Investigation of the one-pot synthesis of quinolin-2-(1H)-ones and the discovery of a variation of the three-component Ugi reaction

Rapid access to the quinolin-2-(1H)-one scaffold is afforded by a sequential 4 component Ugi–Knoevenagel condensation of an aminophenylketone, an aromatic aldehyde possessing electron donating moieties, cyanoacetic acid and an aliphatic isocyanide, in moderate to good yields (49–71%). Interestingly, when the reaction is performed using aromatic aldehydes bearing electron withdrawing moieties or isocyanides containing aromatic or ester units, a mixture of a quinolin-2-(1H)-one and an α-amino amide (Ugi three-component adduct) is afforded in varying ratios. Further when the reaction is performed utilizing a combination of an isocyanide-containing aromatic or carbonyl unit, and an aldehyde possessing an electron withdrawing functionality, the Ugi three-component adduct is exclusively afforded. In our hands this new variation of the Ugi 3CR proved to be efficient and robust affording analogues in good yields (51–70%).     

Attainable accuracy in the numerical integration of the Thomas—Fermi kinetic-energy functional using a modeled electron density

In the Hohenberg and Kohn formation of the density-functional theory of an electronic system, the basic variable is the electron (number) density. This quantity, however, is not known. For this reason, in an actual calculation, one has to resort to an approximate electron (number) density in order to evaluate the integral occurring in the Hohenberg and Kohn density functional framework. This poses the question: what is the accuracy beyond which one cannot penetrate in the numerical evaluation of the integrals? The present work attempts to provide an answer to this question by considering the Ne atom as an example and using the simplest energy-density functional, namely the Thomas-Fermi functional. In this functional, composed of three terms, there is only one term, the kinetic-energy functional, that has to be evaluated numerically. The evaluation of this integral is done by modeling the electron (number) density of the Ne atom and resorting to Simpson's compound rule. Following this, an error bound for the integral is established. This is the central result of this paper.     

Intrinsic characteristic times in the drift-diffusion problem

The redistribution of impurities in a sample in the shape of a slab filled with an isotropic liquid submitted to an external field is considered. The case in which the impurities are ions dissolved in the liquid, and the external field is an electric field is also investigated. It is shown that the intrinsic time connected with the presence of the electric field is proportional to the drift time. The constant of proportionality is of the order of the ratio between the thermal agitation energy and the electrostatic energy. A closed solution for the time evolution of the density of particles is obtained. The importance of the effect on real situations is investigated. The possible application of these results to nematic samples submitted to an external electric field is discussed.     

Intrinsic characteristic times in the drift-diffusion problem

The redistribution of impurities in a sample in the shape of a slab filled with an isotropic liquid submitted to an external field is considered. The case in which the impurities are ions dissolved in the liquid, and the external field is an electric field is also investigated. It is shown that the intrinsic time connected with the presence of the electric field is proportional to the drift time. The constant of proportionality is of the order of the ratio between the thermal agitation energy and the electrostatic energy. A closed solution for the time evolution of the density of particles is obtained. The importance of the effect on real situations is investigated. The possible application of these results to nematic samples submitted to an external electric field is discussed.     

Proton controlled intramolecular photoinduced electron transfer (PET) in podand linked squaraine-aniline dyads

Proton controlled intramolecular PET from an aniline moiety to a squaraine chromophore, attached to podand chains is reported, which to our knowledge is the first example where a squaraine dye is involved as an electron acceptor in an intramolecular PET process, and has implication in the design of PET based sensors.     

Proprietes chimiques des α-hydroxynitrones cycliques: Isomerisation en presence d'un acide d'une α-hydroxynitrone steroidique

The differing stabilities in an acid medium of two isomeric heterocyclic α-hydroxynitrones enables the electrophilic character of the α-hydroxynitrone functional group to be shown towards nucleophiles like water, methanol or the conjugate base of an acid. The electrophilic character is not observed in an alkaline medium where deuteriation experiments have shown the existence of an equilibrium in which an oximo-ketone structure or an anhydrobase is present.     

