Tetrachlorosilane-Sodium Azide System in the Synthesis of Tetrazole-Containing Amino Acid Derivatives

Treatment of N-acetyl-(RS)-phenylalanine and N-acetyl-(RS)-leucine methyl esters with the system tetrachlorosilane-sodium azide leads to formation of tetrazole-containing amino acid derivatives. The latter can be converted into -substituted 5-methyl-1-tetrazolylacetic acids and the corresponding bis-tetrazoles.     

Synthesis and Acidity of 5-Phenyltetrazol-2-ylalkanoic Acids and the Corresponding 5-(5-Phenyltetrazol-2-ylalkyl)tetrazoles

We have obtained 5-phenyltetrazol-2-ylalkanoic acids and their derivatives containing terminal nitrile, amide, and tetrazol-5-yl groups. Tetrazolylalkanoic acids with two (pK _a 4.93) and three (pK _a 5.45) bridging methylene groups are weaker acids than the corresponding ditetrazoles pK _a 4.68 and 5.29 respectively). However, the acidity of 5-phenyltetrazol-2-ylacetic acid (pK _a 3.12), is higher than acidity of the corresponding ditetrazole (pK _a 3.27).     

Linear polynuclear tetrazole-containing compounds

Linear polynuclear tetrazole-containing compounds were synthesized. Alkylation of 5-[-(5-phenyl-2-tetrazolyl)alkyl]tetrazoles with ethyl bromoacetate and chloroacetamide gave the corresponding esters and amides. Treatment of the latter with tetrachlorosilane-sodium azide afforded compounds containing three tetrazole rings linked through polymethylene bridges. Acid ionization constants of the products possessing an NH-tetrazole ring (pK _a = 2.9–3.2) and the corresponding carboxylic acids (pK _a = 2.9–3.1) in aqueous methanol were determined by potentiometric titration.Translated from Zhurnal Organicheskoi Khimii, Vol. 40, No. 10, 2004, pp. 1580–1586.Original Russian Text Copyright © 2004 by Morozova, Komissarov, Esikov, Zubarev, Malin, Ostrovskii.     

Effect of Preliminary Treatment on Microstructure,Mechanical Properties and Fracture of Ni3Al Samples Synthesized by Spark Plasma Sintering

Russian Physics Journal - A comparative study of microstructure parameters and mechanical property characteristics of consolidated Ni3Al samples formed by spark plasma sintering after a preliminary...     

Fractionation of Oxygen and Hydrogen Isotopes at the Hydrate Gas forming in the Sea Sediments

The paper gives data on isotope composition of interstitial and near-bottom waters sampled in a region of gas-hydrate formation in the Sea of Okhotsk. The studies shows that heavy isotope of oxygen and hydrogen is used in gas-hydrate formation, with the result that isotope composition of its constitution water constitutes δ¹⁸O = +1.99‰, δD = +23‰ relatively to SMOW. Formation of autogenic carbonates leads to isotope exchange with interstitial water wich, in turn, changes its primary isotope composition in the direction of increasing of O-18 content. The near-bottom waters are isotope-light relatively to the SMOW standard and to the mean isotope composition of interstitial water in the studied region of gas-hydrate spreading.     

Tetrachlorosilane–Sodium Azide System in the Synthesis of Tetrazole-Containing D,L-Tryptophane Derivatives

Russian Journal of Organic Chemistry -     

1-Substituted 5-Alkyl(aryl)sulfanyltetrazoles and Their Derivatives

The review analyzes published data on the synthesis, chemical properties, and application of 1-substituted 5-alkyl(aryl)sulfanyltetrazoles. Specific attention is given to reactions of metalated 1-alkyl(aryl)-5-alkylsulfonyltetrazoles with electrophilic reagents as a general and highly stereoselective method for the preparation of functionally substituted olefins.     

Detector of thermal radiation based on high-temperature superconductor matrix with magnetooptical image-visualization system

We propose a concept for constructing a thermal imaging system of a new type that is based on unique magnetic properties of high-temperature superconductors and on a noncontact magnetooptic information reading from a matrix sensing element.