Enantioselective one-pot three-component synthesis of propargylamines catalyzed by copper(I)–pyridine bis-(oxazoline) complexes

A one-pot three-component coupling of aldehydes and amines in presence of terminal alkynes has been efficiently catalyzed by copper (I) complex of i-Pr-pybox-diPh 2b or s-Bu-pybox-diPh 2c. The process is simple and allows the synthesis of various propargylamines in good to excellent enantioselectivities (up to 99% ee) and in higher yields. The nature of the substituents attached to imines plays a vital role on the enantioselectivities obtained. The presence of gem-diphenyl group at C-5 position and secondary alkyl substituents at the C-4 chiral center of the oxazoline rings of the chiral ligands was found to be crucial for higher enantioselectivities. A transition state model involving π–π stacking is also proposed for the stereochemical outcome.     

Studies on testing and evaluation of platinum plated titanium electrode for production of uranous nitrate

Partitioning of plutonium from uranium is an important step in the reprocessing of spent fuel by PUREX process of solvent extraction using 30% TBP-dodecane. This is achieved by selectively reducing the Pu in solution to least extractable trivalent state by uranous nitrate as the reductant. The latter is conventionally produced by electrolytic reduction of uranyl ion in presence of hydrazine nitrate as uranous nitrate stabilizer using Pt-coated titanium as the anode. The anode plating wears out after period of operation thus affecting the process efficiency and hence the quality control testing of platinum plated electrode becomes important. This article describes the use of Beta backscattering method with strontium-90 radioisotope as non-destructive testing tool for measuring the coating thickness of the sample Ti electrode. The surface characteristics and coating morphology were also examined by scanning electron microscope and the micrographs are presented.     

Observation of field induced anomalous quantum criticality in Ce0.6Y0.4NiGe2 compound

We report the results of our investigation of magnetization and heat capacity on a series of compounds Ce${}_{1?x}$Y_xNiGe₂ ($x=0.1,0.2\text{ and }0.4$) under the influence of external magnetic field. Our studies of the thermodynamic quantity $?\mathrm{d}M/\mathrm{d}T$ on these compounds indicate that magnetic frustration persists in Ce_0.9Y_0.1NiGe₂, as also reported for the parent compound CeNiGe₂. The weak signature of this frustration is also noted in Ce_0.8Y_0.2NiGe₂, whereas, it is suppressed in Ce_0.6Y_0.4NiGe₂. Heat capacity studies on Ce_0.9Y_0.1NiGe₂ and Ce_0.8Y_0.2NiGe₂ indicate the presence of a new magnetic anomaly at high field which indicates that quantum criticality is absent in these compounds. However, for Ce_0.6Y_0.4NiGe₂ such an anomaly is not noted. For this later compound, the magnetic field (H) and temperature (T) dependence of heat capacity and magnetization obey $H/T$ scaling above critical fields. However, the obtained scaling critical parameter (δ) is 1.6, which is away from mean field value of 3. This deviation suggests the presence of unusual fluctuations and anomalous quantum criticality in these compounds. This unusual fluctuation may arise from disorderness induced by Y-substitution.     

Structural and optical characterization of CdS nanoparticles prepared by chemical precipitation method

In the present study we have synthesized CdS semiconducting quantum dots by the chemical precipitation method using Thioglycerol as the capping agent. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) are employed to characterize the size, morphology and crystalline structure of the as-prepared material. The synthesized QPs have a mixture of cubical and hexagonal crystal symmetry with 12 nm average diameter. Ultraviolet-visible (UV-vis) absorption spectroscopy is used to calculate the band gap of the material and blue shift in absorption edge. Confinement of the optical phonon modes in the QPs is studied by Raman spectroscopy, while FTIR for identification of chemical bonds in the nanomaterial. Multiple cadmium and sulphur defects were observed by employing the photoluminescence (PL) method.     