Polymorphic transitions in n-hydrocarbon-water and n-alcohol-water binary systems

The mixing of hydrocarbons and alcohols in an excess of water is explained by polymorphic transitions similar to crystallization in an ensemble of water clusters. Enthalpies of transitions of 4.90 ± 0.07 and 2.2 ± 0.3 kJ/mol are obtained for solutions of hydrocarbons and alcohols in an excess of water, respectively. It is concluded that the mixing of water in an excess of hydrocarbons and alcohols is similar to evaporation (the breaking of H-bonds) with an enthalpy of 34 ± 1.4 kJ/mol. It is established that a polymorphic transition occurs between two binodals, and is accompanied by the emergence of microphases (concentration fluctuations) of alcohols in water. Binodals and spinodals in an excess of water and alcohol coincide for butyl and other higher alcohols.     

Zherlock: an open source data analysis software

Zherlock is an open source software that provides state-of-the-art data analysis tools to the user in an intuitive and flexible way. It is a front-end to different numerical "engines" to produce a seamless integration of algorithms written in different computer languages. Of particular interest is creating an interface to high-level scientific languages such as Octave (a Matlab clone) and R (an S-PLUS clone) to enable efficient porting of new data analytical methods. Zherlock uses advanced scientific visualization tools in 2-D and 3-D and has been extended to work on virtual reality (VR) systems. Central to Zherlock is a visual programming environment (VPE) which enables diagram based programming. These diagrams consist of nodes and connection lines where each node is an operator or a method and lines describe the flow of data between nodes. A VPE is chosen for Zherlock because it forms an effective way to control the processing pipeline in complex data analyses. The VPE is similar in functionality to other programs such as IRIS Explorer, AVS or LabVIEW.     

A Hydrolase-Catalyzed Cyclization Forms the Fused Bicyclic β-Lactone in Vibralactone

Vibralactone is isolated from the basidiomycete fungus Boreostereum vibrans as one of the strongest lipase inhibitors. Its unusual β-lactone-fused bicycle is derived from an aryl ring moiety by an oxidative ring-expansion prior to an intramolecular cyclization. Herein, we report the discovery of the cyclase VibC which belongs to the α/β-hydrolase superfamily and is involved in the vibralactone biosynthesis. Biochemical and crystal studies suggest that VibC may catalyze an aldol or an electrocyclic reaction initiated by the Ser-His-Asp catalytic triad. For the aldol and pericyclic chemistry in living cells, VibC is a unique hydrolase performing the carbocycle formation of an oxepinone to a fused bicyclic β-lactone. This presents a naturally occurring, new enzymatic reaction in both aldol and hydrolase (bio)chemistry that will guide future exploitation of these enzymes in synthetic biology for chemical-diversity expansion of natural products.     

Diffusiophoresis of concentrated suspensions of spherical particles with distinct ionic diffusion velocities

The diffusiophoresis of a concentrated spherical dispersion of colloidal particles subject to a small electrolyte gradient is analyzed theoretically for an arbitrary zeta potential and double layer thickness. In particular, the influence of the difference in the diffusivities of cations and anions is discussed. A unit cell model is used to simulate a spherical dispersion, and a pseudospectral method is adopted to solve the equations governing the phenomenon under consideration. We show that, as in the case of an infinitely dilute dispersion, when the diffusivities of cations and anions are different, the diffusiophoretic mobility is no longer an even function of the zeta potential or double layer thickness. In contrast to the case of identical diffusivity of cations and anions, a local electric field is induced in the present case due to an unbalanced charge distribution between higher and lower concentration regions. Depending upon the direction of this induced electric field, the diffusiophoretic mobility can be larger or smaller than that for the case of identical diffusivity. The diffusiophoretic mobility is influenced mainly by the induced electric field arising from the difference in the ionic diffusivities, the concentration gradient, and the effect of double layer polarization.     

Microcapsule enabled multicatalyst system

We present a new microencapsulated catalyst and report its use in a tandem multicatalyst reaction. Using an encapsulation technique, we developed an active, site-isolated amine catalyst that is capable of catalyzing the addition of nitromethane to an aldehyde. When a second Lewis acid catalyst is added, the nitroalkene intermediate is trapped and converted to the corresponding Michael adduct. We show that if the amine catalyst is not encapsulated, the two catalysts cannot function together. Moreover, if the two reactions are performed in sequence rather than in tandem, the first reaction results in an undesired dinitro product and the desired Michael adduct is not formed.     

