Regio‐ and Diastereoselective and Enantiospecific Metal‐Free C(sp3)H Arylation: Facile Access to Optically Active 5‐Aryl 2,5‐Disubstituted Pyrrolidines

Optically active 5‐aryl 2,5‐disubstituted pyrrolidines are the principal structural moiety of many bioactive compounds including natural products and catalysts for asymmetric synthesis. A highly regio‐ and diastereoselective and enantiospecific method for direct C?H arylation of aliphatic amine has been developed. Structurally diverse enantiopure arylated pyrrolidines were synthesized from commercially available starting materials, through a single‐step three‐component reaction under metal‐ and oxidant‐free conditions. Furthermore, the complex analogous structure of CCK antagonist RP 66803 and angiotensin‐converting enzyme inhibitors was easily constructed using the synthesized arylated pyrrolidine derivative. Detailed theoretical calculations (M06‐2X/TZVPP/SMD//M06‐2X/6‐31+G(d,p) level) were also carried to investigate the mechanism and high level of stereocontrol involved in this direct sp³ C?H arylation reaction. Preference for a given regio‐ and stereoselectivity in the arylated product can be explained through elucidation of the mechanism for dehydration, generating azomethine ylide, and for the final re‐aromatization step. The calculated energies reveals that the re‐aromatization step is essentially rate determining, accompanying an activation barrier of Δ^≠${G{{{\rm S}\hfill \atop {\rm L}\hfill}}}$ =25.6 kcal mol^?1.     

Synthesis of Prebiotic Glycerol in Interstellar Ices

Contemporary mechanisms for the spontaneous formation of glycerol have not been able to explain its existence on early Earth. The exogenous origin and delivery of organic molecules to early Earth presents an alternative route to their terrestrial in situ formation since biorelevant molecules like amino acids, carboxylic acids, and alkylphosphonic acids have been recovered from carbonaceous chondrites. Reported herein is the first in situ identification of glycerol, the key building block of all cellular membranes, formed by exposure of methanol‐based — interstellar model ices to ionizing radiation in the form of energetic electrons. These results provide compelling evidence that the radiation‐induced formation of glycerol in low‐temperature interstellar model ices is facile. Synthesized on interstellar grains and eventually incorporated into the “building material” of solar systems, biorelevant molecules such as glycerol could have been dispensed to habitable planets such as early Earth by comets and meteorites.     

On the Stability and Thermodynamics of the Dark Energy Based on Generalized Uncertainty Principle

The new agegraphic Dark Energy (NADE) model (based on generalized uncertainty principle) interacting with Dark Matter (DM) is considered in this study via power-law form of the scale factor a(t). The equation of state (EoS) parameter ω _G is observed to have a phantom-like behaviour. The stability of this model is investigated through the squared speed of sound $v_{s}^{2}$ . It is found that $v_{s}^{2}$ always stays at negative level. This indicates instability of the considered model. Moreover, validity of the generalized second law of thermodynamics has been investigated assuming that the apparent horizon is the enveloping horizon. It has been observed that the generalized second law is valid throughout the evolution of the universe.     

Banana-shaped mesogens: effect of 2-methylresorcinol as the central unit on the mesomorphic properties of five-ring esters

Three homologous series of banana-shaped five-ring esters and one series of seven-ring esters derived from 2-methylresorcinol have been synthesized. This has been carried out to understand the effect of chemical structure on the mesomorphic properties of such compounds. It is shown that the 2-methyl substituent in the central phenyl ring destabilizes the mesophases when they are compared with those of the analogous unsubstituted compounds. Replacement of a phenyl ring by a biphenyl moiety (seven-ring esters) in the two arms of the bent-core molecule enhances the thermal range of the mesophases as well as the clearing temperatures. The mesophases have been characterized using techniques such as polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction, and by electro-optical investigations. In the 32 compounds investigated, two mesophases, B 1 and B 2 , have been identified.     

