Influence of cellular substructure on the thermal conductivity of heterovalent solid solutions of fluorides

The thermal conductivity of single-crystal samples of Sr_0.88La_0.09Nd_0.03F_2.03 and Sr_0.80La_0.15Nd_0.05F_2.20 solid solutions, both with a cellular substructure and without it, have been investigated by the method of stationary longitudinal heat flow in the temperature range of 50–300 K. An anisotropy of thermal conductivity (related to the substructure) is established for a Sr_0.995Nd_0.005F_2.005 single crystal.     

Fluoride optical nanoceramics

The methods for preparation of highly transparent optical ceramics based on simple and complex fluoride compounds of elements of the first, second, and third Group in the Periodical system are considered. The use of precursors as nanopowders and processes of their self-assembling on heating results in maximally homogeneous, transparent, and mechanically strong ceramics. The resulting calcium fluoride ceramics possess optical losses of 10⁻²–10⁻³ cm⁻¹ at 1.06 μm and shock resistance characterized by the fracture toughness K _1C = 4.7±0.3 MPa m^1/2 (for comparison, for a calcium fluoride single crystal K _1C = 1.5±0.15 MPa m^1/2). Regularities of the chemistry of fluoride nanopowders were considered in comparison with the oxide nanopowders: the fluorides are prone to hydrolysis, and powder nanoparticles precipitated from aqueous solutions have complex and heterogeneous (over the volume) chemical composition. The spectral luminescence properties of the ceramics activated by rare-earth metals (Ce³⁺, Nd³⁺, Er³⁺, Yb³⁺) or containing active color centers are presented. The generation properties of the lithium fluoride ceramics with the color centers and the ternary Ca-Sr-Yb fluoride during diode laser pumping are describe Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 863–872, May, 2008.     

Synthesis of 3-methyl-4-(5-R-1H-1,2,4-triazol-3-yl)-1,2,5-oxadiazoles

A number of 3-methyl-4-(5-R-1H-1,2,4-triazol-3-yl)-1,2,5-oxadiazoles were obtained in high yields by thermal dehydration of acylated 4-methyl-1,2,5-oxadiazole-3-carboxamide hydrazones.     

Substituted 2-aminonicotinamides in the synthesis of pyrido[2,3-d]pyrimidin-4(1H)-ones, 2,3-dihydropyrido- [2,3-d]pyrimidin-4(1H)-ones, and 11b,12-dihydropyrido- [2',3':4,5]pyrimido[2,1-a]isoindole-5,7-diones

The reactions of 2-aminonicotinamides with triethyl orthoformate, carboxylic acids chlorides, aldehydes, and 2-formylbenzoic acid were studied. As a result pyrido[2,3-d]pyrimidin-4(1H)-ones, 2,3-dihydropyrido[2,3-d]pyrimidin-4(1H)-ones, and 5,7,11b,12-tetrahydropyrido[2',3':4,5]pyrimido- [2,1-a]isoindole-5,7-diones were obtained.     

Synthesis and antineoplastic properties of (1H-1,2,3-triazol-1-yl)furazans

A method of 3-amino-4-[5-aryl(heteroaryl)-1H-1,2,3-triazol-1-yl)]furazan synthesis was optimized. Condensation of these compounds with 2,5-dimethoxytetrahydrofuran resulted in a series of previously unknown 4-[5-aryl(heteroaryl)-1H-1,2,3-triazol-1-yl)]-3-(pyrrol-1-yl)furazans. All target compounds were evaluated for both antimitotic microtubule destabilizing effect in a phenotypic sea urchin embryo assay and cytotoxicity in a panel of 60 human cancer cell lines. Pyrrolyl derivatives of triazolylfurazans were determined as antiproliferative compounds. The most potent microtubule targeting compounds 7a and 7e are of interest for further trials as antineoplastic agents.     

Polyalkoxybenzenes from plant raw materials 1. Isolation of polyalkoxybenzenes from CO2 extracts of Umbelliferae plant seeds

For the search for a domestic natural source of allylpolyalkoxybenzenes and development of an effective process for their isolation, CO₂ extracts of several varieties of parsley, dill, celery, caraway, and nutmeg were analyzed systematically for the first time by GC/MS and GLC techniques. The varieties with high contents of myristicin, elemicin, allyltetramethoxybenzene, apiol, and dillapiol were identified. The conditions of CO₂ extraction for obtaining concentrates with minimum contents of the distillation residues were selected. Using high performance fractional distillation, polyalkoxyallylbenzenes with 98–99% purity were isolated from the concentrates on a pilot unit. By isomerization of some allylbenzenes followed by ozonolysis under specially selected conditions, apiol-and dillapiolaldehydes were obtained in 75–80% yields. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2364–2371, December, 2007.     

Synthesis and reactions of 3-cyano-6-methoxymethyl-4-methyl-2(1H)-pyridinethione

Nucleophilic substitution of the chlorine atom in 2-chloro-3-cyano-6-methoxymethyl-4-methylpyridine by mercapto group produces the corresponding 2(1H)-pyridinethione, alkylation of which by halogenated compounds in the presence of KOH proceeds regioselectively to form S-alkyl derivatives. Thorpe—Ziegler cyclization of S-alkyl derivatives, which contain an active methylene group, yields new 3-aminothieno[2,3-b]-pyridines.Kuban State Technological University, Krasnodar 350072, Russia, and N. D. Zelinskii Institute of Organic Chemistry of the Russian Academy of Sciences, Moscow 117913; e-mail: stud@issep.rssi.ru. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 3, pp. 337–341, March, 1999.