A Thermolysis Study of Poly(Trimethylene Phenylphosphinate) and Poly(2,2-Dimethyltrimethylene Phenylphosphinate). NMR and X-Ray Structure of 2-Oxo-2-Phenyl-4,4-Dimethyl-1,2-Oxaphospholan

Abstract

The syntheses of polyphosphinates 2 and 2a by the ring-opening polymerization of cyclic phosphonites 1 and 1a with CH₃I as an initiator have been reported in literature^1–3. These polymers thermally decompose to give oxaphospholan 3 and 3a. In this paper, we present evidence on the mechanism of their formation.     

Studies on Biologically Potent Tetraazamacrocyclic Complexes of Bivalent Tin

Fourteen- to eighteen-membered tetraamide macrocyclic ligands N 4 L 1 -N 4 L 4 have been prepared by the condensation of 1,2-diaminoethane or 1,3-diaminopropane with malonic or succinic acid in the presence of condensing reagents dicyclohexylcarbodiimide and 4-dimethylaminopyridine. On reduction, these macrocyclic ligands give a new series of tetraazamacrocycles MacL 1 -MacL 4 which form complexes with tin(II) chloride. The ligands and their complexes were characterized by elemental analyses, molecular weight determinations, infrared and 1 H NMR spectral studies. The hexacoordinated state for tin has been confirmed by spectral studies. An octahedral geometry for these complexes has been proposed as the binding sites are the nitrogen atoms of the macrocycles. On the basis of the chemical composition the representation of the complexes as [Sn(MacL n )Cl 2 ] (n = 1-4) has been established. The ligands and their complexes also have been screened for their antifungal and antibacterial activities and the findings have been reported and explained.     

Pyrenoimidazole‐Based Deep‐Blue‐Emitting Materials: Optical,Electrochemical, and Electroluminescent Characteristics

A series of pyrenoimidazoles that contained various functional chromophores, such as anthracene, pyrene, triphenylamine, carbazole, and fluorene, were synthesized and characterized by optical, electrochemical, and theoretical studies. The absorption spectra of the dyes are dominated by electronic transitions that arise from the pyrenoimidazole core and the additional chromophore. All of the dyes exhibited blue‐light photoluminescence with moderate‐to‐high quantum efficiencies. They also displayed high thermal stability and their thermal‐decomposition temperatures fell within the range 462–512 °C; the highest decomposition temperature was recorded for a carbazole‐containing dye. The oxidation propensity of the dyes increased on the introduction of electron‐rich chromophores, such as triphenylamine or carbazole. The application of selected dyes that featured additional chromophores such as pyrene, carbazole, and triphenylamine as blue‐emissive dopants into multilayered organic light‐emitting diodes with a 4,4′‐bis(9H‐carbazol‐9‐yl)biphenyl (CBP) host was investigated. Devices that were based on triphenylamine‐ and carbazole‐containing dyes exhibited deep‐blue emission (CIE 0.157, 0.054 and 0.163, 0.041), whereas a device that was based on a pyrene‐containing dye showed a bright‐blue emission (CIE 0.156, 0.135).     

O-(2-Aminobenoyl)-Hydroxylamine—A New Reagent for the Direct Conversion of Audehydes to Nitriles

Refluxing an ethanolic solution of O-(2-aminobenzoyl) -hydroxylamine (1) aldenydes and BF₃-Et₂ yields (78–94%) the corresponding nitriles.     

A Convenient Synthetic Entry Into 2,2-Diorganyl-5,6-Diaryl-1,3,4,2-Dioxaza Silacyclohexene Derivatives VIA Dianion Cyclisation: Sequential One-Pot Cyclosylation

In a convenient one-pot sequence, treatment of bezoin and p-anisoin oximes with sodium hydride in dry THF in 1:2 molar ratio generates 1,5-dianion, which upon subsequent addition of diorganodichlorosilane yields 1,3,4,2-dioxazasilacyclohexene derivatives in good yields. In general, very often a salt elimination route is used for the synthesis of the title compounds.