Solvent effects on the molecular stability,intramolecular hydrogen bond,and π-electron delocalization in the simple RAHB systems with different donors and acceptors: a quantum chemical study

Structural Chemistry - In the present study, solvent effects on the molecular stability, intramolecular hydrogen bond (IMHB), and π-electron delocalization (π-ED) in some of the simple...     

A novel and reusable magnetic nanocatalyst developed based on graphene oxide incorporated strontium nanoparticles for the facial synthesis of β‐enamino ketones under solvent‐free conditions

A novel magnetic SrFeGO nanocatalyst (NC) was synthesized through a simple sol–gel technique by introducing strontium and iron oxide nanoparticles onto graphene. The synthesized NC was characterized using FT‐IR and FE‐SEM. Subsequently, the catalytic activity of SrFeGO was tested in a reaction between β‐dicarbonyl compounds and aniline derivatives to gain β‐enamino ketone derivatives under solvent‐free conditions. It was found that SrFeGO NC is a potential catalyst for the synthesis of β‐enamino ketones. The β‐enamino ketone produced by such reactions could be isolated in high purity without the need for chromatographic purifications. The newly prepared magnetic graphene oxide nanocomposite could be recovered and reused for numerous times with no significant decrease in efficiency. Moreover, the protocol has the advantages of excellent yielding (up to 98%) in short a reaction time, benefitting an easy workup procedure and being environmentally friendly.     

A perspective view of top‐down proteomics in snake venom research

The venom produced by snakes contains complex mixtures of pharmacologically active proteins and peptides which play a crucial role in the pathophysiology of snakebite diseases. The deep understanding of venom proteomes can help to improve the treatment of this “neglected tropical disease” (as expressed by the World Health Organization [WHO]) and to develop new drugs. The most widely used technique for venom analysis is liquid chromatography/tandem mass spectrometry (LC/MS/MS)‐based bottom‐up (BU) proteomics. Considering the fact that multiple multi‐locus gene families encode snake venom proteins, the major challenge for the BU proteomics is the limited sequence coverage and also the “protein inference problem” which result in a loss of information for the identification and characterization of toxin proteoforms (genetic variation, alternative mRNA splicing, single nucleotide polymorphism [SNP] and post‐translational modifications [PTMs]). In contrast, intact protein measurements with top‐down (TD) MS strategies cover almost complete protein sequences, and prove the ability to identify venom proteoforms and to localize their modifications and sequence variations.     

A Catalytic Route to Pyrrole Derivatives via Copper‐catalyzed Multicomponent Reaction

A novel approach for the synthesis of pyrrole derivatives has been reported. The reactions starting from terminal alkynes, carbodiimides, and malononitrile using CuI, DBU, and TBPAc in anhydrous MeCN afforded the functionalized pyrroles in acceptable yields. Alkyl‐, aryl‐, and heteroaromatic terminal alkynes were tolerated. Carbodiimides could be symmetrical and unsymmetrical substrates with aryl or alkyl substituents. The reaction exhibited a good regioselectivity when unsymmetrical carbodiimides were employed.     

The role of pyruvic acid as starting material in some organic reactions in the presence of SBA-Pr-SO<Subscript>3</Subscript>H nanocatalyst

Pyruvic acid contains three different reactive positions: –COOH, ketone carbonyl and methyl groups. Correspondingly, pyruvic acid was applied as starting material in the modified Niementowski reaction and Aldol condensation using SBA-Pr-SO₃H as an efficient nanocatalyst. Aldol condensation of pyruvic acid and oxindole provided a new oxindol-based carboxylic acid which was subsequently used in the Ugi four-component reaction. Moreover, through the modified Niementowski reaction of pyruvic acid, new derivatives of quiazoline were produced in the presence of SBA-Pr-SO₃H. The obtained products are important due to their potentially biological active skeletons.     

A novel dicationic ionic liquid as a highly effectual and dual-functional catalyst for the synthesis of 3-methyl-4-arylmethylene-isoxazole-5(4H)-ones

Research on Chemical Intermediates - A novel dicationic ionic liquid, N,N,N′,N′-tetramethyl-N,N′-bis(sulfo)ethane-1,2-diaminium mesylate [TMBSED][OMs]2), has been produced, and...     

Thermal Characteristics of PVA-PANI-ZnS Nanocomposite Film Synthesized by Gamma Irradiation Method

Gamma irradiation is employed for in situ preparation of PVA-PANI-ZnS nanocomposite. The irradiation dose is varied from 10 to 40 kGy at 10 kGy intervals. The XRD result confirms the formation of crystalline phases corresponding to ZnS nanoparticles, PVA and PANI. Field emission scanning electron microscopy shows the formation of agglomerated PANI along the PVA backbone, within which the ZnS nanoparticles are dispersed.UV-visible spectroscopy is conducted to measure the transmittance spectra of samples revealing the electronic absorption characteristics of ZnS and PANI nanoparticles. Photo-acoustic(PA) setup is installed to investigate the thermal properties of samples. The PA spectroscopy indicates a high value of thermal diffusivity for samples due to the presence of ZnS and PANI nanoparticles. Moreover, at higher doses, the more polymerization and formation of PANI and ZnS nanoparticles result in enhancement of thermal diffusivity.     

Metal-free chemo- and regioselective acylation of pyridine derivatives with alcohols in water

A straightforward acylaltion of pyridine derivatives has been developed using K₂S₂O₈ as the oxidant and water as a green solvent. The corresponding 2-acylpyridines were synthesized with high chemo- and regioselectivity in good to high yields. This efficient and practical method could serve as a new tool for the convenient synthesis of 2-benzoylpyridines of interest for future pharmaceutical and chemical applications.