Palladium acetate assisted synthesis of five-membered N-polyheterocycles

Abstract

The metal-assisted synthesis of heterocyclic compounds is known to be one of the extremely developing as well as significant concepts of organic chemistry. Because of their expensive, complex working of the instrument and difficult procedures, the methodologies used earlier for the heterocycle synthesis were less amicable to the researchers. The Pd(OAc)₂-mediated cyclic reactions have been recognized to be very effective for both the stereoselective as well as regioselective formation of the 5-membered N-bearing heterocyclic compounds. The different uses of palladium acetate, as a catalyst in the formation of 5-membered N-containing polyheterocycles, are covered in this review article.     

X-ray,SEM, and DSC studies of ferroelectric Pb<Subscript>1−<Emphasis Type="Italic">X</Emphasis></Subscript>Ba<Subscript><Emphasis Type="Italic">X</Emphasis></Subscript>TiO<Subscript>3</Subscript> ceramics

The polycrystalline ferroelectric compounds of general formula Pb_1−X Ba _X TiO₃ with X = 0.00, 0.1, 0.2 and 0.5 were prepared by high temperature solid-state reaction technique using high purity oxides and carbonates. The compounds formation was confirmed by X-ray diffraction and all the X-ray peaks were indexed with tetragonal structure of space group P4mm. Morphology and particle size of the compounds were obtained using scanning electron microscopy. Ferroelectric phase transition, enthalpy change, and specific heat of the compounds were obtained using modulated differential scanning calorimetry. It was observed that the phase transition temperature decreased linearly with the increase of substitution concentration.     

In silico study of remdesivir with and without ionic liquids having different cations using DFT calculations and molecular docking

The new coronavirus is trying best to kill the humanity with its highly infectious nature and its first infection was reported in 2019; later this infection was named as COVID-19. Health-care systems are still the using repurposing drugs to cure the patients from this infection. Remdesivir is found to have good potential to cure the patients from this infection and is being extensively used during the 1^st and 2^nd wave of COVID-19. Therefore, in the present work, authors have studied the interaction of remdesivir with different ionic liquids with change in cations using density functional theory calculation in gaseous and water. Based on the DFT calculations, it was found that remdesivir interacts effectively with different ionic liquids based on the energy; further, the change in free energy for Remdesivir-[Bet-ester][Lev] (1) was found to be ?3223.5758 and ?3223.6533 hartree per particle in gaseous and water respectively and most stable; further, 2 and 3 have the comparable free energies. Further, the potential of remdesivir with and without ionic liquids against the main protease of SARS-CoV-2 was investigated using molecular docking. Results revealed that Remdesivir-[Chol][Lev] (2) and Remdesivir-[Chol-ether][Lev] (3) have shown promising results with binding energy of ?129.64 ?kcal/mol and ?125.44 ?kcal/mol respectively while Remdesivir [Bet-ester][Lev] (1) have a binding energy of -123.86 kcal/mol. It is important to mention that changing the cations in ionic liquid play an important role in the docking. It is also observed that the ionic liquid having sodium as cation, then the binding energy against Mpro of CoV is poor and even less than the remdesivir alone.     

X-ray, scanning electron microscopy and electrical properties of synthetic fresnoite (Ba2TiSi2O8) ceramics

Polycrystalline ceramic samples of fresnoite (Ba₂TiSi₂O₈ or BTS) have been prepared by a standard solid-state reaction method using high-purity oxides and carbonates. For one set of compounds, in stoichiometric ratio BaCO₃, TiO₂ and SiO₂ were melted at 1300°C and then sintered into pellet form, whereas the other set of compounds have been prepared without melting and sintered into pellet form at 1250°C. The formation of the single-phase compound and its structural parameters were investigated by X-ray diffraction followed by Rietveld refinement and scanning electron microscopic (SEM) techniques. A better agreement between the observed and calculated X-ray diffraction patterns was obtained by performing the Rietveld refinement with a structural model using the non-centrosymmetric space group P4bm. A better agreement between observed and calculated d-values shows that the lattice parameters calculated using the Rietveld refinement analysis are better than that of the earlier report so far. The activation energies of both compounds were calculated by measuring its dc electrical conductivities. The results are discussed in detail.     

