An overview on synthetic strategies to coumarins

Coumarins units have recently emerged as a hot topic of research due to their diverse applications. Their synthesis is partly based on classical methodologies such as Pechmann reaction or Knoevenagel condensation, but it also sparked the discovery of completely new pathways. In very recent years so-called vertically expanded coumarins were synthesized, effectively expanding the portfolio of existing architectures. This review serves as a guide through synthesis strategies to coumarins.     

Overview on the synthetic routes to nicotine nitriles

The biological and medicinal properties of nicotinonitrile and its analogues have prompted enormous research aimed at developing synthetic routes to these heterocyclic. This review highlights the different synthetic routes to nicotine nitriles.     

A new pd-catalyzed cascade reaction for the synthesis of strained aromatic polycycles

Two new palladium catalyzed cascade reactions involving a 4-exo-dig cyclocarbopalladation are described. These processes are shown to convert bromoenediynes and bromodienynes into strained aromatic compounds in a single step.     

Metal complexes derived from hydrazoneoxime ligands: IV. Molecular and supramolecular structures of some nickel(II) complexes derived from diacetylmonoxime S-benzyldithiocarbazonate

Four new nickel(II) complexes, [{Ni(L)}₂], [NiL · HPyr], [NiL · HIm] and [Ni(HL)₂] · H₂O, derived from diacetylmonoxime-S-benzyldithiocarbazonate (H₂L) have been synthesized and characterized by elemental analyses, field desorption and electrospray ionization mass spectra, UV–Vis, infrared absorption spectra, as well as ¹H NMR spectra. X-ray molecular structures showed that the Ni(II) in both [NiL · HPyr] and [NiL · HIm] are in a distorted square planar environment and is coordinated to the dianionic NNS tridentate hydrazoneoxime ligand via deprotonated oximate nitrogen, hydrazone imine nitrogen, and thiolate sulphur. The fourth coordination sites are occupied, respectively, by the pyrazole and imidazole nitrogens. The oximate O1 of [NiL · HPyr] is involved in intramolecular hydrogen bond with the pyrazole NH proton as well as intermolecular hydrogen bond pyrazole C6H proton, forming a helical chain propagating along the b-axis. The structure is stabilized by a set of π?π and CH?π interactions. The molecular units in [NiL · HIm] are linked together by hydrogen bond formation between the oximate oxygen and imidazole NH proton, giving rise to an infinite zigzag chain extended along the a-axis. The chains are interconnected by π?π and CH?O interactions. In [Ni(HL)₂] · H₂O, the Ni(II) is in a distorted octahedral environment. The two mononegative hydrazoneoxime ligands are coordinated in the meridional configuration where the two thiol sulphur atoms and the two oxime nitrogen atoms are cis to each other, while the imine nitrogen atoms are trans. The oxime proton O2H is involved in a reciprocal bifurcated hydrogen bond formation with both N2 and S3 of the adjacent molecule giving rise to hydrogen bonded dimer. This dimeric structure is further stabilized by a pair of reciprocal CH?O interactions. A one dimensional chain of alternating dimeric unit and water molecule propagating along the c-axis is formed via hydrogen bond formation between the oxime O1 oxygen and the bridged water molecule proton.     

Intertwining Operators Associated to a Family of Differential-Reflection Operators

Mediterranean Journal of Mathematics - We introduce a family of differential-reflection operators $${\Lambda_{A, \varepsilon}}$$ acting on smooth functions defined on $${{\mathbb R}}$$ . Here, A is...     

A confident source of hard X‐rays: radiation from a tokamak applicable for runaway electrons diagnosis

In a tokamak with a toroidal electric field, electrons that exceed the critical velocity are freely accelerated and can reach very high energies. These so‐called `runaway electrons' can cause severe damage to the vacuum vessel and are a dangerous source of hard X‐rays. Here the effect of toroidal electric and magnetic field changes on the characteristics of runaway electrons is reported. A possible technique for runaways diagnosis is the detection of hard X‐ray radiation; for this purpose, a scintillator (NaI) was used. Because of the high loop voltage at the beginning of a plasma, this investigation was carried out on toroidal electric field changes in the first 5 ms interval from the beginning of the plasma. In addition, the toroidal magnetic field was monitored for the whole discharge time. The results indicate that with increasing toroidal electric field the mean energy of runaway electrons rises, and also an increase in the toroidal magnetic field can result in a decrease in intensity of magnetohydrodynamic oscillations which means that for both conditions more of these high‐energy electrons will be generated.     

Synthesis and antimicrobial evaluation of novel 1,3-thiazoles and unsymmetrical azines

Research on Chemical Intermediates - 1,3-Thiazol derivatives have been synthesized via reaction of 1-(1-(5,6-dimethoxy-2-oxobenzo[d]thiazol-3(2H)-yl)propan-2-ylidene)-4-substituted...     

A Validated Direct Thin-Layer Chromatographic Separation and Enantioselective Determination of Racemic Centrally Acting Drugs Using Ion-Pair and Ligand-Exchange Chiral Selectors: A Thermodynamic Study of Complexation

JPC – Journal of Planar Chromatography – Modern TLC - A rapid, inexpensive, and stereoselective densitometric—thin-layer chromatographic (TLC) method using l-(+)-tartaric acid and...     

Differentiable Distance Spaces

The distance function \({\varrho(p, q) ({\rm or} d(p, q))}\) of a distance space (general metric space) is not differentiable in general. We investigate such distance spaces over \({\mathbb{R}^n}\), whose distance functions are differentiable like in case of Finsler spaces. These spaces have several good properties, yet they are not Finsler spaces (which are special distance spaces). They are situated between general metric spaces (distance spaces) and Finsler spaces. We will investigate such curves of differentiable distance spaces, which possess the same properties as geodesics do in Finsler spaces. So these curves can be considered as forerunners of Finsler geodesics. They are in greater plenitude than Finsler geodesics, but they become geodesics in a Finsler space. We show some properties of these curves, as well as some relations between differentiable distance spaces and Finsler spaces. We arrive to these curves and to our results by using distance spheres, and using no variational calculus. We often apply direct geometric considerations.