Chiral Amine Catalyzed Reductive Aldol/Reductive Michael Addition Cascade Towards Enantioselective Synthesis of Benzannulated Diquinanes

Disclosed here an amine-catalyzed reductive aldol-condensation followed by an intramolecular reductive Michael-addition cascade employing Hantzsch ester as hydride source to a keto-bis-enone to provide enantio- and diastereoselective benzannulated diquinanes having three consecutive stereocenters, one of which is an all-carbon quaternary formyl stereocenter. Interestingly, on changing a tether connecting the ketone and an enone moiety from an aliphatic to an aromatic, a change in reactivity is observed. In this case, instead of the above-mentioned reductive aldol condensation, an asymmetric aldol reaction occurs, followed by an iminium/enamine isomerization and, finally diastereoselective Michael addition reaction occurs. As a result, a bis-benzannulated diquinane is obtained with vicinal congested quaternary chiral centers.     

Lone pair effect in thallium(I) macrocyclic compounds

The role of the inert (lone) pair of electrons in thallium(I) salts is studied by comparison of the compounds [Tl@18-crown-6]+ X- (X = TlI4, ClO4) and [K@18-crown-6]+ ClO4-. In contrast to common introductory chemistry textbook opinions, the paradigm that s-p hybridization is a prerequisite for an inert electron pair to become stereochemically active in compounds of the heavier main group elements has to be revised. Instead, an inert pair of electrons is expected to become stereochemically involved whenever it is forced to participate in antibonding orbital interactions with its surroundings, and there is the possibility for a structural distortion that minimizes these repulsive forces. The structural distortion will occur to such an extent that repulsive orbital interactions and attractive electrostatic interactions counterbalance. Our results also provide an explanatory background for many of the rules of thumb that are found in the literature about why and when an inert electron pair is expected to become stereochemically active in a certain compound.     

Evaluation of Properties of Concrete Without Cement Produced Using Fly Ash-Based Geopolymer

The use of ordinary Portland cement (OPC) in the construction industry is inevitable. The huge production of OPC and its use in infrastructural development pose an environmental impact. Greenhouse gas emitted increases the global temperature and it is an alarming sign to everybody on the planet. Concrete is the most consuming material which is produced by using OPC and it is proven that OPC contributes a lot to CO₂ emission. Hence in this study attempt is made to produce concrete by using environment-friendly material like fly ash along with alkaline activators, which is termed Geo polymer concrete. The by-product fly ash is widely available worldwide. It is a by-product of thermal power plants. The use of fly ash in concrete produces less expensive and more cost-effective concrete than concrete made up using OPC. Due to its high silicate and alumina content, fly ash reacts with an alkaline solution to create an aluminosilicate gel that binds the aggregate and results in high-quality concrete. Fly ash is finer than cement, it occupies the pores of cement after hydration. This would result in denser concrete which gives higher strength. In comparison to ordinary concrete, fly ash-based geopolymer concrete offers better resistance to aggressive environments and high temperatures. In the present study, an alkaline activator of molarity 8 is used to prepare geopolymer concrete. The test specimens are cast and cured for 28 days. Test results indicate that an alkaline liquid fly-ash ratio (0.4) produces higher mechanical properties. Hence, geopolymer concrete produced in this study is found to be cost-effective and environment friendly.     

Adiabaticity Conditions for the Process of Stretching of Uniformely Deforming Polymers

Plastic deformation of polymers is accompanied by increasing temperature owing to the transformation of mechanical work for the deformation into heat. The effect of the strain rate on the heating of uniformly deforming polymer films is analyzed theoretically. A formula describing the heating value is derived. As in the case of a frontal spreading of the neck, an increase in the strain rate upon a uniform deformation results in the transition from an isothermal process to an adiabatic one. The rate of the transition to adiabatic strain conditions increases with a growth of deformation. As compared to the neck spreading process, the transition is shifted toward higher strain rates. At low elastic deformations and usual rate values, the strain proceeds in an adiabatic regime.     

Quartz-crystal sensors for biosensing and chemical analysis

The principle and applications of quartz-crystal sensors based on the three basic concepts for mass, viscosity, and viscoelastic changes are reported. In the general discussion the realization of a resonant frequency-resonant resistance diagram is described in detail. As an example of application to mass sensing, gas sensing with a carbon-coated quartz crystal is reported. Determination of the blood coagulation factor is used as an example of the application to viscosity sensing. As an example of viscoelastic measurement, an ion-exchange polymer-coated quartz crystal is investigated to show that viscoelasticity changes more than mass in the transport process. The possibility of developing new biosensors and chemical sensors is discussed on the basis of these results.     