Locating and staffing service centers under service level constraints

Many firms experience demand from geographically dispersed customers. This demand is satisfied by mobile servers that travel to the site of the customer. To achieve this in a cost-effective manner, the firm needs to decide where to locate its service centers, which customer regions to assign to the centers and the staffing level   at each center so that customers experience a defined level of service at minimum cost. To determine adequate staffing levels, we approximate a service center and the customer regions assigned to it as an M/G/s$M/G/s$ queueing system. Based on this queueing model, we explore properties of two different staffing level functions. The queueing model is embedded in a large-scale integer program. Using the concept of column generation, we develop an algorithm that can efficiently solve moderate-sized problems.     

Weak interactions between furfuryl and equatorial dioxime ligand in furfuryl(O2)Co(dmgH)2Py: NMR, X-ray and DFT calculations

The crystal and molecular structure of furfuryl(O₂)Co(dmgH)₂Py (1) has been determined by X-ray diffraction analysis. In the molecular structure of 1, the furfuryl ring oxygen is pointing inwards and is very close to one of the dmgH (Me) (2.625 Å). It shows unusual C-H···O weak interaction which must be responsible for the observed 1:3 ratio of dmgH methyl protons in NMR spectrum. Also, theoretical calculations using DFT have been performed on 1 for the Co-O and CH₂-C(furfuryl) bond rotation. Conformational energy diagrams derived from theoretical calculations also indicate that in most stable conformer the furfuryl ring oxygen is very close to one of the dmgH (Me) groups.     

RP-HPLC analysis of Jirakadyarishta and chemical changes during fermentation

Jirakadyarishta, an Ayurvedic formulation prepared by the fermentation of a decoction of Cuminum cyminum (seeds) is traditionally used for intestinal disorders. RP-HPLC analysis of the decoction and the final processed formulation revealed that apigenin-7-O-[galacturonide (1 --> 4)-O-glucoside] and luteolin-4'-O-glucoside-7-O-galacturonide) were the two major constituents of the decoction of C. cyminum. Selective hydrolysis of 7-O-glucosides of luteolin and apigenin during fermentation resulted in an increase in the amount of luteolin and apigenin. The 4'-O-glucoside-7-O-galacturonide of luteolin and galacturonide derivative of apigenin were not hydrolyzed during fermentation. Monomeric phenolics, together with 5-hydroxymethyl furfural (5-HMF), were also introduced into the formulation through the jaggery and other plant materials during fermentation. This communication highlights the importance of the ancient processing methods used in Ayurveda.     

A Spectrophotometric Determination of Ascorbic Acid

A new, simple and sensitive method for the spectrophotometric indirect determination of ascorbic acid in fruits, beverages, and pharmaceuticals is described. In this method, the ascorbic acid reduces Cu²⁺ to Cu⁺ and reacts with 2,9‐dimethyl‐1,10‐phenanothroline (neucoproine) to form Cu (neucoproine)⁺ complex, and it was extracted with N‐phenylbenzimidoylthiourea (PBITU) in chloroform. The apparent value of molar absorptivity of the complex in terms of ascorbic acid is (3.52) × 10⁴ L mole^?1 cm^?1 at λ_max, 460. The detection limit of ascorbic acid is 40 μg L^?1 and the method obeys Beer's law over the concentration range of 0.1–4.0 μg mL^?1. The proposed method was successfully applied for the determination of ascorbic acid in various samples. The validity of the present method was checked by the flow injection analysis (FIA) method.     

Monotone periodic orbits for torus homeomorphisms

Let be a homeomorphism of the torus isotopic to the identity and suppose that there exists a periodic orbit with a non-zero rotation vector . Then has a topologically monotone periodic orbit with the same rotation vector.