SBA‐15‐functionalized melamine–pyridine group‐supported palladium(0) as an efficient heterogeneous and recyclable nanocatalyst for N‐arylation of indoles through Ullmann‐type coupling reactions

SBA‐15‐functionalized melamine–pyridine group‐supported palladium(0) was found to serve as a heterogeneous and recyclable nanocatalyst for N‐arylation of indoles with aryl iodides under a low catalyst loading (0.3 mol% of Pd) through Ullmann‐type C? N coupling reactions. A variety of aryl iodides could be aminated to provide the N‐arylated products in good to excellent yields without the need of an inert atmosphere. Also, this catalyst was found to be an efficient system for the N‐arylation of other nitrogen‐containing heterocycles with aryl iodides. The heterogeneous palladium catalyst could be recovered by simple filtration of the reaction solution and reused for six cycles without significant loss in its activity. Copyright © 2015 John Wiley & Sons, Ltd.     

Green synthesis of palladium nanoparticles using Pistacia atlantica kurdica gum and their catalytic performance in Mizoroki–Heck and Suzuki–Miyaura coupling reactions in aqueous solutions

A one‐pot green method for the synthesis of palladium nanoparticles (Pd‐NPs) supported on Pistacia atlantica kurdica (P. a. kurdica) gum is described. This natural gum is used as a reducing and stabilising agent. The formation of the Pd‐NPs/P. a. kurdica gum catalyst was verified using several techniques, such as Fourier transform infrared spectroscopy, ultraviolet–visible spectrophotometry, scanning and transmission electron microscopies, X‐ray diffraction, energy‐dispersive X‐ray spectroscopy, dynamic light scattering and wavelength‐dispersive X‐ray spectroscopy. The Pd‐NPs stabilised by P. a. kurdica gum were employed as a heterogeneous catalyst in Mizoroki–Heck and Suzuki–Miyaura cross‐coupling reactions at low palladium loading (0.1 mol%) under aerobic, phosphine‐free and ligand‐free conditions in water. Product yields of up to 98%, a facile work‐up, no evidence of leached palladium from the catalyst surface and smooth recovery of the catalyst, which can be reused at least eight times, confirm the efficiency of the catalysts in the reactions investigated. Copyright © 2015 John Wiley & Sons, Ltd.     

Silica Phenyl Sulfonic Acid as a Solid Acid Heterogeneous Catalyst for Chemoselective Thioacetalization of Carbonyl Compounds and Dethioacetalization under Mild Conditions

Silica phenyl sulfonic acid (SPSA) is an effective catalyst for chemoselective thioacetalization of aldehydes in the presence of ketones under neutral conditions. In addition, a simple and an efficient procedure for deprotection of 1,3‐dithianes and 1,3‐dithiolanes of aromatic, aliphatic, and α,β‐unsaturated aldehydes and ketones in the solvent‐free to the corresponding parent carbonyl compounds was successfully carried out with SPSA in excellent yields.     

Covalently Linked at the Lower Rim Double‐Calix[4]arene as a Precursor for Multicavity Supramolecular Receptor

New covalently linked at the lower rim double‐calix[4]arens, which have great potential for the synthesis of multicavity receptors, were prepared via Sonogashira cross‐coupling reaction. The structures of 6 and 7 were confirmed by NMR, MS, and elemental analysis.     

Ag nanoparticles decorated Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/chitosan nanocomposite: synthesis,characterization and application toward electrochemical sensing of hydrogen peroxide

We studied a rapid, sensitive and selective amperometric sensor for determination of hydrogen peroxide by electrodeposited Ag NPs on a modified glassy carbon electrode (GCE). The modified GCE was constructed through a step by step modification of magnetic chitosan functional composite (Fe₃O₄–CH) and high-dispersed silver nanoparticles on the surface. The resulted Ag@Fe₃O₄–CH was characterized by various analytical methods including Fourier transform infrared spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy and cyclic voltammetry. The proposed sensor employed Ag@Fe₃O₄–CH/GCE as the working electrode with a linear current response to the hydrogen peroxide concentration in a wide range from 0.01 to 400 µM with a low limit of detection (LOD = 0.0038 µM, S/N = 3). The proposed sensor showed superior reproductivity, sensitivity and selectivity for the detection of hydrogen peroxide in environmental and clinical samples.     

SiO2-functionalized melamine-pyridine group–supported Cu(OAc)2 as an efficient heterogeneous and recyclable nanocatalyst for the N-arylation of amines through Ullmann coupling reactions

This study reports a convenient approach to prepare SiO₂/CCPy/Cu(OAc)₂ as a novel nanocatalyst, in which melamine-bearing pyridine groups have functionalized SiO₂ and can act as a capping agent to stabilize Cu(II) species. The catalyst is characterized through Fourier transform infrared, transmission electron microscopy, field emission scanning electron microscopy (FESEM), Brunauer–Emmett–Teller (BET), thermogravimetric analysis, inductivity coupled plasma (ICP), and energy dispersive X-ray (EDX) techniques. Furthermore, its catalytic behavior is evaluated in the N-arylation of indole, imidazole, and aniline during Ullmann-type C–N coupling reactions. Moreover, it has been proved that the heterogeneous nanocatalyst can be feasibly recovered by filtration and reused in five consecutive reaction cycles without any noticeable loss of its catalytic activity. The results clarified that the devised method is advantageous from several perspectives, that is, low catalyst loading, high product yield, experimental simplicity, broad substrate scope, and short reaction time.     

Puckering behavior in six new phosphoric triamides containing aliphatic six- and seven-membered ring groups and a database survey of analogous ring-containing structures

The influence of a N heteroatom on the ring conformations of six- and seven-membered aliphatic rings in six new C(O)NHP(O)-based phosphoric triamide structures (analysed by X-ray crystallography) is investigated. Additionally the influence of steric and crystal packing effects is also studied by the analysis of Hirshfeld surfaces. The results are compared to analogous structures with three- to seven- aliphatic membered rings deposited in the Cambridge Structural Database. In the newly determined structures, the six-membered rings only show the near-chair conformation with a maximum deviation of the θ puckering parameter of 4.4° from the ideal chair value of 0°/180°, while the seven-membered rings are found in different conformations such as near-chair, twist chair and twist sofa.     

Green synthesis of imidazo[1,2-a]pyridines using calix[6]arene-SO3H surfactant in water

In this research, green synthesis of imidazo[1,2-a]pyridines in the presence of calix[n]arenes-SO₃H as a Brønsted acid catalyst and surfactant is described. Using of calix[n]arenes in water provided a hydrophobic cavity that successfully carried out the synthesis reactions at short times with high yields. This catalyst system is recoverable with a simple extraction using an organic solvent and reusable for at least for 5 cycles without any losses of its activity.