Geometry and energy effects on the structure of hard sphere fluids

The density profile of molecules is an interesting property in the theoretical study of inhomogeneous fluids. In this work, the density profile of a hard sphere fluid around various hard and soft spheres is studied using a well-established version of the density functional theory called “modified fundamental measure theory”. The results obtained from this study show that an increase in the size of the central molecule leads to both an enhanced density profile at the contact point and an amplified layering structure. Similar effects can be observed when attraction between original and bulk molecules increases. Another finding of the present study is that increasing the size of the central molecule has a quasi-attractive role of an entropic origin called ‘depletion potential’. Since the molecule is not very large, the depletion potential can be mapped in a hard core with an attractive Yukawa tail. Increasing molecule softness, however, has an opposite effect and causes the height of the first peak of the density profile to diminish and the inhomogeneity of the structure to lighten.     

The influence of water on the friction forces of fibers in aramid fabrics

Fabrics based on high-impact organic fibers have an excellent potential to dissipate the energy of a ballistic impact. That is why they are used in protective helmets and flexible armor vests. The work of friction is the main mechanism of energy absorption in fabrics during a transverse impact. The friction forces of fibers were studied via the pullout of several neighboring fibers and via the transverse hardness indentation. The influence of water on indentation forces and pullout forces of Armos and Rusar fibers during their pullout from fabrics is studied. Water enhances friction force several-fold during the pullout of fibers. Consequently, the potential to dissipate the energy of an impact changes during a transverse action. The influence of moisture is irreversible in the Armos fabrics without a water-repellent coating, and drying does not lead to complete recovery of the friction forces of fibers. In the case of Rusar 56319 fabrics with a water-repellent coating, large drops of water roll off the fabric and only small drops influence the friction forces. A substantial variation in the indentation force is detected, thereby apparently providing evidence of the instability of the density of the fabric. An analysis of the mechanisms of energy dissipation is performed. The energy of the elastic deformation in an individual fiber is three times smaller than the kinetic energy of the fiber. Friction work can exceed the sum of kinetic energy and strain energy by an order of magnitude. The estimation of the value of the increase in the temperature of a fiber during an impact is performed. Heat is not emitted during an impact on an individual fiber in the case of the formation of a transverse wave during an inelastic impact. In the process of transmission of transverse and dilatational waves, the energy dissipation is proportionate to the impact velocity raised to the power of 8/3.     

Electron Correlations for Adiabatic Electrochemical Electron Transfer Reactions in a Model for an Electrode with an Infinitely Wide Conduction Band

Fresh general relationships for adiabatic free-energy surfaces (AFES) and corresponding diagrams of kinetic modes for adiabatic electrochemical electron transfer reactions are derived in the framework of an exactly solvable model for a metallic electrode with an infinitely wide conduction band. The model is a limiting case of the Anderson model applicable to the sp metals. In contrast to earlier studies of adiabatic reactions in a model for an electrode with an infinitely wide conduction band, this work accounts for the electron–electron correlation effects exactly. As an illustration, an AFES is calculated and a diagram of kinetic modes is constructed for a special case corresponding to the equilibrium electrode potential of a two-electron reaction. The exact AFES is compared with the AFES computed in the Hartree–Fock approximation and a spinless model. The correlation effects are shown to play a substantial role and lead to a considerable decrease in the activation free energy.     

A modified strategy for Pictet-Spengler reaction leading to the synthesis of imidazoquinoxalines on solid phase

An alternative strategy for Pictet-Spengler reaction involving an N-1 linked aromatic amine of imidazole and aldehydes is described. This is in contrast to a typical Pictet-Spengler reaction, which involves an aliphatic amine attached to the carbon of an activated aromatic nucleus and an aldehyde. Our strategy commences with the nucleophilic replacement of fluorine in resin-bound o-fluoro-nitrobenzoic acid with mono- or disubstituted imidazole, followed by reduction of the nitro group to give an N1 linked aromatic amine of the resin-bound imidazole. This was subsequently treated with an aldehyde in toluene at 80 degrees C and then oxidized in the presence of DDQ to give resin-bound imidazoquinoxalines. Finally, acidolytic cleavage furnished the desired compounds in high yields and purities.