Zinc triflate: a highly efficient reusable catalyst in the synthesis of functionalized quinolines via Friedlander annulation

An environmentally friendly and highly efficient procedure for the preparation of quinolines and fused polycyclic quinolines has been developed by a simple Friedlander annulation reaction of 2-aminoaryl ketone with carbonyl compounds in presence of zinc triflate under microwave irradiation and solvent-free conditions. The reaction also proceeds effectively when In(OTf)₃ was used in lieu of Zn(OTf)₂ as the catalyst. The catalyst can be recovered after the reaction and reused efficiently in subsequent runs.     

Variation of total columnar ozone characteristics over Dibrugarh, India and comparison with satellite observations over the Indian subcontinent

In this study, we investigate the characteristics of the total columnar ozone (TCO) over Dibrugarh (27.3° N and 94.6° E), India for the period September 2007 to February 2009 using Microtops II Ozonometer. These measurements are compared with TCO data available from Total Ozone Mapping Spectrometer (TOMS) on board Nimbus-7 satellite for the same period. It has been observed that the TCO increases from morning till noon and then decreases rapidly in the afternoon. A distinct seasonal variation of TCO is observed with low value in the months of September–December and high values in the month of April, May and June as seen from both Microtops II and TOMS measurements. Satellite observations reveal that the TCO at all latitudes is nearly equal in the months of September–November and May to August. The seasonal variation of TCO between December to May is nearly a mirror image between low and mid latitudes along the three longitudes sectors.     

Improved measurement of the K+-->pi+nunu; branching ratio

An additional event near the upper kinematic limit for K+-->pi(+)nunu; has been observed by experiment E949 at Brookhaven National Laboratory. Combining previously reported and new data, the branching ratio is B(K+-->pi(+)nunu;)=(1.47(+1.30)(-0.89))x10(-10) based on three events observed in the pion momentum region 211相似文献   

Effect of high energy ion irradiation on silicon substrate in a pulsed plasma device

We have performed an experimental analysis on the investigation of high energy ion beam irradiation on Si(1 0 0) substrates at room temperature using a low energy plasma focus (PF) device operating in methane gas. The surface modifications induced by the ion beams are characterized using standard surface science diagnostic tools, such as X-ray diffraction (XRD), scanning electron microscopy (SEM), photothermal beam deflection, energy-dispersive X-ray (EDX) analysis and atomic force microscope (AFM) and the results are reported. In particular, it has been found that with silicon targets, the application of PF carbon ion beams results in the formation of a surface layer of hexagonal (6H) silicon carbide, with embedded self-organized step/terrace structures.     

Investigation of phytochemicals and antioxidant capacity of selected <Emphasis Type="Italic">Eucalyptus</Emphasis> species using conventional extraction

Eucalyptus species have found their place in traditional medicine and pharmacological research and they have also been shown to possess a large number of phenolic compounds and antioxidants. The present study sought to implement conventional extraction to yield maximal total phenolic content (TPC), total flavonoid content (TFC), proanthocyanidins, antioxidants, and saponins from E. robusta using different solvents. The most suitable extraction solvent was further employed for extracting phytochemicals from E. saligna, E. microcorys, and E. globulus to select the Eucalyptus species with the greatest bioactive compound content. The results emphasised the efficiency of water in extracting TPC ((150.60 ± 2.47) mg of gallic acid equivalents per g), TFC ((38.83 ± 0.23) mg of rutin equivalents per g), proanthocyanidins ((5.14 ± 0.77) mg of catechin equivalents per g), and antioxidants ABTS ((525.67 ± 1.99) mg of trolox equivalents (TE) per g), DPPH ((378.61 ± 4.72) mg of TE per g); CUPRAC ((607.43 ± 6.69) mg of TE per g) from E. robusta. Moreover, the aqueous extract of E. robusta had the highest TPC, TFC and antioxidant values among the other Eucalyptus species tested. These findings highlighted the efficiency of conventional extraction in extracting natural bioactive compounds from Eucalyptus species for pharmaceutical and nutraceutical applications.     

Partial molar volumes and partial molar adiabatic compressibilities of potassium trioxalato complexes of Al(III), Fe(III), Co(III), and Cr(III) between 15° and 35°C

The apparent and limiting apparent molal volumes of dilute aqueous solutions of K₃[Al(ox)₃] · 3H₂O, K₃[Fe(ox)₃] · 3H₂O, K₃[Co(ox)3] · 3H₂O, and K₃[Cr(ox)₃] · 3H₂O complexes were determined from density data measured at 15°, 25°, and 35°C. The apparent and limiting apparent molal adiabatic compressibilities of these complexes were determined from measured ultrasonic sound velocities at 15°, 25°, and 35° in dilute aqueous solutions. The volume change associated with complex formation is discussed in terms of the nature of the coordinate bond and the overall hydration behavior of these complexes.     

A Carbohydrate-based Synthetic Approach to Diverse Structurally and Stereochemically Complex Chiral Polyheterocycles

Chiral polyheterocycles are one of the most frequently encountered scaffolds in natural products and in current drugs repertoire. A carbohydrate-based diversity oriented synthetic (DOS) approach has been employed for gaining access to many structurally diverse and stereochemically complex rigid polyheterocyclic molecules with multiple chiral hydroxyl groups to enhance aqueous solubility. Inexpensive chiral pool of D-Glucose has been judiciously exploited to get access of complex chiral polyheterocyclic structures using inexpensive, common achiral reagents and domino-Knoevenagel hetero-Diels-Alder (DKHDA) reaction as one of the key synthetic tools. Stereochemistry of newly generated stereocenters of polycyclic structures are unambiguously determined through NMR and X-ray crystallographic study. A chemoinformatic comparison (PCA and PMI) with 40 branded blockbuster drugs showed that newly generated polyheterocycles have good three-dimensional scaffold diversity and most of these pass the Lipinski filter of drug-likeness.     

Tripodal naphthalene ether ligand: Solid-state anion recognition and fluorescence studies

The simple tripodal amine ligand Tris-[2-(naphthalen-1-yloxy)-ethyl]-amine (L₁) was screened for anion recognition. Four crystal structures confirmed the inorganic as well as organic anion recognition in the solid state. Solid-state structures are results of supramolecular self-assembly and 3D molecular network involves C–HO and C–Hπ bonding in the crystal lattice. In the solid state, it forms a strong C–HCl and C–HO type interactions with the anions. This anion recognition was also confirmed by steady state fluorescence spectroscopy. In complex 4, L₁ is confined between 2D hydrogen bonded sheet formed by pyromellitic acid anion. L₁ shows unusually high selectivity toward nitrate in solution resulting in both a dramatic color change and a concomitant quenching of luminescence.     

Endocrine disruption: molecular interactions of chlorpyrifos and its degradation products with estrogen receptor

Structural Chemistry - Chlorpyrifos is an extensively used organophosphate pesticide showing broad-spectrum effectiveness on various target pests. Long-term sublethal exposure to this pesticide is...