State selective electron capture in partially stripped ion-atom interaction at intermediate and high energies

Post form of “boundary corrected continuum intermediate state (BCIS)” approximation has been employed to study charge transfer cross-sections in collision of C^q+, N^q+ and O^q+ (q=1–5) with ground state atomic hydrogen in the energy range of 50–200 keV/amu. In this formalism we have adopted model potential for the interaction of the active electron with the projectile ion. Calculated results for total charge transfer cross-sections have significant improvement over other existing theoretical results in their comparison to the available experimental findings except for singly charge ions. Sub-shell distribution for total charge transfer cross-section has also been reported in graphical form. Predictions suggested by Olson in connection with the sub-shell distribution of total charge transfer cross-section has been reaffirmed. However, an oscillatory structure of charge state dependence of the total charge transfer cross-sections has not been found in the present investigation.     

Nanowires of metal-organic complex by photocrystallization: a system to achieve addressable electrically bistable devices and memory elements

A new method has been achieved to form a Cu:benzoquinone derivative (DDQ) charge-transfer complex by the photoexcitation of [Cu(DDQ)2(CH 3COO)2] ( 1) that has been synthesized by the reaction of DDQ and hydrated cupric acetate in acetonitrile. Photoexcitation of coordinated complex 1 leads to the formation of charge-transfer complex Cu2+(DDQ(.-)2 ( 2). The charge transfer complex 2, when spun on solid substrates, forms nanowires. Sandwich structures of 2 exhibit electrical bistability associated with memory phenomenon. Read-only and random-access memory phenomena are evidenced in nanowires of 2 providing a route to attend the issues pertaining to the addressibility of organic memory devices.     

Determination of sulphur in uranium matrix by total reflection X-ray fluorescence spectrometry

The possibility of sulphur determination in uranium matrix by total reflection x-ray fluorescence spectrometry (TXRF) has been studied. Calibration solutions and samples of sulphur in uranium matrix were prepared by mixing uranium in form of a standard uranyl nitrate solution and sulphur in the form of Na₂SO₄ standard solution, prepared by dissolving Na₂SO₄ in Milli-Q water. For major element analysis of sulphur, it was determined without separation of uranium whereas for the trace level determinations, uranium was first separated by solvent extraction using 30% tri-n-butyl phosphate (TBP) in dodecane as an extractant. In order to countercheck the TXRF results, a few samples of Rb₂U(SO₄)₃, a chemical assay standard for uranium, were diluted to different dilutions and sulphur content in these solutions were determined. The TXRF determined results for trace determinations of sulphur in these diluted solutions were counterchecked after addition of another uranium solution, so that sulphur is at trace level compared to uranium, separating uranium from these solution mixtures using TBP extraction and determining sulphur in aqueous phase by TXRF. For such TXRF determinations, Co was used as internal standard and W Lα was used as excitation source. The precision and accuracy of the method was assessed for trace and major element determinations and was found to be better than 8% (1σ RSD) and 15% at a concentration level of 1 μg/mL of sulphur measured in solutions whereas for Rb₂U(SO₄)₃, these values were found to be better than 4 and 13%, respectively.     

A new organic compound for the synthesis of gold nanoparticles

2,3,5,6-Tetrakis-(morpholinomethyl)hydroquinone (1) is used for the first time in the preparation of gold nanoparticles by the reduction of HAuCl₄ in water–methanol medium without using any capping agent. Compound 1 was prepared by Mannich-type aminomethylation of hydroquinone with morpholine. It is characterized by elemental analysis, FT-IR, UV–Vis and mass spectra and finally by single crystal X-ray diffraction. The ratio of HAuCl₄ and compound 1 played a vital role in controlling the shape and size of gold nanoparticles. The samples were characterized by Transmission Electron Microscopy (TEM), XRD, FT-IR, UV–Vis measurements. With the increasing amount of gold(III) solution with respect to compound 1, two different morphologies such as self-assembled and spherical gold nanoparticles have been observed. The results indicate that the morphology of gold nanoparticles with different sizes can be controlled by changing the concentrations of compound 1 and gold(III) solution.