Preparation and stereoselectivity of 1,3-dipolar cycloaddition ofD-glucose-derived nitrones to N-arylmaleimides

Summary Nitrones2 derived fromD-glucose oxime and benzaldehydes without employing any protection of hydroxyl group were isolated in pure state. The 1,3-dipolar cycloaddition of2 to N-arylmaleimides gave predominantly theanti isoxazolidines3 and was rationalized byZ/E isomerization of N-glycosylnitrones2. The structure and steric configuration of the products have been assigned on the basis of¹H- and¹³C-NMR spectroscopy. AM1 calculations of the nitrones and MM2 calculations of the adducts were performed.

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Darstellung und Stereoselektivität der 1,3-dipolaren Cycloaddition vonD-Glucose-abgeleiteten Nitronen an N-Arylmaleimiden

Zusammenfassung Die Nitrone2 wurden ausD-Glucoseoxim und Benzaldehyden ohne Schutz von Hydroxylgruppen in reinem Zustand erhalten. Die 1,3-dipolare Cycloaddition von2 an N-Arylmaleimiden ergab bevorzugt dieanti-Isoxazolidine3; dies wurde über eineZ/E-Isomerisierung der N-Glycosylnitrone2 rationalisiert. Struktur und Stereochemie wurden auf Basis von¹H- und¹³C-NMR-Spektroskopie ermittelt. Außerdem wurden AM1-Berechnungen an den Nitronen und MM2-Rechnungen an den Addukten ausgeführt.

     

Synthesis of 1,1-dihydroperfluorooxaalkan-1-ols and their interaction with terephthaloyl chloride

A series of 1,1-dihydroperfluorooxaalkan-1-ols and ,,,-tetrahydroperfluorooxaalkanediols has been synthesized. Some tercphthalates were synthesized by the reaction of these alcohols and diols with terephthaloyl chloride.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1573–1576, June, 1996.     

Synthesis, X-ray structure and properties of a new nitrite-bound copper(II) complex with 2-(3,5- dimethylpyrazol-1-ylmethyl)pyridine in a CuN4(O) coordination

Synthesis and characterization of a nitrite-bound copper(II) compound [CuL⁴)₂(ONO)]ClO₄ have been achieved (L⁴ = 2-(3,5-dimethylpyrazol-1-ylmethyl)pyridine]. The bidentate ligand L⁴ provides a pyridine and a pyrazole donor site; however, they are separated by a methylene spacer. The complex has been structurally characterized and it belongs to only a handful of complexes having nitrito-bound mononuclear copper(II) centre. The metal atom has a distorted square pyramidal geometry with the copper atom displaced from the equatorial plane by 0.25 Å. In MeCN solution the green complex exhibits a broad ligand-field transition at 655 nm with a shoulder at 675 nm and in dichloromethane-toluene glass (80 K) it exhibits an EPR spectral feature characteristic of the unpaired electron in the d_x²−y² orbital. Variable-temperature (80–300 K) magnetic susceptibility measurements in the solid state as well as room temperature measurement in MeCN solution reveal mononuclear magnetically dilute copper(II) centre. When examined by cyclic voltammetry (MeCN solution) it displays electrochemically irreversible Cu^II---Cu^I response [cathodic peak potential, E_pc (V vs saturated calomel electrode (SCE)): −0.32]. An oxidative response is observed at 1.14 V, probably due to bound-nitrite oxidation and is partially removed to generate a solvated complex at the electrode surface. The latter species gives rise to reversible Cu^II---Cu^I redox response [ ].     

An easy preparation of per- and poly-fluoroalkyl propenyl sulfones

Sodium tridecafluorohexanesulfinate (1a) and sodium 1-chloro-2,2,2-trifluoroethanesulfinate (1b) were prepared by the treatment of 1-iodo-tridecafluorohexane and 1-bromo-1-chloro-2,2,2-trifluoroethane with sodium dithionite in a water-acetonitrile solution. Prolonged reaction of 1a with allyl bromide in DMF afforded tridecafluorohexane 1-propenyl sulfone 2 as the only product in good yield. A similar treatment of 1b gave exclusively 1-chloro-2,2,2-trifluoroethane 3-propenyl sulfone 4. Bromination of 4 followed by dehydrobromination with Et₃N resulted in a mixture of 1-chloro-2,2,2-trifluoroethane 3-bromo-1-propenyl sulfone 6 and 1-chloro-2,2,2-trifluoroethane 2-bromo-3-propenyl sulfone 7, while dehydrobromination with pyridine gave sulfone 6 practically as the only product. α,β-Unsaturated sulfones 2 and 6 were shown to be active dienophiles.     

