Chitosan-supported copper as an efficient and recyclable heterogeneous catalyst for A3/decarboxylative A3-coupling reaction

Chitosan-supported copper (chit@copper) based heterogeneous catalysts have been explored for A³-coupling and decarboxylative A³-coupling. The developed protocol employs low catalyst loading, solventless condition and easy work-up for the synthesis of diversely substituted propargylamines. More importantly, the catalyst could be recovered and reused without any significant loss in the activity. This offer huge advantages as recyclability issues are rarely addressed in decarboxylative A³-coupling. Leaching studies were carried out using AAS and ICPMS analysis. It is envisaged that chit@copper catalysts can have potential applications in terms of efficiency and recyclability in the emerging area of decarboxylative CH bond activation/functionalization strategies.     

Effect of monomer concentration and functionality on electro-optical properties of polymer-stabilised optically isotropic liquid crystals

Optically isotropic nature can open a new type of high-performance liquid crystal (LC) displays. The main features emerge from the interaction between LC and polymer network at the interface. At this point, we investigated the influence of cross-linking monomer concentration and functionality on electro-optic properties of optically isotropic liquid crystal (OILC) obtained by polymerisation-induced phase separation method. Interestingly, we obtained a pore-like network structure constructed by highly interlinked polymer beads in acrylate monomers and achieved fast decay response time (0.6 ms). We found that the voltage-dependent hysteresis was mostly eliminated (~0.25%), and the contrast ratio was enhanced (1:1550) for high functional monomers. The result inspires a simple way to optimise the materials to fabricate a high-performance OILC device and it shows high-transparency, low-driving voltage, hysteresis-free and sub-millisecond response time.     

Modeling protein-protein interactions through alanine-amide hydrogen bonds

The hydrogen-bonded complexes formed between alanine and formamide and between alanine and N-methylformamide have been completely investigated in the present study using ab initio molecular orbital theory (MP2) and density functional theory (B3LYP) using aug-cc-pVDZ basis set. Geometry optimization and vibrational frequency calculations have been carried out for isolated and hydrogen-bonded systems. The stabilization energies (?E_BSSE) suggest that alanine-N-methylformamide complexes are more stable than alanine-formamide complexes. The tendency of N-H of amide to act as hydrogen bond (HB) donor is found to be much better in relative to the N-H of amino group of alanine. The study suggests that the tendency of carbonyl oxygen of amide to act as HB acceptor towards various sites of alanine decreases in the order O–H?>?N–H?>?C–H. The results are corroborated by natural bond orbital (NBO) analysis, Bader’s theory of atoms in molecules (AIM) and molecular electrostatic potential (MEP) studies. The blue and red shifts in the stretching frequencies of HB donors X-H (X?=?O, N, C) have also been analysed.     

Green synthesis of three- to five-membered O-heterocycles using ionic liquids

The investigation for replacement of organic solvents in organic synthesis is a growing area of interest due to increasing environmental issues. The use of ionic liquid salts as solvents and catalysts in organic reactions has gained extensive interest. Ionic liquids provided a new environmentally benign and improved alternative to traditional methods in modern synthetic chemistry. The aim of present review is to focus on the applications of ionic liquids for the synthesis of O-heterocycles.     

Pyrrolidine-carbamate based new and efficient chiral organocatalyst for asymmetric Michael addition of ketones to nitroolefins

The novel ((S)-pyrrolidin-2-yl)methyl phenylcarbamate was synthesized and used as an efficient organocatalyst for the asymmetric Michael addition of cyclic/acyclic ketones to nitroolefins. Interestingly, the resulting Michael adducts were obtained in good to high yields (up to 96%) with excellent stereoselectivity (ee up to >99%, dr up to >99:1) without using any additive.     

Interactions of 3, 3.5, 4, and 4.5 generations of poly(amido amine) dendrimer with cationic surfactants

The conductivity (κ), turbidity (τ), NMR, and Krafft temperature (T _K) studies have been carried out for hexadecylpyridinium bromide (HPyBr), hexadecylpyridinium chloride (HPyCl), and hexadecyltrimethylammonium bromide (HTAB) in the presence of 3G, 3.5G, 4G, and 4.5G generations of poly(amido amine) dendrimers (PAMAM) in aqueous phase. The cmc of all present surfactants were evaluated from κ and τ measurements, both in the presence as well as in the absence of PAMAM. The cmc values decrease in the presence of PAMAM in comparison to that in pure water, especially in the presence of amine terminated PAMAM. Krafft temperature values of pure surfactants also decrease in the presence of various generations of PAMAM. A comparison of all present results from different techniques indicates that HPyBr interacts more strongly with all generations of PAMAM rather than HPyCl and HTAB.     

Simultaneous Determination of Cobalt and Nickel Using Morpholinedithiocarbamate (MDTC) as Reagent by First and Second Derivative Spectrophotometry

A selective and sensitive derivative method has been proposed for the simultaneous determination of trace amounts of Co(II) and Ni(II) with morpholinedithiocarbamate (MDTC) in the presence of sodium lauryl sulphate (SLS). The molar absorption coefficients of the 1:2 complex of Co(II) and Ni(II) at 326 nm and 322 nm are 2.248 × 10⁴ and 2.505 × 10⁴ L mol^?1 cm^?1 for zero order. The analytical sensitivity for the second derivative of Co(II) and Ni(II) complexes are 0.0044 μg mL^?1 and 0.0060 μg mL^?1. The developed derivative procedure, using the zero‐crossing technique, has been successfully applied for the analysis of Co(II) and Ni(II) simultaneously in different alloy samples.     

Colorimetric determination of capsaicin in capsicum fruits with the Folin-Ciocalteu reagent

Summary A colorimetric method for determination of capsaicin in capsicum fruits is described. The acetone or ethyl acetate extract (prepared at room temperature) is purified on a basic alumina (Brockmann Grade I) column and pure capsaicin is eluted with methanol-acetone-water (75251); the capsaicin content is determined after colour development with Folin-Ciocalteu reagent, the absorbance being measured at 760 nm. The method is reproducible and results are in good agreement with those obtained by existing methods.

---

Zusammenfassung Eine kolorimetrische Methode zur Bestimmung von Capsaicin in Paprikafrüchten wurde beschrieben. Der bei Zimmertemperatur gewonnene Aceton-oder Essigesterextrakt wird in einer Säule aus basischem Aluminiumoxid (Brockmann I) gereinigt und das reine Capsaicin durch Farbreaktion mit Folin-Ciocalteu-Reagens und Messung bei 760 nm durchgeführt. Die reproduzierbaren Ergebnisse stimmen mit denen anderer Methoden gut überein.