Synthesis of 1H-pyrrolo[2,3-b]phenoxathiin-2,3-dione

The title compound was obtained using the Sandmeyer reaction starting from 2-aminophenoxathiine. A new synthesis of N-methylpyrrolo[2,3-b]phenoxathiin-2,3-dione was also presented. Chemical and spectral data supporting the structure of the newly synthesized compounds were given. The isatin analogue, 1-methylpyrrolo-[2,3-b]phenoxathiin-2,3-dione-10, 10-dioxide, could not be obtained.Faculty of Chemistry, Organic Chemistry Department, University of Bucharest, 90–92 Panduri Road, Romania. Faculty of Pharmacy, Organic Chemistry Department, University of Medicine and Pharmacy Carol Davila, Bucharest, Romania. Published in Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 396–399, March, 1998.     

Dielectric properties of CuInP<Subscript>2</Subscript>(Se<Subscript>x</Subscript>S<Subscript>1−<Emphasis Type="Italic">x</Emphasis></Subscript>)<Subscript>6</Subscript> solid solutions

The dielectric properties of layered crystals of CuInP₂(Se_xS_1?x)₆ solid solutions are studied at x = 0.02, 0.05, 0.20, and 0.40. At a low selenium content (x ≤ 0.05), the solid solutions undergo a transition to the phase with short-range polar order. This transition manifests itself as a diffuse maximum in the temperature dependence of the permittivity ε′(T). Ferroelectric ordering in the solid solutions under investigation is suppressed at x > 1. It is assumed that the structural disordering initiated by the substitution of atoms in the anion sublattice of the solid solutions at 0.1 < x < 0.75 leads to the formation of the state of structured glass. The dielectric relaxation dispersion observed in the radio-frequency range at temperatures of 80–140 K is associated with the freezing of the relaxation dynamics of individual copper atoms.     

Formation of defects in gallium phosphide grown in the presence of oxygen

The influence of oxygen introduced in the gaseous phase on the formation of defects in GaP epitaxial layers is investigated by deep-level transient spectroscopy. The extremal dependences of the concentrations of charge carriers and electron traps with energy E _c−0.24 eV on the oxygen flux are discussed. Zh. Tekh. Fiz. 67, 52–55 (September 1997)     

Orientation effects in phenoxathiin acetylation and formylation

In acetylation and formylation of phenoxathiin, besides 2-acyl-substituted main products, the 3-isomers form in ca. 10% yield. The structure of 3-acetylphenoxathiin isolated by fractional crystallization from the mixture resulted after acetylation was proved by means of physical and chemical methods.Faculty of Chemistry, Organic Chemistry Department, University of Bucharest, 90-92 Panduri Road, Romania. SINDAN S.R.L. 11 1 Mai Blv., Bucharest, Romania.Published in Khlmiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1261–1265, September, 1996. Original article submitted May 8, 1996; revision submitted July 30, 1996.     

Dielectric properties of Sn2P2S6 crystals as a function of their growth conditions

The behavior of the permittivity near a phase transition in Sn₂P₂S₆ crystals of different technological quality is studied. It is established that, in high-resistance crystals, where an internal electric field is formed by the screening of spontaneous polarization in the polar phase, long-time relaxation of ɛ is observed in a temperature range ∼2 K above T _max. This relaxation and change in the form of the maximum of ɛ′(T) at a phase transition are attributed to an internal electric field induced by the volume space charge formed in regions near the surface. It is established that the existing differences in the properties of Sn₂P₂S₆ crystals are due to deviations from stoichiometry, arising during growth and synthesis of the crystals. Fiz. Tverd. Tela (St. Petersburg) 41, 1456–1461 (August 1999)     

Synthesis of potential anti-Trypanosoma cruzi azole-naftifine analogues by azide–alkyne click reaction

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