs. In the absence of a modifying metal (Pd monometallic nanoparticles) or for PdZn nanoparticles where Zn is the electron donor, the activity of heterogenized catalysts increases, while for PdAu and PdPt based catalysts, where the modifying metal is the electron acceptor, the activity decreases. These changes are explained by the increased polarity of the catalyst after deposition on alumina (addition of a component with a higher dielectric constant) offset by poor accessibility of some catalytic sites of nanoparticles containing electron deficient Pd atoms. [Copyright &y& Elsevier]

Abstract: This paper reports deposition of ultrathin poly(sodium-4-styrenesulfonate)/chitosan layers on a mesoporous alumina surface and the formation of catalytic Pd nanoparticles in mesopores covered by such layers. The structure of these nanoparticulate catalysts has been studied using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, N2 adsorption–desorption and CO chemisorption measurements. The Pd nanoparticles formed in the mesopores covered by ultrathin polymer layers do not exceed 2–3nm, revealing that these layers can control nucleation and growth of nanoparticles. The catalytic behavior of these catalysts has been investigated in selective hydrogenation of dehydrolinalool to linalool. The catalytic properties were found to depend on the amounts of poly(sodium-4-styrenesulfonate) and chitosan deposited on alumina, determining the nanoparticle coverage and formation of catalytic centers either before hydrogenation or in situ: the latter occurred when chitosan coverage was insufficient. High stability, low cost and exceptionally high catalytic activity, makes these catalysts promising candidates for broad catalytic applications. [Copyright &y& Elsevier]