Effect of microwave irradiation on the reactivity of chloroarenes in Suzuki—Miyaura reaction

Simple catalytic systems for the Suzuki—Miyaura reaction of aryl chlorides under microwave conditions were tested. Microwave irradiation facilitated the reaction course. The catalyst, base, and solvent effect were studied and two reaction systems offered reasonable to high yields within a short time.     

Metabolic Profiling of Murine Macrophages Exposed to Silver Nanoparticles at Dose and Time Dependencies

The macrophage time-dependent metabolic profile changing basal metabolism triggered by nanoparticles can be obtained and used to improve wound healing treatments. Herein this study demonstrates that metabolic status responds systematically to cytotoxicity manipulation, providing an interesting way of cellular control. Nuclear magnetic resonance (NMR) based metabolomics and cytotoxic assays are used to study RAW 264.7 cells exposed to AgNPs at different concentrations and incubation times. Cytotoxicity data show a slight decrease in cellular expansion rates accompanied by morphological changes in cells. Metabolomics show that despite the glycolytic activity of treated and non-treated cells remains unchanged; however, only the treated cells present a rich Citrate environment signaling up-regulation of Tricarboxylic-Acid-Cycle (TCA). Cells choose aerobic routes instead of anaerobic ones to produce energy and self-regulate their amino acid metabolism to balance TCA. Choline metabolism is down-regulated once its sub-products, Betaine and Glycine, are reduced, thus compromising Creatine synthesis. Phospholipid metabolism is down-regulated due to the decreasing of Phosphocholine and Sn-Glycerol-3-PC, in agreement with the cytotoxicity results. Pyroglutamate decreases in treated cells, signaling different levels of oxidative stress. These analytical tools can characterize AgNPs-treatments, even distinguishing dose and time dependencies. Therefore, the fine-tuning of exposition parameters can modulate cellular activity to achieve better wound healing.     

Amperometric Folic Acid Quantification Using a Supramolecular Tetraruthenated Nickel Porphyrin µ‐Peroxo‐Bridged Matrix Modified Electrode Associated to Batch Injection Analysis

A supramolecular Nickel (II) porphyrin complex containing four pyridyl‐bis(2,2′‐bipyridyl)chloro ruthenium meso substituents was submitted to successive voltammetric cycles in high alkaline media to produce a supramolecular matrix with Nickel centers linked by µ‐peroxo bridges, producing a highly stable thin film able to act as redox mediator for electrocatalytic oxidation of folic acid. The characterization of electrode surface material was performed by Scanning Electron Microscopy and Electrochemical Impedance Spectroscopy. The modified electrode was inserted into a batch injection electrochemical cell used for the rapid and precise quantification of folic acid in pharmaceutical products. The favorable hydrodynamic conditions provided by amperometry‐BIA association allowed a very high throughput with good linear range (1 to 200 µmol L^?1) and low detection limit (7.37×10^?7 mol L^?1). The electrochemical method was applied to the quantification of folic acid in different tablet samples. The results were comparable with values indicated by the manufacturer and those found using high HPLC according to the Brazilian Pharmacopoeia; commercial samples were submitted to a procedure in order to remove lactose of tablets, since carbohydrates act as interfering species. This procedure together with the electrochemical method showed to be simple, rapid, efficient and an appropriate alternative for quantifying this compound in real samples.     

Retention Behavior of Some Compounds Containing Polar Functional Groups on Perfluorophenyl Silica-Based Stationary Phase

A retention study on perfluorophenyl silica-based stationary phase was undertaken for some organic compounds containing different polar functionalities. The dependence of the retention factor on the content of organic modifier (acetonitrile, or methanol) in mobile phase was fitted by polynomial equations. The only exception was observed for adenine, which showed a sigmoidal dependence for the retention factor versus organic modifier content. The extrapolated values of retention factor for water as mobile phase (log k _w) from these dependences were well correlated with octanol–water partition constants (log K _ow), excepting the values for hexachlorocyclohexane isomers and adenine. Temperature dependences of the retention factor obeyed the van’t Hoff equation with thermodynamic parameters similar to those obtained in reversed phase on C8 or C18 stationary phases, excepting two statines whose dependences of ln k on the reciprocal value of absolute column temperature were nonlinear. Again, adenine had an atypical behavior with decrease in the retention factor with the increase in column temperature, due to possible tautomeric equilibria of this compound in presence of water, in accordance with theoretical models reported by literature. Charge modeling with MarvinSketch package program revealed charged centers from analyte molecule that could interact differently with charge centers from stationary phase.     

Pd-catalysed conjugate addition of arylboronic acids to <Emphasis Type="Italic">α,β</Emphasis>-unsaturated ketones under microwave irradiation

The Pd-catalysed conjugate addition of arylboronic acids to α,β-unsaturated cyclic ketones was studied under controlled microwave irradiation conditions. A variety of catalysts, bases and solvents was explored in order to achieve optimum yields in the shortest possible reaction time. Under optimised conditions (Pd(OAc)₂/2,2′-bipyridine and KF in a mixture of toluene, water, and acetic acid and 10 min microwave irradiation), a range of arylboronic acids was successfully added to several cyclic enones. With chiral phosphane ligands, a promising enantioselectivity was obtained (85 % ee).     

Carbon nanotube-nucleobase hybrids: nanorings from uracil-modified single-walled carbon nanotubes

Single‐walled carbon nanotubes (SWCNTs) have been covalently functionalized with uracil nucleobase. The hybrids have been characterized by using complementary spectroscopic and microscopic techniques including solid‐state NMR spectroscopy. The uracil‐functionalized SWCNTs are able to self‐assemble into regular nanorings with a diameter of 50–70 nm, as observed by AFM and TEM. AFM shows that the rings do not have a consistent height and thickness, which indicates that they may be formed by separate bundles of CNTs. The simplest model for the nanoring formation likely involves two bundles of CNTs interacting with each other via uracil–uracil base‐pairing at both CNT ends. These nanorings can be envisaged for the development of advanced electronic circuits.     

The microwave-to-flow paradigm: translating high-temperature batch microwave chemistry to scalable continuous-flow processes

The popularity of dedicated microwave reactors in many academic and industrial laboratories has produced a plethora of synthetic protocols that are based on this enabling technology. In the majority of examples, transformations that require several hours when performed using conventional heating under reflux conditions reach completion in a few minutes or even seconds in sealed-vessel, autoclave-type, microwave reactors. However, one severe drawback of microwave chemistry is the difficulty in scaling this technology to a production-scale level. This Concept article demonstrates that this limitation can be overcome by translating batch microwave chemistry to scalable continuous-flow processes. For this purpose, conventionally heated micro- or mesofluidic flow devices fitted with a back-pressure regulator are employed, in which the high temperatures and pressures attainable in a sealed-vessel microwave chemistry batch experiment can be mimicked.     

Semitransitive subsemigroups of the singular part of the finite symmetric inverse semigroup

We prove that the minimal cardinality of a semitransitive subsemigroup in the singular part $\mathcal{I}_{n}\setminus \mathcal{S}_{n}$ of the symmetric inverse semigroup $\mathcal{I}_{n}$ is 2n?p+1, where p is the greatest proper divisor of n, and classify all semitransitive subsemigroups of this minimal cardinality.     

Statistical Convergence of Infinite Series

In this paper we use the notion of statistical convergence of infinite series naturally introduced as the statistical convergence of the sequence of the partial sums of the series. We will discuss some questions related to the convergence of subseries of a given series.