Synthesis and properties of (4-hydroxy-5-methoxycarbonylthieno)-tetrathiafulvalenes

6-Hydroxy-5-methoxycarbonylthieno[2,3-d]-1,3-dithiol-2-thione, -2-one, and 2-selenone were prepared by intramolecular cyclocondensation of 4-methoxycarbonylmethylthio-1,3-dithiol-2-thione-, 2-one-, and 2-selenone-5-carboxylic acid methyl ester. 2,6(7)-Di(methoxycarbonylmethylthio)-3,7(6)-di(methoxycarbonyl)tetra-thiafulvalene, 2-methoxycarbonylmethylthio-3-methoxycarbonyl-6,7-ethylenedithiotetrathiafulvalene, and the corresponding thieno-condensed tetrafulvalene derivatives were synthesized from them. The electrochemical oxidation potentials of the new tetrafulvalene derivatives were determined.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 761–768, June, 1993.     

Characterisation of humic substances by acid catalysed transesterification

The chemical composition of low molecular weight moieties linked to the core structures of humic substances (HS) are of substantial importance for the understanding of the chemical structures and mode of interactions of HS with other substances in the environment. In this study a novel approach to characterise certain low molecular weight compounds bound to HS is suggested. The method includes transesterification (TE) of ester and amide bound structures, and esterification (E) of free carboxylic groups using acid catalysed methanolysis followed by gas chromatography (GC)-mass spectrometry (MS) and GC-FID analysis. Methanolysis of five HS of different origin, demonstrated the presence of multifunctional hydroxy-substituted benzoic acids, hexoses, and long chain fatty acids. Based on GC-FID and addition of the internal standard before methanolysis, the total amounts of low molecular weight material could be estimated. In case of HS from the aqueous sources the yields were below 1%, whereas in case of the HS derived from lignite the yield was significantly higher. The hydrophobic long chain fatty acids constituted about one-third of this material. Principal component analysis (PCA), which was used for extended data evaluation, differentiated between the samples in terms of chemical composition.     

Synthesis of 5-dialkylaminothiocarbonylthiobarbituric acids and 5-diethyiaminothiocarbonylthio-6-aminouracil

The title compounds are obtained by three different methods. The aminothiocarbonylthiolation of barbituric acids 1 and aminouracil ( 5 ) can be accomplished in one step by reaction with thiuram disulfides in the presence of potassium carbonate. On the other hand, compounds 4 can be obtained via the salt of chloro derivative 2 or the corresponding iodonium ylides 3 . The aminouracil derivative 7 was obtained in a similar fashion from 5 directly or via iodonium betaine 6 .     

Preparation of two stereoisomers of the macrocyclic electron donor tetramethoxycarbonyl[5.5]-tetrathiafulvalenophane with bridges containing two sulfur atoms

Isomers of a macrocycle containing two tetrathiafulvalene structural units joined by propylenedithio bridges are prepared. The electrochemical oxidation potentials are determined. Possible conformations of tetramethoxycarbonyl[5.5] tetrathiafulvalenophane are analyzed using the AM1 method.Riga Technical University, Riga LV-1048, Latvia. Department of Chemistry, Ben Gurion University of Negev, 84105 Israel. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 910–913, July, 1999.