DBU as a scaffold for the synthesis of [1,3]oxazolo[2’,3’ : 2,3]pyrimido-[1,2-a]azepines: annulation with aromatic cyanopropargylic alcohols

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Synthesis and Isomer Composition of 2-Polyfluoroalkoxy-1,3,2-dioxaphospholanes and -phosphinanes

Polyfluoroalkanols readily reacted with 2-chloro-1,3,2-dioxaphospholanes and 2-chloro-1,3,2-dioxaphosphinanes in hexane in the presence of triethylamine (–10 to 25°C, 5 h) to give 2-polyfluoroalkoxy-1,3,2- dioxaphospholanes and 2-polyfluoroalkoxy-1,3,2-dioxaphosphinanes in 48–72% yield. The products were found to exist as mixtures of cis and trans isomers with the trans isomer predominating for the phospholanes and cis isomer predominating for the phosphinanes according to the ¹H, ¹³C, ¹⁹F, and ³¹P NMR data.     

Potassium,calcium, and strontium complexes with diphenyloxo-18-crown-6. Synthesis and vibrational spectra

New K, Ca, and Sr complexes with diphenyloxo-18-crown-6 (2,3,5,6-dibenzo-1,4,7,10,13,16-hexaoxocyclooctadecadiene-2,5, DPO18C6) were prepared and isolated as solids. Their IR spectra (400–4000 cm^–1) were studied. On the basis of spectroscopic data, a structure was proposed for these compounds. In the complexes, DPO18C6 occurs in the inner sphere of K, Ca, and Sr. Only five oxygen atoms of the crown ether are involved in coordination, and the macrocycle conformation does not depend on the nature of the metal.Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 2, 2005, pp. 98–103.Original Russian Text Copyright © 2005 by Ivanova, Dorokhov, Kireeva, Pyatova, Yakshin, Tsivadze.     

Preparation of Porous Carbon–Mineral Materials by Chemical Treatment of Sapropel Carbonization Products

The effect of chemical treatment (with nitric acid, sodium hydroxide, or superheated steam) of sapropel carbonization products on the properties of the final carbon–mineral materials was studied. Steam activation exerts the strongest effect on the samples of carbon–mineral materials prepared from organic sapropel, leading to the maximal increase in the surface area and to a change in the textural characteristics. All kinds of treatment lead to a considerable increase in the fraction of micropores (to 26% of the total pore volume) and to a decrease in the fraction of macropores (from 44 to 14% of the total pore volume). The strongest changes in the properties of carbon–mineral materials prepared from mineral sapropel are observed upon acid treatment.     

Anticholinesterase properties of O,O-diisopropyl S-(β-N,N-arylmethylaminoethyl) thiophosphates and their methiodides

Russian Chemical Bulletin -     

Strain Hardening and Fracture of Austenitic Steel Single Crystals with High Concentration of Interstitial Atoms

Stages in the flow curves, mechanisms of deformation (slip or twinning), evolution of the dislocation structure and fracture are studied in austenitic stainless steel single crystals alloyed with nitrogen (C _N = 0–0.7 wt. %) and Hadfield steel in relation to the orientation of the crystal axis of tension, test temperature, and atomic concentrations of nitrogen and carbon. The dislocation-structure pattern (cellular or planar) and deformation mechanisms (slip or twinning) are shown to depend on the matrix stacking-fault energy _sf, friction forces due to solid-solution hardening by interstitial atoms, and crystal orientation. An interrelation between the stages in the flow curves and the type of dislocation structure is found. The contribution of mechanical twinning to the plastic flow of steel crystals is shown to increase with increase in nitrogen and carbon concentrations. The mechanical twinning develops in the early stages of deformation and determines the strain-hardening coefficient and fracture of crystals in high-strength states for interstitial atomic concentration C 0.5–0.7 wt. %. High deforming stresses due to solid-solution strain hardening by interstitial atoms of nitrogen and carbon in combination with low _sf are found to result in twinning in the <001> orientations. The values of _sf in Hadfield steel single crystals and in austenitic stainless steel single crystals are found experimentally depending on the concentration of nitrogen atoms and test temperature.