Separation of mixtures of permanent gases and light hydrocarbons on spherical carbon molecular sieves by gas-solid chromatography

Summary Experimental results are presented on the application of Carbosieve S (Supelco) and Spherocarb (Analabs) spherical carbon molecular sieves for the gas chromatographic separation of mixtures of permanent gases and C₁–C₃ hydrocarbons using a single column or two columns in series. At a programmed temperature of 35–300°C, good separation of the sample components was obtained when using helium as the carrier gas. When hydrogen was used as the carrier gas and the analysis was carried out under isothermal conditions the elution sequence of oxygen and nitrogen reversed as the temperature was increased. This behaviour was observed within a temperature range of 35–225°C for Carbosieve S, and within a temperature range of 35–300°C for Spherocarb.     

Nanocomposites Produced by Direct Intercalation of Secondary Doped Polyaniline in V2O5

The possibility of the production of nanocomposites based on V₂O₅ and conducting polymers by direct intercalation of macromolecules of secondary doped polyaniline into the interlayer galleries of nanoparticles of aqueous V₂O₅ sol was demonstrated for the first time. The driving force of the intercalation process is substitution of the protons present in the galleries of the V₂O₅ by a polyaniline chain carrying a positive charge.     

Development of new lubricating grease formulations using recycled LDPE as rheology modifier additive

The recovery of plastic waste but also its applicability in product development may be an incentive to industry, since the use of such plastics represents a cheaper source of raw material. The aim of the present paper is to study the feasibility of recycling polyolefins as additives to improve the rheological properties of lithium 12-hydroxystearate lubricating greases. The effects that both soap and recycled low-density polyethylene (LDPE) concentration exert on the rheology of lithium lubricating greases and its relationship with grease microstructure are discussed in this work. In this way, different lubricating grease formulations were manufactured by modifying the concentration of lithium 12-hydroxystearate and content of recycled LDPE, according to a RSM statistical design. These lubricating greases were rheologically characterized through small-amplitude oscillatory shear (SAOS) and viscous flow measurements. In addition to these, scanning electronic microscopy (SEM) observations and mechanical stability tests were also carried out. Recycled LDPE was found to be an effective additive to modify grease rheology, acting as filler in the soap entangled microstructure. The values of both apparent viscosity and viscoelastic functions in the linear viscoelastic region increase with soap and recycled polymer concentrations. However, the addition of recycled LDPE distort the microstructural network of these greases resulting greases with less relative elastic characteristics and poorer mechanical properties as LDPE content increases.     

The effect of the solvents on the specific intramolecular C-H...N interactions studied by1H NMR spectroscopy

The analysis of the effect of the solvents on the proton chemical shifts in¹H NMR spectra of 2-vinyloxypyridine indicates that the C—H...N interaction of weak intramolecular hydrogen bond type hinders the formation of intermolecular hydrogen C—H...X and C-H... bonds. The protonating solvents reduce the intramolecular C—H...N interaction due to association with the N atom of the pyridine cycle.Translated fromIzvestiya Akademii Nauk. Seriya Khimieheskaya, No. S, pp. 1202–1204, May, 1996.     

Conversion of 3-benzoyl-1-methyl-4-phenyl-γ-piperidol by arylamines and arylhydrazines. Synthesis of 3-arylamino-1-oxo-1-phenylpropanes and 1,3-diarylpyrazoles and their fragmentation under electron impact

It has been established that on heating, 3-benzoyl-4-hydroxy-1-methyl-4-phenylpiperidine is ring-opened in the presence of arylamines by a type of retroaldol reaction, with subsequent transamination of the intermediate Mannich base and the formation of 3-arylamino-1-oxo-1-phenylpropanes. When using arylhydrazines this γ-piperidol is recyclized with the formation of 1,3-diarylpyrazoles and their 4,5-dihydro derivatives. The mass spectral behavior of a series of 3-arylamino-substituted 1-phenylpropanones has been studied. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1486–1495, October, 2007.