Tandem A N—A N reactions in the synthesis of 1H-pyrrolo[3,2-e]-1,2,4-triazines and products of their oxidative transformations

The reactions of 3-aryl-1,2,4-triazines with -aminovinyl ketones or ethyl -aminocrotonates in acetic anhydride at room temperature afforded cyclic products of the tandem nucleophilic addition, viz., 3a,4,7,7a-tetrahydro-1H-pyrrolo[3,2-e]-1,2,4-triazines, in good yields. Under oxidative conditions, the latter compounds underwent the pyrrole-ring opening under the action of potassium permanganate to form the corresponding triazinones and were transformed into thriazolyl-substituted pyridines under the action of selenious acid.     

Chemistry and Structure of Diterpene Compounds of the Kaurane Series: VII. Chiral Complexes of Isosteviol with Aromatic Compounds

(4,8,13)-13-Methyl-16-oxo-17-norkaurane-18-carboxylic acid (isosteviol) forms with aniline, dimethylaniline, and toluene individual 2:1 molecular complexes whose crystals are isostructural. According to X-ray diffraction data, the supramolecular crystal structure of these complexes is formed by chiral double helices with a 4₃ screw axis, consisting of isosteviol molecules. The strands of the helices are linked together by intermolecular hydrogen bonds involving the carboxy and carbonyl groups of two isosteviol molecules of neighboring helices. In their turn, the two hydrogen-bonded isosteviol molecules form head-to-tail pseudocage dimers. The aromatic guests occupy fairly large cavities between the strands of isosteviol helices.     

Synthesis and structural study of Rb<Subscript>2</Subscript>FeZr(PO<Subscript>4</Subscript>)<Subscript>3</Subscript> phosphate with langbeinite structure

A new orthophosphate of rubidium, iron, and zirconium, crystallizing in the langbeinite structure (cubic system, sp. gr. P2₁3, Z = 4), was synthesized and investigated by X-ray powder diffraction and IR spectroscopy. The structure of the Rb₂FeZr(PO₄)₃ phosphate was refined by the Rietveld method using the neutron powder diffraction data (DN-2 time-of-flight diffractometer; Joint Institute for Nuclear Research, Dubna). This structure is characterized by a mixed framework [FeZr(PO₄)₃] with Rb atoms located in large cavities. Fe³⁺ and Zr⁴⁺ cations are distributed statistically over two independent crystallographic positions.     

Nonclassical polarization properties of fundamental radiation in the case of generation of the second optical harmonic by mixing

The evolution of quantum fluctuations of the quadrature components, the number of photons and the Stokes parameters of fundamental radiation that excites the second harmonic in interaction of type II is considered. Special attention is given to the variances of the Stokes parameters of the fundamental radiation. It is shown that the fluctuations of three Stokes parameters decrease and those of the fourth Stokes parameter increase in comparison with the fluctuations for the case of coherent radiation.     

Chemistry and Structure of Diterpene Derivatives of the Kaurane Series: V. Isosteviol Anhydrides

(4,8,13)-13-Methyl-16-oxo-17-norkaurane-18-carboxylic acid (isosteviol) anhydride is synthesized, which is a first representative of bisditerpene compounds of the kaurane series. The structures of the anhydride and isosteviol chloride were studies by X-ray diffraction and quantum chemistry (AM1).     

Crystal structure of non-stoichiometric copper selenides studied by neutron scattering and X-ray diffraction

Structural characteristics of non-stoichiometric copper selenides were studied by the elastic neutron and X-ray scattering techniques. Rietveld analysis was used to refine the structure of the high-temperature β-phase of the Cu_1.75Se, Cu_1.78Se, and Cu_1.83Se samples. The homogeneity ranges of the cubic phase were determined. The modification of the crystal structure accompanying the β-α phase transition was studied for Cu_1.75Se and Cu_1.98Se compounds within the 443-10 K temperature range. It was shown that the phase transition is accompanied by distortions of the fcc lattice and the ordering of copper ions.     

New phosphate Fe0.5Nb1.5(PO4)3 with an electrically neutral framework. Synthesis and crystal structure

A new iron-niobium phosphate, Fe_0.5Nb_1.5(PO₄)₃, has been prepared and studied by X-ray diffraction, electron microprobe analysis, IR spectroscopy, and neutron powder diffraction. On the basis of X-ray powder data, it was found that the synthesized phosphate crystallizes into the sp. gr. R $\bar 3$ c and corresponds to the structural type of sodium-zirconium phosphate NaZr₂(PO₄)₃. The structure was refined by the Rietveld method based on a powder neutron diffraction experiment. The obtained phosphate belongs to complex niobium orthophosphates and has a framework structure with a zero framework charge.     

Redox Treatment Effects on the Magnetic Properties of Copper Chromite

Magnetic susceptibility and low-temperature neutron diffraction measurements were performed to study the effect of redox treatments of copper chromite on its magnetic properties. When copper chromite is subjected to reduction at 453-643 K, magnetic ordering with T _c = 130 K disappears. Reoxidation does not completely restore the magnetic properties. The changes in the magnetic properties of copper chromite induced by sequential reduction and reoxidation correlate with its structural changes.     

Unusual course of the reaction of 15(<Emphasis Type="Italic">S</Emphasis>)-bromoisosteviol methyl ester with sodium azide

The reaction of 15(S)-bromoisosteviol methyl ester with sodium azide produced 15(S)-hydroxyisosteviol, the structure of which was elucidated by an x-ray structure analysis.