Synthesis of N2-arylaminopyrimidine-5-carbonitrile derivatives via SNAr amination reaction

An efficient and high-yielding synthesis of N~2-arylaminopyrimidine-5-carbonitrile derivatives starting from arylamines and 2-methylthio-pyrimidine-5-carbonitriIe derivatives has been developed in the presence of cesium carbonate as basic reagent.This new protocol showed high chemical tolerance for a range of functional groups,and only the methylthio substituent on C2 of the pyrimidine ring was replaced with arylamine derivatives under the reaction conditions.     

1H NMR, mass spectroscopic studies and color fastness properties of methyl-4,6-dihydroxy-2-oxo-1-phenyl-5-arylazopyridine-3-carboxylate, part III: new disperse dyes

1H NMR and mass spectroscopic studies of new disperse dyes synthesized from methyl-4,6-dihydroxy-2-oxo-1-phenyl pyridine-3-carboxylate. Application of the dyes on polyester fabric and color fastness properties are also studied. The dyes are also found to possess DPPH free radical scavenging activity.     

Structural and microwave properties of (Ba,Sr)TiO3 films grown by pulsed laser deposition

The relationship between the structure and the microwave dielectric properties of epitaxial Ba_0.5Sr_0.5TiO₃ (BST) films has been investigated. Single-phase BST films (40-160 nm) have been deposited onto (100) MgO substrates by pulsed laser deposition. As-deposited films show a significant tetragonal distortion. The in-plane lattice parameters (a) are always larger than the surface normal lattice parameters (c). The tetragonal distortion depends on the thickness of the films and the post-deposition annealing conditions. Films annealed at 900 °C show less tetragonal distortion than the as-deposited film and the films annealed at higher temperatures. The distortion in the film is due to stress caused by the lattice mismatch and thermal expansion coefficient differences between the film and the substrate. The dielectric constant and its change with dc bias voltage of BST films on MgO at microwave frequencies increase with increasing annealing temperature from 900 °C to 1200 °C, which corresponds to an increase in the tetragonal distortion.     

Ultra-Weak Metal−Metal Bonding: Is There a Beryllium-Beryllium Triple Bond?

Metal-metal triple bonds featuring s-block element have not been reported until now. Only Be−Be double bonds between have been predicted theoretically based on the intuitive electron donation from four s¹ type electron-donating ligands. Herein, we theoretically predicted a novel species featuring a Be−Be triple bond in the Li₆Be₂ molecule. The molecule was found to be thermodynamically stable. The presence of the triple bond was confirmed by adaptive natural density partitioning (AdNDP), electron localization function (ELF), and atoms in molecules (AIM) analyses. Moreover, the mechanical strength of the Be−Be triple bond was analyzed by using compliance matrix, pointing towards its ultra-weak nature.     

Ultra‐small and highly dispersed Pd nanoparticles inside the pores of ZIF‐8: Sustainable approach to waste‐minimized Mizoroki–Heck cross‐coupling reaction based on reusable heterogeneous catalyst

The rapid development of nanomaterials, particularly advanced hybrid nanoparticles, has made new opportunities for the design and fabrication of high‐performance metal‐based catalysts. However, generating metal nanoparticles of desired size without aggregation is an important challenge for enhancing the catalytic activity of metal nanoparticles supported in the host matrix. In this work, a hybrid nanoporous material, namely Pd nanoparticles@N‐heterocyclic carbene@ZIF‐8, with a high internal surface area was successfully prepared using a dispersed anionic sulfonated N‐heterocyclic carbene–Pd(II) precursor inside the cavities of zeolitic imidazolate framework (ZIF‐8) using an impregnation approach followed by reduction with NaBH₄. The anionic sulfonated N‐heterocyclic carbene was found to be a superb ligand for the stabilization of Pd nanoparticles in the pores of ZIF‐8. The resulting system was applied to the Mizoroki–Heck cross‐coupling reaction, in which the catalyst showed high catalytic activity under mild reaction conditions.     

MCM‐41‐SO3H as a nanoreactor for the one‐pot,solvent‐free synthesis of 1,8‐dioxo‐9‐aryl decahydroacridines

One‐pot four‐component synthesis of 1,8‐dioxo‐9‐aryl decahydroacridines in solvent‐free condition was efficiently performed in the presence of MCM‐41‐SO₃H as a nanocatalyst and nanoreactor in good yields. The method provides several advantages such as low cost, operational and experimental simplicity, high yields, and short reaction times. J. Heterocyclic Chem., (2012).     

Platelet-Activating Factor (PAF) Antagonistic Activity of a New Biflavonoid from <em>Garcinia nervosa</em> var. <em>pubescens</em> King

The methanol extract of the leaves of Garcinia nervosa var. pubescens King, which showed strong inhibitory effects on platelet-activating factor (PAF) receptor binding, was subjected to bioassay-guided isolation to obtain a new biflavonoid, II-3,I-5, II-5,II-7,I-4',II-4'-hexahydroxy-(I-3,II-8)-flavonylflavanonol together with two known flavonoids, 6-methyl-4'-methoxyflavone and acacetin. The structures of the compounds were elucidated by spectroscopic methods. The compounds were evaluated for their ability to inhibit PAF receptor binding to rabbit platelets using ³H-PAF as a ligand. The biflavonoid and acacetin showed strong inhibition with IC₅₀ values of 28.0 and 20.4 μM, respectively. The results suggest that these compounds could be responsible for the strong PAF antagonistic activity of the plant.