Palladium-catalyzed amino group arylation of 1,3-disubstituted 1H-pyrazol-5-amine based on Buchwald–Hartwig reaction

Chemistry of Heterocyclic Compounds - An efficient Pd-catalyzed C–N bond formation for the synthesis of different pyrazole derivatives using XPhos as a ligand and KOH as a base is presented....     

Microwave-assisted oxidation of alcohols by hydrogen peroxide catalysed by tetrabutylammonium decatungstate

This work deals with catalytic activity of tetrabutylammonium decatungstate(VI) in the oxidation of selected alcohols with hydrogen peroxide as an oxidant using 1,2-dichloroethane/water or acetonitrile/water as a solvent system. Different forms of heating were compared. The highest conversions of substrates were achieved in the two phase system acetonitrile/water using microwave irradiation combined with elevated pressure. Finally, optimum parameters for these reactions in a microwave pressurised reactor were established and discussed.     

Application of a device used for observation of controlled thermal processes in a furnace

This paper describes an appliance that allows to visually observe phenomena occurring in the studied materials during heating, from room temperature to 600 °C. The design criteria and device construction are described in details. The device allows for visual observation of physical phenomena of various material types, e.g., organic matter, polymers, and even observation of sintering mechanisms. Analysis of lubricant evaporation from powder metals (an aluminum alloy) in different atmospheres is shown. The featured device can also be used for interpretation of material defects. This is presented on the example of heating the aluminum alloy in an atmosphere containing oxygen (to simulate a furnace leakage). In addition, the influence of experimental atmosphere on melting and sintering processes is demonstrated. Another application of the presented device can be the visual observation of differences between combustion and pyrolysis processes. Our results show that the presented device is complementary with an advanced thermoanalysis apparatus which, in turn, does not allow visual observation of samples.     

Comparison of some dispersion-corrected and traditional functionals as applied to peptides and conformations of cyclohexane derivatives

We compare the energetic and structural properties of fully optimized α-helical and antiparallel β-sheet polyalanines and the energetic differences between axial and equatorial conformations of three cyclohexane derivatives (methyl, fluoro, and chloro) as calculated using several functionals designed to treat dispersion (B97-D, ωB97x-D, M06, M06L, and M06-2X) with other traditional functionals not specifically parametrized to treat dispersion (B3LYP, X3LYP, and PBE1PBE) and with experimental results. Those functionals developed to treat dispersion significantly overestimate interaction enthalpies of folding for the α-helix and predict unreasonable structures that contain Ramachandran φ and ψ and C = O[ellipsis (horizontal)]N H-bonding angles that are out of the bounds of databases compiled the β-sheets. These structures are consistent with overestimation of the interaction energies. For the cyclohexanes, these functionals overestimate the stabilities of the axial conformation, especially when used with smaller basis sets. Their performance improves when the basis set is improved from D95?? to aug-cc-pVTZ (which would not be possible with systems as large as the peptides).     

Convenient syntheses of novel 1-isothiocyano-alkylphosphonate diphenyl ester derivatives with potential biological activity

Herein, we describe a convenient method for the syntheses of novel 1-isothiocyano-alkylphosphonate diaryl ester derivatives and their antiproliferative activity. The syntheses are based on dithiocarbamates obtained in situ with the use of carbon disulfide under basic conditions, and their desulfurization using several different reagents, of which hydrogen peroxide proved to be the most efficient. The compounds synthesized demonstrated high antiproliferative activity against several cancer cell lines in vitro, and also showed some activity as serine protease inhibitors.     

Hydrodynamic shearing of DNA in a polymeric microfluidic device

With the advent of next-generation sequencing (NGS) systems and the associated high throughput they afford, the input to these machines requires manageable lengths of fragments (~1000 bp) produced from chromosomal DNAs. Therefore, it is critical to develop devices that can shear DNA in a controlled fashion. We report a polymer-based microfluidic device that establishes an efficient and inexpensive platform with performance comparable to a commercially available bench-top system.     

Anion-induced shuttling of a naphthalimide triazolium rotaxane

The anion-templated synthesis of a rotaxane structure, incorporating the new naphthalimide triazolium motif, is described and the interlocked host shown to exhibit selective, uni-directional, anion-induced shuttling. Initial pseudorotaxane investigations demonstrate the ability of a naphthalimide triazolium threading component to form interpenetrated assemblies with counter-anion-dependent co-conformations. (1)H NMR studies reveal that the shuttling behaviour of the analogous rotaxane host system is controlled by selective anion binding and by the nature of the solvent conditions. Complete macrocycle translocation only occurs upon the recognition of the smaller halide anions (chloride and bromide). The rotaxane solid-state crystal structure in the presence of chloride is in agreement with the solution-phase co-conformation. The sensitivity of the axle naphthalimide absorbance band to the position of the macrocycle component within the interlocked structure enabled the molecular motion to be observed by UV/Vis spectroscopy, and the chloride-induced shuttling of the rotaxane was reversed upon silver hexafluorophosphate addition.     

Acid-base equilibriums of lumichrome and its 1-methyl, 3-methyl, and 1,3-dimethyl derivatives

Lumichrome photophysical properties at different pH were characterized by UV-vis spectroscopy and steady-state and time-resolved fluorescence techniques, in four forms of protonation/deprotonation: neutral form, two monoanions, and dianion. The excited-state lifetimes of these forms of lumichrome were measured and discussed. The results were compared to those obtained for similar forms of alloxazine and/or isoalloxazine, and also to those of 1-methyl- and 3-methyllumichrome and 1,3-dimethyllumichrome. The absorption, emission, and synchronous spectra of lumichrome, 1-methyl- and 3-methyllumichrome, and 1,3-dimethyllumichrome at different pH were measured and used in discussion of fluorescence of neutral and deprotonated forms of lumichrome. The analysis of steady-state and time-resolved spectra and the DFT calculations both predict that the N(1) monoanion and the N(1,3) dianion of lumichrome have predominantly isoalloxazinic structures. Additionally, we confirmed that neutral lumichrome exists in its alloxazinic form only, in both the ground and the excited state. We also confirmed the existence and the alloxazinic structure of a second N(3) monoanion. The estimated values of pK(a) = 8.2 are for the equilibrium between neutral lumichrome and alloxazinic and isoalloxazinic monoanions, with proton dissociation from N(1)-H and N(3)-H groups proceeding at the almost the same pH, while the second value pK(a) = 11.4 refers to the formation of the isoalloxazinic dianion in the ground state.